A prospective in-group comparison of the efficacy and safety of fully closed-loop control ventilation (Intellivent-ASV (Registered Trademark) with conventional adaptive support ventilation (ASV) and synchronized intermittent mandatory ventilation (SIMV) modes.

Materials and Methods: The study will take place in the 9-bed Medical ICU (MICU) at the Hadassah-Hebrew University Medical Center, a 750-bed academic tertiary referral center. The MICU admits critically ill, non-surgical cases with acute respiratory, infectious, neurological, haematological-oncological, renal, metabolic and other general medical problems. All patients admitted to our MICU and who will be ventilated for at least 24 hours prior to recruitment will be eligible for inclusion. Patients included will also need to have stable hemodynamic and respiratory parameters over the previous 12 hours. We will exclude patients due for extubation on the same day, patients with unstable hemodynamic parameters (labile blood pressure or pulse rate or escalating vasopressor or inotrope requirements), those requiring mandatory ventilation (such as pressure controlled ventilation) or who are receiving inhaled nitric oxide. Pregnant women and minors (age less than 18 years) will also be excluded. The study was reviewed and approved by the Hadassah Hebrew University Hospital Institutional Review Board. Study design and parameters recorded: 1. Participants will all be initially ventilated for at least two hours on ASV, the standard ventilation mode in our Medical ICU. The usual initial setting is 100% minute ventilation using the patient ideal body weight, PEEP within the range of 2-12 cmH2O PEEP and the lowest FiO2 allowing adequate oxygenation (SaO2 greater than 93% or a PaO2 greater than 70 mmHg) in the range of FiO2 0.35 - 0.5. At the end of this 2 hour period, baseline parameters and arterial blood gases will be obtained. These include blood pressure (BP), heart rate (HR), FiO2, PEEP, inspiratory pressure received, compliance, resistance, peak inspiratory pressure , respiratory rate- (total breaths per minute and spontaneous breaths per minute) , spontaneous minute volume, expiratory tidal volume and actual minute volume. 2. The ventilation mode will then be changed to Intellivent-ASV (Registered trademark) for a period of two hours, after which the same parameters will be recorded. 3. The patients will subsequently be returned to the standard (baseline) mode of ventilation (ASV) for two hours, followed by a change to SIMV mode for a period of two hours, after which the same, previously described, parameters will be obtained. SIMV settings will be determined by the treating intensivist according to individual preference and patient condition, based on: tidal volume of 6-10 ml/kg, respiratory rate of 10-18 breaths per minute, PEEP of 2-12 cmH2O and pressure support of 10-20 cmH2O. The doses of sedatives administered to the patients will not altered throughout the study period. Data Analysis The results will be presented as mean plus standard deviation or range. Groups will be compared using analysis of variance (ANOVA) to detect if "between-group" variation is greater than "within-group" variation. In addition, the Student's T-test will be used to compare matched groups. A p value of less than 0.05 will be considered significant.