Non-Invasive, Near Infrared Monitoring of Cellular Oxygen Sufficiency in Vivo
Since soft tissues, skin and bone are relatively translucent to near infrared (NIR) light and since cytochrome c oxidase possesses a redox dependent absorption band in that region, it appeared important to exploit these two co-incident properties in the development of a non-invasive technique to monitor sufficiency of O2 delivery to tissues in a variety of experimental and clinical situations. Aside from the enzyme and hemoglobin, in both the oxygenated (HbO2) and the deoxygenated (Hb) form, very few if any other tissue components possess absorption properties in the NIR and we found none that exhibited O2-dependent absorption changes. In order to correct the cyt a,a 3 signals for interference by changing perfusion, O2 saturation and O2 utilization conditions, means had to be found to strip out the contributions of HbO2 and Hb to the overall absorbance properties of the tissue or organ being monitored. Towards this purpose we designed and constructed a multiwavelength differential spectrophotometer for the monitoring of intact, normally circulated tissues, such as brain and muscle, through skin and bone. An outline of the biological and design principles, proof of method and a brief consideration of the data format and significance is given in this first preliminary report.
KeywordsCerebral Oxygen Utilization Condition Cerebral Vasculature Optic Fiber Bundle Blood Trace
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