Measuring the rate of change of haemodynamic response at the onset of exercise in normal limbs and those with intermittent claudication

Abstract

Patients with claudication have an inadequate haemodynamic response to exercise. Blood flow response will not only have a magnitude, but also a rate of change. There is scope for investigating these parameters, as manipulation of the factors which control them may benefit work to improve the treatment for claudication. This work compares the responses for patients with one normal limb and one with intermittent claudication. A custom-built ergometer allows unilateral, infragenicular plantar flexion exercise, whilst common femoral artery blood flow can be measured continuously by Duplex ultrasound. This apparatus was used to measure blood flow before, at the onset of and during a 5 W square-wave exercise stimulus in 15 patients. The claudicant group had a mean steady-state gain that was approximately half that of the normal group at around 170 ml min−1 (p < 0.001) and a response time that was much shorter (p = 0.006). A mean response time of 21.0 ± 1.4 s was achieved in claudicant limbs compared to 31.8 ± 2.9 s in normals. However, the average rate of change of blood flow during this response time was estimated to still be greater for the normal group, at 431.7 ± 47.1 ml min−2, than for the claudicant group. The differences in magnitude and rate of change of limb blood flow response to exercise in claudicants were significant and may have implications for the treatment of claudication.