A Prospective Randomised Trial of Two Tidal Volume Ventilator Strategies in Patients Undergoing Major Surgery

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There is no good evidence to guide the choice of breath size (tidal volume) delivered by the breathing machine during anaesthesia. In a recent multi-centre study, we found that anaesthetists deliver a variable tidal volumes with some patients receiving low-tidal volumes (6-7 ml/kg) and others receiving high-tidal volumes (9-10 ml/Kg) according to clinician preference. We also found that they typically positive end expiratory pressure (PEEP) (pressure to keep lung when breathing out has been completed) at an average modest value of 5.0 cmH2O. Thus, in Victoria and the Austin hospital in patients under general anaesthesia administered tidal volume can be variably high or low and PEEP is often applied at modest levels. Because of such variability and the possibility that one approach or another may be better at avoiding lung complications after anaesthesia, we wish to perform prospective randomised trial to evaluate the impact and outcome of two different tidal volume strategies during anaesthesia. Specifically, we wish to conduct a pilot single-centre prospective randomised trial comparing a low tidal volume (6 ml/kg) to a higher tidal volume (10 ml/kg) tidal volume strategy in combination with PEEP at 5 cm H2O for patients undergoing major surgery. The anticipated sample size is 900 participants over a 18 month period. Patients will be randomly allocated to either low or control tidal volume ventilation for the period of their surgical procedure to test the hypothesis that one of these two approaches in superior at decreasing post-surgical lung complications.