Perfusion pressure and movement-induced hyperemia: evidence of limited vascular function and vasodilatory reserve with age

Abstract

To better understand the mechanisms contributing to reduced blood flow with age, this study sought to elucidate the impact of altered femoral perfusion pressure (FPP) on movement-induced hyperemia. Passive leg movement was performed in 10 young (22 ± 1 yr) and 12 old (72 ± 2 yr) healthy men for 2 min, with and without a posture-induced change in FPP (~7 ± 1 ΔmmHg). Second-by-second measurements of central and peripheral hemodynamic responses were acquired noninvasively (finger photoplethysmography and Doppler ultrasound, respectively), with FPP confirmed in a subset of four young and four old subjects with arterial and venous catheters. Central hemodynamic responses (heart rate, stroke volume, cardiac output, mean arterial pressure) were not affected by age or position. The young exhibited a ~70% greater movement-induced peak change in leg blood flow (ΔLBF(peak)) in the upright-seated posture (supine: 596±68 ml/min; upright: 1,026 ± 85 ml/min). However, in the old the posture change did not alter ΔLBF(peak) (supine: 417±42 ml/min; upright: 412±56 ml/min), despite the similar increases in FPP. Similarly, movement-induced peak change in leg vascular conductance was ~80% greater for the young in the upright-seated posture (supine: 7.1 ± 0.8 ml·min(-1)·mmHg(-1); upright: 12.8 ± 1.3 ml·min(-1)·mmHg(-1)), while the old again exhibited no difference between postures (supine: 4.7 ± 0.4 ml·min(-1)·mmHg(-1); upright: 4.8 ± 0.5 ml·min(-1)·mmHg(-1)). Thus this study reveals that, unlike the young, increased FPP does not elicit an increase in movement-induced hyperemia or vasodilation in the old. In light of recent evidence that the majority of the first minute of passive movement-induced hyperemia is predominantly nitric oxide (NO) dependent in the young, these findings in the elderly may be largely due to decreased NO bioavailability, but this remains to be definitively determined.

Fig. 1.

Posture-induced alterations in femoral arterial, venous, and perfusion pressure. Data collected from catheters placed in the common femoral artery (CFA) and common femoral vein (CFV) in a subset of 4 young and 4 old subjects. A: baseline measures without movement, *P < 0.001 compared with supine posture. B: baseline (BL) average during the 60 s prior to initiation of movement. Dashed line at 0 s indicates the start of 2 min of passive movement. Main effect of increased femoral perfusion pressure throughout 2 min of passive movement (P < 0.001). Data are illustrated as means ± SE.

Fig. 2.

Peripheral hemodynamic responses to passive limb movement. A: absolute leg blood flow (LBF, ml/min). B: change (Δ) in LBF, normalized for the difference in baseline between group and body posture. C: peak Δ in LBF. D: absolute leg vascular conductance (LVC, ml·min⁻¹·mmHg⁻¹). E: Δ in LVC. F: peak Δ in LVC. Young, n = 10; old, n = 12. Baseline (BL) indicates the average of the 60 s just prior to initiation of passive movement. Dashed line at 0 s indicates the start of 2 min of passive movement. *P < 0.001 compared with supine posture, #P < 0.05 compared with the young in the same posture. Data are illustrated as means ± SE.

Fig. 3.

Attenuated movement-induced rapid vasodilation with age. The slopes calculated for the increase in the leg vascular conductance (LVC, ml·min⁻¹·mmHg⁻¹) over time (9 s) indicate a reduced NO-independent contribution to rapid vasodilation with age (young, n = 10; old, n = 12). Greater femoral perfusion pressure (FPP) increased the slope of the LVC over time in the young, with no effect in the old. *P < 0.001, slope of LVC over time compared with supine posture, #P < 0.001 slope of LVC over time compared with the young in the same posture. Data are illustrated as means ± SE.

Fig. 4.

Attenuated movement-induced vasodilatory reserve with age. The difference in the peak change (Δ) in leg vascular conductance (LVC, ml·min⁻¹·mmHg⁻¹) between the supine and upright-seated posture (vasodilatory reserve) in the old (n = 12) compared with the young (n = 10). #P < 0.001 compared with the young. Data are illustrated as means ± SE.