Motion Capture-based Respiratory Monitor in Small Animals

Abstract

Several methods for monitoring the respiratory status of small experimental animals are available; however, most of them are invasive and are not suitable for use with free-moving animals. A 3-dimensional (3D) motion capturing method is widely used for monitoring and analyzing the motion of moving objects. In this study, we examined whether or not this method is capable of monitoring the respiratory status of small animals and explored the potential use for less invasive monitoring method for the free-moving small animals. 21 markers that reflect near-infrared (NIR) light were attached to the skin of the trunk of an anesthetized rat. The body movement synchronized with spontaneous respiration was detected using eight NIR video-cameras that emitted a weak NIR light and captured the reflected NIR light from the markers. The respiratory status was analyzed by calculating the change in volume of a virtual polyhedron, for which the attached makers were regarded as vertexes. The 3D motion capturing system detected the chest movement with a spatial resolution of 0.26 mm and a time resolution of 4 msec. Volumetric analysis of the virtual polyhedron provided the respiratory rate, allowing monitoring of respiratory fluctuation induced by hypoxia. This study demonstrates that a 3D motion capturing system can be used as a noninvasive monitoring method for checking the respiratory status of small animals.