P0.1 and Extubation Failure in Critically Ill Patients

Weaning and extubation are essential steps for the management of critically ill patients when mechanical ventilation (MV) is no longer required. Extubation failure (EF) occurs in approximately 10-30% (1,2) of all patients meeting the readiness criteria and have tolerated a spontaneous breathing trial (SBT). EF is associated with prolonged MV, as well as increased morbidity and mortality (2). Therefore, the early identification of critically ill patients who are likely to experience EF is vital for improved outcomes. EF can result from different factors (respiratory, metabolic, neuromuscular), particularly cardiac factor, and can be caused by the inability of the respiratory muscle pump to tolerate increases in the cardiac and respiratory load (1,3). Respiratory drive represents the intensity of the neural stimulus to breathe. In mechanically ventilated patients, it can be abnormally low (i.e., suppressed or insufficient) or abnormally high (i.e., excessive), and thus result in excessively low or high inspiratory effort, leading to potential injury to the respiratory muscles (i.e., myotrauma) (4,5) or to the lungs. A high incidence of abnormal drive (low or high) may explain the high incidence of diaphragm dysfunction at time of separation from mechanical ventilation (6). Airway occlusion pressure (P0.1) is the drop in airway pressure (Paw) 100 milliseconds after the onset of inspiration during an end-expiratory occlusion of the airway (7). P0.1 measurement is not perceived by the patient and does not influence respiratory pattern. It is, in theory, a reliable measure of respiratory drive because the brevity of the occlusion explains that it is not affected by patient's response to the occlusion and it is independent of respiratory mechanics (8). P0.1 has also been correlated with inspiratory effort (9, 10) and it has been shown that in patients under assisted mechanical ventilation P0.1 might be able to detect potentially excessive inspiratory effort (11). P0.1