In-vivo study on the stability of the use of gas absorption spectroscopy as a technology for assessing sinus cavity size and oxygen gas concentration

Abstract: Sinusitis is a common disease caused by a virus or bacteria, with 84% to 91% of cases caused by a viral pathogen. However, physicians prescribe antibiotics for this disease in 85% of all cases. GPX Medical is a company working on the development of a medical device which, by means of absorption spectroscopy, can determine whether the disease is caused by virus or bacteria supporting, thus, the doctors in decision making. The main purpose of this study is to evaluate the stability of the measurements performed by this medical device, by analyzing the maxillary sinuses size and O2 concentration in different subjects under a longer period. The first step consisted in performing a pilot study to determine the measurement geometries, number of samples and the updating time for the laser by analyzing a 3-D model of the sinuses and the strength of the signal. This was followed by a preclinical study where measurements on sinuses size and O2 concentration of five healthy volunteers were performed over a period of one-day, one-week and one-month to analyze the intra- and intersubject variability, and determine the best measurement geometry. This pilot study revealed an optimal number of samples of 30 and an optimal updating time for the laser of 2s. From the preclinical study it resulted that the best measurement position is the palate-cheekbone geometry (position 1), which was determined by analyzing the signal strength. The results of the preclinical study show a certain stability of the measurements with low intrasubject variability in most cases, accompanied by differences between the right and the left side, and a higher intersubject variability. However, for better results a newer fiber should be used in the measurements for position 1 and 2.