Lung-protective perioperative mechanical ventilation

Intraoperative ventilation has the potential to cause lung injury and possibly increase risk of pulmonary complications after surgery. Use of large tidal volumes could cause overdistension of lung tissue, which can be aggravated by too high levels of positive end-expiratory pressure (PEEP). Too low levels of PEEP, though, could result in repetitive opening and closing of lung tissue. The main aim of this thesis was to investigate the effect of intraoperative use of higher levels of PEEP and recruitment manoeuvres on occurrence of postoperative pulmonary complications (PPCs). We hypothesized that this strategy would protect against development of PPCs during low tidal volume ventilation. We further investigated several other aspects of perioperative ventilation, focussing on associations between ventilator settings and PPCs and outcome. The main finding is that ventilation with higher levels of PEEP does not seem to reduce development of PPCs during low tidal volume ventilation in non-obese patients undergoing major surgery. High levels of PEEP may even be detrimental by causing hemodynamic compromise and maybe even by increasing the risk of PPCs. We further show that lung-protective strategies using low tidal volumes combined with higher levels of PEEP reduce the incidence of PPCs, but do not shorten hospital length of stay, or improve survival. In the event of pulmonary complications, patients do have longer lengths of stay and higher incidence of mortality. Finally, use of higher levels of PEEP during postoperative ventilation after cardiac surgery resulted in better compliance and oxygenation, but this was not sustained after extubation