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Patients with intermittent claudication have a marked impairment in walking performance. As the primary determinants of this impairment are poorly understood, the aim of this study was to identify key physiological predictors of walking performance in claudicants using multiple regression analysis.
With Local Research Ethics Committee approval, 45 male claudicants (age 69 ± 9 years; mean ± SD) were recruited from the Sheffield Vascular Institute at the Northern General Hospital, Sheffield, UK. Each patient performed a graded treadmill test to determine maximum walking distance (MWD), peak oxygen uptake, and anaerobic threshold. Calf muscle oxygenation (StO2) at 1 min and time to minimum StO2 were also measured using near-infrared spectroscopy. On other occasions, peak calf blood flow, resting ankle-brachial index, and pulmonary oxygen uptake kinetics during steady-state walking were assessed. A forward stepwise multiple regression analysis was performed to determine predictors of MWD. Statistical significance was set at P ≤ 0.05.
A regression model comprising peak oxygen uptake, StO2 at 1 min, and time to minimum StO2 explained 64% of the variance in MWD. The following prediction equation was generated:
Adjusted R2 = 0.64, standard error of the estimate = 154 m (P < 0.001).
The results suggest that cardiopulmonary fitness and the ability to match oxygen delivery to metabolic demand are important determinants of walking performance in claudicants, and that specific near-infrared spectroscopy variables might be useful in studies that evaluate the mechanisms of clinical improvement with different treatment interventions.