Investigation of capnogram signal characteristics using statistical methods

This paper presents investigation on the characteristics of the capnogram. To date, all previous research conducted on capnogram signals were based on the fact that it is a stationary one. The analysis based on this assumption is limited to the use of certain conventional signal processing methods only. In this study, the first-order (mean and variance) and the second-order (autocorrelation) of asthmatics, and nonasthmatics patients´ capnogram are calculated. The results show that mean and variance of different segments of each signal are not the same as it should be in stationary signals. In addition, the autocorrelation function of each signal is independent at most of the time difference. Therefore, based on our findings in this paper, capnogram signals are in the category of wide-sense nonstationary random signals.