RESUMO
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 Pmus) and inspiratory effort (pressure-time product [PTP] peak Pmus). 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 Pmus) and effort (PTP-peak Pmus) 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 Pmus 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 Pmus 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.