Total Hemoglobin Mass Correlates with Peak Oxygen Consumption in Patients with Chronic Stroke

Abstract

Background: The peak oxygen consumption (V.O2peak) and blood hemoglobin concentration [Hb] are lower in stroke patients than in age-matched healthy subjects. The ability of skeletal muscles to extract oxygen is diminished after stroke. We hypothesized that the oxygen extraction capacity of skeletal muscles in stroke patients depends on [Hb]. To test the hypothesis, we determined the relationship between V.O2peak and total hemoglobin mass (tHb-mass) in stroke patients. Methods: The subjects were 19 stroke patients (age: 74 ± 2, mean ± SD, 10 males) and 11 age-matched normal subjects (age 76 ± 3, 6 males). Plasma volume (PV) and V.O2peak were measured on the same day. PV was measured using Evans Blue dye dilution method. Blood volume (BV) was calculated from PV and hematocrit, while tHb-mass was estimated from BV and [Hb]. Each subject underwent cardiopulmonary exercise test on a bicycle ergometer using a V.O2peak respiratory gas analyzer. Results: There were no differences in age, height, and weight between the two groups. V.O2peak was lower in stroke patients than in the control. BV and tHb mass were not significantly different between the two groups, but [Hb] was significantly lower in stroke patients. In stroke patients, V.O2peak correlated significantly with tHb-mass (r = 0.497, p < 0.05), but not with BV. Conclusion: Our results suggested that low [Hb] seems to contribute to V.O2peak in stroke patients. The significant correlation between tHb-mass and V.O2peak suggested that treatment to improve [Hb] can potentially improve V.O2peak in stroke patients.