Lower limb vasodilatory capacity is not reduced in patients with moderate COPD

Abstract

We compared exercise capacity (peak O2 uptake; V̇O2peak) and lower limb vasodilatory capacity in 9 patients with moderate COPD (FEV1 52.7 ± 7.6% predicted) and 9 age-matched healthy control subjects. V̇O2peak was measured via open circuit spirometry during incremental cycling. Calf blood flow (CBF) measurements were obtained at rest and after 5 minutes of ischemia using venous occlusion plethysmography. While V̇O2peak was significantly lower in the COPD patients (15.8 ± 3.5 mL·kg−1·min−1) compared with the control group (25.2 ± 3.5 mL·kg−1·min−1), there were no significant differences between groups in peak CBF or peak calf conductance measured 7 seconds post-ischemia. V̇O2peak was significantly correlated with peak CBF and peak conductance in the control group, whereas no significant relationship was found between these variables in the COPD group. However, the rate of decay in blood flow following ischemia was significantly slower (p < 0.05) for the COPD group (−0.036 ± 0.005 mL·100 mL−1·min−1·s−1) when compared with controls (−0.048 ± 0.015 mL·100 mL−1·min−1·s−1). The results suggest that the lower peak exercise capacity in patients with moderate COPD is not related to a loss in leg vasodilatory capacity.

Passive leg movement in chronic obstructive pulmonary disease: evidence of locomotor muscle vascular dysfunction

“…Our prior work examining brachial artery FMD (22) documented that patients with COPD exhibit vascular dysfunction, which was, at least in part, due to elevated oxidants, as acute treatment with an antioxidant cocktail partially restored FMD. However, until the present study, it was unclear whether this vascular dysfunction is evident in the lower extremities of patients with COPD, as previous work suggested perhaps no such dysfunction exists in the legs (41). Given previously documented differences in FMD between the upper and lower extremities (32,33), coupled with the fact that vascular dysfunction can be exaggerated in the lower extremity (33), it was possible that previous assessments of FMD may have underestimated the vascular dysfunction in patients with COPD.…”

“…However, although this hypothesis is scientifically sound, given growing concern as to whether or not the FMD assessment is predominantly NO dependent (53), coupled with the fact that FMD is typically performed in the nonambulatory upper limbs and may be limb specific (32,33), begs the question whether such vascular dysfunction exists in the locomotor muscle of the lower limbs of patients with COPD and whether such a deficit is NO dependent. To this end, Sabapathy et al (41) explored vascular function in the calf using reactive hyperemia measured by venous occlusion plethysmography and found no difference between nine patients with moderate-severity COPD and age-matched control subjects. However, as recognized by previous work (24), venous occlusion plethysmography readings are not always achievable and are only modestly related to the more robust ultrasound assessment of blood flow, creating some doubt about the validity of the above study (41).…”

“…To this end, Sabapathy et al (41) explored vascular function in the calf using reactive hyperemia measured by venous occlusion plethysmography and found no difference between nine patients with moderate-severity COPD and age-matched control subjects. However, as recognized by previous work (24), venous occlusion plethysmography readings are not always achievable and are only modestly related to the more robust ultrasound assessment of blood flow, creating some doubt about the validity of the above study (41).…”

The impact of venous occlusion per se on forearm muscle blood flow: implications for the near‐infrared spectroscopy venous occlusion technique

“…Following the 5 min of arterial occlusion, 12 serial venous occlusion trials were performed over the course of 3 min by intermittently inflating the arm cuff to 50 mmHg. A duty cycle of 15 s was used (8 s on and 7 s off; Sabapathy et al ., ) to facilitate a high sampling frequency of throughout the reactive hyperaemia. The first venous occlusion trial began within 5 s after the end of the arterial occlusion period.…”