DE2413988A1 - PROCEDURE AND ARRANGEMENT FOR CARRYING OUT THE PROCEDURE FOR EXPLORING INTRATHORACAL RESPIRATORY MECHANICS - Google Patents

Description

INSTITUT EATIOIfAL de la SANTE et de la RECHERCHE MEDICALE, PARIS (France)

Method and arrangement for carrying out the method for researching intrathoracic respiratory mechanics

The invention relates to a method for researching intrathoracic respiratory mechanics and to an arrangement for Implementation of this procedure.

Such research is based on the considerations set out below.

Breathing mechanics regards the passive breathing system as a linear system of the second order. In addition, can

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show and investigate experimentally that at the time of Resting breathing the inertial forces can be neglected. This sets the "system under consideration" to such a one first order.

Apparent theoretical reasons (not laminar flow in the airways, not following Hooke's law Tissue deformation, non-Newton viscosity of the tissue) that the linear hypothesis is only an approximation. However, the experiment shows that the approximation in normal humans is excellent at rest and is usually acceptable even with the patient.

On this assumption, by writing that the pressure of movement Δρ im developed by the respiratory muscles Equilibrium with the effect of the withdrawal forces (spring forces and surface tension) and the drag forces (aerodynamic and tissue-wise) results from consideration of the intrathoracic organs under exclusion the chest wall:

E (Yp - Vr) + R dTp / dt = Δρ

In this equation:

E is the intrathoracic extensibility R the intrathoracic resistance Vp the lung volume Vr is the relaxation volume

After the introduction of the formula function C = ^, this results

Vp + RC dVp / dt = Vr + CAP

So that only directly measurable quantities occur, one takes for

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A P the changes given by a small balloon of the esophageal pressure and for the volume V which is spread out or displaced at the mouth:

Vp = Yo + V
Vo is the lung volume at the beginning of inhalation.

The changes in the internal lung pressure are thus neglected and the change in state of the inhaled air is considered to be instantaneous. The inhaled air changes from the ambient state (ATPS) to the JQsreolar state (BTPS). dV / dt is supplied by a pneumotachograph (PTG) whose signal, which is integrated as a function of time, gives the volume V.
The result is:

V + RC H = Vr - Vo + C Δρ

In the known state of the art, a classic method consists of recording Δρ and V as well as deriving

dV
tung · & as a function of time, ii for two points with

dv
ITulausfluss ^ = O results in:

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For two points of equal volume V, we get:

Another classic method is to use a

α dV

Curve V as a function of Δρ and another curve ^

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as a function of Δρ. In the loop of V, the two points with zero flow are determined by their horizontal tangents. The fill is the slope of the diameter in between. In the loop of -π , the two points of equal volume are taken, which allows R to be calculated.

However, these two classic methods have several disadvantages:

1.) You only use two cycle points and not all of the information.

2) The determination of these points is very subjective as a function of the disturbance superimposed on the curve. This disruption is inevitable because it is not instrumental but biological (especially heart rate loss). Because of this, the signal / interference ratio is often very high mediocre and the determination of the zero outflow points, the attachment of the tangents to the loop and the Determination of the points of equal volume become very arbitrary.

3) Breathing, like many, is biological. Appearances not periodic, but pseudo-periodic. Even in the Resting behavior, successive breathing cycles are not identical. Choosing a cycle as representative of the middle state is therefore very arbitrary. A satisfactory determination of the mean state would require observation of a large number of cycles due to the cumbersome nature of the procedure is not appropriate.

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4) It is not a device for correct calibration of the! gneumotachograph and the change of the calibration factor inhalation - exhalation is ignored.

5) The inhalation and the exhalation cannot be observe separately. '

6) The procedures are slow and arduous.

Object of the invention, which relates to a method for researching intrathoracic breathing mechanics using of a small balloon that sends a signalAρ the Changes in esophageal pressure are provided by a pneumotachograph, which provides a function of time

dV
derived signal -rr of the volume V displaced by the mouth, and an integrating _{circuit which receives the signal ^ x em} and outputs the signal V, it is therefore to eliminate the aforementioned disadvantages. According to the invention, this is achieved in that an oscilloscope receives the signal Δ ρ at its horizontal input and a signal y at its vertical input, which is as follows:

where Λ is an adjustable parameter that the parameter A. is set in such a way that the loop visible on the oscilloscope screen closes into a straight line, and that the inclination of this straight line corresponds to the lullung C and the Quotient of the division of the parameter Λ by the filling G gives the intrathoracic resistance R. It will be noted that closing a loop into a straight line is a is particularly unalterable, error-free and accurate in oscillography.

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In addition, it is enough to set the parameter to zero to get a loop, its surface measures intrathoracic work of breath per cycle.

The invention is suitable for completing the method outlined above in order to adjust the gain, to allow calibration and separate observation of two respiration times.

In the following, the calibration of the pneumotachograph (PTG) in the alveolar states (BTPS) is pointed out.

dV The pneumotachograph gives an output proportional to -r Signal off. The calibration factor is proportional to the viscosity of the gas mixture that traverses it. This viscosity depends on the temperature and the water vapor content. It is therefore not the same for inhaled air and the exhaled gas, which is saturated with water vapor at body temperature.

It is impossible to determine the temperature of the gas in the pneumotachograph from the outset because of the heat exchange that takes place to know between the gas and the walls. Furthermore, the viscosity is not an additive property. It is impossible, to derive the viscosity of the gas mixture from the viscosities of its components. So it is impossible To recognize from the outset how the calibration factor of the pneumotachograph between inhalation and exhalation varies. It is only possible to do this empirically by using the same gas mixture for the inhaled air and for the exhaled air To turn on the gas.

It is known to implement a calibration pump for the alveolar states for this purpose.

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A cylindrical container contains water kept ^{thermostatically at 37 ° C.} A turbine ensures the exchange of heat and moisture between the water and the air it contains. A plunger allows the volume of the container to be varied. The calibration pneumotachograph is attached to a pipe socket attached to the container lid. It is traversed by the ambient air during inhalation when the piston descends and by the gas in the alveolar states during exhalation when the piston is raised.

An example of an arrangement for carrying out the method is described below, reference being made to the figure is taken.

dV

A pneumotachograph 1 sends a signal + xr to a potentiometer 3 to adjust the gain. The wiper of the potentiometer 3 feeds a detector circuit 5 for

3-TT ·

the sign of - * rr . When inhaling, the detector circuit 5 closes its contact 7, so that a relay 11 is fed via a switch 9. The wiper of the potentiometer 3 is also connected to a potentiometer 13 for gain correction during exhalation. Its effect is canceled when inhaling due to the bridging by means of a working contact 15 of the relay. The wiper of the potentiometer 13 feeds an operational amplifier 17, which is connected as an integrator and • inverter and at the output of which the signal -V is obtained. The wiper of the potentiometer 13 also feeds a single-pole switch 19, which serves as a gain switch and acts both in the gain position 0 and in the positions 1 and 10 on an inverting amplifier 21, which is a potentiometer

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to set the adjustable parameter λ. This is what you get on the wiper of this potentiometer 23

dV dV

Signal -A ^. The two signals -V and -λ-j ^ are by means of an adder-inverter 25 summed at its output the signal y = V + A ^ is obtained. The signal y is running either via the normally closed contact 27 of the relay 11 and one Switch 29 or via the normally open contact 31 and one Switch 33 and goes to the active Y-vertical deflector plate of an oscilloscope 35. A small balloon 37 delivers the signal Δρ to the active Σ horizontal deflection plate of the oscilloscope 35. Under certain circumstances, if a retentive screen is present, this can be done with an instant photo camera equip (e.g. Polaroid camera).

The pneumotachograph 1 is mounted on the calibration pump (not shown). The calibration does not take place at the outflow, but instead at the volume in the integrator 17, which has a time constant of 1 see. Has.

When the switch 19 receives the input of the adder 25 from Signal ^ blocks, 35 V is recorded on the oscilloscope as a function of time. The sign detector 5 switches

dV

the potentiometer 13 for the signal -rr on exhalation and the short circuit on inhalation. The switches 29 and 33 are closed in such a way that, on the one hand, inhalation and, on the other hand, exhalation can be recorded. If the calibration pump neither generates nor consumes gas, the same air mass passes through the pneumotachograph on inhalation in the ATPS states and on exhalation in the BTPS states.

The potentiometer 13 is operated so that the mean value of the signal becomes zero. This calibration correction is

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much more exact if one observes the volume and not the outflow, since a possible inequality of the calibration integrated with each cycle and even visible when it is very small.

Then press potentiometer 3 to set the desired value for a known volume (500, 750 or 1000 enr) to get observed distraction.

In the following, it is possible to observe the inhalation and exhalation separately.

In the normal state, the resistance to inhalation and exhalation is just as great, at least when resting. At the This can be different for sick people. There is then the advantage of separate observation of inhalation and exhalation. This is made possible by the switches 29 and 33, which are assigned to the relay 11 and controlled by the detector 5 will.

Finally, important values of R can be observed in the patient. The switch 19 allows the use of the Inverter circuit 21 with amplification 10. You can then Time constants RC up to 10 see. watch what all Covers needs in pathology.

According to the above explanation, it goes without saying, that, compared with the classical method, the use of the arrangement according to the invention has the following advantages:

1) The entirety of the information provided by the observed cycle is used.

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2) Thanks to the remanence of the screen, the information provided over several cycles is used. The values determined for R and C are therefore representative of (Xen mean state of the passive intrathoracic respiratory system.

3) The eye is very sensitive to recognizing the straight line and certainly much better with a disturbed signal a straight line as a curve or a loop.

4-) By using a memory oscilloscope you can the use of photographic recordings is not applicable.

5) The correct calibration of the pneumotachograph at two breathing times is accurate and quick.

6) The entire process is quick and easy and has few subjective elements.

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Claims (2)

Claims 1. A method for researching intrathoracic respiratory mechanics using a small balloon that delivers a signal A ρ of the changes in esophageal pressure, a pneumotachograph that uses a dV The time-derived signal -s-r des from the mouth gives ^ατ gives / ^ατ displaced volume V /, and an integrating circuit which receives the signal ^ and emits the signal V, characterized in that an oscilloscope (35) receives the signal Λ ρ at its horizontal input and a signal y at its vertical input, which is as follows: where Λ. one adjustable parameter is that the Parameter X is set in such a way that the. loop visible on the screen of the oscilloscope (35) closes to a straight line, and that the inclination of this straight line is the filling G and the quotient of the division of the Parameter Λ gives the intrathoracic resistance R through the filling C. 2. The method according to claim 1, characterized in that that the surface of the visible loop on the screen of the oscilloscope (35) for the value of zero des adjustable parameter λ measures the intrathoracic work of breathing per cycle. .J arrangement for carrying out the method according to claim or 2, characterized in that the pneumotachograph (1) sends the signal ^ to a potentiometer (3) for amplifier setting that the grinder des - 12 409839/0833 Potentiometer (3) for setting the gain a circuit (5) feeds the sign of the signal evaluates and feeds a relay (11) when inhaled, that the wiper of the potentiometer (3) for gain adjustment feeds a potentiometer (13) for gain correction during exhalation, that a normally open contact (15) of the relay (11) the input and the slider of the Potentiometer (13) for gain correction during exhalation short-circuits that the wiper of the potentiometer (13) for gain correction during exhalation an integrating-inverting circuit (17) feeds, which supplies the signal -V, that a single pole switch (19) with three Positions (0, 1 and 10) are provided by the potentiometer slider (13) for gain correction is also fed during exhalation and acts on an inverting amplifier (21), which is a potentiometer (23) controls to set the adjustable parameter, and that an adder-inverter (25) controls the Signal -V from the integrating-inverting circuit (17) -λ dV
and the signal - A * -rr from the wiper of the potentiometer (23) receives and the y- ~ signal either via a normally closed contact (27) of the relay (11) and a switch (29) or a normally open contact (31) of the relay (11) and a switch (33) outputs to the vertical input of the oscilloscope (35). 409839/0833