Risks and benefits of mechanical ventilation with positive end-expiratory pressure during the perioperative phase

Abstract

Gas exchange disturbances during and following general anaesthesia result primarily from atelectasis and may lead to threatening hypoxemia. Research has shown that atelectasis appears within the first 5 minutes in approximately 90% of all patients due to oxygen uptake and mechanical ventilation with pure oxygen via the induction of narcosis. A reduction of inspiratory oxygen concentration from 100% to 80% during the induction is able to minimize the size of atelectasis by nearly 85%. For recruitment of atelectasis in adults with a closed chest an airway pressure of approx. 40 cm H2O is needed for a time period of 7 - 10 seconds. Whenever a high inspiratory oxygen concentration is needed, mechanical ventilation with positive end-expiratory pressure should be applied in order to avoid renewed alveolar collapse. The exclusive use of PEEP leads to only partial recruitment of the atelectasis and does not improve the gas exchange in unselected patients. Serious side effects with the intraoperative application of moderate PEEP levels (5 - 10 cm H2O in adults) are not expected. Atelectasis may be one of the main causes for postoperative pulmonary complications such as pneumonia and hypoxemia CPAP and if necessary non-invasive mechanical ventilation with PEEP are the most effective procedures for reopening atelectasis and in case of pulmonary complications should be part of the post-operative standard therapy, although research is still needed to determine the long-term prognostic use.