The Effect of a 300 mBar Increase in Barometric Pressure on Digital Microcirculation in Healthy Subjects Exposed to High Altitude: Is the Use of a Portable Hyperbaric Chamber to Treat Frostbite and/or Hypothermia in the Field Indicated? (Flow_Pulse Study)

2019 ◽  
Vol 20 (1) ◽  
pp. 56-60 ◽  
Author(s):  
Yann Savina ◽  
Sandra Leal ◽  
Pascal Zellner ◽  
François Becker ◽  
Monica Piris ◽  
...  
Keyword(s):  
High Altitude ◽  
Healthy Subjects ◽  
Barometric Pressure ◽  
Hyperbaric Chamber

Improvement in lung diffusion by endothelin A receptor blockade at high altitude

2012 ◽  
Vol 112 (1) ◽  
pp. 20-25 ◽  
Author(s):  
Claire de Bisschop ◽  
Jean-Benoit Martinot ◽  
Gil Leurquin-Sterk ◽  
Vitalie Faoro ◽  
Hervé Guénard ◽  
...  
Keyword(s):  
High Altitude ◽  
Sea Level ◽  
Exercise Capacity ◽  
Barometric Pressure ◽  
Membrane Component ◽  
Alveolar Volume ◽  
Double Blind ◽  
Lung Diffusion ◽  
Endothelin A Receptor ◽  
Endothelin A

Lung diffusing capacity has been reported variably in high-altitude newcomers and may be in relation to different pulmonary vascular resistance (PVR). Twenty-two healthy volunteers were investigated at sea level and at 5,050 m before and after random double-blind intake of the endothelin A receptor blocker sitaxsentan (100 mg/day) vs. a placebo during 1 wk. PVR was estimated by Doppler echocardiography, and exercise capacity by maximal oxygen uptake (V̇o2 max). The diffusing capacities for nitric oxide (DLNO) and carbon monoxide (DLCO) were measured using a single-breath method before and 30 min after maximal exercise. The membrane component of DLCO (Dm) and capillary volume (Vc) was calculated with corrections for hemoglobin, alveolar volume, and barometric pressure. Altitude exposure was associated with unchanged DLCO, DLNO, and Dm but a slight decrease in Vc. Exercise at altitude decreased DLNO and Dm. Sitaxsentan intake improved V̇o2 max together with an increase in resting and postexercise DLNO and Dm. Sitaxsentan-induced decrease in PVR was inversely correlated to DLNO. Both DLCO and DLNO were correlated to V̇o2 max at sea level ( r = 0.41–0.42, P < 0.1) and more so at altitude ( r = 0.56–0.59, P < 0.05). Pharmacological pulmonary vasodilation improves the membrane component of lung diffusion in high-altitude newcomers, which may contribute to exercise capacity.

Physiology in Medicine: A physiologic approach to prevention and treatment of acute high-altitude illnesses

2015 ◽  
Vol 118 (5) ◽  
pp. 509-519 ◽  
Author(s):  
Andrew M. Luks
Keyword(s):  
High Altitude ◽  
Acute Hypoxia ◽  
Acute Mountain Sickness ◽  
Travel Medicine ◽  
Barometric Pressure ◽  
Time Frame ◽  
Low Oxygen ◽  
Organ Systems ◽  
Prevention And Treatment ◽  
Physiologic Responses

With the growing interest in adventure travel and the increasing ease and affordability of air, rail, and road-based transportation, increasing numbers of individuals are traveling to high altitude. The decline in barometric pressure and ambient oxygen tensions in this environment trigger a series of physiologic responses across organ systems and over a varying time frame that help the individual acclimatize to the low oxygen conditions but occasionally lead to maladaptive responses and one or several forms of acute altitude illness. The goal of this Physiology in Medicine article is to provide information that providers can use when counseling patients who present to primary care or travel medicine clinics seeking advice about how to prevent these problems. After discussing the primary physiologic responses to acute hypoxia from the organ to the molecular level in normal individuals, the review describes the main forms of acute altitude illness—acute mountain sickness, high-altitude cerebral edema, and high-altitude pulmonary edema—and the basic approaches to their prevention and treatment of these problems, with an emphasis throughout on the physiologic basis for the development of these illnesses and their management.

Adaptations to High-Altitude Hypoxia

2021 ◽  
Author(s):  
Cynthia M. Beall ◽  
Kingman P. Strohl
Keyword(s):  
High Altitude ◽  
Oxygen Delivery ◽  
Hemoglobin Concentration ◽  
Barometric Pressure ◽  
Ambient Air ◽  
Extreme Environment ◽  
Indigenous Populations ◽  
East African ◽  
Short Term

Biological anthropologists aim to explain the hows and whys of human biological variation using the concepts of evolution and adaptation. High-altitude environments provide informative natural laboratories with the unique stress of hypobaric hypoxia, which is less than usual oxygen in the ambient air arising from lower barometric pressure. Indigenous populations have adapted biologically to their extreme environment with acclimatization, developmental adaptation, and genetic adaptation. People have used the East African and Tibetan Plateaus above 3,000 m for at least 30,000 years and the Andean Plateau for at least 12,000 years. Ancient DNA shows evidence that the ancestors of modern highlanders have used all three high-altitude areas for at least 3,000 years. It is necessary to examine the differences in biological processes involved in oxygen exchange, transport, and use among these populations. Such an approach compares oxygen delivery traits reported for East African Amhara, Tibetans, and Andean highlanders with one another and with short-term visitors and long-term upward migrants in the early or later stages of acclimatization to hypoxia. Tibetan and Andean highlanders provide most of the data and differ quantitatively in biological characteristics. The best supported difference is the unelevated hemoglobin concentration of Tibetans and Amhara compared with Andean highlanders as well as short- and long-term upward migrants. Moreover, among Tibetans, several features of oxygen transfer and oxygen delivery resemble those of short-term acclimatization, while several features of Andean highlanders resemble the long-term responses. Genes and molecules of the oxygen homeostasis pathways contribute to some of the differences.

Effect of beta-adrenoceptor blockade on renin-aldosterone and alpha-ANF during exercise at altitude

1989 ◽  
Vol 67 (1) ◽  
pp. 141-146 ◽  
Author(s):  
P. Bouissou ◽  
J. P. Richalet ◽  
F. X. Galen ◽  
M. Lartigue ◽  
P. Larmignat ◽  
...  
Keyword(s):  
High Altitude ◽  
Sea Level ◽  
Acute Mountain Sickness ◽  
Plasma Renin ◽  
Barometric Pressure ◽  
Suppressive Effect ◽  
Beta Blockade ◽  
Plasma Norepinephrine ◽  
Plasma Aldosterone Concentration ◽  
Ergometer Exercise

The renin-aldosterone system may be depressed in subjects exercising at high altitude, thereby preventing excessive angiotensin I (ANG I) and aldosterone levels, which could favor the onset of acute mountain sickness. The role of beta-adrenoceptors in hormonal responses to hypoxia was investigated in 12 subjects treated with a nonselective beta-blocker, pindolol. The subjects performed a standardized maximal bicycle ergometer exercise with (P) and without (C) acute pindolol treatment (15 mg/day) at sea level, as well as during a 5-day period at high altitude (4,350 m, barometric pressure 450 mmHg). During sea-level exercise, pindolol caused a reduction in plasma renin activity (PRA, 2.83 +/- 0.35 vs. 5.13 +/- 0.7 ng ANG I.ml-1.h-1, P less than 0.01), an increase in plasma alpha-atrial natriuretic factor (alpha-ANF) level (23.1 +/- 2.9 (P) vs. 10.4 +/- 1.5 (C) pmol/1, P less than 0.01), and no change in plasma aldosterone concentration [0.50 +/- 0.04 (P) vs. 0.53 +/- 0.03 (C) nmol/1]. Compared with sea-level values, PRA (3.45 +/- 0.7 ng ANG I.ml-1.h-1) and PA (0.39 +/- 0.03 nmol/1) were significantly lower (P less than 0.05) during exercise at high altitude. alpha-ANF was not affected by hypoxia. When beta-blockade was achieved at high altitude, exercise-induced elevation in PRA was completely abolished, but no additional decline in PA occurred. Plasma norepinephrine and epinephrine concentrations tended to be lower during maximal exercise at altitude; however, these differences were not statistically significant. Our results provide further evidence that hypoxia has a suppressive effect on the renin-aldosterone system. However, beta-adrenergic mechanisms do not appear to be responsible for inhibition of renin secretion at high altitude.

A transportable hyperbaric chamber with soda lime for the treatment of high-altitude disorders

1994 ◽  
Vol 5 (3) ◽  
pp. 295-301 ◽  
Author(s):  
Shigeru Saito ◽  
Hitoshi Shimada ◽  
Kinichi Yamamori
Keyword(s):  
High Altitude ◽  
Soda Lime ◽  
Hyperbaric Chamber

Arrhythmic Risk Evaluation during Exercise at High Altitude in Healthy Subjects: Role of Microvolt T-Wave Alternans

2008 ◽  
Vol 31 (10) ◽  
pp. 1277-1283 ◽  
Author(s):  
GIUSEPPE GIBELLI ◽  
CECILIA FANTONI ◽  
CLAUDIO ANZÀ ◽  
PAOLO CATTANEO ◽  
ANDREA ROSSI ◽  
...  
Keyword(s):  
High Altitude ◽  
Healthy Subjects ◽  
Risk Evaluation ◽  
T Wave ◽  
T Wave Alternans

scholarly journals Respiratory and circulatory control at high altitudes.

1982 ◽  
Vol 100 (1) ◽  
pp. 147-157
Author(s):  
J B West
Keyword(s):  
Oxygen Consumption ◽  
High Altitude ◽  
Acute Hypoxia ◽  
Maximal Oxygen Consumption ◽  
Barometric Pressure ◽  
Mount Everest ◽  
Exercise Ventilation ◽  
Circulatory Control ◽  
Work Level ◽  
Oxygen Requirements

Hyperventilation is one of the most important features of acclimatization to high altitude. Resting ventilation at extreme altitudes increases up to fourfold and exercise ventilation for a given work level increases to the same extent. Hypoxic stimulation of the peripheral chemoreceptors is the chief mechanism for the hyperventilation but there is also evidence that central sensitization of the respiratory centres occurs. Permanent residents of high altitude have a blunted hypoxic ventilatory response compared to acclimatized lowlanders. Cardiac output increases in responses to acute hypoxia but returns to normal in acclimatized lowlanders. Oxygen uptake at extreme altitudes is markedly limited by the diffusion properties of the blood gas barrier. As a consequence the maximal oxygen consumption of a climber near the summit of Mount Everest is near his basal oxygen requirements. Maximal oxygen consumption is so sensitive to barometric pressure that it may be that day-to-day variations will affect the chances of a climber reaching the summit without supplementary oxygen.

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