A respiratory jacket for ventilatory measurements in children.

The properties of an air-filled polyurethane-coated nylon jacket for measuring volume parameters were determined on a model and in 13 subjects. There was a linear relationship between jacket pressure on a logarithmic scale and the lung volume change over an operating pressure range of 0.7-6 cmH2O. The magnitude of pressure change was frequency dependent. The magnitude of a calibration signal was reduced by superimposed tidal breathing. For the jacket tested, the calibration signal during tidal breathing was 87% of the calibration during apnea. With these properties established, a calibration technique was devised and tested on 13 infants. Corrected tidal volumes (VT) obtained with the jacket correlated well with those obtained with a pneumotachograph (r = 0.986). At the operating pressures used the jacket caused no significant change in functional residual capacity (FRC), VT, or frequency. The jacket is a reliable technique for measurement of VT and immediate changes in FRC in awake children.