| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Departments of 1Medicine and 2Population Health Sciences, University of Wisconsin, and 3Middleton Memorial Veterans Hospital, Madison, Wisconsin
Submitted 20 April 2005 ; accepted in final form 15 September 2005
To investigate the contribution of the peripheral chemoreceptors to the susceptibility to posthyperventilation apnea, we evaluated the time course and magnitude of hypocapnia required to produce apnea at different levels of peripheral chemoreceptor activation produced by exposure to three levels of inspired PO2. We measured the apneic threshold and the apnea latency in nine normal sleeping subjects in response to augmented breaths during normoxia (room air), hypoxia (arterial O2 saturation = 78–80%), and hyperoxia (inspired O2 fraction = 50–52%). Pressure support mechanical ventilation in the assist mode was employed to introduce a single or multiple numbers of consecutive, sighlike breaths to cause apnea. The apnea latency was measured from the end inspiration of the first augmented breath to the onset of apnea. It was 12.2 ± 1.1 s during normoxia, which was similar to the lung-to-ear circulation delay of 11.7 s in these subjects. Hypoxia shortened the apnea latency (6.3 ± 0.8 s; P < 0.05), whereas hyperoxia prolonged it (71.5 ± 13.8 s; P < 0.01). The apneic threshold end-tidal PCO2 (PETCO2) was defined as the PETCO2 at the onset of apnea. During hypoxia, the apneic threshold PETCO2 was higher (38.9 ± 1.7 Torr; P < 0.01) compared with normoxia (35.8 ± 1.1; Torr); during hyperoxia, it was lower (33.0 ± 0.8 Torr; P < 0.05). Furthermore, the difference between the eupneic PETCO2 and apneic threshold PETCO2 was smaller during hypoxia (3.0 ± 1.0 Torr P < 001) and greater during hyperoxia (10.6 ± 0.8 Torr; P < 0.05) compared with normoxia (8.0 ± 0.6 Torr). Correspondingly, the hypocapnic ventilatory response to CO2 below the eupneic PETCO2 was increased by hypoxia (3.44 ± 0.63 l·min–1·Torr–1; P < 0.05) and decreased by hyperoxia (0.63 ± 0.04 l·min–1·Torr–1; P < 0.05) compared with normoxia (0.79 ± 0.05 l·min–1·Torr–1). These findings indicate that posthyperventilation apnea is initiated by the peripheral chemoreceptors and that the varying susceptibility to apnea during hypoxia vs. hyperoxia is influenced by the relative activity of these receptors.
apnea threshold
This article has been cited by other articles:
|
|
 |
|
  A. Xie, J. B. Skatrud, S. R. Barczi, K. Reichmuth, B. J. Morgan, S. Mont, and J. A. Dempsey Influence of cerebral blood flow on breathing stability J Appl Physiol, March 1, 2009; 106(3): 850 - 856. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Kohler, S. Kriemler, E. M. Wilhelm, H. Brunner-LaRocca, M. Zehnder, and K. E. Bloch Children at high altitude have less nocturnal periodic breathing than adults Eur. Respir. J., July 1, 2008; 32(1): 189 - 197. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. K. Stickland, B. J. Morgan, and J. A. Dempsey Carotid chemoreceptor modulation of sympathetic vasoconstrictor outflow during exercise in healthy humans J. Physiol., March 15, 2008; 586(6): 1743 - 1754. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. N. Ainslie, K. Burgess, P. Subedi, and K. R. Burgess Alterations in cerebral dynamics at high altitude following partial acclimatization in humans: wakefulness and sleep J Appl Physiol, February 1, 2007; 102(2): 658 - 664. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Xie, J. B. Skatrud, B. Morgan, B. Chenuel, R. Khayat, K. Reichmuth, J. Lin, and J. A. Dempsey Influence of cerebrovascular function on the hypercapnic ventilatory response in healthy humans J. Physiol., November 15, 2006; 577(1): 319 - 329. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
