Monitoring or ventilation apparatus for cardiopulmonary resuscitation with determination of an airway opening index

Abstract

The invention relates to a monitoring and/or respiratory assistance apparatus that can be used during a cardiopulmonary resuscitation (CPR) with successive chest compressions of duration (dt) performed on the patient and with relaxations, said apparatus comprising a CO.sub.2 content measurement sensor (10) a graphical user interface (14), and signal-processing system (11) configured to process the CO.sub.2 content measurement signals in such a way as to determine at least one maximum CO.sub.2 content value (Vmax) and at least one minimum CO.sub.2 content value (Vmin), during at least one duration (dt) of at least one chest contraction, and then to calculate at least one airway opening index AOI or mean index AOI.sub.mean on the basis of the CO.sub.2 content values. Said one or more indices are displayed on the GUI in the form of numerical values or graphical representations, especially curves or pictograms.

Claims

1. A monitoring and/or respiratory assistance apparatus (1) that can be used during a cardiopulmonary resuscitation (CPR) with successive chest compressions of duration (dt) performed on the patient and with relaxations, said apparatus comprising: a CO.sub.2 content measurement sensor (10) configured and adapted for measuring a concentration of CO.sub.2 produced by a patient during the cardiopulmonary resuscitation (CPR), and to supply a CO.sub.2 content measurement signal to a signal-processing system (11), the signal-processing system (11) configured and adapted to process the CO.sub.2 content measurement signal originating from the CO.sub.2 content measurement sensor (10), and at least one graphical user interface (GUI) (14), characterized in that the signal-processing system (11) is configured to: a) determine at least one maximum CO.sub.2 content value (Vmax) and at least one minimum CO.sub.2 content value (Vmin), during at least one duration (dt) of at least one chest compression (CC), and b) calculate at least: one airway opening index AOI such that:
AOI=(Vmax-Vmin)/Vmax Or a mean index AOI.sub.mean on the basis of several successive opening indices AOI obtained during the durations (dt) of n successive chest compressions (with n>1), and c) transmit to said graphical user interface (14) at least one index value AOI or at least one mean index value AOI.sub.mean, and the graphical user interface (14) is configured to display said at least one index value AOI or mean index value AOI.sub.mean, or a graphical representation (16) of said at least one index value AOI or mean index value AOI.sub.mean.

2. The apparatus according to claim 1, characterized in that the signal-processing system (11) is configured to: i) determine several maximum CO.sub.2 content values (Vmax) and several minimum CO.sub.2 content values (Vmin) during the durations (dt) of n successive chest compressions (with n>1), ii) calculate the successive opening indices AOI corresponding to said several maximum CO.sub.2 content values (Vmax) and several minimum CO.sub.2 content values (Vmin), and iii) calculate a mean index AOI.sub.mean on the basis of the successive AOI indices obtained for the n chest compressions.

3. The apparatus according to claim 1, characterized in that the signal-processing system (11) is configured to calculate a mean index AOI.sub.mean on the basis of the successive AOI indices obtained for n chest compressions, such that:
AOI.sub.mean=Σ.sub.i=1.sup.nAOI(i)/n where: n is an integer of CC, with n>1.

4. The apparatus according to claim 1, characterized in that the graphical user interface (14) is configured to display said at least one index value AOI or mean index value AOI.sub.mean expressed in the form of a percentage.

5. The apparatus according to claim 1 characterized in that the graphical user interface (14) is configured to display at least one index value AOI or mean index value AOI.sub.mean in the form of a graphical representation (16) chosen from a pictogram, a curve, a bar graph or a pie chart.

6. The apparatus according to claim 1, characterized in that the CO.sub.2 content measurement sensor (10) comprises a capnometer configured to perform CO.sub.2 content measurements continuously.

7. The apparatus according to claim 1, characterized in that the signal-processing system (11) comprises at least one microprocessor (12) programmed with at least one algorithm.

8. The apparatus according to claim 1, further comprising an alarm configured to trigger when AOI<0.75 (i.e. <75%) or AOI.sub.mean<0.75 (i.e. <75%).

9. The apparatus according to claim 8, characterized in that the alarm comprises an acoustic or visual alarm, and the GUI (14) is configured to display said visual alarm.

10. The apparatus according to claim 1, characterized in that the graphical user interface (14) comprises a digital screen.

11. The apparatus according to claim 1, characterized in that the apparatus is chosen from among an assisted ventilation apparatus comprising a source (2) of respiratory gas and a micro-blower.

12. The apparatus according to claim 1, characterized in that the apparatus is chosen from among a cardiac monitor or a cardiac monitors/defibrillator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be better understood from the following detailed description given as a non-limiting example and with reference to the appended figures, in which:

(2) FIG. 1 is a schematic view of a monitoring and respiratory assistance apparatus according to the invention,

(3) FIG. 2 is an example of a curve of the CO.sub.2 content over time, corresponding to airways that are well open,

(4) FIG. 3 is similar to FIG. 2 but corresponds to airways that are a little less open than in the case of FIG. 2,

(5) FIG. 4 is similar to FIG. 2 but corresponds to airways that are closed or just slightly open.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) FIG. 1 is a schematic representation of an embodiment of a respiratory assistance apparatus or medical ventilator according to the invention used for delivering a respiratory gas, typically air or oxygen-enriched air, to a patient P during cardiopulmonary resuscitation (CPR), that is to say to a person who is in cardiac arrest and on whom a first responder performs cardiac massage, that is to say an alternation of chest compressions (CC) and relaxations (R), that is to say non-compressions.

(7) This apparatus or ventilator 1 comprises a source 2 of respiratory gas, such as a motorized micro-blower, which is in fluidic communication with a gas conduit 3 for delivering the respiratory gas to the patient P during cardiopulmonary resuscitation, typically pressurized air, for example via flexible conduit 4 and a gas distribution respiratory interface 5, for example a respiratory face mask or laryngeal mask, a tracheal tube or the like.

(8) The source 2 of respiratory gas is governed, that is to say controlled, by signal-processing and control means 6, in particular an electronic board with microprocessor or similar. The control means 6 control the source 2 of respiratory gas in such a way that it delivers the gas in accordance with one or more predefined ventilation modes that are stored in a memory 7, for example in accordance with a “normal” ventilatory mode, corresponding to ventilation of a patient who is not or no longer in cardiac arrest, and a “CPR” ventilatory mode corresponding to ventilation of a patient who is in cardiac arrest and on whom a first responder initiates or performs CPR.

(9) For example, in accordance with a ventilatory mode intended for CPR, the source 2 of respiratory gas is controlled so as to deliver air in a ventilatory cycle comprising several pressure levels or of the BiPAP type, in particular two pressure levels comprising a low pressure level, for example a low pressure (LP) of between approximately 0 cm H.sub.2O and 15 cm H.sub.2O, and a high pressure level, for example a high pressure (HP) of between approximately 7 cm H.sub.2O and 40 cm H.sub.2O. The gas is delivered alternately between these two pressure levels (LP, HP) throughout the CPR performed by the first responder, that is to say while the first responder performs the chest compressions and relaxations. The duration (D.sub.LP) of delivery of gas at low pressure (LP) by the micro-blower 1 is between 2 and 10 seconds, typically of the order of 3 to 6 seconds, whereas the duration (D.sub.HP) of delivery of gas at high pressure (HP) is less than 3 seconds, for example of the order of 0.5 to 1.5 seconds.

(10) The micro-blower 1 of the ventilator generates two pressure levels, namely a high pressure level (i.e. HP) and a low pressure level (i.e. LP). The cardiac massage alternating between phases of chest compression (CC) and relaxation generates pressure peaks, which are superposed on the pressure cycles of the ventilator. This results in pressure peaks at the high plateaus (i.e., at HP) and low plateaus (i.e. at LP) which reflect the chest compressions with increased pressure, since the chest yields under the pressure of the chest compressions performed by the first responder, and the relaxations with low pressure, since the chest rises again in the absence of chest compressions.

(11) The air delivered by the micro-blower 2 is conveyed through the gas conduit 3 which forms all or part of the inhalation branch 3a of the patient circuit of the ventilator 1.

(12) The gas conduit 3 is in fluidic communication with the respiratory interface 5, via the flexible tubing 4, in such a way as to deliver to it pressurized air originating from the micro-blower 2. The gas conduit 2 will be attached to the respiratory interface 5 by way of an intermediate attachment piece 8, here a Y-shaped piece. This Y-shaped intermediate attachment piece 8 comprises internal gas passages and is moreover attached to an exhalation branch 3b of the patient circuit of the ventilator 1, so as to be able to collect and convey the gases rich in CO.sub.2 that are exhaled by the patient and to discharge them to the atmosphere (at 9).

(13) Also provided are means 10 for measuring the CO.sub.2 content, called a CO.sub.2 sensor 10 or capnometer, which means are designed to perform measurements of the concentration of CO.sub.2 in the gases exhaled by the patient P and to deliver CO.sub.2 content measurement signals to signal-processing means 11 where these measurement signals can be processed, in particular by one or more calculation algorithms or similar.

(14) In the embodiment in FIG. 1, the CO.sub.2 sensor 10 is arranged near the mouth of the patient P in the mainstream configuration, that is to say upstream from and in immediate proximity to the respiratory interface 5, preferably between the Y-shaped piece 8 and the respiratory interface 5, e.g. a tracheal tube.

(15) However, the CO.sub.2 sensor 10 may also be arranged in the sidestream configuration, for example in the framework 20 of the respiratory assistance apparatus 1 and is connected, via a gas sampling line, such as tubing or the like, to a gas sampling site situated upstream from and in immediate proximity to the respiratory interface 5, for example on the junction piece 18. This gas sampling line allows gas to be sampled and then conveyed to the CO.sub.2 sensor 10.

(16) The CO.sub.2 sensor 10 performs continuous measurements of the concentration of CO.sub.2 in the gases expired by the patient P, in particular the gas flowing through the Y-shaped piece 8, which gas is enriched in CO.sub.2 during its passage through the lungs of the patient P, where gaseous exchanges take place.

(17) The CO.sub.2 content measurement signals are then transmitted by the CO.sub.2 sensor 10 to the signal-processing means 11 via an electrical connection 13 or similar, in particular by wires or the like, which signal-processing means (11) preferably comprise an electronic board 12 with a microprocessor, preferably with a microcontroller, using one or more algorithms.

(18) Preferably, the signal-processing means 11 are connected electrically to the storage means 7, for example a memory card or similar, so as to be able to record there all or some of the CO.sub.2 content values measured over time, in particular during the chest compressions.

(19) It will be noted that, depending on the embodiment chosen, the signal-processing means 11 and the control means 6 can be combined, arranged on or comprise one and the same electronic memory card, or they can be arranged on or comprise separate electronic cards.

(20) In the context of the present invention, the monitoring of an AOI index is of great importance since the first responder is thereby informed in real time of the opening or non-opening of the airways and thus knows whether or not the successive chest compressions performed generate a ventilation flowrate in the patient P.

(21) More precisely, the signal-processing means 11 are configured to:

(22) a) determine at least one maximum CO.sub.2 content value (Vmax) and at least one minimum CO.sub.2 content value (Vmin), during at least one duration (dt) of at least one chest compression (CC), and

(23) b) one airway opening index AOI such that:
AOI=(Vmax−Vmin)/Vmax

(24) Preferably, the signal-processing means are configured to:

(25) i) determine several maximum CO.sub.2 content values (Vmax) and several minimum CO.sub.2 content values (Vmin) during the durations (dt) of n successive chest compressions (with n>1),

(26) ii) calculate the successive opening indices AOI, as above, corresponding to the maximum CO.sub.2 content values (Vmax) and several minimum CO.sub.2 content values (Vmin), and

(27) iii) calculate a mean index AOI.sub.mean on the basis of the successive AOI indices obtained for the n chest compressions, with: AOI.sub.mean=Σ.sub.i=1.sup.nAOI(i)/n where: n is an integer of CC, with n>1.

(28) The storage means 7 can also record all or some of the values of the AOI index and of the mean AOI index AOI.sub.mean calculated by the signal-processing means 11.

(29) More generally, it has been found in practice that the indices AOI and preferably AOI.sub.mean reflect the opening of the patient's airways, during the cardiac massage, and inform the first responder(s) in real time of the opening or non-opening of these airways. This information is very useful to the first responder in order to ascertain whether the air insufflation performed during the cardiac massage is effective or not, that is to say whether or not air is reaching the small intrapulmonary airways

(30) To this end, the apparatus 1 of the invention additionally comprises at least one graphical user interface or GUI 14, such as a digital screen (e.g. colour, black and white, or both), preferably a touch screen, connected electrically to the signal-processing means 11 which are configured to transmit to the GUI 14 the one or more values of the index AOI or of the mean index AOI.sub.mean that have been calculated as explained above.

(31) The GUI 14 for its part is configured to display this value of the index AOI or of the mean index AOI.sub.mean. In other words, the GUI 14 displays the index either in the form of a numerical value, preferably expressed as a percentage, or in the form of one or more graphical representations 16, or both. Examples of a graphical representation 16 include a pictogram, that is to say a drawing or the like, a bar graph, a curve, a pie chart, for example an icon or the like which represents lungs and whose size and/or colour varies depending on the value of the index AOI or AOI.sub.mean that has been determined.

(32) The graphical representation 16 can be different depending on the value of the index displayed, in order to facilitate its interpretation or understanding by the first responder, and in particular it can have a size proportional to the value of the index to be displayed and/or a different colour depending on the value of the index to be displayed.

(33) For example, it is possible to display a drawing of the lungs:

(34) of a small size, and for example red in colour, for index values AOI or AOI.sub.mean less than a predefined threshold value, for example <0.75 (or 75%),

(35) of a medium size, and for example orange in colour, for index values AOI or AOI.sub.mean between 0.75 and 0.9 (or 75% to 90%), and

(36) of a large size, and for example green in colour, for index values AOI or AOI.sub.mean greater than a predefined upper threshold value, for example >0.9 (or 90%).

(37) It is also possible to provide acoustic or visual alarm means configured to trigger when an index value AOI or a mean index value AOI.sub.mean is less than a given alarm threshold, preferably when AOI<0.75 (i.e. <75%) or AOI.sub.mean<0.75 (i.e. <75%), preferably a visual alarm, and the GUI 14 is configured to display said visual alarm.

(38) A source 15 of electric current, such as a rechargeable battery or similar, directly or indirectly supplies electric current to the signal-processing means 11 and the control means 6, the micro-blower 2, the GUI 14 or any other element of the apparatus, in particular the storage means 7. The source 15 of electric current is preferably arranged in the framework 20 of the ventilator.

(39) The apparatus 1 according to the present invention is particularly suitable for use during cardiopulmonary resuscitation (CPR) on a person (i.e., a patient) in cardiopulmonary arrest, in the context of which a respiratory gas such as pressurized air is supplied, in accordance with a ventilatory cycle with several pressure levels, to said person undergoing the cardiac massage with alternating chest compressions and relaxations. To facilitate its transport by the first responders, for example by a physician, a nurse, a fire-fighter or similar, the ventilator of the invention is preferably arranged in a bag for carrying it.

(40) The apparatus 1 according to the present invention can be a medical ventilator, as described above, or a monitor or a combined cardiac monitor/cardiac defibrillator for additionally monitoring the cardiac activity of the patient, especially via electrodes, and optionally delivering electric shocks.

(41) FIGS. 2 to 4 illustrate the present invention.

(42) More precisely, FIGS. 2 and 3 are examples of CO.sub.2 content curves over time, corresponding to airways that are fully open (FIG. 2) or to airways that are almost fully open (FIG. 3), that is to say very slightly closed in relation to those of FIG. 2.

(43) As will be seen, these curves comprise CO.sub.2 peaks which are produced during the chest compressions performed by the first responder on the patient P during the cardiac massage. The CO.sub.2 content is expressed here in mmHg, i.e. partial CO.sub.2 pressure (mmHg) in the gas; however, the CO.sub.2 content could be expressed with another magnitude, for example a % by volume, a molar % or the like.

(44) Each CO.sub.2 content peak is characterized by a high value (CO.sub.2 max) and a low value (CO.sub.2 min) corresponding to the maximum CO.sub.2 content value (Vmax) and minimum CO.sub.2 content value (Vmin) that are used to determine the indices AOI and AOI.sub.mean. The amplitude ΔCO.sub.2 of each peak corresponds to the difference Vmax−Vmin during each chest compression performed during the cardiac massage.

(45) In FIG. 2, the minimum CO.sub.2 content value is equal to 0, hence the index AOI is equal to 1, or 100%, which corresponds to fully open airways, for which the gas transfers are optimal in the patient's lungs.

(46) Moreover, in FIG. 3, it will be seen that in this case the minimum CO.sub.2 content value is close to 0, hence the index AOI is close or very close to 1, for example of the order of approximately 90 to 99%, which corresponds to airways that are almost fully open, for which the gas transfers are still very good.

(47) Conversely, FIG. 4 illustrates a CO.sub.2 curve obtained for a patient with closed airways, for which the gas exchanges are poor. As will be seen, in this case the amplitude ΔCO.sub.2 of each peak, which corresponds to the difference Vmax−Vmin, is very small, that is to say the high (CO.sub.2max) and low (CO.sub.2min) values are close, hence the difference (Vmax-Vmin) tends towards 0. In this case, there is a low AOI index value, for example below 0.2 (i.e. <20%).

(48) It will be immediately appreciated that, by providing the first responder with this AOI index value for each peak, that is to say each chest compression, or a mean value AOlmean over several chest compressions, that is to say corresponding to several successive peaks, said first responder can immediately have a good idea of the state of opening of the patient's airways and will be able to act accordingly.

(49) Knowing more precisely the state of opening of the airways, i.e. the AOI index according to the invention, the first responder will have better information concerning what is called the “effective” ventilation of the patient, that is to say the quantity of ventilation reaching the alveoli and thus participating in the gas exchanges through the alveolar-capillary membrane of the patient. It is indeed this “effective” ventilation of the patient that permits efficient re-oxygenation of the patient's blood and removal of the CO.sub.2 that it contains, by diffusion through the alveolar-capillary membrane of the patient's lungs.

(50) Knowing this AOI index, the user, typically the first responder, can decide to adjust the ventilation by modifying all or some of the ventilation parameters when he ascertains that it is not sufficiently effective, that is to say when the re-oxygenation of the patient's blood is insufficient.

(51) In other words, through knowledge of the AOI index of the invention, the user can carry out different adjustments of the medical device, in particular of the ventilator serving to supply respiratory gas to the patient, in order to perform a ventilation that is as effective as possible for the patient. This information on the state of opening of the airways also allows the first responder to take therapeutic decisions, especially on whether to continue or stop the cardiopulmonary resuscitation (CPR) performed on the patient.