Continuous low tidal volume ventilation during cardiopulmonary bypass reduces the risk of pulmonary dysfunction

Objective: Pulmonary dysfunction is considered to be the most important complication after open heart surgery. Different maneuvers like intermittent or continuous positive pressure ventilation, low tidal volume ventilation and different vital capacity maneuvers have been used for reducing the incidence of pulmonary dysfunction after cardiac surgery. In this study we evaluated the effects of low tidal volume ventilation versus no-ventilation during cardiopulmonary bypass (CPB) in patients undergoing conventional CABG surgery. Methodology: This randomized clinical trial was conducted in a tertiary care cardiac hospital. One hundred patients who were planned to undergo conventional CABG surgery were divided into two groups by using draw randomization procedure. In Group A patients (ventilation group) ventilation was continued at low tidal volume of 3 ml/kg, respiration rate of 12 breaths/min and PEEP of 5 cmH2O. In Group B patients (non-ventilation group) ventilation was arrested during CPB. For data analysis Statistical Package for Social Sciences (SPSS) V17 was used. Parametric variables were compared using unpaired t-test and non-parametric variables were compared using 2-test. Results: The mean patient’s age in this study was 57.70 ± 8.57 years in ventilated group and 54.5 ± 8.33 years in non-ventilated group. PaO2/FiO2 ratio and alveolar-arterial oxygen tension gradient immediately after intubation was same in groups. But PaO2/FiO2 was significantly high in ventilated group after one hours of CPB and even after four hours of CPB (p < 0.001 and 0.002 respectively). Alveolar arterial oxygen tension (A-a O2) gradient after 1 hour and four hours of CPB was significantly low in Ventilated group (p < 0.001 and 0.001 respectively). Total Mechanical ventilation time was also significantly shorter in ventilated group 5.19 ± 1.96 hours versus 6.42 ± 2.60 hours in non-ventilated group (p 0.009). On 4th post-operative day, incidence of atelectasis was significantly low 20% in ventilated group versus 38% in non-ventilated group (p = 0.04). Conclusion: Continuous low tidal volume ventilation is associated with better oxygenation after surgery and reduced risk of post-op pulmonary complications during cardiopulmonary bypass in patients undergoing conventional coronary artery bypass graft surgery.