A non-invasive system to evaluate diaphragmatic strength in ventilated patients

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Abstract
In this paper we describe a system that allows an indicator of diaphragmatic strength to be determined non-invasively in mechanically ventilated patients. The system is comprised of an occlusion device that can be incorporated into the ventilator tubing and an occlusion control unit to operate the occlusion. The system electronically coordinates the timing of airway occlusion at the mouthpiece, application of a magnetic phrenic nerve stimulus and rapid removal of the occlusion once the measurement has been made. The system therefore permits measurement of the change in airway pressure produced by a stimulated diaphragm contraction, without disconnection from the ventilator. Other important respiratory measurements such as twitch mouth pressure, simulated cough and P0.1 can also be performed on non-ventilated patients in a repeatable and systematic manner. Keywords: twitch mouth pressure, respiratory muscle strength, magnetic stimulation, ventilator weaning, simulated coughs, P0.1