Estimation of occlusion pressure during assisted ventilation in patients with intrinsic PEEP

We conducted a study to assess the validity of the occlusion pressure (P-0.1) measured during activation of the trigger mechanism (P(0.1)aw(trig)) in patients showing variable levels of PEEPi during pressure-support ventilation. We first compared P(0.1)aw(trig) and P-0.1 measured with the conventional method (i.e., the airway pressure drop after the first 100 ms of an occluded inspiration) in 16 patients with chronic obstructive pulmonary disease (COPD). We observed good agreement and a highly significant correlation (r = 0.99; bias = 0.3 +/- 0.5 cm H2O) between the two methods. In a second part of the study, we compared, in 17 patients, P(0.1)aw(trig) with (P(0.1)es), measured as the depression generated on the esophageal pressure tracing in the first 100 ms of the inspiratory negative swing, and with P-0.1 measured on the Pes tracing simultaneously with Paw(trig) (P(0.1)es-synchro). Our results showed a good correlation and good agreement between Paw(trig) and P(0.1)es (r = 0.92; bias = 0.3 +/- 0.5 cm H2O); Paw(trig) and P(0.1)es-synchro (r = 0.97; bias = 0.1 +/- 0.2 cm H2O); and P(0.1)es and P(0.1)es-synchro (r = 0.95, bias = 0.2 +/- 0.4 cm H2O), respectively. This study suggests that reliable measurements of inspiratory drive can be obtained easily, on a breath-by-breath basis, from airway pressure tracings during pres- sure-support ventilation in patients with variable levels of PEEPi.