The strong light useful again
The researchers said their findings offer the potential for accurate and reliable monitoring of brain oxygenation during cardiac surgeries, to more effectively protect the brain against reduced oxygen levels, or anoxia, which is known to cause cognitive impairment in some surgical patients.
The monitor, called a cerebral oximeter, uses one or more sensors attached to the forehead that emit non-harmful, low-level laser light through the skin and skull into the brain. Since the near-infrared light absorption characteristics of the haemoglobin in red blood cells are known, the system can calculate the brain tissue oxygen saturation by measuring the differences in intensity of light as it passes through the brain.
The basic principle of cerebral oximetry is based on optical spectroscopy techniques. "It has always been a challenge to directly measure the oxygen levels in the brain," said anaesthesiologist David MacLeod, M.D., at Duke University Medical Center. "The main issues with the invasive approach are that it does not provide specific information in real time, and it is of course invasive, which can carry some risk to the patient.
For their study, the researchers enrolled twelve healthy volunteers. The volunteers were monitored using the different blood oxygenation measurement systems – pulse oximetry, jugular and radial arterial co-oximetry, and the prototype cerebral oximeter. In a stepwise fashion, the researchers decreased and then increased the concentration of inhaled oxygen through a range of 70 to 100 percent arterial blood oxygen saturation. Frequent, concurrent measurements were made on all three systems throughout the process.
"We made a total of 171 readings and found a strong correlation between the reference co-oximetry measurements by the invasive methods to the non-invasive approaches," MacLeod said.
COMPAMED.de; Source: Duke University Medical Center