Rebuttal from Mounier and Brugniaux

Abstract

Point:CounterpointRebuttal from Mounier and BrugniauxPublished Online:15 May 2012https://doi.org/10.1152/japplphysiol.00067.2012cMoreSectionsPDF (39 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat By arguing for major physiological differences between normobaric (NH) and hypobaric (HH) hypoxia, Millet al. (7) are indirectly pleading for “real altitude” as the gold standard. In our opinion, hypobaric chambers represent nothing more than another (inaccurate?) model, inasmuch as real altitude involves more physiological constraints than simply a reduction in barometric pressure (PB). For instance, Mairbaurl et al. (6) demonstrated that the air dryness occurring at altitude could be misleading in the interpretation of the alterations in the alveolar epithelium.It is interesting to note that Millet et al. (7) also decided to highlight acute mountain sickness and preacclimatization as a point of debate in their argument. However, we have a completely different interpretation of the literature they cited. Essentially, the dose of hypoxia used by Beidleman et al. (1) during their preacclimatization is fundamentally different to what Fulco et al. (4) used (60 h at 4,300 m vs. 525 h at 2,200–3,100 m). We, therefore, argue that more than the changes in PB per se and fewer hours spent at a much lower altitude account for the discrepancy between these two studies. This is a clear illustration of the difficulties in interpreting the available literature, thus warranting further research.On the basis of our original contribution (8), the notion that the erythropoietin response is driven by changes in oxygen pressure (Po2) rather than PB is not subject of debate, which would tend to temper the alleged lack of efficiency of the normobaric living high-training low regimen (nLHTL). As a matter of fact, our group actually demonstrated a clear increase in both O2 carrying capacity and performance in elite athletes using nLHTL (2).Furthermore, the data presented by Millet al. (7) relating to nitric oxide (NO) and fluid balance are not convincing. For instance, the work from Hemmingsson and Linnarsson (5) has triggered heated discussions regarding the validity of the measurements, thus prompting us to the greatest caution regarding the interpretation of their results. Regarding fluid balance, Fall et al. (3) recently demonstrated in NH the role played by exercise and hypoxia on contracting plasma volume, independently of increased diuresis.All in all, although we acknowledge possible marginal differences between HH and NH, we stand by our point arguing that O2 sensing-related physiological adaptations are driven by Po2. However, based on existing gaps in the literature, we think more studies comparing the two models, especially those involving longer exposures, are required.REFERENCES1. Beidleman BA , Muza SR , Fulco CS , Cymerman A , Ditzler D , Stulz D , Staab JE , Skrinar GS , Lewis SF , Sawka MN. Intermittent altitude exposures reduce acute mountain sickness at 4300 m. Clin Sci (Lond) 106: 321–328, 2004.Crossref | PubMed | ISI | Google Scholar2. Brugniaux JV , Schmitt L , Robach P , Nicolet G , Fouillot JP , Moutereau S , Lasne F , Pialoux V , Saas P , Chorvot MC , Cornolo J , Olsen NV , Richalet JP. Eighteen days of “living high, training low” stimulate erythropoiesis and enhance aerobic performance in elite middle-distance runners. J Appl Physiol 100: 203–211, 2006.Link | ISI | Google Scholar3. Fall L , Evans KA , Lewis MH , Bailey DM. Haemostatic response to hypoxaemic/exercise stress: the dilemma of plasma volume correction. J Clin Pathol 64: 269–271, 2011.Crossref | ISI | Google Scholar4. Fulco CS , Muza SR , Beidleman BA , Demes R , Staab JE , Jones JE , Cymerman A. Effect of repeated normobaric hypoxia exposures during sleep on acute mountain sickness, exercise performance, and sleep during exposure to terrestrial altitude. Am J Physiol Regul Integr Comp Physiol 300: R428–R436, 2011.Link | ISI | Google Scholar5. Hemmingsson T , Linnarsson D. Lower exhaled nitric oxide in hypobaric than in normobaric acute hypoxia. Respir Physiol Neurobiol 169: 74–77, 2009.Crossref | ISI | Google Scholar6. Mairbaurl H , Weymann J , Mohrlein A , Swenson ER , Maggiorini M , Gibbs JS , Bartsch P. Nasal epithelium potential difference at high altitude (4,559 m): evidence for secretion. Am J Respir Crit Care Med 167: 862–867, 2003.Crossref | PubMed | ISI | Google Scholar7. Millet GP , Faiss R , Pialoux V. Point: Hypobaric hypoxia induces different physiological responses from normobaric hypoxia. J Appl Physiol; 10.1152/japplphysiol.00067.2012.ISI | Google Scholar8. Mounier R , Brugniaux JV. Counterpoint: Hypobaric hypoxia does not induce different physiological responses from normobaric hypoxia. J Appl Physiol; 10.1152/japplphysiol.00067a.2012.ISI | Google Scholar Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation More from this issue > Volume 112Issue 10May 2012Pages 1787-1787 Copyright & PermissionsCopyright © 2012 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.00067.2012cPubMed22589491History Published online 15 May 2012 Published in print 15 May 2012 Metrics