Figure 3. Records of rib 10 displacement and pressure changes during isolated, spontaneous contraction of the diaphragm (A) and during mechanical ventilation (B) in a representative animal.

The external intercostal muscles in all interspaces were severed, and all the parasternal intercostal muscles but the one in the second left interspace were denervated or severed. The diaphragm, therefore, was the only muscle active during inspiration, and the trace of EMG activity (integrated signal) in the parasternal intercostal in the second left interspace provided the time reference. The traces of pleural (P_pl) and abdominal pressure (P_ab) are also shown. The rib moved cranially and outward (upward deflections) both during unimpeded inspiration and during single occluded breaths (breath after arrow in A); they also moved cranially and outward during mechanical, passive lung inflation (B).