Transpulmonary Pressure-Guided Lung Protective Ventilation Improves Pulmonary Mechanics and Oxygenation in Adult Obese Patients

Abstract

Background: Transpulmonary pressure (PL) manometry is used to assess pulmonary mechanics and guide lung protective mechanical ventilation (LPV). PL manometry is recommended to individualize LPV settings for patients with increased chest wall elastance and hypoxemia. Our primary aim was to determine if non-PL guided LPV settings, pulmonary mechanics, and oxygenation differ 1-day after receiving PL guided LPV among obese mechanically ventilated (MV) patients. Secondary endpoints: Ventilator-free days (VFD), ICU length of stay (LOS), and overall ICU mortality..

Methods: This was an IRB approved retrospective analysis of prospectively collected quality improvement data from MV adult obese patients. All patients were MV for a period prior to placement of an esophageal balloon catheter. Ventilator settings, pulmonary mechanics, and oxygenation were recorded on the initial day of PL measurement (D1, non-PL guided LPV). PL guided LPV targeted Inspiratory PL < 20 cm H₂O and expiratory PL 0-6 cm H₂O. PEEP was adjusted according to a FIO₂/PL Table. Comparisons were made to repeat measurements done on day 2 (D2, PL guided LPV). Hypoxemia severity was also compared. Data reported as n (%) and median (IQR). Alpha set at .05.

Results: 19 patients (63% male) with median age 49 (40-65) y, BMI 46.3 (36.6-55.9) kg/m2, and SOFA score 8 (6-11) were included in our sample. 13 (68%) patients received care in the medical ICU and 6 (32%) in our surgical/trauma ICU. PL measurement occurred 16 (9-21) h after initiating non-PL guided LPV in an effort to optimize ventilator settings. PL guided LPV resulted in higher PEEP [14 (14-20) vs 18 (17-25)], P <.01), Expiratory PL [-3 (-5 to -1) vs 1 (0 to 3), P <.01], Crs [30 (26-42) vs 43 (37-51), P <.01], and PaO₂/FIO₂ [165 (106-193) vs 246 (204-286), P <.01] at D2. PL guided LPV resulted in lower FIO₂ [.60 (.40-.90) vs .30 (.30-.40), P <.01)] and lower Driving Pressure [14 (10-15) vs 10 (8-11), P =.01]. V_T [420 (360-457)] vs 435 (363-463) mL, P =.64) and Inspiratory PL [7 (2-11) vs 8 (5-10), P =.55) were similar. Hypoxemia was lower after PL guided ventilator setting adjustment (Table). VFD ranged from 2-28 [8 (6-12)] d and ICU LOS was 17 (11-27) d. ICU mortality was 11% (n=2/19).

Conclusions: PL guided LPV results in higher PEEP, lower FIO₂, improved pulmonary mechanics, and greater oxygenation when compared to non-PL guided LPV MV settings in adult obese patients. Future studies should evaluate early PL guided LPV among obese pts and the effect on VFD, ICU LOS, and ICU mortality.

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