Cerebrovascular Dysregulation in Chronic Kidney Disease

The purpose of this study is to test whether or not regular exercise training may improve brain blood flow regulation in patients with chronic kidney disease (CKD).

Prior research has shown that CKD patients have an increased risk of stroke and that impairments in brain blood flow regulation predict stroke in other chronic disease states. This study will test whether exercise training can improve brain blood flow regulation via improved dynamic cerebral autoregulation and cerebrovascular carbon dioxide reactivity in CKD. Participants will undergo exercise training on a stationary bicycle, or stretching exercises, 3 times per week for 12 weeks.

Participants will be assigned to one of two conditions:1) aerobic exercise training on a stationary bicycle, or 2) stretching and balance training.

Participants will exercise 3 times a week on a stationary bicycle. Exercise intensity will begin at low levels (50% of maximal heart rate reserve) and increase as tolerated to a maximum of 80% of maximal heart rate reserve. Exercise time will progress from an initial 20 minutes per session to a maximum of 45 minutes per session.

Participants will undergo progressive whole body stretching and balance exercises. This type of low intensity exercise is designed not to increase heart rate but rather to improve joint mobility and the ability to perform activities of daily living. This will serve as the control group to the exercise group. The control group will come in for stretching sessions 3 times per week for 20-45 minutes.

Mean arterial pressure and middle cerebral artery blood velocity data will be subjected to transfer function analysis to derive mean arterial pressure-middle cerebral artery blood velocity transfer function phase (radians) and gain (cm/s/mmHg). These indices reflect dynamic cerebral autoregulation.

Mean arterial pressure-middle cerebral artery blood velocity transfer function phase (radians) and gain (cm/s/mmHg) will be compared at baseline (week 0) and after completing the 12-week intervention (week 13).

cerebrovascular carbon dioxide reactivity will be quantified as the change in middle cerebral artery blood velocity for a given change in end-tidal CO2 (cm/s/mmHg).

cerebrovascular carbon dioxide reactivity will be compared at baseline (week 0) and after completing the 12-week intervention (week 13).

Inclusion Criteria: • Individuals with chronic kidney disease stages III-IV. Exclusion Criteria: Heart failure Chronic obstructive pulmonary disease Uncontrolled hypertension or hypotension Pregnancy or plans to become pregnant Inability to exercise on a stationary bicycle Current participation in exercise more than 20 minutes twice per week