M.D. Alekhin, L.N. Anishchenko, A.V. Zhuravlev, A.I. Dyachenko

Effective registration of external breathing parameters is an important aspect of both functional diagnostics and vital signs monitoring. For proper analysis of respiratory movements character and estimation of appropriate abdominal and thoracal components volume changes impedance and inductive respiratory plethysmography methods are mostly widespread. Nevertheless, when carrying out these types of clinical and laboratory research procedures at least two electrodes should be placed on the thorax with cabling or a pair of band perimetric abdominal and thoracal sensors should be fixed on a body. In a case of increased motion activity these circumstances usually cause an appearance of extraneous signal artifacts. Generally, applying contact sensors is an additional stress factor for patient which negatively influence on objectivity and quality of sleep. One of the novel non-contact methods of external breathing parameters registration is bio-radiolocation. During breathing process the presence of specific biometric modulation in bio-radar signal is mostly caused by reciprocal movements of skin of abdominal and thoracal areas due to periodic contractions of respiratory muscles. For clinical adoption of new remote approaches for reliable registration of breathing activity parameters their verification with standard contact methods is necessarily needed. Comparing of bio-radiolocation and respiratory plethysmography data during simultaneous registration of different types of breathing is for the first time performed in the paper. For defining functional relationships between the two signals in both time and frequency domains a range of methods based on calculation of pairwise correlation and spectral functions and estimation of their main generalized characteristics was used. The obtained values of cross-correlation coefficient from 0,84 to 0,94 denote close linear relationship between signals of bio-radar and abdominal band perimetric sensor in time domain. Calculated estimations of effective width of cross-spectrum show the cause to conclude that the main interaction power of these signals is concentrated in rather narrow frequency band corresponding to the range of breathing activity parameters registration. The obtained values of average levels of coherence in the range from 0,67 to 0,69 for quiet breathing and from 0,73 to 0,93 for hurried breathing in effective band of cross-spectrum denote statistical significance of pairwise spectral estimates and the presence of stable linear relationship between signals of bio-radar and respiratory plethysmograph in frequency domain. To conclude, the results of carried out pairwise correlation and spectral analysis of bio-radiolocation and respiratory plethysmography data for different types of breathing denoted close linear relationship between corresponding signals both in time and frequency domains. Thus, bio-radiolocation is supposed to be a reliable and effective approach for non-contact remote monitoring of respiration activity parameters.