Transpulmonary Pressure-Guided Lung-Protective Ventilation Improves Pulmonary Mechanics and Oxygenation Among Obese Subjects on Mechanical Ventilation

Abstract

BACKGROUND:

Transpulmonary pressure (P_L) is used to assess pulmonary mechanics and guide lung-protective mechanical ventilation (LPV). P_L is recommended to individualize LPV settings for patients with high pleural pressures and hypoxemia. We aimed to determine whether P_L-guided LPV settings, pulmonary mechanics, and oxygenation improve and differ from non-P_L-guided LPV among obese patients after 24 h on mechanical ventilation. Secondary outcomes included classification of hypoxemia severity, count of ventilator-free days, ICU length of stay, and overall ICU mortality.

METHODS:

This is a retrospective analysis of data. Ventilator settings, pulmonary mechanics, and oxygenation were recorded on the initial day of P_L measurement and 24 h later. P_L-guided LPV targeted inspiratory P_L < 20 cm H₂O and expiratory P_L of 0–6 cm H₂O. Comparisons were made to repeat measurements.

RESULTS:

Twenty subjects (13 male) with median age of 49 y, body mass index 47.5 kg/m², and SOFA score of 8 were included in our analysis. Fourteen subjects received care in a medical ICU. P_L measurement occurred 16 h after initiating non-P_L-guided LPV. P_L-guided LPV resulted in higher median PEEP (14 vs 18 cm H₂O, P = .009), expiratory P_L (–3 vs 1 cm H₂O, P = .02), respiratory system compliance (30.7 vs 44.6 mL/cm H₂O, P = .001), and ${\mathbf{\text{P}}}_{{\mathbf{\text{aO}}}_{\mathbf{\text{2}}}}{\mathbf{\text{/F}}}_{{\mathbf{\text{IO}}}_{\mathbf{\text{2}}}}$ (156 vs 240 mm Hg, P = .002) at 24 h. P_L-guided LPV resulted in lower ${\mathbf{\text{F}}}_{{\mathbf{\text{IO}}}_{\mathbf{\text{2}}}}$ (0.53 vs 0.33, P < .001) and lower P_L driving pressure (10 vs 6 cm H₂O, P = .001). Tidal volume (420 vs 435 mL, P = .64) and inspiratory P_L (7 vs 7 cm H₂O, P = .90) were similar. Subjects had a median of 7 ventilator-free days, and median ICU length of stay was 14 d. Three of 20 subjects died within 28 d after ICU admission.

CONCLUSIONS:

P_L-guided LPV resulted in higher PEEP, lower ${\mathbf{\text{F}}}_{{\mathbf{\text{IO}}}_{\mathbf{\text{2}}}}$ , improved pulmonary mechanics, and greater oxygenation when compared to non-P_L-guided LPV settings in adult obese subjects.