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CARDIOVASCULAR
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Volume 5, 2000, No 4 |
Simultaneous
Monitoring of Cerebral Oxygenation using the NIRS-300 and OS-30 Near-Infrared
Spectrophotometry Devices
G. Nollert, S. Hoerstrup, P. Khalil, S. Däbritz, M. Nagashima, R. A.
Jonas
Background:
Commercially available near infrared spectrophotometry (NIRS) devices allow only
for relative measurements of chromophores like hemoglobin (Hb), oxygenated
hemoglobin (HbO2) and oxidized cytochrome a,a3 (CytOx) in
brain tissue. A new NIRS device, the OS-30, claims to give absolute measurements
for a very small tissue volume directly under the probe. We compared the OS-30
with a different NIRS device, the NIRO-300 in a piglet model. The NIRO-300 works
with two different algorithms to calculate a tissue oxygenation index (TOI) and
to measure changes in Hb and HbO2.
Methods:
Ten piglets were submitted to seven different ventilation conditions lasting 30
min. Before and after every ventilation period blood gases were taken from the
jugular bulb and femoral artery. Blood gas parameters and changes in blood gas
parameters during a ventilation period were compared to NIRS parameters and
their changes. The values obtained with both devices were compared. Additionally,
the relationships between the NIRO-300 parameters TOI, Hb, and HbO2
were analyzed.
Results:
Absolute
OS-30 measurements do not correlate with blood gases and only very weakly with
NIRO-300 CytOx (r=0.37) measurements. Brain tissue saturation values of both
devices were 20% to 45% lower than jugular bulb saturation. Changes in the CytOx
signal of both devices correlated with changes in jugular bulb venous pH and PCO2.
The Hb and HbO2 values correlated with the TOI parameter (r=0.496 and
r=0.652 resp; p<0.01) and it was possible to show a linear relationship
(r=0.995; p<0.001).
Conclusions:
Absolute measurements of the OS-30 device do not reflect overall brain
oxygenation in pigs and are not correlated to other NIRS measurements; however
this instrument may be useful to measure trends. The TOI parameter of the
NIRO-300 device correlates with jugular bulb hemoglobin saturation and
simultaneous HbO2 and Hb values; however, the absolute values are too
low.
(CVE. 2000; 5 (4): 271-275)
Key words: NIRS, cytochrome a,a3, hyperoxia, hypocarbia, hypercarbia, cerebral oxygenation
Richard
A. Jonas, M.D.
Department of Cardiac Surgery
The Children’s Hospital
Harvard Medical School
300 Longwood Ave.
Boston, MA 02115
USA
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