HK1117432A - Manpower respirator for treating obstructive sleep apnea and method for its control - Google Patents

Description

Artificial respirator for treating obstructive sleep apnea and control method thereof

Technical Field

The invention relates to a ventilator for treating patients with obstructive sleep apnea and a method for controlling the same having the features of the preamble of claim 1.

Background

An artificial ventilator for the treatment of obstructive sleep apnea generates artificial air which has a higher pressure than natural air and is delivered to a patient to be treated through a breathing hose and a mask during sleep.

Muscle contraction is weakened during sleep, the soft tissue of the laryngeal airway may be depressed, and the sleeper is in danger of asphyxia. The resultant cessation of breathing is known as obstructive sleep apnea. The cause of the collapse of the soft airways is the pressure drop therein, which is caused by the high velocity of the respiratory airflow. As a result, the airway can no longer withstand the pressure differential with the ambient normal atmospheric pressure in the base of the tongue and in the region of the soft palate. They press against each other and close the air flow channel. Further applied pulmonary suction enhances this closure, so that the patient may not inhale air for a long period of tens of seconds. This process can occur hundreds of times each night while sleeping. The long term consequences are a reduced quality of life, heart-circulatory diseases and a reduced general life expectancy.

When a patient suffering from obstructive sleep apnea breathes artificial air, the pressure of the artificial air in the larynx is at least higher than the natural ambient atmospheric pressure by the pressure drop required for flow, so that the soft tissue of the larynx can no longer be depressed. The patient is heavy and can absorb it freely and spontaneously, and the number of sleep apnea is reduced to the level of a healthy person. For this purpose, artificial air is generated by an artificial respirator and fed to the patient via a breathing hose and a breathing mask.

Artificial ventilators that produce artificial air with a constant treatment pressure at all times are known as CPAP (continuous positive airway pressure) devices.

The air flow in the respiratory tract of a patient does not proceed without resistance. The drag components of laminar and turbulent flow distributed over the length act as a barrier. The resistance components are the nasal tract resistance, the resistance of the soft-walled airways in the throat, and the resistance of the bronchi. The magnitude of the turbulent flow resistance is related to the flow strength.

The patient's airway resistance and the device's flow resistance are in series. The internal resistance of the plant may be influenced by the respective plant controller. A smaller burden of the respiratory muscles is achieved when the flow resistance of the device is realized to be negative and thus acts against the positive airway resistance of the patient. Negative resistance has an opposite pressure-flow relationship. In relation to the flow resistance within the CPAP device, the device should generate a higher pressure if an air flow is applied in the direction of the patient; if the patient exhales air in the direction of the device, the device should produce a lower pressure.

CPAP devices that produce a higher therapeutic pressure during inhalation and a lower therapeutic pressure during exhalation are known as two-stage devices (e.g., the device known by RESPIRONICS under the name bipak ®). In order to determine the transition from inspiration to expiration and vice versa, the device has a processor, which is called a breath starter. Two-stage devices are always applied when the patient already has a generally elevated airway resistance due to other illnesses, or when the treatment with the CPAP device is only effective with very high treatment pressures.

The pressure control of the two-stage device is comparable to that of a ventilator for artificial respiration. The disadvantage is that only two pressure levels exist, which are predefined independently of the respective depth of respiration and cannot be adapted to the depth of respiration. The pressure transition caused by the breathing trigger results in a rectangular artificial respiration pressure profile and thus does not compensate optimally for the airway resistance. The transition from the lower to the higher pressure level results in a short artificial breath, when air is forced into the lungs. The transition from a high to a low pressure level may cause a constriction of the small respiratory tract due to the initially high expiratory flow, even preventing expiration. This phenomenon is uncomfortable for the patient and can be alleviated by: the transition from one pressure level to another is not a strict rectangular curve, but rather a gradual transition.

The comfort of use of the two-stage device is decisively influenced by the correct functioning of the breath starter. At the very end of the expiration phase, when the respiratory gas flow is almost absent, air flutter also occurs, because the heart beat rhythmically influences the compressed lung volume and the resulting air flow. The breath starter cannot accurately recognize the end of one exhalation, and the patient has the feeling that: pressure switching is often performed at the wrong moment.

Disclosure of Invention

It is therefore an object of the present invention to provide a ventilator for the treatment of sleep apnea which, when applied, significantly reduces the burden on the patient's respiratory muscles, makes the treatment more comfortable and may reduce the consequences of treatment lag. In another aspect the invention provides a method for controlling such an apparatus.

This task is achieved by a breathing apparatus having the features of claim 1. Advantageous developments of such a respirator are given in the dependent claims 2 to 5.

A further solution to this object is a method for controlling such a respirator as claimed in claim 6, advantageous improvements of which are given in claims 7 and 8.

The respirator according to the invention comprises a pressure generator which can provide any pressure up to a freely selectable limit and is controlled by a pressure regulating device. A ventilator generates artificial air with the pressure generator, for example a blower, which is fed to the patient by means of a breathing hose and a breathing mask.

According to the invention, the controller contained in the ventilator, which in an advantageous development may be a servo processor (see claim 3), determines the pressure loss over the airway resistance and matches the treatment pressure change substantially proportionally to the determined pressure loss change.

In an advantageous development, the controller is configured to calculate the pressure loss over the airway resistance from the respiratory airflow of the patient and the magnitude of the airway resistance. For this purpose, the artificial respirator has a device for determining the respiratory gas flow. The respiratory resistance of the patient can be determined externally and communicated to the ventilator in the form of input data, or, as an advantageous improvement according to claim 4, this resistance can be measured continuously or intermittently automatically by means of a measuring device integrated in the ventilator.

As an advantageous improvement, a continuous or intermittent measurement of the airway resistance can be carried out, for example, with the aid of a standard pressure or flow signal. In this way, changes in the airway resistance are always taken into account immediately when controlling the artificial respirator according to the invention. Since the feeding of air from a ventilator is usually done by a nasal mask and there is a considerable variation in the flow resistance of the nose, a continuous measurement of the respiratory resistance is particularly an approach to compensate for different size obstacles of the nose breathing.

A further advantageous embodiment of the respirator according to the invention is the combination of the novel features with the mode of operation of a device which operates according to the automatic regulation principle (Auto-CPAP) for determining the optimum base pressure, which has been known for a long time and is described, for example, in EP 0705615a1 (see claim 4). A ventilator according to the invention, which uses such a combined assembly, automatically determines the effective base pressure, which may also vary depending on the patient's anatomy.

If the advantageous embodiment described above is not used, not only the base pressure but also the airway resistance can be determined by external means and fixedly fed into the ventilator according to the invention.

The effect to be achieved with the ventilator according to the invention is the effect of an inspiratory amplifier which supports inspiratory action with a matched pressure rise and expiratory action with a matched pressure drop. This effect can be compared with the effect of a steering force booster or a brake force booster of a motor vehicle.

Comfortable breathing is obtained by: not only the pressure rise during inspiration but also the pressure drop during expiration proceeds approximately in proportion to the pressure loss in the breathing resistance. For this purpose, with the known respiratory resistance, the pressure loss is calculated as the product of the respiratory resistance and a fraction of the square of the respiratory airflow, since the turbulent resistance increases linearly with the flow rate. The proportion of the above-mentioned portion is determined by the degree of amplification of the respiratory force.

It is also advantageous to match different sleep states, which are known to be distinguished by different breathing parameters, such as breathing frequency and breathing volume. In this way, the involvement of a ventilator is avoided when the breathing intensity is low, by the difference between the maximum inhalation pressure and the minimum exhalation pressure being automatically reduced. Conversely, in the case of a large breathing intensity, the difference between the maximum inhalation pressure and the minimum exhalation pressure increases accordingly.

Furthermore, it can be determined by means of the control unit from the predefined intensity whether the ventilator compensates for the entire pressure loss in the airway resistance or for a part thereof (see claim 6). For this purpose, the output signal of the control unit is added to a predetermined base pressure signal and fed as a main variable to the pressure regulating device (see claim 7).

Drawings

The invention is explained in more detail below with the aid of an exemplary embodiment. In the drawings:

fig. 1 shows a block diagram of an embodiment of a breathing apparatus according to the invention, an

FIG. 2 for determining the treatment pressure p_actThe differently scaled portions of the pressure loss Δ p under consideration illustrate the flow of breathing air *_vPressure loss Δ p, treatment pressure p_actAnd the pressure p in the lung_LThe signal profile of (2).

Detailed Description

Fig. 1 shows a block diagram illustrating a possible implementation of a breathing apparatus 1 according to the invention.

In order to generate the pressure, a pressure generator 3, here in the form of a blower, and an oscillating pump 4, which generates oscillating pressure changes with small amplitudes, are provided in the respirator. The two pressures are added at an addition point 5 to obtain a sum pressure, and the sum pressure is passed throughIndividual flow resistance R_iAnd a breathing hose 6 leading to a breathing mask 7. Thus, in the flow resistance R_iTo form a ventilator air flow *_DRelated to the pressure drop. Flow processor 8 is powered by ventilator airflow *_DDetermines the flow of breathing gas *_VWhich leads to the lungs of the patient 2. This is done by calculating the leakage airflow *_LAnd is derived from ventilator airflow *_DIs subtracted from the process of variation. The leakage air flow being through a blow-off valve R_L(which is typically only one opening to the exterior), as well as airflow through other parasitic vents, and even through non-sealing portions of the mask.

Therapeutic pressure p_actIs measured in a breathing mask 7 (which is typically only a nasal mask). The pressure measured from the mask is sent to a pressure processor 9 which provides two output signals. The signal at the output a represents the actual constant pressure component and is fed as the actual pressure to the pressure regulating device 10. The device compares the actual pressure with a setpoint pressure provided by the adder 11, which setpoint pressure comprises a predefined base pressure p of the respirator 1_oAs its components. The difference between the nominal pressure and the actual pressure regulates the magnitude of the pressure generated by the pressure generator 3 in such a way that as far as possible no residual regulating deviations occur.

Another signal on the output B of the pressure processor 9 represents the alternating pressure in the breathing mask 7. This pressure is generated by the oscillating pump 4. However, the amplitude is proportional to the magnitude of all the resistances present, the flow resistance R_iRespiratory resistance R of patient 2_AWAnd the flow resistance R of the discharge opening_LIt is related. For a better understanding, the patient's compliance C and the breathing pump P are shown, which however do not contribute to the functioning of the breathing apparatus 1 according to the invention.

Flow resistance R_iAnd the flow resistance R of the discharge opening_LIs known so that the pressure processor can calculate the respiratory resistance R_AWTo which it is directedA measure of the amount of resistance.

The measurement results are transmitted via the changeover switch 12 to the servo processor 13, which takes account of the determined respiratory gas flow *_VCalculating respiratory tract resistance R_AWAnd a predetermined intensity int, and that the respiratory resistance R to be compensated for by the ventilator 1 is determined_AWAgain only a fraction of this is compensated for by the total pressure loss deltap.

By operating the switch 12, the resistance input of the servo processor 13 can be switched to the manually input resistance value R_AWXThe above. In this operating mode, an externally determined airway resistance can be fixedly predefined, which may be of interest for certain applications.

Output signal of servo processor 13 and predetermined base pressure p_oThe target treatment pressure p for processing by the pressure control device 10 is obtained by adding the pressure values by means of an adder 11_act。

Fig. 2 shows the operation of the respirator 1 according to the invention in signal relationship. To facilitate identification of the process, the process is simplified and considered as a sinusoidal excitation.

Once the patient 2 has been instructed by the breathing pump P about the inspiration and expiration phases, the lung volume (fit) C is passed through the flow of breathing air *_VIs inflated and deflated. This flow of breathing gas *_LResistance to flow through the respiratory tract R_AWOn which a part of the treatment pressure P is consumed_act. There is no linear relationship between pressure consumption Δ p and airflow, but rather an approximately squared relationship. As can be seen, the time profile of the pressure consumption Δ p is therefore no longer sinusoidal.

When the artificial respirator is adopted, the treatment pressure P is_actA part of the amount of pressure loss is continuously changed.

When the fraction is zero (left diagram in the figure), the treatment pressure P_actNo change in time occurred. By inhalation and respirationThe resulting periodically fluctuating pressure loss Δ P changes in this case completely reflect the intrapulmonary pressure P_L. For the user of a respirator, this means that the respiratory resistance R is based on_AMWithout exception, the respiratory disorder of (a) must be overcome by its respiratory muscles.

As the proportion of this portion increases (the middle graph (proportion 0.5) and the right graph (proportion 1) in the graph), the change in the periodically fluctuating pressure loss Δ P caused by inhalation and exhalation is increasingly shifted to the treatment pressure P_actOn the fluctuation of (c). As a result, the pressure in the lung P_LThe fluctuations of (a) are reduced to the same extent. For the user, this means that his breathing effort becomes smaller. To overcome respiratory resistance R_AWThe required breathing effort is taken over by the pressure generator in increasing proportion. Has higher respiratory tract resistance R_AWThe user of (2) does not need to have a great deal of respiratory muscle power for the normal inhalation or exhalation process. The user can achieve the same ventilation intensity with a very small intra-pulmonary suction or pressure.

To find respiratory resistance R_AWFor example, an oscillating respiratory resistance measurement method may be used.

Another possibility is that the respiratory tract resistance is determined by an external measurement method and the measured value or a further determined value is input into the artificial respirator.

Using the ventilator according to the invention, obstructive sleep apnea can be treated, wherein artificial air is generated by means of the pressure generator 3, which air is fed to the patient 2 via the breathing hose 6 and the suction mask 7. At the same time, the artificial respirator 1 changes the pressure of the artificial air in such a way that: with a predetermined artificial air treatment pressure P_actWith the respiratory resistance R of the respiratory tract of the patient 2_AWA proportional value of the consumed pressure deltap is changed. Preferably, different ratio values are predefined for inhalation or exhalation, with which the treatment pressure P of the artificial air is varied_act。

List of reference numerals

1 Artificial respirator

2 patients

3 pressure generator

4 oscillating pump

5 addition position

6 breathing hose

7 breathing mask

8-stream processor

9 pressure processor

10 pressure regulating device

11 adder

12 change-over switch

13 servo processor

A output end

B output terminal

C Lung volume (degree of coordination)

int Strength

P respiratory pump

P_oBase pressure

p_actPressure of treatment

P_LIntrapulmonary pressure

R_AWRespiratory resistance

R_AWXExternally determined airway resistance

R_iFlow resistance

R_LFlow resistance

*_DVentilator airflow

*_LLeakage air flow

*_VRespiratory airflow

Delta p pressure loss

Claims (8)

1. A ventilator for the treatment of obstructive sleep apnea, having a pressure generating means for generating a therapeutic pressure (p)_act) A pressure generator (3) for artificial air, a pressure regulating device (10) for controlling the pressure generator (3), and a breathing hose (6) and breathing mask (7) for feeding the artificial air generated by the pressure generator (3) to the patient (2), characterized by a controller (13) for continuously determining the airway resistance (R) falling on the patient's airway_AW) And is used to make the therapeutic pressure change process basicIs proportionally matched to the determined course of the pressure loss (Δ p).

2. A respirator as claimed in claim 1, characterized in that it has a device for continuously determining the actual respiratory airflow (c) And for continuously determining the respiratory tract resistance (R)_AW) By a flow of breathing gas (13)) And respiratory resistance (R)_AW) The value of (2) is controlled.

3. An artificial respirator according to any one of the preceding claims, characterized in that the controller (13) is a servo processor.

4. An artificial respirator according to any one of the preceding claims, further comprising a means for automatically determining airway resistance (R) continuously or intermittently_AW) The apparatus of (1).

5. A respirator as claimed in any one of the preceding claims, characterized in that it comprises a device operating on the principle of automatic regulation (automatic CPAP principle), which automatically determines the optimum base pressure (p)_o)。

6. Method for controlling a ventilator according to any one of the preceding claims, characterized by for generating a treatment pressure (P)_act) Is controlled by a controller (13) in such a way that the treatment pressure of the artificial air is at a predetermined base pressure (p)_o) Starting from the fact that the respiratory resistance (R) of the respiratory tract of the patient (2) is actually determined by changing_AW) Of upper consumption pressure (Δ p)The ratio value is adjusted.

7. A method as claimed in claim 6, characterized in that the controller (13) presets an intensity signal which determines that the artificial ventilator (1) should compensate for the patient's respiratory resistance (R)_AW) The whole of the upper consumed pressure (Δ p) is again only compensated for a part thereof.

8. A method as claimed in claim 7, characterized in that an output value of the controller (13) is related to the predetermined base pressure (P)_o) Is added by an adder (11) and the resulting sum signal is used as the therapeutic pressure (p) regulated by the pressure generator (3)_act) Is transmitted to the pressure regulating device (10).