Obesity: biomechanical implications for mechanical ventilation

Obesity is a highly prevalent chronic disease that profoundly affects respiratory physiology. Excess adipose tissue alters lung volumes, chest-wall mechanics, and pleural pressures, leading to airway closure, atelectasis, and ventilation-perfusion mismatch. These changes have important implications for mechanical ventilation in both perioperative and critical care settings. This narrative review examines the impact of obesity on respiratory physiology during mechanical ventilation and discusses strategies for optimizing ventilatory management in patients with obesity and acute lung injury. Obesity primarily reduces functional residual capacity and expiratory reserve volume through cephalad displacement of the diaphragm and increased intra-abdominal pressure. These alterations promote airway collapse, impaired ventilation distribution, and mild hypoxemia. During general anesthesia, additional reductions in lung volume and increased pleural pressure further predispose patients with obesity to airway closure and atelectasis. Ventilatory management should include adequate preoxygenation, recruitment maneuvers when appropriate, and individualized positive end-expiratory pressure (PEEP) titration. In patients with acute hypoxemic respiratory failure or acute respiratory distress syndrome, excess adiposity may worsen respiratory mechanics by increasing superimposed pressure and the prevalence of airway closure. These mechanisms complicate interpretation of respiratory mechanics. Advanced bedside monitoring tools, including esophageal pressure manometry and electrical impedance tomography, may provide valuable insights for optimizing ventilatory settings and balancing lung recruitment with the risk of overdistension. In moderate-to-severe acute respiratory distress syndrome, prone positioning is feasible and safe. Furthermore, individualized weaning approaches, and early use of noninvasive ventilation after extubation may further improve respiratory management.