title: Noninvasively determined muscle oxygen saturation is an early indicator of central hypovolemia in humans.
abstract: Ten healthy human volunteers were subjected to progressive lower body negative pressure (LBNP) to the onset of cardiovascular collapse to compare the response of noninvasively determined skin and fat corrected deep muscle oxygen saturation (SmO2) and pH to standard hemodynamic parameters for early detection of imminent hemodynamic instability. Muscle SmO2 and pH were determined with a novel near infrared spectroscopic (NIRS) technique. Heart rate (HR) was measured continuously via ECG, and arterial blood pressure (BP) and stroke volume (SV) were obtained noninvasively via Finometer and impedance cardiography on a beat-to-beat basis. SmO2 and SV were significantly decreased during the first LBNP level (-15 mmHg), whereas HR and BP were late indicators of impending cardiovascular collapse. SmO2 declined in parallel with SV and inversely with total peripheral resistance, suggesting, in this model, that SmO2 is an early indicator of a reduction in oxygen delivery through vasoconstriction. Muscle pH decreased later, suggesting an imbalance between delivery and demand. Spectroscopic determination of SmO2 is noninvasive and continuous, providing an early indication of impending cardiovascular collapse resulting from progressive reduction in central blood volume.
authors.affiliation: Dept. of Anesthesiology, UMass Medical School, 55 Lake Ave North, Worcester, MA 01655, USA. babs.soller@umassmed.edu
authors.forename: Babs R
authors.initials: BR
authors.lastname: Soller
authors.forename: Ye
authors.initials: Y
authors.lastname: Yang
authors.forename: Olusola O
authors.initials: OO
authors.lastname: Soyemi
authors.forename: Kathy L
authors.initials: KL
authors.lastname: Ryan
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Rickards
authors.forename: J Matthias
authors.initials: JM
authors.lastname: Walz
authors.forename: Stephen O
authors.initials: SO
authors.lastname: Heard
authors.forename: Victor A
authors.initials: VA
authors.lastname: Convertino
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D001794:Blood Pressure; D001810:Blood Volume; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D020896:Hypovolemia / Q000175:diagnosis* / Q000378:metabolism / Q000503:physiopathology; D008150:Lower Body Negative Pressure; D008297:Male; D008955:Models, Cardiovascular; D018482:Muscle, Skeletal / Q000378:metabolism*; D010100:Oxygen / Q000097:blood / Q000378:metabolism*; D010101:Oxygen Consumption; D012867:Skin / Q000378:metabolism; D013055:Spectrophotometry, Infrared; D013318:Stroke Volume; D013997:Time Factors; D014655:Vascular Resistance
chemical_list: D010100:Oxygen