Patent Application
20130087145
This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in International Patent Application No. PCT/EP2010/068556 filed on Nov. 30, 2010 and German Patent Application No. 10 2010 016 699.5 filed Apr. 29, 2010.
The invention relates to a method and a device for administering at least one medical gas to a mechanically ventilated patient. A machine ventilator produces a constant respiratory gas flow in at least a portion of a line supplying respiratory gas. This constant respiratory gas flow is produced independent of the respiratory sequence of the patient. A predetermined amount of a medical gas to be administered is added to the constant respiratory gas flow. The gas mixture provided by the respiratory gas flow of the ventilator and the medical gas added to this flow are supplied to a connecting piece, such as a so-called Y-piece from which a patient feed line leads to the mechanically ventilated patient and from which a further line branches off. Via this further line at least the gas exhaled by the patient and the proportion of the respiratory gas introduced into the first line by the ventilator and the medical gas fed into the first line which have not been inhaled by the patient are discharged via a second line.
Documents EP 0 937 479 B1, EP 0 937 479 B1, U.S. Pat. No. 5,558,083, EP 0 786 264 B1, EP 1 516 639 B1, and EP 0 723 466 B1 disclose devices and methods for delivering nitrogen monoxide in a continuous and pulsed manner over the course of time to a mechanically ventilated patient. Control valves for setting the amount of nitrogen monoxide are provided, which valves, however, as a function of the design in each case, allow a defined amount of gas to pass through per unit time under specific, defined pressure conditions. Therefore, there is reliance on providing the medical gas in a combination appropriate for the device and on providing the patient with an amount of gas appropriate for the treatment in the opened state of the regulating means. However, it is desirable to wean the mechanically ventilated patient, if necessary, from the active ingredients of the medical gas in a continuous or stepwise manner and to reduce the amount of the administered medical gas per unit time. In the case of high, gas source-provided concentrations of the medical gas and in the case of a very low amount of gas to be supplied, a precise metering of low amounts of gas is therefore necessary, whereas in the case of gas sources having a low concentration of the medical gas and administration of relatively large amounts of the medical gas by means of the regulating means, substantially larger amounts of gas have to be introduced into the first line.
It is an object of the invention to specify a method and a device for administering at least one medical gas to a patient mechanically ventilated by means of a ventilator, in which method and device the amount of gas to be administered is easily adjustable.
This object is achieved by a method having the features of claim 1 and by a device having the features of the independent device claim. Advantageous developments of the invention are specified in the dependent claims.
What is achieved by the method and the device for administering at least one medical gas to a patient mechanically ventilated by means of a ventilator is that, via each of the two regulating means arranged in parallel, the medical gas can be introduced into the ventilator-produced constant respiratory gas flow in the first line and can thus be supplied to the patient. By opening one of the regulating means or both regulating means to produce the gas pulses, it is possible to set the amount, more particularly the volume, of the medical gas introduced into the first line with an appropriate selection of the pulse length and pulse repetition. In this case, a constant pulse frequency is preset. By this, it is achieved that the respiratory gas supplied to the patient represents a constant proportion of the medical gas.
By appropriately selecting the dimensions of the regulating means, gas sources containing different concentrations of the medical gas can thus also be used, without requiring structural modifications of the device for administering the medical gas. Thus, both the method and the device provide variable adjustment of the amount of gas to be administered in large adjustment ranges and thus a broad concentration spectrum. The pulse-shaped partial pressure brought about by the gas pulses is measurable into the airways of the mechanically ventilated patient.
In an advantageous embodiment the respiration frequency is the number of breaths of the patient within a certain unit of time. A pulse frequency indicates the number of the gas pulses of the pulse sequence within the same time unit. The regulating means are controlled by means of the control unit such that the pulse frequency is higher than the respiratory frequency. Thus, a relatively constant distribution of the medical gas in the respiratory air fed to the patient is achieve, even if a part of the constant respiratory gas flow together with the added medical gas is not fed to the patient, but is discharged via the second line together the gas exhaled by the patient.
It is especially advantageous if the pulse frequency of the gas pulses is 26, 52, 104 or 208 pulses per minute. In case of such pulse sequences it could be observed that the periodic noise generation by the device was tolerated especially well by the patient and that the patient showed a good reaction to the application of the medical gas. As already mentioned, the gas injection effected by the gas pulses leads very quickly to a homogeneous partial pressure situation.
Further, it is advantageous when the regulating means are controlled by means of a or the control unit such that an amount of gas defined in relation to a gas pulse and/or gas volume defined in relation to a gas pulse is fed into the first line. As a result, the amount of gas or the gas volume that is required for the administration can be introduced into the first line in a simple manner.
It is particularly advantageous when the medical gas contains NO (nitrogen monoxide). The medical gas can in particular be provided as a gas mixture composed of NO (nitrogen monoxide) and N2 (nitrogen). A gas mixture composed of NO (nitrogen monoxide) and He (helium) has also been found to be particularly advantageous, since especially helium can achieve particularly short reaction and response times. As a result, effective administration is possible especially in the case of newborn babies and in the case of premature babies and the relatively low amounts of the mixture composed of respiratory gas and medical gas that are inhaled by these patients.
It is further advantageous to have more than two regulating means arranged in parallel. Experiments have shown that it is particularly advantageous to have four regulating means arranged in parallel, wherein the regulating means are formed such that at least two of the regulating means in the opened state allow a different amount of gas to pass through. The regulating means arranged in parallel are preferably valves and are then also referred to as a valve bank. In this connection, it has been found to be particularly advantageous when, under the defined pressure conditions, the first valve has a flow of 0.16 liters per minute, valve 2 has a flow of 1.6 liters per minute and valves 3 and 4 each have a flow of 8 liters per minute when opened constantly (measured using medical air). It is further advantageous when regulating means are used which have a shortest realizable opening time of milliseconds, preferably in the range from 4 milliseconds to 7 milliseconds. The control unit can open the valves individually or in any desired combination, and so, in the case of the specific exemplary embodiments, a maximum flow of 17.76 liters per minute is possible.
It is particularly advantageous when a control unit optimizes the opening of the regulating means to the effect that a very long opening time is achieved within one cycle time of for example 104 gas pulses per minute. As a result, a constant as well as homogeneous injection of the medical gas into the respiratory air supplied to the patient is achieved. Also achieved as a result is a large adjustable metering range of the medical gas to be administered to the patient.
In one embodiment, 26×18.60 microliters of the medical gas are administered when only one valve having a flow of 0.16 liters per minute, 7 milliseconds opening time per gas pulse and a pulse frequency of 26 pulses per minute theoretically, is opened. However, owing to the required valve stroke and/or the response delay, 26×13 microliters are administered in practical experiments using these parameters. Even in the case of a premature baby, which has a tidal volume of 2.4 litres per minute, it is possible as a result to set a low concentration of 0.1 ppm with a starting concentration of the medical gas of 1000 ppm. As a result, after a more highly concentrated administration of the medical gas, it can be reduced in a stepwise or continuous manner to approximately 338 microliters per minute, and weaning of the patient from the medical gas or from the active ingredient thereof is therefore easily possible. Furthermore, the use of multiple regulating means connected in parallel makes it possible, at the administered concentrations, i.e., target concentrations, which are currently conventional, to also use more highly concentrated supply gas sources, with the result that said supply gas sources, more particularly supply gas cylinders, have to be exchanged at greater intervals, and as a result logistics and consumption costs can be lowered. Alternatively or additionally, the invention makes a larger therapeutic concentration spectrum clinically available.
As already mentioned, it is advantageous when the regulating means in an opened state allow volume flows differing face to face to pass through from the gas source to the first line. In the case of more than two regulating means, it is advantageous when at least two of the regulating means in the opened state allow different volume flows to pass through from the gas source to the first line. As a result, a concentration from a relatively large concentration spectrum can be set in a simple manner.
It is particularly advantageous when the regulating means each comprise at least one solenoid valve. Furthermore, a restricting orifice or another restricting means for limiting the volume flow flowing through the regulating means can be arranged upstream and/or downstream of at least one regulating means. Solenoid valves are, firstly, inexpensive and, secondly, solenoid valves have relatively short response times. The solenoid valves are controlled in particular in a binary manner, and so they are completely closed in a first operating state and completely opened in a second operating state. By means of the restricting means for limiting the volume flow flowing through the regulating means, it is possible to use regulating means of the same type, more particularly solenoid valves of the same type, wherein the volume flow flowing through the regulating means in the opened state differs owing to the provision of different flow resistances. As a result, it is easily possible to produce different volume flows through the regulating means.
In an advantageous development of the invention, gas is removed from the patient feed line. At least the proportion of the medical gas and/or the proportion of a reaction product of the medical gas in the removed gas is determined. The gas can be removed from the patient feed line via a measurement line and supplied to an analysis unit for the detection of at least the proportion of the medical gas and/or the proportion of a reaction product of the medical gas. More particularly, the removal and detection can be carried out once or more than once during one act of inhalation, preferably repeatedly during each act of inhalation. As a result, the concentration of the medical gas in the inhalation air can be easily determined, monitored and/or regulated. The inner diameter of the measurement line is preferably smaller than the diameter of the first line, the second line and the patient feed line.
It is further advantageous to compare the determined proportion of the medical gas, as the actual value, with a target value and, in the event of a determined deviation of the actual value from the preset target value, to adapt the amount of the medical gas introduced into the first line during each gas pulse as a function of the comparative result. Preferably, the proportion of the medical gas in the inhalation gas is regulated to the preset target value. As a result, the amount of the medical gas to be administered to the patient can be easily monitored, and/or kept constant. If, in addition to or as an alternative to the proportion of the medical gas, the proportion of a reaction product of the medical gas is analyzed, it is advantageous to determine the proportion of an oxidation product of the medical gas. If nitrogen monoxide (NO) is used as medical gas, the proportion of the oxidation product nitrogen dioxide (NO2) can be determined in particular. The proportion of the determined nitrogen dioxide can then be compared with a permissible target value. When the target value is exceeded, the feeding of the medical gas into the first line can then be stopped or the volume of the fed medical gas can be reduced. In the event of an excessively high concentration of nitrogen dioxide in the mechanical ventilation gas, the patient can be harmed, and so this must be avoided.
It is further advantageous when the ventilator determines information concerning a flow profile of the respiration of the mechanically ventilated patient. Depending on the determined flow profile the control unit can then control the regulating means such that during the inhalation phases of the patient during each generated gas pulse they apply a larger amount of the medical gas into the first line and/or supply the gas pulses with a higher pulse frequency into the first line than is the case during the exhalation phases of the patient.
In an escecially preferred embodiment the same pulse frequence is used during the inhalation phase and during the respiration phase. Preferably, the pulse frequency is preset to 104 gas pulses per minute. Alternatively, during the inhalation phase the pulse frequency can be higher than during the exhalation phase. In case of an increased pulse frequency the volume supplied with each gas pulse can equal or be higher than the gas volume of the gas pulses during the exhalation phase.
The solenoid valves used are preferably valves switchable between a completely closed and a completely opened position, which valves are controlled in a binary manner.
The invention can be used especially in neonatology for treating pulmonary hypertension of a premature baby with nitrogen monoxide. Nitrogen monoxide is also administered in order to treat patients after organ transplantations. However, the invention can also be used for administering other gaseous medicaments.
Depending on the clinical use, up to 10% of the inspired volume can originate from a gas source for providing gaseous medicaments. Such a gas source is also referred to as an additive gas source, since it is provided in addition to a respiratory gas source or oxygen source. The invention avoids the disadvantage in the prior art that a delay time arises from the time of measuring the flow velocity of the respiratory gas used for the inspiration of the patient up to the mechanical adjustment of a control valve used for feeding the medical gas, and that there is an occurrence of relatively large concentration fluctuations of the administered medical gas in the mechanically ventilated air provided to the patient with dynamic flow profiles. Furthermore, in the case of known control valves, the control range of the conducted medical gas is limited relatively strongly. In the case of valves which allow a large flow of the medical gas, low flow rates can only be set relatively imprecisely. In a further embodiment of the invention, discontinuous feeding by means of multiple gas pulses into the respiratory air of the ventilator patient circuit comprising the first line, the second line and the patient feed line can be carried out.
Further features and advantages of the invention are found in the following description, which more particularly elucidates the invention by means of exemplary embodiments in conjunction with the attached figures.
The following is shown:
The ventilator 12 produces a constant flow of respiratory gas in the respiratory air tube 24. The medical gas mixture NO/N2 determined for the treatment of the patient is supplied to this constant respiratory gas flow via the connecting line 40 by means of the metering device 20. For this purpose, the metering device 20 produces continuously gas pulses with a pulse frequency which is at least independent fromthe respiratory rate of the patient.
In addition, a measurement line 41 is connected to the patient feed line 30 and conducts at least some of the gas mixture situated in the patient feed line 30 to the connector A of the metering device 20. The gas mixture supplied to the metering device 20 via the connector A is analyzed by a measurement/evaluation unit 44 of the metering device 20.
The metering device 20 has a third module 52, which, in the present exemplary embodiment, comprises four solenoid valves 54 to 60, which are each supplied with the medical gas mixture NO/NO2 via the connector C. Upstream of the solenoid valves 54, 56 is, in each case, a metering orifice 62, 64 for restricting the flow through the respective solenoid valve 54, 56. The output sides of the solenoid valves 54 to 60 are connected to the connector B, and so the solenoid valves 54 to 60 are connected in parallel. The control unit 48 of the metering device 20 can individually control the solenoid valves 54 to 60, i.e., open them individually or in combination. Thus, it is possible to achieve a gas flow between the connector C and the connector B by opening a valve 54 to 60 and to thus feed medical gas NO via the connecting line 40 into the respiratory gas line 24. The amount of flow between the connector C and the connector B can be increased by the simultaneous opening of multiple valves 54 to 60. In addition, the administered amount, i.e., the amount of the medical gas NO fed into the respiratory gas line 24, can be set by appropriate selection of the pulse duration and/or by appropriate selection of the pulse frequency. In this connection, the gas pulses produced by the individual valves 54 to 60 can have a different pulse duration with preferably the same pulse frequency. The third module containing the parallel arrangement of multiple valves 54 to 60 is also referred to as valve bank 52. The valve bank 52 containing the four solenoid valves 54 to 60 allows a large adjustable metering range and flexible adaptation of the amount of gas to be administered when using gas sources 16 having different starting concentrations of the medical gas. The starting concentration is preferably preset as a parameter via the operating unit 50 and taken into consideration when calculating the pulse duration and pulse frequency for producing the amount to be administered.
In the present exemplary embodiment, the solenoid valve 54 has a flow of 0.16 liters per minute, the solenoid valve 56 has a flow of 1.6 liters per minute and the solenoid valves 58 and 60 each have a flow of 8 liters per minute, measured using medical air. The pulse frequency, i.e. the clock rate, amounts to 104 gas pulses per minute, i.e. 104 bolups per minute. If smaller quantities of the medical gas NO shall be administered or for other reasons a lower clock rate and/or a lower pulse frequency shall be selected, said pulse frequency is preferably reduced to 52 gas pulses per minute or 26 gas pulses per minute. If a higher pulse frequency shall be selected, said pulse frequency can also be increased to 208 gas pulses per minute.
By means of the arrangement shown in
To wean the patient, the dose is lowered in a stepwise or continuous manner to 0.5 ppm; in the case of premature babies, to 0.1 ppm. The starting concentration of the medical gas in the gas source 26 is preferably 1000 ppm. All doses indicated refer to the respiratory air supplied to the Y-piece 26 and containing the introduced medical gas.
In general, the use of a valve bank 52 containing multiple valves 54 to 60 arranged in parallel makes it possible, in the case of currently conventional administered amounts, to use gas sources 16 containing higher starting concentrations of the medical gas, more particularly up to 2000 ppm or up to 4000 ppm. Compared to gas sources containing 1000 ppm of the same amount of gas, the service lives are doubled when the starting concentration is doubled. Alternatively or additionally, the use of the valve bank 52 provides a larger therapeutic concentration spectrum. In the present exemplary embodiment, the minimum opening duration of the solenoid valves 54 to 60 is 7 milliseconds. As a result, the amount of the medical gas NO fed into the respiratory gas line 24 can be varied in large ranges, resulting in a large adjustable therapeutic concentration spectrum.
It was found in experiments that the use of a gas mixture (NO/He) composed of nitrogen monoxide and helium, compared with the gas mixture (NO/N2) used in the first exemplary embodiment according to
The second, lower graph shows the gas pulses fed into the respiratory air feed line 24 by means of the metering device 20 as volume flow of the relevant proportion of the medical gas NO. Supplying the medical gas in this exemplary embodiment is achieved by means of gas pulses having a constant pulse frequency and thus independently of the respiratory rate of the patient 14.
The solenoid valves used are preferably valves switchable between a completely closed and a completely opened position, which valves are controlled in a binary manner.
The invention can be used especially in neonatology for treating pulmonary hypertension of a premature baby with nitrogen monoxide. Nitrogen monoxide is also administered in order to treat patients after organ transplantations. However, the devices 10, 100 described in the exemplary embodiments can also be used for administering other gaseous medicaments.
It is further known to mix gaseous medicaments into a respiratory gas flow by means of a proportioning valve as a function of the flow velocity, measured in real-time by means of a flow meter, of the respiratory air flow.
There is a data and/or signal cable 202 between the ventilator 12 and the metering device 20, via which information concerning a real-time flow profile of the respiration of the mechanically ventilated patient 14 transmits by means of signals and/or data to the control unit 48 of the metering device 20. For the data transmission, it is possible to use in particular a real-time-capable bus system, for example a CAN BUS or a serial interface, such as a USB interface or RS232 interface, using a real-time-capable data transmission protocol.
The medical gas is fed into the respiratory air feed line 24 such that, during the respiratory phases of the patient, a higher concentration of the medical gas is contained in the supplied ventilation air. In a first embodiment of the third exemplary embodiment, the gas pulses are delivered at a constant pulse frequency, wherein the amount of gas delivered per gas pulse is greater during the inhalation phases than during apnea phases and during the exhalation phases of the patient 14.
Alternatively or additionally, it is possible in further embodiments for the pulse frequency to be higher during the inhalation phases than during the exhalation phases and during apnea. In addition, it is possible during apnea of the patient 14 for the supplying of the medical gas by the metering device 20 to be interrupted. It is advantageous that by means of gas-pulse and pulse-frequency optimization performed by the control unit 44 or a control unit of the ventilator 12 a relatively long opening time of the activated valves 54 to 60 is required within the defined pulse frequency. The pulse frequency is preferably 104 gas pulses per minute. Only when the required gas flow of the medical gas through the valve bank 52 is greater than or equal to the maximum flow through a valve 54 to 60, and so the flow through said valve 54 to 60 would not be sufficient to administer the required amount of the medical gas, or the valve 54 to 60 would no longer close and would thus produce no more gas pulses, is an additional further valve 54 to 60 or, instead of the first valve 54 to 60, a second valve 54 to 60 having a larger flow in the opened state controlled by the control unit 48.
In a fourth exemplary embodiment, in contrast to the exemplary embodiment shown in
In other exemplary embodiments, the amount of gas administered in one gas pulse can be further varied in that the individual pulse widths, with which the valves 54 to 60 for producing a gas pulse are controlled, are different, and so at least two valves 54 to 60 deliver gas pulses of different pulse width. As a result, a total gas pulse is produced which has been produced from two subpulses of different pulse width. The total gas pulse then has a stepped course, which is fed into the respiratory gas feed line 24. In a specific embodiment of the third and fourth exemplary embodiment, the pulse frequencies during the inhalation phases are twice as high as in the exhalation phase. For example, the pulse frequency can be 208 gas pulses per minute during the inhalation phase and 104 gas pulses per minute during the exhalation phase. Alternatively, the pulse frequency can be 104 gas pulses per minute during the inhalation phase and 52 gas pulses per minute during the exhalation phase. Depending on the rise in the amount of gas inhaled at the start of an act of inhalation by the patient 14, i.e., depending on the flow at the start of the act of inhalation and/or the temporal course of the respiratory gas flow, it is possible for the length of an inhalation of the patient 14 and/or the course of the inhalation of the patient 14 to be empirically determined and, in line with the estimated course for each gas pulse during an inhalation, for an amount of the medical gas to be fed into the respiratory gas feed line 24 by this gas pulse to be defined. The defined amount of gas is then fed into the respiratory gas feed line 24 by appropriate control of the solenoid valves 54 to 60.
In an alternative embodiment of the invention, a closed circuit system is formed, and so the gas mixture exhaled by the patient 14 remains in the closed circuit system. Thus, the medical gas not taken up by the patient also remains in the circuit system. Such closed circuits are used especially during anesthesia of the patient 14. During anesthesia, the patient 14 is connected to an anesthesia machine. The control unit 48 is connected to the anesthesia machine via an interface. The anesthesia machine comprises at least one sensor for determining the start of a breath of the patient 14 and a sensor for determining the volume of gas mixture inhaled in said breath. The anesthesia machine transmits, via the interface, data containing information concerning the start of the breath and the inhaled volume of gas mixture to the control unit 48, which, as a function of said data, determines the amount of the medical gas injecting via the valves 54 to 60 such that as much medical gas is injected for it to be completely or at least almost completely taken up by the patient 14 in the breath, and so no accumulation of the medical gas occurs in the gas mixture of the closed circuit system. The control unit 48 controls the solenoid valves 54 to 60 in particular such that the amount of medical gas to be injected is injected within a short time at the start of the breath. Thus, an accumulation of the medical gas in the gas mixture is avoided and, as a result, reactions with other substances in the closed circuit system are, for example, avoided.
In a further alternative embodiment of the invention, the medical gas is taken up in a carrier gas, more particularly helium. This reduces time delays in the transport of the medical gas through the lines, and so a precise control of the inspiration times is possible. This is necessary especially in the treatment of infants, since, during their treatment, even delays of 100 ms in the inspiration times may be critical with respect to the success or failure of the therapy. The ventilator 12 comprises a sensor for calculating the gas volume of a breath of the patient 14 and a sensor for determining the temporal start of a breath. The ventilator 12 is connected to the metering device 20 via a data interface, wherein data containing information concerning the volume of the last breath of the patient 14 and data containing information concerning the times of at least the last two breaths of the patient 14 are transmitted via the interface. The control unit 48 determines in real-time, as a function of these data, the start of the next breath of the patient 14 and controls, as a function of the calculated start of the breath and of at least the gas volume of the last breath, the solenoid valves 54 to 60 such that the injecting amount of medical gas is injected in a burst at the start of the next breath. Injection in a burst is understood to mean in particular that the medical gas is injected within a very short time. For this purpose, the control unit 48 opens the solenoid valves 54 to 60 as far as possible at the start of the breath.
Although the invention above has been described in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 016 699.5 | Apr 2010 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP10/68556 | 11/30/2010 | WO | 00 | 12/21/2012 |
