Benites, Martín HernánBihari, ShaileshBattiato, RominaBruhn, AlejandroBugedo, GuillermoCosta, Eduardo L. V.Dellamonica, JeanGuérin, ClaudeLanger, ThomasMarini, John J.Marrazo, FrancescoMezidi, MehdiSelickman, JohnWiersema, Ubbo F.Retamal, Jaime2025-11-072025-11-072025Critical Care, Vol. 29, N°457 (2025) p. 1-11.1364-8535https://hdl.handle.net/20.500.12254/7351Background Adjusting trunk inclination in patients with acute respiratory distress syndrome directly affects physiological variables such as respiratory mechanics and PaCO2 levels. These effects may vary according to the body mass index (BMI) due to differences in lung and chest wall mechanics, highlighting the need for further investigation to clarify the clinical relevance of body position across patient subgroups. Methods A secondary analysis compared the physiological effects of increasing trunk inclination angles between mechanically ventilated patients with obesity (BMI ≥ 30 kg/m2) and those without obesity (BMI < 30 kg/m2). Results Data from 159 patients collected across seven individual studies were analyzed. The following physiological changes were observed in response to increased trunk inclination: Sixty-five patients with obesity presented a greater decrease in respiratory system compliance (-7.5 [-10; -5] mL/cmH2O; p < 0.001) compared to ninety-four patients without obesity (-3.5 [-7; -0.08] mL/cmH2O; p = 0.045). Lung compliance decreased in obese patients (-7.8 [-12.4; -3.3] mL/cmH2O; p < 0.001), whereas no significant changes were observed in patients without obesity (-5.9 [-14.2; 2.3] mL/cmH2O; p = 0.160). Chest wall compliance decreased by -42.9 [-63.2; -22.6] mL/cmH2O (p < 0.001) in obese patients and by -47.7 [-95.3; -0.15] mL/cmH2O in non-obese patients (p = 0.049). PaCO2 increased in obese patients by 4.6 [1.4; 7.8] mmHg (p = 0.004) but not in patients without obesity (2.5 [-0.6; 5.6] (p = 0.113). No significant differences were observed in PaO2/FIO2 between phases.enAtribución-NoComercial-CompartirIgual 3.0 Chile (CC BY-NC-SA 3.0 CL)Body positionSupine positionCompliance of respiratory systemObeseArticlehttps://orcid.org/0000-0001-6366-534Xhttps://doi.org/10.1186/s13054-025-05694-z