Intra-rater reliability of leg blood flow during dynamic exercise using Doppler ultrasound

Test-retest reliability of Doppler ultrasound-based leg blood flow assessments during exercise in patients with chronic obstructive pulmonary disease

Doppler ultrasound may be used to assess leg blood flow (Q ̇ leg ${{\dot{Q}}_{{\mathrm{leg}}}}$ ), but the reliability of this method remains unexplored in patients with chronic obstructive pulmonary disease (COPD), where between-subject variability may be larger than healthy due to peripheral vascular changes. This study aimed to investigate the reliability of Doppler ultrasound in quantifyingQ ̇ leg ${{\dot{Q}}_{{\mathrm{leg}}}}$ during single-leg knee-extensor exercise (KEE) in COPD patients compared with those obtained from healthy matched controls. In this case-control study, 16 participants with COPD were matched based on sex and age with 16 healthy controls. All participants underwent measurement ofQ ̇ leg ${{\dot{Q}}_{{\mathrm{leg}}}}$ using Doppler ultrasound in a KEE set-up at various intensities on two separate visits. Confounding factors onQ ̇ leg ${{\dot{Q}}_{{\mathrm{leg}}}}$ were controlled for, and the ultrasound scans were consistently performed by the same sonographer. During exercise, smallest real difference (SRD) ranged from 367 mL to 583 mL in COPD and 438 mL to 667 mL in the control group. The coefficient of variation (CV) ranged from 7.9% to 14.3% in COPD and 9.4% to 10.4% in the control group. The intraclass correlation coefficient ranged from 0.75 to 0.92 in COPD and 0.67 to 0.84 in the control group. CV was lower in the control group during exercise at 0 W, but apart from that, reliability was not different between groups during exercise. Doppler ultrasound showed nearly equal reliability when evaluatingQ ̇ leg ${{\dot{Q}}_{{\mathrm{leg}}}}$ in COPD patients and healthy individuals with a CV below 15% during exercise for both groups. HIGHLIGHTS: What is the central question of this study? What is the between-day reliability of Doppler ultrasound when quantifying leg blood flow during single-leg knee-extensor exercise in COPD patients compared to healthy matched controls? What is the main finding and its importance? This study demonstrates a coefficient of variation ranging from 7.9 to 14.3% during single-leg knee-extensor exercise for between-day reliability when applying Doppler ultrasound to assess leg blood flow in patients with COPD. Furthermore, it offers insights into the peripheral circulatory constraints in COPD, as evidenced by diminished leg blood flow. This study is the first of its kind to evaluate the reliability of Doppler ultrasound in the assessment of the peripheral circulation during exercise in COPD.

The impact of leg position on muscle blood flow and oxygenation during low-intensity rhythmic plantarflexion exercise

PURPOSE

Resistance training (RT) is an effective countermeasure to combat physical deconditioning whereby localized hypoxia within the limb increases metabolic stress eliciting muscle adaptation. The current study sought to examine the influence of gravity on muscle oxygenation (SmO₂) alongside vascular hemodynamic responses.

METHODS

In twelve young healthy adults, an ischemic occlusion test and seven minutes of low-intensity rhythmic plantarflexion exercise were used alongside superficial femoral blood flow and calf near-infrared spectroscopy to assess the microvascular vasodilator response, conduit artery flow-mediated dilation, exercise-induced hyperemia, and SmO₂ with the leg positioned above or below the heart in a randomized order.

RESULTS

The microvascular vasodilator response, assessed by peak blood flow (798 ± 231 mL/min vs. 1348 ± 290 mL/min; p < 0.001) and reperfusion slope 10 s of SmO₂ after cuff deflation (0.75 ± 0.45%.s-1 vs.2.40 ± 0.94%.s-1; p < 0.001), was attenuated with the leg above the heart. This caused a blunted dilatation of the superficial femoral artery (3.0 ± 2.4% vs. 5.2 ± 2.1%; p = 0.008). Meanwhile, blood flow area under the curve was comparable (above the heart: 445 ± 147 mL vs. below the heart: 474 ± 118 mL; p = 0.55) in both leg positions. During rhythmic exercise, the increase in femoral blood flow was lower in the leg up position (above the heart: 201 ± 94% vs. below the heart: 292 ± 114%; p = 0.001) and contributed to a lower SmO₂ (above the heart: 41 ± 18% vs. below the heart 67 ± 5%; p < 0.001).

CONCLUSION

Positioning the leg above the heart results in attenuated peak vascular dilator response and exercise-induced hyperemia that coincided with a lower SmO₂ during low-intensity plantarflexion exercise.