Validation of a Proposed Algorithm for Assistance Titration During Proportional Assist Ventilation With Load-Adjustable Gain Factors

Abstract

Background: The present study aimed to validate a recently proposed algorithm for assistance titration during proportional assist ventilation with load-adjustable gain factors, based on a noninvasive estimation of maximum inspiratory pressure (peak P_mus) and inspiratory effort (pressure-time product [PTP] peak P_mus).

Methods: Retrospective analysis of the recordings obtained from 26 subjects ventilated on proportional assist ventilation with load-adjustable gain factors under different conditions, each considered as an experimental case. The estimated inspiratory output (peak P_mus) and effort (PTP-peak P_mus) were compared with the actual-determined by the measurement of transdiaphragmatic pressure- and the derived PTP. Validation of the algorithm was performed by assessing the accuracy of peak P_mus in predicting the actual inspiratory muscle effort and indicating the appropriate level of assist.

Results: In the 63 experimental cases analyzed, a limited agreement was observed between the estimated and the actual inspiratory muscle pressure (-11 to 10 cm H₂O) and effort (-82 to 125 cm H₂O × s/min). The sensitivity and specificity of peak P_mus to predict the range of the actual inspiratory effort was 81.2% and 58.1%, respectively. In 49% of experimental cases, the level of assist indicated by the algorithm differed from that indicated by the transdiaphragmatic pressure and PTP.

Conclusions: The proposed algorithm had limited accuracy in estimating inspiratory muscle effort and with indicating the appropriate level of assist.

Keywords: assistance; inspiratory muscles output; proportional assist ventilation; titration.