Exercise and Vascular Function in Haemodialysis Patients

• Brachial artery flow mediated dilatation [ Time Frame: Baseline and 12 week follow-up ] [ Designated as safety issue: No ]
  Brachial artery diameter is measured using vascular ultrasound. A cuff similar to that used for blood pressure is then inflated around the forearm for 5 minutes. Following cuff release vascular ultrasound is used to measure arterial dilation in response to reactive hyperaemia. Relative change in diameter provides a measure of endothelial function. Images are recorded over a period of 4-5 minutes post cuff release.
  
  

• Aortic pulse wave velocity [ Time Frame: Baseline and three month follow-up ] [ Designated as safety issue: No ]
  Aortic pulse wave velocity is measured using a Vicorder (Skidmore Medical, Bristol UK). Briefly the Vicorder measures the time taken for a pulse wave to travel between a pressure cuff located on the carotid artery and another at the site of the femoral artery. The calculated velocity of the pulse wave is a measure of central arterial stiffness.
  
  
• Maximal aerobic power [ Time Frame: Baseline and three months ] [ Designated as safety issue: No ]
  Peak aerobic power is assessed using a graded exercise test with respiratory gas analysis. An Astrand protocol will be used with cycle ergometry. Participants continue until volitional exhaustion or the test is terminated by the investigator. An oxygen uptake figure in ml/kg/min is a measure of peak aerobic power (VO2peak)
  
  
• Timed up-and-go [ Time Frame: Baseline and three month follow-up ] [ Designated as safety issue: No ]
  The time taken to stand up from a chair, walk three metres and return is recorded. This is a functional measure of mobility with a threshold time related to falls and fractures.
  
  
• Sit-to-stand 5 [ Time Frame: Baseline and 3 month follow-up ] [ Designated as safety issue: No ]
  The time taken to stand up from a chair five times without using upper limb assistance is recorded. This is a surrogate measure of lower limb power with a threshold that is related to balance and risk of falls.
  
  
• Non exercise questionnaire [ Time Frame: Baseline and 3 month follow-up ] [ Designated as safety issue: No ]
  A non-exercise questionnaire utilising anthropometry, gender and self reported physical activity will be used to estimate aerobic fitness. This method carries minimal burden compared to physical performance tests and is a useful screening tool for health counselling.
  
  
• Physical activity [ Time Frame: Baseline and 3 month follow-up ] [ Designated as safety issue: No ]
  Physical activity over a seven day period will be measured using an Actigraph accelerometer. The monitor measures body movement as activity counts which may be categorised according to level of intensity using established cut-points.
  
  
• Kidney Disease Quality of Life Short Form (KDQOL) [ Time Frame: Baseline and 3 month follow-up ] [ Designated as safety issue: No ]
  The KDQOL is a self-administered questionnaire designed to measure generic health related quality life as well as condition specific items. Higher scores indicate better quality of life.
  
  
• Duke Activity Status Index [ Time Frame: Baseline and 3 months ] [ Designated as safety issue: No ]
  This self administered 12 item questionnaire provides a self reported measure of physical capacity. Higher scores indicate higher fitness and ability to perform activities of daily living.
  
  
• Leicester Uraemic Symptom Scale (LUSS) [ Time Frame: Baseline and 3 month follow-up ] [ Designated as safety issue: No ]
  The LUSS provides a measure of condition related symptom burden. it records the number of symptoms, frequency and their level of intrusiveness.
  
  

Life expectancies in haemodialysis patients are significantly shorter than the general population due to higher cardiovascular disease risk. This is mediated by higher prevalence of cardiovascular risk factors associated with chronic kidney disease and the haemodialysis procedure. Consequently ageing of the arterial system is accelerated in this condition leading to higher prevalence of arterial plaques and increased arterial stiffness.

Higher physical activity and fitness are associated with lower cardiovascular disease and all-cause mortality in haemodialysis patients and the general population. Moreover, physical inactivity is associated with increased arterial stiffness and plaques which narrow heart arteries. Worryingly the haemodialysis population is on average highly inactive with low fitness.

Current research demonstrates that exercise which improves fitness improves arterial health. Increased bloodflow during exercise stimulates the release of nitric oxide causing arteries to dilate. Regular exercise is believed to lead to beneficial remodelling of arteries and lower arterial stiffness. Exercise is reported to improve arterial function across a range of conditions. However published research regarding the possible benefits of long term aerobic exercise on arterial health in this population is conflicting. Limitations in study design, moderately high participant dropout rates and low statistical power hamper a definitive conclusion. Importantly a gold standard measure of arterial function has not been used in previously published studies.

There is ample evidence that exercise programmes in people on dialysis improve fitness, physical function, and quality of life. It is also clear that a state of higher physical activity and fitness is associated with better arterial function in the general population. It would be advantageous for reasons of health counselling to determine whether the process of improving physical fitness and activity levels may also improve arterial health in haemodialysis patients.