Ventilation apparatus for cardiopulmonary resuscitation with display of the trend in CO.SUB.2

Abstract

The invention relates to a respiratory assistance apparatus for delivering a respiratory gas, such as air, to a patient during cardiopulmonary resuscitation (CPR), having a source (1) of respiratory gas, means (4) for measuring the CO.sub.2 content, and signal-processing and control means (5). The signal-processing and control means (5) are configured to process the CO.sub.2 content measurement signals corresponding to measurements performed by the CO.sub.2 content measurement means (4) during a given period of time (dt), and to calculate at least one mean CO.sub.2 content value (Vmean) from the maximum CO.sub.2 content values (Vmax) obtained over the time window (Ft), and to transmit said at least one mean CO.sub.2 content value (Vmean) to the graphical user interface (7) which displays it.

Claims

1. A respiratory assistance apparatus for delivering a respiratory gas to a patient during cardiopulmonary resuscitation (CPR), comprising: a source (1) of the respiratory gas for delivering the respiratory gas to said patient during the cardiopulmonary resuscitation (CPR), a CO2 content measurement device (4) for measuring a CO.sub.2 content produced by the patient, and to supply CO.sub.2 content measurement signals to a signal-processing and control system (5), the signal-processing and control system (5) configured to process the CO.sub.2 content measurement signals originating from the CO.sub.2 content measurement device (4), and at least one graphical user interface (7), characterized in that: the signal-processing and control system (5) is configured: a) to process the CO.sub.2 content measurement signals corresponding to the measurements performed by the CO.sub.2 content measurement device (4) during a given time period (dt), and to extract therefrom a plurality of end tidal CO.sub.2 (EtCO.sub.2) content values, b) to select a maximum EtCO.sub.2 content value (Vmax) from said plurality of EtCO.sub.2 content values measured during said given time period (dt), c) to repeat steps a) and b) in order to obtain several successive maximum EtCO.sub.2 content values (Vmax) measured over a time window (Ft) comprising several successive time periods (dt), d) to calculate at least one mean CO.sub.2 content value (Vmean) from only the several successive maximum EtCO.sub.2 content values (Vmax) obtained over the time window (Ft), and e) to transmit said at least one mean CO.sub.2 content value (Vmean) to the graphical user interface (7), and the graphical user interface (7) is configured to display said at least one mean CO.sub.2 content value (Vmean).

2. The apparatus according to claim 1, characterized in that the signal-processing and control system (5) is configured to repeat the steps a) to e) in such a way as to obtain several successive mean CO.sub.2 content values (Vmean) calculated based on the several successive maximum EtCO.sub.2 content values (Vmax) obtained over successive time windows (Ft), preferably a sliding time window (Ft).

3. The apparatus according to claim 2, characterized in that the time window (Ft) is between 20 seconds and 10 minutes.

4. The apparatus according to claim 1, characterized in that the graphical user interface (7) is configured to display said at least one mean CO.sub.2 content value (Vmean) in the form of a graphical representation or a numerical value.

5. The apparatus according to claim 1, characterized in that the graphical user interface (7) is configured to display at least some of the calculated successive mean CO.sub.2 content values (Vmean) in the form: of a curve composed of a succession of graphical symbols, each graphical symbol corresponding to said at least one mean CO.sub.2 content value (Vmean), or of a bar graph comprising several bars, each bar of said bar graph corresponding to a mean CO.sub.2 content value (Vmean).

6. The apparatus according to claim 1, characterized in that the signal-processing and control system (5) comprises at least one microprocessor.

7. The apparatus according to claim 1, characterized in that the CO2 content measurement device (4) for measuring the CO.sub.2 content comprises a capnometer.

8. The apparatus according to claim 1, characterized in that the source (1) of respiratory gas is in fluidic communication with a gas conduit (2), the gas conduit (2) being in fluidic communication with a respiratory interface (3).

9. The apparatus according to claim 8, characterized in that the CO2 content measurement device (4) for measuring the CO.sub.2 content is arranged: either upstream from and in immediate proximity (18) to the respiratory interface (3), or in the apparatus, being connected to a gas sampling site (18) situated upstream from and in immediate proximity to the respiratory interface (3).

10. The apparatus according to claim 1, characterized in that the given time period (dt) is between 2 and 10 seconds.

11. The apparatus according to claim 1, characterized in that the CO2 content measurement device (4) for measuring the CO.sub.2 content is configured to perform measurements continuously.

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

13. The apparatus according to claim 1, characterized in that the signal-processing and control system (5) is configured to control the source (1) of respiratory gas and to deliver the respiratory gas in ventilatory cycles comprising two pressure levels, the source (1) of respiratory gas comprising a motorized micro-blower.

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 graphical representation of the variations of the CO.sub.2 content in the respiratory gases of a normal patient,

(3) FIG. 2 is a diagram showing a ventilatory cycle with two pressure levels that can be used by the apparatus of FIG. 6 in order to ventilate a patient in cardiopulmonary arrest during CPR,

(4) FIG. 3 illustrates the pulmonary pressure variations of a patient in cardiopulmonary arrest during CPR,

(5) FIG. 4 is a diagram showing the quantity of CO.sub.2 measured by the capnometer of the apparatus of FIG. 6 during CPR, at the moment of and after resumption of spontaneous cardiac activity (RSCA),

(6) FIG. 5 is a diagram showing the CO.sub.2 content peaks during the ventilatory cycles implemented during CPR,

(7) FIG. 6 is a diagram showing an embodiment of a respiratory assistance apparatus for CPR according to the invention, and

(8) FIG. 7 is a diagram showing the measurements and time intervals used to calculate and display the trend in CO.sub.2. Successive CO.sub.2 content measurement time period (dt) are shown from which the Vmax1, Vmax 2, Vmax3 and Vma4 are selected. Sliding windows Ft.sub.1, Ft.sub.2 and Ft.sub.3 corresponding to three dt's are shown, for which Vmean1 and Vmean 2 are calculated.

DESCRIPTION OF PREFERRED EMBODIMENTS

(9) FIG. 6 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, with an alternation of chest compressions (CC) and relaxations (Re).

(10) The apparatus comprises a source 1 of respiratory gas, such as a motorized micro-blower, which is in fluidic communication with a gas conduit 2 of the inhalation branch 2a of the patient circuit 2a, 2b in order to deliver the respiratory gas to said patient P during the CPR.

(11) The source 1 of respiratory gas is governed, that is to say controlled, by signal-processing and control means 5, in particular an electronic board with microprocessor 6 or similar. The signal-processing and control means 5 control the source 1 of respiratory gas in such a way that it delivers the gas in accordance with one or more predefined ventilation modes.

(12) It preferably makes it possible to control the source 1 of respiratory gas so as to deliver the gas in accordance with a “normal” ventilatory mode, corresponding to ventilation of a patient who is not 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.

(13) For example, in accordance with a ventilation mode intended for CPR, the source 1 of respiratory gas is controlled so as to deliver the respiratory gas, typically air, in a ventilatory cycle comprising several pressure levels or of the BiPAP type, as illustrated in FIG. 2, 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.

(14) The gas is delivered alternately between these two pressure levels (LP, HP), as is illustrated in FIG. 2, 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.

(15) The chest compressions (CC) and relaxations (Re) resulting from the cardiac massage will themselves bring about pressure variations in the lungs of the patient, which will increase or decrease the pressure supplied by the micro-blower 1, and this will lead, in the patient's lungs, to a pressure curve as illustrated in FIG. 3 where the pressure peaks at the high plateaus (i.e. at HP) and low plateaus (i.e. at LP) reflect the chest compressions (CC) with increased pressure, since the chest yields under the pressure of the CC performed by the first responder, and the relaxations (Re) with low pressure, since the chest rises again in the absence of CC.

(16) As will be seen from FIGS. 2 and 3, the given time period (dt), during which the plurality of CO.sub.2 content values are measured and the maximum CO.sub.2 content value (Vmax) is extracted therefrom, corresponds to the duration (D.sub.LP) of delivery of gas at low pressure (LP), i.e. between 2 and 10 seconds, typically between 3 and 6 seconds.

(17) The gas delivered by the micro-blower 1 is conveyed through the gas conduit 2 which forms all or part of the inhalation branch 2a of the patient circuit 2a, 2b. The respiratory gas, generally air, is delivered to the patient via a gas distribution interface, for example here an endotracheal intubation tube 3, more simply called a tracheal tube. However, other interfaces may be used, in particular a face mask or a laryngeal mask.

(18) The gas conduit 2 of the inhalation branch 2a is in fluidic communication with the tracheal tube 3 in such a way as to supply the latter with the gas, such as air, originating from the source 1 of respiratory gas. The gas conduit 2 will in fact be attached to the tracheal tube 3 by way of an intermediate attachment piece, typically a Y-shaped piece 8 comprising internal passages for the gas. This Y-shaped intermediate attachment piece 8 comprises internal passages for gas.

(19) The Y-shaped piece 8 is likewise attached to the exhalation branch 2b of the patient circuit 2a, 2b so as to be able to collect and convey the gases rich in CO.sub.2 that are exhaled by the patient P and to discharge them to the atmosphere (at 9).

(20) Also provided are means 4 for measuring the CO.sub.2 content, called a CO.sub.2 sensor or more simply a capnometer, which means are designed to perform measurements of the concentration of CO.sub.2 in the gas exhaled by the patient P and to deliver the corresponding CO.sub.2 content measurement signals to the signal-processing and control means 5, where these measurement signals can be processed by one or more calculation algorithms or similar.

(21) In the embodiment in FIG. 6, the CO.sub.2 sensor 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 3, preferably between the intermediate attachment piece 8, i.e. the Y-shaped piece, and the respiratory interface 3, i.e. the tracheal tube, for example on a junction piece 18 (cf. FIG. 6).

(22) According to another embodiment (not shown), the CO.sub.2 sensor can be arranged in the “sidestream” configuration. In this case, the CO.sub.2 sensor 4 is situated in the framework of the respiratory assistance apparatus 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 3, for example on the junction piece 18. This gas sampling line communicates fluidically with the lumen of the junction piece 18 in such a way as to be able to collect a sample of the gas from there and convey it then to the CO.sub.2 sensor situated in the framework of the apparatus.

(23) In all cases, the junction piece 18 comprises an internal passage for gas, allowing the gas to pass through it.

(24) Preferably, the CO.sub.2 sensor performs continuous measurements of the concentration of CO.sub.2 in the gas flowing through the junction piece 18, which gas is enriched in CO.sub.2 during its passage through the lungs of the patient P, where gaseous exchanges take place.

(25) The CO.sub.2 content measurement signals are then transmitted by the CO.sub.2 sensor to the signal-processing and control means 5 by an electrical connection or similar, in particular by wire or similar.

(26) The monitoring of the CO.sub.2 content, in particular of the etCO.sub.2 which indirectly reflects the alveolar CO.sub.2 content, is in fact of great importance during CPR, especially for detecting a resumption of spontaneous cardiac activity (RSCA). This is because a resumption of spontaneous cardiac activity (RSCA), hence a significant increase of the cardiac output, brings about a rapid increase in the quantity of CO.sub.2 carried by the blood to the lungs and transferred through the alveolar-capillary membrane, this CO.sub.2 then being found again in the gas flow exhaled by the patient.

(27) Hence, according to the present invention and as illustrated in FIG. 7, the signal-processing and control means 5, particularly the microprocessor 6, are configured:

(28) a) to process the CO.sub.2 content measurement signals corresponding to measurements performed by the CO.sub.2 content measurement means 4, typically a capnometer, during a given time period (dt), for example between 1 and 7 seconds, and to extract therefrom a plurality of CO.sub.2 content values. During the time period (dt) in question, the patient undergoes cardiac massage with a succession of chest compressions and relaxations, which causes gas to enter and leave the lungs, thus causing variations in the CO.sub.2 contents of the gas flow exhaled, that is to say leaving the lungs under the effect of the chest compressions, especially as a function of the force applied by the first responder, which is not equal from one contraction to another, as is illustrated in FIGS. 3 and 5 for example.

(29) b) to select the maximum CO.sub.2 content value (Vmax) from said plurality of CO.sub.2 content values measured during said given time period (dt). In other words, from the different CO.sub.2 contents measured during the time period dt, one selects only the highest one which is the most representative of the CO.sub.2 content, i.e. the etCO.sub.2 content, during the time period (dt) in question. To do this, the signal-processing and control means 5 store and then compare the measured CO.sub.2 values in order to retain only the highest one.

(30) c) to repeat steps a) and b) in order to obtain several successive maximum CO.sub.2 content values (Vmax) measured during a longer time window (Ft), for example between 30 seconds and 5 minutes, comprising several successive time periods (dt). In other words, the signal-processing and control means 5 perform measurements during several successive periods (dt) and select, for each of these, the maximum CO.sub.2 content value over each of the desired periods obtained during the long time window including said successive periods (dt). All of these maximum CO.sub.2 content values are stored by the storage means 11.

(31) d) to calculate at least one mean CO.sub.2 content value (Vmean) from the maximum CO.sub.2 content values (Vmax) obtained over the time window (Ft). The maximum CO.sub.2 content values (Vmax) which have been stored over the whole of the long time window (Ft) are retrieved from the storage means 11, and then a means CO.sub.2 content value is calculated from these for the time window (Ft) in question.

(32) e) to transmit said at least one mean CO.sub.2 content value (Vmean) to the GUI 7, which then displays this means CO.sub.2 content value in the form of a numerical value or a graphical representation, advantageously in the form of a graphical representation, namely a graphical symbol, for example a dot, a cross or any other symbol, which is displayed on a time graph showing the graphical representation of the mean CO.sub.2 content value (Vmean) as a function of time.

(33) f) steps a) to e) are repeated as many times as is necessary over successive time periods (dt) and over a sliding time window (Ft) of a duration of between typically 1 and 5 minutes, so as to obtain mean CO.sub.2 content values (Vmean) over the course of time, thus making it possible to monitor the development of the content of CO.sub.2 in the gas flows leaving the patient's lungs during the cardiac massage, in particular under the effect of the chest compressions. To put it another way, the GUI 7 displays, for example, a trend curve composed of a succession of graphical symbols. Of course, another graphical representation could be adopted, for example bar graphs or similar.

(34) The medical ventilator of the invention permits a measurement, advantageously a continuous measurement, of the concentration of CO.sub.2 in the gases exhaled by the patient P. The measurement is performed by the capnometer 4, which is arranged on the pathway of the gas, very close to the mouth of the patient P, preferably between the Y-shaped piece 8 and the respiratory interface 3, and the measurement signals are transmitted to the signal-processing and control means 5 via electrical lines or similar.

(35) This measurement of the concentration of CO.sub.2 in the gases exhaled by the patient P makes it possible to obtain a plurality of maximum CO.sub.2 content values which are then processed by the signal-processing and control means 5 in order to calculate mean CO.sub.2 content values from several successive maximum CO.sub.2 content values obtained over a given time window comprising several successive given time periods during which the maximum CO.sub.2 content values have been determined, preferably a sliding time window (cf. FIG. 7).

(36) The mean CO.sub.2 value (Vmean) is not necessarily updated when each point is displayed, and instead it can be refreshed and displayed after a defined duration, for example a few seconds.

(37) The reason is that, as has already been explained, the CO.sub.2 concentration value which best reflects the alveolar CO.sub.2 content, and which hence gives a good indication of the state of the blood flow in the patient P during the CPR, is the highest CO.sub.2 value, also called the maximum peak value, as illustrated in FIG. 5 which shows the development of the CO.sub.2 content and of the etCO2 measurements for given durations (dt), in the context of CPR performed on a person in cardiac arrest.

(38) More precisely, during CPR, the CO.sub.2 content in the gas exhaled by the patient, on account of the cardiac massage performed, varies depending on the presence or absence of chest compressions (CC).

(39) Thus, during the insufflation of air by the micro-blower 1 of the ventilator, then during the first compression(s) following this insufflation, no CO.sub.2 is detected in the gas flow passing through the conduit 2 as far as the Y-shaped piece 8 and then to the tracheal tube 3, which thereafter distributes this air to the lungs of the patient P. After a few chest compressions (CC) performed by a first responder, CO.sub.2 is detected at the Y-shaped piece 8 by the capnometer 4, since the alternating chest compressions (CC) and relaxations (Re) cause movements of air entering and leaving the lungs of the patient.

(40) Exhaled air rich in CO.sub.2 is then found again at the Y-shaped piece 8, and measurements of the concentrations of CO.sub.2 can be carried out by the capnometer 4. The corresponding signals are sent to the signal-processing and control means 5, where they are processed in the way explained above.

(41) The maximum CO.sub.2 content value (Vmax) determined for the given durations (dt), for example durations of 3 to 7 seconds, is the value that best represents the alveolarCO.sub.2. In fact, the CO.sub.2 present at the Y-shaped piece 8 is “washed out” little by little on account of the successive and repeated chest compressions and tends to decrease after reaching this maximum value, since the chest compressions thus cause the discharge to the atmosphere (at 9) of the gases rich in CO.sub.2, via the exhalation branch 2b of the patient circuit. The successive chest compressions thus generate different CO.sub.2 levels, the most representative being the maximum peak value, as illustrated in FIG. 5 which shows the development of the CO.sub.2 content in the gas and illustrates several measurements of the etCO.sub.2 measured over several successive durations dt, for example durations of 3 to 6 seconds, while CPR is being performed. It will be seen here that the CO.sub.2 content of the gas is not constant during a given time interval dt and that there is therefore necessarily a maximum CO.sub.2 content value (Vmax) over each interval dt, that is to say the peak value.

(42) The ventilator thus stores (at 11) all the peak values of CO.sub.2 during each time period dt, typically between 3 and 7 seconds, and determines the maximum CO.sub.2 content value (Vmax) from the plurality of peaks (EtCO2_.sub.1, EtCO2_.sub.2, EtCO2_.sub.3, . . . , EtCO2_x) measured over a given time period, as is illustrated in FIG. 5.

(43) As is illustrated in FIG. 7, these operations are repeated over several successive given time periods (dt) comprised in a longer time window (Ft), for example a time window (Ft) of 30 seconds to 5 minutes, advantageously a sliding time window (Ft), so as to be able to determine and display on the GUI 7, preferably continuously, a plurality of mean CO.sub.2 content values (Vmean) in the form of a graphical representation, preferably a trend curve over time, on which graphical symbols represent the different mean CO.sub.2 content values (Vmean) as a function of time, as is illustrated in FIG. 4.

(44) Furthermore, these maximum CO.sub.2 content values (Vmax) are processed by the signal-processing and control means 5 so as to calculate a succession of mean CO.sub.2 content values (Vmean) over a given time window comprising several successive given time periods during which said maximum CO.sub.2 content values (Vmax) have been determined, preferably a sliding time window, for example a time window of between 30 seconds and 5 minutes.

(45) The mean CO.sub.2 content values (Vmean) thus determined are displayed on the GUI 7, likewise in the form of a graphical representation such as a curve, a bar graph or similar, preferably in the form of a trend curve on which the mean values (Vmean) are represented by a succession of symbols such as dots or similar (FIG. 4). In FIG. 4, the curve « . . . . . . » represents the Vmean values and the curve « ______» represents the values of etCO.sub.2.

(46) The data calculated from this CO.sub.2, in particular the Vmean values, constitute a useful indicator for the first responder, which allows him to control the CPR, since it reflects the state of the circulation and metabolism of the patient from the moment when the patient is intubated (INT) and CPR is performed (cf. FIG. 4). Indeed, the more effective the CPR, the greater the quantity of CO.sub.2 produced and transferred through the alveolar-capillary membrane, hence the greater the quantity of CO.sub.2 that can be detected at the capnometer 4.

(47) Hence, in the case of a resumption of spontaneous cardiac activity (RSCA), the circulation recovers abruptly and therefore the quantity of alveolar CO.sub.2 increases in parallel, which induces a substantial increase in the quantity of CO.sub.2 detected by the capnometer 4 by a factor often greater than 2, as is illustrated in FIG. 4. It will in fact be seen from FIG. 4 that the etCO.sub.2 is always below 2.5 during the CPR but that it increases (INC) suddenly to reach over 5 at the moment of resumption of spontaneous cardiac activity (RSCA), i.e. after approximately 3 to 4 minutes following the intubation (INT) of the patient and the start of CPR.

(48) In the context of the invention, the fact that the GUI 7 displays a trend curved based on the mean values (Vmean) determined over a sliding time window (Ft) allows the first responder to better detect the occurrence of the spontaneous resumption of cardiac activity (SRCA) since the curve Vmean shows a strong increase (INC in FIG. 4) at the moment of a RSCA on account of increased release of CO.sub.2 in the gases exhaled by the lungs.

(49) Thus, when the first responder notes a strong rise (INC) of the curve showing the mean CO.sub.2 content values (Vmean) on the GUI 7, he can conclude from this that the patient is at the start of RSCA and, for example, can decide to analyse the heart rate and, if appropriate, stop the cardiac massage.

(50) The ventilator additionally permits parallel performance of a continuous measurement of the exhaled and inhaled gas flow rates, with the aid of a flow rate sensor (not shown).

(51) Advantageously, the ventilator of the invention can also include alarm means designed and programmed to warn the first responder or the like when one or more of the measured maximum CO.sub.2 content values exceeds or, conversely, drops below a given value that is predefined or calculated continuously.

(52) In particular, an acoustic and/or visual alarm is provided which triggers when the maximum CO.sub.2 content measured, at a time t, is greater than a threshold value, for example: [VmaxCO.sub.2]>1.5×[MeanCO.sub.2] where: [VmaxCO.sub.2] is the maximum CO.sub.2 content value measured during a given duration dt, for example over a duration dt of between 2 and 10 seconds, [MeanCO.sub.2] is the mean value of the maximum CO.sub.2 content values [VmaxCO.sub.2] determined for several successive durations dt in a given time window (FT) (FT>x.dt with x≥2:2), for example a period of 30 seconds to 5 minutes, or more.

(53) Similarly, the alarm can trigger in the event of the CO.sub.2 concentration dropping abruptly below a given minimum value, which could be the sign of a new cardiac arrest of the patient, of hyperventilation, or of obstruction of the gas circuit between the patient and the machine, for example a flexible conduit that is bent or crushed and no longer allows the gas to pass through.

(54) A source 10 of electric current, such as a rechargeable battery or similar, integrated in the framework of the ventilator, directly or indirectly supplies electric current to the signal-processing and control means 5, the micro-blower 1, the GUI 1 or any other element of the apparatus, in particular a storage memory 11.

(55) Generally, the invention relates to a medical ventilator suitable for use during cardiopulmonary resuscitation (CPR), comprising a source 1 of respiratory gas, such as a micro-blower, means for measuring the CO.sub.2 4, such as a capnometer, signal-processing and control means 5 receiving and processing the CO.sub.2 content measurement signals originating from the CO.sub.2 measurement means 4, in order to obtain successive maximum CO.sub.2 content values (Vmax) measured over a time window (Ft) and to calculate at least one mean CO.sub.2 content value (Vmean) from the maximum CO.sub.2 content values (Vmax) obtained over the time window (Ft), and a GUI 7 configured to display said at least one mean CO.sub.2 content value (Vmean).

(56) The respiratory assistance apparatus or medical ventilator 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 aid 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.

(57) It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.