An examination of the fast component of exercise hyperpnoea in humans.
Published: 2005
Language: eng
Number of pages: 190
Description: The onset of exercise is accompanied by a rapid increase in ventilation that is believed to arise from a combination of feed forward and feedback neural mechanisms. I completed five studies wherein I investigated the nature and behavior of these putative mechanisms in human subjects. In the first study I developed a mode of generating passive limb movement in order to study the drive to breathe from afferent feedback mechanisms. In the second study I investigated the mechanism(s) that brought about the observation that ventilation adapts during passive limb movement. In this study I concluded that the decline in ventilation that occurs during passive movement is due to an adaptation in the afferent feedback from the moving limbs, not a decline in carbon dioxide levels. Moreover, this adaptation affects the tidal volume component of ventilation and not breathing frequency. The third investigation was designed to investigate the contribution of central command and afferent feedback mechanisms to the rapid increase in ventilation that is observed at exercise onset. I studied the ventilatory response to the following transitions: rest to passive movement, passive to active movement, and rest to active movement. I found that all transitions were accompanied by rapid increases in ventilation, and that the values for ventilation and breathing frequency at the first point of active exercise were the same whether active exercise was started from rest or from a background of passive leg movement. My results therefore support the contention that both afferent feedback and central command mechanisms provide independent sources of ventilatory drive during exercise in humans. In studies 4 and 5, I wanted to investigate how wakefulness or arousal via a cognitive task might affect the initial increase in ventilation at the start of exercise. I found that when subjects were performing a mental task, the respiratory response to the onset of both passive and active movements was suppressed. Based upon this observation I developed an new empirical model, presented in chapter 5 that describes the drives to breathe at the onset of exercise in humans that includes the influence of behavior or arousal.
Notes: Thesis (Ph.D.)--University of Toronto, 2005.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 66-06, Section: B, page: 2896.