WO2008025079A1 - Determination of leak during cpap treatment - Google Patents

Determination of leak during cpap treatment Download PDF

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Publication number
WO2008025079A1
WO2008025079A1 PCT/AU2007/001255 AU2007001255W WO2008025079A1 WO 2008025079 A1 WO2008025079 A1 WO 2008025079A1 AU 2007001255 W AU2007001255 W AU 2007001255W WO 2008025079 A1 WO2008025079 A1 WO 2008025079A1
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Prior art keywords
determining
flow rate
leak
air
point
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Application number
PCT/AU2007/001255
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French (fr)
Inventor
David John Bassin
Original Assignee
Resmed Ltd
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Priority to JP2009525857A priority Critical patent/JP2010501290A/en
Priority to EP07800217A priority patent/EP2063942A1/en
Publication of WO2008025079A1 publication Critical patent/WO2008025079A1/en

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    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES 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
    • A61M16/00Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/0057Pumps therefor
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES 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
    • A61M16/00Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/06Respiratory or anaesthetic masks
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES 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
    • A61M16/00Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/021Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes operated by electrical means
    • A61M16/022Control means therefor
    • A61M16/024Control means therefor including calculation means, e.g. using a processor
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES 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
    • A61M16/00Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/0003Accessories therefor, e.g. sensors, vibrators, negative pressure
    • A61M2016/0015Accessories therefor, e.g. sensors, vibrators, negative pressure inhalation detectors
    • A61M2016/0018Accessories therefor, e.g. sensors, vibrators, negative pressure inhalation detectors electrical
    • A61M2016/0021Accessories therefor, e.g. sensors, vibrators, negative pressure inhalation detectors electrical with a proportional output signal, e.g. from a thermistor
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES 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
    • A61M16/00Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/0003Accessories therefor, e.g. sensors, vibrators, negative pressure
    • A61M2016/003Accessories therefor, e.g. sensors, vibrators, negative pressure with a flowmeter
    • A61M2016/0033Accessories therefor, e.g. sensors, vibrators, negative pressure with a flowmeter electrical
    • A61M2016/0036Accessories therefor, e.g. sensors, vibrators, negative pressure with a flowmeter electrical in the breathing tube and used in both inspiratory and expiratory phase
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES 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
    • A61M2205/00General characteristics of the apparatus
    • A61M2205/15Detection of leaks
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES 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
    • A61M2205/00General characteristics of the apparatus
    • A61M2205/16General characteristics of the apparatus with back-up system in case of failure
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES 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
    • A61M2205/00General characteristics of the apparatus
    • A61M2205/50General characteristics of the apparatus with microprocessors or computers

Definitions

  • This invention relates to treatment of apneas and other respiratory disorders.
  • it relates to methods and apparatus for the determination of leakage airflow and true respiratory airflow, during the mechanical application of positive airway pressure.
  • breathable gas is supplied from a mechanical respirator or ventilator, for example via a mask, at a pressure which may be higher during inspiration and lower during expiration.
  • a mechanical respirator or ventilator for example via a mask
  • any reference to a "mask” is to be understood as including all forms of devices for passing breathable gas to a person's airway, including nose masks, nose and mouth masks, nasal prongs/pillows and endotracheal or tracheostomy tubes.
  • the term "ventilator” is used to describe any device that does part of the work of breathing.
  • one measures the subject's respiratory airflow during mechanical ventilation to assess adequacy of treatment, or to control the operation of the ventilator.
  • Respiratory airflow is commonly measured with a pneumotachograph placed in the gas delivery path between the mask and the pressure source. Leaks between the mask and the subject are unavoidable.
  • the pneumotachograph measures the sum of the respiratory airflow plus the flow through the leak. If the instantaneous flow through the leak is known, the respiratory airflow can he calculated by subtracting the flow through the leak from the flow at the pneumotach.
  • Some methods to correct for the flow through the leak assume (i) that the leak is substantially constant, and (ii) that over a sufficiently long time, inspiratory and expiratory respiratory airflow will cancel. If these assumptions are met, the average flow through the pneumotach over a sufficiently long period will equal the magnitude of the leak, and the true respiratory airflow may then be calculated as described.
  • FIG. 1a shows a trace of measured mask pressure in bi-level CPAP (Continuous Positive Airway Pressure) treatment between about 4 cm H 2 O on expiration and 12 cm H 2 O on inspiration.
  • FIG. 1b shows a trace of true respiratory airflow in synchronism with the mask pressures.
  • CPAP Continuous Positive Airway Pressure
  • FIG. 1d shows a trace of true respiratory airflow in synchronism with the mask pressures.
  • the measured mask flow shown in FIG. 1d now includes an offset due to the leak flow.
  • the prior art method determines the calculated leak flow over a number of breaths, as shown in FIG. 1e.
  • the resulting calculated respiratory flow as the measured flow minus the calculating leak flow is shown in FIG. 1f, having returned to the correct mean value, however is incorrectly scaled in magnitude, giving a false indication of peak positive and negative airflow.
  • the method will not work in the case of a subject who is making no respiratory efforts, and is momentarily not being ventilated at all, for example during an apnea, because for the duration of the apnea there is no start or end of breath over which to make a calculation.
  • Berthon-Jones attempts to deal with sudden changes in instantaneous leak flow by dynamically adjusting the filter's time constant using fuzzy logic, lengthening the time constant if it is certain that the leak is steady, reducing the time constant if it is certain that the leak has suddenly changed, and using intermediately longer or shorter time constants if it is intermediately certain that the leak is steady.
  • Berthon-Jones also develops a jamming index by fuzzy logic to deal with the case of a large and sudden increase in the conductance of the leak, in which case the calculated respiratory airflow will be incorrect.
  • the calculated respiratory airflow will be large positive for a time that is large compared with the expected duration of a normal inspiration.
  • the calculated respiratory airflow will be large negative for a time that is large compared with the duration of normal expiration.
  • the jamming index i.e. an index of the degree of certainty that the leak has suddenly changed, is derived, such that the longer the airflow has been away from zero, and by a larger amount, the larger the index.
  • the explicit calculation of the jamming index by fuzzy logic is described in the '129 patent, which is incorporated herein by reference.
  • the time constant for the low pass filters is then adjusted to vary inversely with the jamming index.
  • the index will be large, and the time constant for the calculation of the conductance of the leak will be small, allowing rapid convergence on the new value of the leakage conductance.
  • the index will be small, and the time constant for calculation of the leakage conductance will be large, enabling accurate calculation of the instantaneous respiratory airflow.
  • the index will be progressively larger, and the time constant for the calculation of the leak will progressively reduce.
  • the index will be of an intermediate value
  • the time constant for calculation of the impedance of the leak will also be of an intermediate value
  • This invention rapidly determines the instantaneous leak in a CPAP system without detailed modeling the source of the leak and without having to determine the precise phase in a breathing cycle at which the leak occurs. It relies instead on the use of timers to define the breathing cycle and a calculation to assure that the instantaneous flow is compared to the flow over a time period long enough to include an entire breath. It does this by looking backward to include an entire phase cycle. This avoids having to take long term averages over multiple breaths, or to have a model that recognized the beginning and end of a breath.
  • the present invention is motivated by the desire to determine instantaneous leak without having to resort to the computationally expensive processes of fuzzy logic.
  • it provides a system in which a patient's breathing effort is synchronized with the flow from a ventilator by the use of timers rather than by a complex measurement of the phase of a breathing cycle. Synchronization is flow triggered and phase is a bookkeeping device only. Cycling between pressures suitable for inspiration and expiration is controlled by thresholds that change during breaths.
  • a target ventilation is defined and supported by a variable backup rate.
  • Servo control of gross alveolar ventilation is provided in which the further a breathing pattern moves from the target, the faster the response of the system. This is designed to stop small breaths from counting for effective ventilation.
  • the present invention uses triggering to achieve synchronization between the patient's effort and the ventilator functions. This is accomplished by setting cycling thresholds that vary with time.
  • the parameters are TjMin, T.Max, T e Min and T e Max, respectively the minimum and maximum time that inspiration and expiration can persist. Triggering thus consists in the setting of TjMin, T 1 MaX, T e Min and T e Max.
  • Triggering of a change in flow to begin an inspiration-expiration cycle is subject to an adjustable threshold value. However there can be no triggering before the minimum expiration time (TeMin). Cycling from inspiration to expiration is subject to an initial absolute refractory period (TiMin), where the threshold is an adjustable proportion of the peak flow, but the threshold is constrained to be within predetermined limits. It is therefore less likely to cycle early in timed breaths (i.e. relative refractory period) in order to make too-short timed breaths less likely. In any event, cycling will occur when a maximum inspiratory time is reached, which time is calculated automatically. Typically, a clinician sets the backup rate to be delivered during a sustained period of timed breaths ("apnoeic backup rate").
  • the backup rate during spontaneous breathing is 2/3 of apnoeic backup rate.
  • the backup rate increases progressively, typically over 5 breaths, to the apnoeic rate.
  • the backup rate increases faster if ventilation well below target, more slowly if at target, not at all if well above target. Any triggered breath causes the backup rate to drop to 2/3 of apnoeic rate.
  • the breath phase is by definition 0 at the start of inspiration, 0.5 at the start of expiration, and approaches 1 at the end of expiration. As a bookkeeping device it is sufficient to consider the phase as a linear function between transition points. During inspiration the phase may be linearized in segments at such a rate of change during inspiration that the phase will reach 0.5 at TiMax and at such a rate of change of phase during expiration that phase will reach 1 at TeMax.
  • the phase will thus show jumps if the switch from inspiration to expiration occurs as the result of a timeout.
  • the phase now is a broken series of line segments exhibiting jumps.
  • TiMax is reached, cycling occurs due to time and the phase curve is continuous. If cycling from inspiration to expiration occurred due to a flow threshold, then the phase will have an upward jump. If T e Max is reached then triggering occurs due to time, a backup breath is delivered and the phase drops suddenly to zero. If triggering occurs due to flow to end the expiration then the phase will not reach 1. Correcting for Leak
  • Leak makes the estimation of patient flow difficult., since patient flow measurement is the basis of a ventilation estimate. What is provided is a leak algorithm that responds rapidly to changes in leak, in a few breaths yet has very stable baseline, which effectively suspends changes in pressure support while adapting to a new leak level after a big change, and can handle moderately large leaks (0.6 l/s).
  • the leak flow values may be averaged over the last 5 points (0.1 seconds) and stored in a buffer accompanied by the associated breath phase, so that the search for the last breath was in a buffer of 100 points, and done every 0.1 seconds.
  • the 50 Hz averaged leak estimate can then be calculated at 50 Hz by linear interpolation between the most recent averaged leak estimate and the averaged leak estimate just before it.
  • the backup rate varies from breath to breath, so the slope of the phase curves may vary from breath to breath:
  • the servoventilation of the present invention automatically adjusts pressure support to provide at least a target ventilation, between a minimum pressure support (which may be zero) and a maximum pressure support.
  • Min and max pressure support are set by a clinician.
  • the target ventilation is the non-anatomical- deadspace ventilation (a crude approximation to alveolar ventilation). The aim is mainly to prevent small breaths at a high rate from being counted as effective ventilation.
  • the anatomical deadspace is set manually.
  • the clinical procedure is to learn the target ventilation and backup rate while the patient is awake. Then a target ventilation ramp and EPAP is set. Then possibly adjust the maximum inspiratory fraction and the cycling threshold, which is a proportion of the peak flow. A default value is 25%.
  • Jamming is a state in which there exists a change in a leak that has not been fully compensated for.
  • the presence of a leak can change the flow so that it doesn't get close to its zero crossing points at which the transition from inspiration to expiration is usually recognized.
  • the pressure is adjusted to switch from inspiration to expiration at such a zero crossing point, the change will not be recognized and the pressure will remained "jammed" in one phase.
  • the low pass filtered flow should oscillate around a base line that can be recognized as the new criteria for the phase change.
  • the jamming index J is related to leak flow by the formula:

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Abstract

In a CPAP system controlled by timers, leak is determined at each instant by a lookback for a time as long as single breath and an integration of flow over that period. A jamming index indicates whether the leak has suddenly increased, at which time the updating of the flow ceases until the leak variation stops its rapid rate of change.

Description

DETERMINATION OF LEAK DURING CPAP
TREATMENT
Related Applications
This application claims priority of US Provisional Application 60/823,934, filed August 30, 2006, the specification and drawings of which are incorporated herein by reference.
Field Of The Invention
This invention relates to treatment of apneas and other respiratory disorders. In particular it relates to methods and apparatus for the determination of leakage airflow and true respiratory airflow, during the mechanical application of positive airway pressure.
Background of the Invention
For the treatment of apneas and other respiratory disorders occurring during sleep, breathable gas is supplied from a mechanical respirator or ventilator, for example via a mask, at a pressure which may be higher during inspiration and lower during expiration. (In this specification any reference to a "mask" is to be understood as including all forms of devices for passing breathable gas to a person's airway, including nose masks, nose and mouth masks, nasal prongs/pillows and endotracheal or tracheostomy tubes. The term "ventilator" is used to describe any device that does part of the work of breathing.) Typically one measures the subject's respiratory airflow during mechanical ventilation to assess adequacy of treatment, or to control the operation of the ventilator. Respiratory airflow is commonly measured with a pneumotachograph placed in the gas delivery path between the mask and the pressure source. Leaks between the mask and the subject are unavoidable. The pneumotachograph measures the sum of the respiratory airflow plus the flow through the leak. If the instantaneous flow through the leak is known, the respiratory airflow can he calculated by subtracting the flow through the leak from the flow at the pneumotach.
Some methods to correct for the flow through the leak assume (i) that the leak is substantially constant, and (ii) that over a sufficiently long time, inspiratory and expiratory respiratory airflow will cancel. If these assumptions are met, the average flow through the pneumotach over a sufficiently long period will equal the magnitude of the leak, and the true respiratory airflow may then be calculated as described.
The known method is only correct if the pressure at the mask is constant. If, on the other hand, the mask pressure varies with time (for example, in the case of a ventilator), assumption (i) above will be invalid, and the calculated respiratory airflow will therefore be incorrect. This is shown markedly in FIGS. 1a-1f.
FIG. 1a shows a trace of measured mask pressure in bi-level CPAP (Continuous Positive Airway Pressure) treatment between about 4 cm H2O on expiration and 12 cm H2O on inspiration. FIG. 1b shows a trace of true respiratory airflow in synchronism with the mask pressures. At time=21 seconds a mask leak occurs, resulting in a leakage flow from the leak that is a function of the treatment pressure, as shown in FIG. 1c. The measured mask flow shown in FIG. 1d now includes an offset due to the leak flow. The prior art method then determines the calculated leak flow over a number of breaths, as shown in FIG. 1e. The resulting calculated respiratory flow, as the measured flow minus the calculating leak flow is shown in FIG. 1f, having returned to the correct mean value, however is incorrectly scaled in magnitude, giving a false indication of peak positive and negative airflow.
Another prior art arrangement is disclosed in European Publication No. 0 714 670 A2, including a calculation of a pressure-dependent leak component. The methodology relies on knowing precisely the occurrence of the start of an inspiratory event and the start of the next inspiratory event. In other words, the leak calculation is formed as an average over a known breath and applied to a subsequent breath. This method cannot be used if the moment of start and end of the previous breath are unknown. In general, it can be difficult to accurately calculate the time of start of a breath. This is particularly the case immediately following a sudden change in the leak.
Furthermore, the method will not work in the case of a subject who is making no respiratory efforts, and is momentarily not being ventilated at all, for example during an apnea, because for the duration of the apnea there is no start or end of breath over which to make a calculation.
In US patent 6,152,129 (Berthon-Jones) the leak is determined by first estimating the conductance of the leak path from the longterm orifice flow:
Figure imgf000004_0001
where GL = i/RJs conductance (L denotes leak), Q is instantaneous flow, p is instantaneous pressure and <> denotes a longterm average calculated for example by low pass filtering with an HF or other filter having a long time constant. Note that the word "average" as used herein contains the general sense inclusive of the result of a low pass filtering step, and is not limited to an arithmetic mean or other standard average such as the RMS average.
The instantaneous leak flow, based on the model of the flow through an
orifice is then QL = — yfp . Note that the instantaneous respiratory airflow is then
Figure imgf000004_0002
Berthon-Jones attempts to deal with sudden changes in instantaneous leak flow by dynamically adjusting the filter's time constant using fuzzy logic, lengthening the time constant if it is certain that the leak is steady, reducing the time constant if it is certain that the leak has suddenly changed, and using intermediately longer or shorter time constants if it is intermediately certain that the leak is steady.
Berthon-Jones also develops a jamming index by fuzzy logic to deal with the case of a large and sudden increase in the conductance of the leak, in which case the calculated respiratory airflow will be incorrect. In particular during apparent inspiration, the calculated respiratory airflow will be large positive for a time that is large compared with the expected duration of a normal inspiration. Conversely, if there is a sudden decrease in conductance of the leak, then during apparent expiration the calculated respiratory airflow will be large negative for a time that is large compared with the duration of normal expiration.
Therefore, the jamming index, i.e. an index of the degree of certainty that the leak has suddenly changed, is derived, such that the longer the airflow has been away from zero, and by a larger amount, the larger the index. The explicit calculation of the jamming index by fuzzy logic is described in the '129 patent, which is incorporated herein by reference.
The time constant for the low pass filters is then adjusted to vary inversely with the jamming index. In operation, if there is a sudden and large change in the leak, the index will be large, and the time constant for the calculation of the conductance of the leak will be small, allowing rapid convergence on the new value of the leakage conductance. Conversely, if the leak is steady for a long time, the index will be small, and the time constant for calculation of the leakage conductance will be large, enabling accurate calculation of the instantaneous respiratory airflow. In the spectrum of intermediate situations, where the calculated instantaneous respiratory airflow is larger and for longer periods, the index will be progressively larger, and the time constant for the calculation of the leak will progressively reduce. For example, at a moment in time where it is uncertain whether the leak is in fact constant, and the subject merely commenced a large sigh, or whether in fact there has been a sudden increase in the leak, the index will be of an intermediate value, and the time constant for calculation of the impedance of the leak will also be of an intermediate value.
Brief Description of the Invention
This invention rapidly determines the instantaneous leak in a CPAP system without detailed modeling the source of the leak and without having to determine the precise phase in a breathing cycle at which the leak occurs. It relies instead on the use of timers to define the breathing cycle and a calculation to assure that the instantaneous flow is compared to the flow over a time period long enough to include an entire breath. It does this by looking backward to include an entire phase cycle. This avoids having to take long term averages over multiple breaths, or to have a model that recognized the beginning and end of a breath.
Sudden changes in a leak are recognized and expressed as a jamming index value, which is then used as a parameter to control the temporary secession of updating flow values.
Further forms of the invention include those set out in the claims.
Detailed Description of Preferred Embodiments of the Invention
The present invention is motivated by the desire to determine instantaneous leak without having to resort to the computationally expensive processes of fuzzy logic. In particular it provides a system in which a patient's breathing effort is synchronized with the flow from a ventilator by the use of timers rather than by a complex measurement of the phase of a breathing cycle. Synchronization is flow triggered and phase is a bookkeeping device only. Cycling between pressures suitable for inspiration and expiration is controlled by thresholds that change during breaths.
What is important is achieving synchronization between the patient's breathing effort and the action of the ventilator. A target ventilation is defined and supported by a variable backup rate. Servo control of gross alveolar ventilation is provided in which the further a breathing pattern moves from the target, the faster the response of the system. This is designed to stop small breaths from counting for effective ventilation.
One problem is caused by sudden changes in a leak. It is necessary to respond as quickly as a monitored parameter recognizes the change. This is accomplished by having controlling thresholds respond to jamming.
The present invention uses triggering to achieve synchronization between the patient's effort and the ventilator functions. This is accomplished by setting cycling thresholds that vary with time. The parameters are TjMin, T.Max, TeMin and TeMax, respectively the minimum and maximum time that inspiration and expiration can persist. Triggering thus consists in the setting of TjMin, T1MaX, TeMin and TeMax.
These relate to instantaneous backup rates, since
TtotMax=TiMax+TeMax.=1/Backup-rate.
Triggering of a change in flow to begin an inspiration-expiration cycle is subject to an adjustable threshold value. However there can be no triggering before the minimum expiration time (TeMin). Cycling from inspiration to expiration is subject to an initial absolute refractory period (TiMin), where the threshold is an adjustable proportion of the peak flow, but the threshold is constrained to be within predetermined limits. It is therefore less likely to cycle early in timed breaths (i.e. relative refractory period) in order to make too-short timed breaths less likely. In any event, cycling will occur when a maximum inspiratory time is reached, which time is calculated automatically. Typically, a clinician sets the backup rate to be delivered during a sustained period of timed breaths ("apnoeic backup rate"). This can be set at the patient's optimum rate at end of learning period. The backup rate during spontaneous breathing (triggered breaths) is 2/3 of apnoeic backup rate. On a transition from triggered to timed breaths, the backup rate increases progressively, typically over 5 breaths, to the apnoeic rate. The backup rate increases faster if ventilation well below target, more slowly if at target, not at all if well above target. Any triggered breath causes the backup rate to drop to 2/3 of apnoeic rate.
Phase as a measure of Cycle Progress
The breath phase, is by definition 0 at the start of inspiration, 0.5 at the start of expiration, and approaches 1 at the end of expiration. As a bookkeeping device it is sufficient to consider the phase as a linear function between transition points. During inspiration the phase may be linearized in segments at such a rate of change during inspiration that the phase will reach 0.5 at TiMax and at such a rate of change of phase during expiration that phase will reach 1 at TeMax.
The phase will thus show jumps if the switch from inspiration to expiration occurs as the result of a timeout. Thus unlike the situation in Berthon-Jones, where the phase is forced to follow a smooth curve, the phase now is a broken series of line segments exhibiting jumps. There are a few cases to be considered: If TiMax is reached, cycling occurs due to time and the phase curve is continuous. If cycling from inspiration to expiration occurred due to a flow threshold, then the phase will have an upward jump. If TeMax is reached then triggering occurs due to time, a backup breath is delivered and the phase drops suddenly to zero. If triggering occurs due to flow to end the expiration then the phase will not reach 1. Correcting for Leak
Leak makes the estimation of patient flow difficult., since patient flow measurement is the basis of a ventilation estimate. What is provided is a leak algorithm that responds rapidly to changes in leak, in a few breaths yet has very stable baseline, which effectively suspends changes in pressure support while adapting to a new leak level after a big change, and can handle moderately large leaks (0.6 l/s).
To determine leak one can integrate the flow over a time period as long as a single breath. So that this can be accomplished immediately, the invention looks back from the present time to a time when the respiration was at the same phase as the phase at the current time. Starting with the current phase, say φo, the invention looks backwards in time for the most recent phase in the interval [φo - 0.75, φ0 - 0.25]. This is seeking a point in time at least 0.25 of a breath before the present. When such a phase is found, the invention calculates φ1= φ0- 0.25 and looks backward for a phase in he interval [φ-i - 0.75, φr0.25]. This is continued, 0.25 at a time, i.e. φι+1= φr.O25. When a phase is found which is in [φ3 -.075, φ3 -0.25] the iteration ceases, since this is just [φo-0.5, φ0]. if phase varied continuously this would have found exactly φ0; in reality it will most likely find φ0- ε, where hopefully ε is small. By proceeding in this manner we have some confidence that the phase has gone backward rather than forward. This algorithm will regard two phase transitions of 0.5 in succession as being movement backward, thought the actual direction is of course actually indeterminate. If this algorithm fails to find a point between the present moment and a time T|eak before the present which meats this criterion, we take the averaging period to be T|eak. As an implementation detail, to reduce computational requirements, the leak flow values may be averaged over the last 5 points (0.1 seconds) and stored in a buffer accompanied by the associated breath phase, so that the search for the last breath was in a buffer of 100 points, and done every 0.1 seconds. The 50 Hz averaged leak estimate can then be calculated at 50 Hz by linear interpolation between the most recent averaged leak estimate and the averaged leak estimate just before it.
Setting the Backup and Timing Parameters
The backup rate varies from breath to breath, so the slope of the phase curves may vary from breath to breath: At each breath the backup period is calculated ( = 60 seconds / backup rate in breaths/min). TiMax is calculated at the start of each inspiration as the backup period multiplied by the inspiratory fraction, so the slope of the inspiratory breath phase line ( = 0.5 / TiMax) varies from breath to breath. TeMax is calculated at the start of each expiration to be that time which will deliver the current backup rate ( = backup period - actual inspiratory time), so the slope of the expiratory breath phase line ( = 0.5 / TeMax) varies from breath to breath. The servoventilation of the present invention automatically adjusts pressure support to provide at least a target ventilation, between a minimum pressure support (which may be zero) and a maximum pressure support. Min and max pressure support are set by a clinician. The target ventilation is the non-anatomical- deadspace ventilation (a crude approximation to alveolar ventilation). The aim is mainly to prevent small breaths at a high rate from being counted as effective ventilation. The anatomical deadspace is set manually.
Clinical Procedure
The clinical procedure is to learn the target ventilation and backup rate while the patient is awake. Then a target ventilation ramp and EPAP is set. Then possibly adjust the maximum inspiratory fraction and the cycling threshold, which is a proportion of the peak flow. A default value is 25%.
Jamming Jamming is a state in which there exists a change in a leak that has not been fully compensated for. The presence of a leak can change the flow so that it doesn't get close to its zero crossing points at which the transition from inspiration to expiration is usually recognized. Thus if the pressure is adjusted to switch from inspiration to expiration at such a zero crossing point, the change will not be recognized and the pressure will remained "jammed" in one phase. However the low pass filtered flow should oscillate around a base line that can be recognized as the new criteria for the phase change.
The jamming index J is related to leak flow by the formula:
Jkj + Q.- J)kSτjpmaΛ = Qleak , where J=O indicates a stable leak through some orifice and J=1 a sudden leak.
When jamming is observed, i.e. a rapid change of leak, the system suspends changes in pressure support. Otherwise the pressure support is adjusted automatically.

Claims

What is claimed is:
1. A method for determining the amount of leak in a CPAP system controlled by timers, comprising determining the length of a time interval at least as long as a single breath, integrating airflow over a preceding time interval as long as said time interval, omitting said integration over said interval when a jamming index indicates that the leak has suddenly increased, until a measure of leak variation ceases to indicate a rapid rate of change, determining the amount of leak as a function of said integration.
2. A method for determining the airflow in a CPAP system controlled by timers, comprising setting cycling thresholds that vary with time, determining a breath phase from the cycling thresholds, looking backwards in time for a phase equal to the current phase, determining the length of a time interval at least as long as that between equal phase points, integrating airflow over a preceding time interval as long as said time interval.
3. The method for determining the airflow in a CPAP system controlled by timers of claim 2, further comprising omitting said integration over said interval when a jamming index indicates that the leak has suddenly increased, until a measure of leak variation ceases to indicate a rapid rate of change, correcting said airflow by the amount of leak as a function of said integration.
4. A CPAP system controlled by timers, comprising a controller for determining the length of a time interval at least as long as a single breath, integrating airflow over a preceding time interval as long as said time interval, omitting said integration over said interval when a jamming index indicates that the leak has suddenly increased, until a measure of leak variation ceases to indicate a rapid rate of change, 5. determining the amount of leak as a function of said integration.
5. A CPAP system controlled by timers, comprising a controller for setting cycling thresholds that vary with time, determining a breath phase from the cycling thresholds, 0 looking backwards in time for a phase equal to the current phase, determining the length of a time interval at least as long as that between equal phase points, integrating airflow over a preceding time interval as long as said time interval. 5
6. The CPAP system controlled by timers of claim 5, further comprising omitting said integration over said interval when a jamming index indicates that the leak has suddenly increased, until a measure of leak variation ceases to indicate a rapid rate of change, correcting said airflow by the amount of leak as a function of said integration.0
7. The CPAP system controlled by timers of claim 5, in which, when jamming is present suspends changes in pressure support.
8. A method of determining an air leak flow rate from a respiratory device5 connected to a patient breathing in breathing cycles, the method comprising the steps of:
(i) measuring a flow rate of air from the respiratory device; (ii) determining a duration of a breathing cycle; (iii) calculating an average of the flow rate of air over a period at least equal to said duration;
(iv) determining the air leak flow rate to be the difference between said air flow rate and said average.
9. The method of claim 8 wherein said flow rate of air is measured continuously.
10. The method of claim 8 wherein said determining of a duration of a breathing cycle is determined continuously.
11. The method of claim 8 wherein said calculating an average of the flow rate of air is calculated continuously.
12. The method of claim 8 wherein said calculating an average of the flow rate of air is calculated from a mid-inspiratory point of a first breathing cycle to a mid- inspiratory point of a second breathing cycle.
13. The method of claim 8 wherein said calculating an average of the flow rate of air is calculated from a mid-expiratory point of a first breathing cycle to a mid-, expiratory point of a second breathing cycle.
14. The method of claim 12 or 13 wherein said second breathing cycle is adjacent said first breathing cycle.
15. The method of claim 8 further comprising the step of determining whether the air leak flow rate is rapidly changing.
16. The method of claim 8 without further comprising the step of determining a transition point from inspiration to expiration.
17. The method of claim 8 without further comprising the step of determining a transition point from expiration to inspiration.
18. A method of determining an air leak flow rate at a first point in time from a respiratory device connected to a patient breathing in breathing cycles, the method comprising the steps of: (i) determining a flow rate of air from the respiratory device;
(ii) determining a phase function of the breathing cycle the patient; (iii) determining a duration of the breathing cycle;
(iv) selecting a second point in said function of phase corresponding to the first point in time in a previous breath; (v) integrating the flow rate between said first and second points;
(vi) determining said leak flow rate by comparing said flow rate of air and the result of said integration.
19. The method of claim 18 wherein said phase function is a discontinuous function.
20. A method of determining an air leak flow rate at a first point in time from a respiratory device connected to a patient breathing in breathing cycles comprising the steps of: (i) determining a flow rate of air at said first time point;
(ii) determining a first phase value in the respiration cycle of the patient corresponding to said first point in time; (iii) determining a second point in a prior respiration cycle when the respiration was at approximately the same phase value as said first phase value;
(iv) calculating an average flow rate over the interval between said first and second points; (v) determining the leak flow by comparing said flow rate and said average flow rate.
21. A method of providing pressure support to a patient comprising the steps of: (i) determining a leak flow rate; (ii) determining whether a leak flow rate is rapidly changing;
(iii) determining a level of pressure support;
(iv) providing said level of pressure support to the patient;
(v) maintaining substantially the same level of pressure support if the leak flow rate is rapidly changing.
22. A respiratory device for connection to a patient breathing in cycles, including a controller for:
(i) measuring a flow rate of air from the respiratory device;
(ii) determining a duration of a breathing cycle; (iii) calculating an average of the flow rate of air over a period at least equal to said duration;
(iv) determining the air leak flow rate to be the difference between said air flow rate and said average.
23. A respiratory device for connection to a patient breathing in cycles, including a controller for determining an air leak flow rate at a first point in time from the respiratory device by
(i) determining a flow rate of air from the respiratory device; (ii) determining a phase function of the breathing cycle the patient; (iii) determining a duration of the breathing cycle; (iv) selecting a second point in said function of phase corresponding to the first point in time in a previous breath; (v) integrating the flow rate between said first and second points; and
(vi) determining said leak flow rate by comparing said flow rate of air and the result of said integration.
24. A respiratory device for connection to a patient breathing in cycles, including a controller for determining an air leak flow rate at a first point in time from the respiratory device by.
(i) determining a flow rate of air at said first time point; (ii) determining a first phase value in the respiration cycle of the patient corresponding to said first point in time; (iii) determining a second point in a prior respiration cycle when the respiration was at approximately the same phase value as said first phase value;
(iv) calculating an average flow rate over the interval between said first and second points; and
(v) determining the leak flow by comparing said flow rate and said average flow rate.
25. Apparatus for providing pressure support to a patient, comprising a controller for:
(i) determining a leak flow rate; (ii) determining whether a leak flow rate is rapidly changing;
(iii) determining a level of pressure support; (iv) providing said level of pressure support to the patient; (v) maintaining substantially the same level of pressure support if the leak flow rate is rapidly changing.
PCT/AU2007/001255 2006-08-30 2007-08-30 Determination of leak during cpap treatment WO2008025079A1 (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010085895A3 (en) * 2009-01-29 2010-12-16 Yrt Limited A method for estimating leaks from ventilator circuits
EP2337602B1 (en) * 2008-10-16 2019-09-25 Koninklijke Philips N.V. Ventilator with limp mode
US11266801B2 (en) 2015-10-09 2022-03-08 University Of Utah Research Foundation Ventilation devices and systems and methods of using same

Families Citing this family (34)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AUPO163896A0 (en) * 1996-08-14 1996-09-05 Resmed Limited Determination of respiratory airflow
CN101541366B (en) * 2006-08-30 2013-07-17 雷斯梅德有限公司 Determination of leak during CPAP treatment
US8267085B2 (en) 2009-03-20 2012-09-18 Nellcor Puritan Bennett Llc Leak-compensated proportional assist ventilation
US8272379B2 (en) 2008-03-31 2012-09-25 Nellcor Puritan Bennett, Llc Leak-compensated flow triggering and cycling in medical ventilators
EP2313138B1 (en) 2008-03-31 2018-09-12 Covidien LP System and method for determining ventilator leakage during stable periods within a breath
US8746248B2 (en) 2008-03-31 2014-06-10 Covidien Lp Determination of patient circuit disconnect in leak-compensated ventilatory support
US8424521B2 (en) 2009-02-27 2013-04-23 Covidien Lp Leak-compensated respiratory mechanics estimation in medical ventilators
US8418691B2 (en) 2009-03-20 2013-04-16 Covidien Lp Leak-compensated pressure regulated volume control ventilation
WO2010121313A1 (en) 2009-04-22 2010-10-28 Resmed Ltd Detection of asynchrony
EP2590702B1 (en) * 2010-07-09 2014-05-14 Koninklijke Philips N.V. Leak estimation using leak model identification
US9272111B2 (en) 2010-07-27 2016-03-01 Koninklijke Philips N.V. Leak estimation using function estimation
CN103180002B (en) * 2010-07-30 2016-10-19 瑞思迈有限公司 Leakage detection method and equipment
CN103182120B (en) * 2011-12-30 2016-06-15 北京谊安医疗系统股份有限公司 Invasive respirator is the device of man-machine synchronization under noninvasive ventilation mode
US9498589B2 (en) 2011-12-31 2016-11-22 Covidien Lp Methods and systems for adaptive base flow and leak compensation
EP2816952B1 (en) * 2012-02-20 2022-08-03 University of Florida Research Foundation, Inc. Method and apparatus for predicting work of breathing
CN104302338B (en) * 2012-04-13 2018-02-16 瑞思迈有限公司 Apparatus and method for ventilation therapy
WO2014068000A1 (en) * 2012-10-31 2014-05-08 Maquet Critical Care Ab A Breathing Apparatus and a Method therein
US10493223B2 (en) * 2013-06-19 2019-12-03 Koninklijke Philips N.V. Determining of subject zero flow using cluster analysis
JP6863740B2 (en) 2013-07-01 2021-04-21 レスメド・プロプライエタリー・リミテッド Respiratory motor drive system
US20150081448A1 (en) * 2013-09-16 2015-03-19 Microsoft Corporation Non-intrusive advertisement management
US9675771B2 (en) 2013-10-18 2017-06-13 Covidien Lp Methods and systems for leak estimation
JP6331456B2 (en) * 2014-02-20 2018-05-30 コニカミノルタ株式会社 Information processing system and program
CN104874067B (en) * 2014-02-28 2018-09-11 北京谊安医疗系统股份有限公司 Leakage detection method for lung ventilator
CN103977494B (en) * 2014-05-29 2016-07-20 北京航空航天大学 A kind of method controlling ventilation air leakage based on flow waveform estimated pressure
CN104771818B (en) * 2015-03-02 2017-03-01 深圳市科曼医疗设备有限公司 Per nasal pressure generator self-adapting calibration system and method
CN111603643B (en) 2015-04-02 2023-05-23 希尔-罗姆服务私人有限公司 Pressure control of breathing apparatus
EP3319672A1 (en) * 2015-07-07 2018-05-16 Koninklijke Philips N.V. Methods and systems for patient airway and leak flow estimation for non-invasive ventilation
DE102015216895A1 (en) * 2015-09-03 2017-03-09 Hamilton Medical Ag Ventilation device with error detection for flow sensors
CN106730208B (en) * 2017-01-18 2020-05-15 湖南明康中锦医疗科技发展有限公司 Method for adaptively adjusting air leakage and breathing machine
EP3697484B1 (en) 2017-10-18 2023-05-31 Resmed Pty Ltd Respiratory apparatus with multiple power supplies
US11478594B2 (en) * 2018-05-14 2022-10-25 Covidien Lp Systems and methods for respiratory effort detection utilizing signal distortion
CN112156297A (en) * 2018-10-26 2021-01-01 北京怡和嘉业医疗科技股份有限公司 Ventilation treatment equipment and control method
CN111184932B (en) * 2019-12-02 2022-09-02 湖南明康中锦医疗科技发展有限公司 Method for detecting air leakage of respiratory support equipment and respiratory support equipment
CN110975090A (en) * 2019-12-20 2020-04-10 广州和普乐健康科技有限公司 Breathing machine air leakage calculation method and device, storage medium and computer equipment

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6152129A (en) * 1996-08-14 2000-11-28 Resmed Limited Determination of leak and respiratory airflow
EP1005829B1 (en) * 1996-09-23 2003-04-23 Resmed Limited Assisted ventilation to match patient respiratory need
WO2005051470A1 (en) * 2003-11-26 2005-06-09 Resmed Limited Macro-control of treatment for sleep disordered breathing
WO2006000017A1 (en) * 2004-06-23 2006-01-05 Resmed Limited Methods and apparatus with improved ventilatory support cycling
EP0714670B1 (en) * 1994-12-02 2006-03-22 Respironics Inc. Breathing gas delivery apparatus

Family Cites Families (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5490502A (en) * 1992-05-07 1996-02-13 New York University Method and apparatus for optimizing the continuous positive airway pressure for treating obstructive sleep apnea
EP2113196A3 (en) * 1993-11-05 2009-12-23 ResMed Limited Control of CPAP treatment
US6932084B2 (en) * 1994-06-03 2005-08-23 Ric Investments, Inc. Method and apparatus for providing positive airway pressure to a patient
US6105575A (en) * 1994-06-03 2000-08-22 Respironics, Inc. Method and apparatus for providing positive airway pressure to a patient
AU737302B2 (en) * 1996-09-23 2001-08-16 Resmed Limited Determination of instantaneous inspired volume
WO2000041757A1 (en) * 1999-01-15 2000-07-20 Resmed Limited Method and apparatus to counterbalance intrinsic positive end expiratory pressure
US6910480B1 (en) * 1999-09-15 2005-06-28 Resmed Ltd. Patient-ventilator synchronization using dual phase sensors
US6761165B2 (en) * 2000-02-29 2004-07-13 The Uab Research Foundation Medical ventilator system
US6553992B1 (en) * 2000-03-03 2003-04-29 Resmed Ltd. Adjustment of ventilator pressure-time profile to balance comfort and effectiveness
DE10023473A1 (en) * 2000-05-10 2001-12-06 Peter Schaller Correcting leak volume flow in respiration or diagnostic system by determining average pressure and volume flow and calculating corrected volume flow
US6752151B2 (en) * 2000-09-25 2004-06-22 Respironics, Inc. Method and apparatus for providing variable positive airway pressure
US6546930B1 (en) * 2000-09-29 2003-04-15 Mallinckrodt Inc. Bi-level flow generator with manual standard leak adjustment
CN1767785B (en) * 2003-01-30 2015-08-26 康普麦迪克斯有限公司 For the algorithm of automatic positive air pressure titration
EP1605999A1 (en) * 2003-03-24 2005-12-21 Weinmann Geräte für Medizin GmbH & Co. KG Method and device for detecting leaks in respiratory gas supply systems
SE0401208D0 (en) * 2004-05-10 2004-05-10 Breas Medical Ab Multilevel fan
US7717110B2 (en) * 2004-10-01 2010-05-18 Ric Investments, Llc Method and apparatus for treating Cheyne-Stokes respiration
US7487774B2 (en) * 2005-08-05 2009-02-10 The General Electric Company Adaptive patient trigger threshold detection
CN101541366B (en) * 2006-08-30 2013-07-17 雷斯梅德有限公司 Determination of leak during CPAP treatment
WO2013098686A1 (en) * 2011-12-27 2013-07-04 Koninklijke Philips Electronics N.V. Compensation of breath delivery

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0714670B1 (en) * 1994-12-02 2006-03-22 Respironics Inc. Breathing gas delivery apparatus
US6152129A (en) * 1996-08-14 2000-11-28 Resmed Limited Determination of leak and respiratory airflow
EP1005829B1 (en) * 1996-09-23 2003-04-23 Resmed Limited Assisted ventilation to match patient respiratory need
WO2005051470A1 (en) * 2003-11-26 2005-06-09 Resmed Limited Macro-control of treatment for sleep disordered breathing
WO2006000017A1 (en) * 2004-06-23 2006-01-05 Resmed Limited Methods and apparatus with improved ventilatory support cycling

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2337602B1 (en) * 2008-10-16 2019-09-25 Koninklijke Philips N.V. Ventilator with limp mode
WO2010085895A3 (en) * 2009-01-29 2010-12-16 Yrt Limited A method for estimating leaks from ventilator circuits
US8910633B2 (en) 2009-01-29 2014-12-16 Yrt Limited Method for estimating leaks from ventilator circuits
US11266801B2 (en) 2015-10-09 2022-03-08 University Of Utah Research Foundation Ventilation devices and systems and methods of using same

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