DE1466843A1 - Plethysmograph - Google Patents

Description

Pi-l-oritätt "performance show of the phartna 25 October 1965 zcutischen and medical-technical 55 ^ 6-65 / Dr.vB / E Industry on the occasion of the 71 · Congress of the German Society füp (Mediz in" front 25 ^. 65 ^

U66843

Erich Jaeger, Würzburg
X-ray ring 5

Plethysmograph .
Addition see patent ... (patent application J 27 1C2 IXd / ^ Oa)

The main patent relates to a plethysinograph for medical pulmonary examinations with a largely airtight closable cabin for receiving a person to be examined, a device that responds to pressure changes in the air contained inside the cabin, and a space which is arranged inside the cabin and is sealed against it an easily movable wall, the interior of which is connected via a breathing tube to a mouthpiece or a breathing mask into which the person to be examined breathes.

From a medical point of view, the fluctuations in the internal pressure of the cabin are of primary interest due to the fluctuations in volume that occur during breathing

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of those to be examined. Person caused. However, these pressure changes of interest are superimposed on relatively strong disturbances, the main cause of which is the heating of the cabin air by the examining person and other sources of heat, such as lighting fixtures or heat emitting devices.

In order to solve these difficulties, it has been proposed in the daupo patent on the one hand that the patent should be allowed to breathe in a space separated from the interior of the cabin by an easily movable compartment, inside of which there is a thermostatically controlled heating device and a ventilator . ¹ -; ' ¹ "Il: - device is located, and on the other hand, the inside of the egg Ks.vLno through a compensation opening, preferably variable .-, connect the cross-section with 'Ie? Umgeoungsluft r: u.

Gor ". ^ ;; one; other own '/ slain (Pae ^ ntoiinieldung J 27 991 I.Cd/JCa) the internal pressure cer L · ·' Lne. -Light on Jen" J: r ^ εcungsdrucl-: oezoron, probe /. 'n on d- ^ r ;. Di-uc !: inside a closed buffer tank in order to avoid disturbances caused by pressure fluctuations in the outside air, which for example duror. : 3as opening and closing of doors: occur iccnnea.

lX: ^ 'i ^ \ the present ^.' rfindunj the eoer: mentioned at ^: uv: vcc \ en should be further reduced. This is done by the following warning men. achieved:

The easily movable V / and of the sealed

Space; ■;.!. rd formed as -.Tr me lock, by example; .eise zv / ei thin plastic hoses are arranged one inside the other,

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εο that a double, heat-insulating V.and is formed.

Instead of or in addition to the equalization opening, the cabin is provided with a pump that sucks air out of the cabin at such a rate that (3 the pressure increase caused by the heating öo :? indoor air is at least approximately compensated. The throughput of the pump is attached preferably controlled so that it decreases according to one or the sum of several exponential functions.

The increase in pressure inside the cabin is preferably first measured with the pump stopped to a measure of the. "Change" of the pumping rate to obtain. Characteristic is known the influence of various of the examined person • heat sources, which is empirically readily ascertainable results the value determined in this way is also a measure of the patient's basal metabolic rate.

Further features of the invention are protected in the subclaims.

The invention is illustrated below with the aid of exemplary embodiments explained in more detail in connection with the drawing; show it:

FIG. 1 is a side view of a plethysmograph with the cabin cut along a line 1-1 in FIG. 2;

2 shows a plan view of the cabin in a sectional plane 2-2 of FIG. 1 and a circuit arrangement for determining dos basal metabolic rate or for eliminating disruptive Warmer: Influences;

Fig. J is a partially sectioned, partially r :: ehornat ifjch shown side view of a preferred embodiment

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management form of a breathing head for the one shown in Figs Plethysmograph;

FIG. 4 is a plan view of that shown in FIG. 3 Breathing head, and

Fig. 5 is a diagram for explaining the operation the circuit shown in FIG.

The plethysmograph shown in the drawings as a preferred embodiment of the invention includes a cabin 10 for accommodating the person to be examined and a measuring and control frame 12.

The cabin 10 has a tightly closing door 14 with a window 16, its interior is through another Window 18 and a light source 20 arranged outside the cabin, preferably a fluorescent lamp that does not generate much heat illuminated. In the ceiling of the cabin there is also a relatively large opening 22 with a closure 24, the can be opened from the inside in an emergency.

In the interior of the cabin there is one shown in FIG. 3 breathing head 28 shown in more detail, which is mounted on a vertical rod 30 so that it can be adjusted in height and pivoted.

During the examination, the patient sits on a type of chair 32, the seat and back of which are perforated are. The underside of the seat surface and the rear of the backrest are in communication with the interior of the cabin 10. This measure avoids disturbances that would otherwise be caused by air pockets between the patient's body and the stool.

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To the internal volume of the cabin 10 as possible

To keep it small, the rear wall 3 ^ of the cabin has the shape of a Half-cylinder 'In addition, under the chair 32 there is one against the Located inside the cabin sealed box 36 ". The interior 38 of this box can be used as a buffer volume as will be explained in more detail below.

The pressure changes in the cabin 10 can be measured in several ways:

1. By means of a measuring device 40 which is connected between the interior of the cabin and the ambient air.

2. By means of a measuring device between the interior of the cabin and an opposite of the ambient air largely closed buffer volume is switched. As a buffer volume, for example, the interior 38 of the Box 36 serve. In this case there is then a measuring device 42 connected between the interior of the cabin and the interior 38 of the box 36. The buffer volume can also be outside the Cabin are located and is then connected to the terminal 44 of the measuring device 40 facing away from the cabin. The outer buffer volume may have a wall in common with the cabin 10 or be entirely separate from it.

The measuring devices 40, 42 can be sensitive differential pressure manometers or sensitive, direction-dependent ones Flow measuring devices with downstream integrating device 'be. ■

The inside of the cabin is with the outside air

also via a compensation opening, the cross-section of which is preferably is adjustable, connected, which in Fig. 2 as a valve

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46 is shown. A rotatable disc can be used for this can be used, which has openings of different diameters, optionally in one of the interior of the cabin with the duct connecting the outside air can be switched on and then determine its narrowest cross-section.

A similar compensation opening, which represents an adjustable flow resistance, can also be used according to Desired provided between the buffer tank and the outside air and / or between the buffer tank and the interior of the cabin be.

The product of the volume elasticity and the volume of the cabin 10 is preferably equal to the product of the volume elasticity and volume of the buffer tank, so that pressure fluctuations of the ambient air without influence on the between the interior of the buffer tank and the interior of the cabin are the prevailing pressure difference.

When the box 36 under the chair y2. is used as a buffer container, the chair is ys. preferably supported on the cabin wall or the cabin floor, but not on the box 36, so that disturbances caused by deformations of the box yS when the person to be examined moves are prevented. ~

The breath head 28 shown in more detail in FIGS. 3 and 4 comprises a breathing tube having a mouthpiece 48 ^ O (or a breathing mask nichtdargesteilten) into which the patient breathes. The breathing tube 43 contains a solenoid valve 52, which is used in a manner known per se to record closure pressure curves,

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a correspondingly designed, only schematically illustrated solenoid valve 54 which, when open, allows the person to be examined to breathe air from inside the cabin 10; a flow meter 56, which preferably contains a flow resistor 58 in the form of a heatable metal network and a differential pressure manometer 60 which is connected to pipe socket 62 on both sides of the flow resistor 58 and a pipe socket 64 which is arranged in front of the valve 52 and leads to a pressure gauge 66 which with the valve closed, _measure the occlusion pressure (alveolar pressure P alv). The closing of the valve 52 is preferably controlled by the differential pressure manometer 60 and preferably closes at the end of exhalation, since the occlusion pressure curve then recorded by the pressure measuring device 66 and the measuring device 12 of the plethysmograph allows the functional residual air to be determined. For this purpose, the differential pressure manometer 60 is connected to a control unit 68, c3as, as indicated sehematically in the rectangle marked 68, contains a relay with two fixed contacts x, y and a movable contact tongue ζ, the rest position of which is in the middle. If the differential pressure & P. According to the diagram shown in Fig. J5, the contact tongue ζ then alternately rests against the contacts x, y in accordance with the diagram below, and takes a short period of time in its rest position in which it does not make contact with any of the contacts. The control unit 68 thus has a threshold value. During the transition from exhalation to inhalation

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Atraung the 'control unit 68 closes the solenoid valve 52 for. a sufficient time to record a locking pressure curve, which in the measuring and control frame 12 together with the simultaneous pressure changes occurring in the cabin 10 can be indicated or recorded.

The upper end of the breathing tube 48 opens into a space 70 which is sealed off from the interior of the cabin and which is delimited at the bottom by a base plate 72. From the base plate "J'D jump up and down depending on a cylindrical Plansch 74, γβ before, which are each provided with an annular groove 78, the 80th to the upper flange J6 wire brackets 82 are attached, which carry above a tubular piece 84, which means can be sealed of a removable plug. on the base plate 72 are also v / urther wire bracket 88 attached, which are fastened at the top of a ring 90. the wire brackets 82, 88 are used to support hoses 92 and 94, made of thin plastic film, whose upper and lower ends are provided with elastic bands ^ 6 , which seal the ends of the hoses in the grooves 78 or 80 or corresponding grooves on the outside of the pipe section 84. The space 70 is therefore against the interior of the cabin 10 in which it is arranged is, hermetically sealed; however, because of the flexibility of the thin plastic films from which the hoses 92, 94 are made, no disruptive pressure difference can occur between the space 70 and the interior of the cabin 10 eten.

In the room 70 there is an air circulation and temperature control device 98. Through this device 98

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the air in the room 70 is kept at a temperature whose In practice, the value is just below the body temperature and is chosen so that neither of the examined Person in the room 70 cools exhaled air, nor the out the space 70 heated air inhaled. Sine such cooling or warming would interfere with the measurements. The through that Wire bracket 82, 88 ensured space between the Plastic film tubing 92, 94 provides excellent Thermal insulation is so that no interference by heat emission from the space 70 into the interior of the cabin can »One, such thermal insulation has proven itself in practice proved extremely important.

The device 98 contains a tubular housing 100 in which an electric fan 102 is arranged at the top is. The fan preferably conveys from top to bottom: the motor is preferably arranged at the top, the fan blade at the bottom. There is a thermostat-controlled one under the fan Heating device, the heat exchanger plates 104, e.g. made of copper, and one that is in good thermal contact with them Includes heat source. As a heat source, at least one power transistor ΙΟβ is preferably used, which is connected to the Sheet metal 104 is in a good thermally conductive connection. The transistor 6 forms part of a known temperature control device that is also close to the transistor arranged heat sensor IO8, which transmits the transmission, sistors prevented, and one a little further away from the transistor arranged heat sensor UO (Flg. 4) contains;

which is responsive to the temperature of the air flowing past the metal sheets 104. All rule keeping is preferable mounted on the metal sheets 104 and encapsulated with a silicone resin to protect against moisture.

The breathing tube 48 can also be provided with a heating arrangement 112., which is only shown schematically, and a electrical resistance heating can be provided.

To preheat the breathing head 28 and to: remove stale air, a heater fan Il4 operate like a hair dryer, then the Plug 86 removed and the assembly with the valve open 52 flushed with fresh, possibly warm air.

If in the course of an investigation a person placed in the cabin 10 and the door 14 of the cabin closed temperature and pressure in the cabin begin to rise. This is extremely disruptive for the measurements. The compensation opening 46 (FIG. 2) provides a certain remedy here, however, depends on a compromise: the time constant of the compensation must not be too short on the one hand, otherwise the pressure fluctuations to be measured will also be falsified v / earth, on the other hand the time constant should not be too large otherwise the temperature-related increase in pressure will not be sufficient is weakened. In order to avoid these difficulties, according to the invention a pump II6 (Fig. 2), e.g. a blower is provided which draws air from the interior at a controlled, decreasing rate the cabin 10 pumps out. The relationships are based on the in

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Fig. 5 illustrated diagram explains in which along the The abscissa is the time t and along the ordinate the temperature T of the air contained in the cabin or of that practically proportional pressure P are plotted.

If one closes the cabin in which there is a patient and switched-on devices, the pressure P and rise Temperature T "according to a curve 118, which is essentially consists of the sum of two exponential functions 120, 122. The curve 120 corresponds to the heat output of the one to be examined Person showing curve 122 of heat dissipation from devices switched on. According to the invention, the pump 116 is now controlled in such a way that that their delivery rate etvra decreases according to a curve 124 so, that the internal pressure of the cabin remains largely constant. The curve 124 is also the sum of two exponential functions 126, i'd8, which is the reciprocal of the e-functions 1'dO, 122 are.

Such a pump control can be achieved relatively easily. The drive of the pump Il6 is through a Regulator 130 regulated, in which the setpoint in the form of a voltage E is entered. It is assumed that a high voltage E results in a low delivery rate of the pump and vice versa correspond. The voltage E is generated by charging a capacitor I32 via two separate charging circuits. Everyone The charging circuit contains an adjustable series resistor Ij54 or 156 and an adjustable voltage source I38, I40. the The voltage source can be, for example, potentiometers, as shown, which are connected to a direct voltage LL

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H66843

are. The one charging circuit with the resistor 1J54 and the potentiometer 138 is used to compensate for the heating that is caused by switched-on devices and can therefore be set once when the device is manufactured. The other charging circuit 1J6, l40 must depend on the heat output set differently for the person to be examined.

The setting of the charging circuit 136, l40 can

take place on the basis of the following measurement: The cabin is closed and the increase in pressure in the cabin is measured, for example, by means of the measuring device 42. The charging circuit 136 is interrupted, for example by a switch 142, so that only the heating caused by the devices is compensated. _{The pressure increase / ^ P 0} shown in the diagram on the left in FIG. 2 is then exclusively due to the heat given off by the person examined. The pressure signal from the measuring device 42, which increases in accordance with curve 120 (FIG. 5), is converted into a linearly increasing signal U by a step 144 which generates the inverse function, the speed of which then represents a measure of the heat output of the person to be examined. The rate of rise can be recorded by a stage 146 or digitally displayed in a known manner; this display firstly represents a measure of the basal metabolic rate of the person examined and at the same time provides a basis for setting the charging circuit Ij56, l40. Instead of using the pump II6 su to compensate for the pressure increase caused by the devices in the manner mentioned, you can use the

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U66843

Let the pump rest also measure the basal metabolic rate and apply a linearly increasing voltage U from the voltage U in one Subtract level 148. The voltage U then becomes accordingly based on the power output of the devices. May be the power output of the devices is neglected at all and the arrangement shown in FIG. 2 is then simplified accordingly will"

It is particularly useful to control the delivery rate of the pump proportionally to the rate of increase in the temperature of the air in the cabin 10. This control is independent of the pressure fluctuations in the cabin that represent the useful signal. A signal representing the rate of temperature rise dT / dt can also be used to determine the basal metabolic rate in accordance with the above explanations. When controlling the pump, no special correction is necessary, the dT / dt signal can be used directly to control the speed of the pump drive. The air in the cabin is preferably circulated.

Claims (1)

Patont claims. / Iy Plethysmograph - for medical lung errant requests with a largely airtight closable cabin to accommodate a person to be examined, a device that reacts to changes in pressure inside the cabin contained air, and one inside the Kacine arranged, against this sealed space r;: it one easily movable wall, the inside of which is connected to an air tube Mouthpiece or a breathing mask is connected to the examining person breathes, characterized in that the easily manoeuvrable '/. " is trained. 2. Plethysmograph according to claim 1, characterized g e k e η η :: e i c h η e t that the easily movable l / and contains two spaced \ ^r oneinander arranged plastic films (92, 94). ^. Plethysmograph according to Claim 2, characterized in that the plastic films (92, Sk) are shaped like tubes, each supported by a wire frame (82, SS) and sealed at their ends by elastic bands (96). BATH S / 00 21 4. Plethysmograph in particular according to one of the preceding claims, with a measuring device which is based on the expansion of the cabin caused by heating contained air responds, characterized in that da3 the measuring device (42) is connected to a non-linear amplifier (144), "the one at least provides an approximately linearly increasing output signal (U) and verounden this with a registration or display device (146) is. 5. plethysmograph according to claim 4, characterized characterized in that the display device is one of the Speed of rise of the signal, proportional display supplies. 6. plethysmograph according to claim 5, characterized marked denies that the device is in basic metabolic units, e.g. kilocalories / hourj is calibrated, 7. Plethysmograph according to one of the ¹ preceding claims, characterized by an air pump (116) which sucks air from the interior of the cabin with controllably decreasing throughput. 8. Plethysmograph according to claim "J, characterized ge k e η η ζ ο I η et that the throughput of the pump 909826/0027 ^ ' such according to an exponential function or a sum of Exponential functions that the pressure increase caused by the heating of the air in the cabin at least decreases is approximately compensated. 9. Plethysmograph according to one of the preceding claims with one in the connection between the mouthpiece or the breathing mask and the sealed space arranged flow meter, a valve blocking the breathing tube for Closure pressure measurement and a closure pressure measuring device, characterized by a circuit arrangement (68) to control the closing of the valve as a function of from the signal generated by the flow meter (56). 10. Plethysmograph according to claim 9, characterized in that the valve (52) at the end the exhalation is closed and an occlusion pressure curve is recorded. 11. Plethysmograph according to claim 9 or 10, characterized in that the circuit arrangement contains a relay with two normally open contacts and a neutral rest position to control the closing of the valve. 909826/002 7 U66843 12. Plethysmograph according to one of the preceding claims, characterized by dadur-ch, that the device (40, 42) responsive to pressure changes in the cabin (10) contains a flow measuring device. 15. Plethysmograph according to claim 12, characterized in that the flow measuring device has at least one thermistor which is in an outlet opening (e.g. at 40, 42 or 46) of the cabin (10), and an arrangement responsive to the direction of flow, e.g. a mechanically agitated member, or a second, in the direction of flow against the first thermistor offset second thermistor and one on the relative temperature or resistance difference changes the two NTC thermistors appealing arrangement contains. 14. Plethysmograph according to claim 12 or IjJ, d adurch characterized in that the flow meter is followed by an integrator. 909826/0027