Modulation of the corticospinal control of ventilation by changes in reflex respiratory drive

Abstract

We have determined whether changes in PCO(2) above and below eucapnia modulate the precision of the voluntary control of breathing. Twelve trained subjects performed a compensatory tracking task in which they had to maintain the position of a cursor (perturbed by a variable triangular forcing function) on a fixed target by breathing in and out of a spirometer (ventilatory tracking; at 10 l/min). Before each task, subjects hyperventilated for 5 min, and the end-tidal PCO(2) (PET(CO(2))) was controlled; tracking was then performed separately at hypocapnia, eucapnia, and hypercapnia (PET(CO(2)) approximately 25, 37, and 43 Torr, respectively). Ventilatory tracking error was unchanged during hypocapnia (P > 0.05) but was significantly worse during hypercapnia (P < 0.003), compared with eucapnia; arm tracking error, performed as a control, was not significantly affected by PET(CO(2)) (P > 0. 05). In conclusion, ventilatory tracking performance is unaffected by the eucapnic PCO(2). From this, we suggest that resting breathing in awake humans may be independent of chemical drives and of the prevailing PCO(2).

The Contribution of Chemoreflex Drives to Resting Breathing in Man

“…Our estimation of the combined chemoreflex contribution to resting ventilation differs from that estimated by Corfield et al (1999). They estimated the contribution by calculating the error of a ventilatory tracking task during hypocapnia, eucapnia and hypercapnia.…”

“…However, Corfield et al (1999) have recently suggested that the contribution of the combined central and peripheral chemoreflexes to resting breathing may be inconsequential.…”

Electroencephalographic evidence for a respiratory-related cortical activity specific of the preparation of prephonatory breaths

“…These activities include activities relating to airway clearance (cough, sneezing) or to the need for food ingestion without aspiration (Bartlett and Leiter, 2012). They also include breathing behaviours depending on cortical networks that allow voluntary apnoea (McKay et al, 2008) and the execution of voluntary respiratory manoeuvres that can be complex and very precise (Colebatch et al, 1991;Corfield et al, 1999;Gandevia and Rothwell, 1987;Plotkin et al, 2010;Similowski et al, 1996). In humans, speech represents the most frequent disruption of automatic breathing by a voluntary activity.…”

Effects of pain and arousal on the control of breathing

“…However, even with most levels of anesthesia (e.g., supra minimum alveolar concentration [MAC] concentrations of inhalational anesthetics), painful surgical stimuli that do not elicit a purposeful movement will elicit a change in ventilation. The role of chemoreflexes in determining resting ventilation in awake subjects is subject to some controversy [6,7] and it may be that a "wakefulness drive", as proposed by Fink [8], plays a major part, possibly accounting for the often irregular breathing that is observed at rest.…”