Development of Non-Invasive Deep Tissue pH Sensor.

A Phase I SBIR effort has demonstrated the feasibility of measuring deep tissue pH using near infrared reflection spectroscopy coupled with partial least squares multivariate calibration techniques. Measurement of pH with a breadboard system has been successfully demonstrated in skin covered rabbit muscle and in a canine heart on cardiopulmonary bypass. In six separate determinations of deep tissue pH in the rabbit teres major muscle, the derived model was capable of measuring pH from collected near-infrared spectra to an average accuracy of -0.006 0.009 pH units. By collecting data on both the canine heart and the rabbit muscle, the potential of this technique for diagnosis of ischemic conditions in muscle tissue has been shown. The Phase I effort has demonstrated the following characteristics for this pH measurement system significant measurement penetration down to a depth of 7 mm, insensitivity to probe height from skinmuscle surface, and a measurement time of under 15 seconds. The results of the Phase I effort are promising for development of a miniaturized, low cost non-invasive pH monitor system for assisting combat casualties in the field, as well as for many civilian medical applications, including cardiac and reconstructive surgery.