Premium
NIRS‐derived Microvascular Oxygen Saturation Kinetics Related to Skeletal Muscle Metabolic Rate
Author(s) -
Margo Amadea C.,
Townsend Dana K.,
Hunt Brian E.,
Barstow Thomas J.
Publication year - 2020
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.2020.34.s1.06723
Subject(s) - oxygenation , chemistry , cuff , oxygen , myoglobin , forearm , oxygen saturation , reactive hyperemia , saturation (graph theory) , skeletal muscle , medicine , nuclear medicine , cardiology , anatomy , blood flow , surgery , biochemistry , mathematics , organic chemistry , combinatorics
Skeletal muscle tissue oxygen hemoglobin/myoglobin saturation (STO 2 ) measured during post occlusive reactive hyperemia (PORH) provides a kinetic parameter (STO 2 upslope (%/time)) that has increasingly been used as a measure of microvascular responsiveness. The magnitude of the oxygen saturation prior to cuff release (STO 2 min) often correlates to STO 2 upslope but the physiological variable associated with variability in STO 2 min is most likely muscle metabolic rate (MR). This physiologic variable likely influences the rate of reperfusion after cuff release. The purpose of this study, therefore, was to isolate variables contributing to differences in STO 2 upslope through their influence on STO 2 min. Our hypothesis was that MR would significantly affect STO 2 upslope. Methods The anterior antebrachium of twenty‐two (11 male, 11 female), 18–26 years, normoglycemic subjects was monitored continuously by near infrared spectroscopy during three upper limb PORH tests. Tissue oxygenation variables were determined prior to, during the cuff and for 2.5 min. post‐cuff release. MR was calculated in ml O 2 /100 g lean tissue/min and used both corrected and uncorrected for ATT (MR C ). Body fat and abdominal adiposity (%) were quantified by dual energy‐ray absorptiometry. Forearm adipose tissue thickness (ATT) (3.32 + 1.43 mm, range 2.8–6.7 mm) was measured by ultrasound. Results STO 2 min and STO 2 upslope were significantly negatively correlated (r=−0.47, P= 0.03) and both were significantly negatively correlated with MR (r = −0.75, P = <0.001 and r = −0.52, P = 0.01, respectively). In a multiple, forward step‐wise regression analysis with a dependent variable of STO2 upslope and independent variables of ATT, MR or MR C , STO2min, and total body fat, only ATT entered the equation (R squared 0.334, P= 0.006); no other variable statistically added any independent predictive power to the regression equation. Conclusions To our knowledge, this is the first study to assess the effects of MR on NIRS STO2 upslope. In contrast to our hypothesis, MR did not affect STO2 upslope but ATT did. This finding suggests that ATT must be taken into account when assuming differences in STO2 upslope reflect differences in microvascular reactivity even in largely lean subjects. Support or Funding Information American Heart Association, Grant/Award Number: 0151183ZWheaton College Alumni Summer Research Support