The extensometer--use in spontaneously ventilating awake volunteers.

The extensometer is a new device with potential in the field of respiratory pattern analysis. This paper describes the physical principles upon which the extensometer depends and also assesses its performance as a noninvasive respiratory monitor in respect of its ability to measure tidal volume and to determine obstructive breathing patterns in awake volunteers in the supine position over a limited time period. Further developments of the device are outlined and the current status of torso transducers in anaesthesia and intensive care are discussed.