Acute exacerbations of Chronic Obstructive Pulmonary Disease (COPD) may require mechanical ventilation. Various mechanical ventilation strategies and modes can be used to manage respiratory insufficiency in such patients. High tidal volumes required for mechanical ventilation of patients with obstructive pathologies is a well-known fact. Adapted Support Ventilation (ASV) is an intelligent closed-loop mechanical ventilation mode which automatically adjusts ventilation to lung mechanics. Led by measured lung mechanics, ASV mode often generates higher than usual tidal volumes during mechanical ventilation of COPD patients, particularly if the minute volume (MV) target is high. Thus, the effects of high tidal volumes on inspiratory transpulmonary pressure (Ptp), and whether Ptp stays within safe limits during ASV mode is of great interest.
Patients with acute exacerbation of COPD who required mechanical ventilation will be enrolled in the first 24 hours of admission to the intensive care unit. All patients will be deeply sedated. An esophageal balloon catheter will be inserted in order to measure transpulmonary pressure. 100 % minute volume target will be calculated in advance as 100 ml per ideal body weight.
Patients will be ventilated with two different MV targets in two sets. 'Adapted support ventilation' and 'volume control (VC)' modes will be used consecutively within each set. While the target minute volume will be 100 % in the first set, the volume target in the second set will be tuned to decrease patients PaCO2 below 45 mmHg. The sequence of ventilation mode will be randomized within each set. Ventilation periods will be 30 minutes with 15 minutes washout period in between. İf Ptp increase above 20 cmH20 at any ventilation mode, the tidal volume will be decreased.
ASV mode is expected to be safe, assessed by adequate inspiratory transpulmonary pressures, and expected to be as effective as VC mode with lower intrinsic positive end expiratory pressure (iPEEP) levels.
