Determination of airway resistance and lung compliance

摘要

A method and apparatus is disclosed for determining airway resistance and lung compliance using an electrical circuit model (36) wherein at least one component parameter is non-linear. The system (10) non-intrusively obtains pressure and flow data signals (20,24) from a pressure transducer (22) and a laminar flow element (18) without interrupting or interfering with normal breathing and gas supply to a patient (12). An invariant exponential is determined empirically based on physical characteristics (14) of the airway. The non-linear airway resistance and lung compliance can then be calculated based on the sensed flow rate, gas pressure, a calculated gas volume, and the invariant exponential using linear techniques. The resulting airway resistance can be normalized to a standard reporting flow rate value. The system is particularly useful in anesthesia applications, but is also useful in any breathing system where fresh gas is supplied constantly from a gas source other than a ventilator. <IMAGE>