Divergent expiratory braking activity of costal and crural diaphragm.

Background: There is increasing clinical interest in understanding the contribution of the diaphragm in early expiration, especially during mechanical ventilation. However, current experimental evidence is limited, so essential activity of the diaphragm during expiration and diaphragm segmental differences in expiratory activity, are unknown.

Objectives: To determine if: 1) the diaphragm is normally active into expiration during spontaneous breathing and hypercapnic ventilation, 2) expiratory diaphragmatic activity is distributed equally among the segments of the diaphragm, costal and crural.

Expiratory and inspiratory action of transversus abdominis during eupnea and hypercapnic ventilation.

Background: Recently, there is interest in the clinical importance of monitoring abdominal muscles during respiratory failure. The clinical interpretation relies on the assumption that expiration is a passive physiologic process and, since diaphragm and abdomen are arranged in series, any inward motion of the abdominal wall represents a sign of diaphragm dysfunction. However, previous studies suggest transversus abdominis might be active even during eupnea and is preferentially recruited over the other abdominal muscles.

Parasternal intercostal function during sustained hypoxia.

Ventilatory response to sustained isocapnic hypoxia in adult humans and other mammals is characterized by a biphasic pattern, with attenuation of neuromotor output to the diaphragm. However, there is no a priori reason that hypoxia-mediated attenuation of respiratory drive would be a common event among other respiratory muscles. At present, little is known about the function of the chest wall muscles during sustained hypoxia.

Parasternal intercostal, costal, and crural diaphragm neural activation during hypercapnia.

The parasternal intercostal is an obligatory inspiratory muscle working in coordination with the diaphragm, apparently sharing a common pathway of neural response. This similarity has attracted clinical interest, promoting the parasternal as a noninvasive alternative to the diaphragm, to monitor central neural respiratory output. However, this role may be confounded by the distinct and different functions of the costal and crural diaphragm.