DE102010045839B4 - Method and device for ventilation with background frequency - Google Patents

Abstract

Breathing gas source with a control unit and measuring means for detecting spontaneous breathing, the control unit having a comparator which provides a first signal when spontaneous breathing is detected, so that the control unit controls the breathing gas source in such a way that a CPAP pressure level is provided, and when a failure is detected a second signal is provided after a time interval after spontaneous breathing, so that the control unit controls the breathing gas source in such a way that an inspiratory pressure level that is more than 4 hPa above the CPAP pressure level is generated and then an expiratory pressure level that is at least 4 hPa below the inspiratory pressure level is generated.

Description

The most common sleep disorder is obstructive sleep apnea (OSA). The respiratory flow is temporarily either significantly reduced (hypopnea) or completely interrupted (apnea). The resulting lack of oxygen creates a stressful situation that prevents restful sleep and damages the heart in the medium term. Even with periodic breathing, the patient is poorly supplied with oxygen. The extent of OSA is measured as the number of events per hour of sleep using the apnea-hypopnea index (AHI). The standard therapy for OSA is CPAP therapy (Continuous Positive Airway Pressure), in which a ventilator offers the patient a pressure that is permanently higher than atmospheric pressure. The patient breathes himself (spontaneous breathing). APAP therapy is also suitable here. The pressure is only increased during apnea or hypopnea.

Central sleep apnea is a disorder in the brain's control of breathing. Due to a periodic lack of respiratory drive, phases of breathing alternate with complete respiratory arrest.

Alternating periods of hyperventilation with increasing and decreasing tidal volume and phases of central hypopneas or apneas characterize periodic breathing. One of the many forms of periodic breathing is Cheyne-Stokes breathing.

Recent research shows that patients with obstructive sleep apnea can develop central sleep apnea or Cheyne-Stokes breathing with inadequate CPAP therapy. This so-called complex sleep apnea is a mixed form of OSA, central sleep apnea and periodic breathing.

Conventionally, patients with periodic breathing or central apnea have been ventilated with a different class of devices, the bilevel devices, by offering a higher inspiratory pressure level (IPAP) and a lower expiratory pressure level.

However, in patients with frequent periodic breathing or episodes of apnea, mechanical ventilation is only necessary during episodes of reduced or absent spontaneous breathing or periodic breathing to prevent the occurrence of oxygen desaturations and arousals.

DE 103 43 610 A1 describes a method for controlling a ventilator so that at least one control parameter for a ventilation pattern is at least temporarily specified by a control unit. During an analysis phase, at least one actual parameter of spontaneous patient breathing is recorded. The measured values are then transformed into the control parameter(s).

The ventilator can then be controlled depending on the calculated control parameters.

DE 10 2004 018 029 A1 describes a device for ventilation with a breathing gas source, a control device and a connection device for connection to a ventilation mask. The control device is connected to at least one sensor for detecting a breathing parameter of the patient. Limit values of a limit value memory defining the size of an acceptance window are adaptively changed by the control device depending on the measurement signal from the sensor in such a way that a lower limit value is increased if the breathing parameter detected by the sensor signal is below a tolerance value located within the acceptance window. In addition, the control device reduces an upper limit value if the breathing parameter is above a second tolerance value. The control device controls the ventilator depending on the breathing parameter if it is within the acceptance window, and depending on a predefined setpoint if the breathing parameter is outside the acceptance window.

DE 10 2006 018 042 A1 describes a method for controlling a ventilator with different functional states. The ventilator takes measurements and saves data in one or more functional states without calculations. The process of the device functions is unaffected by these measurements and data storage. Through this control, the ventilator can influence device functions in one or more additional functional states with simultaneous measurements and/or calculations, whereby the ventilator can automatically select or change the functional states based on the measurements and/or calculations.

DE 10 2007 039 004 A1 describes a method for detecting at least one respiratory parameter that is characteristic of the respiratory state of a patient. The time course of at least one state variable that changes repeatedly with ventilation is measured patients. The method can be used to control a ventilator, so that an optimization of the pressure volume generated by the ventilator is realized depending on a tidal volume determined from the state variables.

The object of the present invention is to further develop devices of the CPAP, APAP and bilevel classes in such a way that they detect the patient's spontaneous breathing and switch to a ventilation mode (mandatory ventilation) if there is no spontaneous breathing.

Another task is to offer a background frequency for ventilators of the CPAP, APAP and bilevel classes that responds adaptively to rapidly changing breathing positions and establishes minimum ventilation.

The cyclical recording of the parameters for the detection of spontaneous breathing and the corresponding evaluation mean that the device operation mode is transferred to a bilevel control cycle early and automatically, without the patient perceiving this as unpleasant.

Alternatively, the device switches back from mandatory mode to CPAP mode if the patient's spontaneous inspiration is detected again between two breaths in the bilevel cycle. The distance between breaths in the bilevel cycle (background frequency) remains the same. It is also thought to increase or decrease the interval between breaths in the bilevel cycle over time, e.g. B. depending on the breathing time volume achieved, in order to either improve the patient's ventilation or provoke him to spontaneous breathing again.

The device operation in the bilevel ventilation cycle comes as close as possible to the patient's natural ventilation process by measuring and saving the minute ventilation volume and/or the frequency as well as the inspiration and expiration durations after spontaneous breathing has been detected.

A simple device structure is provided by performing the bilevel ventilation cycle in a time-controlled manner.

It is also considered that detection of spontaneous breathing depends on a measurement of an EEG activity, an EMG activity, an EOG activity, an ECG activity, a measurement of the respiratory excursion (e.g. effort belts in piezoelectric or induction technology) or from actigraphy data.

In order to synchronize the operation of the ventilator with a natural breathing rhythm of the patient during ventilation, the patient's respiratory drive can be measured and used as a trigger signal for the ventilator in order to trigger a pressure build-up.

A fully automatic control process is achieved by cyclically evaluating the presence of spontaneous breathing and returning to CPAP mode when spontaneous breathing begins.

Exemplary embodiments of the invention are shown schematically in the drawings.

1 shows the basic structure of a ventilation device. In the area of a device housing 1 with a control panel 2 and display 3, a breathing gas source is arranged in the interior of the device. A connecting hose 5 is connected via a coupling 4. An additional pressure measuring hose 6 can run along the connecting hose 5 and can be connected to the device housing 1 via a pressure inlet connection 7. To enable data transfer, the device housing 1 has an interface 8 for USB and an insertion compartment for memory cards. Flow signals, pressure signals and detected events, in particular lack of spontaneous breathing and the onset of the background frequency, are stored in the internal data memory or on the memory card. An exhalation element 9 is arranged in the area of an extension of the connecting hose 5 facing away from the device housing 1. An exhalation valve can also be used.

The ventilator also has the following components as measuring means: a sensor for detecting a flow characteristic and/or a sensor for detecting a pressure characteristic. There is also a pressure controller that provides a necessary minimum pressure and compensates for fluctuations caused by the patient's breathing activity to such an extent that a pressure accuracy of +/-0.3 hPa is achieved.

In a preferred embodiment, an electronically controlled fan sucks in ambient air through a filter and conveys it to the device outlet. From here the air flows through the hose system and the breathing mask to the patient. Sensors detect the pressure in the breathing mask and in the hose system as well as the change in breathing phase. Accordingly, the fan provides the from IPAP and EPAP pressures set by the user. Switching from one pressure level to the other occurs by quickly changing the speed of the fan.

The device according to the invention is preferably also designed as an APAP device, which reacts to snoring, apneas, a flattening of the respiratory gas flow or obstructive pressure peaks with an increase in pressure. A version as a titration device is also being considered, which contains a real CPAP, APAP, Bilevel-S or Bilevel-ST mode. The proportion of breaths with spontaneous breathing and with background frequency is calculated internally in the device. The calculation results can be viewed on the device display or externally, e.g. B. can be visualized on a PC.

During mandatory breaths, any glottal occlusions that may occur are recognized and differentiated from obstructions, and a pressure response (a reduction in EEPAP and/or the pressure difference IPAP to EPAP) reduces future reflex glottal occlusions.

• • Oberes Druckniveau (IPAP oder maximaler IPAP der automatischen Steuerung): 9-25 mbar
• • Unteres Druckniveau (EPAP oder minimaler EPAP der automatischen Steuerung): 0-8 mbar
• • Endexspiratorisches Druckniveau (EEPAP bzw. CPAP oder die Druckgrenzen der APAP-Steuerung): 1-4 mbar über EPAP
• • Eventuelle Druckanstiegsgeschwindigkeit (Rampe): 0,2 s
• • Phasenzeit TI = TInspiration: 2 s oder 33 %
• • Phasenzeit TE = TExspiration: 4 s oder 66 % oder
• • Mandatorische Atemfrequenz (f): 10/min
• • Stärke der Ausatemerleichterung während CPAP- oder APAP-Modus: Stufe 2, Triggerschwelle 2-5 l/min oder Automatik-Trigger

Basic settings are e.g. E.g.:

• • Upper pressure level (IPAP or automatic control maximum IPAP): 9-25 mbar
• • Lower pressure level (EPAP or minimum EPAP of automatic control): 0-8 mbar
• • End-expiratory pressure level (EEPAP or CPAP or the pressure limits of the APAP control): 1-4 mbar above EPAP
• • Any pressure rise rate (ramp): 0.2 s
• • Phase time TI = TInspiration: 2 s or 33%
• • Phase time TE = TExspiration: 4 s or 66% or
• • Mandatory respiratory rate (f): 10/min
• • Strength of exhalation relief during CPAP or APAP mode: level 2, trigger threshold 2-5 l/min or automatic trigger

The inspiratory pressure level (IPAP) and also the CPAP pressure level are essentially constant. According to the invention, it is also intended to vary the pressure during inspiration slightly in order to make inhalation easier. In particular, the height of the pressure strokes and the edge steepness are set or stored in the device so that they can be accessed.

In a basic form, the pressure is raised from the EPAP to the IPAP level in two stages, with each stage being half the set final pressure. The slope is the same for both pressure levels.

A soft start function makes it easier to continue sleeping during the transition from CPAP mode to the bilevel cycle. For this purpose, an initial pressure can be set for inspiration and expiration, which is continuously increased to the therapy pressures IPAP and EPAP during the soft start phase. This function can be blocked. Or the soft start time can be limited. The device has an automatic switch-on. If this is activated, the device can be switched on by breathing into the breathing mask. The device is still switched off via the on/off

Power off button. The therapy mode and - depending on the mode - the currently applied values for IPAP and EPAP or CPAP, respiratory frequency (f) are shown on the display. Furthermore, spontaneous or mandatory breathing phase changes (triggered by the device) are displayed and the pressure change is displayed graphically.

To make exhalation easier, a lower level of the expiratory pressure curve or a magnitude of the expiratory pressure reduction is provided.

To make inhalation easier, an upper level of the inspiratory pressure curve or a strength of the inspiratory increase is provided.

The strength of the inspiratory increase and expiratory decrease is a maximum of 4 hPa each, so that no bilevel mode is used when spontaneous breathing is stable.

Operation by the user is carried out through target-oriented settings (scopes), which correspond to a preselection of certain parameters, which are retrieved from a memory and executed according to the preselection.

Scope SOFT: comfortable exhalation relief for OSA patients with high pressure requirements or central apneas. Low starting value for PDIFF, automatic background frequency slightly below the current spontaneous frequency.

Scope SUPP: Protection against hypoventilation and desaturation through additional ventilation support. Medium-high starting value for PDIFF, automatic background frequency slightly below the current spontaneous frequency.

Scope CONT: maximum relief for the respiratory muscles through a high level of breathing support. High start value for PDIFF, automatic Background frequency slightly above the current spontaneous frequency.

• Prio S (S = spontaneous) entlässt den Patienten sanft in die Spontanatmung. Schnell wirksamer Schutz vor Entsättigungen bei zentralen Störungen ohne zeitaufwendige Titration.

Two automatic background frequencies for effective protection against desaturations:

• Prio S (S = spontaneous) gently releases the patient into spontaneous breathing. Quickly effective protection against desaturation in the event of central disturbances without time-consuming titration.

If necessary, the patient is caught slightly below his current breathing rate. Once the patient's tidal volume is normalized, the frequency is slowly reduced to return the patient to spontaneous breathing. If desired, a lower and an upper limit (Fmin, Fmax) can be set for the control range.

Prio T (T = timed) supports maximum relief of the respiratory muscles. Relief of the respiratory muscles with physiological frequency adaptation without time-consuming titration. The patient is mandatorily ventilated slightly above his current respiratory rate. Although ventilation is largely mandatory, individual spontaneous breaths with a higher frequency or individual prolonged breaths as well as general adjustments to the patient's current frequency are possible. This adaptable, gentle T-ventilation reduces the risk of fighting.

S mode (spontaneous release of the trigger): The transition from one pressure level to the other is triggered exclusively by the patient's beginning breathing movements. A pressure drop to the set lower level also occurs when the inspiratory flow ends.

ST mode (spontaneous breathing and time): As long as the patient is breathing on his own, the device works in S mode. If the respiratory drive is lost, the device automatically switches to T mode and ventilates the patient at the specified safety frequency. Switching to T mode occurs after an adjustable delay time has elapsed.

T mode (time ventilation with a predefined fixed inspiration time): If the trigger function is switched off, the patient is ventilated with the set parameters. When the trigger is switched on, the device only accepts spontaneous trigger signals in the expiratory phase.

The breathing trigger detects the patient's efforts to inhale or exhale and signals this to a control device or stores the frequency. A flow-based trigger is integrated that can be adjusted separately for inhalation and exhalation.

In timed mode T and assisted controlled mode ST, the user can set the respiratory rate in the range of 6 to 45 breaths per minute and the inspiratory time in the range of 20% to 67% of the breathing period. In the assisted mode S and the assisted controlled mode ST, the user can choose one of 6 trigger levels for inspiration and expiration. The user can switch off the expiration trigger in ST mode. Expiration is then time-controlled. If you do not breathe into the device in S mode, the pressure is switched at a minimum frequency of 6 breaths per minute.

• 1 zeigt eine Beatmungsmaske 10, die als Nasalmaske ausgebildet ist. Eine Fixierung im Bereich eines Kopfes eines Patienten kann über eine Kopfhaube 11 erfolgen. Im Bereich ihrer dem Verbindungsschlauch 5 zugewandten Ausdehnung weist die Beatmungsmaske 10 ein Kupplungselement 12 auf.
• 2 veranschaulicht die drei Druckniveaus IPAP: oberes Druckniveau EPAP: unteres Druckniveau (sorgt für eine erleichterte Ausatmung und für ein angenehmes Atemgefühl) PDIFF (ΔIPAP-EPAP): unterstützt die Atmung EEPAP: endexspiratorisches Druckniveau, notwendiger Druck zur Beseitigung von Obstruktionen (Schienung)

In ST mode, the respiratory rate of the spontaneously breathing patient must be above the prescribed rate so that the device's time-controlled trigger does not become active. The device reacts to the change in breathing phases by changing the pressure level.

• 1 shows a ventilation mask 10, which is designed as a nasal mask. Fixation in the area of a patient's head can be done using a hood 11. In the area of its extension facing the connecting hose 5, the respiratory mask 10 has a coupling element 12.
• 2 illustrates the three pressure levels IPAP: upper pressure level EPAP: lower pressure level (ensures easier exhalation and a pleasant feeling of breathing) PDIFF (ΔIPAP-EPAP): supports breathing EEPAP: end-expiratory pressure level, pressure necessary to remove obstructions (splinting)

At time 1, the IPAP is still present and the inspiration maximum - visible at the apex of the flow curve - has certainly passed. The pressure level begins to decrease with a slight drop in pressure. As soon as the start of expiration is detected, the device actively brakes and the pressure ramp reaches its maximum steepness.

At time 2 the end of the reduction is reached. EPAP pressure is present. The difference between the pressures IPAP and EPAP is PDIFF (ΔI-E).

At time 3, the pressure level begins to increase from the EPAP to the EEPAP. This is reached at time 4. This is also the end of the increase. The increase in pressure depends on the breathing frequency.

At time 5 the inspiration begins. Here there is a rapid increase in pressure on the IPAP level, even if the EEPAP level has not yet been reached at time 4. The ramp steepness can be adjusted by the user in three steps (P rise).

At time 6 the IPAP is reached.

After switching on the device, a CPAP mode is initially carried out in a basic state, taking into account at least one parameter recorded by measurement to take into account the patient's own respiratory activity. Depending on this recorded breathing parameter, the control of the breathing gas delivery device is synchronized with the patient's spontaneous breathing.

The device detects the start of inspiration via gas flow or pressure sensors. The device also detects the end of the inspiration phase. For this purpose, two principles are used alternatively or in addition: pressure control and flow control.

Pressure control: When the specified pressure is reached in the system (tubes and patient airways), the device switches off pressure support and allows exhalation.

Flow control: As soon as the gas flow from the device to the patient falls below a certain value (close to zero), i.e. hardly any gas flows to the patient, the pressure support is switched off. This principle allows for better adaptation to the actual “inhalation need” of the patient.

If a further parameter evaluation shows that the patient is not breathing spontaneously, the process of recording the breathing parameter continues. In addition, the function of the ventilator in the bilevel ventilation cycle is synchronized with the patient's recorded spontaneous breathing. The detection of spontaneous breathing can, for example, be time-controlled or via a neural network to evaluate one or more special parameters. Possible parameters for detecting spontaneous breathing include, for example, respiratory parameters such as flow and pressure and/or measured values from ECG, EEG, EMG, EOG, thoracic function, abdomen or actigraphs.

If the evaluation of the spontaneous breathing shows that the patient is breathing, there is a transition from the bilevel ventilation cycle to the CPAP mode with the next EPAP pressure level.

If spontaneous breathing is no longer detected, a transition to the bilevel ventilation cycle occurs - e.g. B. with the patient's spontaneous breathing frequency recorded from the memory or the permanently stored background frequency - for the next inspiration with the IPAP pressure level.

When there is no spontaneous breathing, the device generates a significantly higher inspiratory or lower expiratory pressure than when spontaneous breathing is present. If several breaths are mandatorily generated in succession by the device, the pressure difference of IPAP and EPAP between breaths can be varied, allowing a smooth transition from CPAP or APAP mode to bilevel mode and back to CPAP or APAP mode he follows. To ease the transition, the time difference between mandatory breaths can also be varied.

To detect phases of intermittent hypoxia or hypoventilation, the following sensors are used alternatively or in addition and the sensor signals are continuously evaluated: pulse oximeter, CO2 sensor, effort sensor, respiratory gas pressure sensor, respiratory gas flow sensor.

If there is a hypoventilation phase that is significantly longer than a single hypopnea, preferably at least 1 to 5 minutes, the device according to the invention increases the pressure difference between inspiration and expiration in order to ventilate the patient better, even if spontaneous breathing is still detected.

This avoids ongoing periods of intermittent hypoventilation, which can lead to hypoxia.

Alternatively or in addition to this, the typical or average breathing time volume (the breathing time volume VT results from the product of the tidal volume VE and the breathing frequency f) or the tidal volume or the peak flow is determined and saved over at least 2 to 10 minutes and the individual current breaths are compared with the compared stored data.

It is then determined whether a certain number or percentage of breaths in a period > 1 minute are reduced compared to normal breathing, e.g. B. by at least 10%.

The device then increases the pressure difference between inspiration and expiration for a period of at least 1 minute and then decreases the pressure difference again when normal breathing is achieved compared to the recorded values.

In a preferred embodiment, the device learns the patient's required respiratory volumes or flows via external sensors during a titration night. If there is no spontaneous breathing, the device increases the pressure difference even further than in a phase with intermittent hypoventilation. If there is already intermittent hypoventilation, the device increases the pressure difference even further in the absence of spontaneous breathing than in the absence of spontaneous breathing in a phase of normal breathing.

In one embodiment, the first mandatory breath is triggered after apnea is detected (timed breath) only after an adjustable period of time.

• ➢ Ziel 1: komfortable Ausatemerleichterung und weitgehend Spontanatmung
• ➢ Auswahl am Gerät: Scope Soft
• ➢ Algorithmusverhalten: niedriger Startwert für PDIFF, automatische Hintergrundfrequenz etwas unterhalb der aktuellen Spontanfrequenz

OSAS patient with high pressure requirements

• ➢ Goal 1: comfortable exhalation and largely spontaneous breathing
• ➢ Selection on the device: Scope Soft
• ➢ Algorithm behavior: low starting value for PDIFF, automatic background frequency slightly below the current spontaneous frequency

• ➢ Ziel 2: Schutz vor intermittierenden oder längerfristigen Entsättigungen mit Arousals
• ➢ Auswahl am Gerät: Scope Supp
• ➢ Algorithmusverhalten: mittelhoher Startwert für PDIFF, automatische Hintergrundfrequenz etwas unterhalb der aktuellen Spontanfrequenz

Additional central respiratory events or hypoventilation phases

• ➢ Goal 2: Protection against intermittent or long-term desaturations with arousals
• ➢ Selection on the device: Scope Supp
• ➢ Algorithm behavior: medium-high starting value for PDIFF, automatic background frequency slightly below the current spontaneous frequency

• ➢ Ziel 3: geringer Anteil an Spontanatmung, Entlastung der Atemmuskulatur
• ➢ Auswahl am Gerät: Scope ACon (adaptiv kontrollierte Beatmung)
• ➢ Algorithmusverhalten: hoher Startwert für PDIFF, automatische Hintergrundfrequenz etwas oberhalb der aktuellen Spontanfrequenz

Additional need to reduce the work of breathing

• ➢ Goal 3: low proportion of spontaneous breathing, relief of the respiratory muscles
• ➢ Selection on the device: Scope ACon (adaptive controlled ventilation)
• ➢ Algorithm behavior: high starting value for PDIFF, automatic background frequency slightly above the current spontaneous frequency

The automatic background frequency with the aim of spontaneous breathing follows the changing breathing rate of the patient. If apnea occurs, a transition to mandatory ventilation occurs. On the other hand, the automatic background frequency ensures that the patient is not subjected to mandatory ventilation for an unnecessarily long time, but rather guides him back into spontaneous breathing.

For this purpose, flow-based breathing phase detection is carried out on the device side. The breathing frequency is determined from the sequence of breathing phases. This is averaged over a definable period of time. Weighted averaging is preferably carried out. The value of the patient's spontaneous breathing frequency determined in this way serves as a criterion for specifying a background frequency on the device side when controlling the process of the device. Using the background frequency, the device switches alternately to the IPAP or EPAP pressure level. The patient is therefore subject to mandatory ventilation. In addition, the patient's respiratory time volume (AZV) is recorded and averaged during spontaneous breathing. The value of the patient's spontaneous breathing AZV determined in this way serves as a criterion for the process control of the device for changing/slowing down a device-side background frequency with which the device ventilates the patient on a mandatory basis.

Based on the patient's determined spontaneous breathing frequency, a predeterminable lower limit of the spontaneous breathing frequency is now used as a trigger threshold for the transition to the mandatory operating mode. For example, a value of 60% to 90% of the spontaneous breathing frequency is defined as the trigger threshold. If the patient's spontaneous breathing frequency falls to a value below the triggering threshold, mandatory ventilation takes place. Mandatory ventilation starts with an increased PDiff (difference IPAP-EPAP or the EPAP pressure level) compared to spontaneous breathing. PDiff remains elevated until the breathing time volume of mandatory ventilation falls within the range of the last values determined from the spontaneous breathing phase. The background frequency is then gradually reduced until the patient is again able to breathe spontaneously.

If necessary, the patient is caught slightly below their current average breathing rate (e.g. at 80% of the current average spontaneous frequency). As long as the patient's respiratory time volume is not normalized, the ventilation support (PDIFF) is gradually increased with each timed breath. When the patient's respiratory time volume is normalized, the frequency is slowly reduced to return the patient to spontaneous breathing. As a result, mandatory ventilation occurs as often as necessary and as rarely as possible.

How to get in 3 detects, the period duration of the mandatory background frequency M is initially slightly below the current patient frequency S. After reaching the ventilation target (the patient's tidal volume is in the spontaneous breathing range), the frequency of the mandatory background frequency M is reduced again to enable spontaneous breathing. A lower and an upper limit for the control range can be specified at the user's discretion.

Fig. 4

The adaptive mandatory ventilation mode ensures both maximum relief for the respiratory muscles and at the same time ensures good acceptance by the patient thanks to the physiological frequency adjustment.

To do this, the sequence control gradually shortens the time until the next mandatory breath is triggered (timed breath) until the background frequency M is above the frequency of the spontaneously breathing patient S, i.e. the patient has been “run over” and allows himself to be controlled. If the patient is ventilated at the background frequency, this is slowly reduced again in the event of obstructions or after a set period of time has elapsed, for example by 1% to 15% every minute, until the spontaneous breathing frequency is reached again. As soon as the patient breathes spontaneously again, the background frequency is increased again. This automates the typical titration process when a patient is placed on mandatory ventilation and adapts it to the changing needs of the patient through ongoing iterative adjustment. Although ventilation is largely mandatory, individual spontaneous breaths with a higher frequency or individual prolonged breaths as well as general adjustments to the patient's current frequency are possible. The patient is mandatorily ventilated slightly above his current spontaneous breathing rate.

How to get in 4 detects, the mandatory background frequency M is slightly above the current patient frequency S. Although ventilation is largely mandatory, individual spontaneous breaths are possible. These then have a higher frequency or are extended.

Fig. 5

The IPAP-EPAP difference (PDIFF) is adjusted in such a way that maximum relief during the exhalation phase is guaranteed as EEPAP (= obstruction level) increases.

In addition, PDIFF increases when the patient experiences intermittent hypoventilation, which is detected as a reduction in minute ventilation (MV) over an epoch of 2 minutes, thus providing temporary additional ventilation support.

During mandatory breaths, PDIFF is also increased to provide effective controlled ventilation.

In 5a one can see that as EEPAP increases, PDIFF also increases. This ensures maximum comfort and an optimal breathing sensation with every EEPAP. When EEPAP is low, PDIFF is also small and allows for calm breathing. With high EEPAP, PDIFF is appropriately high and allows maximum relief during exhalation and thus optimal comfort.

In 5b one can see that PDIFF increases after epochs in which a respiratory deficit occurred. This means that a patient with intermittent hypoventilation receives more ventilation support during the critical phases. After normalization of breathing, PDIFF is reduced again.

In 6 the inspiratory pressure increase is illustrated. The ramp steepness from EEPAP to IPAP can be set by the user in three steps (P rise).

Claims (1)

Breathing gas source with a control unit and measuring means for detecting spontaneous breathing, the control unit having a comparator which provides a first signal when spontaneous breathing is detected, so that the control unit controls the breathing gas source in such a way that a CPAP pressure level is provided, and when a failure is detected a second signal is provided after a time interval after spontaneous breathing, so that the control unit controls the breathing gas source in such a way that an inspiratory pressure level that is more than 4 hPa above the CPAP pressure level is generated and then an expiratory pressure level that is at least 4 hPa below the inspiratory pressure level is generated.

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