Method and apparatus to counterbalance intrinsic positive end expiratory pressure
First Claim
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1. A method for preventing dynamic airway compression during ventilatory support of a patient, comprising the steps of:
- providing an interface to the patient'"'"'s airway, providing said interface with a supply of breathable gas at a controllable pressure and with an exhaust, providing a device for measuring respiratory airflow;
providing a device for calculating respiratory airflow and deriving a measure of the degree of dynamic airway compression;
determining respiratory airflow by way of measurement and calculation, varying the pressure at the patient interface so as to provide ventilatory support to the patient, from at least the determined respiratory airflow, deriving a measure of the degree of dynamic airway compression, and servo-controlling the measure of the degree of dynamic airway compression by increasing expiratory pressure if said measure is large or increasing, and reducing expiratory pressure if said measure is small or zero, wherein said measure of the degree of dynamic airway compression is derived by analysis of the shape of the expiratory airflow versus time curve.
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Abstract
The invention prevents dynamic airway compression during ventilatory support of a patient. The respiratory airflow is determined by measurement or calculation, and a measure of the degree of dynamic airway compression is derived from the determined airflow. This measure is servo-controlled to be zero by increasing expiratory pressure if the measure of the degree of dynamic airway compression is large or increasing, and by reducing expiratory pressure if the measure of the degree of dynamic airway compression is small or zero.
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Citations
24 Claims
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1. A method for preventing dynamic airway compression during ventilatory support of a patient, comprising the steps of:
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providing an interface to the patient'"'"'s airway, providing said interface with a supply of breathable gas at a controllable pressure and with an exhaust, providing a device for measuring respiratory airflow;
providing a device for calculating respiratory airflow and deriving a measure of the degree of dynamic airway compression;
determining respiratory airflow by way of measurement and calculation, varying the pressure at the patient interface so as to provide ventilatory support to the patient, from at least the determined respiratory airflow, deriving a measure of the degree of dynamic airway compression, and servo-controlling the measure of the degree of dynamic airway compression by increasing expiratory pressure if said measure is large or increasing, and reducing expiratory pressure if said measure is small or zero, wherein said measure of the degree of dynamic airway compression is derived by analysis of the shape of the expiratory airflow versus time curve. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for preventing dynamic airway compression during ventilatory support of a patent, comprising the steps of:
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providing a variable pressure device to supply pressure to the patient'"'"'s airway so as to provide ventilatory support, providing an apparatus for determining respiratory airflow and deriving a measure of the degree of dynamic airway compression;
determining the patent'"'"'s respiratory airflow, deriving a measure of the degree of dynamic airway compression as a function of the determined respiratory airflow by measuring the patient'"'"'s airway conductance separately during the inspiratory and expiratory portions of at least one respiratory cycle, and increasing or decreasing expiratory pressure in accordance with the derived measure of the degree of dynamic airway compression, wherein the measure of the degree of dynamic airway conductance is calculated as a function of the difference between the inspiratory conductance and the expiratory conductance. - View Dependent Claims (8, 9, 10, 11, 12)
superimposing a high-frequency oscillation on the variable pressure provided to the patient'"'"'s airway, identifying the inspiratory and expiratory portions of each respiratory cycle, measuring the component of the respiratory airflow at said high frequency, separately over the inspiratory and expiratory portions of at least one respiratory cycle, and calculating the inspiratory and expiratory airway conductances from the high-frequency component airflow measurements.
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13. An apparatus for determining a pressure response to ameliorate dynamic airway compression during ventilatory support comprising:
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an interface to a patient'"'"'s airway and an exhaust, a means for supplying breathable gas at a controllable pressure to the interface, a means for deriving an airflow signal from said interface, and a controller means with programming instructions for;
(a) controlling a variation of the pressure at the interface to provide ventilatory support to the patient;
(b) controlling a determination of a measure of a degree of dynamic airway compression at least from calculated data representing the airflow signal; and
(c) servo-controlling the measure of the degree of dynamic airway compression by increasing the controllable pressure during expiration if the measure of the degree of dynamic airway compression is large or increasing, and decreasing the controllable pressure during expiration if the measure of the degree of dynamic airway compression is small or zero, wherein said measure of the degree of dynamic airway compression is derived by analysis of the shape of the expiratory airflow versus time curve. - View Dependent Claims (14, 15, 16, 17, 18)
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19. An apparatus for determining a pressure response to ameliorate dynamic airway compression during ventilation support comprising:
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an interface to a patient'"'"'s airway and an exhaust, a means for supplying breathable gas at a controllable pressure to the interface, a transducer for determining an airflow signal from said interface, and a processor with programmed instructions for controlling;
(a) variation of the pressure at the interface to provide ventilatory support to the patient;
(b) a determination of a measure of a degree of dynamic airway compression as a function of data representing the airflow by measuring airway conductance separately during inspiratory and expiratory portions of at least one respiratory cycle; and
(c) increasing or decreasing expiratory pressure in accordance with the derived measure of the degree of dynamic airway compression, wherein the measure of the degree of dynamic airway conductance is calculated as a function of the difference between the inspiratory conductance and the expiratory conductance. - View Dependent Claims (20, 21, 22, 23, 24)
superimposing a high-frequency oscillation on the variable pressure provided to the patient'"'"'s airway, identifying the inspiratory and expiratory portions of each respiratory cycle, measuring the component of the respiratory airflow at said high frequency, separately over the inspiratory and expiratory portions of at least one respiratory cycle, and calculating the inspiratory and expiratory airway conductances from the high-frequency component airflow measurements.
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Specification