S53 DIFFERENTIATION BETWEEN HYPERCAPNIC OBSTRUCTIVE SLEEP APNOEA (OSA), COMBINED OSA AND OBESITY HYPOVENTILATION SYNDROME (OHS) AND LONE OHS IN CLINICAL PRACTICE

¹K. K. Lee, ¹A. Mistry, ¹N. Grey, ¹P. Murphy, ¹A. J. Williams, ¹A. C. Davidson, ²N. Hart. ¹Lane Fox Respiratory Unit, Guy’s & St Thomas NHS Foundation Trust, London, UK, ²Guy’s & St Thomas NHS Foundation Trust and King’s College London NIHR Biomedical Research Centre, London, UK

Background Respiratory complications of obesity are increasingly common. The definition of obesity hypoventilation syndrome (OHS) is an overlap between daytime hypercapnia and sleep-disordered breathing in obese patients. This description could more clearly be defined as obesity-related respiratory failure (ORRF) incorporating three separate groups: hypercapnic obstructive sleep apnoea (OSA), combined OSA and OHS (OSA–OHS) and lone OHS. However, distinguishing between these groups in clinical practice is often difficult without detailed nocturnal physiological monitoring. We hypothesised that clinical anthropometric data would distinguish between OSA, combined OSA–OHS and OHS.

Method Data of 88 patients initiated on home mechanical ventilation from August 2005 to June 2008 were analysed from a purpose-designed electronic discharge summary database. The groups were defined by detailed overnight physiological studies. As the proportion of OHS was low (n = 8), we combined OSA–OHS and OHS for comparative purposes.

Results 42% of patients had OSA and 58% had OSA–OHS or lone OHS. The mean age was 52 (16) and 55 (15) years, respectively, with 70% males in the OSA group and 49% males in the OSA–OHS and OHS group. The results are shown in table 1. …