Low cost optical plethysmography based on Kinect™ systems : a feasibility study

This work presents a feasibility study concerning a new low cost Optical Plethysmography based on the Kinect™ system. Optical methods do not disturb the breathing pattern due to the noninvasive principle of measurement. In fact these systems measure ventilation indirectly by recording the motion of the chest wall. The proposed method use four Kinect™ sensors, placed around the subject, to enable the tracking of the breathing chest wall. A CAD software is used to evaluate the chest wall surface and its absolute volume. The system is compared with the Opto-Electronic plethysmography, as it is used as a referent standard. The precision of the system shows a relative standard deviation (%RSD = 0,03%) one order of magnitude larger that the referent standard(%RDS = 0,03%). Moreover it shows a statistical significant agreement in estimation of tidal volume(r2 = 0,744, p<0,001) and Inspiratory Capacity (r2 =0,682, p<0,001), while it provides non-correlated estimates of Expiratory Reserve Volumes (r2 =0,219, p=0,012). These results demonstrate the proposed optical method presents value not usable for diagnostic purpose, but represents a good start point for cheap, portable, contactless solutions.