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A revision of maximal oxygen consumption and exercise capacity at altitude 70 years after the first climb of Mount Everest
Full text linkOn the 70th anniversary of the first climb of Mount Everest by Edmund Hillary and Tensing Norgay, we discuss the physiological bases of climbing Everest with or without supplementary oxygen. After summarizing the data of the 1953 expedition and the effects of oxygen administration, we analyse the reasons why Reinhold Messner and Peter Habeler succeeded without supplementary oxygen in 1978. The consequences of this climb for physiology are briefly discussed. An overall analysis of maximal oxygen consumption (VO2max) at altitude follows. In this section, we discuss the reasons for the non-linear fall of VO2max at altitude, we support the statement that it is a mirror image of the oxygen equilibrium curve, and we propose an analogue of Hill's model of the oxygen equilibrium curve to analyse the VO2max fall. In the following section, we discuss the role of the ventilatory and pulmonary resistances to oxygen flow in limiting VO2max, which becomes progressively greater while moving toward higher altitudes. On top of Everest, these resistances provide most of the VO2max limitation, and the oxygen equilibrium curve and the respiratory system provide linear responses. This phenomenon is more accentuated in athletes with elevated VO2max, due to exercise-induced arterial hypoxaemia. The large differences in VO2max that we observe at sea level disappear at altitude. There is no need for a very high VO2max at sea level to climb the highest peaks on Earth. imageAbstract figure legend Maximal oxygen consumption (VO2max) shows a non-linear fall with altitude that is a mirror image of the oxygen equilibrium curve. Di Prampero and Ferretti were the first to associate the non-linear behaviour of the respiratory system to the oxygen equilibrium curve. On the other hand, Wagner constructed his convective curve accounting for the effects of the oxygen equilibrium curve. The decrease is more accentuated in athletic subjects with elevated VO2max compared to those who are non-athletic, so that the large differences in VO2max that are observed at sea level disappear at altitude. Such consequences are due to the effect of ventilatory and pulmonary resistances to oxygen flow in limiting VO2max, which becomes progressively greater while moving toward higher altitudes compared to that of the cardiovascular resistance. On top of Everest, the pulmonary resistances provide most of the VO2max limitation and the respiratory system provides linear responses. imag
Should Travelers with Hypertension Adjust Their Medications When Traveling to High Altitude?
No full textProgetto vincitore del concorso internazionale per il restauro dell'Orto Botanico di Padova
No full textSerum undercarboxylated osteocalcin was inversely associated with plasma glucose level and fat mass in type 2 diabetes mellitus
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Comment on: Acute kidney injury and rhabdomyolysis: a role for the regulator of G-protein signaling (RGS)-2
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Acute mountain sickness in a subject with metabolic syndrome at high altitude
No full textVisitors at high altitude are increasing in age and comorbidities, which can lead
to a failure in acclimatization. We describe the development of acute mountain
sickness (AMS) in a 44-year-old man with metabolic syndrome and the time- and
altitude-dependent correlation between the development of AMS and blood pressure
and heart rate changes. Our observations support a dominant role of endothelial
dysfunction in the pathogenesis of AMS and suggest new behavioral indications
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