Determinants of non-invasive ventilation success or failure in morbidly obese patients in acute respiratory failure

Introduction

Malignant obesity hypoventilation syndrome (MOHS) refers to the association between morbid obesity (body mass index >40 kg/m²), daytime hypercapnia (PCO₂ >45 mmHg) after other respiratory or neuromuscular causes of alveolar hypoventilation have been excluded, and multiple organ disorders (diabetes mellitus, arterial hypertension, metabolic syndrome, obstructive sleep apnea syndrome) [1]. Acute respiratory failure (ARF) is a common life-threatening complication of MHOS. Non-invasive ventilation (NIV) provides the cornerstone of the therapeutic management of decompensated MOHS [2]. We aimed to identify the determinants of NIV success or failure in this indication.

Methods

A monocentric prospective observational study including 48 patients with MOHS and treated by NIV for ARF over a 2-year period.

Results

NIV failed to reverse ARF in only seven patients. NIV failure was associated with a sixfold increase in in-hospital mortality (85.7% vs. 14.6%; P < 0.001). Factors associated with NIV failure and need for endotracheal intubation included pneumonia (n = 5, 71.4% vs. n = 8, 19.5%; P = 0.01), higher SOFA (11 vs. 5; P < 0.001) and SAPS 2 (69 vs. 39; P = 0.001) score at admission. The only factor associated with successful response to NIV was idiopathic decompensated MOHS (n = 19, 100% vs. n = 0, 0%; P = 0.03). In these patients, pH (7.23 vs. 7.28 vs. 7.44, respectively, at H0, H2, H24; P < 0.05) and PCO₂ (74.5 vs. 68.5 vs. 57 mmHg, respectively, at H0, H2, H24; P < 0.05) dramatically improved with NIV.

Conclusion

NIV provides a very efficient therapy to reverse hypercapnic ARF in morbidly obese patients. Multiple organ failure and pneumonia are the main factors associated with NIV failure in patients with MOHS.