A new method for 3D optical analysis of chest wall motion.

A method for kinematic analysis of chest wall motion is presented, based on a TV-image processor which allows a three-dimensional assessment of volume change of the trunk by automatically computing the co-ordinates of several passive markers placed on relevant landmarks of the thorax and abdomen. The parallel computation used for the image processing allows a real time recognition of the passive markers with the necessary accuracy. A geometric model also allows the on-line computation of the contribution to the chest volume by the different parts. For this purpose the model is based on 96 tetrahedrons which can be grouped into 16 compartments and into four sections representing: upper thorax (reflecting the action of neck and parasternal muscles and the effect of pleural pressure), lower thorax (reflecting the action of diaphragm and the effect of pleural and abdominal pressure), upper and lower abdomen (reflecting the actions of diaphragm and abdominal muscles). The volume can also be split into two vertical sections pointing out asymmetrics between the right and left side. The method is non-invasive, non-ionizing and leaves the subject maximum freedom of movement during the test, thus being suitable for routine clinical analysis. The monitoring of the subject can be prolonged in time and can be performed in different postures: standing, sitting, supine and lying on one side. The method was tested on eight healthy subjects showing good accuracy, reliability and reproducibility.