• Sleep apnoea

In recent decades, the prevalence of obesity and severe obesity has increased significantly around the globe.1 ,2 As a consequence, it is likely that the prevalence of obesity-associated comorbidities such as obesity hypoventilation syndrome (OHS) will follow the same trend.3 OHS is the most severe form of respiratory compromise induced by obesity, leading to increased mortality and a wide array of comorbidities such as pulmonary hypertension, right heart failure and increased risk of hospitalisation due to acute-on-chronic hypercapnic respiratory failure.4–6 Unfortunately, OHS remains frequently unrecognised or misdiagnosed even in patients with severe obesity hospitalised with hypercapnic respiratory failure.7 ,8

Although positive airway pressure (PAP) remains the cornerstone therapy for OHS, controversy persists as to the preferred mode of PAP therapy for long-term management.9 In theory, non-invasive ventilation (NIV) should be more effective than CPAP since it addresses the various complex pathophysiological disturbances that result in OHS, such as altered ventilatory drive, increased work of breathing due to restrictive chest physiology induced by excess adiposity and exacerbation of hypoventilation during sleep. However, observational and a few randomised controlled trials with short-term follow-up have shown that both CPAP and NIV are equally effective in improving daytime and nighttime hypercapnia as well as symptoms in patients with OHS.10–12 NIV is commonly prescribed as a fixed level of pressure support in the form of bilevel PAP in spontaneous mode or bilevel PAP spontaneous-timed (ST) mode with a back-up respiratory rate, or a variable level of pressure support such as volume-targeted pressure support. Given the lack of consensus and the limited information on long-term outcomes with the various modalities of PAP therapy, it is not surprising that there is significant variation in clinical practice.

To further address this relevant clinical question, Howard et al13 conducted a …