Blood pressure changes in young male subjects exposed to a median altitude

Changes in blood pressure, oxygen saturation, hemoglobin concentration, and heart rate among low-altitude migrants living at high altitude (5380 m) for 360 days

BACKGROUND

This article aimed to study the adjustment and adaptation of resting systolic blood pressure (SBP), diastolic blood pressure (DPB), oxygen saturation (SpO2 ), hemoglobin concentration ([Hb]), and heart rate (HR) in low-altitude migrants during a 1-year stay at high altitude.

MATERIALS AND METHODS

Our study enrolled 35 young migrants who were exposed to a hypoxia environment at 5380 m altitude on the Qinghai Tibetan Plateau between June 21, 2017, and June 16, 2018. We set 14-time points (the 1st-10th, 20th, 30th, 180th, and 360th day after arriving at 5380 m) for obtaining the measurements of resting SBP, DBP, HR, SpO2, and [Hb] and compared them with the control values recorded prior to migration. Variables with continuous data were summarized as means (SD). One-way repeated measures ANOVA without assuming sphericity was carried out to test whether the mean values (SBP, DBP, HR, SpO2 , and [Hb]) on different days were different significantly. Furthermore, Dunnett's multiple comparisons test was carried out to determine the time points whose values were significantly different from the control values.

RESULTS

SBP and DBP were continually increasing within d1-3 and peaked on the 3rd day, then steadily declined from d3 to d30. SBP fell back to the control values on d10 (p > 0.05), and DBP fell back to the control values on d20 (p > 0.05). A significant decline occurred on d180 (p < 0.05). Both SBP and DBP were lower than the control values on d180 (p < 0.05), and this trend was maintained to d360. There were similar characteristics of HR and BP in the time course at HA. HR on d1-3 was increasing (p < 0.05) compared to the control values, after which it fell back to the control values on d180 (p > 0.05), and this trend was maintained to d360. SpO2 was the lowest on d1 and lower than the control value throughout the study at HA (p < 0.05). [Hb] increased after long-term exposure (180 and 360 days) to HA (p < 0.05).

CONCLUSIONS

Our study continuously monitored lowlanders at 5380 m in Tibet, and is perhaps the only longitudinal study of migrants conducted at an altitude above 5000 m during a 1-year period. Our study provides new information on the adjustment and adaptation of [Hb], SpO2 , SBP, DBP, and HR in high-altitude plateau migrants during a 360-day stay at an altitude of 5380 m.

Blood Pressure Variation with Altitudes in Children: A Cross-Sectional Observational Study from Himalayan Hills

OBJECTIVES

We aimed to evaluate blood pressure (BP) in Indian children who had similar demographic characteristics but hailed from different altitudes.

METHODS

BP of school going children, aged 5 to 12 years, at five different locations varying in altitude (near sea level: n = 425; 2000 feet: n = 244; 4000 feet: n = 248; 6000 feet: n = 242 and 8000 feet: n = 250) was measured in a mountainous district in Himalaya. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were recorded by aneroid sphygmomanometer in the sitting posture using a calibrated instrument and four trained resident doctors. The average of three readings was taken.

RESULTS

Of the 1229 children whose data were analyzed, 50.4% were boys. SBP showed a progressive rise from 99.5 (4.00) mmHg [mean (standard deviation)] at near sea level to 106.7 (4.17) mmHg at 8000 feet. Similarly, DBP showed a rise from 60.1 (3.67) mmHg to 66.8 (4.58) mmHg over the same altitude range. Analysis of covariance for BP variation with altitude, with age as covariate, indicated a modest but statistically significant rise in both SBP and DBP with altitude. Higher BP values was noted among children residing at higher than at lower altitude (0.8% at sea level to 18.8% at 8000 feet). Correlations between SBP and DBP values and height and weight, though positive and significant at p < 0.01 level, were weak.

CONCLUSIONS

These data will help in correct interpretation of BP readings in children residing at high altitude.

Variation of vital signs with potential to influence the performance of qSOFA scoring in the Ethiopian general population at different altitudes of residency: A multisite cross-sectional study

Introduction

The physiological range of different vital signs is dependent on various environmental and individual factors. There is a strong interdependent relationship between vital signs and health conditions. Deviations of the physiological range are commonly used for risk assessment in clinical scores, e.g. respiratory rate (RR) and systolic blood pressure (BP_sys) in patients with infections within the quick sequential organ failure assessment (qSOFA) score. A limited number of studies have evaluated the performance of such scores in resource-limited health care settings, showing inconsistent results with mostly poor discriminative power. Divergent standard values of vital parameters in different populations, e.g. could influence the accuracy of various clinical scores.

Methods

This multisite cross-sectional observational study was performed among Ethiopians residing at various altitudes in the cities of Asella (2400m above sea level (a.s.l.)), Adama (1600m a.s.l.), and Semara (400m a.s.l.). Volunteers from the local general population were asked to complete a brief questionnaire and have vital signs measured. Individuals reporting acute or chronic illness were excluded.

Results

A positive qSOFA score (i.e. ≥2), indicating severe illness in patients with infection, was common among the studied population (n = 612). The proportion of participants with a positive qSOFA score was significantly higher in Asella (28.1%; 55/196), compared with Adama, (8.3%; 19/230; p<0.001) and Semara (15.1%; 28/186; p = 0.005). Concerning the parameters comprised in qSOFA, the thresholds for RR (≥22/min) were reached in 60.7%, 34.8%, and 38.2%, and for BP_sys (≤100 mmHg) in 48.5%, 27.8%, and 36.0% in participants from Asella, Adama, and Semara, respectively.

Discussion

The high positivity rate of qSOFA score in the studied population without signs of acute infection may be explained by variations of the physiological range of different vital signs, possibly related to the altitude of residence. Adaptation of existing scores using local standard values could be helpful for reliable risk assessment.

Echoes from Gaea, Poseidon, Hephaestus, and Prometheus: environmental risk factors for high blood pressure

High blood pressure (BP) affects over one billion people and is the leading risk factor for global mortality. While many lifestyle and genetic risk factors are well-accepted to increase BP, the role of the external environment is typically overlooked. Mounting evidence now supports that numerous environmental factors can promote an elevation in BP. Broadly speaking these include aspects of the natural environment (e.g., cold temperatures, higher altitude, and winter season), natural disasters (e.g., earthquakes, volcanic eruptions), and man-made exposures (e.g., noise, air pollutants, and toxins/chemicals). This is important for health care providers to recognize as one (or several) of these environmental factors could be playing a clinically meaningful role in elevating BP or disrupting hypertension control among their patients. At the population level, certain environmental exposures may even be contributing to the growing pandemic of hypertension. Here we provide an updated review of the literature linking environment exposures with high BP and outline practical recommendations for clinicians.

High altitude-related hypertensive crisis and acute kidney injury in an asymptomatic healthy individual

BACKGROUND

High-altitude exposure causes a mild to moderate rise in systolic and diastolic blood pressure. This case report describes the first documented case of a hypertensive crisis at altitude, as well as the first report of the occurrence of acute kidney injury in the context of altitude-related hypertension.

CASE PRESENTATION

A healthy, previously normotensive 30-year old, embarked on a trek to Everest Base Camp (5300 m). During his 11-day ascent the subject developed increasingly worsening hypertension. In the absence of symptoms, the individual initially elected to remain at altitude as had previously been the plan. However, an increase in the severity of his hypertension to a peak of 223/119 mmHg resulted in a decision to descend. On descent he was found to have an acute kidney injury that subsequently resolved spontaneously. His blood pressure reverted to normal at sea level and subsequent investigations including a transthoracic echocardiogram, cardiac magnetic resonance imaging, renal ultrasound, and urinary catecholamines were normal.

CONCLUSION

This report challenges the view that transient rises in blood pressure at altitude are without immediate risk. We review the evidence that altitude induces hypertension and discuss the implications for the management of hypertension at altitude.

Relationship between altitude and the prevalence of hypertension in Tibet: a systematic review

Introduction

Hypertension is a leading cause of cardiovascular disease, which is the cause of one-third of global deaths and is a primary and rising contributor to the global disease burden. The objective of this systematic review was to determine the prevalence and awareness of hypertension among the inhabitants of Tibet and its association with altitude, using the data from published observational studies.

Methods

We conducted electronic searches in Medline, Embase, ISI Web of Science and Global Health. No gender or language restrictions were imposed. We assessed the methodological characteristics of included studies using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) criteria. Two reviewers independently determined the eligibility of studies, assessed the methodology of included studies and extracted the data. We used meta-regression to estimate the degree of change in hypertension prevalence with increasing altitude.

Results

We identified 22 eligible articles of which eight cross-sectional studies with a total of 16 913 participants were included. The prevalence of hypertension ranged between 23% and 56%. A scatter plot of altitude against overall prevalence revealed a statistically significant correlation (r=0.68; p=0.04). Meta-regression analysis revealed a 2% increase in the prevalence of hypertension with every 100 m increase in altitude (p=0.06). The locations and socioeconomic status of subjects affected the awareness and subsequent treatment and control of hypertension.

Conclusions

The results from cross-sectional studies suggest that there is a significant correlation between altitude and the prevalence of hypertension among inhabitants of Tibet. The socioeconomic status of the inhabitants can influence awareness and management of hypertension. Very little research into hypertension has been conducted in other prefectures of Tibet where the altitude is much higher. Further research examining the impact of altitude on blood pressure is warranted.

Control of breathing and the circulation in high-altitude mammals and birds

Hypoxia is an unremitting stressor at high altitudes that places a premium on oxygen transport by the respiratory and cardiovascular systems. Phenotypic plasticity and genotypic adaptation at various steps in the O2 cascade could help offset the effects of hypoxia on cellular O2 supply in high-altitude natives. In this review, we will discuss the unique mechanisms by which ventilation, cardiac output, and blood flow are controlled in high-altitude mammals and birds. Acclimatization to high altitudes leads to some changes in respiratory and cardiovascular control that increase O2 transport in hypoxia (e.g., ventilatory acclimatization to hypoxia). However, acclimatization or development in hypoxia can also modify cardiorespiratory control in ways that are maladaptive for O2 transport. Hypoxia responses that arose as short-term solutions to O2 deprivation (e.g., peripheral vasoconstriction) or regional variation in O2 levels in the lungs (i.e., hypoxic pulmonary vasoconstriction) are detrimental at in chronic high-altitude hypoxia. Evolved changes in cardiorespiratory control have arisen in many high-altitude taxa, including increases in effective ventilation, attenuation of hypoxic pulmonary vasoconstriction, and changes in catecholamine sensitivity of the heart and systemic vasculature. Parallel evolution of some of these changes in independent highland lineages supports their adaptive significance. Much less is known about the genomic bases and potential interactive effects of adaptation, acclimatization, developmental plasticity, and trans-generational epigenetic transfer on cardiorespiratory control. Future work to understand these various influences on breathing and circulation in high-altitude natives will help elucidate how complex physiological systems can be pushed to their limits to maintain cellular function in hypoxia.

Correlation between blood pressure changes and AMS, sleeping quality and exercise upon high-altitude exposure in young Chinese men

BACKGROUND

Excessive elevation of arterial blood pressure (BP) at high altitude can be detrimental to our health due to acute mountain sickness (AMS) or some AMS symptoms. This prospective and observational study aimed to elucidate blood pressure changes induced by exposure to high-altitude hypoxia and the relationships of these changes with AMS prevalence, AMS severity, sleep quality and exercise condition in healthy young men.

METHODS

A prospective observational study was performed in 931 male young adults exposed to high altitude at 3,700 m (Lhasa) from low altitude (LA, 500 m). Blood pressure measurement and AMS symptom questionnaires were performed at LA and on day 1, 3, 5, and 7 of exposure to high altitude. Lake Louise criteria were used to diagnose AMS. Likewise, the Athens Insomnia Scale (AIS) and the Epworth Sleepiness Scale (ESS) were filled out at LA and on day 1, 3, and 7 of exposure to high altitude.

RESULTS

After acute exposure to 3,700 m, diastolic blood pressure (DBP) and mean arterial blood pressure (MABP) rose gradually and continually (P < 0.05). Analysis showed a relationship with AMS for only MABP (P < 0.05) but not for SBP and DBP (P > 0.05). Poor sleeping quality was generally associated with higher SBP or DBP at high altitude, although inconsistent results were obtained at different time (P < 0.05). SBP and Pulse BP increased noticeably after high-altitude exercise (P < 0.05).

CONCLUSIONS

Our data demonstrate notable blood pressure changes under exposure to different high-altitude conditions: 1) BP increased over time. 2) Higher BP generally accompanied poor sleeping quality and higher incidence of AMS. 3) SBP and Pulse BP were higher after high-altitude exercise. Therefore, we should put more effort into monitoring BP after exposure to high altitude in order to guard against excessive increases in BP.

Cross-sectional study of sociodemographic patterning of risk factors for cardiovascular disease in three isolated-based subgroups of the Uyghur population in Xinjiang, China

OBJECTIVE

To explore the sociodemographic patterning of risk factors for cardiovascular disease (CVD) in three isolated-based subgroups of the Uyghur population in Xinjiang, China.

DESIGN

A cross-sectional study. Between 2005 and 2008, a non-probability sampling design method was used to select three specific groups of the Uyghur rural populations based on their potential socioeconomic status (ie, isolated, semi-isolated and open-environment status).

SETTING

Three communities (named Desert, Turpan and Yuli Rob) in Southern Xinjiang autonomous region, China.

PARTICIPANTS

1656 people were included in this study. The inclusion criteria were that all participants were 18 years or older, they were descendants of at least three generations living in the same region, and there was no history of intermarriage.

MAIN OUTCOME MEASURES

The prevalence of CVD risk factors (ie, tobacco use, alcohol use, obesity, dyslipidemia, hypertension, diabetes, etc) was assessed.

RESULTS

Compared with the Desert and Turpan communities, Yuli Rob had the highest levels of obesity, dyslipidemia and hypertension, and the Desert had the lowest levels of CVD risk factors. Age standardisation slightly altered the estimates, though the patterns remained unchanged. Some unique characteristics were also found. For example, the Desert group displayed significantly lower high-density lipoprotein cholesterol (HDLC) level compared with Yuli Rob and Turpan groups. The mean values were 0.63, 1.06 and 1.45 mmol/l for men and 0.64, 1.22 and 1.51 mmol/l for women (p<0.0001). The HDLC levels in the Desert group increased with increase in body mass index and fasting glucose levels, which was inconsistent with previous studies.

CONCLUSIONS

Identifying the unique CVD risk factors of the ethnic-specific populations is very important in development of tailored strategies for the prevention of CVD.

Hemodynamics and metabolism at low versus moderate altitudes

Despite the higher prevalence of diabetes and hypertension in populations residing at moderate altitudes, mortality in these populations is lower than in populations residing at low altitudes. To examine whether metabolic and hemodynamic differences can explain this apparent paradox, we performed a cross-sectional study of a general population sample recruited in the Canary Islands, Spain (n=6729). We recorded altitude of residence, age, heart rate, blood pressure, body mass index, social class, physical activity, energy intake, alcohol intake, smoking habit, prevalence of type 2 diabetes mellitus and hypertension. In a subsample (n=903), we recorded serum concentration of cholesterol, triglycerides, glucose, C peptide, leptin, soluble leptin receptor (sObR), C-reactive protein, resistin, soluble CD40 ligand (sCD40L), and paraoxonase activity (PON), and we estimated insulin resistance and free leptin index. We found an inverse association between altitude and heart rate (p<0.001), leptin (p<0.001), free leptin index (p<0.001), resistin (p<0.001), and sCD40L (p<0.05) and a direct association between altitude and hypertension (odds ratio=1.29 for altitude >600 m; 95% confidence interval=1.03-1.62), glycemia (p<0.05), C peptide (p<0.001), insulin resistance (p<0.001), sObR (p<0.05), and PON (p<0.05). When social class was included in the multivariate model, the association with PON was no longer significant. In conclusion, individuals residing at moderate altitudes have a lower heart rate and lower serum concentration of total leptin, free leptin, and sCD40L. These differences may partially explain the lower mortality in these populations.

"Environmental hypertensionology" the effects of environmental factors on blood pressure in clinical practice and research

Blood pressure (BP) is affected by many environmental factors including ambient temperature, altitude, latitude, noise, and air pollutants. Given their pervasiveness, it is plausible that such factors may also have an impact on hypertension prevalence and control rates. Health care providers should be aware that the environment can play a significant role in altering BP. Although not among the established modifiable risk factors (eg, obesity) for hypertension, reducing exposures when pertinent should be considered to prevent or control hypertension. The authors provide a concise review of the evidence linking diverse environmental factors with BP and suggest an approach for incorporating this knowledge into clinical practice. The authors propose using the term environmental hypertensionology to refer to the study of the effects of environmental factors on BP in clinical and research settings.

Nervous system function during exercise in hypoxia

Aerobic exercise capacity decreases with exposure to hypoxia. This article focuses on the effects of hypoxia on nervous system function and the potential consequences for the exercising human. Emphasis is put on somatosensory muscle afferents due to their crucial role in the reflex inhibition of muscle activation and in cardiorespiratory reflex control during exercise. We review the evidence of hypoxia influences on muscle afferents and discuss important consequences for exercise performance. Efferent (motor) nerves are less affected at altitude and are thought to stay fairly functional even in severe levels of arterial hypoxemia. Altitude also alters autonomic nervous system functions, which are thought to play an important role in the regulation of cardiac output and ventilation. Finally, the consequences of hypoxia-induced cortical adaptations and dysfunctions are evaluated in terms of neurotransmitter turnover, brain electrical activity, and cortical excitability. Even though the cessation of exercise or the reduction of exercise intensity, when reaching maximum performance, implies reduced motor recruitment by the nervous system, the mechanisms that lead to the de-recruitment of active muscle are still not well understood. In moderate hypoxia, muscle afferents appear to play an important role, whereas in severe hypoxia brain oxygenation may play a more important role.