WO2009113899A1

WO2009113899A1 - Method and device for supplying a gas component during narcosis inhalation

Info

Publication number: WO2009113899A1
Application number: PCT/RU2008/000119
Authority: WO
Inventors: Игорь Викторович ИСАЕВ
Original assignee: МОРОЗОВ, Василий Юрьевич
Priority date: 2008-02-29
Filing date: 2008-02-29
Publication date: 2009-09-17

Abstract

The invention relates to medicine. The inventive method involves stabilising the value of a gas volume rate at the level of the largest amount of said component which is required for inhalating narcosis per time unit. The adjustment is carried out by means of a shutoff adjusting unit, the adjusting action of which reduces the gas component supply time at a constant volume velocity which is maintained at the level of the calculated value determined by the relation between the specified quantity and the peak value. In order to uniformly supply the gas component, the action is performed by algorithm dosing the supply time by pulses which have the same length and are uniformly spaced within a time unit. The total length is equal to the calculated value. A device for supplying a gas component during inhalation narcosis and an apparatus for supplying a gas component during narcosis inhalation which are used for carrying out said method are also disclosed.

Description

Method and device for supplying a gas component during inhalation anesthesia.

Application area.

The invention relates to medicine, and more specifically relates to a method for supplying gas components, such as oxygen, nitrous oxide, anesthetics, and apparatus for delivering inhaled anesthesia.

The prior art.

A known method for the automatic supply of gas components during anesthesia to a patient (US patent 6,830,047, MKI A61 M 16/00, 2004), in which using the model calculate the concentration of active gas components (anesthetics) in the patient’s body, compare them with previous information from data bank, calculate their difference and adjust the concentration by the difference obtained by feeding the component.

A known method and device for supplying an anesthetic (US patent 5,806,513, MKI A61M 16 / 01.1998) in which effective control is carried out by a computer that provides a signal to the regulating authority for the supply of gas flow. The closest is the known method of supplying gas flows during inhalation anesthesia, in which the regulation and measurement of the flow rate and quantity of the gas component are carried out. The flow rate and quantity of the gas component are controlled by a control valve installed at the inlet of the gas supply line by changing the flow area (RF N ° 2178314 Cl, 2002, MKI A 61 M 16/01, RF patent Ш 2 248 225C2, MKI A 61M 16/01, A. I. Trushin, V. M. Yurevich. Inhalation anesthesia apparatus. M. Medicine. 1989, p. 17). The closest technical solution is apparatus for delivering inhalation anesthesia (A. I. Trushin, V. M. Yurevich. Inhalation anesthesia apparatus. M. Medicine. 1989, p. 17), containing their own supply lines for each gas component of inhalation anesthesia, equipped with own regulating device in the form of a valve, and a measuring device, which is used as a rotameter or a group of rotameters. The lines are connected by exits to the collector for mixing the components necessary for inhalation and the formation of a further gas stream of an averaged composition, which enters the patient. The feed control is carried out by changing, on the assignment, the volumetric speed due to the action of the control valve on the passage area. The task is formed according to the readings of the rotameter.

Traditionally, dosing of medical gases in mechanical ventilation apparatuses and anesthesia machines is carried out using rotameters. The operational range of gas flows through each channel (oxygen, nitrous oxide, anesthetic anesthetic) used in medical practice reaches a hundredfold (from 0.1 l / min to 10 l / min), and sometimes exceeds it. The problem of achieving accuracy (reducing the error) of dosing is due to the fact that the level of concentration of anesthetic in the brain tissue must be adequate to the patient's condition during all phases of surgical intervention. This requires multiple regulation of the supply of gas (s) component (s) for inhalation anesthesia in a wide range of current (working) values during the operation.

At the same time, a separate rotameter has a small working range, usually not exceeding ten times. Therefore, there is a need, to ensure acceptable measurement accuracy of flows within the full operational range, to install several rotameters with overlapping ranges (to different measurement limits) in series.

The accuracy of the rotameter, as a rule, is measured from the upper limit of measurements. Therefore, with the accuracy class standard for such devices (error ± 4% of the upper measurement limit) for a rotameter with an upper measurement limit of 10 l / min, the error reaches 400 ml / min. Typically, at least two rotameters are installed in the gas line - one in the range from 1 to 10 l / min and the second in the measurement range from 0.2 to 2 l / min. Thus, when measuring the flow, for example, at 2.5 l / min (when the second rotameter has not yet been activated), the measurement error can reach 16% (0.4 l / min from 2.5 l / min).

The increasingly common tachometric flow meters, which allow digital readings, have approximately the same level of error, but additionally have the disadvantage that they are characterized by the so-called “stress tolerance”, i.e. some minimum flow level below which The sensor does not detect it. Beyond this “support” there is an additional “accelerated” section, in which the sensor is unstable. And only at flows exceeding these two sections of the characteristic, does the tachometric sensor begin to function normally.

The situation is not much better with the use of other flowmeters, for example, measuring the pressure drop across a constricting device (orifice) and converting this pressure drop to a gas or liquid flow. The fact is, the magnitude of the pressure drop depends not only on the flow rate of the working fluid (gas), its density and the area of the passage section of the constriction device, but also on the flow coefficient of this constriction device “m” (in other words, not all flows through the throttle its cross-section, but only a part, is of the order of 70%. This phenomenon is called “the suppression of strut”). Unfortunately, this flow coefficient even for the same narrowing device (for example, a throttle washer) also depends on the size of the measured flow and ranges from 0.65 to 0.75. This is primarily due to a change in the Reynolds number in the throttling section. Thus, the dependence of the flow coefficient on the flow of the working fluid, i.e. it is precisely from the value that is required to be measured that an additional error of the order of 7% makes.

With small amounts of anesthetic anesthetic delivered, especially approaching the lower supply limit, the absolute error becomes at least commensurate with the supply amount of the gas component, which essentially blocks the regulation process. Disclosure of the invention.

The basis of the invention is the creation of a method and device for supplying a gas component during inhalation anesthesia to the respiratory circuit, which would reduce the dosage error by controlling the time of the component supply at its stabilized volumetric speed (flow rate).

The problem is solved in that in the method of supplying the gas component during inhalation anesthesia, in which the gas component is supplied at a volumetric rate, the amount of the gas component supplied per unit time is regulated by a regulating body located in the supply line to ensure the amount set according to the patient’s condition, they stabilize the volumetric velocity at the level of the maximum amount of this component necessary for inhalation anesthesia per unit time, 15 regulation is carried out by a shut-off type walking body, the controlled action of which reduces the gas component supply time with a constant volumetric rate maintained to a calculated value determined by the ratio of the set quantity to the maximum value, and, in order to ensure an even gas component supply, the effect is carried out according to the algorithm, dosing the supply time by pulses equal duration and evenly distributed per unit time, while the total duration of the pulses is equal to the calculated value.

The problem is also solved by the fact that in the device for supplying a gas component during inhalation anesthesia to the respiratory circuit containing a regulating organ located in the gas component supply line, a shut-off regulating organ is used and an additional stabilization device is introduced volumetric velocity of the gas component at the maximum value set on the line along the stream, and a timer for generating a signal of controlled impulse exposure according to the algorithm for supplying the gas component with pulses of equal duration and uniformly distributed per unit time, with a step H of at least 0.25 sec., at this timer output is associated with the regulatory authority.

It is preferable to use a solenoid valve as the regulator of the shut-off type. It is advisable that the device for stabilizing the volumetric velocity of the gas component at the maximum value would be made in the form of a reducer and throttle calibrated to the maximum value, sequentially installed along the gas stream. The problem is solved in addition to the fact that the apparatus for delivering inhalation anesthesia, containing its own supply lines for each gas component of inhalation anesthesia, equipped with its own regulatory body, and connected to the outputs for mixing the components, each line has a regulating body of a locking type and additionally contains a device for stabilizing the volumetric velocity of the gas component at the maximum value, installed on the line along the flow, and at least one timer for of signals controlled by pulse impact on the algorithm supplying a gas component of the pulses of equal duration and uniformly distributed in a unit time, with increments of at least H 0,25cek., the timer output is connected with the regulator. It is advisable that an electromagnetic valve be used in the apparatus as the regulating body of the shut-off type.

It is also advisable that in the apparatus, the device for stabilizing the volumetric velocity of the gas component at the maximum value would be made in the form of a reducer and an inductor calibrated to the maximum value, sequentially installed along the gas flow.

The apparatus may include a pressure meter installed at the inlet of the gas component supply line.

A brief description of the drawings.

The invention is further explained in the description of examples of its implementation and the drawings, in which: FIG. Ia-Ic illustrate the implementation of the method of supplying a gas component according to the invention.

2a-2c illustrate an embodiment of a method for supplying a gas component according to the invention (continued). Fig. 3 depicts a schematic diagram of a control device according to the invention.

4 is a schematic diagram of an apparatus for delivering inhalation anesthesia, according to the invention.

The method of supplying the gas component according to the invention is as follows. The volumetric feed rate of the gas component is calibrated at the value of V _max (Fig. Ia), equal to the maximum amount W _{max of} this component, which is necessary for inhalation anesthesia in unit of time, for example a minute. Graphically, W _max represents the area bounded by V _max and unit time boundaries.

In case of inhalation anesthesia, the quantity W _{3 of the} gas component is set, which must be supplied per unit time based on the patient’s current state, and the value of the time T _p for delivering a given quantity W ₃ with a constant volume velocity Vmax is calculated. For the calculation, the ratio T _p = W _{3 is used} ./V _max (graphically, T _{p is} shown in FIG. Ia).

The gas component is supplied by acting by the regulating body of the shut-off type according to the algorithm, dosing the supply time with pulses of equal duration and uniformly distributed per unit time, to ensure uniformity in the supply of the gas component. In this case, the total pulse duration is equal to the calculated T _p .

To ensure equal pulse duration, the calculated time value T _{p is} divided by an integer “n” (Fig. 1 b). The conditions for choosing the value of "n" are as follows.

The volume of the respiratory circuit of the ventilator, including the blower or replacing its fur, a backup bag, the patient’s internal piping and breathing hoses, is approximately 3-4 liters. With an average inspiratory volume (for an adult patient) of 0.5 - 0.6 L and an average respiratory rate of 12 - 14 breaths / minute, the time of complete replacement of the respiratory mixture in the circuit (when working with “open contact”, i.e. when all the mixture used by the patient is discharged into the atmosphere), it is approximately 30 to 40 seconds. Therefore, in order for the patient to be given a respiratory mixture of constant composition, the number “n” (the number of gas supply cycles per minute) must be at least 2 (Ev = 0.5 12 / p). It is clear that the larger the number "n", the more stable the resulting mixture composition in the respiratory circuit. However, since the respiratory mixture in the respiratory circuit is intensively mixed, it is not practical to significantly increase the number of cycles (the number of device operations) per minute, because This will lead to a reduction in the life of the device.

Control measurements of the composition of the mixture in the circuit showed that even when working with “open contact”, good mixing of the mixture in it occurs even at a “n” value of 8–9 (ie, at 8–9 cycles per minute). An increase in the number of cycles per minute (the number “n”) to 12 led to the complete stabilization of the composition of the mixture in the entire possible range of inspiratory volumes.

As the transition to increasingly low-flow anesthesia occurs, when part of the patient’s breathing mixture is cleared of carbon dioxide and returned to the respiratory circuit, the number “n” can be reduced. So, when working with the oxygen / xenon mixture along a completely “closed” breathing circuit, in order to save expensive xenon, the entire breathing mixture exhaled by the patient, purified from carbon dioxide, is returned to the breathing circuit, the number is “n” was brought to a value of 0.5 (one trip in two minutes). In this case, fluctuations in the composition of the mixture could not even be detected with optical sensors, and the volume of xenon supplied to the circuit was brought to 0.005 l / min. Thus, the number "n" is selected based on the volume of the respiratory mixture in the device and the patient's consumption of a constant composition of the respiratory mixture. The obtained value of T _pP; equal to T _pn = T _p / n, corresponds to the duration of the feed pulse of the gas component. Impulses are evenly distributed per unit time minute. With a uniform distribution, the pulses are sampled per unit time, for example, as shown in FIG. Ic.

During the pulse, the shut-off element passes the gas component with a fully open passage section. In the absence of an impulse, the passage section is completely closed and there is no gas component supply (supply cut-off). Examples of supplying a different amount of W ₃ gas component during inhalation anesthesia according to the algorithm according to the invention are shown in FIG. 2a-2c.

If the predetermined amount W ₃ decreases, then the calculated time value T _p and the pulse duration T _pn decrease. The uniform distribution of pulses per unit time in this case takes the form shown in FIG. 2a or in FIG. 2c or in FIG. 2c.

Thus, a predetermined quantity W _{3 of the} gas component is supplied in doses of equal volume by the total number of doses n per unit time minute. The quantity q of the gas component supplied at a dose q = W ₃ / p. The total (volume) amount of the supplied gas component over time T _p : W ₃ = T _pn .nV _ma χ

The error of the gas component supply is determined by the error (T _pn .n Vsc _ax ) ¹ , and at V _max = const and n = const it is determined by the time control error and the error of the transient process when the inertia of the valve closure takes place. As is well known, the errors of time regulation are extremely small. Transient errors (inertia of valve closure) remain.

The error is the same in absolute value over the entire operational range of the quantities of the supplied gas components.

The best embodiment of a device for supplying a gas component.

A device for supplying a gas component during inhalation anesthesia (Fig. 3) contains a shut-off type regulator 1 located in the gas component supply line 2, a timer 3 for generating a signal of controlled pulse action in time, the output of which is connected with the regulator 1, and at the input 4, the value of the set quantity W _{3 of the} gas component is supplied, the device 5 for stabilizing the space velocity of the gas component at the level of the maximum value V _max.

The timer 3 contains an algorithm diagram for effecting the regulatory body 1 by dosing the exposure time with pulses of equal duration and uniformly distributed per unit time according to the invention.

As the regulatory body 1 use an electromagnetic valve.

The stabilization device 5 contains a gear 6 and a throttle 7, sequentially installed along the gas flow in line 2. The throttle 7 is calibrated to the maximum V _ma χ _. The device operates as follows. Preliminarily, using the reducer 6 and throttle 7, the volumetric feed rate of the gas component in line 2 is _calibrated at the level of V _maXs equal to the maximum amount W _{max of} this component, which is required during inhalation anesthesia per unit time (minute).

When the device is running, the timer 3 is set to the value of the amount W _{3 of the} gas component. Timer 3 calculates the time T _p and the pulse duration T _pn and sequentially sends signals of duration T _pn to the regulator 1 uniformly discretizing them according to the algorithm with step H.

When a signal arrives, the regulator 1 is fully opened and supplies the gas stream with a value of V _max for T _pn. In the absence of a signal, the regulatory body 1 is completely closed.

The apparatus for supplying inhalation anesthesia (Fig. 4) contains shutoff type regulating organs 1 located in their own supply lines 2 for each gas component, connected by outputs 8 for mixing the components, a timer 3 for generating time-controlled pulsed signals on the regulating organ 1 of each gas component At the input of timer 3, the values of the set quantity W ₃ ^{m of} each gas component (m = 1.2, etc.) are received. The outputs of the timer 3 are connected with the regulatory bodies 1, respectively, of the component.

Timer 3 contains a circuit for generating a signal of controlled pulse action according to the algorithm for supplying a gas component with pulses of equal duration and uniformly distributed in a unit of time with a step H of at least 0.25 sec.

The algorithm that is used in the inventive device is widely used in industry. In particular, on this basis For example, many transformerless voltage converters, including chargers for mobile phones, work in rhythm. High voltage is applied to the input of such converters, and a low voltage of several volts is received at the output precisely due to the fact that the input voltage is supplied to the device output by short pulses, the duration of which changes as the output voltage deviates from the set value.

“Timer” is a device that, after a specified time, automatically turns on (off) some devices. It is this function that he performs in the inventive device, since it turns on the device for a predetermined time (turns on the gas supply solenoid valve), and after a predetermined time has passed, turns it off (the gas supply stops). After a certain time (a given cycle time equal to "minute /" n "), the cycle repeats.

Such devices are also widely used in industry, including household appliances, in particular, in an electric stove (glass-ceramic work surface with touch control)

In such devices, regulation is carried out precisely by periodically turning on the element in a time cycle of a given duration, while no additional computing devices are used.

4 shows one set timer 3. However, if necessary, other timers can be set, for example, separately for each component

As the regulatory body 1 use an electromagnetic valve. The device for stabilization of the volumetric velocity of each supply line 2 contains a reducer 6 and a throttle 7 sequentially installed along the gas flow in line 2. The throttle 7 in each line 2 is calibrated to its own maximum value V _max ^m The device may contain a bag receiver at the output 8 ( not shown) for additional smoothing of pulsations and averaging of the composition.

The apparatus may comprise a pressure sensor 9 mounted on a flow supply line upstream of the gas component supply device for monitoring pressure.

Figure 4 shows a schematic diagram of an apparatus for inhalation anesthesia containing its own supply lines of three gas components: oxygen O ₂ (m = l), nitrous oxide NОг (m = 2) and xenon Xe (m = 3). The device operates as follows.

Preliminarily, using the reducer 6 and throttle 7, the volumetric feed rate of each gas component in its own line 2 is calibrated at the level of V _max ^m equal to the maximum quantity W _ma χ ^{Ш of} this component required during inhalation anesthesia per unit time (minute).

In operation, timer 3 is set to the value of the amount W ₃ ^{W of} each gas component. Timer 3 calculates the time T _p ^m and the pulse duration T _pP ^w and provides the corresponding signals to the regulator 1 according to the gas component, evenly discretizing them with a step H ^m .

Upon receipt of the signal, the regulatory body 1 is fully open and supplies a gas stream with a value of V _max ^m for T _pn ^m _. In the absence of a signal, the regulatory body 1 is completely closed. In the claimed invention, the flow is always passed through the constricting device at a constant instantaneous speed, and its value is controlled by changing the opening time of the throttle per unit time. The task of stabilizing the flow coefficient is easily solved by stabilizing the differential pressure across the throttle (in the particular case, by stabilizing the pressure only at the inlet, since the pressure at the outlet is almost constant) and, therefore, by stabilizing the Reynolds number. The throttle is calibrated to its own maximum value V ' _n max ^m Adjusting the throttle opening time per unit time does not cause difficulties, since an electromagnetic valve is used as a throttling element. The use of an adjustable opening time of the element dosing the working fluid in a fixed working cycle is widely used in technology and is called “wide-impulse modulation”.

Thus, the nature of regulation has been changed - regulation according to the readings of measuring instruments, based on measuring the differential pressure across the throttle, has been replaced by a calculated timing control with a calibrated differential pressure across the throttle. To organize a gas flow at a level of 10 l / min, it is quite enough to have a valve with a nozzle diameter of 1.5 - 2.5 mm with a pressure drop of about 0.03 - 0.05 kG / cm ² , i.e. at such pressure drops, at which the thermodynamic characteristics of the working fluid can be neglected. Since the maximum stroke of the damper, which ensures full opening of the passage section of the nozzle / damper pair from the “closed” position to the “fully open” position)), is equal to ¹ A of the nozzle diameter, the valve stroke is only 0.4 - 0.6 mm With this move, the response time of the electric thromagnet is in the range of 0.003 - 0.005 seconds. Thus, even with the minimum specified time interval during which the valve is in the open position equal to 0.25 sec, the error introduced by the process of opening the damper does not exceed 2% (0.005 sec from 0.25 sec), and this error is not from upper, and from the current, the minimum, value. The maximum accumulated error from the upper value at, for example, twelve cycles per minute (i.e., at n = 12), will be (0.005 x 12 = 0.06) s, or 0.1% of the upper measurement limit (at which the total duration of the open state of the valve is close to 60 seconds).

Industrial applicability.

The present invention can be used in medicine for inhalation anesthesia.

Claims

CLAIM.

1. The method of supplying the gas component during inhalation anesthesia, in which the gas component is supplied at a volumetric rate, the amount of the gas component supplied per unit time is regulated by a regulator located in the supply line to ensure the quantity specified by the patient’s condition, DIFFERENT by the fact that they stabilize the volumetric velocity at the level of the maximum amount of this component necessary for inhalation anesthesia per unit time, regulation is carried out by the regulatory body shut-off type, the controlled action of which reduces the time of supply of the gas component with a supported constant volume velocity to a calculated value determined by the ratio of the set quantity to the max

15 to the minimum value, in this case, to ensure uniform supply of the gas component, the effect is carried out according to the algorithm, dosing the supply time with pulses of equal duration and uniformly distributed per unit time, while the total pulse duration is equal to the calculated value.

20 2. A device for supplying a gas component during inhalation anesthesia to the respiratory circuit, containing a regulator located in the gas component supply line, DISTINCTIVE in that it uses a shut-off regulator (1) and an additional device (5) for stabilizing

25 gas velocity of the gas component at the maximum value, set on the line along the stream, and a timer (3) for generating a signal of controlled impulse exposure according to the algorithm for supplying the gas component with pulses of equal duration and evenly distributed in a unit of time, with a step H of at least 0.25 sec., while the output of the timer (3) is connected with the regulatory body (1).

3. The device according to claim 2, DIFFERENT in that an electromagnetic valve is used as the regulating body 5 of the shut-off type (1).

4. The device according to claim 2, characterized in that the device (5) for stabilizing the volumetric velocity of the gas component at the maximum value level is made in the form of a reducer (6) and a throttle valve (7) calibrated to the maximum value, sequentially installed along the gas flow.

5. An apparatus for delivering inhalation anesthesia, containing its own supply lines for each gas component of inhalation anesthesia, equipped with its own regulatory authority, and

15 connected by outputs for mixing components, DIFFERENT in that each line (2) has a shut-off type regulating body (1) and further comprises a device for stabilizing the volumetric velocity of the gas component at the maximum value, installed on the line along the flow, and at least ,

20 one timer (3) for generating controlled impulse signals according to the algorithm for supplying a gas component with pulses of equal duration and uniformly distributed per unit time, with a step H of at least 0.25 sec., While the output of the timer (3) is connected with the regulatory body (1 )

25 6. The apparatus according to claim 5, characterized in that in the apparatus, as the regulating body (1) of the shut-off type, an electromagnetic valve is used.

7. The apparatus according to claim 5, characterized in that the device for stabilizing the volumetric velocity of the gas component at the maximum value level is made in the form of a reducer (6) and a throttle (7) calibrated to the maximum value, sequentially installed along the gas flow.

8. The apparatus according to claim 5, DIFFERENT in that it comprises a pressure meter (9) installed at the inlet of the gas component supply line (T).