Estimating actual inspiratory muscle pressure from airway occlusion pressure at 100 msec

Background: Quantification of the patient’s respiratory effort during mechanical ventilation is very important, and calculating the actual muscle pressure (Pmus) during mechanical ventilation is a cumbersome task and usually requires an esophageal balloon manometry. Airway occlusion pressure at 100 milliseconds (P0.1) can easily be obtained non-invasively. There has been no study investigating the association between Pmus and P0.1. Therefore, we aimed to investigate whether P0.1 correlates to Pmus and can be used to estimate actual Pmus Materials and Methods: A bench study using lung simulator (ASL 5000) to simulate an active breathing patient with Pmus from 1 to 30 cmH2O by increments of 1 was conducted. Twenty active breaths were measured in each Pmus. The clinical scenario was constructed as a normal lung with a fixed setting of compliances of 60 mL/cmH2O and resistances of 10 cmH2O/l/sec. All experiments were conducted using the pressure support ventilation mode (PSV) on a Hamilton-G5 ventilator (Hamilton Medical AG, Switzerland), Puritan Bennett 840TM (Covidien-Nellcor, CA) and Avea (CareFusion, CA). Main results: There was significant correlation between P 0.1 and Pmus (correlation coefficient = - 0.992, 95% CI: - 0.995 to -0.988, P-value<0.001). The equation was calculated as follows: Pmus = -2.99 x (P0.1) + 0.53 Conclusion: Estimation of Pmus using P 0.1 as a substitute is feasible, available, and reliable. Estimation of Pmus has multiple implications, especially in weaning of mechanical ventilation, adjusting ventilator support, and calculating respiratory mechanics during invasive mechanical ventilation. Keywords: P 0.1, Inspiratory occlusion pressure, WOB, Esophageal balloon, mechanical ventilators, respiratory failure Keywords: P 0.1, P mus, Inspiratory occlusion pressure, WOB, Esophageal balloon, mechanical ventilators, respiratory failure