Reliability of using the skin blood flow plateau response to local heating as a noninvasive assessment of nitric oxide-dependent vasodilation

Whether the noninvasive plateau phase of the skin blood flow response to local heating correlates with more invasive, direct quantification of the NO component is unresolved. To reliably quantify how well these two variables relate to each other, a large sample size is required. We therefore retrospectively analyzed data from 194 young adults at a control microdialysis site that was perfused with lactated Ringer's solution. Skin blood flow was measured using laser-Doppler flowmetry, and the skin was heated from 33 to 39°C. Perfusion of the nonspecific NO synthase inhibitor, N(G)-Nitro-L-arginine methyl ester (L-NAME) (20 mM), was used to quantify the NO component. Data were analyzed using multivariable linear regression. The local heating plateau and NO component were calculated and expressed in multiple ways based on a recently published analysis (Wolf ST, et al<i>. J Appl Physiol (1985)</i> 137: 1418-1424, 2024). There was a positive linear association between the local heating plateau, expressed as the total local heating response, and the NO component, expressed as Δ%CVC_max. The relation between the plateau and other indices of the NO component appears to largely depend on how the NO component is calculated and expressed. We also found that the relation between the total local heating response and Δ%CVC_max was not influenced by racial identity or biological sex. Our retrospective analysis of a large cohort of participants suggests that the noninvasive local heating plateau may serve as a reliable surrogate for the more invasive quantification of the NO component when the ability to use more invasive methods is not feasible.<b>NEW & NOTEWORTHY</b> The ability to assess NO-dependent dilation using noninvasive methods has important clinical implications. Here we show that there is a strong relationship between the skin blood flow plateau response to local heating (noninvasive) and directly quantified NO-dependent dilation (invasive).