MXPA98010529A - Resistive element and calibrated air duct for spirome - Google Patents

Abstract

The present invention relates to an air duct, preferably a calibrated air duct includes a resistive element disposed in a hollow space of the tubular portion. This resistive element is adapted to provide a linear resistance-to-pressure response and is configured and adapted to cause a difference in pressure, or differential pressure, as the air circulates through the hollow space in this element. The preferred calibrated air duct has a pressure response, is useful in a spirometer and includes a tubular member. The calibration information is associated with the air duct and relates to the pressure response of the air duct of an exemplary response to pressure of an exemplary air duct having substantially the same dimensions and configuration as the duct of air.

Description

RESISTIVE ELEMENT AND CALIBRATED AIR DUCT FOR SPIROMETER BACKGROUND OF THE INVENTION The present invention relates to resistive elements and air ducts for use with spirometers, and to the spirometers that use such resistive elements and air ducts. More particularly, the present invention relates to resistive elements and air passages that are disposable and preferably at least partially biodegradable, to spirometers, preferably to differential pressure spirometers, which employ such elements and conduits, and to calibration techniques to ensure a high level of accuracy when disposable air ducts are used with spirometers. Spirometers are the devices used to measure the speed of circulation and volume of gas exhaled and inhaled by a user or patient, for example, a human being. Two general types of spirometers measure volume and flow, respectively. For the type of flow, the current port of the spirometer used to measure circulation is the pneumotachograph, with Fleisch being one of the types. These measurements are important for the physiological study and for the diagnostic analysis of the lung performance of the user of the spirometer. For example, the effects of various medicines used to treat patients with pulmonary or asthmatic problems can be analyzed by controlling the velocity of circulation and the volume of exhaled gas before and after the administration of a medication. Several devices are available in the market that are known as pneumotachographs, such as the Fleisch Pneumotachograph. These devices depend on a flow of laminar air passing through a resistance element. The other spirometers use more sophisticated electronics so that laminar flow is not necessary. Measuring the difference in pressure or the difference in pressure of exhaled gas through an element that creates or causes the difference in pressure is the basis for differential pressure spirometers. In such differential pressure spirometers, it is important that the air duct (pneumotachograph) be accurately configured and located, for example, relative to the pressure and electronic recording systems of the spirometers so that the measurements can be carried out reliably. and reproducibly. Such pneumotachographs of precise configuration, instead of being disposable, are made of strong metals or plastics to be durable and effective after many uses without structural degradation. See, for example, US Patent 5,137,026 to Waterson et al., The disclosure of which is hereby incorporated by reference in its entirety. Because most spirometers involve driving exhaled gas directly from a user's respiratory system to the measuring instrument, a major complication in the use of such devices is contamination from one patient to another patient if the same spirometer is used. for both. Several practices have been suggested to overcome this contamination problem. A particularly popular practice is to use a disposable mouthpiece and / or bacteriological filter over the entrance of the spirometer. The patient using the spirometer only makes contact with the nozzle and / or the bacteriological filter and thus can, at least in theory, avoid contaminating the rest of the device. The disadvantages of this practice include the relative cost of such nozzles / filters, and the relative ineffectiveness of such systems. Another way to overcome this contamination problem is to sterilize, between patients, the portion or portions of the spirometer that come in contact with the user and / or exhaled air. The disadvantages of this approach include having to spend additional capital on the supply and sterilization equipment, having to control the operation and efficiency of the sterilization equipment, and having to buy relatively durable and expensive spirometers to withstand the sterilization procedures. A third alternative that has been suggested is the use of disposable spirometer components. See, for example, U.S. Patent No. 5,038,773 to Norlien et al.; U.S. Patent No. 5,305,762 to Acorn et al .; U.S. Patent No. 272,184 to Karpowicz; U.S. Patent No. 4,807,641 to Boehringer et al .; and U.S. Patent No. 4,905,709 to Bieganski et al. Such disposable preliminary spirometer components have generally been made of strong plastics or medical grade metals, so, although they are disposable, the cost of producing such components is relatively high. In addition, it is relatively difficult to remove waste from such disposable components, for example, because they are made of strong and durable materials. The economical manufacture of a relatively inexpensive spirometer component of biodegradable and / or low cost material, however, has been prohibitive so far because of, for example, the interests of quality control. The general specifications of the industry require high quality spirometer components but the quality of these components can decrease when making them biodegradable, for example, the placement of these components in the spirometer can present problems. The placement of the resistive element within each air duct can affect the performance of the total spirometer, for example. The resistive element is frequently placed in perpendicular or normal configuration relative to the inner wall of the air duct and, additionally, must be placed at exact predetermined distances from the two opposite ends of the air duct.

Frequently, the resistive elements of the prior art lack linear responses in the resistance-versus-velocity values of circulation. More particularly, resistive elements configured to exhibit good resistance to high velocities of circulation frequently do not function adequately at low circulation speeds and, on the other hand, resistive elements configured to function well at low circulation speeds frequently do not provide a resistance ideal at high speeds of circulation. Therefore, any possibility of manufacturing a relatively inexpensive spirometer, as an alternative to the non-biodegradable components of durable metal or plastic of the prior art, would appear to be flawed due to performance and manufacturing interests. These manufacturing interests include the inconsistencies between various disposable and biodegradable spirometry components that can be produced in the assembly line and, additionally, include subsequent performance variations between the spirometer components that result from these inconsistencies. Inconsistencies in these components can be increased when they are assembled together or placed in the spirometer. For example, a port of passage of an air duct can not be perfectly formed, and the subsequent placement of this port of passage in the spirometer can lead to irregularly low pressure registers due to the filtration of air around the pressure port. The even positioning of the resistive element within the air duct, as another example, could be inaccurate between various assemblies and, consequently, a problem of precision may also prevail among the existing non-biodegradable components of durable plastic or metal. Accordingly, it would be advantageous to provide a means to ensure the high performance and consistency quality between various spirometer components from the assembly line, without considering whether the spirometer components are metal, plastic or biodegradable. A typical resistive element for a spirometer includes a disc-shaped member with a large opening in the center thereof. Other resistive elements of the prior art have disc-shaped elements formed of a mesh material. Another prior art device includes a diamond-shaped window in a central portion of the disc-shaped member. The diamond-shaped window is secured to a portion of the disk-shaped element, and is adapted to open and close at various amplitudes or degrees, depending on the speed of air circulation. A resistive element of the prior art formed of a mesh is typically rendered inoperable or inaccurate by moisture and saliva in the exhalations of the patient, resulting in obstruction of the mesh. Resistive elements of the prior art comprising a diamond-shaped window have been somewhat effective at low air circulation speeds, but have not provided a fully effective resistance-against-pressure response at both high and low flow rates. It would be advantageous to provide the spirometers with spirometer components that demonstrate linear characteristics and that can be economically, conveniently and effectively produced and used.

COMPENDIUM OF THE INVENTION New resistive elements and air ducts have been discovered, preferably calibrated air ducts, for use in spirometers, and spirometers that include such resistive elements and air ducts. The resistive elements and air ducts of the present invention are disposable so that, after being used by a patient, they are removed and eliminated. The resistive elements and air ducts are almost completely biodegradable, can be manufactured relatively economically, and are capable of demonstrating characteristics of high performance and consistency. As used in the present, the term "biodegradable" refers to the component or material that is decomposable forming more acceptable components for the environment, such as carbon dioxide, water, methane and the like, by natural biological processes, such as microbial action, by example, when exposed to typical landfill or embankment conditions, in no more than five years, preferably less than three years, and even more preferably in less than one year. Using resistive elements and biodegradable air ducts provides considerable advantages. First, when disposing of these resistive elements and air ducts, the charge on the environment of such removal is reduced compared with, for example, the elimination of a conventional non-biodegradable air duct made of metal or plastic. In addition, because they are biodegradable, the resistive elements and air ducts can be made of cheap and abundant materials (easily available). Therefore, the present resistive elements and air ducts are relatively inexpensive, easy and easy to process. The subsequent calibration of the air ducts corrects any discrepancy in the size, shape and performance of the air ducts. Since the present resistive air elements and ducts can be manufactured economically, replacing a used air duct with a new air duct can be done without great economic impact. In addition, the present resistive elements and air ducts are very easy to replace in the spirometer. These advantages promote operator compliance where the spirometer operator (for example, the care provider or the patient operating the spirometer) is more likely to change the present resistive elements and air passages after each patient or treatment, reducing thus the risks of contamination and the spread of diseases, for example, tuberculosis and other diseases of the respiratory system, AIDS, and other systemic and similar conditions. The spirometers that use the air ducts of the present, preferably calibrated air ducts, provide affordable, reliable and reproducible pulmonary performance measurements (between one air duct and another), with a reduced risk of contamination. In short, the present disposable and biodegradable resistive elements and air ducts, preferably the calibrated air ducts, are inexpensive and easy to produce to acceptably accurate specifications (for reproducible performance), their use is efficient and reliable, and are convenient and effectively removable in an acceptable or safe manner for the environment, reducing the risks of contamination caused by the use of the spirometer. In a broad aspect, the current invention concerns air ducts for use in spirometers. The air ducts of the present invention comprise a tubular portion defining an open inlet, an open outlet, preferably opposite the inlet, and a hollow space in between. The tubular portion is shaped and adapted to be removably coupled to the housing of a spirometer. The air duct is disposable, that is, it can be removed or decoupled from the spirometer housing and discarded without having to remove the housing. Substantially, the entire tubular portion is preferably biodegradable. The open entrance is configured and adapted to be received in the mouth of the user of the spirometer. Therefore, this open entrance and the area of the tubular portion near the open entrance act as a nozzle for the spirometer so that the user or the patient using the spirometer can exhale directly into the air passage through the open entrance. No specially configured (and relatively expensive) filter separator and / or nozzle is needed with the use of the present air ducts. The air ducts of the present invention include a resistive element which is located in the hollow space of the tubular portion. This resistive element is configured to cause a difference in. the pressure, or differential, as the air circulates in the hollow space of this element, and is adapted to provide a non-linear flow-versus-pressure response. This response is subsequently linearized using computer programs. The resistive element includes a flat portion having a first face and a second face, and a parameter connecting the first face to the second face. An opening is formed in the center of the flat portion to connect the first face to the second face. A plurality of grooves in the flat portion extend radially of the opening, thus forming a plurality of hinged windows in the flat portion. Each slot includes a central end and a distant end. The resistive element also includes a plurality of hinge grooves.

Each hinge slot is connected to the distal end of a slot, and extends generally perpendicular relative to the axis of the slot. The total amount of the hinge slots corresponds to the total number of slots. According to one aspect of the present invention, the grooves and hinge grooves form hinged windows in the shape of an arrowhead. Each hinged window includes a point, pointing towards the center of the flat member, and a neck, which controls the flexibility of the window. A large neck reduces the flexibility of the hinged window, and a small neck increases the flexibility of the hinged window. The resistive element has an approximately linear pressure response over a range of flow rates, from zero liters per second to 15 liters per second. According to another aspect of the present invention, an air duct is formed of a first duct, a second duct, and a neck duct. The first conduit has a near end, a distal end, and a first diameter. The second conduit, similarly, has a near end, a distal end, and a second diameter that is approximately equal to the first diameter. A resistive element contacts the near end of the first conduit first and the distal end of the second conduit, and has a third diameter that is approximately equal to the first diameter. A neck conduit engages both the proximal end of the first conduit and the distal end of the second conduit.

The neck conduit has an inner diameter that is approximately equal to the first diameter, and has an outer diameter that is larger than the first diameter first. There is a pass port formed in the second conduit. The port of passage opens directly into the hollow space defined by the pipe assembly and is at a distance from the resistive element. The port of passage provides communication between the hollow space of the tubular assembly and a pressure sensor assembly of the spirometer. The pressure sensor assembly of the spirometer compares the pressure in the hollow space with the atmospheric pressure. The tubular portions and resistive elements of the air conduits of the present invention preferably comprise biodegradable materials, and are more preferably 99% biodegradable. Preferred biodegradable building materials include paperboard, paper, biodegradable polymeric materials and the like, and mixtures thereof. In a particularly useful embodiment, the tubular portion is made of paperboard or paper or mixtures thereof, more preferably produced by analog methods to those traditionally used to produce the tubes that form the core of toilet paper rolls. Such production methods often include the formation of a paper or cardboard tube on a mandrel or similar implement, then cutting the resulting tube to the desired length. If the tubular portion is made of biodegradable polymeric materials, such tubes can be formed using conventional polymer molding techniques. The resistive element is placed in relation to the tubular portion so that the difference in pressure for any given velocity of air circulation through the resistive element is equal to the duct in the conduit. The resistive element is preferably located transverse to the longitudinal axis of the tubular portion. The resistive element can be put into the tubular portion by adhering (eg, using biodegradable adhesives) the resistive element to the inner wall of the tubular portion or by joining two separate segments of the tubular portion with the resistive element placed between them. Other methods or techniques for the placement of the resistive elements in the tubular portions can be employed. Preferably, the resistive elements of the air ducts of the present invention designed for use in the same spirometer are structured and configured in essentially the same way, so that no recalibration or adjustment to the spirometer is necessary when replacing one air duct with another. In a preferred embodiment, the air ducts of the present invention also comprise means, or a sub-system, of positioning adapted to cooperate with the housing of the spirometer to properly orient the air duct relative to the housing of the spirometer. Any suitable positioning means can be employed to properly orient the air duct relative to the housing of the spirometer, for example, so that the port of passage of the air duct is properly aligned with the assembly of the pressure sensor of the spirometer. In a specific embodiment, the positioning means include a notch configured and adapted to cooperate with a projection on the housing of the spirometer. In another specific embodiment, the positioning means includes a port of orientation in the tubular portion configured and adapted to cooperate with a projection located in the housing of the spirometer. This is a particularly useful embodiment, because the orientation port can easily be placed in the tubular portion of the air duct. Also, since the housing of the spirometer is frequently a component made of molded polymer, the orientation projection can easily be formed in the housing of the spirometer. An air duct according to the present invention can be adjusted without gapping in the open cavity defined by a housing of a spirometer so that the port of passage of the tubular portion is properly aligned with the pressure sensor assembly of the spirometer . To ensure proper alignment, the projections of the housing can be placed in the notch of the tubular portion such that the port of passage of the tubular portion is properly aligned with the pressure sensor assembly of the spirometer. A suction cup interface of the pressure sensor assembly fits without gapping around the port of passage. The clearance of the fit between the air duct and the housing of the spirometer housing ensures that the air duct can be used in conjunction with the spirometer without disturbing the alignment of the pass-through port / pressure sensor assembly. After use, the air duct can be removed from the conduit of the spirometer housing with relative ease to replace it with a new air duct. The air ducts of the present may be designed and structured to be used with an existing spirometer modified retroactively or with a spirometer specifically constructed for use with air ducts. It is particularly useful to have the tubular portion longer than the housing of the spirometer so that in use the tubular portion extends beyond at least one of the ends of the housing component of the spirometer to which the tubular portion is removably coupled. This aspect is very attractive in the prevention of excessive pollution of the housing of the spirometer by the user. Thus, the air that is exhaled by the patient passes through the tubular portion without making important or intimate contact with the housing of the spirometer. In another broad aspect of the present invention, new spirometers are provided. The spirometers of the present invention comprise a housing, an air duct as described herein, a pressure sensor assembly positioned in relation to the passage port of the air duct to detect the pressure at the port of passage, and an assembly electronic coupled to the pressure sensor assembly to generate signals, preferably electrical signals, indicating the differential between the pressure detected at the port of passage and the atmospheric pressure. The electronic assembly can be placed in the housing or it can be located in a remote position of the housing. For example, the housing can be a type of portable component connected, for example, by a filament, cable, or an RF path, to an electronic processing system that includes a considerable portion of the electronic assembly of the spirometer of the present invention. Alternatively, the electronic assembly can be completely arranged in the housing of the spirometer to provide a totally autonomous unit. Although many aspects of the current invention are described separately, more than one or all of the aspects may be used in various combinations, provided the aspects are not mutually inconsistent, and all combinations fall within the scope of the present invention. These and other aspects and advantages of the current invention. they are disclosed in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings, in which similar parts bear like reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side view of a spirometer according to the present invention showing a portion of the electronics disposed apart from the portable unit. Figure 1A is a front side view of the spirometer shown in Figure 1. Figure 2 is an enlarged view of the air duct of the current invention; Figure 3 is a cross-sectional view of the air duct of the current invention; Figure 4 is a planar top view of the resistive element of the current invention; Figure 5 is a front top view, partially in section and in perspective, of the air duct used in the spirometer shown in Figure 3.

Figure 6 is a somewhat schematic illustration showing a spirometer according to the current invention. Figure 6A is a cross-sectional view taken generally along line 6A-6A of Figure 6. Figure 7 is a cross-sectional view taken generally along line 7-7 of Figure 1. Figure 8 is a side view of an alternative embodiment of a spirometer according to the present invention. Figure 9 is a rear side view of the spirometer shown in Figure 8. Figure 10 is a perspective view illustrating the spirometer bar code reader assembly of the currently preferred embodiment; Figure 11 is a circuit diagram illustrating a specific implementation of the bar code reader assembly of Figure 10; Figure 12 is a schematic representation of a linear array of photodiodes for light reception of a bar code label according to the currently preferred embodiment; and Figure 13 is a perspective view of a set of autofocus lenses used to focus light on a linear array of photodiodes, according to the currently preferred embodiment. Figures 14 and 15 illustrate perspective views of a spirometer designed in accordance with the currently preferred embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS With reference to Figures 1 and 1 A, a spirometer according to the present invention, generally shown as 10, includes a biodegradable and disposable air duct 12, a housing 14 and electronic control 16. The spirometer 10 is what is usually known as a pressure differential spirometer and, in general, operates in a manner similar to the spirometer disclosed in the above-mentioned US Patent No. 5,137,026. The air duct 12 is described with reference to Figures 2 and 3. The air duct 12 includes a first tubular segment 18, a second tubular segment 20, and a neck duct 21. A resistive element 22 is placed between the first tubular segment 18 and second tubular segment 20. Air duct 12 and resistive element 22 are preferably about ninety-nine percent biodegradable. The tubular segments 18, 20, and 21 are manufactured from biodegradable paperboard or heavy paper, for example, in a manner similar to the manufacture of conventional cardboard tubes, such as those used as cores for toilet paper rolls and similar products. . These segments 18, 20, and 21 are preferably coated with a glossy layer. The resistive element 22 preferably comprises biodegradable material having good memory characteristics. According to the present embodiment, the resistive element 22 comprises a Nomex material. The material of the resistive element 22 can, alternatively, comprise any material such as nylon or other moisture resistant material. In the present embodiment, the resistive element 22 has a thickness of approximately .07620 mm, but other thicknesses can be used according to design parameters. The resistive element 22 is first secured to either the first tubular segment 18 or the second tubular segment 20, and then the other tubular segment 18 or 20 is then secured to the resistive element 22. Preferably, a biodegradable adhesive is used. In the present embodiment, the outer diameter of the first tubular segment 18 is equal to the outer diameter of the second tubular segment 20, and the outer diameter of the resistive element 22 is equal to the outer diameter of the first tubular segment 18. An inside diameter of the neck conduit 21 is approximately equal to the outer diameter of the first tubular segment 18. The neck conduit 21 is adapted to fit over both the first tubular segment 18 and the second tubular segment 20. Although it is preferable to use adhesives to secure the resistive element 22 between the first tubular segment 18 and the second tubular segment 20, the loose and frictional fit of the neck conduit 21 on the first tubular segment 18 and the second tubular segment 20 may be sufficient, in itself, to secure the resistive element 22 between the first tubular segment 18 and the second tubular segment 20. The distal end 23 of the neck conduit 21 is flush with the end d 25 of the first tubular segment 18 when the neck conduit 21 is suitably secured on both tubular segments 18 and 20.

Additionally, a notch 27, preferably comprising a punctured semicircle at the distal end 23 of the neck conduit 21, is preferably aligned with the port 24 of the second tubular segment. The port 24 of the second tubular segment 20 preferably comprises a punched circle in the second tubular segment 20. The notch 27 and / or the port 24 can be formed in the neck conduit 21 and / or the second tubular segment 20 either before or after assembling the three pieces 18,, and 21. After assembly of the three elements 18, 20, and 21, the port 24 opens directly into the hollow space (Figure 3) of the air duct 12. Figure 3 illustrates the air duct 12 in an armed state. Although a three-piece configuration of the air duct 12 is currently preferred, these three pieces 18, 20, and 21 can be replaced by a single duct, for example, and / or the resistive element 22 can be secured to an annular piece ( not shown), which is inserted into the single conduit. Figure 4 illustrates a planar top view of the resistive element 22, according to the currently preferred embodiment. The resistive element 22 comprises a central opening 32 and a plurality of slots 34 extending radially from the central opening 32. Each pair of adjacent slots 34 forms a hinged window 36, which in the presently preferred embodiment forms an arrowhead. Each hinged window in the shape of an arrowhead 36 comprises a point located near the central opening 32 and a neck 38 located at a distance from the central opening 32. According to the present embodiment, the resistive element 22 comprises eight hinged windows 36, but is You can use more or less hinged windows 36 according to the design parameters. The width of each neck 38 controls the flexibility of the corresponding hinged window 36. A larger neck yields the corresponding hinged window 36 less flexible, and a smaller neck 38 renders the hinged window co-compact 36 more flexible. A human patient exhaling at one end of the air duct 12 generates an air flow through the resistive element 22 which typically can comprise an air circulation velocity of between zero and 16 liters per second.

The resistance provided by the resistive element 22 should, ideally, be approximately linear between these various air flow rates. Resistive elements of the prior art, comprising a disc with a single opening therein, for example, do not have linear pressure relationships against circulation speed. A disc-shaped resistive element of the prior art having a good resistance of less than 1.5 centimeters of water per liter per second at approximately 12 liters per second, for example, will not have good resistance at lower speeds of circulation. More particularly, such conventional resistive disk-shaped element would have a very low resistance at low circulation speeds, which is unacceptable. The resistive element 22 of the current invention uses unique hinged windows 36 having collars 38, which can be designed to adapt the resistance of the resistive element 22 to various circulation speeds. The resistive element 22 of the present invention is adapted to provide an ideal resistance of less than 1.5 centimeters of water per liter per second at a circulation speed of approximately 12 liters per second but, in contrast to. a conventional resistive disk element, the resistive element 22 of the present invention also provides good resistance at low speeds of circulation. Generally speaking, the resistive element 22 provides a very good response of approximately linear flow rate against resistance at flow rates between zero and 16 liters per second. At high circulation speeds, hinged windows 36 open wide to provide good strength that is not too high. At low circulation speeds, the hinged windows 36 open very little, to provide a good resistance that is not too low. According to the currently preferred embodiment, an angle between two of the slots 34 is about 45 degrees, and each slot 34 has a width of about .0508 cm. A preferred width of each of the perpendicular hinged portions 37, which are used to control the width of a neck 38, it is approximately .1 cm. The diameter of the resistive element 22 is preferably 2.8 cm., with a tolerance of plus or minus .00127 cm., and the width between a line 39 that bisects one of the hinged windows 36, and another line 41 that passes through a slot 34, is approximately .159 cm., with a tolerance of more or less .00127 cm. An important aspect of the resistive element 22 of the present invention is the resistance provided at low circulation speeds, since, typically, patients are unable to generate a high velocity of circulation. The same resistive element also works well at high speeds of circulation. The resistive element 22 provides good resistance to a variety of circulation speeds, regardless of whether the patient is exhaling or inhaling. With reference to Figure 5, the air duct 12 includes an open inlet 46 and an open outlet 48. The area surrounding the open inlet 46 is configured and adapted to be inserted into the mouth of a human being. This area of the nozzle is used by the patient using the spirometer 10 (Figure 1) by placing the area 46 in the mouth and exhaling in the hollow space 30 of the air duct 12. Returning to Figure 1, when it is desired to use the air duct 12 is unpacked and coupled to the housing 14. In particular, the air duct 12 is coupled to the housing duct 51. The housing duct 51 includes a tab 52, adapted to be inserted into the notch 27 (Figure 2) of the air duct 12. Prior to placing the air duct 12 in the housing duct 51, the notch 27 is aligned with the port 24 (Figure 2) and, according to this embodiment, is manually aligned by the user just before insertion into the duct. housing 51. When the notch 27 is aligned with the port 24, the port 24 will be aligned with the portion of the pressure sensor 76, as shown in Figure 6. More particularly, an adjustment of the portion of the pressure sensor 76, comprising, preferably, a suction-shaped piece 77 that fits around the port 24 to provide a tight fit. The suction cup piece 77 preferably comprises silicone or vinyl rubber, and is adapted to provide a fit around the port 24, in order to attenuate any air filtration in this interface. Accordingly, the patient's breath is not introduced into the pressure sensor portion 76, preventing contamination of the pressure sensing area 76. After inserting the notch 27 of the air duct 12 into the housing duct 51 and, more particularly, placing it on the alignment tab 52, the distal end 23 of the neck conduit 21 should be flush with the distal end of the housing conduit 51. At this point, the spirometer 10 is ready for use. Note that the air duct 12 is longer than the housing duct 51 and, when properly coupled to the housing duct, extends beyond one of the ends of the housing duct. The relatively long air duct 12 reduces the risk of contamination of the housing, preventing effective contact thereof with the exhaled air of the user of the spirometer. Figure 6 illustrates the general operation of a spirometer, generally shown by the number 10. The following is a general description of the operation of the spirometer after placing the air duct 12 adequately relative to the area of the pressure sensor 76. The apparatus and the calibration method of the current invention will be discussed in more detail below, after the present general operational description. This general description is applicable to the use of any spirometer, such as the spirometer 10, according to the present invention. Through port 24 (Figure 2) communicates with pressure sensor 76. As an additional protection against contamination, pressure sensor 76 can be equipped with a filter, although this is not required. The pressure sensor 76 communicates with a differential pressure transducer or "calibrator" 80, which may be, for example, a transducer sold by Motorola under the trademark MPX 2020D. The pressure transducer 80 generates an electrical signal in a pair of output cables 82 and 84, which is proportional to the differential pressure between the sensor 76 and the atmospheric pressure. This signal is amplified by a differential amplifier stage 86 and directed to an analog-to-digital converter 88 that converts the output signal of the amplifier into digital signals. The output of the converter 88 is directed to a microprocessor 90, which is part of the control electronics 16. The microprocessor 90 uses the calibration data supplied by the encoded information in the air duct 12 in combination with an algorithm stored in a ROM 92 to carry out various calculations on the output signal of the converter 88, and to display the calibrated final results, e.g. eg, the volume and flow rate, on the screen 94, for example, a conventional monitor or liquid crystal module. The microprocessor 90 is energized by a power source 91, for example, either a battery or a connector capable of being coupled or connected to a conventional power line voltage source. The switch 96 can be activated to start the operation of the spirometer by the microprocessor 90. The results of each measurement can be stored in a RAM 98 for later reference. An output port 100 may also be provided to allow the programming of the microprocessor 90 to be changed. In addition, the microprocessor 90 may be programmed to transmit, through the input / output port and at the desired time, the accumulated results in the RAM 98. to a printer or a computer. U.S. Patent No. 5,137,026 to Waterson et al. Provides additional details with respect to the operation of a conventional spirometer. When a patient has completed a diagnostic treatment or exercise using the spirometer 10, the biodegradable air duct 12 is removed from the housing duct and discarded in a manner safe for the environment. As shown in Figures 1 and 1 A, the housing 14 is structured to be held in the user's hand. For example, the housing shaft 102 is configured to be easily held in the hand. In addition, notches 104 are provided for fingers 104 to further facilitate the use of this portable device. The embodiment shown in Figures 1 and ÍA includes the control electronics 16 located within the housing of the handle 14. Communication with printers or external computers can be carried out by the cable 106 that can be connected to the converter using a connector 105, such as the conventional RJ-11 conventional fast connection connector, in the housing 14. According to this preferred embodiment, the communication can also be carried out by means of a conventional infrared data association link (IRDA), and operable between the housing 14 and the printer or the external computer. The electronics in the housing 14 is preferably activated by a battery, such as a conventional rechargeable nickel-cadmium battery. If said battery is used, the housing 14 includes a port through which the battery can be charged. In the embodiment shown in Figures 1 and IA, the microprocessor 90 may be a dedicated microprocessor including a reduced keyboard with structured transparent shield and specifically adapted to control the operation of a spirometer. Alternatively, the microprocessor 90 may be a general purpose personal computer, including a full-sized keyboard, video monitor, printer and hard disk drive. The dedicated microprocessor is particularly advantageous for its relative simplicity, low cost and ease of use. In addition, the housing shaft 102 includes a tapered portion 107, as shown in Figure 1A, which facilitates placement and support of the housing on a flat surface, eg, between uses. The embodiment shown in Figures 1 and AIA is useful as a completely new spirometer, or air conduit 12 and housing 14 can be used to retroactively adapt an existing spirometer. For example, an existing spirometer includes a handheld unit that includes a permanent air conductor, a pressure sensor, a pressure transducer, an amplifier and an analog-to-digital converter, and it is connected to the dedicated control system, which operates in a manner substantially similar to the control electronics 16. The simple replacement of the portable unit by the housing 14 and the components coupled to or disposed in the housing, produces a retroactively adapted spirometer having many of the advantages of the current invention. Figure 7 shows a cross-sectional view of the spirometer 10 of Figure 1, taken along line 7-7 of Figure 1. Another embodiment is shown in Figures 8 and 9. This spirometer, shown generally with the number 210, is, except where specifically mentioned herein, structured in a manner similar to the spirometer 10. The spirometer components 210 corresponding to the spirometer components 10 have reference numbers corresponding to the original reference numbers increased by 200. The primary differences between the spirometer 210 and the spirometer 10 have to do with the air duct configuration 212 and the configuration of the housing duct 251. The air duct 212 is structured substantially similar to the air duct 12 except that in the region near the open outlet 248, two orientation ports 107 and 108 are provided. The accommodation conduit 251 is structured to act as a cradle for the air duct 212 instead of wrapping the air duct 212 as is the case with the duct 51. In addition, the duct 251 includes two upwardly extending projections 109 and 110 which are located to be received in orientation ports 107 and 108, respectively, when the air duct 212 is coupled to the housing duct 251. The projections 109 and 110 being coupled to or received by, the orientation ports 107 and 108, the port 224 ( not shown) is suitably aligned with pressure sensor 276 (not shown). As shown in Figures 8 and 9, a reduced keyboard with transparent shield 112 of the microprocessor 90 is located on the axis 302 of the housing 214. In addition, this embodiment preferably comprises more ROM, and is display device 94 is located on the housing 214 below the reduced keyboard with transparent shield 112. In the spirometer 210, the power source 91 is a battery, such as a conventional rechargeable nickel-cadmium battery, and is located within the housing 214. Port 114 in the housing 214 is adapted to provide communication between the battery 91 and a conventional battery charger for recharging the battery when necessary. The input / output port 100 is also located in the housing 214 and provides convenient communication between the microprocessor 90 and a computer or printer, when it is desired that information from the electronic circuitry Ill be transmitted to another device. As with the embodiment of Figure 1, an optical IRDA port is also disposed on the axis 302. The spirometer 210 is a self-contained unit that can be operated by a single patient. To operate the spirometer 210, the air duct212 is coupled to the housing duct 251 so that the projections 109 and 110 align with the orientation ports 107 and 108, respectively. The patient then activates a switch on the reduced keyboard with transparent shield 112 and uses the spirometer 210 for any treatment and / or desired diagnostic procedure. When it is desired to remove the air duct 212 from the housing duct 251, the biodegradable air duct 212 is simply removed from the housing duct 212 to be disposed of in an environmentally acceptable manner. Referring again to Figure 6, a character recognition unit 304 is disposed within the housing 14 of the spirometer 10. The character recognition unit 304 comprises, preferably, a device for recognizing bar code type stripes. The character recognition unit 304 is arranged within the housing 14 to align with a sequence of characters 306, preferably bar code type stripes, on the air duct 12, when the air duct 12 is placed inside the housing 14. According to the current invention, there is encoded in the sequence of characters 306, calibration information related to the air duct 12.

This coded information is read by the character recognition unit 304 and transmitted to the converter 88 via line 308 and then to the microprocessor 90. The converter 88 preferably comprises eight inputs. Of these eight, two receive signals from the pressure transducer 80, one receives the flow pressure in the conduit, and one registers the rhinomanometric pressure (the nasal air pressure). According to the current mode, the character recognition unit 304 is arranged within the housing 14 of the spirometer 10 to automatically read the sequence of characters 306, but, alternatively, this information reading of the character sequence 306 can be carried out manually. Human-readable characters can be arranged next to the sequence of characters 306, for example. Additionally, the information reading of the character sequence 306 may be carried out before, during, or after each reading by the spirometer 10, according to the design preferences. The character recognition unit 304 is preferably an optical character recognition unit, adapted to read a sequence of bar code characters 306 but, alternatively, other information transmission techniques can be implemented. For example, magnetic character recognition, optical recognition of alphanumeric characters, recognition of optical symbols, etc. they can be used, provided that the calibration information related to the air duct 12 is transmitted to the microprocessor 90. Preferably, the character recognition unit 304 comprises a linear array for the recognition of bar code type codes. Figure 6A shows a cross-sectional view along the line 6A of Figure 6. According to the current mode, a light source 310 projects illumination in the direction of the arrow Al on a sequence of characters 306 disposed on a surface of the air duct 12. In this embodiment, the character sequence 306 comprises a bar code label or, alternatively, a bar code printed directly on the air duct 12. The light from the light source 310 is reflected from the sequence of characters 306 in the direction of arrow A2 and enters a set of autofocus lenses 313.

The light from the autofocus lens assembly 313 is subsequently focused on a linear array of photodiodes 315. The linear array of photodiodes generates an electrical output, which is interpreted consecutively by the converter 88 and then by the microprocessor 90 (Figure 6). ) to discern the calibration information contained in the character sequence 306. According to the currently preferred embodiment, a wedge-shaped black plastic fastener 318 is disposed between the light source 310, and the autofocus lens assembly 313, and the linear array of photodiodes 315. The black plastic fastener 318 is adapted to secure the three elements 310, 313, and 315 therein so that they are properly aligned within the housing 14 of the spirometer 10. Fig. 10 shows a view in perspective of the character recognition unit 304 of the currently preferred mode. Light from the illumination source 310 is focused on the sequence of characters 306 disposed on the air duct 12. The reflective light is received by the autofocus lens assembly 313, which, according to the present embodiment, is disposed at an angle 321 of about 45 degrees of the illumination source 310. Both the illumination source 310 and the autofocus lens assembly 313 have lengths that are substantially parallel to a scan centerline 323 that passes the character sequence 306. The assembly linear photodiode 315 is arranged substantially parallel to the autofocus lens set 313, and is adapted to receive the focused light from the autofocus lens assembly 313. An external light stop 325 is disposed over a portion of the autofocus lens assembly 313, and another external light stop 327 is disposed over the assembly 315 photodiode linear array. FIG. 13 illustrates the external clip-on light stop 325 adapted to accommodate the autofocus lens assembly 313, according to the currently preferred embodiment. The external light stop 325 preferably comprises black plastic, and can be adapted to be frictionally secured around the autofocus lens assembly 313 and / or secured thereto using an adhesive. Alternatively, less expensive external light stop techniques may be implemented, depending on the design preference. As mentioned above with reference to Figure 6A, both the light source 310 and the autofocus lens assembly 313 and, more preferably, also the linear array of photodiodes 315, are disposed on a wedge-shaped black plastic fastener 318 The wedge-shaped black plastic fastener 318 provides the correct angle between the light source 310, and the autofocus lens assembly 313 and the linear photodiode assembly 315. The black wedge-shaped plastic fastener 318 also facilitates the proper arrangement of the light source 310, the autofocus lens assembly 313, and the linear array of photodiodes 315 with each other and the air duct 12. The black plastic wedge-shaped fastener preferably comprises a black color to suppress light reflections. The total focal length 333 of the autofocus lens assembly 313 is preferably approximately 9.4 millimeters, measured from an internal sensitive surface of the linear array of photodiodes 315 to the target surface of the character sequence 306. According to the embodiment Current, the set of lenses' autofocus 313 comprises a Selfoc® lens assembly, manufactured by Nippon Sheet Glass Co., Ltd. The autofocus lens assembly 313 is located at the midpoint between the linear array of photodiodes 315 and the character sequence 306 so that both the linear array of photodiodes 315 as the character sequence 306 are at focal points of the autofocus lens array 313. According to the current mode, the autofocus lens array 313 is located 2.5 millimeters from the 306 character sequence and 2.5 millimeters of the linear array of photodiodes 315. A portion of approximately 1 millimeter width of the character sequence image 306 along the center line of character sequence 323 is transferred by the autofocus lens array 313 to the linear array of photodiodes 315 when the character sequence 306 is illuminated by the light source 310. According to the current mode, the conjunct or autofocus lens 313 has a length of about 18 to 20 millimeters, and comprises a single row of lenses 336. The autofocus lens assembly 313 is preferably slightly longer than the linear array of photodiodes 315, which is approximately 16 millimeters long, to ensure that the entire linear array of photodiodes 315 receives the image, considering an allowable deviation of plus or minus 1 millimeter in the alignment and / or cause of final lens damage in the lens array autofocus 313. The two focal points of an exemplary single lens 336 of the autofocus lens set 313, which are not to scale, are shown with numbers 339 and 340. The linear array of photodiodes 315 preferably comprises an intelligent optical sensor manufactured by Texas Instruments, model number TSL215, and comprising a set of 128 mode-charged pixels in a linear array of 128 x 1. The linear array of photodiodes 315 is preferred over charge coupled device (CCD) due to its ease of use, among other reasons. The linear array of photodiodes 315 comprises integrated clock generators, analog output buffers, and test and hold circuitry that would otherwise be required by a CCD circuit. The focal point 340, for example, is focused at approximately 1 millimeter below the upper surface of the linear array of photodiodes 315. According to the current mode, in addition to the external light stop 327, a cover of the sensitive surface 346 is disposed on the sensitive surface 346. transparent plastic 344, shown in Figure 32. The central scanning line 323 projects on the sensitive surface 346, as shown by the line 348. According to the current mode, the focal point 340 (Figure 10) is approximately 1 millimeter below the upper surface of the transparent cover 344, and projects on the sensitive surface 346 of the assembly. The light is projected onto the sensitive surface 346 of the linear array of photodiodes 315 when the illumination source 310 is activated by the microprocessor 90 (Figure 6). As shown in Figure 11, the microprocessor 90 activates the light source 310 using the "light activation" signal line 350, connected to a pin of the parallel port 352 of the microprocessor 90. According to the current mode, the source of illumination 310 comprises a set of four light emitting diode elements of approximately 45 milicandelas (lumens / ster), having a wavelength of approximately 635 nanometers and being approximately a Lambertian source. The light source 310 is polarized with a current of 20 milliamperes in the two lamps in the middle and with 25 milliamps of current in the two end lamps, to provide an even illumination along the character sequence 306, according to the invention current. The light source 310 provides approximately 23 microwatts per square centimeter of illumination, and is located approximately 7 millimeters from the bar code, as shown by reference numeral 354. The external light stop 325 between the illumination source 310 and the autofocus lens assembly 313 it suppresses the vagabond light. The current invention incorporates a wavelength of 635 nanometers to approximately match the maximum sensory responsiveness of the linear array of photodiodes 315 that is approximately 750 nanometers. The sensitivity obtained in the linear array of photodiodes 315 is approximately 80% of the maximum of 100% sensitivity of the linear array at a wavelength of 750 nanometers. The light source 310 has a length of approximately 16 millimeters. According to the current mode, only the light source 310 is activated by means of the microprocessor 90 during the reading of the bar code, because, as is obvious, the activation of the light source 310 dissipates energy. Both the light source 310 and the linear array of photodiodes 315 preferably comprise integrated circuits that are mounted on a flexible personal computer plate, forming a dihedral angle 321 among themselves of 45%. With reference to Figure 11, the image integration time of the photodiode array 315 begins with a short pulse through line 360 of the microprocessor 90 at an input serial plug 362 of the photodiode array 315. After approximately 1 to 10 milliseconds, a second input serial pulse is sent to the linear array of photodiodes 315 via line 360. After this second input serial pulse, the image is read into the video output pin 364, timing the clock pin 366 to between 10 kilohrtz and 100 kilohrtz, using 129 or more clock pulses. The resulting signal is transmitted through the serial video output line 368. During said chronometry operation, the video serial output, which comprises an analog voltage, is read by the analog-to-digital (A / D) converter. 370, which preferably comprises a precision of 12 bits and an input range of 0 to 5 volts. The analog-to-digital converter 370 transmits the digital output data on a data bus 373, which reflects the amplitude of each video pulse and, consequently, the darkness of each pixel sensor in the linear array of photodiodes 315. These The digital data on the data bus 373 is then read by the microprocessor 90. The analog-to-digital converter 370 is controlled by the microprocessor 90, and has a conversion time of approximately 10 microseconds. Accordingly, the linear array of photodiodes 315 can be clocked up to 10 microseconds (100 kilohours). The linear photodiode array 315 is activated by a 3-terminal voltage regulator 375 to keep noise from the power supply and the video assembly at a minimum. Although the TSL215 product from Texas Instruments is currently preferred, a newer product can also be used.

Texas Instruments, the TSL1402. This new model comprises twice the number of pixels in the same length of 16 millimeters. The model has twice the resolution and allows the display of more digits with greater reliability. This new model has compatible plugs, allowing to change, simply, the number of clock cycles from 129 to 257, and is less susceptible to optical saturation.

Additionally, the TSL1402 does not require the initial charge period of 40 milliseconds, and provides twice the speed and accuracy. The sequence of characters 306 preferably comprises a bar code having either an ITF sequence interspersed 2 in 5, providing calibration data of approximately 3 decimal digits in addition to a check-sum digit or, alternatively, it can comprise a right binary code. The right binary bar code is currently preferred, and is configured to provide approximately five and a half digits, plus a binary check sum of about six bits. The binary code will be NRZ (not return-to-zero) with bars and spaces of constant width, plus a start mark. This configuration ensures that the total width of the code is constant and allows a margin of error in the placement of 1 millimeter on each side of the code. The minimum widths of the white and black bars in the bar code are selected to be at least 2 to 3 pixels wide in the linear array of photodiodes 315. Given that the linear set of photodiodes has a spacing of .125 millimeters between the photodiodes, the minimum width of bapa is approximately twice said width. This configuration ensures that at least one pixel position in the video output 368 of the linear array of photodiodes 315 reaches the limit below or above, since a pixel in array 315 is entirely black or white, and not located in a position between a black bapa and a white area. The totally high or low voltage, in relation to other voltages in the video output 368 of the linear array of photodiodes 315, is decoded by the computer programs to positively indicate a bapa position. • - Since the light source 310 is preferably of constant intensity, the variations in the intensity of the light source between units and over time are compensated in the present invention. For this, and to compensate for the sensor efficiency, the light integration of the linear array of photodiodes 315 is adjusted. The reading level of the video image of the linear array of photodiodes 315 can be increased, increasing the time between the pulses input serials on line 360, that is, the time of the light integration interval. After reading each chip code, if the chip code amplitude data is too low, the integration time is increased until the amplitude is sufficient to detect black-white differences. The total amplitude of the serial video data stream in each reading operation forms a non-linear curve, due to changes in the light intensity along the illumination source. In computer programs, according to the current invention, a differential differential followed or other indicator is used to detect the approximate white-to-black threshold along the video data stream. This average is used to distinguish between white and black data by comparing them through computer programs. Computer programs filter out high frequency noise, and the resulting data stream comprises an image of the chip code. According to the current mode, this resulting data stream is decoded using the binary NRZ method or the 2-in-5 interleaving method, depending on the code in use. The NRZ format alters the color of the chip code if the data bits do not change, and does not alter the color of the barcode when the bits change. The resulting stream, after being decoded by either the binary NRZ method or the integrated 2 in 5 method, comprises the original binary or decimal number that was originally coded in the air duct 12. This number is then used to calibrate the sensor Spirometric circulation. The linear array of photodiodes 315 must initially be pre-conditioned by an operation period of 40 milliseconds, before reading each code of baps, to allow the 128 pixels to change copectamente from white to black, or vice versa. During this pre-conditioning period, the light source remains activated, and the bap code data is ignored. Subsequently, several scannings of the code of bapas are carried out until obtaining the data connectes, determined by the checksum programmed in the bap code. Consequently, the entire read operation takes approximately 40 milliseconds plus 5 milliseconds per scanned barcode code, or over 100 milliseconds. Each bar code review requires a minimum time of 128 times 10 microseconds, or a maximum time of 128 per 100 microseconds. The time is determined according to the necessary time of integration, as mentioned above. The illumination source 310 is continuously activated during all the scanning of the baffle code, up to 100 milliseconds, and does not turn off between individual scannings of 5 milliseconds, because the pixels need to be illuminated during the integration time. A 16-bit timer embedded in the microprocessor is programmed to unpair repeated periods of time from 10 to 100 milliseconds, each period generating a switch. A timer switch starts a routine that generates the start impulse of the integration, if necessary, and then generates 129 clock pulses, measured by the stopwatch. At each clock pulse, the analog-to-digital converter 370 is read by the microprocessor 90 via the data bus 373 and stored for further analysis. After the completion of the 129 clock pulses, the stopwatch is stopped and the data is analyzed by the microprocessor 90 to determine the mobile threshold level white to black of each pixel, by filtering and calculating continuously from the average. The data, then, is filtered through the computer programs and compared to the mobile threshold level., Before being converted into bap codes. In the currently preferred mode, approximately 8 barcode code scannings are made and stored at the same time, requiring a maximum time of 8 by 12.5 milliseconds, or 100 milliseconds, so that the initial loading time of 40 millisecond pixels does not have to be repeated. With respect to the autofocus lens assembly 313, this assembly may need adjustments to achieve exactly focusing on the character sequence 306 with an epor margin of plus or minus .3 millimeters, unless this is guaranteed by the manufacturing process . The focal length may need adjustment in a low light environment, while executing a microprocessor diagnostic program 90 which continuously scanns the sequence of characters 306, reporting the percentage of reading echos generated during reading of the 306 character sequence. Focal length is preferably adjusted until errors are minimized. Preferably, examples of the worst cases or random bap codes for this procedure would be used.

According to the method of calibrating an air duct 12 and placing the calibration information in the air duct 12 in the form of a sequence of characters 306, a large initial batch of air duct sampling 12 is tested. a manufacturing line. According to the present embodiment, the test procedure comprises subjecting each circulation conduit 12 to an air flow of 7.5 liters per second in the exhalation direction. A sensor, similar to that shown in Figure 6 by the number 76, is placed over the passage port 24 (Figure 2) of the air duct 12, and this sensor is connected to a high precision pressure sensor. A mechanical resonance filter may be required in the conduit. For each conduit, the measured pressure with respect to the air flow of 7.5 liters per second in the exhalation direction is recorded, and, consecutively, a similar pressure is obtained measured for the same velocity of air circulation in the direction of inhalation for each air duct 12. The present invention recognizes that, although there are manufacturing differences between the air ducts 12, the pressure output curve against the air flow inlet for each air duct 12 is remarkably similar. More particularly, the pressure versus air flow performance curve for each circulation conduit 12 can be mathematically modeled by a third-order polynomial with fixed coefficients. The polynomial for each air duct 12 varies by only one gain factor. Thus, according to the currently preferred mode; the response of any air duct in reference can be calibrated to duplicate an exemplary or ideal response by simply multiplying the response of the air duct by a constant. Since the pressure versus air flow performance curve for each air duct 12 varies only by one constant, the measured pressure of an air duct 12 can be compensated to achieve an ideal pressure performance for any given air flow rate between 0 and 16 liters per second. Although the present invention is described in a particular embodiment where the calibration of each air duct can be carried out by simply generating a single calibration constant for each direction of air circulation (inhalation and exhalation), the present invention is not limited to this exemplary modality. According to the presently preferred embodiment, after obtaining the pressure measurements for the circulation of air in the inhalation and exhalation direction in a reference air duct 12, these two pressure measurements are compared with two copespondents measured for example pressure. Exemplary pressure measurements are obtained by taking the average of pressure measurements of an initial large batch of air duct sampling 12 from the manufacturing line in accordance with the current preferred embodiment. The gain factor is determined, based on the pressure measurement in the reference air duct 12 and the exemplary pressure measurements. For example, if the exemplary pressure measurement in the inhalation direction is slightly higher than the pressure measurement in the physical duct in the inhalation direction, a counting factor is generated to increase the pressure measurement of the physical duct 12 to the exemplary measurement of Pressure. This counting factor comprises a constant in the currently preferred mode. A reference table can be used having a number of measurements of the physical conduit 12 and co-spectroscopy co-factors, as a simple example. According to the current modality, such a reference table can comprise a large number of measurements of the physical conduit according to the desired precision, and the corresponding corrective factors. The copection factors, according to the present, calibrate each physical conduit, to the desired level of precision. Additionally, according to the currently preferred embodiment, a single binary number is used to represent both factors of copección for any physical air duct 12. Because the physical air duct 12 is tested for a pressure measured in both directions, the inhalation and the exhalation,, two different factors of copection are generated copespondiendo the two measured values of pressure in the physical air duct 12. The unique binary number is, in the present, the preferred to represent these two factors of compression in compressed form, and these can also be taken from a reference table. Figures 14 and 15 illustrate perspective views of a spirometer design according to the currently preferred embodiment. The air duct -212 is substantially covered by the housing, and the display device 94 and the reduced keyboard with transparent cover 112 are larger than in the embodiments described above.While this invention has been described with respect to various specific examples and embodiments, it will be understood that the invention is not limited thereto and that it may be varied in practice within the scope of the following claims:

Claims (37)

1. - A spirometer adapted to support an air duct, characterized in that the spirometer comprises: a frame adapted to removably hold an air duct having a pressure response and calibration information related to the pressure response of the air duct; a pressure sensor assembly adapted to record the pressure in the air duct supported by the frame and to provide pressure data based at least in part on the pressure in the air duct; a character recognition unit adapted for reading the calibration information; and circuitry adapted to process the calibration information read by the character recognition unit, the circuitry being adapted to use the registered calibration information to cope with the pressure response of the air duct attached by the frame to a pressure response of a exemplary air duct having substantially the same configuration and dimensions as the air duct supported by the frame.

2. The spirometer according to claim 1, characterized in that the character recognition unit comprises a bar code reader.

3. An air duct having a response under pressure and being adapted for use in a spirometer, characterized in that the air tube comprises: a tubular element; and calibration information relative to the pressure response of the air duct to an exemplary pressure response of an exemplary air duct having substantially the same dimensions and configuration as the air duct.

4. The air duct according to claim 3, characterized in that the calibration information comprises a bar code format.

5. The air duct according to claim 3, characterized in that the air duct is arranged, and the calibration information is arranged, in the tubular element.

6. The air duct according to claim 3, characterized in that the calibration information is adapted to facilitate the generation of a pressure response copegida air duct, taking into account the pressure response copegida the exemplary response under pressure of the exemplary air duct.

7. The air duct according to claim 3, characterized in that the calibration information is readable by machine.

8. A spirometer, characterized in that it comprises: a frame adapted to removably hold an air duct having both a pressure port and calibration information; a pressure sensor assembly adapted to record the pressure at the pressure port of the air duct supported by the frame and to provide pressure data based at least in part on the pressure at the pressure port; and circuitry adapted to use the calibration information of the air duct to adjust the pressure data to that which would have been generated by a pressure sensor assembly by recording the pressure of an exemplary air duct having substantially the same dimensions and configuration as the air duct supported by the frame.

9. An air duct having a pressure response for use in a spirometer, characterized in that the air duct comprises: a tubular element defining a hollow space; and tuning information adapted to facilitate adjustment of the pressure response of the air duct, based at least in part on an exemplary response to pressure from an exemplary air duct having substantially the same dimensions and configuration as the air duct.

10. The air duct according to claim 9, characterized in that the air duct is disposable and the calibration information is arranged in the tubular element.

11. The air duct according to claim 9, characterized in that the calibration information serves to provide a copeded response to pressure of the air duct, taking into account the response copeded under pressure the exemplary pressure response of an exemplary air duct .

12. A resistive element for use in a spirometer, characterized in that it comprises: an element having a first substantially flat face and a second, substantially flat second face; a plurality of pitch slots in the element, each of the plurality of pitch slots having a length and having an inner end and an outer opposite end; and a plurality of hinge grooves, each hinge groove being located in and extending at the outer end of one of the passage grooves and having a length oriented in a generally different direction relative to the length of a passage groove, forming the plurality of pitch slots and the plurality of hinge grooves a plurality of windows hinged in the element.

13. - The resistive element for use in a spirometer according to claim 12, characterized in that the plurality of passage grooves and the plurality of hinge grooves form at least four windows hinged in the element.

14. The resistive element for use in a spirometer according to claim 12, characterized in that the number of hinge slots is the same as the number of slots.

15. The resistive element for use in a spirometer according to claim 12, characterized in that each hinged window is in the shape of an arrowhead having a tip and a generally opposite neck, located between two of the passage slots, the neck having a dimension between the two hinge grooves smaller than a similar dimension of the window hinged at a distance from the two hinge grooves.

16. The resistive element for use in a spirometer according to claim 6, characterized in that each hinged window is flexible and the dimension of each neck controls the flexibility of the hinged window copespondiente.

17. The resistive element for use in a spirometer according to claim 15, characterized in that the resistive element has a linear response at approximate pressure over a range of air flow velocities of up to about fifteen liters per second to plus or minus room temperature.

18. A three-piece assembly for use in a spirometer, characterized in that it comprises: a first conduit having a near end and a distal end, the first conduit having a first outer diameter; a second conduit having a near end and a distal end, the second conduit having a second outer diameter that is approximately equal to the first outer diameter; a resistive element located in proximity to the near end of the first conduit and to the distal end of the second conduit; and a neck conduit having a third outer diameter larger than the first and second outer diameters, the neck conduit being coupled to both the first and second conduits and located on the near end of the first conduit and the distal end of the second conduit.

19. The assembly of three pieces for use in a spirometer, according to claim 18, characterized in that it also comprises a port formed in the second tube.

20. The assembly of three pieces for use in a spirometer, according to claim 19, characterized in that it also comprises a notch formed in the neck conduit.

21. The assembly of three parts for use in a spirometer, according to claim 20, characterized in that the port is adapted to accommodate a pressure sensor element of the spirometer, and wherein the notch is adapted to accommodate an alignment tab of the spirometer

22. The assembly of three pieces for use in a spirometer, according to claim 20, characterized in that the notch is aligned with the port.

23. A resistive element for use in a spirometer, characterized in that it comprises: a thin and elastic disc-shaped membrane; a plurality of passage grooves in the membrane forming at least in part a plurality of windows hinged and spaced in the membrane; and the resistive element having an approximately linear pressure response over a range of air flow velocities of up to about 15 liters per second at an approximate ambient pressure.

24. The resistive element for use in a spirometer according to claim 23, characterized in that the plurality of passage grooves provide a first predetermined resistance at low velocities of air flow through the resistive element, and the plurality of hinged and spaced windows provides a second predetermined resistance at high air flow rates through the resistive element.

25. The resistive element for use in a spirometer according to claim 24, characterized in that the resistive element provides a resistance of less than approximately 1.5 centimeters of water per liter per second at an air flow rate of 12 liters per second under pressure. approximate of the environment.

26. The resistive element for use in a spirometer according to claim 23, characterized in that the resistance provided by the resistive element at an air flow rate of 3 liters per second at an approximate ambient pressure is substantially greater than the resistance of a resistive element of similar size comprising only one disc and a large opening .

27. The resistive element for use in a spirometer according to claim 23, characterized in that the plurality of hinged and spaced windows is adapted to open slightly at low flow velocities and to open more substantially at high flow velocities.

28. The resistive element for use in a spirometer according to claim 23, characterized in that the plurality of passage grooves form, at least in one part, at least four windows hinged and spaced in the member.

29. A method for calibrating an air duct for use in a spirometer, characterized in that the method comprises the following steps: (a.) Applying a predetermined air flow rate to the air duct; (b.) measuring a physical pressure for the air duct at the predetermined air flow rate; and (c.) determining a physical gain for the air duct based on both the physical measured pressure and the exemplary pressure used as a reference pressure.

30.- The method to calibrate an air duct according to the claim 29, characterized in that it also comprises the following steps: (d.) Placing the air duct in a spirometer; (e.) read the gain for the air duct; (f.) generate a pressure measurement of the patient using the air duct; and (g.) Apply the gain to the patient's pressure measurement in order to produce a pressure measurement connected to the patient.

31.- The method to calibrate an air duct according to the claim 30, characterized in that it also comprises: applying a predetermined air flow rate to a plurality of air calibration ducts; measuring the predetermined air flow rate for each of the air calibration ducts at the predetermined air flow rate; and determine the exemplary pressure based on the measured calibration pressures.

32. The method for calibrating an air duct according to claim 30, characterized in that it also comprises placing physical gain in the air duct.

33. A method for calibrating an air duct for use in a spirometer, characterized in that the method comprises the following steps: (a.) Measuring a predetermined and unhindered air flow velocity in an inhalation direction in a plurality of calibration ducts. of air; (b) measuring an inhalation calibration pressure for each of a plurality of air calibration conduits at a predetermined and inhalation air flow rate; (c.) taking the average of the inhalation calibration pressures from the air calibration lines to produce an exemplary inhalation pressure; (d.) applying a predetermined and exhalation air flow velocity in an exhalation direction to the plurality of air calibration conduits; (e) measuring an exhalation calibration pressure for each of a plurality of air calibration ducts at predetermined and exhalator air flow rates; (f.) take the average of the exhalation calibration pressures of all the air calibration tubes, in order to produce an exemplary exhalation pressure; (g.) measuring an inhalation physical pressure of the physical airway, based on both the measured physical inhalation pressure and the exemplary inhalation pressure; (h.) assigning a physical inhalation gain to the physical airway, based on both the subject inhalation pressure and the exemplary inhalation pressure; (i.) measuring an exhalation physical pressure of the physical air duct at a predetermined exhalation air flow velocity; j.) assign a physical exhalation gain to the physical airway, based on both the subject exhalation pressure and the exemplary exhalation pressure; (k.) place both the physical inhalation gain and the physical exhalation gain in the physical airway.

34.- The method for calibrating an air duct according to claim 33, characterized in that the physical inhalation gain and the physical exhalation gain are placed in the physical air duct in the form of a code, which represents in a compressed form both the gain exhalatory physics as the physical inhalation gain.

35.- A method for calibrating a physical air duct for use in a spirometer, characterized in that the method comprises the following steps: providing a reference curve of pressure against flow, copespondiendo the reference curve of pressure against flow to a response to pressure of an exemplary air duct at different flow rates; measuring the pressure performance in the physical air duct at a predetermined air flow velocity, in order to establish a measure curve against flow; compare the pressure versus flow reference curve with a measured pressure versus flow curve; and generate a correction, which, when applied to the measured curve of pressure against flow, will produce the reference curve of pressure against flow.

36. - The method for calibrating a physical air duct according to claim 35, characterized in that it also comprises the following steps: placing the physical air duct in a spirometer, having access to the copección; generate a current curve of pressure against flow in response to a patient inhaling in the air duct; apply the copection to the current pressure versus flow curve to produce a pressure curve against airflow that would have been generated if the exemplary air duct had been used in place of the physical air duct to generate the current pressure curve against flow, facilitating the application of the copección to the current curve of pressure against air flow obtaining a precise response in relation to the exemplary air duct, of the physical air duct. 37.- An apparatus for the manufacture of calibrated air ducts, characterized in that it comprises: a pressure port adapted to be placed on a port of an air duct; an air flow generator for directing an air flow, having a predetermined flow rate, through the air duct; a pressure sensor connected to the pressure port adapted to measure a pressure inside the air duct in response to air flow; a comparator assembly adapted to provide a gain for the air duct based on the measured pressure and the reference pressure; and in application assembly adapted to apply the gain to the air duct. RESISTIVE ELEMENT AND CALIBRATED AIR DUCT FOR SPIROMETER SUMMARY OF THE INVENTION The present air duct, preferably a calibrated air duct, includes a resistive element disposed in a hollow space of the tubular portion. This resistive element is adapted to provide a linear resistance-versus-pressure response and is configured and adapted to cause a difference in pressure, or differential pressure, as the air flows through the hollow space in this element. The preferred calibrated air duct has a pressure response, is useful in a spirometer and includes a tubular member. The calibration information is associated with the air duct and relates to the pressure response of the air duct of an exemplary pressure response of an exemplary air duct having substantially the same dimensions and configuration as the air duct.