Effects of high altitude on sleep and respiratory system and theirs adaptations

Key Genes FECH and ALAS2 under Acute High-Altitude Exposure: A Gene Expression and Network Analysis Based on Expression Profile Data

High-altitude acclimatization refers to the physiological adjustments and adaptation processes by which the human body gradually adapts to the hypoxic conditions of high altitudes after entering such environments. This study analyzed three mRNA expression profile datasets from the GEO database, focusing on 93 healthy residents from low altitudes (≤1400 m). Peripheral blood samples were collected for analysis on the third day after these individuals rapidly ascended to higher altitudes (3000-5300 m). The analysis identified significant differential expression in 382 genes, with 361 genes upregulated and 21 downregulated. Further, gene ontology (GO) annotation analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated that the top-ranked enriched pathways are upregulated, involving blood gas transport, erythrocyte development and differentiation, and heme biosynthetic process. Network analysis highlighted ten key genes, namely, SLC4A1, FECH, EPB42, SNCA, GATA1, KLF1, GYPB, ALAS2, DMTN, and GYPA. Analysis revealed that two of these key genes, FECH and ALAS2, play a critical role in the heme biosynthetic process, which is pivotal in the development and maturation of red blood cells. These findings provide new insights into the key gene mechanisms of high-altitude acclimatization and identify potential biomarkers and targets for personalized acclimatization strategies.

Altitude-Related Illness

Altitude-related illness occurs as a result of inadequate acclimatization. The mainstay of prevention is a slow, graded ascent profile which gives the body time to respond to a low-oxygen environment. The diagnosis of these conditions is often difficult in resource-limited environments, so history and a physical exam are key in identifying patients who will require descent and evacuation. Treatment modalities such as supplemental oxygen, portable hyperbaric chambers, and medications, are all temporizing measures until the patient can be safely evacuated to a lower elevation.

[Effects of Extreme Environments on Human Sleep]

Recently, with the rapid growth of the global population and the exhaustion of resources, exploration activities in extreme environments such as the polar regions, the outer space, the deep sea, the deep underground and highlands are becoming increasingly more frequent. This in-depth exploration of the external environment and the consequent dramatic changes in lifestyles impact on sleep, a basic life activity of humans, in ways that cannot be overlooked. the basic life activity of human beings. Sleep, a basic life activity and the result of the evolution of organisms to adapt to their environment, is closely associated with sleep homeostasis and endogenous rhythms. However, external environmental changes and lifestyle shifts in extreme environments have had a significant impact on the patterns and the quality of sleep in humans. Furthermore, this impact can lead to many physiological and psychological problems, posing a great threat to human health. In this review, we delved into the specific effects of different extreme natural environments and enclosed environments on sleep, elaborating on how these environments alter the patterns and the quality of sleep in humans. In addition, we summarized the changes in human sleep under extreme environments to help gain a better understanding of the mechanisms by which these specific environments impact human sleep. It is expected that this review will provide a solid theoretical foundation for optimizing long-term survival strategies in extreme environments and help humans adapt to and overcome the challenges posed by extreme environments more effectively.

Review of Athletic Guidelines for High-Altitude Training and Acclimatization

Ramchandani, Rashi, Ioana Tereza Florica, Zier Zhou, Aziz Alemi, and Adrian Baranchuk. Review of athletic guidelines for high-altitude training and acclimatization. High Alt Med Biol. 00:000-000, 2024. Introduction: Exposure to high altitude results in hypobaric hypoxia with physiological acclimatization changes that are thought to influence athletic performance. This review summarizes existing literature regarding implications of high-altitude training and altitude-related guidelines from major governing bodies of sports. Methods: A nonsystematic review was performed using PubMed and OVID Medline to identify articles regarding altitude training and guidelines from international governing bodies of various sports. Sports inherently involving training or competing at high altitude were excluded. Results: Important physiological compensatory mechanisms to high-altitude environments include elevations in blood pressure, heart rate, red blood cell mass, tidal volume, and respiratory rate. These responses can have varying effects on athletic performance. Governing sport bodies have limited and differing regulations for training and competition at high altitudes with recommended acclimatization periods ranging from 3 days to 3 weeks. Discussion: Physiological changes in response to high terrestrial altitude exposure can have substantial impacts on athletic performance. Major sport governing bodies have limited regulations and recommendations regarding altitude training and competition. Existing guidelines are variable and lack substantial evidence to support recommendations. Additional studies are needed to clarify the implications of high-altitude exposure on athletic ability to optimize training and competition.

Loop gain response to increased cerebral blood flow at high altitude

PURPOSE

To compare loop gain (LG) before and during pharmacological increases in cerebral blood flow (CBF) at high altitude (HA). Loop gain (LG) describes stability of a negative-feedback control system; defining the magnitude of response to a disturbance, such as hyperpnea to an apnea in periodic breathing (PB). "Controller-gain" sensitivity from afferent peripheral (PCR) and central-chemoreceptors (CCR) plays a key role in perpetuating PB. Changes in CBF may have a critical role via effects on central chemo-sensitivity during sleep.

METHODS

Polysomnography (PSG) was performed on volunteers after administration of I.V. Acetazolamide (ACZ-10mg/kg) + Dobutamine (DOB-2-5 μg/kg/min) to increase CBF (via Duplex-ultrasound). Central sleep apnea (CSA) was measured from NREM sleep. The duty ratio (DR) was calculated as ventilatory duration (s) divided by cycle duration (s) (hyperpnea/hyperpnea + apnea), LG = 2π/(2πDR-sin2πDR).

RESULTS

A total of 11 volunteers were studied. Compared to placebo-control, ACZ/DOB showed a significant increase in the DR (0.79 ± 0.21 vs 0.52 ± 0.03, P = 0.002) and reduction in LG (1.90 ± 0.23 vs 1.29 ± 0.35, P = 0.0004). ACZ/DOB increased cardiac output (CO) (8.19 ± 2.06 vs 6.58 ± 1.56L/min, P = 0.02) and CBF (718 ± 120 vs 526 ± 110ml/min, P < 0.001). There was no significant change in arterial blood gases, minute ventilation (VE), or hypoxic ventilatory response (HVR). However, there was a reduction of hypercapnic ventilatory response (HCVR) by 29% (5.9 ± 2.7 vs 4.2 ± 2.8 L/min, P = 0.1).

CONCLUSION

Pharmacological elevation in CBF significantly reduced LG and severity of CSA. We speculate the effect was on HCVR "controller gain," rather than "plant gain," because PaCO2 and VE were unchanged. An effect via reduced circulation time is unlikely, as the respiratory-cycle length did not change.

Sleep at high altitude: A bibliometric study and visualization analysis from 1992 to 2022

Background

As an important monitoring index for adaptation to hypoxia, sleep may reflect the adaptive state of the body at high altitudes. The literature has shown a link between altitude and sleep problems, and sleep changes have become a common problem for individuals at high altitudes, negatively impacting their physical and mental health. As research on high-altitude sleep has gained attention in recent years, the publishing volume has increased worldwide, necessitating a more comprehensive understanding of this field. This manuscript evaluates the key themes and emerging trends in high-altitude sleep over the past few decades and predicts future research directions.

Methods

Articles related to high-altitude sleep published from 1992 to 2022 were retrieved from the Web of Science Core Collection, and the relevant literature characteristics were extracted after the screening. Then, bibliometric analyses and visualizations were performed using Microsoft Excel, CiteSpace, VOSviewer, and an online analysis platform (http://bibliometric.com).

Results

A total of 1151 articles were retrieved, of which 368 were included in the analysis, indicating a gradually increasing trend. The United States, Switzerland, and China have made significant contributions in this field. Bloch KE from the University of Zurich was determined to be the most productive and academically influential author in this field. The highest-yielding journal was High Altitude Medicine & Biology. Initially, altitude training was the primary research topic. Currently, research focuses on sleep disorders and sleep apnea. In the coming years, keywords such as "sleep quality," "prevalence," and "obstructive sleep apnea" will attract more attention.

Conclusion

Our findings will assist scholars to better understand the intellectual structure and emerging trends in this field. Future developments in high-altitude sleep research are highly anticipated, particularly in terms of sleep quality at high altitudes and its associated prevalence. This research is also crucial for the improvement and treatment of symptoms during nocturnal sleep in patients with chronic hypoxia due to cardiopulmonary diseases at high altitudes.

Ganoderma lucidum Induces Myogenesis Markers to Avert Damage to Skeletal Muscles in Rats Exposed to Hypobaric Hypoxia

Jatwani, Arti, and Rajkumar Tulsawani. Ganoderma lucidum induces myogenesis markers to avert damage to skeletal muscles in rats exposed to hypobaric hypoxia. High Alt Med Biol. 24:287-295, 2023. Background: Hypobaric hypoxia (HH) has been reported to induce skeletal muscle loss and impair myogenesis. Aqueous extract of G. lucidum (AqGL) contains bioactive metabolites attributed to various pharmacological effects. In this study, protective effect of AqGL in ameliorating muscle mass loss following acute HH has been reported. Materials and Methods: Male Sprague-Dawley rats were divided into following five groups of six rats in each group: unexposed control (Group 1), 6 hours of HH exposure (Group 2), 6 hours of HH exposure+AqGL extract 50 mg/kg body weight (BW) (Group 3), 6 hours of HH exposure+AqGL extract 100 mg/kg BW (Group 4), and 6 hours of HH exposure+AqGL extract 200 mg/kg BW (Group 5). Experimental animals from all groups, except Group, 1 were exposed to HH, simulated altitude of 25,000 ft for 6 hours. After exposure period, gastrocnemius muscle was collected, weighed, and morphological, biochemical, and molecular markers were analyzed. Results: HH-exposed rat muscle showed significant (p < 0.05) increase in oxidative stress markers (reactive oxygen species & malondialdehyde), which was concomitant with decrease in its mass compared to controls. AqGL treatment significantly (p < 0.05) prevented muscle oxidative stress, restored reduced glutathione content, reduced protein carbonyl content and advanced oxidation protein product, and restored muscle mass loss at effective dose of 100 mg/kg BW. Furthermore, AqGL supplementation enhanced Myf5 (p < 0.01), MyoD (p < 0.01), MyoG (p < 0.05), and Mrf4 (nonsignificantly), brain-derived neurotrophic factor (p < 0.01), and interleukin 6 (p < 0.01) expression along with restoration of tumor necrosis factor alpha (p < 0.001) and myostatin (p < 0.05) in hypoxia-exposed muscle, evidencing induction of myogenesis markers. Moreover, histological analysis showed increased myocyte number; nuclei shifted toward the periphery in the treatment group supporting muscle regeneration. Conclusion: AqGL supplementation attenuates muscle mass loss by preventing oxidative stress and inducing modulation in myogenesis markers under HH environment.

Night-Time Heart Rate Variability during an Expedition to Mt Everest: A Case Report

Mt Everest has been gaining popularity from casual hiking athletes, climbers, and ultra-endurance marathon runners. However, living and sleeping at altitude increases the risk of injury and illness. This is because travel to high altitudes adversely affects human physiology and performance, with unfavourable changes in body composition, exercise capacity, and mental function. This is a case report of a climber who reached the summit of Mt Everest from the north side. During his 40-day expedition, we collected sleep quality data and night-time heart rate variability. During the night inside the tent, the air temperature ranged from -12.9 to 1.8 °C (-5.8 ± 4.9 °C) and the relative humidity ranged from 26.1 to 78.9% (50.7 ± 16.9%). Awake time was 17.1 ± 6.0% of every sleep-time hour and increased with altitude (r = 0.42). Sleep time (r = -0.51) and subjective quality (r = 0.89) deteriorated with altitude. Resting heart rate increased (r = 0.70) and oxygen saturation decreased (r = -0.94) with altitude. The mean NN, RMSSD, total power, LF/HF, and SD1 and SD2 were computed using the NN time series. Altitude reduced the mean ΝΝ (r = -0.73), RMSSD (r = -0.31), total power (r = -0.60), LF/HF ratio (r = -0.40), SD1 (r = -0.31), and SD2 (r = -0.70). In conclusion, this case report shows that sleeping at high altitudes above 5500 m results in progressively reduced HRV, increased awakenings, as well as deteriorated sleep duration and subjective sleep quality. These findings provide further insight into the effects of high altitude on cardiac autonomic function and sleep quality and may have implications for individuals who frequently spend time at high altitudes, such as climbers.

A bibliometric analysis of the studies in high-altitude induced sleep disturbances and cognitive impairment research

Background: The two main symptoms at high altitude, sleep abnormalities and cognitive impairments, interact with each other. These two dysfunctions are also closely related to systemic multisystem diseases, including cerebrovascular diseases, psychiatric disorders, and immune regulatory diseases. Purpose: To systematically analyze and visualize research on sleep disturbances and cognitive impairment at high altitudes using a bibliometrics method, and to determine future research directions by analyzing research trends and the latest hotspots. Methods: Publications from 1990 to 2022 on sleep disturbances and cognitive impairment at high altitudes were retrieved from the Web of Science. Using the R Bibliometrix software and Microsoft Excel, all data were examined statistically and qualitatively. For network visualization, the data were later exported into VOSviewer 1.6.17 and CiteSpace 6.1.R6. Results: A total of 487 articles in this area were published from 1990 to 2022. In this period, there was an overall increase in the number of publications. The United States has shown considerable importance in this sector. Bloch Konrad E was the most prolific and valuable author. The most prolific journal was High Altitude Medicine & Biology, and it has been the first choice for publishing in this field in recent years. Analysis of keyword co-occurrences suggested that research interest in the clinical manifestations of sleep disturbances and cognitive impairment caused by altitude hypoxia was mainly focused on "acute mountain-sickness," "insomnia," "apnea syndrome," "depression," "anxiety," "Cheyne-strokes respiration," and "pulmonary hypertension." The mechanisms of disease development related to "oxidative stress," "inflammation," "hippocampus," "prefrontal cortex," "neurodegeneration," and "spatial memory" in the brain have been the focus of recent research. According to burst detection analysis, "mood" and "memory impairment," as terms with high strength, are expected to remain hot topics in the coming years. High-altitude-induced pulmonary hypertension is also in the emerging stage of research, and the treatments will continue to receive attention in the future. Conclusion: More attention is being focused on sleep disturbances and cognitive impairment at high altitudes. This work will serve as a useful reference for the clinical development of treatments for sleep disturbances and cognitive impairment induced by hypobaric hypoxia at high altitudes.

Genomic adaptation of Ethiopian indigenous cattle to high altitude

The mountainous areas of Ethiopia represent one of the most extreme environmental challenges in Africa faced by humans and other inhabitants. Selection for high-altitude adaptation is expected to have imprinted the genomes of livestock living in these areas. Here we assess the genomic signatures of positive selection for high altitude adaptation in three cattle populations from the Ethiopian mountainous areas (Semien, Choke, and Bale mountains) compared to three Ethiopian lowland cattle populations (Afar, Ogaden, and Boran), using whole-genome resequencing and three genome scan approaches for signature of selection (iHS, XP-CLR, and PBS). We identified several candidate selection signature regions and several high-altitude adaptation genes. These include genes such as ITPR2, MB, and ARNT previously reported in the human population inhabiting the Ethiopian highlands. Furthermore, we present evidence of strong selection and high divergence between Ethiopian high- and low-altitude cattle populations at three new candidate genes (CLCA2, SLC26A2, and CBFA2T3), putatively linked to high-altitude adaptation in cattle. Our findings provide possible examples of convergent selection between cattle and humans as well as unique African cattle signature to the challenges of living in the Ethiopian mountainous regions.

Does altitude increase the risk of traumatic aortic injuries? A retrospective cohort study among six level I trauma centers in the United States

Background

Traumatic aortic injuries (TAIs) are rare but are associated with a high mortality. Prior studies have shown skiers and pilots, whose injuries occur at high altitudes, are at an increased risk for a TAI. The purpose of this study was to examine the effect of altitude on the incidence of TAIs across all causes of injury.

Methods

This retrospective cohort study at six Level I trauma centers (8/1/2016–1/1/2020) included adult blunt trauma patients with a chest or abdomen injury. High altitude injuries (> 5000 ft.) were compared to low altitude injuries (≤ 5000 ft.). The primary outcome was incidence of TAI.

Results

There were 8562 patients, 37% were at high altitude and 63% at low altitude. High altitude patients were older (p < 0.01), more often Caucasian (p < 0.01) and had a higher ISS (p < 0.01). There was a significantly greater incidence of TAI at high altitude than low altitude (1.5% vs. 1.1%, p = 0.01). The median altitude was significantly higher for patients with a TAI than for patients without a TAI (5100 ft. vs. 1400 ft., p = 0.01). After adjustment, high altitude patients had 2-fold [OR: 2.4 (1.6, 3.7)] greater odds of having a TAI than low altitude patients.

Conclusion

TAIs were more prevalent among high altitude injuries. Providers should be aware of the increased incidence of TAIs at high altitudes particularly when there is a delay in diagnosis and transfer to a trauma center with appropriate resources to manage these critical injuries. TAI screening at high altitude trauma centers may improve survival rates.

Cardiorespiratory function, resting metabolic rate and heart rate variability in coal miners exposed to hypobaric hypoxia in highland workplace

Background

Owing to intermittent/acute exposure to hypobaric hypoxia, highland miners may often suffer, the physiological characteristics between highland and lowland miners, however, are rarely reported. The objective of this study was to compare the physiological characteristics of coal miners working at disparate altitudes.

Methods

Twenty-three male coal mining workers acclimating to high altitude for 30 ± 6 days in Tibet (highland group; approx. 4500 m above sea level; 628.39 millibar), and 22 male coal mining workers in Hebei (lowland group; less than 100 m above sea level; 1021.82 millibar) were recruited. Tests were conducted to compare ventilatory parameters, circulation parameters, resting metabolic rate (RMR), and heart rate variability (HRV) indices between the two groups in resting state.

Results

Ventilation volume per minute (VE) of the highland group was markedly raised compared to that of the lowland group (11.70 ± 1.57 vs. 8.94 ± 1.97 L/min, p = 0.000). In the meanwhile, O2 intake per heart beat (VO2/HR) was strikingly decreased (3.54 ± 0.54 vs. 4.36 ± 0.69 ml/beat, p = 0.000). Resting metabolic rate relevant to body surface area (RMR/BSA) was found no significant difference between the two groups. Evident reduction in standard deviation of NN intervals (SDNN) and remarkable increase in ratio of low- and high- frequency bands (LF/HF) were manifest in highland miners compared to that of lowland ones (110.82 ± 33.34 vs. 141.44 ± 40.38, p = 0.008 and 858.86 ± 699.24 vs. 371.33 ± 171.46, p = 0.003; respectively).

Conclusions

These results implicate that long-term intermittent exposure to high altitude can lead miners to an intensified respiration, a compromised circulation and a profound sympathetic-parasympathetic imbalance, whereas the RMR in highland miners does not distinctly decline.

Pulmonary Capacity, Blood Composition and Metabolism among Coal Mine Workers in High- and Low-Altitude Aboveground and Underground Workplaces

(1) Background: While previous studies revealed how underground mining might adversely affect the cardiopulmonary functions of workers, this study further investigated the differences between under- and aboveground mining at both high and low altitudes, which has received little attention in the literature. (2) Methods: Seventy-one healthy male coal mine workers were recruited, who had worked at least 5 years at the mining sites located above the ground at high (>3900 m; n = 19) and low (<120 m; n = 16) altitudes as well as under the ground at high (n = 20) and low (n = 16) altitudes. Participants’ heart rates, pulmonary functions, total energy expenditure and metabolism were measured over a 5-consecutive-day session at health clinics. (3) Results: Combining the results for both above- and underground locations, workers at high-altitude mining sites had significantly higher peak heart rate (HR), minimum average HR and training impulse as well as energy expenditure due to all substances and due to fat than those at low-altitude sites. They also had significantly higher uric acid, total cholesterol, creatine kinase and N-osteocalcin in their blood samples than the workers at low-altitude mining sites. At underground worksites, the participants working at high-altitude had a significantly higher average respiratory rate than those at low-altitude regions. (4) Conclusion: In addition to underground mining, attention should be paid to high-altitude mining as working under a hypoxia condition at such altitude likely presents physiological challenges.

Elucidating the combined effect of intermittent hypoxia training and acetazolamide on hypoxia induced hematological and physiological changes

As the number of people travelling to altitude increases, the risk of life threatening medical emergencies also increases. It is important that we have effective strategies to minimize the risk of altitude illness. In this study, an attempt was made to investigate the combined effect of non-pharmacological (Intermittent hypoxia training; IHT) and pharmacological (acetazolamide; ACZ) intervention as a prophylactic strategy in order to minimize the risk of high altitude hypoxic related problems using rats as an animal model. Male Sprague Dawley rats were subjected to IHT for 4 h consecutively for 5 days at 12% FiO₂ under normobaric conditions with and without oral ACZ administration at 25 mg/kg body weight. Validation of the intervention was performed by exposing the rats to extreme hypoxia (EH) at 8% FiO₂ to further assess the effect of IHT and ACZ on hypoxic acclimatization. The principal findings of this study is that the combined effect of IHT and ACZ improves the arterial oxygenation by alterations in hemodynamics and in blood gasometry, thereby resulting into an increase in the oxygen carrying capacity of the blood with increase in SpO₂ (peripheral oxygen saturation). The present study showed that the combined effect of IHT with ACZ could be refined as a prophylactic measure for better outcomes during altitude ascent and rapid altitude acclimatization rather than IHT or ACZ alone.

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Combination of IHT with ACZ attenuates the inhibitory effect of respiratory alkalosis.

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It also minimizes pathological changes in hematology and blood gas.

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The strategy improved the oxygen carrying capacity of the blood by increasing SpO₂.

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Thus, it leads to ventilatory Acclimatization.

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The combined treatment could be refined as a prophylactic measure for altitude maladies.

Ethnic Differences on Cardiac Rhythms and Autonomic Nervous System Responses During a High-Altitude Trek: A Pilot Study Comparing Italian Trekkers to Nepalese Porters

Altitude hypoxia exposure results in increased sympathetic activity and heart rate due to several mechanisms. Recent studies have contested the validity of heart rate variability (HRV) analysis on sympathetic activity measurement. But the plethora of HRV metrics may provide meaningful insights, particularly if linked with cardiovascular and autonomic nervous system parameters. However, the population-specific nature of HRV and cardiorespiratory response to altitude hypoxia are still missing. Six Italian trekkers and six Nepalese porters completed 300 km of a Himalayan trek. The ECG analysis was conducted at baseline, and before (bBC) and after (aBC) the high-altitude (HA) circuit. Urine was collected before and after the expedition in Italians, for assessing catecholamines. Heart rate increased with altitude significantly (p < 0.001) in the Italian group; systolic (p = 0.030) and diastolic (p = 0.012) blood pressure, and mean arterial pressure (p = 0.004) increased with altitude. Instead, pulse pressure did not change, although the Nepalese group showed lower baseline values than the Italians. As expected, peripheral oxygen saturation decreased with altitude (p < 0.001), independently of the ethnic groups. Nepalese had a higher respiratory rate (p = 0.007), independent of altitude. The cardiac vagal index increased at altitude, from baseline to bBC (p = 0.008). Higuchi fractal dimension (HFD) showed higher basal values in the Nepalese group (p = 0.041), and a tendency for the highest values at bBC. Regarding the urinary catecholamine response, exposure to HA increased urinary levels, particularly of norepinephrine (p = 0.005, d = 1.623). Our findings suggest a better cardiovascular resilience of the Nepalese group when compared with Italians, which might be due to an intrinsic adaptation to HA, resulting from their job.

Methamphetamine exacerbates pathophysiology of traumatic brain injury at high altitude. Neuroprotective effects of nanodelivery of a potent antioxidant compound H-290/51

Military personnel are often exposed to high altitude (HA, ca. 4500-5000m) for combat operations associated with neurological dysfunctions. HA is a severe stressful situation and people frequently use methamphetamine (METH) or other psychostimulants to cope stress. Since military personnel are prone to different kinds of traumatic brain injury (TBI), in this review we discuss possible effects of METH on concussive head injury (CHI) at HA based on our own observations. METH exposure at HA exacerbates pathophysiology of CHI as compared to normobaric laboratory environment comparable to sea level. Increased blood-brain barrier (BBB) breakdown, edema formation and reductions in the cerebral blood flow (CBF) following CHI were exacerbated by METH intoxication at HA. Damage to cerebral microvasculature and expression of beta catenin was also exacerbated following CHI in METH treated group at HA. TiO2-nanowired delivery of H-290/51 (150mg/kg, i.p.), a potent chain-breaking antioxidant significantly enhanced CBF and reduced BBB breakdown, edema formation, beta catenin expression and brain pathology in METH exposed rats after CHI at HA. These observations are the first to point out that METH exposure in CHI exacerbated brain pathology at HA and this appears to be related with greater production of oxidative stress induced brain pathology, not reported earlier.

Does change in barometric pressure per given time at high altitude influence symptoms of acute mountain sickness on Mount Fuji? A pilot study

Background

Acute mountain sickness (AMS) is a common, transient condition characterized primarily by headaches, and it can also be associated with fatigue, dizziness, and nausea with vomiting. The symptoms of AMS are most pronounced after the first night spent at a new altitude. At sea level, changes in barometric pressure per given time have been associated with migraine headaches. We sought to investigate whether changes in barometric pressure, subjective sleep quality index, and other candidates contributed to the risk of developing AMS on Mount Fuji in Japan.

Method

We surveyed 353 trekkers who stayed overnight at a mountain lodge before summitting Mount Fuji. We collected information regarding sex, age, sleeping altitude at the hut, and perceived sleep quality index including sleep time. AMS was assessed with the Lake Louise Scoring system. Barometric pressure and ambient temperature were collected at the 5th station (2305 m) and at the summit (3776 m).

Result

The overall prevalence of AMS in our cohort was 41.4% (Lake Louise Score ≥ 3 with headache, n=146). Using logistic regression, three factors were combined to generate a robust model for determining the risk of AMS (with or without AMS). These included (1) Δ barometric pressure during ascent per hour, (2) sleepiness on rising, and (3) sleep refreshment assessed by perceived sleep quality index.

Conclusion

These results suggest that climbers who stay overnight at the lodge should keep a better physical condition of sleep, and would pay attention to information of barometric pressure condition to decrease their risk of AMS at the summit of Mount Fuji. Our observatory data indicated that an overnight staying in half way up to the summit does not necessarily reduce the AMS risk in both sexes and irrespective of age, at least, until 3776 m elevation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40101-021-00256-y.

Validation of a Spanish version of the Sleep-Related Breathing Disorder scale of the Pediatric Sleep Questionnaire in children living in a high-altitude city

OBJECTIVES

We aimed to validate a Spanish version of the Sleep-Related Breathing Disorder scale of the Pediatric Sleep Questionnaire (SRBD-PSQ) in children living in a high-altitude Colombian city.

METHODS

In a prospective cohort validation study, patients aged between 2 and 17 years who attended the Ear, Nose, and Throat pediatric department of our institution for symptoms related to sleep-related breathing disorders had a baseline visit at enrollment, a second visit the day scheduled for the surgical intervention, and a follow-up visit at least 3 months after the surgical intervention. In these three visits, we gathered the necessary data for assessing the criterion validity, construct validity, test-retest reliability, internal consistency, and sensitivity to change of the Spanish version of the SRBD-PSQ.

RESULTS

In total, 121 patients were included in the analyses. The exploratory factor analysis (generalized least squares method, varimax rotation) yielded a four-factor structure, explaining 65.93% of the cumulative variance. The intraclass correlation coefficient (ICC) of the measurements was 0.887 (95% CI: 0.809-0.934), and the Lin concordance correlation coefficient was 0.882 (95% CI, 0.821-0.943). SRBD-PSQ scores at baseline were significantly higher than those obtained after adenotonsillectomy surgery (median [IQR] 11.0 [9.0- 14.0] vs. 4.00 [1.50-7.0]; p < 0.0001). Cronbach's α was 0.7055 for the questionnaire as a whole.

CONCLUSIONS

The Spanish version of the SRBD-PSQ has acceptable construct validity, excellent test-retest reliability and sensitivity to change, and adequate internal consistency-reliability when used in pediatric patients living at high altitude with symptoms related to sleep-related breathing disorders.

Normal values for respiratory sleep polygraphy in children aged 4 to 9 years at 2,560 m above sea level

Obstructive sleep apnea syndrome affects 1%-4% of all children worldwide. Currently, diagnosis of obstructive sleep apnea is based on sea-level guidelines, without taking into account the altitude at which the populations live. It has been shown that at 3,200 m of altitude there is an increase in obstructive events in healthy children aged 7 to 16 years; on the other hand, it is known that SpO₂ dispersion between individuals becomes wider as altitude increases, a phenomenon that is more marked during sleep. About 17 million Colombians live in regions between 2,500 m and 2,700 m, as do significant populations in other Latin American countries. This research aimed to characterize respiratory polygraphy sleep parameters in healthy, non-snoring children aged 4-9 years living at 2,560 m. We carried out home respiratory polygraphy in 32 children with a mean age of 6.2 years (range 4-9 years). The average recorded sleep time was 7.8 h, the median apnea-hypopnea index was 9.2/h, the obstructive apnea-hypopnea index had a median of 8.8/h (p5 4.2 to p95 17.9) and central apnea a median of 0.4/h. The median SpO₂ was 93% (p5 90.5 to p95 94) and transcutaneous CO₂ had a median of 39.4 mmHg (p531.7 to p95 42.3). The median oxygen desaturation index ≥ 3% was 11.2 and median oxygen desaturation index ≥ 4% was 3.9. Normal measurements for respiratory polygraphy obtained at sea level do not apply to children at altitude. If such guidelines are used, obstructive sleep apnea will be over-diagnosed, resulting in unnecessary adenotonsillectomies, among other interventions.

Prediction of normal values for central apnea-hypopnea index at different ages and altitudes above sea level in healthy children

BACKGROUND

There is a critical need for studies aimed to help clinicians to establish the normal/expected central apnea-hypopnea index (CAHI) at altitudes above sea level and ages other than those reported in the current available studies. The aim of the present study was to develop predictive models useful for determining the normal/expected CAHI in children of different ages born and living at various altitudes above sea level.

METHODS

A systematic review of the literature was performed in order to identify all available studies that reported on CAHI values measured in healthy children of different ages and living at various levels above sea level. In order to identify factors independently associated with CAHI values, they were fit to multiple linear and quantile regression models.

RESULTS

A total of 16 studies that reported on CAHI values measured in healthy children living at various levels above sea level were included in the analyses. Out of the 16 studies, 12 (75%) were conducted in low-altitude cities, 1 (6.2%) was conducted in a medium-altitude city, 2 (12.5%) in high-altitude cities, and 1 (6.2%) in both low- and high-altitude cities. Age and altitude above sea level are independent predictors of CAHI values in the linear regression analysis and in the quantile regression at the ninetieth percentile.

CONCLUSIONS

The best-fitting prediction equations were obtained with linear regression and quantile regression at the ninetieth percentile analyses, and either of the two models could be used to predict the normal/expected CAHI values in healthy children.

Evaluation of Pulmonary Function Tests Among Pregnant Women of Different Trimesters in Debre Berhan Referral Hospital, Shoa, Ethiopia

Introduction

Pregnancy is characterized by a sequence of dynamic physiological changes that impact multiple organ system functions and is associated with various changes in pulmonary anatomy and physiology. Precise knowledge of the pulmonary function test parameters helps to understand and manage the course and outcome of pregnancy leading to safe delivery. It also helps to avoid misdiagnosis and unnecessary interventions. The aim of this study was to evaluate the effect of normal pregnancy on pulmonary function tests among pregnant women in Debre Berhan Referral Hospital, Ethiopia.

Methods

A total of 176 study participants (first, second, and third trimester; and control) were involved under a comparative cross-sectional study design and convenience sampling technique. Anthropometric data, oxygen saturation of arterial blood, and pulmonary function tests were measured. Data were tabulated and statistically analyzed using SPSS version 20.0 statistical software. Means of all parameters were compared using one-way ANOVA followed by Tukey’s post hoc multiple comparison test. Statistical significance was preset at a p-value of less than 0.05.

Results

Mean of FVC for the controls, first, second, and third trimesters was 2.59 ± 0.26, 2.13 ± 0.15, 1.93 ± 0.27, and 1.90 ± 0.11 liters, respectively. Except for FEV_1%, the mean values of FVC, FEV₁, PEFR, and FEF _25–75% in the pregnant group (all the three trimesters) were significantly decreased from the controls (P<0.05). Strong negative correlation was seen between SaO₂ and RR (r= −0.865; P <0.01). As the pregnancy progressed from first to the third trimester, dynamic pulmonary function tests (FVC, FEV₁, FEF_25-75%, and PEFR) were dropped and the respiratory rate increased.

Conclusion

The results had shown the tendency of obstructive pattern while pregnancy becoming advanced. We have observed also a remarkable decline of SaO₂ in pregnant women that might be counterbalanced by raised respiratory rate.

Acute Altitude Acclimatization in Young Healthy Volunteers: Nocturnal Oxygenation Increases Over Time, Whereas Periodic Breathing Persists

Ju, Jia-Der, Cristian Zhang, Francis P. Sgambati, Lidia M. Lopez, Luu V. Pham, Alan R. Schwartz, and Roberto A. Accinelli. Acute altitude acclimatization in young healthy volunteers: nocturnal oxygenation increases over time whereas periodic breathing persists. High Alt Med Biol. 22:14-23, 2021. Study Objectives: This study aimed to examine the acute effects of high altitude (HA) on sleep disordered breathing (sleep apnea and nocturnal hypoxemia) and acute mountain sickness and to characterize acclimatization over time. Methods: Ten native lowlanders residing at sea level (SL) completed the Lake Louise Score (LLS) and underwent nocturnal polygraphy (ApneaLink Plus) for nine consecutive nights (N1-N9) at HA (2,761 m) and two nights before and after HA. Nocturnal oxygen profiles were assessed by measuring the mean nocturnal oxyhemoglobin saturation (S_pO₂) during sleep, and sleep apnea severity as assessed by measuring the Apnea-Hypopnea Index (AHI). Mixed-effects linear regression was used to model responses in outcomes (mean nocturnal S_pO₂, logAHI, and LLS) between HA and SL. Changes in S_pO₂ and AHI were examined in subgroups with mild versus marked nocturnal S_pO₂ and low versus high AHI during exposure to HA and compared between subgroups. Results: Compared with SL, the mean nocturnal S_pO₂ was lower (p < 0.0001) and AHI was higher (p < 0.0001) at HA. The mean nocturnal S_pO₂ increased progressively (p < 0.001), whereas AHI remained high (p < 0.978) and relatively unchanged over nine successive nights at HA. Those with markedly reduced S_pO₂ upon arrival at HA exhibited progressive increases in the mean nocturnal S_pO₂ over time at HA compared with those with mild nocturnal desaturation. LLS rose at HA, but no differences were observed between subgroups. Conclusions: In healthy HA sojourners, the mean nocturnal S_pO₂ increased progressively over time, whereas AHI remained elevated, suggesting distinctive phenotypes and acclimatization responses to HA.

Case studies in physiology: Nocturnal cardiorespiratory adaptive differences between an Italian trekker and a Nepali guide

The cardiopulmonary system is a physiological cornerstone in the adaptive response to hypobaric hypoxia. Portable devices make it feasible nowadays to precisely assess the response to high altitude (HA) expeditions. In this study, we investigated breathing and arterial blood pressure responses during a Himalayan trek from 665 m to 4,780 m altitude in a white European (Italian) sojourner and a native Nepali (Tamang) guide, both healthy males. Resting diurnal and nocturnal data were acquired by means of ambulatory blood pressure monitoring (ABPM) and sleep apnea monitoring. We found an increase in the mean diurnal arterial blood pressure. Nocturnal blood pressure dipping was confirmed at all altitudes. Oxygen saturation decreased at altitude, with its additional nocturnal fall. Sleep apneic episodes, present in the Italian only, increased with altitude. We conclude that the nocturnal, more than diurnal, cardiorespiratory function is affected by HA hypoxia. Further studies should address the role of ethnicity, medications, and sociodemographic factors in the cardiorespiratory responses to hypobaric hypoxia.

COVID-19 and Pneumolysis Simulating Extreme High-altitude Exposure with Altered Oxygen Transport Physiology; Multiple Diseases, and Scarce Need of Ventilators: Andean Condor's-eye-view

BACKGROUND

Critical hypoxia in this COVID-19 pandemic results in high mortality and economic loss worldwide. Initially, this disease' pathophysiology was poorly understood and interpreted as a SARS (Severe Acute Respiratory Syndrome) pneumonia. The severe atypical lung CAT scan images alerted all countries, including the poorest, to purchase lacking sophisticated ventilators. However, up to 88% of the patients on ventilators lost their lives. It was suggested that COVID-19 could be similar to a High-Altitude Pulmonary Edema (HAPE). New observations and pathological findings are gradually clarifying the disease.

METHODS

As high-altitude medicine and hypoxia physiology specialists working and living in the highlands for over 50 years, we perform a perspective analysis of hypoxic diseases treated at high altitudes and compare them to Covid-19. Oxygen transport physiology, SARS-Cov-2 characteristics, and its transmission, lung imaging in COVID-19, and HAPE, as well as the causes of clinical signs and symptoms, are discussed.

RESULTS

High-altitude oxygen transport physiology has been systematically ignored. COVID-19 signs and symptoms indicate a progressive and irreversible failure in the oxygen transport system, secondary to pneumolysis produced by SARS-Cov-2's alveolar-capillary membrane "attack". HAPE's pulmonary compromise is treatable and reversible. COVID-19 is associated with several diseases, with different individual outcomes, in different countries, and at different altitudes.

CONCLUSIONS

The pathophysiology of High-altitude illnesses can help explain COVID-19 pathophysiology, severity, and management. Early diagnosis and use of EPO, acetylsalicylic-acid, and other anti-inflammatories, oxygen therapy, antitussives, antibiotics, and the use of Earth open-circuit- astronaut-resembling suits to return to daily activities, should all be considered. Ventilator use can be counterproductive. Immunity development is the only feasible long-term survival tool.

Saliva panel of protein candidates: A comprehensive study for assessing high altitude acclimatization

Altitude acclimatization describes the processes whereby lowland humans respond to decreased partial pressure of oxygen. It refers to the changes seen as beneficial and involves a series of physiological adjustments that compensate for reduced ambient PO₂, as opposed to changes that are pathological. Although numerous reports document the physiological effects of exposure to hypobaric hypoxia of varying durations but an interesting aspect overlooked by many researchers is that of acclimatization related studies. As proteome, a dynamic entity responds immediately to external stimuli, protein markers and their trends can be studied to assess acclimatization status of an individual. Compared to blood, the use of saliva is advantageous because sample collection and processing are easy, minimally invasive, low cost and better tolerated by individuals. In this study, we employed iTRAQ based LC-MS/MS technique for comparing saliva samples from humans exposed to hypobaric hypoxia from 7 to 120 days with normoxic controls followed by analysis using Ingenuity Pathway Analysis software and validation by immunoassays. Nearly 67 proteins were found to be differentially expressed in the exposed groups as compared to normoxia indicating modulated canonical pathways as lipid metabolism; acute phase response signalling and proteins as carbonic anhydrase 6, alpha-enolase, albumin, and prolactin inducible protein. Collectively, this study provides the proof of concept for the non-invasive assessment of high altitude acclimatization.

The effect of sleep quality in Sherpani Col High Camp Everest

Recently, an increasingly higher volume of travelers deciding to get the experience of hiking to the highest summit worldwide has been noted. However, high altitude environments have adverse effects on the normal bodily function of individuals accustomed to living at low altitudes. The purpose of this study was to record sleep quality and physiological responses of 8 climbers during a 7 days stay at Sherpani Col High Camp Everest in an altitude of 5700-m. Eight experienced climbers (Age: 48 ± 9.2 yrs, Height: 176.3 ± 7.1 cm, Body mass: 76.9 ± 11.7 kg, weekly exercise >80% HR_max > 270 min^-1) participated in the study. The climbers recorded their sleep quality daily and one hour after waking up via a questionnaire (Groningen Sleep Quality Scale, GSQS), levels of perceived exertion (Borg CR10 Scale), heart rate (HR, bpm^-1) and oxygen saturation in blood (SpO₂, %) using the pulse oximeter Nonin Onyx Vantage 9590 (USA). Climbers also filled out questionnaires regarding how sleepy they felt (Epworth Sleepiness Score, ESS) 12 h post waking-up. Repeated measures ANOVA were used in order to examine possible variations between variables. Results showed statistical significant differences in the HR and SpO₂ parameters, (HR: 86.5 ± 5.2 bpm^-1, p < 0.05; SpO₂: 85.3 ± 2.4%, p < 0.05). The subjective evaluation of GSQS, ESS and perceived exertion using a Borg CR10 Scale may be affected by the extreme hypoxic environment and the daily hike-climb which results in low blood oxygen saturation.

Effects of altitude on chronotype orientations in relation to cardiorespiratory and hematological quantities of college students in Ethiopia

BACKGROUND

The mechanism by which Ethiopians adapt to altitude is quite unique compared to other Highlanders with respect to increased oxygen saturation of hemoglobin. Although the effects of altitude on cardiorespiratory and hematological quantities on athletics performances are well known, but there is little information about its underlying effect on chronotype orientations.

METHODS

In this cross-sectional study 60 male college students with mean age 20±1.3 years from high and low altitude regions living in a tropical setting in Ethiopia were included. The participants' chronotype was determined using the self-administered Horne and Ostberg Morningness-Eveningness Questionnaires (MEQ). Measurements and estimations of hematological and cardiorespiratory parameters were performed from 7:00-9:00 AM, East African time zone, in order to minimize any variations that might occur in the course of the day. A multivariate binary logistic regression model was fitted to analyze the underlying chronotype predictors.

RESULTS

28 (93.9%) of participants from high altitude were mainly intermediate type (I-type) dominant with (MEQ = 42-58). While, 16 (55.2%) of participants from low altitudes were morning type (M-type) dominant chronotype with (MEQ = 59-69). Our main finding confirmed that altitude is an independent predictor of chronotype orientations of the participants (p<0.015). Thus, the results of the multivariate analysis seem to indicate that, participants from low and high altitudes may be uniquely oriented towards either M-type or I-type chronotype respectively (adjusted odds ratio [AOR] 4.772, 95% CI = 3.748-4618458). However, no significant difference on cardiorespiratory and hematological quantities between I-type and M-type chronotype of students from low altitude living in the same setting was reported (p > 0.05).

CONCLUSION

Our finding, reported for the first time that, the human chronotype varies according to the altitude, with no underlying effect of cardiorespiratory and hematological quantities.

Severe sleep apnea, Cheyne-Stokes respiration and desaturation in patients with decompensated heart failure at high altitude

Objectives:

To determine the sleep-disordered breathing in patients with decompensated HF (DHF) at an altitude of 2640m.

Methods:

Polysomnogram during the first 48 hours of admission in patients hospitalized for DHF. Sleep apnea (SA) was defined as an apnea hypopnea index (AHI) > 5/hour and central sleep apnea (CSA) as central apnea index (CAI) ≥ 50% of the AHI.

Results:

Sixteen participants, LVEF 24.2±9.9%. All patients had SA, severe in 12 (75%), CSA in 8 (50%) and 7 (43.8%) presented Cheyne-Stokes respiration (CSR). Out of the eight patients with obstructive SA, five had a central component (CAI ≥ 5/h). The SpO2 decreased during sleep to 80.6±5.5% and in patients with CSR to 77.6±6.9%.

Conclusions:

At an altitude of 2640m all patients with DHF presented sleep apnea, most were severe, with CSA and a significant percentage of CSR that was associated with higher oxygen desaturation.

Sleep disorders in adolescents and young adults: Insights into types, relationship to obesity and high altitude and possible lines of management

A sleep disorder is a medical disorder of the sleep pattern of a person that may be serious enough to interfere with normal physical, mental and emotional functioning. Disruptions in sleep can be caused by a variety of causes, from teeth grinding to night terrors. Sleep disorders are usually prevalent among adolescents and young adults, possibly due to factors related to life style, dietary habits, hormonal and emotional disturbances. Other factors that may precipitate sleep disorders include environmental, psychological and genetic factors. Sleep disorders may lead to serious psychological and mood disorders and may even affect the immune system. Management of sleep disorders depends on amelioration of the precipitating factors and the use of certain drugs that may help to restore the normal sleep-wake cycle. This review sheds light on sleep disorders in adolescents and young adults regarding their types, etiology, dangers and possible lines of management.

Sleep disorders in a sample of students in Taif University, Saudi Arabia: The role of obesity, insulin resistance, anemia and high altitude

AIM

The aim of this study was to assess the incidence of sleep disorders and excessive daytime sleepiness (EDS) among Taif University students and to explore the precipitating factors of these disorders.

METHODS

This study was carried out on 1066 students in Taif University of both sexes aging from 18 to 25 years. All included individuals were subjected to full history taking and thorough clinical examination, with special concern on anthropometric measurements (weight, height, waist-to-hip ratio and body mass index). Also, fasting blood glucose, fasting serum insulin, homeostatic model assessment (HOMA) index and blood hemoglobin levels were measured. Sleep disorders were assessed using sleep disturbances scale and the Epworth sleepiness scale.

RESULTS

The overall incidence of sleep disorders and EDS was 31.33% and 15.29% respectively with statistically significant prevalence in females than males. There was significant positive correlation between sleep disturbances scale and Epworth sleepiness scale on one hand and body weight, body mass index, waist-to-hip ratio, the height of the residence place above the sea level, fasting and post-prandial blood glucose, fasting serum insulin and HOMA index on the other hand. Also, there was significant negative correlation between sleep disturbances scale and Epworth sleepiness scale on one hand and blood hemoglobin levels on the other hand.

CONCLUSION

Sleep disorders and EDS in Taif University students were precipitated by high altitude, anemia, obesity and glucose intolerance. Control of these factors may have a positive impact on the incidence of sleep disorders and EDS in this age group.

Prevalence and risk factors associated with hypertension and prehypertension in a working population at high altitude in China: a cross-sectional study

Background

Little information is available on the epidemiology of hypertension and prehypertension at high altitude in China, the aim of this study was to determine the prevalence of hypertension, prehypertension and their risk factors among Chinese working population at high altitude regions.

Methods

A cross-sectional survey was performed in an occupational sample of 4198 employees aged 20–59 years on Qinghai-Tibet Plateau between May to July 2013. Information from a self-administered questionnaire, physical examinations and laboratory measurements were obtained from each participant. Multivariable analysis was performed to determine the association of various risk factors with hypertension and prehypertension.

Results

The total crude prevalence of hypertension and prehypertension was 28.1 and 41.5%, respectively; the overall standardized prevalence of hypertension and prehypertension was 26.7 and 41.3%, respectively. Multivariate logistic regression showed that age, sex, ethnicity, job position, overweight or obesity, frequent drinking, family history of hypertension, diabetes and hyperuricemia were risk factors for hypertension, and age, sex, education, job position, overweight or obesity, current smoking and family history of hypertension were risk factors for prehypertension. Among the hypertensives, 36.5% were aware of their condition, 19.4% were being treated and 6.2% had their blood pressure (BP) controlled; among the treated hypertensives, 31.9% had their BP under control.

Conclusions

There is a high prevalence of hypertension and prehypertension in the working population at high altitude in China, but with very low awareness, treatment and control rates. Workplace-based BP screening and intervention programs that aim to modify risk factors such as high BMI, tobacco use, alcohol consumption and inappropriate use of antihypertensive medicine are urgently needed.

Electronic supplementary material

The online version of this article (doi:10.1186/s12199-017-0634-7) contains supplementary material, which is available to authorized users.

Effects of Short-Term Acclimatization at the Summit of Mt. Fuji (3776 m) on Sleep Efficacy, Cardiovascular Responses, and Ventilatory Responses

Horiuchi, Masahiro, Shiro Oda, Tadashi Uno, Junko Endo, Yoko Handa, and Yoshiyuki Fukuoka. Effects of short-term acclimatization at the summit of Mt. Fuji (3776 m) on sleep efficacy, cardiovascular responses, and ventilatory responses. High Alt Med Biol. 18:171-178, 2017.-We investigated the effects of a short period of acclimatization, at 3776 m on Mt. Fuji, on sleep parameters and related physiological responses. Physiological responses were assessed in seven healthy lowlander men during both daytime and sleep while at sea level (SL), as well as for three consecutive nights at high altitude (HA; 3776 m, day 1 [D1], D2, D3, and morning only of D4). Blood pressure variables, heart rate (HR), pulmonary ventilation (V_E), and breathing frequency (Bf) progressively increased each day, with significant differences between SL and HA (p < 0.05, respectively). In contrast, end-tidal PCO₂ (P_ETCO₂) progressively decreased each day with statistical differences between SL and D3 at HA (p < 0.05). During sleep at HA, mean arterial pressure (MAP) was stable, whereas it decreased during sleep at SL. Sleep efficacy, which was assessed by actigraphy, was linearly impaired with statistical differences between SL and D3 (p < 0.05). These impairments in sleep efficacy at HA were associated with higher MAP and HR, as well as lower Bf and P_ETCO₂ during the daytime (pooled data, p < 0.05, respectively). These results suggest that hypoxia-induced cardiovascular and ventilatory responses may be crucial contributors to changes in sleep efficacy at HA.

Overnight Polysomnographic Characteristics and Oxygen Saturation of Healthy Infants, 1 to 18 Months of Age, Born and Residing At High Altitude (2,640 Meters)

BACKGROUND

Approximately 8% of the world population resides above 1,600 m, with about 10 million people living above 2,500 m in Colombia. However, reference values for polysomnography (PSG) and oxygen saturation (Spo2) of children < 2 years old residing at high altitude are currently unavailable.

METHODS

Healthy infants aged 1 to 18 months born and residing at high altitude (Bogotá: 2,640 m) underwent overnight PSG. Four age groups were defined: group 1, < 45 days; group 2, 3 to 4 months; group 3, 6 to 7 months; and group 4, 10 to 18 months. Of 122 children enrolled, 50 had three consecutive PSG tests and were analyzed as a longitudinal subcohort.

RESULTS

A total of 281 PSG tests were performed in 122 infants (56% girls): group 1, 106 PSG tests; group 2, 89 PSG tests; group 3, 61 PSG tests; and group 4, 25 PSG tests. Active sleep diminished and quiet sleep increased with maturation. Apnea-hypopnea indexes (total, central, and obstructive) were highest in group 1 (21.4, 12.4, and 6.8/h total sleep time, respectively) and diminished with age (P < .001). Mean Spo2 during waking and sleep increased with age (P < .001). Nadir Spo2 values during respiratory events were lower in younger infants. Longitudinal assessments of 50 infants confirmed the temporal trends described for the cross-sectional dataset.

CONCLUSIONS

Healthy infants (≤ 18 months old) born and residing at high altitude show preserved sleep architecture but higher apnea-hypopnea indexes and more prominent desaturation with respiratory events than do those living at low altitude. The current study findings can be used as reference values for infants at high altitude.

Time-varying signal analysis to detect high-altitude periodic breathing in climbers ascending to extreme altitude

This work investigates the performance of cardiorespiratory analysis detecting periodic breathing (PB) in chest wall recordings in mountaineers climbing to extreme altitude. The breathing patterns of 34 mountaineers were monitored unobtrusively by inductance plethysmography, ECG and pulse oximetry using a portable recorder during climbs at altitudes between 4497 and 7546 m on Mt. Muztagh Ata. The minute ventilation (VE) and heart rate (HR) signals were studied, to identify visually scored PB, applying time-varying spectral, coherence and entropy analysis. In 411 climbing periods, 30-120 min in duration, high values of mean power (MP(VE)) and slope (MSlope(VE)) of the modulation frequency band of VE, accurately identified PB, with an area under the ROC curve of 88 and 89%, respectively. Prolonged stay at altitude was associated with an increase in PB. During PB episodes, higher peak power of ventilatory (MP(VE)) and cardiac (MP(LF)(HR) ) oscillations and cardiorespiratory coherence (MP(LF)(Coher)), but reduced ventilation entropy (SampEn(VE)), was observed. Therefore, the characterization of cardiorespiratory dynamics by the analysis of VE and HR signals accurately identifies PB and effects of altitude acclimatization, providing promising tools for investigating physiologic effects of environmental exposures and diseases.

Medication effects on sleep and breathing

Sleep respiration is regulated by circadian, endocrine, mechanical and chemical factors, and characterized by diminished ventilatory drive and changes in Pao2 and Paco2 thresholds. Hypoxemia and hypercapnia are more pronounced during rapid eye movement. Breathing is influenced by sleep stage and airway muscle tone. Patient factors include medical comorbidities and body habitus. Medications partially improve obstructive sleep apnea and stabilize periodic breathing at altitude. Potential adverse consequences of medications include precipitation or worsening of disorders. Risk factors for adverse medication effects include aging, medical disorders, and use of multiple medications that affect respiration.