We read with great interest the article by Treschan et al.1 recently published in the European Journal of Anaesthesiology. The authors present a comparison of the effects of high (12-cm H2O) versus low (2-cm H2O) intraoperative positive end expiratory pressure (PEEP) levels in patients undergoing general anaesthesia for open abdominal surgery on postoperative spirometry readings at days 1 to 5 postsurgery. The authors found no difference in spirometry readings between the high and low PEEP groups at day 5, and also concluded the reductions in measured spirometry readings were associated with a greater incidence of postoperative pulmonary complications. We commend the authors on their work in an interesting and contentious area, where debate is certainly warranted. We also feel that the study raises several interesting points for further consideration.
The authors acknowledge several potential weaknesses in their work in the discussion. Of note, they highlight that the trial was effectively underpowered because of early cessation of the parent PROVHILO study.2 There was also variability in the mode of postoperative analgesia used, which led to several patients being excluded from the analysis, and may have introduced error into the findings.
It is also of note that patients included were determined to be intermediate to high risk of developing postoperative pulmonary complications. It is well recognised that postoperative noninvasive ventilation can attenuate and reverse the restrictive pulmonary syndrome that frequently occurs following major abdominal surgery, and may be used prophylactically to great clinical effect.3 There is no mention of noninvasive ventilation use in the study population, and no consideration of its potential impact in preventing postoperative pulmonary complications.
But we feel that the main discussion point arising from this study is what have we learned regarding the choice of intraoperative PEEP levels to prevent postoperative complications? We already know from PROVILHO2 that very high or low PEEPs confer no additional benefit. The IMPROVE study4 demonstrated improved clinical outcomes when more moderate levels of PEEP (6 to 8-cm H2O) were used as part of an intraoperative ventilation strategy that also included low tidal volumes and frequent recruitment manoeuvres. The real enigma appears to be what level of intraoperative PEEP is optimal – the high reported rates of postoperative pulmonary complications seen in the current study might suggest that neither 12 nor 2-cm H2O is the answer.
Rates of postoperative pulmonary complications are increasing, and becoming a significant challenge to those working in perioperative medicine.5 Faced with an ageing patient population and greater demands on surgical services it is vital that we develop robust care pathways that encompass many variables. We should use preoperative predictive scoring systems to identify those at risk, define guidelines for intraoperative ventilation strategies, optimise postoperative analgesia and consider prophylactic use of noninvasive ventilation to derive the best possible outcomes for our patients. Clearly, intraoperative PEEP is one such factor we need to consider, but future work should concentrate on defining the optimum PEEP within a holistic ‘package’ of care – we have previously seen encouraging results with 6 to 8-cm H2O, so is it time to consider the middle ground again?
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1. Treschan TA, Schaefer M, Kemper J, et al. PROVE Network Investigators. Ventilation with high versus low peep levels during general anaesthesia for open abdominal surgery does not affect postoperative spirometry: a randomised clinical trial. Eur J Anaesthesiol
2. Hemmes SN, Gama de Abreu M, Pelosi P. PROVE Network Investigators for the Clinical Trial Network of the European Society of Anaesthesiology. High versus low positive end-expiratory pressure during general anaesthesia for open abdominal surgery (PROVHILO trial): a multicentre randomised controlled trial. Lancet
3. Squadrone V, Coha M, Cerutti E, et al. Piedmont Intensive Care Units Network (PICUN). Continuous positive airway pressure for treatment of postoperative hypoxemia: a randomized controlled trial. JAMA
4. Futier E, Constantin JM, Paugam-Burtz C, et al. IMPROVE Study Group. A trial of intraoperative low-tidal-volume ventilation in abdominal surgery. N Engl J Med
5. Canet J, Sabate S, Mazo V, et al. PERISCOPE group. Development and validation of a score to predict postoperative respiratory failure in a multicentre European cohort: a prospective, observational study. Eur J Anaesthesiol