Chest Wall Afferent Output

¹ Assistant Professor, Department of Medicine, University of British Columbia, Vancouver, Canada

The intercostal muscles, particularly the interosseous intercostals, contain many more proprioceptive afferents than the diaphragm or interchondral intercostals. This section of the chest wall, therefore, signals information regarding position, muscle length, and mild changes in muscle tension more effectively. Because of the complexity of the chest wall, much of this information can allow for regional adjustments during changes in posture and breathing. The major influence of intercostal afferents on the control of breathing at the supraspinal level appears to be inhibitory. The diaphragm, on the other hand, contains few such proprioceptive afferents. Recent results suggest that thin fiber afferents clearly influence breathing at the supraspinal level. More information is needed to determine what specific stimulae activate the receptors from which these fibers arise. Such information may clarify their role in conditions that may predispose to ventilatory failure. This information should also allow the specific reflex ventilatory effects produced by activation of these receptors to be defined.