Skip to main content Accessibility help
×
Home
Hostname: page-component-99c86f546-md8df Total loading time: 0.126 Render date: 2021-11-27T04:13:32.427Z Has data issue: true Feature Flags: { "shouldUseShareProductTool": true, "shouldUseHypothesis": true, "isUnsiloEnabled": true, "metricsAbstractViews": false, "figures": true, "newCiteModal": false, "newCitedByModal": true, "newEcommerce": true, "newUsageEvents": true }

Body position and cardiac dynamic and chronotropic responses to steady-state isocapnic hypoxaemia in humans

Published online by Cambridge University Press:  25 January 2001

S. Deborah Lucy
Affiliation:
Department of Physiology, Faculty of Medicine and ÓSchool of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada N6A 5C1 and Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
Richard L. Hughson
Affiliation:
Department of Physiology, Faculty of Medicine and ÓSchool of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada N6A 5C1 and Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
John M. Kowalchuk
Affiliation:
Department of Physiology, Faculty of Medicine and ÓSchool of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada N6A 5C1 and Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
Donald H. Paterson
Affiliation:
Department of Physiology, Faculty of Medicine and ÓSchool of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada N6A 5C1 and Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
David A. Cunningham
Affiliation:
Department of Physiology, Faculty of Medicine and ÓSchool of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada N6A 5C1 and Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
Get access

Abstract

Neural mediation of the human cardiac response to isocapnic (IC) steady-state hypoxaemia was investigated using coarse-graining spectral analysis of heart rate variability (HRV). Six young adults were exposed in random order to a hypoxia or control protocol, in supine and sitting postures, while end-tidal PCO2 (PET,CO2) was clamped at resting eucapnic levels. An initial 11 min period of euoxia (PET,O2 100 mmHg; 13.3 kPa) was followed by a 22 min exposure to hypoxia (PET,O2 55 mmHg; 7.3 kPa), or continued euoxia (control). Harmonic and fractal powers of HRV were determined for the terminal 400 heart beats in each time period. Ventilation was stimulated (P < 0.05) and cardiac dynamics altered only by exposure to hypoxia. The cardiac interpulse interval was shortened (P < 0.001) similarly during hypoxia in both body positions. Vagally mediated high-frequency harmonic power (Ph) of HRV was decreased by hypoxia only in the supine position, while the fractal dimension, also linked to cardiac vagal control, was decreased in the sitting position (P < 0.05). However, low-frequency harmonic power (Pl) and the HRV indicator of sympathetic activity (Pl/Ph) were not altered by hypoxia in either position. These results suggest that, in humans, tachycardia induced by moderate IC hypoxaemia (arterial O2 saturation Sa,O2 85 %) was mediated by vagal withdrawal, irrespective of body position and resting autonomic balance, while associated changes in HRV were positionally dependent.

Type
Research Article
Copyright
© The Physiological Society 2000

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Send article to Kindle

To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

Note you can select to send to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Body position and cardiac dynamic and chronotropic responses to steady-state isocapnic hypoxaemia in humans
Available formats
×

Send article to Dropbox

To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

Body position and cardiac dynamic and chronotropic responses to steady-state isocapnic hypoxaemia in humans
Available formats
×

Send article to Google Drive

To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

Body position and cardiac dynamic and chronotropic responses to steady-state isocapnic hypoxaemia in humans
Available formats
×
×

Reply to: Submit a response

Please enter your response.

Your details

Please enter a valid email address.

Conflicting interests

Do you have any conflicting interests? *