Abstract
Respiratory gas analyzers to measure functions such as ventilation volume respiratory rate are expensive, and patients with severe motor and intellectual disabilities (SMID) often remove the devices, increasing contact risk and making them difficult to use in institutions. We propose here an inexpensive, non-contact method of measuring respiratory function using the depth camera introduced in our previous study. The method includes an algorithm that differentiates between body tremors, and between movements peculiar to patients with SMID and those caused by respiration, while further detecting appropriate respiration. However, the previous region of interest (ROI) was limited to a simple rectangular area from the navel to the xiphoid process, and we did not compare measurements using the geometry of the thorax and the abdomen as the ROI. In this study, we performed non-contact respiratory measurement using the geometric shape of the upper body of patients as the ROI, and investigated the improvement of measurement accuracy when the ROI was set according to the individual patient’s body. The results indicated that the values from the new method approached those of the respiratory gas analyzer more closely than the conventional method, and its measurement performance was sufficient for respiratory rehabilitation evaluation. We also found that the measured respiratory signal correlated with the ventilation rate in respiration with large ventilation rate fluctuations, and that the respiratory rhythm abnormalities associated with ventilation rate changes could be measured by the respiratory rate per min and apnea time per min evaluation indices.