LEVELS OF SUSTAINABLE AEROBIC WORKLOAD IN DIALYSIS PATIENTS

The aerobic performance of a heterogeneous group of 89 ambulatory medi cally stable patients on chronic hemodialysis was studied to define in dividual levels of the most acceptable metabolic workload. The patient s performed a step test protocol (3 steps) with a cycle ergometer. Eac h step (25 Watt) lasted 6 min. Heart rate (HR), oxygen consumption (VO 2), ventilation (VE), respiratory exchange ratio (RER), blood pressure (BP) and subjective ratings of dyspnea (CRd) and fatigue (CRf) levels were monitored throughout the test The test was continued to exhausti on or to values of systolic arterial blood pressure (SABP) >240 mmHg, heart rate (HR) greater than or equal to 85% max, or ST changes in EGG . In eleven patients (12.5% of the whole group) the test was interrupt ed within the first two minutes of exercise. In the remaining 78 patie nts, the maximum workload sustained for at least 3 min (MSW) was 25 Wa tts for 43 (48.5%), 50 Watts for 27 (30%), and 75 Watts for 8 (9%) pat ients. Performance was affected in a statistically significant manner by the subjects' anagraphic age, but not by their dialytic age, hemogl obin (Hb) level or weight. Individual levels of tolerable workload wer e estimated for 60% of the group from the stability of physiological v ariables during 3 min, and from subjective ratings at a ''moderate'' l evel. This level corresponded to an average of 3.5+/-0.9 METs, at 60% of the HRmax, with a mean BP of 167+/-21/98+/-14 mmHg. This could beco me a safe starting point for a program of physical retraining.