Determinants of Noninvasive Ventilation Success and Failure in Obesity Hypoventilation Syndrome: A Narrative Review Across Acute and Chronic Care

Background/Objectives: Obesity hypoventilation syndrome (OHS) is a heterogeneous disorder characterized by obesity, chronic daytime hypercapnia, and sleep-disordered breathing. Noninvasive ventilation (NIV) provides ventilatory support during acute hypercapnic respiratory failure and for persistent hypoventilation in OHS, while continuous positive airway pressure (CPAP) is appropriate for selected stable patients with coexisting severe obstructive sleep apnea (OSA). This narrative review synthesizes determinants of NIV success and failure across acute and chronic OHS care. Methods: A targeted narrative search was conducted using PubMed/MEDLINE, Embase, and Scopus. Priority was given to OHS-specific cohort studies, randomized trials, individual patient data analyses, and relevant systematic reviews, with broader NIV evidence used cautiously when OHS-specific data were limited. Results: NIV success in OHS is best interpreted as a context-dependent trajectory rather than a single threshold. Acute success involves favorable trends in pH and PaCO2, reduced work of breathing, improved alertness, avoidance of invasive mechanical ventilation, and safe transition from the acute episode. Chronic success is reflected by sustained hypoventilation control, adherence, interface tolerance, symptom improvement, and fewer recurrent decompensations. Failure may reflect persistent physiological derangement, ineffective NIV delivery, or both. Conclusions: Phenotype-guided positive airway pressure (PAP) selection, early reassessment, technical optimization, adherence support, and structured follow-up may support the management of NIV outcomes in OHS. Distinguishing physiological failure from ineffective NIV delivery may help guide clinical reassessment and escalation decisions, although this conceptual framework requires prospective validation.