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IntroductionObstructive sleep apnoea (OSA) is common in patients with chronic kidney disease (CKD) and may contribute to the progression of kidney disease either through direct effects of hypoxia on the kidney or indirectly through hypoxaemia-induced oxidative stress, endothelial dysfunction, inflammation, activation of the renin–angiotensin and sympathetic nervous systems, and hypertension. Treatment of OSA with continuous positive airway pressure (CPAP) improves many of these physiological abnormalities in patients with normal renal function, though to date there are no trials evaluating the effect of OSA treatment on kidney function in patients with CKD. The purpose of this study is to test the feasibility and efficacy of CPAP therapy in CKD patients with OSA.Methods and analysisThe study is a randomised, controlled, non-blinded, parallel clinical trial in which patients with established CKD are screened for OSA. Patients with OSA are randomised to either conventional medical therapy (control group) or medical therapy and CPAP (CPAP group) and followed for 1 year. The primary outcome is the change in estimated glomerular filtration rate. Secondary outcomes are the change in the urinary albumin/creatinine ratio, the Epworth Sleepiness Scale , Pittsburgh Sleep Quality Index and Kidney Disease Quality of Life questionnaire.Ethics and disseminationEthics approval has been obtained from the Conjoint Health Research Ethics Board (ID: REB15-0055). Results from this study will be disseminated through presentations at scientific conferences and publication in peer-reviewed journals.Trial registration numberNCT02420184; Pre-results.

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Chronic kidney disease (CKD) occurs in up to 16% of adults worldwide (Jha, 2013) and increases the risk of cardiovascular disease and death (Go, 2004). Furthermore, progression of CKD to end-stage renal disease has significant implications both for individual patients (James, 2010) and healthcare costs (Silva, 2018). Obstructive sleep apnoea (OSA) occurs in up to 40% of patients with CKD (Nicholl et al., 2012a, 2012b), and has the potential to accelerate the loss of kidney function (Fine, 2008). Several experimental animal models (Abuyassin, 2018) and some human studies (Ahmed, 2011) have suggested that this is modulated by nocturnal hypoxaemia. However, to date, there have been no well-designed interventional studies that have investigated whether treating OSA in patients with CKD improves physiological and clinical renal outcomes.We are conducting a pilot randomised controlled trial (RCT) (Rimke, 2019) on patients with CKD and OSA to investigate the effect of continuous positive airway pressure (CPAP) on renal