Influence of hematocrit ratio on survival of unacclimatized dogs at simulated high altitude

Eighty-six dogs were subjected to acutely induced, simulated high altitudes to determine the optimum hematocrit ratio for survival. High altitudes were simulated by diluting atmospheric air with nitrogen. Dogs with various hematocrit ratios were obtained by natural selection, hemorrhage, transfusion, and pretreatment with phenylhydrazine. Fifty-one dogs, in groups of 5–15, were placed in a closed chamber, and a 40,000-ft altitude was simulated by proper adjustment of the oxygen-to-nitrogen ratio. This altitude was maintained for a period of 6 hr. Most dogs with hematocrits less than 24 or greater than 66 died before the simulated altitude of 40,000 ft was attained; those with hematocrits of 24–30 survived from 1/2 to 5 hr. Some dogs with hematocrits of 30–65 survived the entire 7-hr period. However, no dogs with hematocrits from 37 to 54 died. The same procedures were repeated at a simulated altitude of 50,000 ft with a group of 38 dogs. The survival group was composed of dogs with hematocrits of 36–46. Dogs with hematocrits of 40–41 were conscious and active while those with hematocrits on either side of this value were comatose. These data indicate that the optimum hematocrit for survival of the unacclimatized dog at acutely induced high altitude is about 40. Deaths occurring on both sides of the optimum value may be explained by a simultaneous consideration of the curves depicting oxygen-carrying capacity of the blood, and blood viscosity, at all ranges of hematocrit.

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Blood respiratory properties in pigeons at high altitudes: effects of acclimation

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1985.249.6.r765 ◽

1985 ◽

Vol 249 (6) ◽

pp. R765-R775 ◽

Cited By ~ 2

Author(s):

Y. Weinstein ◽

M. H. Bernstein ◽

P. E. Bickler ◽

D. V. Gonzales ◽

F. C. Samaniego ◽

...

Keyword(s):

High Altitude ◽

Venous Blood ◽

Hypoxia Tolerance ◽

Control Group ◽

Mixed Venous Blood ◽

High Altitudes ◽

Simulated High Altitude ◽

O2 Extraction ◽

Columbia Livia ◽

Venous Blood Gas

Many birds thrive at high altitudes where environmental temperatures are low. Previous studies have shown that tolerance of and acclimation to hypoxia involve cardiopulmonary and hematological adaptations. We investigated blood respiratory properties during exposure to simulated high altitude (hypobaric hypoxia) and low temperature in unanesthetized resting pigeons (Columbia livia, mean mass 0.38 kg). A control group (C) and a group acclimated to 7 km above sea level (ASL) in a hypobaric chamber at 25 degrees C (HA group) were used. All were acutely exposed to altitudes through 9 km ASL at 5 or 25 degrees C. Arterial and mixed venous blood gas tensions and O2 and CO2 content during steady state decreased with increased altitude, whereas blood lactate increased in both groups at both temperatures. Acute high-altitude exposure did not affect hematocrit, hemoglobin concentrations, or O2 carrying capacity, but at any altitude these were all greater in HA than in C birds. At 5 degrees C blood pH increased with altitude in controls but remained unchanged in HA birds. At 25 degrees C in both groups mean intracellular pH did not change, averaging 6.97, whereas extracellular (venous) pH increased with altitude. At the highest altitudes tissue O2 extraction was virtually complete in both groups. Acclimation changed blood O2 and CO2 combining properties in ways likely to improve gas transport at high altitudes. The previously unreported shifts in blood respiratory and acid-base properties with acclimation indicate that innate extrapulmonary adaptations contribute to avian hypoxia tolerance.

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Respiratory alkalosis and hypokalemia in dogs exposed to simulated high altitude

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1962.202.6.1041 ◽

1962 ◽

Vol 202 (6) ◽

pp. 1041-1044 ◽

Cited By ~ 4

Author(s):

D. C. Smith ◽

J. Q. Barry ◽

A. J. Gold

Keyword(s):

High Altitude ◽

Potassium Concentration ◽

Plasma Potassium ◽

Respiratory Alkalosis ◽

Simulated Altitude ◽

Simulated High Altitude ◽

Anesthetized Dogs ◽

Per Se ◽

Decompression Stress

Exposure of restrained, unanesthetized dogs to a simulated altitude of 30,000 ft consistently resulted in respiratory alkalosis and marked hypokalemia. When alkalosis was prevented by increasing the pCO2 of inspired air during decompression, a smaller but statistically significant decrease in plasma potassium concentration still occurred. In comparison with previous studies, the hypokalemia observed in these restrained, unanesthetized dogs was greater than that found in either unrestrained or anesthetized dogs subjected to the same decompression stress. Consequently, the suggestion is made that in the unanesthetized, restrained dog, the hypokalemic response not attributable to respiratory alkalosis is of adrenal mediation and results from the "stress" of restraint plus hyperventilation, rather than to hypoxemia or the decompression stress, per se.

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Relationship Between Arterial Oxygen Saturation and Hematocrit, and Effect of Slow Deep Breathing on Oxygen Saturation in Himalayan High Altitude Populations

Kathmandu University Medical Journal ◽

10.3126/kumj.v10i3.8014 ◽

2013 ◽

Vol 10 (3) ◽

pp. 30-34 ◽

Cited By ~ 1

Author(s):

Ojashwi Nepal ◽

BR Pokharel ◽

K Khanal ◽

SL Mallik ◽

BK Kapoor ◽

...

Keyword(s):

Oxygen Saturation ◽

High Altitude ◽

Carrying Capacity ◽

Arterial Oxygen Saturation ◽

Arterial Oxygen ◽

P Value ◽

Deep Breathing ◽

Cross Sectional ◽

Lower Altitude ◽

Oxygen Carrying Capacity

Background The oxygen saturation of haemoglobin is reduced in high altitude-living organisms. Increase in the hematocrit is responsible for rise in the hemoglobin concentration so that the oxygen carrying capacity in the hypobaric hypoxic subject is elevated. Objectives To compare two different high altitude populations, in order to study the relationship between arterial oxygen saturation and hematocrit. Methods lIn the cross-sectional study of two populations residing at altitude of 2800 m and 3760 m are compared for the difference in hematocrit. The oxygen carrying capacity of arterial haemoglobin (SaO2) is determined by pulse oximetry. The sample is drawn from the natives of two small villages, Thini at Jomsom (2800 m) and Jharkot (3760 m) in Mustang district of Nepal. The natives at 2800 m are termed as lower high altitude population and local residents at 3760 m are said to be higher altitude population in this study. The sample blood was drawn by venipuncture and packed cell volume was determined by Wintrobe’s method. Results The hematocrit obtained from 3760 m altitude population and the lower high altitude population at altitude of 2800 m differ significantly with the p value < 0.0001and the SaO2 in both the population fails to show any difference with p value > 0.05. Deep breathing exercise in these populations however increased SaO2 significantly. Conclusion The higher altitude natives have greater arterial oxygen saturation than lower altitude population which is due to rise in red cell concentration. The slow deep breathing raises oxygen saturation irrespective of altitude. Kathmandu University Medical Journal | VOL.10 | NO. 3 | ISSUE 39 | JUL- SEP 2012 | Page 30-34 DOI: http://dx.doi.org/10.3126/kumj.v10i3.8014

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The effect of Aeration of the Oil on the Behaviour of an Engine Lubricating System Under High Altitude Conditions

Journal of the Royal Aeronautical Society ◽

10.1017/s0368393100115640 ◽

1949 ◽

Vol 53 (460) ◽

pp. 383-404

Author(s):

E. Giffen ◽

H. R. Mills

Keyword(s):

High Altitude ◽

Atmospheric Pressure ◽

Aircraft Engine ◽

Lubricating Oil ◽

Lubrication System ◽

Simulated Altitude ◽

High Altitudes ◽

Fundamental Information ◽

Oil Mixtures

The work described in this paper was done during the war, at the suggestion of the aircraft engine firms, as a result of difficulties with lubricating oil systems at high altitudes. Failure of oil pressure, seizure of bearings, or excessive loss of oil sometimes occurred and these defects were attributed to air in the lubricating oil, this air being greatly increased in volume at high altitudes because of reduced atmospheric pressure.The behaviour of air-oil mixtures therefore was studied to obtain fundamental information which could be applied to engine lubrication at high altitudes. The present paper deals with that part of the research which was done on a complete lubrication system under simulated altitude conditions.

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Splenic contraction is enhanced by exercise at simulated high altitude

European Journal of Applied Physiology ◽

10.1007/s00421-021-04637-0 ◽

2021 ◽

Author(s):

Angelica Lodin-Sundström ◽

Pontus Holmström ◽

Marcus Ekstam ◽

Daniel Söderberg ◽

Erika Schagatay

Keyword(s):

High Altitude ◽

Spleen Volume ◽

Short Term ◽

Graded Response ◽

Simulated High Altitude ◽

Oxygen Carrying Capacity ◽

Partial Contraction ◽

Hypoxic Exercise ◽

Term Field

Abstract Purpose Splenic contraction increases circulating hemoglobin (Hb) with advantages during hypoxia. As both hypoxia and exercise have been shown to be important separate triggers of splenic contraction we aimed to investigate if the spleen response to simulated high altitude (HA) is enhanced by superimposing exercise. Method Fourteen healthy volunteers (seven females) performed the following protocol in a normobaric environment sitting on an ergometer cycle: 20 min rest in normoxia; 20 min rest while breathing hypoxic gas simulating an altitude of 3500 m; 10 min exercise at an individually set intensity while breathing the hypoxic gas; 20 min rest in hypoxia; and finally 20 min rest in normoxia. Spleen measurements were collected by ultrasonic imaging and venous Hb measured at the end of each intervention. Result Mean ± SD baseline spleen volume during normoxic rest was 280 ± 107 mL, the volume was reduced by 22% during rest in hypoxia to 217 ± 92 mL (p < 0.001) and by 33% during exercise in hypoxia (189 mL; p < 0.001). Hb was 140.7 ± 7.0 g/L during normoxic rest and 141.3 ± 7.4 g/L during hypoxic rest (NS), but increased by 5.3% during hypoxic exercise (148.6 ± 6.3 g/L; p < 0.001). Spleen volume and Hb were stepwise changed back to baseline at cessation of exercise and return to normoxia. Conclusion Splenic contraction is induced by hypoxia and further enhanced by superimposing exercise, and reduced when exercise ceases, in a step-wise manner, showing that the tonic but partial contraction observed in long-term field expeditions to HA may occur also in the short term. This “graded response” may be beneficial during acclimatization to HA, to cope with moderate chronic hypoxia during rest while allowing additional enhancement of oxygen carrying capacity to overcome short bouts of extreme hypoxia caused by exercise.

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The waterscape at high altitudes

10.1093/oso/9780198736868.003.0002 ◽

2017 ◽

Author(s):

Dean Jacobsen ◽

Olivier Dangles

Keyword(s):

High Altitude ◽

Regional Climate ◽

Water Source ◽

Aquatic Systems ◽

Running Waters ◽

High Altitudes ◽

Different Types ◽

Geological Origin ◽

Broad Variety ◽

The Tropics

Chapter 2 presents the amazing variety of running waters, lakes, ponds, and wetlands found at high altitudes. These waterbodies are not equally distributed among the world’s high altitude places, but tend to be concentrated in certain areas, primarily determined by regional climate and topography. Thus, a large proportion of the world’s truly high altitude aquatic systems are found at lower latitudes, mostly in the tropics. The chapter presents general patterns in the geographical distribution of high altitude waters, and gives examples of some of the most extreme systems. High altitude aquatic systems and habitats cover a broad variety in dynamics and physical appearance. These differences may be related to, for example, water source (glacier-fed, rain-fed, or groundwater-fed streams), geological origin (e.g. glacial, volcanic, or tectonic lakes), or catchment slope and altitude (different types of peatland wetlands). This is exemplified and richly illustrated through numerous photos.

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