Nocturnal haemodialysis increases pharyngeal size in patients with sleep apnoea and end-stage renal disease

Background. Sleep apnoea is common in patients with end-stage renal disease (ESRD) and is improved by nocturnal haemodialysis (NHD). Recent findings from our laboratory indicate the development of ESRD is associated with pharyngeal narrowing. We hypothesized that NHD increases pharyngeal cross-sectional area and that this is associated with an improvement in sleep apnoea. Methods. Twenty-four patients (aged 32-68 years), receiving conventional haemodialysis (CHD) (4 h/day, 3 days/week), were recruited for overnight polysomnography and estimation of pharyngeal cross-sectional area at functional residual capacity (FRC) and residual volume (RV). Patients were divided into apnoeic and non-apnoeic groups based on an apnoeahypopnoea index (AHI) 15/h. Following conversion from CHD to NHD (8 h/night, 36 nights/week) all measurements were repeated and apnoeic patients were classified as responders if AHI fell to 15 events/h. Results. Conversion from CHD to NHD was associated with an increase in pharyngeal cross-sectional area (FRC: 3.29 +/- 0.67 vs 3.39 +/- 0.75 cm(2); RV: 1.91 +/- 0.51 vs 2.13 +/- 0.48 cm(2), P < 0.05), which was not significantly different between groups. Sleep apnoea improved in three patients. Conclusions. Conversion from CHD to NHD is associated with an increase in pharyngeal cross-sectional area. This may play a role in some patients whose sleep apnoea improves on NHD.