Influence of Natural Hypobaric Hypoxic Conditions on Dynamic Visual Performance

Influence of short-term hypoxia exposure on dynamic visual acuity

Background

To quantify the changes in dynamic visual acuity (DVA) and explain the hidden reasons after acute exposure to hypobaric hypoxia status.

Methods

The study group comprised 18 healthy male and 15 healthy female participants aged 20-24 years old. DVA was measured with the self-developed software of Meidixin (Tianjin) Co., Ltd. Measurements were taken at eight altitudes. Data analysis was performed using the Kolmogorov-Smirnov test, paired sample T-test, and two-way repeated measures analysis of variance (ANOVA) for repeated measurements.

Results

At constant altitude, DVA showed an overall decreasing trend with increasing angular velocity and a fluctuating decrease at the vast majority of altitudes. At constant angular velocities, DVA gradually increased with altitude, with the most pronounced increase in DVA at altitude 5, and thereafter a gradual decrease in DVA as altitude increased. Finally, as altitude decreased, DVA increased again and reached a higher level at the end of the experiment, which was superior to the DVA in the initial state.

Conclusion

Under a hypobaric hypoxic environment at high altitude, DVA was affected by the angular velocity and the degree of hypoxia, manifesting as an increase or decrease in DVA, which affects the pilot's observation of the display and control interfaces during the driving process, acquisition of information, and decision-making ability, which in turn may potentially jeopardize the safety of the flight.

A longitudinal study on the impact of high-altitude hypoxia on perceptual processes

This study aimed to explore the neural mechanisms underlying high-altitude (HA) adaptation and deadaptation in perceptual processes in lowlanders. Eighteen healthy lowlanders were administered a facial S1-S2 matching task that included incomplete face (S1) and complete face (S2) photographs combined with ERP technology. Participants were tested at four time points: shortly before they departed the HA (Test 1), twenty-five days after entering the HA (Test 2), and one week (Test 3) and one month (Test 4) after returning to the lowlands. Compared with those at sea level (SL), shorter reaction times (RTs), shorter latencies of P1 and N170, and larger amplitudes of complete face N170 were found in HAs. After returning to SL, compared with that of HA, the amplitude of the incomplete face P1 was smaller after one week, and the complete face was smaller after one month. The right hemisphere N170 amplitude was greater after entering HA and one week after returning to SL than at baseline, but it returned to baseline after one month. Taken together, the current findings suggest that HA adaptation increases visual cortex excitation to accelerate perceptual processing. More mental resources are recruited during the configural encoding stage of complete faces after HA exposure. The perceptual processes affected by HA exposure are reversible after returning to SL, but the low-level processing stage differs between incomplete and complete faces due to neural compensation mechanisms. The configural encoding stage in the right hemisphere is affected by HA exposure and requires more than one week but less than one month to recover to baseline.

Influence of hypobaric hypoxic conditions on ocular structure and biological function at high attitudes: a narrative review

Background

With the development of science and technology, high-altitude environments, involving aviation, aerospace, and mountainous regions, have become the main areas for human exploration, while such complex environments can lead to rapid decreases in air and oxygen pressure. Although modern aircrafts have pressurized cabins and support equipment that allow passengers and crew to breathe normally, flight crew still face repeated exposure to hypobaric and hypoxic conditions. The eye is a sensory organ of the visual system that responds to light and oxygen plays a key role in the maintenance of normal visual function. Acute hypoxia changes ocular structure and function, such as the blood flow rate, and can cause retinal ischemia.

Methods

We reviewed researches, and summarized them briefly in a review.

Results

The acute hypobaric hypoxia affects corneal, anterior chamber angle and depth, pupils, crystal lens, vitreous body, and retina in structure; moreover, the acute hypoxia does obvious effect on visual function; for example, vision, intraocular pressure, oculometric features and dynamic visual performance, visual field, contrast sensitivity, and color perception.

Conclusion

We summarized the changes in the physiological structure and function of the eye in hypoxic conditions and to provide a biological basis for the response of the human eye at high-altitude.

MUSCLE STRENGTH COORDINATION TRAINING FOR ATHLETES IN MOUNTAINEERING SPORTS

ABSTRACT Introduction Rock climbing is a physical activity that requires excellent physical conditioning. In addition to improving physical fitness and motor coordination, rock climbing requires constant improvements in muscle coordination skill training to enhance its modern tactics. Objective Explore the muscular coordination skill training of rock climbers. Methods A random sample of 8 athletes were assigned to the experiment involving the measurement of athletes’ body composition, serum creatine kinase and blood urea levels, and other biomarkers collected before and after the trial. Results There was a significant negative correlation between dynamic balance and motor coordination ability after training in extreme rock climbing sports. On the second day after the rock climbing exercise, the volunteers’ body weight and fat content significantly reduced, and the concentration of creatine kinase (CK) and blood urea (BU) increased significantly. Conclusion The exploration of extreme sports’ effect on improving athletes’ muscle coordination ability showed that strength and coordination should be enhanced in rock climbing. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

Adaptation and altitude sickness: A 40-year bibliometric analysis and collaborative networks

Introduction

We analyze the scientific production and collaboration networks of studies based on adaptation and altitude diseases in the period 1980-2020.

Methods

The publications were extracted from journals indexed in Scopus. The bibliometric analysis was used to analyze the scientific production, including the number of annual publications, the documents, and the characteristics of the publications. With the VOSviewer software, the analysis of collaborative networks, productivity of the countries, as well as the analysis of the co-occurrence of keywords were visualized.

Results

15,240 documents were registered, of which 3,985 documents were analyzed. A significant trend was observed in the number of publications (R ²: 0.9847; P: < 0.001), with annual growth of 4.6%. The largest number of publications were original articles (77.8%), these published more frequently in the journal "Altitude Medicine and Biology". The largest number of countries were from Europe and Asia; however, the largest collaboration network was with the United States. Of the countries with high altitudes, China and Peru ranked first in scientific productivity. The research priorities were on the adaptation mechanism (37.1%), mainly anoxia and respiratory function. Acute mountain sickness (18.4%) and pulmonary edema (14.7%) were the most reported diseases. Of the top 10 institutions, "University of Colorado" and "Universidad Peruana Cayetano Heredia" contributed more than 100 publications.

Conclusions

Scientific production on adaptation and altitude illnesses continues to grow. The United States and United Kingdom present collaborative networks with high-altitude countries. The research is aimed at studying the mechanisms of adaptation to altitude and acute mountain sickness.

Dynamic Range of Luminance Perception in Acute Hypobaric Hypoxia

Rizzi, Alessandro, Alice Plutino, Diego Vecchi, Anton Giulio Guadagno, and Marco Lucertini. Dynamic range of luminance perception in acute hypobaric hypoxia. High Alt Med Biol. 23:313-318, 2022.-The effects of acute hypobaric hypoxia, as potentially experienced in high altitude flight, on the detection of low contrast targets within a high dynamic range (DR) of luminance were investigated. The tests were performed after 10 minutes of adaptation to an ambient luminance level of 0.2 lx. Twenty-four individuals were exposed to hypobaric hypoxia at an altitude of 18,000 ft (5,490 m) inside a hypobaric chamber and were asked to identify the darkest one perceived from a grid of progressively less luminous patches. The results were compared with those obtained by the same subjects at sea level. The results indicate a global reduction of the DR perception during hypoxia, with a mean decrease of 0.023 cd/m² (standard deviation ±0.064), which resulted statistically significant (p < 0.05). No significant correlations with oxygen saturation levels were observed. These findings might have practical applications in the design of cockpit's instruments, especially those dedicated to night-time flight missions at high altitudes.