Monitoring of ventilation and lung mechanics during automatic ventilation. A new device.

A device that allows continuous monitoring and recording of expired minute volume, tidal volume, resistance, compliance, indices of hyperinflation and other measures of ventilation and lung mechanics during automatic ventilation is described. After connection to the ventilator (Servoventilator 900) with one cable it is operating without any calibrations or other measures. The calculation of expired minute volume is done in a new way that eliminates errors due to compression of gas in the connecting lines. Calculations of compliance is made in a way allowing measurements even in patients with hyperinflation. Expiratory and inspiratory resistance values are obtained. The indices of hyperinflation in terms of measured flow and estimated alveolar pressure at the end of an expiration are discussed. The problems and benefits associated with measurements in much obstructive patients are analyzed. A short study of the performance of the calculator is presented.