3. To determine if the clearance of middle-sized uraemic toxins improves symptoms of sleep apnoea. The middle-sized molecules to be assessed in this study include C-Reactive protein (CRP), beta 2-microglobulin (β2M), tumour necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and interleukin 8 (IL-8), which are the serum inflammatory markers that are commonly found in patients with obstructive sleep apnoea.