title: Chemoreceptor Responsiveness at Sea Level Does Not Predict the Pulmonary Pressure Response to High Altitude.
abstract: BACKGROUND
  The hypoxic ventilatory response (HVR) at sea level (SL) is moderately predictive of the change in pulmonary artery systolic pressure (PASP) to acute normobaric hypoxia. However, because of progressive changes in the chemoreflex control of breathing and acid-base balance at high altitude (HA), HVR at SL may not predict PASP at HA. We hypothesized that resting oxygen saturation as measured by pulse oximetry (Spo₂) at HA would correlate better than HVR at SL with PASP at HA.
  
  
  METHODS
  In 20 participants at SL, we measured normobaric, isocapnic HVR (L/min · -%Spo₂⁻¹) and resting PASP using echocardiography. Both resting Spo₂ and PASP measures were repeated on day 2 (n = 10), days 4 to 8 (n = 12), and 2 to 3 weeks (n = 8) after arrival at 5,050 m. These data were also collected at 5,050 m in life-long HA residents (ie, Sherpa [n = 21]).
  
  
  RESULTS
  Compared with SL, Spo₂ decreased from 98.6% to 80.5% (P < .001), whereas PASP increased from 21.7 to 34.0 mm Hg (P < .001) after 2 to 3 weeks at 5,050 m. Isocapnic HVR at SL was not related to Spo₂ or PASP at any time point at 5,050 m (all P > .05). Sherpa had lower PASP (P < .01) than lowlanders on days 4 to 8 despite similar Spo₂. Upon correction for hematocrit, Sherpa PASP was not different from lowlanders at SL but was lower than lowlanders at all HA time points. At 5,050 m, although Spo₂ was not related to PASP in lowlanders at any point (all R² ≤ 0.05, P > .50), there was a weak relationship in the Sherpa (R² = 0.16, P = .07).
  
  
  CONCLUSIONS
  We conclude that neither HVR at SL nor resting Spo₂ at HA correlates with elevations in PASP at HA.
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, BC, Canada. Electronic address: ryanleohoiland@gmail.com.
authors.forename: Ryan L
authors.initials: RL
authors.lastname: Hoiland
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, BC, Canada.
authors.forename: Glen E
authors.initials: GE
authors.lastname: Foster
authors.affiliation: Division of Neurosurgery, Department of Clinical Neuroscience, University of Cambridge, Cambridge, England; Department of Physiology, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand.
authors.forename: Joseph
authors.initials: J
authors.lastname: Donnelly
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, BC, Canada.
authors.forename: Mike
authors.initials: M
authors.lastname: Stembridge
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, BC, Canada.
authors.forename: Chris K
authors.initials: CK
authors.lastname: Willie
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, BC, Canada.
authors.forename: Kurt J
authors.initials: KJ
authors.lastname: Smith
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, BC, Canada.
authors.forename: Nia C
authors.initials: NC
authors.lastname: Lewis
authors.affiliation: Department of Physiology, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand; School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand; School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand; School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, England.
authors.forename: Samuel J E
authors.initials: SJE
authors.lastname: Lucas
authors.affiliation: School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand.
authors.forename: Jim D
authors.initials: JD
authors.lastname: Cotter
authors.affiliation: Department of Cardiology, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
authors.forename: David J
authors.initials: DJ
authors.lastname: Yeoman
authors.affiliation: Department of Physiology, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand.
authors.forename: Kate N
authors.initials: KN
authors.lastname: Thomas
authors.affiliation: Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, AB, Canada.
authors.forename: Trevor A
authors.initials: TA
authors.lastname: Day
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, BC, Canada.
authors.forename: Mike M
authors.initials: MM
authors.lastname: Tymko
authors.affiliation: Cardiff School of Sport (Mr Stembridge), Cardiff Metropolitan University, Cardiff, Wales; Peninsula Sleep Laboratory, University of Sydney, Sydney, NSW, Australia; Department of Medicine, University of Sydney, Sydney, NSW, Australia.
authors.forename: Keith R
authors.initials: KR
authors.lastname: Burgess
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan, Kelowna, BC, Canada.
authors.forename: Philip N
authors.initials: PN
authors.lastname: Ainslie
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D000531:Altitude; D062186:Arterial Pressure / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology; D002628:Chemoreceptor Cells / Q000502:physiology*; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000209:etiology / Q000503:physiopathology*; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D010092:Oximetry; D010100:Oxygen / Q000097:blood; D011651:Pulmonary Artery / Q000503:physiopathology; D014655:Vascular Resistance / Q000502:physiology; D055815:Young Adult
chemical_list: D010100:Oxygen