Airway Occlusion Pressure and P0.1 to Estimate Inspiratory Effort and Respiratory Drive in Ventilated Children

OBJECTIVE: To compare the level of agreement between proximal (near the subject) and distal (inside the ventilator) measured airway occlusion pressure at 100 ms (P0.1) and occlusion pressure (Δ Pocc ), and to study the correlation between Δ Pocc and peak-to-trough esophageal pressure (Δ Pes ).

DESIGN: Secondary analysis of prospectively collected physiology dataset (2021-2022).

SETTING: Medical-surgical 20-bed PICU.

PATIENTS: Children younger than 18 years with and without acute lung injury ventilated greater than 24 hours and spontaneously breathing with appropriate triggering of the ventilator.

INTERVENTIONS: None.

MEASUREMENTS AND MAIN RESULTS: Data from three expiratory hold maneuvers (with a maximum of three breaths during each maneuver) in 74 subjects (118 measurements) with median age 3 months (interquartile range 1-17), and primary respiratory failure due to a pulmonary infection in 41/74 (55.4%) were studied. The median proximal ∆ Pocc was 6.7 cm H 2 O (3.1-10.7) and median P0.1 4.9 cm H 2 O (4.1-6.0) for the first breath from the maneuver; both increased significantly ( p < 0.001) with the subsequent two breaths during the same maneuver. Median distal ∆ Pocc was 6.8 (2.9-10.8) and P0.1 4.6 (3.9-5.6) cm H 2 O; both increased significantly ( p < 0.001) with the two subsequent breaths. Proximal and distal Δ Pocc ( r > 0.99, p < 0.001) and P0.1 ( r > 0.80, p < 0.001) were correlated. Correlation between ventilator displayed and Y-piece measured Δ Pocc ( r > 0.99) and P0.1 ( r = 0.85) was good. Mean ( sd ) difference for Δ Pocc was 0.13 (0.21); levels of agreement were -0.28 and 0.54. For P0.1, mean ( sd ) difference was -0.36 (1.14) and levels of agreement -2.61 and 1.88. There was a high correlation between Δ Pes and ∆ Pocc ( r = 0.92) for the same breath and a good correlation with Δ Pes from the preceding breath ( r = 0.76). There was a poor correlation with the transpulmonary pressure ( r = 0.37).

CONCLUSIONS: Δ Pocc is not affected by measurement site, whereas P0.1 may be overestimated or underestimated. Δ Pocc was highly correlated with the peak-to-trough esophageal pressure, supporting the concept that inspiratory effort can also be quantified noninvasively by measuring Δ Pocc .