| Popis: |
In this study we tested the hypothesis that the stimulatory hypercapnic ventilatory response (HCVR) would be less in quadriplegic patients. Apart from the sheer exclusion of a substantial part of the effector of the respiratory control system due to paralysis of the respiratory muscles of the chest and abdominal wall, two lines of evidence suggest such a possibility. First, these muscles contain a rich network of mechanoreceptors, muscle spindles, and tendon organs, which are classified as proprioceptors. There is evidence showing that afferent information from these proprioceptors exerts, via ascending spinal pathways, a reflex effect on the central control of respiration, modulating the descending drive to phrenic and intercostal spinal motoneurons (Shannon, 1986). Second, chemoreceptor afferents might have a facilitatory effect on the descending drive to respiratory muscle neurons independent of the proprioceptive influences. Recent studies have shown that hypercapnia increases both internal intercostal (Fregosi and Bartlett, 1989) and abdominal expiratory (Ledlie et al.,1983) nerve activities in the absence of proprioceptive feedback from the body wall. |
