Chemoreceptor Responsiveness at Sea Level Does Not Predict the Pulmonary Pressure Response to High Altitude

• Published in: Chest Vol. 148; no. 1; pp. 219 - 225
• Main Authors: Hoiland, Ryan L., BHK, Foster, Glen E., PhD, Donnelly, Joseph, MBChB, Stembridge, Mike, MSc, Willie, Chris K., PhD, Smith, Kurt J., MSc, Lewis, Nia C., PhD, Lucas, Samuel J.E., PhD, Cotter, Jim D., PhD, Yeoman, David J., BSc, Thomas, Kate N., BSc, Day, Trevor A., PhD, Tymko, Mike M., BHSc, Burgess, Keith R., MD, Ainslie, Philip N., PhD
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-07-2015
• Subjects: Acclimatization - physiology; Adult; Altitude; Arterial Pressure - physiology; Baroreflex - physiology; Chemoreceptor Cells - physiology; Female; Humans; Hypercapnia - etiology; Hypercapnia - physiopathology; Hypoxia - etiology; Hypoxia - physiopathology; Male; Oximetry; Oxygen - blood; Pulmonary Artery - physiopathology; Pulmonary/Respiratory; Vascular Resistance - physiology; Young Adult; high altitude; Sp o 2; HVR; hematocrit; PVR; HAPE; HPV; HCVR; SL; TRV; pulmonary artery pressure; hypoxic ventilatory response; pulmonary artery systolic pressure; hypoxic pulmonary vasoconstriction; tricuspid regurgitation jet velocity; e; hypercapnic ventilatory response; AMS; PASP; expired volume per unit time; P etco 2; partial pressure of end-tidal oxygen; partial pressure of end-tidal CO 2; P eto 2; high altitude pulmonary edema; HCT; HA; pulmonary vascular resistance; acute mountain sickness; oxygen saturation as measured by pulse oximetry; PAP; sea level; Spo2; Petco2; Peto2
• ISSN: 0012-3692; 1931-3543
• DOI: 10.1378/chest.14-1992

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 (Sp o2 ) 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 · −%Sp o2−1 ) and resting PASP using echocardiography. Both resting Sp o2 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, Sp o2 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 Sp o2 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 Sp o2 . 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 Sp o2 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 Sp o2 at HA correlates with elevations in PASP at HA.