Method and apparatus for determining patient lung pressure, compliance and resistance
First Claim
1. For use with a respirator system of the volume-compensated type in which a preselected volume of gas is delivered to a patient during an inspiration phase of the patient breathing cycle, apparatus for the determination of patient compliance and resistance comprising:
- control means operable to initiate computation and display of patient compliance and resistance;
means for sampling the system pressure at the end of the inspiration phase;
means included within said control means for ensuring a plateau phase, following the inspiration phase and preceeding an expiration phase, long enough to allow the system pressure to equalize with the patient lung pressure;
means for sampling the system pressure at the end of the plateau phase, to obtain a measure of the lung pressure at the end of the inspiration phase;
means for monitoring the actual volume of gas delivered to the patient; and
means for computing and displaying patient compliance, as derived from the monitored volume and the system pressure sampled at the end of the inspiration phase, and patient resistance, as derived from the monitored volume and the two sampled values of the system pressure.
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Abstract
A method and appartus for determining patient lung pressure, compliance and resistance, for use in conjunction with a respirator system of the compensated-volume type wherein a predetermined volume of gas is delivered to the patient in each breathing cycle. The method and apparatus of the invention determine both the system pressure at the point of delivery to the patient and the patient lung pressure, both at the end of the inspiration phase of the breathing cycle, and utilize these values, together with a compensated volume signal, to compute the values of patient compliance and resistance. Control circuitry, actuated periodically or on demand, substitutes an enforced plateau period following inspiration, to allow the system pressure to fall to the value of lung pressure which is obtained at the end of the inspiration phase, thereby permitting the measurement of lung pressure by sampling system pressure at the end of the plateau period. The control circuitry also controls analog-to-digital converters which convert the computed values of pressure, compliance and resistance for display in a digital display device.
67 Citations
13 Claims
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1. For use with a respirator system of the volume-compensated type in which a preselected volume of gas is delivered to a patient during an inspiration phase of the patient breathing cycle, apparatus for the determination of patient compliance and resistance comprising:
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control means operable to initiate computation and display of patient compliance and resistance; means for sampling the system pressure at the end of the inspiration phase; means included within said control means for ensuring a plateau phase, following the inspiration phase and preceeding an expiration phase, long enough to allow the system pressure to equalize with the patient lung pressure; means for sampling the system pressure at the end of the plateau phase, to obtain a measure of the lung pressure at the end of the inspiration phase; means for monitoring the actual volume of gas delivered to the patient; and means for computing and displaying patient compliance, as derived from the monitored volume and the system pressure sampled at the end of the inspiration phase, and patient resistance, as derived from the monitored volume and the two sampled values of the system pressure. - View Dependent Claims (2, 3, 4)
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5. A method for the determination of the compliance and resistance of a patient undergoing breathing therapy from a respirator system for the delivery of a preselected volume of gas to the patient during an inspiration phase of each breathing cycle, said method comprising the steps of:
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monitoring respirator system pressure during each breathing cycle, the breathing cycle including the inspiration phase, a plateau phase during which exhalation is prevented, and an expiration phase; sampling the system pressure at the end of the inspiration phase and at the end of the plateau phase, whereby the sampled system pressure at the end of the plateau phase is substantially equal to the patient lung pressure at the end of the inspiration phase; measuring a compensated volume of gas delivered to the patient during the inspiration phase; differentiating the compensated volume with respect to time; and computing the patient compliance and resistance from the measured compensated volume, its time differential and the sampled system pressure values. - View Dependent Claims (6, 7, 8, 9)
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10. Apparatus for use with a respirator system of the volume-compensated type in which a preselected volume of gas is delivered to a patient in each breathing cycle, the cylce having an inspiration phase, followed by a plateau phase during which exhalation is prevented, and an expiration phase, said apparatus being for the determination of patient compliance and resistance, and comprising:
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first electrical means for computing a respirator system pressure and a patient lung pressure both at the end of the inspiration phase of the breathing cycle, said first electrical means including means for ensuring a plateau phase long enough to allow the system and lung pressures to equalize, and means for sampling system pressure at the end of the inspiration phase and at the end of the plateau phase, whereby the system pressure at the end of the plateau phase is substantially equal to the lung pressure at the end of the inspiration phase; means for obtaining a measure of compensated volume of gas delivered to the patient during the inspiration phase; and second electrical means for computing patient compliance from the compensated volume and the system pressure at the end of the inspiration phase, and for computing the patient resistance from the compensated volume and the system and lung pressures at the end of the inspiration phase. - View Dependent Claims (11, 12, 13)
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Specification