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

Abstract

<b><i>Background:</i></b> The peak oxygen consumption (V.O_2peak) 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.O_2peak and total hemoglobin mass (tHb-mass) in stroke patients. <b><i>Methods:</i></b> 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.O_2peak 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.O_2peak respiratory gas analyzer. <b><i>Results:</i></b> There were no differences in age, height, and weight between the two groups. V.O_2peak 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.O_2peak correlated significantly with tHb-mass (<i>r</i> = 0.497, <i>p</i> &#x3c; 0.05), but not with BV. <b><i>Conclusion:</i></b> Our results suggested that low [Hb] seems to contribute to V.O_2peak in stroke patients. The significant correlation between tHb-mass and V.O_2peak suggested that treatment to improve [Hb] can potentially improve V.O_2peak in stroke patients.