The acute effects of cigarette smoking on treadmill exercise distances in patients with stable intermittent claudication.

The hypothesis that smoking has an acute effect on treadmill exercise performance in patients with peripheral vascular disease was investigated in a crossover trial. Twelve patients with stable intermittent claudication who were regular smokers attended on two occasions within one week and treadmill tests were performed after 1/2, 1, 1 1/2, and 2 hours. Immediately before the second exercise test, two standard cigarettes were smoked or an unlit cigarette was "sham-smoked." Because participants could not be blinded, an attempt to control for patient bias was made. Half were told that we expected smoking to make no difference or possibly cause some improvement, and half were told that we expected it to make no difference or possibly cause some deterioration. These explanations and the order of study days were determined by balanced randomization. Suggestion had a significant influence on claudication distance immediately after smoking (p less than 0.01) but no significant effect on walking distance. Combining data from both groups assumes that no overall bias was introduced by the explanations given. Immediately after smoking, small, nonsignificant increases in claudication distance (+10%, 95% CI-7%, +27%) and walking distance (+9%, 95% CI-2%, +19%) were observed. Smoking caused a mean increase in heart rate of 9 beats per minute, which persisted for one hour, but no consistent change in blood pressure. The results show that suggestion may have a significant influence on treadmill exercise distances. Smoking is unlikely to have an important acute effect on exercise performance in claudicants.