To accommodate chest wall weight during mechanical ventilation in obese patients, which adjustment is recommended?

• A. Increase FiO2 only
• B. Apply high PEEP only
• C. Use PEEP to offset weight of chest wall
• D. Avoid PEEP entirely

Answer: (C)

In obesity the chest wall’s weight adds external pressure on the lungs, raising pleural pressures and reducing lung compliance and end-expiratory lung-volume, which promotes atelectasis and poorer oxygenation. Using PEEP increases mean airway pressure and helps keep the airways and alveoli open at the end of expiration, offsetting the chest wall’s compressive effect. This preserves functional residual capacity, improves alveolar recruitment, and enhances oxygenation more effectively than simply increasing FiO2, which doesn’t address airway collapse or recruitability. While titrating PEEP to achieve adequate oxygenation, it’s important to monitor hemodynamics, because excessive PEEP can impair venous return and cause overdistension. The goal is to use enough PEEP to counterbalance chest wall load without compromising circulation.