Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
  • A61M16/0057—Pumps therefor
  • A61M16/0066—Blowers or centrifugal pumps
  • A61M16/0069—Blowers or centrifugal pumps the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
  • A61M16/021—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes operated by electrical means
  • A61M16/022—Control means therefor
  • A61M16/024—Control means therefor including calculation means, e.g. using a processor
  • A61M16/026—Control means therefor including calculation means, e.g. using a processor specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
  • A61M16/0003—Accessories therefor, e.g. sensors, vibrators, negative pressure
  • A61M2016/0015—Accessories therefor, e.g. sensors, vibrators, negative pressure inhalation detectors
  • A61M2016/0018—Accessories therefor, e.g. sensors, vibrators, negative pressure inhalation detectors electrical
  • A61M2016/0021—Accessories therefor, e.g. sensors, vibrators, negative pressure inhalation detectors electrical with a proportional output signal, e.g. from a thermistor
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
  • A61M16/0003—Accessories therefor, e.g. sensors, vibrators, negative pressure
  • A61M2016/003—Accessories therefor, e.g. sensors, vibrators, negative pressure with a flowmeter
  • A61M2016/0033—Accessories therefor, e.g. sensors, vibrators, negative pressure with a flowmeter electrical
  • A61M2016/0039—Accessories therefor, e.g. sensors, vibrators, negative pressure with a flowmeter electrical in the inspiratory circuit

Definitions

• This invention relates to a method of controlling the pressure provided by a CPAP device according to the preamble of claim 1, to a CPAP device 5 for carrying out such a method, and to a corresponding storage medium.
• the invention relates to a method in which the pressure is adjusted in response to respiratory events.
• CPAP continuous positive airway pressure
• a CPAP device applies by means of a compressor, preferably via a humidifier, via a hose and a nasal mask a positive overpressure up to about 30 mbar in the respiratory tract of the patient. This overpressure is designed to ensure that the upper airways throughout the night
• Fig. 1 shows CPAP device 1 and a patient 19.
• the CPAP device in turn comprises a compressor 4, a breathing tube 9, a respiratory mask 18, a pressure sensor 11 and a flow sensor 16.
• a compressor 4 a breathing tube 9, a respiratory mask 18, a pressure sensor 11 and a flow sensor 16.
• the compressor contains a turbine 8.
• the turbine is also referred to as fan, fan unit, compressor, fan or blower. These terms are used synonymously in this patent.
• the pressure sensor 11 is located in the compressor housing and measures the pressure generated by the turbine.
• the pressure gauge can be connected to the hose via a hose
• the pressure sensor can also be located in the respiratory mask and be connected to the compressor housing via electrical lines.
• one or more small holes 2 are mounted, so that on average over time an air flow from the compressor to
• the speed of the turbine 8 is controlled by a microcontroller 5 so that the measured with the pressure sensor 11 actual pressure coincides with a predetermined target pressure.
• the target pressure is conventionally preset under the supervision of a physician and referred to as titration pressure.
• the flow sensor can, for. B. be a sensor with heating wire 17.
• a restriction in the breathing tube may be provided for the respiratory flow measurement, whereby the differential pressure across the constriction is measured.
• the pressure sensors can be arranged directly in the breathing tube or connected to it via further pressure measuring hoses.
• the microcontroller 5 can also take over the pressure control.
• control methods have been developed for CPAP devices that lower the target pressure as much as possible.
• Such control is known from WO00 / 24446. This control is based on an algorithm in which at least three pressure values are successively set during an AutoSef operation: If the tidal volume is independent of the set pressures, the pressures were too high too low.
• BiPAP devices and multilevel devices have also been developed. Such a device is described in DE 691 32 030 T2.
• the pressure is raised by a valve during inhalation and lowered during exhalation.
• the valve is controlled to maintain constant pressure during inhalation and exhalation. If the valve position changes only slowly during an inhalation process, this is interpreted as the end of the inhalation process.
• Inaudible vibrations or pressure changes can be evaluated to determine if the patient's breathing is regular, irregular or apneic.
• the duration of inhalation and exhalation and the flow rates can be determined. This information can be stored in memory.
• an admittance from respiratory flow divided by pressure can be calculated. The time course of the admittance can be compared with stored admittance schemes. The number of the best matching admittance schemes can be used as a "pointer" to a table containing the action to be taken, such as an increase in pressure.
• WO 94/23780 describes a method for controlling the pressure of a CPAP device. If no respiratory disturbances occur during sleep, the pressure is gradually lowered. If sleep disorders such as apneas, hypopneas or snoring occur, the pressure is increased. US 5,335,654 and EP 0 934 723 A1 describe a similar process.
• EP 0 612 257 B1 also describes an auto-CPAP system which detects apneas, hypopneas and unstable respiration to adjust the pressure.
• WO 99/24099 describes a control method for an auto-CPAP device that accounts for apneas, hypopneas, decreased respiratory flow, and snoring.
• the respiratory flow signal is supplied to a band-limited differentiator. If the output signal of the differentiator exceeds an inhalation threshold or falls below an exhalation threshold, an exhalation detection signal or a one-event detection signal is determined.
• EP 0 934 723 A1 relates to the control of a CPAP device due to the detection of apneas and partial occlusion of the upper respiratory tract.
• DE 101 18 968 further a control method for CPAP devices is described.
• DE 101 18 968 is incorporated by reference into this application.
• the control method first calculates characteristics from a measured respiratory flow curve and a measured actual pressure curve of a CPAP device. Special combinations of features are combined into detectors. Flags are set in the detectors when they detect an event, ie respond to the event. The control method then changes the target pressure based on the event flags of the detectors.
• the control method has three different states, namely a normal state, a sensitive state, and a leak state, between which it is possible to switch back and forth. Some detectors operate in the sensitive state with parameters deviating from the normal state. The control process changes to the sensitive state when the control process lowers pressure in the normal state. By choosing the parameters for the sensitive state, this responds Control method faster if CPAP actual pressure is too low. If, for example, the mask is disconnected, the controller changes to the leak state
• the local maxima of the first derivative correspond to the maximum slope of the respiratory flow at the transition between inspiration and expiration. From the end of inspiration, the beginning of inspiration is searched for by searching for the first local minimum in the derivative. The expiration time results as a time difference between a minimum of the derivative and the preceding maximum.
• the most recent breath is compared to the previous breaths by calculating a cross-correlation function.
• the cross-correlation function has values between one and one, with the correlation equaling one when the two breaths match one another and equal to minus one when the curves are negatively correlated, i. if a peak in the breathing pattern coincides exactly with a valley in the considered data piece.
• the backward correlation is the mean value over a certain number of local maxima of the cross-correlation function before the current time.
• the first derivative of the respiratory flow after the time during inspiration is estimated or calculated. Subsequently, a straight line is adapted to the first derivative. The slope of this fitted straight line gives the mean curvature of inspiration.
• Pressure control of a typical CPAP device is not so fast that it is in would be able to correct even snoring sounds. Zero crossings are counted only during the inspiratory phase to allow the controller to respond only to inspiratory snoring. The variance of the actual pressure can also be used to detect snoring.
• the features calculate a respiratory arrest detector, an apnea detector, a hypopnea detector and a respiratory flow limitation detector as an indication of an increase in pressure as well as a normal detector as an indication of stable respiration and possible pressure reduction ,
• a respiratory standstill, apnea, hypnopnea and respiratory flow limitation detector are referred to below as respiratory events.
• the respiratory arrest detector responds if more than 2 minutes pass without detecting a breath. If this happens more than 3 times, the automatic pressure control stops.
• the apnea detector first detects breaths in which the expiratory time is longer than 10 seconds, referred to as respiratory arrest.
• the apnea detector responds when either one of the respiratory arrest lasts longer than 30 seconds during 2 consecutive respiratory arrest events, or when more than 3 consecutive respiratory arrest events occur.
• Respiratory arrest is consecutive if the duration of the intermediate hyperventilation block and respiratory period is ⁇ 60 seconds.
• hypopnea detection the non-normalized mean inspiratory volume, the backward correlation, and the snoring feature are used.
• Respiratory flow limitation detection uses the snoring feature, mean curvature, and backward correlation.
• the normal detector uses the correlation feature.
• Stable breathing is when the set pressure for a given time z. B. 180 s was not changed and during this time, the backward correlation, for example,> 0.86.
• the fuzzy logic is also known in the prior art. According to conventional logic, logical variables can only assume states 0 or 1, also referred to as “false” and “true”, respectively. In fuzzy logic, fuzzy variables can take any value between 0 and 1, including 0 and 1. The fuzzy logic is mainly used in control systems, which should consider the experience of professionals.
• fuzzy variables indicate membership in a set.
• the amount corresponds to a specific operating state of the device to be controlled.
• fuzzy logic it is possible to design a controller considering a limited number of typical operating conditions.
• the fuzzy logic provides a formalism for interpolating between the considered states.
• the object of the invention is to specify methods for controlling the setpoint pressure of a CPAP device, a CPAP device for carrying out the method, and a storage medium for a corresponding program, which make it possible for the patient to optimize the time course of the respiratory flow course of a patient Set CPAP target pressure.
• An advantage of a slow lowering of the pressure supplied by the CPAP device is that the pressure is much finer than the 1 mbar steps mentioned in DE 101 18 968 adjustable.
• the set pressure will be more optimal, so better to meet the condition as low as possible but as high as necessary.
• increasing the absolute value of the rate of temporal pressure change is that the pressure delivered by the CPAP device is rapidly lowered when it is still well above the optimal pressure.
• the occurrence of a respiratory event indicates that the pressure delivered by the CPAP device is already a bit too low. Under these circumstances it is advantageous to raise the pressure by a predetermined value quickly, so as stepwise as possible.
• the CPAP device When the CPAP device has reached approximately the optimum pressure, it lowers the set pressure, so to speak, in a trial-and-error manner to provoke a respiratory event. If, after the stepwise increase in pressure, the pressure at the beginning of the ramp is approximately reached, this is an indication that the optimum pressure has been approximately reached. Under these circumstances, it is advantageous to burden the patient less frequently with a probable lowering and thus to extend the time for keeping the pressure constant.
• Avoiding a ramp when the backward correlation is too low also advantageously prevents the patient in his sleep from being disturbed by the provocation of a respiratory event as a result of the lowering of the pressure exerted by the CPAP device.
• Fig. 1 is a CPAP device
• Fig. 2 is a flowchart for explaining the method according to the invention.
• FIG. 2 explains the method according to the invention with reference to a flowchart. It is essentially based on the ramp-shaped lowering of the target pressure in step 33.
• the invention is based on the finding that even with a slow change in the target pressure, the abovementioned features, such as the expiration time, in particular the backward correlation, a mean inspiratory volume and a mean curvature of the respiratory flow change only insignificantly over time, as long as the target pressure is still above that optimal pressure, so long as no respiratory events occur.
• the upper limit for the absolute value of the derivative of the pressure after the time can be 1 mbar per breath.
• the actually driven rate should be small compared to this value, ie less than 0.2 mbar per breath.
• a value of two minutes is stored in step 31 in a memory called "normal time”.
• the current target pressure is stored in step 32 in the memory "AiterDruck".
• the target pressure in step 33 is ramped down at a constant rate, ie the derivative of the target pressure after the time is constant.
• the CPAP device is controlled by a microcontroller.
• the signal supplied by the pressure sensor 11 is digitized with a similar step size.
• the control of the turbine by the microcontroller takes place in fine digital steps. All this means that the target pressure is actually not ramped, but rather lowered in small steps.
• a ramped lowering is therefore to be understood for the purposes of this application, when the pressure is lowered in a quasi-ramp in several small steps within a breathing cycle.
• a respiratory cycle lasts about 4 to 5 s, so that after 1 sec, a small step should take place.
• the small steps should be small compared to 1 mbar, ie less than 0.2 mbar.
• step 34 it is checked whether a respiratory event has occurred.
• a respiratory event is the opposite of stable breathing, ie a respiratory disorder.
• the detectors described in DE 101 18 968 with the exception of the normal detector, ie in particular the apnea, hypopnea and the Atemfiusslimitationsdetektor can be used.
• the latter detectors may be used with other respiratory disorder detection techniques known in the art, such as the admittance from respiratory flow divided by pressure described in DE 691 32 030 T2 or the reduced respiratory flow and snoring mentioned in WO 99/24099 become.
• step 34 the current time is stored in memory "Start Time” in step 35 for further use in step 41.
• the target pressure is increased stepwise by a predetermined value, for example by 1 mbar.
• the actual pressure follows the target pressure according to the inertia of the turbine 8 and the selected control parameters for the regulation of the actual pressure to the target pressure.
• a step-shaped Increasing the actual pressure delivered by the CPAP device should be understood to mean an increase occurring within a breathing cycle, ie within 4 to 5 seconds.
• the reason for the step-like raising of the target pressure as fast as possible is that when a respiratory event occurs, the actual pressure is already too low for the current sleeping state of the patient.
• the too low pressure should be raised as quickly as possible in order not to disturb the sleep of the patient by further respiratory events.
• the target pressure is compared with the value stored in the "AiterDruck" memory.
• the target pressure was stored at the beginning of the ramp. If the target pressure deviates from the pressure stored in the "AiterDruck” memory by more than tolerance in step 37, this is interpreted as indicating that the pressure at the beginning of the ramp was close to the optimum pressure for the patient's current sleep state.
• the time stored in the memory "normal time” is extended in step 38 in order not to disturb the sleep of the patient unnecessarily by further respiratory events, which are provoked by the lowering of the target pressure in step 33 test.
• the extension in step 38 may be done by adding a constant value or multiplying by a value greater than one.
• step 37 or 38 the target pressure is kept constant at least for the time stored in the "normal time” memory. This condition is checked in step 41.
• step 40 while the set pressure is kept constant, it is further checked whether respiratory events occur. If so, the target pressure is further increased in step 36 after the current time has been stored in the memory "Start Time” in step 35.
• step 42 After it is determined in step 41 that the time stored in the "normal time” memory has elapsed since the time stored in the memory "start time”, it is checked in step 42 whether the normal detector has responded.
• the backward correlation can be evaluated for this purpose.
• a predetermined value for example 0.86.
• HEP17 Hettorney Docket Number HEP17, title “Procedure for a ventilator, ventilator and storage medium", applicant: seleon gmbh).
• step 42 If the backward correlation is sufficiently high, ie if a normal event is determined in step 42, after the current target pressure has been stored in the memory "AiterDruck" in step 32, the target pressure is again reduced in step 33 until a respiratory event is reached in step 34 is determined.
• the target pressure in step 33 is lowered not with a constant rate ramp, but with a rate increasing in absolute value over time. This results in the target pressure approaching the optimum pressure in a shorter time if the target pressure is initially far above the optimum pressure.
• the rate may be increased in proportion to the time that has elapsed since the start time of the ramp, resulting in a downwardly open parabola for the target pressure.
• the events detected by the detectors are treated as fuzzy variables.
• the controller operates continuously.
• the transition from "no event” to "event occurred” ie the range in which the fuzzy variable increases from 0 to 1, so that the corresponding fuzzy variable reaches the value 0.5 at the above limit.
• the width of the selected transition region and the course of the transition function are of secondary importance for the quality of the control process.
• the normal fuzzy variable may assume a value of zero if the backward correlation falls within a range of 0.82 to 0.9, and linearly increases from 0 to 1 1 when the backward correlation exceeds 0.9.
• other functions such as a suitably scaled Arctan function or a probability integral ⁇ (x) may be used to design the transition region:
• the rate of pressure change is determined using fuzzy variables from the sum of the fuzzy variables supplied by the individual detectors and preferably weighted by coefficients.
• the coefficients take into account that, for example, when respiratory arrest is detected, the pressure is increased rapidly, while with respiratory flow limitation, the target pressure of the CPAP device is increased more slowly.
• the coefficient for the apnea-fuzzy variable will be greater than that for the respiratory-flow-limiting fuzzy variable.
• the absolute value of the rate at which the target pressure is decreased in step 33 may be lowered if one or more respiratory events are already detected a little, ie the fuzzy variables values in the range of 0.1 or 0.2. In this way, the target pressure is lowered more slowly as the breathing becomes less regular.
• the step height of the increase of the target pressure in step 36 may be made dependent on the fuzzy variables with which the respiratory event has occurred.
• each fuzzy variable has occurred for a particular respiratory event such as apnea or hypopnea.
• increasing the target pressure depends on the fuzzy variable having the highest value, that is, the fuzzy variable most likely to signal a respiratory event. For example, if this variable has a value of 0.8, the target pressure is raised by 1 mbar. If it has a value of 0.9, the increase of the target pressure can amount to 1, 1 mbar.
• Rate can be started when the backward correlation approaches the value of 0.86 from below, so that the corresponding fuzzy variable more and more clearly Normal event announces.
• the above-described desired pressure control methods according to the invention can also be used in BiPAP devices and in multilevel devices.
• the target pressure determined by the control method can be used as the higher pressure in BiPAP devices or the highest pressure in multilevel devices.
• the pressure determined by a control method according to the invention indicates the time average of the pressures generated by a BiPAP or multilevel device.
• a CPAP device may be equipped with a slot 6, which is connected via a data line 10 to the microcontroller 5.
• a storage medium 7 can be inserted to store another program in the microcontroller 5. In this way the firmware can be updated.

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• Health & Medical Sciences (AREA)
• Emergency Medicine (AREA)
• Pulmonology (AREA)
• Engineering & Computer Science (AREA)
• Anesthesiology (AREA)
• Biomedical Technology (AREA)
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• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)

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• 2002
  • 2002-11-19 DE DE10253935A patent/DE10253935B3/de not_active Expired - Fee Related
• 2003
  • 2003-10-30 WO PCT/DE2003/003610 patent/WO2004045693A2/fr active Application Filing
  • 2003-10-30 AU AU2003283201A patent/AU2003283201A1/en not_active Abandoned
  • 2003-10-30 JP JP2004552382A patent/JP4928731B2/ja not_active Expired - Fee Related

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