Authors: Göran Hedenstierna, M.D., Ph.D. et al
Anesthesiology 12/ 2016, Vol.125, 1079-1082.
SEVERAL clinical trials on protective ventilation during anesthesia and postoperative pulmonary complications have been performed during the past years and assumed to be suitable as guidelines for clinical treatment.1–8 Comprehensive reviews and meta-analysis have also been performed.9,10 Why then do these studies differ in their recommendations? One reason may be that the three major tools that have been used for creating protective ventilation have been taken over from intensive care and thus from a different category of patients with severely sick lungs that may be more vulnerable to forces caused by mechanical ventilation. These tools are (1) a low tidal volume or low driving pressure, assumed to reduce stress and strain of the lung; (2) a recruitment maneuver, assumed to reopen any collapsed alveoli; and (3) a positive end-expiratory pressure (PEEP), assumed to keep the lung open during ongoing anesthesia and surgery. Protective ventilation covers a period from induction to emergence from anesthesia, and whether any positive effects remain in the postoperative period is unknown. The atelectasis that develops intraoperatively may last for some days after surgery11 and may be a cause of postoperative pulmonary complications. Without knowing how successful the protective ventilation during anesthesia is in keeping the lung open without excessive strain, and if any positive effects remain in the postoperative period, reduction in postoperative pulmonary complications can hardly be attributed to protective ventilation. One may even ask if the concept protective ventilation can be replaced by nonharmful ventilation during anesthesia. It must also be realized that postoperative lung complications may be related to events other than intraoperative pulmonary dysfunction. That mentioned, let us return to the three tools that make up the framework of protective ventilation and discuss if the physiology makes sense.