Determinants of the Recovery of Diaphragm Dysfunction in Patients With Prolonged Mechanical Ventilation

The transition to unassisted breathing after invasive ventilation often proves challenging. Persistent ventilator dependence predisposes patients to nosocomial complications and death and increases the economic burden of critical illness. Ventilator-dependence results from an imbalance between the load and capacity of the respiratory muscle pump. Patients who fail a trial of spontaneous breathing commonly exhibit excess respiratory loads secondary to weaning-induced pulmonary edema, atelectasis or dynamic hyperinflation. At the same time, many ventilator-dependent patients exhibit striking loss of respiratory pump capacity due to diaphragm dysfunction which predisposes to prolonged ventilator dependence. Diaphragm dysfunction is common in ventilated patients. By prolonging ventilator dependence it may be an important contributor to the poor long-term clinical and functional outcomes of survivors of critical illness. While some main risk factors for diaphragm dysfunction have been already described (diaphragm disuse induced by mechanical ventilation, sepsis, initial severity upon admission), the determinants of recovery of diaphragm dysfunction are unknown, as well it has not been elucidated whether diaphragm function can simply improve after the acute phase of ICU admission. Therefore, the goal of this study is to investigate the time course evolution of diaphragm function in patients exposed to prolonged duration of mechanical ventilation (i.e. in a weaning center) and to determine which factors are associated with an improvement of the diaphragm function leading to a safe mechanical ventilation discontinuation.