Assessment of resistance vessel function in human skeletal muscle: guidelines for experimental design, Doppler ultrasound, and pharmacology

Abstract

The introduction of duplex Doppler ultrasound almost half a century ago signified a revolutionary advance in the ability to assess limb blood flow in humans. It is now widely used to assess blood flow under a variety of experimental conditions to study skeletal muscle resistance vessel function. Despite its pervasive adoption, there is substantial variability between studies in relation to experimental protocols, procedures for data analysis, and interpretation of findings. This guideline results from a collegial discussion among physiologists and pharmacologists, with the goal of providing general as well as specific recommendations regarding the conduct of human studies involving Doppler ultrasound-based measures of resistance vessel function in skeletal muscle. Indeed, the focus is on methods used to assess resistance vessel function and not upstream conduit artery function (i.e., macrovasculature), which has been expertly reviewed elsewhere. In particular, we address topics related to experimental design, data collection, and signal processing as well as review common procedures used to assess resistance vessel function, including postocclusive reactive hyperemia, passive limb movement, acute single limb exercise, and pharmacological interventions. Listen to this article’s corresponding podcast at https://ajpheart.podbean.com/e/guidelines-for-doppler-ultrasound-and-resistance-vessel-function/ .

Indices of leg resistance artery function are independently related to cycling V̇O 2 max

“…The results of this inquiry yielded two major findings. First, in agreement with current thought (Limberg et al, 2020;Thijssen, Black, et al, 2011), the assessments of conduit artery function (FMD and its derivatives) and resistance artery function (derivatives of RH, PLM, and ROV) appear to reflect two different aspects of vascular function, with the indices derived from the RH, PLM, and ROV being strongly correlated with each other, but not with FMD and its derivatives. The second major finding of this study is that leg vascular function, especially resistance artery function, is strongly related to VȮ 2 max, accounting for approximately 30% of the variance in VȮ 2 max not accounted for by known influencers, like body mass, sex, and BMI.…”

“…Therefore, in the current study vascular function was measured in multiple ways (FMD, RH, PLM, and ROV) on a group of young, healthy adults. As illustrated in Figure 1 and further described in Table 1, lower limb vascular function assessed by the resistance artery tests RH, PLM, and ROV exhibits strong relationships with each other (r = 0.54-0.83, p < .05), supporting the notion that they reflect some of the same physiological processes (Limberg et al, 2020). This comes in agreement with data from Rossman, Groot, Garten, Witman, & Richardson (2016) and Walker et al (2016) who observed significant correlations between PLM-induced hyperemia and RH in various populations.…”

“…As illustrated in Table 1, Factor 1 is comprised exclusively of FMD and factors derived from the FMD test, which have been suggested to represent conduit artery function (Thijssen, Black, et al, 2011). Meanwhile, Factor 2 was comprised of the main indices derived from RH, PLM, and ROV, all of which have recently been referred to as tests of resistance artery or resistance vessel function (Limberg et al, 2020). Thus, the current data indicate that the tests of resistance artery function used in the current study are relatively interchangeable, but that tests reflecting conduit artery function should not be considered as surrogates for tests of resistance artery function, or vice versa.…”

“…Multiple noninvasive assessments intended to interrogate the function of the resistance arteries (Limberg et al, 2020) of the lower limbs have been developed in recent years. Indeed, tests such as reactive hyperemia (RH) in response to cuff occlusion and removal, the hyperemic response to passive leg movement (PLM), and the rapid onset of vasodilation and hyperemia in response to a single muscle contraction (ROV) have been shown to be NO dependent (Broxterman et al, 2017;Casey, Walker, Ranadive, Taylor, & Joyner, 2013;Limberg et al, 2020) and related to peak blood flow during knee extension exercise (Hanson et al, 2020). Nevertheless, it is not clear if these distinct indices of vascular function actually reflect the same underlying physiology and are related to each other.…”

“…Nevertheless, it is not clear if these distinct indices of vascular function actually reflect the same underlying physiology and are related to each other. It is also unclear how relevant these indices of resistance artery function (Limberg et al, 2020) are to exercise capacity. If these indices of resistance artery vascular function truly are representative of the function of the resistance arteries, which are largely responsible for blood flow control (Joyner & Casey, 2015), one may expect them to relate well to exercise capacity.…”