Noninvasive optical quantification of cerebral venous oxygen saturation in humans.
OBJECTIVE
Cerebral oxygen extraction, defined as the difference between arterial and venous oxygen saturations (SaO2 and SvO2), is a critical parameter for managing intensive care patients at risk for neurological collapse. Although quantification of SaO2 is easily performed with pulse oximetry or moderately invasive arterial blood draws in peripheral vessels, cerebral SvO2 is frequently not monitored because of the invasiveness and risk associated with obtaining jugular bulb or super vena cava (SVC) blood samples.


METHODS
In this study, near-infrared spectroscopy (NIRS) was used to noninvasively measure cerebral SvO2 in anesthetized and mechanically ventilated pediatric patients (n = 10). To quantify SvO2, the NIRS signal component that fluctuates at the respiration frequency is isolated. This respiratory component is dominated by the venous portion of the interrogated vasculature. The NIRS measurements of SvO2 were validated against the clinical gold standard: invasively measured oxygen saturations from SVC blood samples. This technique was also applied in healthy volunteers (n = 5) without mechanical ventilation to illustrate its potential for use in healthy populations with natural airways.


RESULTS
Ten pediatric patients with pulmonary hypertension were studied. In these patients, SvO2 in the SVC exhibited good agreement with NIRS-measured SvO2 (R(2) = 0.80, P = .001, slope = 1.16 ± 0.48). Furthermore, in the healthy adult volunteers, mean (standard deviation) NIRS-measured SvO2 was 79.4 (6.8)%. This value is in good agreement with the expected average central venous saturation reported in literature.


CONCLUSIONS
Respiration frequency-selected NIRS can noninvasively quantify cerebral SvO2. This bedside technique can be used to help assess brain health in neurologically unstable patients.
University of Pennsylvania, Department of Physics and Astronomy, 209 South 33rd St, Philadelphia, PA 19104. Electronic address: jenlynch@sas.upenn.edu.
Jennifer M
JM
Lynch
Athinuola A. Martinos Center for Biomedical Imaging, The Optics Division, Charlestown, Massachusetts.
Erin M
EM
Buckley
Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
Peter J
PJ
Schwab
Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
David R
DR
Busch
Division of Cardiology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
Brian D
BD
Hanna
University of Pennsylvania, Department of Biostatistics and Epidemiology, Philadelphia, Pennsylvania.
Mary E
ME
Putt
Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
Daniel J
DJ
Licht
University of Pennsylvania, Department of Physics and Astronomy, 209 South 33rd St, Philadelphia, PA 19104.
Arjun G
AG
Yodh
D000293:Adolescent; D000465:Algorithms; D002550:Cerebral Veins / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000097:blood* / Q000175:diagnosis; D007223:Infant; D008297:Male; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000097:blood*; D011659:Pulmonary Gas Exchange; D012016:Reference Values; D015203:Reproducibility of Results; D012121:Respiration, Artificial; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
D010100:Oxygen
Near-infrared spectroscopy; cerebral venous oxygenation; noninvasive; pediatrics; validation