The Small Pulmonary Arteries in Rats at Simulated High Altitude

Pathobiology ◽  
1973 ◽  
Vol 39 (3-4) ◽  
pp. 270-275 ◽  
Author(s):  
J.M. Kay ◽  
P. Smith
Keyword(s):  
High Altitude ◽  
Pulmonary Arteries ◽  
Simulated High Altitude

Reduction of ICa,Land Ito1Density in Hypertrophied Right Ventricular Cells by Simulated High Altitude in Adult Rats

1997 ◽  
Vol 29 (1) ◽  
pp. 193-206 ◽  
Author(s):  
Christophe Chouabe ◽  
Leon Espinosa ◽  
Pierre Megas ◽  
Abderrazak Chakir ◽  
Oger Rougier ◽  
...  
Keyword(s):  
Right Ventricular ◽  
High Altitude ◽  
Adult Rats ◽  
Ventricular Cells ◽  
Simulated High Altitude

Role of Rho kinases in PKG-mediated relaxation of pulmonary arteries of fetal lambs exposed to chronic high altitude hypoxia

2007 ◽  
Vol 292 (3) ◽  
pp. L678-L684 ◽  
Author(s):  
Yuansheng Gao ◽  
Ada D. Portugal ◽  
Sewite Negash ◽  
Weilin Zhou ◽  
Lawrence D. Longo ◽  
...  
Keyword(s):  
High Altitude ◽  
Chronic Hypoxia ◽  
Pulmonary Arteries ◽  
Regulatory Subunit ◽  
Fourth Generation ◽  
Minor Effect ◽  
Altitude Hypoxia ◽  
High Altitude Hypoxia ◽  
Rock Activity

An increase in Rho kinase (ROCK) activity is implicated in chronic hypoxia-induced pulmonary hypertension. In the present study, we determined the role of ROCKs in cGMP-dependent protein kinase (PKG)-mediated pulmonary vasodilation of fetal lambs exposed to chronic hypoxia. Fourth generation pulmonary arteries were isolated from near-term fetuses (∼140 days of gestation) delivered from ewes exposed to chronic high altitude hypoxia for ∼110 days and from control ewes. In vessels constricted to endothelin-1, 8-bromoguanosine-cGMP (8-Br-cGMP) caused a smaller relaxation in chronically hypoxic (CH) vessels compared with controls. Rp-8-Br-PET-cGMPS, a PKG inhibitor, attenuated relaxation to 8-Br-cGMP in control vessels to a greater extent than in CH vessels. Y-27632, a ROCK inhibitor, significantly potentiated 8-Br-cGMP-induced relaxation of CH vessels and had only a minor effect in control vessels. The expression of PKG was increased but was not accompanied with an increase in the activity of the enzyme in CH vessels. The expression of type II ROCK and activity of ROCKs were increased in CH vessels. The phosphorylation of threonine (Thr)696 and Thr850 of the regulatory subunit MYPT1 of myosin light chain phosphatase was inhibited by 8-Br-cGMP to a lesser extent in CH vessels than in controls. The difference was eliminated by Y-27632. These results suggest that chronic hypoxia in utero attenuates PKG-mediated relaxation in pulmonary arteries, partly due to inhibition of PKG activity and partly due to enhanced ROCK activity. Increased ROCK activity may inhibit PKG action through increased phosphorylation of MYPT1 at Thr696 and Thr850.

Relationship between Behavior in a Stress Situation and Later Separation from Flight Training with Expressed Anxiety toward Flying

1956 ◽  
Vol 2 (3) ◽  
pp. 393-397
Author(s):  
Robert B. Voas ◽  
John T. Bair ◽  
Rosalie K. Ambler
Keyword(s):  
High Altitude ◽  
Training Program ◽  
Flight Training ◽  
Stress Situation ◽  
Simulated High Altitude ◽  
Development Of Anxiety ◽  
The Relationship

The purpose of this research was to determine the relationship between reactions of cadets during simulated high altitude in a decompression chamber and the later development of anxiety toward flying as reported in terminal interviews. The results for 1540 cadets indicated that significantly more of those who withdrew because of anxiety toward flying had anxiety reactions in the decompression chamber than of those who completed the Naval Air Training Program.

Acute hypoxia in a simulated high-altitude airdrop scenario due to oxygen system failure

2017 ◽  
Vol 123 (6) ◽  
pp. 1443-1450 ◽  
Author(s):  
William Ottestad ◽  
Tor Are Hansen ◽  
Gaurav Pradhan ◽  
Jan Stepanek ◽  
Lars Øivind Høiseth ◽  
...  
Keyword(s):  
High Altitude ◽  
Acute Hypoxia ◽  
Supplemental Oxygen ◽  
Cerebral Oximetry ◽  
Arterial Oxygen ◽  
Hypoxic Exposure ◽  
System Failure ◽  
Oxygen System ◽  
Simulated High Altitude ◽  
Oxygen Tensions

High-Altitude High Opening (HAHO) is a military operational procedure in which parachute jumps are performed at high altitude requiring supplemental oxygen, putting personnel at risk of acute hypoxia in the event of oxygen equipment failure. This study was initiated by the Norwegian Army to evaluate potential outcomes during failure of oxygen supply, and to explore physiology during acute severe hypobaric hypoxia. A simulated HAHO without supplemental oxygen was carried out in a hypobaric chamber with decompression to 30,000 ft (9,144 m) and then recompression to ground level with a descent rate of 1,000 ft/min (305 m/min). Nine subjects were studied. Repeated arterial blood gas samples were drawn throughout the entire hypoxic exposure. Additionally, pulse oximetry, cerebral oximetry, and hemodynamic variables were monitored. Desaturation evolved rapidly and the arterial oxygen tensions are among the lowest ever reported in volunteers during acute hypoxia. PaO2 decreased from baseline 18.4 (17.3–19.1) kPa, 138.0 (133.5–143.3) mmHg, to a minimum value of 3.3 (2.9–3.7) kPa, 24.8 (21.6–27.8) mmHg, after 180 (60–210) s, [median (range)], N = 9. Hyperventilation with ensuing hypocapnia was associated with both increased arterial oxygen saturation and cerebral oximetry values, and potentially improved tolerance to severe hypoxia. One subject had a sharp drop in heart rate and cardiac index and lost consciousness 4 min into the hypoxic exposure. A simulated high-altitude airdrop scenario without supplemental oxygen results in extreme hypoxemia and may result in loss of consciousness in some individuals. NEW & NOTEWORTHY This is the first study to investigate physiology and clinical outcome of oxygen system failure in a simulated HAHO scenario. The acquired knowledge is of great value to make valid risk-benefit analyses during HAHO training or operations. The arterial oxygen tensions reported in this hypobaric chamber study are among the lowest ever reported during acute hypoxia.

Effects of simulated high altitude on blood glucose levels during exercise in individuals with Type 1 Diabetes

2021 ◽  
Author(s):  
Cory W Dugan ◽  
Shane K Maloney ◽  
Kristina J Abramoff ◽  
Sohan S Panag ◽  
Elizabeth A Davis ◽  
...  
Keyword(s):  
High Altitude ◽  
Acute Hypoxia ◽  
Carbohydrate Oxidation ◽  
Normoxic Condition ◽  
Glucose Levels ◽  
Oxidation Rates ◽  
Blood Glucose Levels ◽  
Simulated High Altitude ◽  
The Impact

Abstract Context Current exercise guidelines for individuals with type 1 diabetes (T1D) do not consider the impact that high altitude may have on blood glucose levels (BGL) during exercise. Objective To investigate the effect of acute hypoxia (simulated high altitude) on BGL and carbohydrate oxidation rates during moderate intensity exercise in individuals with T1D. Methods Using a counterbalanced, repeated measures study design, 7 individuals with T1D completed two exercise sessions; normoxia and hypoxia (~4,200m simulated altitude). Participants cycled for 60min on an ergometer at 45% of their sea-level V̇O2peak, and then recovered for 60min. Before, during and after exercise, blood samples were taken to measure glucose, lactate and insulin levels. Respiratory gases were collected to measure carbohydrate oxidation rates. Results Early during exercise (<30min), there was no fall in BGL in either condition. After one hour of exercise and during recovery, BGL were significantly lower under the hypoxic condition compared to both pre-exercise levels (p=0.008) and the normoxic condition (p=0.027). Exercise in both conditions resulted in a significant rise in carbohydrate oxidation rates, which returned to baseline levels post-exercise. Before, during and after exercise, carbohydrate oxidation rates were higher under the hypoxic compared with the normoxic condition (p<0.001). Conclusions The greater decline in BGL during and after exercise performed under acute hypoxia suggests that exercise during acute exposure to high altitude may increase the risk of hypoglycemia in individuals with T1D. Future guidelines may have to consider the impact altitude has on exercise-mediated hypoglycemia.

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