Evaluation of Chest Wall Motion Symmetry During Ventilation in Healthy Subjects by Optoelectronic Plethysmography

Pulmonary ventilation is the only macroscopically observable breathing step. The ventilatory mechanism has been extensively studied and knowledge of its operation is now well established. The thoraco-abdominal couple is generally considered as a homogeneous functional unit. The anatomical organization of the trunk is not symmetrical. The right lung receives 55% of the volume of air mobilized, the heart is usually lateralized to the left and exerts a mechanical stress on the left lung, the thoracic diaphragm is asymmetrical. The densities of the subdiaphragmatic viscera vary greatly between hollow organs (stomach, colon) and full organs (liver rate).

Conventional spirometry, the gold-standard reference method in ventilatory analysis, allows to measure the quantities of air mobilized at inspiration and expiration. This quantitative method does not provide information on the kinematics of the different areas of the thorax and abdomen involved during breathing.

Optoelectronic plethysmography (OEP) is a non-invasive technique for the analysis of the 3D motion of passive markers placed on the surface of the subject's chest, abdomen and back. This technique, validated as a reliable alternative to conventional spirometry, allows the combination of quantitative measurements of respiratory volumes with qualitative measurements of thoraco-abdominal kinematics. The OEP has the specificity of allowing to choose a segmentation of the trunk to analyze the kinematics of the different identified zones. The most commonly used method in research is segmentation into three compartments (pulmonary thoracic, abdominal and abdominal thoracic).

The OEP studies also suggested the use of segmentation in relation to the median plane of the body to compare the symmetry of the three compartments described above. This 6-compartment segmentation was rarely used in respiratory analysis to assess interventions such as surgery of pulmonary rehabilitation protocols. To our knowledge, there is no study in healthy subjects to assess the level of symmetry of pulmonary ventilation. This type of study is a fundamental preliminary step to be able to subsequently study the symmetry of the ventilatory kinematics in the case of pathologies giving deformities of the thorax, spine and abdomen (scoliosis for example).