Acclimatization
Andrew M. Luks, Philip N. Ainslie, Justin S. Lawley, Robert C. Roach, Tatum S. Simonson in Ward, Milledge and West's High Altitude Medicine and Physiology, 2021
Although medications are often used to facilitate acclimatization and decrease the risk of acute altitude illness (Chapters 20 and 22), they cannot provide the same protection against AMS, HACE, or HAPE or improve cognitive and physical performance to the same extent as allowing adequate time for acclimatization and the protective physiological responses. There has been increasing interest among mountaineers and other high altitude travelers in strategies that can be employed ahead of the planned high altitude excursion to accelerate the process of acclimatization. While the most reliable method would be to live 24 hours a day for several weeks in a hypobaric chamber (Houston and Riley 1947; Houston et al. 1987; Richalet 2010), such a strategy is infeasible for the overwhelming majority of people traveling to high altitude, and other less time-intensive strategies are necessary.
Oxygen
Donald A. Mahler, Denis E. O’Donnell in Dyspnea, 2014
POCs are lightweight units that provide either pulse flow or a combination of pulse and oxygen flow, and can be operated on external current or battery power with no time limitation. Although the versatility of these units has essentially eliminated patient dependence on oxygen delivery companies or stationary home units, concern about potential undertreatment of hypoxemia in some patients has been raised [97,98] because of the less than pure oxygen provided, unlike with gas cylinders, and because of increased entrainment of room air and drop in oxygen concentration with increased respiratory rate [94,99]. Data on the effectiveness of POCs are limited, but POCs have been shown to be equivalent to portable liquid oxygen systems and compressed gas canisters in treating exertional hypoxemia in COPD patients [97,100]. However, POCs may not be equivalent to other delivery methods in all cases. In a study of 16 patients with severe COPD being evaluated for air travel by hypoxia altitude simulation test and hypobaric chamber, oxygen delivery by POC resulted in a significantly lower PaO2 than that achieved with compressed oxygen, either by continuous flow or with an oxygen-conserving device [101]. Although these findings do not preclude the use of POCs for air travel, they underline the need for device-specific titration and anticipation of additional oxygen flow requirements.
Lower-intensity aerobic endurance sports
Nick Draper, Helen Marshall in Exercise Physiology, 2014
The equivocal results achieved with pure altitude training have led researchers to investigate the benefits of live high-train low (hi-lo) strategies. In this type of training athletes spend most of their time living at altitude to stimulate the physiological benefits associated with prolonged altitude exposure, but return to sea level for training, thereby maintaining the intensity of training. Within the literature participants have either lived at altitude for acclimatisation or alternatively resided within a de-pressurised house, while some have slept in a hypobaric chamber or tent. These simulated altitude alternatives provide an opportunity for an athlete to experience the benefits of living at altitude without having to move away from their normal training environment. A research paper by Levine and Stray-Gundersen on the effects of HiLo training has been summarised to provide an insight into the performance benefits of such training (seepp. 385–6).
Central Corneal Thickness of Healthy Lowlanders at High Altitude: A Systematic Review and Meta-Analysis
Published in Current Eye Research, 2018
Hsin-Ming Liu, Chyi-Huey Bai, Cher-Ming Liou, Hung-Yi Chiou, Chiehfeng Chen
Our study has several limitations. First, trials conducted at both altitude and simulated altitude were included. Although hypobaric chambers might not necessarily reflect geographical conditions on a mountain, the test for subgroup differences between hypobaric chambers and real altitude in our study showed no statistical significance. Second, 100% oxygen masks were provided to participants of the two trials conducted in the hypobaric chamber. The reason for not giving the same oxygen level at high elevations was because of the chamber safety rules for avoiding decompression sickness, and as the mask covered only the nose and mouth, oxygen was not directly administered to the cornea. Third, CCT changes due to high-elevation exposure were not continuously investigated, and this was mainly because only a minority of included trials reported serial CCT measurements. Thus, further studies with daily measurements of CCT at high altitude and a close follow-up of CCT after descent to lower elevations are required to achieve a comprehensive understanding of cornea edema formation and recovery.
Compound Danshen Dripping Pill inhibits high altitude-induced hypoxic damage by suppressing oxidative stress and inflammatory responses
Published in Pharmaceutical Biology, 2021
Yunhui Hu, Jia Sun, Tongxing Wang, Hairong Wang, Chunlai Zhao, Wenjia Wang, Kaijing Yan, Xijun Yan, He Sun
Male Sprague-Dawley rats were obtained from SBF Biotechnology (Beijing, China). Rats were distributed randomly in 5 groups (6 rats per group) and received treatment by intragastric administration at 10 mL/kg once a day for 3 d. Treatments consist of 0.5% sodium carboxymethylcellulose (CMC), CDDP (at 170 and 340 mg/kg, in 0.5% CMC) and 50 mg/kg ACTZ in 0.5% CMC. Rats in the control group (0.5% CMC) were left at atmospheric pressure, whereas animals in all other treatments, including a model group treated with only 0.5% CMC, were introduced in a hypobaric chamber (QTK-LP; IVD Biotechnology, Henan, China) for 24 h in order to simulate an altitude of 5500 m.
Comparative study of the effect of bilastine and cetirizine on cognitive functions at ground level and at an altitude of 4,000 m simulated in hypobaric chamber: a randomized, double-blind, placebo-controlled, cross-over study
Published in Expert Opinion on Drug Safety, 2018
Ákos Reményi, Andor Grósz, Sándor András Szabó, Zsolt Tótka, Dávid Molnár, Frigyes Helfferich
In our study, due to the points above, we were not satisfied with low altitude testing and with the sole application of the hypoxia condition. The hypobaric chamber was, therefore, an indispensable means of testing, without endangering the health of the volunteers, but with the testing criteria satisfied with 4,000 m maximum simulated altitude.
Related Knowledge Centers
- Decompression Sickness
- Unconsciousness
- Valsalva Maneuver
- Hypoxia
- Nitrogen
- Oxygen Saturation
- Aerospace Physiology
- Oxygen Mask
- Time of Useful Consciousness