Effects of blood withdrawal on cardiac, hemodynamic, and pulmonary responses to a moderate acute workload in healthy middle-aged and older females

Abstract

Objectives: To investigate the effects of blood withdrawal on cardiac, hemodynamic, and pulmonary responses to submaximal exercise in females. Design: 30 healthy females (63.8 ± 8.3 yr) were recruited for this experimental study. Transthoracic echocardiography, non-invasive blood pressure monitoring, and oxygen uptake (VO2) were assessed during a fixed submaximal workload (100 W) prior to (day 1) and immediately after (day 2) a 10 % reduction of blood volume (BV). Main measurements included left ventricular end-diastolic volume (LVEDV), stroke volume (SV), cardiac output (Q), mean arterial pressure (MAP), systolic blood pressure (SBP), diastolic blood pressure (DBP), and VO2. BV was determined via carbon monoxide rebreathing. Results: Participant’s BV ranged from 3.8 to 6.6 L. Following 10 % reduction in BV (0.5 ± 0.1 L), LVEDV (p ≤ 0.030) and SV (p < 0.019) were reduced during submaximal exercise while Q was unchanged (p = 0.139) due to increased HR (p < 0.026). Hemodynamic variables including MAP (p < 0.015), SBP (p < 0.005), and DBP (p < 0.038) were reduced while VO2 was unaltered (p = 0.250). Conclusions: Blood withdrawal results in marked reductions in cardiac filling with compensatory chronotropic responses that preserve Q at a moderate submaximal workload in healthy females. Thus, BV determines the relative exercise intensity, as typically determined by HR, of submaximal efforts in this population.