Detecting Lung's Closing Pressure by Capnography

General anesthesia is associated with loss of pulmonary functional residual capacity and the consequent development of atelectasis and closure of the small airway. Mechanical ventilation in a lung with reduced functional residual capacity and atelectasis increased the dynamic alveolar stress-strain, inducing a local inflammatory response in atelectatic lung areas known as ventilatory-induced lung injury. This phenomenon may appear even in healthy patients undergoing general anesthesia and predisposes them to hypoxemic episodes that can persist in the early postoperative period. Lung recruitment maneuvers restore the functional residual capacity and, therefore, protect the lungs from lung injury. A key issue in this kind of treatment is detecting the lung's closing pressure in order to maintain the end-expiratory pressure above such a limit.