Evaluation of fully automated ventilation: a randomized controlled study in post-cardiac surgery patients
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Discrepancies between the demand and availability of clinicians to care for mechanically ventilated patients can be anticipated due to an aging population and to increasing severity of illness. The use of closed-loop ventilation provides a potential solution. The aim of the study was to evaluate the safety of a fully automated ventilator.
We conducted a randomized controlled trial comparing automated ventilation (AV) and protocolized ventilation (PV) in 60 ICU patients after cardiac surgery. In the PV group, tidal volume, respiratory rate, FiO2 and positive end-expiratory pressure (PEEP) were set according to the local hospital protocol based on currently available guidelines. In the AV group, only sex, patient height and a maximum PEEP level of 10 cmH2O were set. The primary endpoint was the duration of ventilation within a “not acceptable” range of tidal volume. Zones of optimal, acceptable and not acceptable ventilation were based on several respiratory parameters and defined a priori.
The patients were assigned equally to each group, 30 to PV and 30 to AV. The percentage of time within the predefined zones of optimal, acceptable and not acceptable ventilation were 12 %, 81 %, and 7 % respectively with PV, and 89.5 %, 10 % and 0.5 % with AV (P < 0.001). There were 148 interventions required during PV compared to only 5 interventions with AV (P < 0.001).
Fully AV was safe in hemodynamically stable patients immediately following cardiac surgery. In addition to a reduction in the number of interventions, the AV system maintained patients within a predefined target range of optimal ventilation.
KeywordsPositive-pressure respiration Randomized trial Closed-loop Thoracic surgery Cardiac surgery Mechanical ventilation
Dr. Lellouche holds a clinical research scholarship from FRSQ (Fonds de Recherche en Santé du Québec). Hamilton Medical provided a restricted grant of 60,000 Can$ to conduct the study and provided ventilators for the study. The funding agencies had no role in the conduct of the study, in the collection, analysis or interpretation of the data, or in the preparation, review or approval of the manuscript. Marc Wysocki participated to the study design, but data were analyzed independently from Hamilton Medical at IUCPQ Research Center (Serge Simard, biostatistician), and manuscript draft was prepared mainly by François Lellouche.
Conflicts of interest
Dr. Wysocki was head of medical research at Hamilton Medical Company when the study was performed; he is now Medical Director of GE Healthcare.
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