Applying the Allan Variance to the Analysis of Errors of the Expiration Volume Measurement Channel of Mechanical Lung Ventilators

Abstract

The expiration volume measurement channel of a mechanical lung ventilator operating at a low rate of gas mixture flow is considered. The channel components are described in detail. The importance of accurate measurement of gas flow at low rates of mechanical ventilation (especially in neonatal medicine) is substantiated. The Allan variance is suggested as a statistical tool for analyzing the measurement channel errors. The obtained Allan variances, their approximations as sums of exponential functions, and estimates of power spectrum density coefficients of zero-signal noise are presented. The obtained estimates of the main components of the channel error are compared with the parameters of the electronic components used in the measurements. Preliminary recommendations for reduction of errors of the volume measurement channel are given.