Role of non-invasive ventilation (NIV) in the perioperative period.

Anaesthesia, postoperative pain and surgery (more so if the site of the surgery approaches the diaphragm) will induce respiratory modifications: hypoxaemia, pulmonary volume decrease and atelectasis associated to a restrictive syndrome and a diaphragm dysfunction. These modifications of the respiratory function occur early after surgery and may induce acute respiratory failure (ARF). Maintenance of adequate oxygenation in the postoperative period is of major importance, especially when pulmonary complications such as ARF occur. Non-invasive ventilation (NIV) refers to techniques allowing respiratory support without the need of endotracheal intubation. Two types of NIV are commonly used: noninvasive continuous positive airway pressure (CPAP) and noninvasive positive pressure ventilation (NPPV) which delivers two levels of positive pressure (pressure support ventilation + positive end-expiratory pressure). NIV may be an important tool to prevent (prophylactic treatment) or to treat ARF avoiding intubation (curative treatment). The aims of NIV are: (1) to partially compensate for the affected respiratory function by reducing the work of breathing, (2) to improve alveolar recruitment with better gas exchange (oxygenation and ventilation) and (3) to reduce left ventricular after load increasing cardiac output and improving haemodynamics. Evidence suggests that NIV, as a prophylactic or curative treatment, has been proven to be an effective strategy to reduce intubation rates, nosocomial infections, intensive care unit and hospital lengths of stay, morbidity and mortality in postoperative patients. However, before initiating NIV, any surgical complication must be treated. The aims of this article are (1) to describe the rationale behind the application of NIV, (2) to report indications (including induction of anaesthesia) and contraindications and (3) to offer some algorithms for safe usage of NIV in high-risk surgery patients.