Alveolar PCO2 oscillations and ventilation at sea level and at high altitude

• Published in: Journal of applied physiology (1985) 2008-02, Vol.104 (2), p.404-415
• Main Authors: Collier, D. J, Nickol, A. H, Milledge, J. S, van Ruiten, H. J. A, Collier, C. J, Swenson, E. R, Datta, Avijit, Wolff, C. B
• Format: Article
• Language: English
• Subjects: Acclimatization; Acetazolamide - pharmacology; Acute Disease; Administration, Inhalation; Altitude; Bicycling; Biological and medical sciences; Carbon Dioxide - administration & dosage; Carbon Dioxide - metabolism; Chemoreceptor Cells - metabolism; Chronic Disease; Exercise; Fundamental and applied biological sciences. Psychology; Humans; Hypercapnia - metabolism; Hypercapnia - physiopathology; Hypoxia - metabolism; Hypoxia - physiopathology; Inhalation; Mountaineering; Oxygen - administration & dosage; Periodicity; Pulmonary Alveoli - drug effects; Pulmonary Alveoli - metabolism; Pulmonary Alveoli - physiopathology; Pulmonary Ventilation - drug effects; Time Factors
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00166.2007

1 William Harvey Research Institute, Barts & The London Queen Mary School of Medicine & Dentistry, Charterhouse Square, London; 2 Oxford Centre for Respiratory Medicine, Churchill Hospital, Oxford; 3 Department of Respiratory Medicine, Northwick Park Hospital, Harrow, United Kingdom; 4 Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands; 5 Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington; and 6 York Hospitals NHS Foundation Trust, York, United Kingdom Submitted 9 February 2007 ; accepted in final form 21 October 2007 This study examines the potential for a ventilatory drive, independent of mean P CO 2 , but depending instead on changes in P CO 2 that occur during the respiratory cycle. This responsiveness is referred to here as "dynamic ventilatory sensitivity." The normal, spontaneous, respiratory oscillations in alveolar P CO 2 have been modified with inspiratory pulses approximating alveolar P CO 2 concentrations, both at sea level and at high altitude (5,000 m, 16,400 ft.). All tests were conducted with subjects exercising on a cycle ergometer at 60 W. The pulses last about half the inspiratory duration and are timed to arrive in the alveoli during early or late inspiration. Differences in ventilation, which then occur in the face of similar end-tidal P CO 2 values, are taken to result from dynamic ventilatory sensitivity. Highly significant ventilatory responses (early pulse response greater than late) occurred in hypoxia and normoxia at sea level and after more than 4 days at 5,000 m. The response at high altitude was eliminated by normalizing P O 2 and was reduced or eliminated with acetazolamide. No response was present soon after arrival (