Breathing movements of the chest and abdominal wall in healthy subjects.

BACKGROUND Physical assessment of breathing is an important component of physical therapy evaluations. However, there are no standardized reference values of breathing movements available for use in clinical practice. The purpose of this study was to determine the 3-dimensional distances of observational points on the thorax and abdomen during breathing in healthy subjects and to assess the effects of age, posture, and sex on breathing movements. METHODS We studied the 3-dimensional breathing movement distances of the thorax and abdomen in 100 healthy subjects (50 males, 50 females). Breathing movements were measured with a 3-dimensional motion system during quiet and deep breathing with subjects in supine and sitting positions. Thirteen reflective markers were placed on the upper (the clavicles, 3rd ribs, and sternal angle) and lower thorax (the 8th ribs, 10th ribs, and xiphoid process) and the abdomen (upper abdomen and lateral abdomen). Range of movement in both breathing conditions was measured as the 3-dimensional distance at half respiratory cycle. Respiratory rates were calculated based on the breathing movements analyzed. One-way analysis of variance, t tests, and multiple regression were used for statistical analysis. RESULTS The average marker distances for the thorax and abdomen during quiet breathing were less than one third of those during deep breathing. Upper thoracic movement was significantly decreased with age. There was less abdominal movement in females than in males, except during quiet breathing in the supine position. The distances between the thoracic markers were greater and those of the abdomen were less during quiet and deep breathing in the sitting position, compared with those in the supine position. CONCLUSIONS We found that the observed breathing movements were related to the effects of age, sex, and posture. These findings are in agreement with those reported in previous studies. The results may be helpful in assessing breathing movement by physical examination.