Infrared imaging of nitric oxide-mediated blood flow in human sickle cell disease

Abstract

Vascular dysfunction is an important pathophysiologic manifestation of sickle cell disease (SCD), a condition that increases risk of pulmonary hypertension and stroke. We hypothesized that infrared (IR) imaging would detect changes in cutaneous blood flow reflective of vascular function. We performed IR imaging and conventional strain gauge plethysmography in twenty-five adults with SCD at baseline and during intra-arterial infusions of an endothelium-dependent vasodilator acetylcholine (ACh), an endothelium-independent vasodilator sodium nitroprusside (SNP), and a NOS inhibitor L-NMMA. Skin temperature measured by IR imaging increased in a dose-dependent manner to graded infusions of ACh (+1.1° C, p < 0.0001) and SNP (+0.9° C, p < 0.0001), and correlated with dose-dependent increases in forearm blood flow (ACh: +19.9 mL/min/100mL, p < 0.0001; rs = 0.57, p = 0.003; SNP: +8.6 mL/min/100mL, p < 0.0001; r = 0.70, p = 0.0002). Although IR measurement of skin temperature accurately reflected agonist-induced increases in blood flow, it was less sensitive to decreases in blood flow caused by NOS inhibition. Baseline forearm skin temperature measured by IR imaging correlated significantly with baseline forearm blood flow (31.8±0.2° C, 6.0±0.4 mL/min/100mL; r = 0.58, p = 0.003), and appeared to represent a novel biomarker of vascular function. It predicted a blunted blood flow response to SNP (r = −0.61, p = 0.002), and was independently associated with a marker of pulmonary artery pressure, as well as hemoglobin level, diastolic blood pressure, homocysteine, and cholesterol (R2 = 0.84, p < 0.0001 for the model). IR imaging of agonist-stimulated cutaneous blood flow represents a less cumbersome alternative to plethysmography methodology. Measurement of baseline skin temperature by IR imaging may be a useful new marker of vascular risk in adults with SCD.

Ultrathin conformal devices for precise and continuous thermal characterization of human skin

“…3d have diagnostic value for conditions such as congestive heart disease and tissue hypoxia 11 , and disturbances in skin blood flow may reflect functional changes due to disease in other important organ systems 12 . As small skin temperature changes correlate with tissue blood flow 13 , they can serve as naturally occurring markers for monitoring periodic contraction and dilation of the vessels (vasomotion). Previous studies of oscillatory behaviour in blood flow at low frequencies suggest correlations to local vasomotions controlled by endothelium-derived hyperpolarizing factor (0.005–0.0095 Hz), rate of endothelial release of nitric oxide (0.0095–0.02 Hz), and sympathetic activity (0.02–0.06 Hz; ref.…”

Epidermal photonic devices for quantitative imaging of temperature and thermal transport characteristics of the skin

“…Spatiotemporal mapping even with passive e-TLC systems yields useful information on blood circulation 49,50 , maximal percentage increase in blood flow rate after occlusion 51 and duration of reactive hyperaemia 52 . Measurements of temperature fluctuations above the ulnar artery and adjacent veins serve as an important part of a reactive hyperaemia protocol.…”

Rapid vs. delayed infrared responses after ischemia reveal recruitment of different vascular beds

“…Temperature calibration was performed prior to imaging as previously described. [4] IR images were displayed in real time, allowing immediate observation of gross changes in arm perfusion. The IR images were then saved as an image cube for subsequent offline analysis.…”

“…[2, 3] A study by Gorbach et al showed that skin temperature correlated significantly with forearm blood flow in patients with sickle cell anaemia. [4] To assess blood flow dynamics in healthy subjects, the post-occlusive reactive hyperemia (PORH) test, a standard test of circulatory function, was combined with IR imaging of the volar aspect of the forearm. IR measurements were validated through comparison with blood flux measurements using laser Doppler flowmetry probes.…”