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Effect of Acute Local Heating on Lower Extremity Macro‐ and Microvascular Dilator Function in Humans
Author(s) -
Romero Steven A.,
Gag Daniel,
Cramer Matthew N.,
Simmons Grant H.,
Pellinger Thomas K.,
Poh Paula Y.S.,
Kouda Ken,
Crandall Craig G.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.lb671
Subject(s) - dilator , medicine , femoral artery , blood flow , reactive hyperemia , anatomy , cardiology , surgery
Local heating of an extremity increases blood flow and vascular shear stress throughout the arterial vascular tree. Local heating acutely improves macrovascular dilator function in the upper extremities through a shear stress dependent mechanism. However, the effect of local heating on macro‐and microvascular dilator function of the lower extremities is unclear. Therefore, the purpose of this study was to test the hypothesis that acute local heating improves lower extremity macro‐ and microvascular dilator function. Five healthy subjects (2 females; age 27 ± 4 years; height 166 ± 4 cm; weight 65 ± 7 kg; mean ± SD) immersed their lower extremities at a depth of ~33 cm into a circulated water bath (42.5 ± 0.4°C) for 45 min. Superficial femoral artery blood flow and diameter (Doppler ultrasound) were measured prior to and every 15 min during heating. Intestinal temperature, skin and skeletal muscle temperatures of the calf were measured. Prior to and 30 min after heating, macro‐ (flow‐mediated dilation) and microvascular (3 min reactive hyperemia area under the curve) dilator function were assessed in the superficial femoral artery following 5 min of arterial occlusion. Local heating increased superficial femoral artery blood flow (pre 63.7 ± 10.8 mL min −1 vs. 45 min local heating 606.3 ± 54.3 mL min −1 ) and shear rate (pre 51.5 ± 12.9 s −1 vs. 45 min local heating 410.6 ± 70.9 s −1 ; both P < 0.05). Intestinal temperature (Δ0.7 ± 0.1°C), calf skin temperature (Δ9.1 ± 0.1°C), and muscle temperature (Δ8.3 ± 0.6°C; all P < 0.05) increased at 45 min local heating. Macrovascular dilator function was unchanged following heating (pre 4.6 ± 1.1% vs. post 4.6 ± 0.7%; P = 0.8). Microvascular dilator function increased following local heating (pre 456 ± 89 mL vs. post 605 ± 101 mL; P = 0.02). However, after normalizing for differences in baseline blood flow, microvascular dilator function did not differ (pre 423 ± 71 mL vs. post 556 ± 91 mL; P = 0.2). Taken together, local heating of the lower extremities increases blood flow and shear rate similar to that previously observed in the upper extremities. However, these data suggest that these hemodynamic changes do not improve lower extremity macro‐ or microvascular dilator function following local heating in healthy humans. Support or Funding Information Funded by National Institutes of Health (GM‐068865).