Effects of Different Modes and Support Level on Oxygen Consumption and Respiratory Muscle Oxygenation in Patients with Mechanical Ventilator

About 20% of patients in ICU failed to wean from mechanical ventilator. Common causes of weaning failure included: increased workload of breathing, hypoxia, respiratory muscle fatigue and/or malnutrition. As the level of mechanical ventilation progressive decreased in weaning phase, the workload of respiratory muscle increased. Several studies demonstrated that the oxygen consumption (VO2) of respiratory muscles in the patients being weaned from mechanical ventilation can be considerably higher, and many authors, rather than focusing on the mechanical work of breathing, evaluated the role of VO2 as a predictor of weaning success.Adaptive support ventilation mode (ASV) is a closed loop mode of mechanical ventilation (MV) that provides a target minute ventilation by automatically adapting inspiratory pressure and respiratory rate with the minimum work of breathing on the part of the patient. Several studies have discovered the effect of different ventilator modes on weaning outcomes in patients with mechanical ventilator. However, few have examined the changes of VO2 among different ventilator modes. The purpose of this study is the compared VO2 among different ventilator modes and support levels in patients with mechanical ventilators. MethodsSubjects who have been on mechanical ventilator for more than 24 hours and are ready for weaning process will be recruited from medical intensive care units in hospital (n=40). This study is a randomized crossover controlled trial for PSV and ASV. At baseline, the ventilator status will be started from PSV 8 cmH2O, followed by switching to ASV mode with matched minute volume (MV) to PSV 8 cmH2O. The patients were then randomly assigned to group 1: support level from high (PSV 12 cmH2O and ASV with matched MV) to low (CPAP and ASV with matched MV), or group 2: low to high level. Each status remained for 20 min and the data was recorded from the last 3 mins of each step. The , production of carbon dioxide ( ) and EE were measured by an indirect calorimetry. The oxygenation status of respiratory muscles will be measured by near-infrared spectroscopy (NIRS). The differences between modes are compared by t-test. The significance level was set as p value ＜ 0.05.

Project ID:PC10708-0739
External Project ID:MOST107-2314-B182-049