Modern dialysis technology, such as Haemodiafiltration (HDF), allows for better removal of toxic molecules such as beta 2 microglobulin (B2M) and C-Reactive protein (CRP), than standard haemodialysis treatment, and may offer the benefits of nocturnal dialysis to all dialysis patients. No one has examined the effect of HDF on sleep apnoea in haemodialysis patients, and the investigators will answer this question in this study.