Predictors of noninvasive ventilation failure in critically ill obese patients: a brief narrative review

 Non-invasive ventilation ( NIV ) has been used successfully for the management of acute respiratory failure (ARF) more often in the last two decades than previously. Unfortunately, NIV can have failure rates ranging from 5% to 50% and patient selection is the key to success. There are particular groups of patients that are more likely to benefit from NIV. For patients with hypoventilation syndrome (OHS) this treatment can be beneficial. This review seeks to evaluate the effectiveness of NIV in acute ARF and determine predictors of NIV failure in morbidly obese patients. Only a few studies have investigated NIV success or failure in these patients. NIV was most often effective when patients were carefully selected. Obese patients who exhibited early NIV failure had a high severity score at admission. In contrast, more than half of hypercapnic patients with decompensated OHS exhibited a delayed but successful response to NIV. Patients with decompensation of OHS had better prognosis and response to NIV than other hypercapnic patients. They required more aggressive NIV settings, a longer time to reduce paCO2 levels , and more frequently a delayed but successful response to NIV which should encourage the use of NIV rather than early intubation. Since clear predictors of NIV failure have not been identified, a strict and prolonged monitoring is mandatory.