Ralph James* & Pietro Scalfaro**
*Physics Department, University of Western Australia.
**Pediatric Intensive Care Unit, CHUV Lausanne, Switzerland.
The speed of sound in an ideal gas depends on its effective ratio of specific heats, the absolute temperature and the mean molecular mass. We have assessed the accuracy of molecular mass measurements with an ultrasonic time-of-flight flowmeter designed for use in infants. Pure and mixed gases were measured in static and dynamic (3 - 6 L/min) conditions. Analysis of responses to heavy gas washout trials were also used to determine the effectiveness of this method in estimating the tidal volume and functional residual capacity of infants. Potential applications of the techniques include direct measurement of the functional residual capacity of lungs.
Sonagrams of the human voice in air, He and N2O. This page contains some large images (6 x 200k)