Oxygen concentration and myocardial stunning

INTERVENTION: 4 litres oxygen delivered by nasal cannulae during standard 4‐hour haemodialysis. CONDITION: Dialysis‐induced myocardial stunning ; Circulatory System PRIMARY OUTCOME: 1. Myocardial stunning; 2. Development of regional wall motion abnormalities; ; Key observations are taken pre‐dialysis (baseline) and 15 minutes prior to end of dialysis (peak stress) by cardiac echocardiography (for later offline semi‐automated analysis for regional wall motion abnormalities). SECONDARY OUTCOME: Intradialytic haemodynamics; haemodynamic variables observed pre‐dialysis, and throughout dialysis treatment, with continuous non‐invasive measurement by finometer, and NICOM (bioreactance). INCLUSION CRITERIA: 1. Male and female 2. Over 18 years old 3. Chronic haemodialysis greater than 4 months