Figure 1. Measurements of the inspiratory rib cage depression indices. Ti = inspiratory time; Te = expiratory time. (a) Amplitude of the rib cage depression during inspiration. (d) Positive contribution of the thorax to inspiration. (b) Delay of the thoracic inward movement relative to that of abdomen at the end of inspiration. The amplitude index was calculated as: (a/a') x 100. The phase delay index was calculated as: (b/Ti) x 100.