Impact of high altitude on echocardiographically determined cardiac morphology and function in patients with coronary artery disease and healthy controls

Differential diagnosis of chronic obstructive pulmonary disease and obesity hypoventilation syndrome in patients presenting with hypercapnic respiratory failure

PURPOSE

The differential diagnosis of chronic obstructive pulmonary disease (COPD) and obesity hypoventilation syndrome (OHS) is important to avoid misdiagnosis and mistreatment. This study aimed to compare the laboratory and clinical findings of these two diseases.

METHODS

Patients who presented with hypercapnic respiratory failure and were hospitalized for at least 5 days were included. The patients' clinical findings and laboratory parameters at admission were compared. The STOP-Bang questionnaire and Berlin Sleep Questionnaire were used to evaluate risk of sleep apnea, and dyspnea was assessed with the modified Borg scale. Improvements in clinical and blood gas parameters during follow-up were also evaluated.

RESULTS

Patients with OHS had higher diastolic blood pressure, STOP-Bang scores, frequency of high apnea risk according to the Berlin Sleep Questionnaire, and frequency of pulmonary hypertension (PH) when compared with the COPD group (p = 0.01, < 0.001, < 0.001, and < 0.001, respectively). Waist circumference, triglyceride level, and frequency of metabolic syndrome were also higher in the OHS group (p < 0.001 for all). High Berlin Sleep Questionnaire score and body mass index (BMI) were significant discriminators for OHS, while the presence of bronchial obstruction was a discriminator for COPD. Evaluation of these three parameters together enabled differential diagnosis in 85% of cases.

CONCLUSION

Patients with OHS who present with hypercapnic respiratory failure may be misdiagnosed as having COPD because of the similar clinical pictures. Clinicians should consider OHS in patients with high BMI, increased risk of sleep apnea, and no obstructive findings on physical examination.

Comparison of the Effects of Hemodialysis and Peritoneal Dialysis on Exhaled Nitric Oxide in Renal Replacement Therapy

BACKGROUND

Peritoneal dialysis (PD) and hemodialysis (HD) form the basis of renal replacement therapy (RRT) in patients with end-stage renal disease. Both methods have advantages, and in our study, we aimed to examine the effect of both methods on exhaled nitric oxide (FeNO) levels.

METHODS

Our study included RRT patients between 18 and 65 who our hospital's nephrology clinic followed up for at least 2 years. A total of 100 patients, 35 patients from both RRT groups and 30 healthy control groups, were included in our study. Echocardiography (ECHO) and FeNO measurements were performed.

RESULTS

In the comparison of the groups' mean pulmonary arterial pressure (PAP) and pre-RRT FeNO levels, it was observed that both levels were higher in HD patients compared to PD patients (p = 0.04, < 0.001, respectively). The control group observed that both predialysis and postdialysis FeNO levels in HD patients showed a statistically significant difference compared to the control group (p ≤ 0.001, 0.01, respectively). It was observed that mean arterial pressure (MAP) levels were higher in HD patients compared to PD patients before RRT (p = 0.01). FeNO positively correlated with age and gamma-glutamyl transferase (GGT) level (R = 0.542, p = 0.01, R = 0.629, p = 0.01, respectively).

CONCLUSION

FeNO is known as an essential indicator of oxidative stress and inflammation. The higher FeNO level in HD patients compared to PD and its positive correlation with oxidative stress markers such as GGT suggest that PD may be more suitable for the physiological structure.

Flying to high-altitude destinations

Every year millions of people fly to high-altitude destinations. They thereby expose themselves to specific high-altitude conditions. The hypoxic environment (low ambient oxygen availability) constitutes a major factor affecting health and well-being at high altitude. While the oxygen availability is already moderately reduced inside the aircraft cabin, this reduction becomes aggravated when leaving the plane at high-altitude destinations. Especially if not pre-acclimatized, the risk of suffering from high-altitude illnesses, e.g., acute mountain sickness, high-altitude cerebral or pulmonary edema, increases with the level of altitude. In addition, diminished oxygen availability impairs exercise tolerance, which not only limits physical activity at high altitude but may also provoke symptomatic exacerbation of pre-existing diseases. Moreover, the cold and dry ambient air and increased levels of solar radiation may contribute to adverse health effects at higher altitude. Thus, medical pre-examination and pre-flight advice, and proper preparation (pre-acclimatization, exercise training, and potentially adaptation of pharmacological regimes) are of utmost importance to reduce negative health impacts and frustrating travel experiences.

Cardiovascular physiology and pathophysiology at high altitude

Oxygen is vital for cellular metabolism; therefore, the hypoxic conditions encountered at high altitude affect all physiological functions. Acute hypoxia activates the adrenergic system and induces tachycardia, whereas hypoxic pulmonary vasoconstriction increases pulmonary artery pressure. After a few days of exposure to low oxygen concentrations, the autonomic nervous system adapts and tachycardia decreases, thereby protecting the myocardium against high energy consumption. Permanent exposure to high altitude induces erythropoiesis, which if excessive can be deleterious and lead to chronic mountain sickness, often associated with pulmonary hypertension and heart failure. Genetic factors might account for the variable prevalence of chronic mountain sickness, depending on the population and geographical region. Cardiovascular adaptations to hypoxia provide a remarkable model of the regulation of oxygen availability at the cellular and systemic levels. Rapid exposure to high altitude can have adverse effects in patients with cardiovascular diseases. However, intermittent, moderate hypoxia might be useful in the management of some cardiovascular disorders, such as coronary heart disease and heart failure. The aim of this Review is to help physicians to understand the cardiovascular responses to hypoxia and to outline some recommendations that they can give to patients with cardiovascular disease who wish to travel to high-altitude destinations.

Hypoxia and the Aging Cardiovascular System

Older individuals represent a growing population, in industrialized countries, particularly those with cardiovascular diseases, which remain the leading cause of death in western societies. Aging constitutes one of the largest risks for cardiovascular diseases. On the other hand, oxygen consumption is the foundation of cardiorespiratory fitness, which in turn is linearly related to mortality, quality of life and numerous morbidities. Therefore, hypoxia is a stressor that induces beneficial or harmful adaptations, depending on the dose. While severe hypoxia can exert detrimental effects, such as high-altitude illnesses, moderate and controlled oxygen exposure can potentially be used therapeutically. It can improve numerous pathological conditions, including vascular abnormalities, and potentially slows down the progression of various age-related disorders. Hypoxia can exert beneficial effects on inflammation, oxidative stress, mitochondrial functions, and cell survival, which are all increased with age and have been discussed as main promotors of aging. This narrative review discusses specificities of the aging cardiovascular system in hypoxia. It draws upon an extensive literature search on the effects of hypoxia/altitude interventions (acute, prolonged, or intermittent exposure) on the cardiovascular system in older individuals (over 50 years old). Special attention is directed toward the use of hypoxia exposure to improve cardiovascular health in older individuals.

Investigation of the need for computed tomography pulmonary angiography in the decision to discontinue treatment for pulmonary thromboembolism

BACKGROUND

Acute pulmonary thromboembolism (PTE) is an important cause of morbidity and mortality that can reduce quality of life due to long-term complications during and after treatment discontinuation.

OBJECTIVES

The aim of this study was to evaluate patients for these complications before discontinuing treatment and determine the necessity of computed tomography pulmonary angiography (CTPA) imaging.

METHODS

This retrospective study included 116 patients over the age of 18 who received anticoagulant treatment for at least 3 months and presented for treatment discontinuation to the Atatürk University Research Hospital Chest Diseases Outpatient Clinic between January 2015 and September 2019.

RESULTS

CTPA performed at treatment discontinuation showed complete thrombus resolution with treatment in 73 patients (62.9%). High pulmonary artery obstruction index (PAOI) at diagnosis was statistically associated with findings of residual or chronic thrombus on CTPA at treatment discontinuation (p = 0.001). In the differentiation of patients with residual/chronic thrombus and those with thrombus resolution, D-dimer at a cut-off value of 474 µg/L had 60% sensitivity and 70% specificity. At a cut-off value of 35.5 mmHg, mean pulmonary artery pressure on echocardiography had sensitivity and specificity of 72% and 77%, respectively. At a cut-off of 23.75, PAOI had sensitivity and specificity of 93% and 69%, respectively.

CONCLUSION

In addition to physical examination findings, D-dimer and echocardiography were guiding parameters in the evaluation of treatment discontinuation and thrombus resolution in patients presenting to the outpatient clinic for discontinuation of treatment for acute PTE. PAOI at diagnosis may be another important guiding parameter in addition to these examinations.

Right Ventricular Response to Acute Hypoxia Exposure: A Systematic Review

Background: Acute hypoxia exposure is associated with an elevation of pulmonary artery pressure (PAP), resulting in an increased hemodynamic load on the right ventricle (RV). In addition, hypoxia may exert direct effects on the RV. However, the RV responses to such challenges are not fully characterized. The aim of this systematic review was to describe the effects of acute hypoxia on the RV in healthy lowland adults.

Methods: We systematically reviewed PubMed and Web of Science and article references from 2005 until May 2021 for prospective studies evaluating echocardiographic RV function and morphology in healthy lowland adults at sea level and upon exposure to simulated altitude or high-altitude.

Results: We included 37 studies in this systematic review, 12 of which used simulated altitude and 25 were conducted in high-altitude field conditions. Eligible studies reported at least one of the RV variables, which were all based on transthoracic echocardiography assessing RV systolic and diastolic function and RV morphology. The design of these studies significantly differed in terms of mode of ascent to high-altitude, altitude level, duration of high-altitude stay, and timing of measurements. In the majority of the studies, echocardiographic examinations were performed within the first 10 days of high-altitude induction. Studies also differed widely by selectively reporting only a part of multiple RV parameters. Despite consistent increase in PAP documented in all studies, reports on the changes of RV function and morphology greatly differed between studies.

Conclusion: This systematic review revealed that the study reports on the effects of acute hypoxia on the RV are controversial and inconclusive. This may be the result of significantly different study designs, non-compliance with international guidelines on RV function assessment and limited statistical power due to small sample sizes. Moreover, the potential impact of other factors such as gender, age, ethnicity, physical activity, mode of ascent and environmental factors such as temperature and humidity on RV responses to hypoxia remained unexplored. Thus, this comprehensive overview will promote reproducible research with improved study designs and methods for the future large-scale prospective studies, which eventually may provide important insights into the RV response to acute hypoxia exposure.

[Heart Patients and Exposure to Altitude]

Overall, heart patients should be advised individually with respect to their tolerance of altitudes. However, the historical reflex that altitude 'per se' is bad for heart patients should become a thing of the past. Adequately treated and stable patients can usually go up to an altitude of 2500 m without any restrictions. Higher altitudes are also possible for a large number of patients, but may require an adaptation of the medication and further clarification. This is especially the case when physical work is to be performed at great heights.

Cardiac Acclimatization at High Altitude in Two Different Ethnicity Groups

Gaur, Priya, Meerim Sartmyrzaeva, Abdirashit Maripov, Kubatbek Muratali Uulu, Supriya Saini, Koushik Ray, Krishna Kishore, Almaz Akunov, Akpay Sarybaev, Bhuvnesh Kumar, Shashi Bala Singh, and Praveen Vats. Cardiac acclimatization at high altitude in two different ethnicity groups. High Alt Med Biol. 22:58-69, 2021. Introduction: High altitude (HA) exposure causes substantial increase in pulmonary artery pressure (PAP) and resistance. However, the effects of HA hypoxia exposure on cardiac function remain incompletely understood. Studies evaluating interethnic differences in cardiac functions in response to HA exposure are lacking. We aimed to compare the cardiac performance in Indian versus Kyrgyz healthy lowland subjects over the course of a 3-week HA exposure at 4,111 m. Methodology: Ten Indians and 20 Kyrgyz subjects were studied to assess cardiac acclimatization noninvasively by echocardiography in two different ethnic groups for 3 weeks of stay at HA. Pulmonary hemodynamics, right and left ventricular functions were evaluated at basal and on days 3, 7, 14, and 21 of HA exposure and on day 3 of deinduction. Results: HA exposure significantly increased PAP, pulmonary vascular resistance, cardiac output (CO), and heart rates (HRs) in both groups. Tricuspid regurgitant gradient increased significantly in both the group at day 3 versus basal; 38.9 mmHg (31.8, 42.9) versus 21.9 mmHg (19.5, 22.6) in Kyrgyz; and 34.1 mmHg (30.2, 38.5) versus 20.4 mmHg (19.7, 21.3) in Indians. HR increased significantly in Indians at day 3 and 7, whereas in Kyrgyz throughout exposure. CO increased significantly in both groups at day 3 versus basal with 5.9 L/min (5.5, 6.4) versus 5.1 L/min (4.4, 5.9) in Kyrgyz, and 5.7 L/min (5.56, 5.98) versus 4.9 L/min (4.1, 5.3) in Indians. Both groups exhibited preserved right ventricular diastolic and systolic functions at HAs. HA exposure changed the left ventricular diastolic parameters only in Kyrgyz subjects with impaired mitral inflow E/A, but not in Indian subjects. All cardiac changes induced at HAs have been recovered fully upon deinduction in both, except lateral-septal A', which remained low in Indians. Conclusion: Although pulmonary hemodynamics responses were similar in both groups, there were differences in cardiac functional parameters between the two in response to HA exposure that may be accounted to ethnic variation.

Clinical recommendations for high altitude exposure of individuals with pre-existing cardiovascular conditions: A joint statement by the European Society of Cardiology, the Council on Hypertension of the European Society of Cardiology, the European Society of Hypertension, the International Society of Mountain Medicine, the Italian Society of Hypertension and the Italian Society of Mountain Medicine

Take home figure

Tricuspid annular plane systolic excursion is preserved in young patients with pulmonary hypertension except when associated with repaired congenital heart disease

Aims

Tricuspid annular plane systolic excursion (TAPSE) is a measure of right ventricular (RV) longitudinal function that correlates with functional status and mortality in adults with pulmonary hypertension (PH). The diagnostic and predictive value of TAPSE in children with PH has not been fully examined. We aimed to define TAPSE across aetiologies of paediatric PH and assess the correlation between TAPSE and measures of disease severity.

Methods and results

TAPSE measurements were obtained in 84 children and young adults undergoing treatment for PH and 315 healthy children to establish z-scores at moderate altitude for comparison. The relationships between TAPSE and echocardiographic, biomarker, and functional measures of disease severity between aetiologies were assessed. TAPSE z-scores in PH patients with congenital heart disease (CHD) repaired with open cardiac surgery (n = 20, mean -2.73) were significantly decreased compared with normal children and patients with other aetiologies of PH (P < 0.001) but did not reflect poorer clinical status. TAPSE z-scores in children with idiopathic PH (n = 29, -0.41), unrepaired CHD (n = 11, -0.1), and PH related to systemic disease (n = 14, -0.39) were not different from normal. TAPSE correlated modestly with brain natriuretic peptide, echocardiographic function parameters, and functional class except in patients with repaired CHD.

Conclusion

Children with PH maintain normal TAPSE values early except when associated with repaired CHD. Superior RV adaptation to high afterload in children compared with adults may account for this finding. Reduced TAPSE after repair of CHD does not correlate with functional status and may reflect post-operative changes rather than poor function primarily due to PH.

Electrocardiographic changes during exercise in acute hypoxia and susceptibility to severe high-altitude illnesses

BACKGROUND

The goals of this study were to compare ECG at moderate exercise in normoxia and hypoxia at the same heart rate, to provide evidence of independent predictors of hypoxia-induced ECG changes, and to evaluate ECG risk factors of severe high-altitude illness.

METHODS AND RESULTS

A total of 456 subjects performed a 20-minute hypoxia exercise test with continuous recording of ECG and physiological measurements before a sojourn above 4000 m. Hypoxia did not induce any conduction disorder, arrhythmias, or change in QRS axis. The amplitude of the P wave in V1 was lower in hypoxia than in normoxia. The amplitudes of the R, S, and T waves and the Sokolow index decreased in hypoxia. Under hypoxia, the amplitude of the ST segment decreased in II and V6 and increased in V1, the ST slope rose in V5 and V6, and the J point was lower in II, V5, and V6. Multivariate regression of hypoxic/normoxic ratios of electrophysiological parameters and clinical characteristics showed a correlation between the decrease in Sokolow index and T-wave amplitude in V5 with desaturation at exercise. Trained status and low body mass index were associated with a smaller decrease in T-wave amplitude in V5 and V6. Comparison of ECG between subjects suffering or not suffering from severe high-altitude illness failed to show any difference.

CONCLUSIONS

During a hypoxia exercise test, a dose-dependent hypoxia-induced decrease in the amplitude of the P/QRS/T waves was observed. No standard ECG characteristic predicted the risk of developing severe high-altitude illness. Further studies are required to clarify the cause of these electric changes and their potential predictive role in cardiac events.

Physiology in Medicine: Acute altitude exposure in patients with pulmonary and cardiovascular disease

Travel is more affordable and improved high-altitude airports, railways, and roads allow rapid access to altitude destinations without acclimatization. The physiology of exposure to altitude has been extensively described in healthy individuals; however, there is a paucity of data pertaining to those who have reduced reserve. This Physiology in Medicine article discusses the physiological considerations relevant to the safe travel to altitude and by commercial aircraft in patients with pulmonary and/or cardiac disease.

Supplemental oxygen attenuates the increase in wound bacterial growth during simulated aeromedical evacuation in goats

BACKGROUND

Bacterial growth in soft tissue and open fractures is a known risk factor for tissue loss and complications in contaminated musculoskeletal wounds. Current care for battlefield casualties with soft tissue and musculoskeletal wounds includes tactical and strategic aeromedical evacuation (AE). This exposes patients to a hypobaric, hypoxic environment. In this study, we sought to determine whether exposure to AE alters bacterial growth in contaminated complex musculoskeletal wounds and whether supplemental oxygen had any effect on wound infections during simulated AE.

METHODS

A caprine model of a contaminated complex musculoskeletal wound was used. Complex musculoskeletal wounds were created and inoculated with bioluminescent Pseudomonas aeruginosa. Goats were divided into three experimental groups: ground control, simulated AE, and simulated AE with supplemental oxygen. Simulated AE was induced in a hypobaric chamber pressurized to 8,800 feet for 7 hours. Bacterial luminescence was measured using a photon counting camera at three time points: preflight (20 hours postsurgery), postflight (7 hours from preflight and 27 hours postsurgery), and necropsy (24 hours from preflight and 44 hours postsurgery).

RESULTS

There was a significant increase in bacterial growth in the AE group compared with the ground control group measured postflight and at necropsy. Simulated AE induced hypoxia with oxygen saturation less than 93%. Supplemental oxygen corrected the hypoxia and significantly reduced bacterial growth in wounds at necropsy.

CONCLUSIONS

Hypoxia induced during simulated AE enhances bacterial growth in complex musculoskeletal wounds which can be prevented with the application of supplemental oxygen to the host.

Occupational health of miners at altitude: adverse health effects, toxic exposures, pre-placement screening, acclimatization, and worker surveillance

CONTEXT

Mining operations conducted at high altitudes provide health challenges for workers as well as for medical personnel.

OBJECTIVE

To review the literature regarding adverse health effects and toxic exposures that may be associated with mining operations conducted at altitude and to discuss pre-placement screening, acclimatization issues, and on-site surveillance strategies.

METHODS

We used the Ovid ( http://ovidsp.tx.ovid.com ) search engine to conduct a MEDLINE search for "coal mining" or "mining" and "altitude sickness" or "altitude" and a second MEDLINE search for "occupational diseases" and "altitude sickness" or "altitude." The search identified 97 articles of which 76 were relevant. In addition, the references of these 76 articles were manually reviewed for relevant articles. CARDIOVASCULAR EFFECTS: High altitude is associated with increased sympathetic tone that may result in elevated blood pressure, particularly in workers with pre-existing hypertension. Workers with a history of coronary artery disease experience ischemia at lower work rates at high altitude, while those with a history of congestive heart failure have decreased exercise tolerance at high altitude as compared to healthy controls and are at higher risk of suffering an exacerbation of their heart failure. PULMONARY EFFECTS: High altitude is associated with various adverse pulmonary effects, including high-altitude pulmonary edema, pulmonary hypertension, subacute mountain sickness, and chronic mountain sickness. Mining at altitude has been reported to accelerate silicosis and other pneumoconioses. Miners with pre-existing pneumoconioses may experience an exacerbation of their condition at altitude. Persons traveling to high altitude have a higher incidence of Cheyne-Stokes respiration while sleeping than do persons native to high altitude. Obesity increases the risk of pulmonary hypertension, acute mountain sickness, and sleep-disordered breathing. NEUROLOGICAL EFFECTS: The most common adverse neurological effect of high altitude is acute mountain sickness, while the most severe adverse neurological effect is high-altitude cerebral edema. Poor sleep quality and sleep-disordered breathing may contribute to daytime sleepiness and impaired cognitive performance that could potentially result in workplace injuries, particularly in miners who are already at increased risk of suffering unintentional workplace injuries. OPHTHALMOLOGICAL EFFECTS: Adverse ophthalmological effects include increased exposure to ultraviolet light and xerophthalmia, which may be further exacerbated by occupational dust exposure. RENAL EFFECTS: High altitude is associated with a protective effect in patients with renal disease, although it is unknown how this would affect miners with a history of chronic renal disease from exposure to silica and other renal toxicants. HEMATOLOGICAL EFFECTS: Advanced age increases the risk of erythrocytosis and chronic mountain sickness in miners. Thrombotic and thromboembolic events are also more common at high altitude. MUSCULOSKELETAL EFFECTS: Miners are at increased risk for low back pain due to occupational factors, and the easy fatigue at altitude has been reported to further predispose workers to this disorder. TOXIC EXPOSURES: Diesel emissions at altitude contain more carbon monoxide due to increased incomplete combustion of fuel. In addition, a given partial pressure of carbon monoxide at altitude will result in a larger percentage of carboxyhemoglobin at altitude. Miners with a diagnosis of chronic obstructive pulmonary disease may be at higher risk for morbidity from exposure to diesel exhaust at altitude.

CONCLUSIONS

Both mining and work at altitude have independently been associated with a number of adverse health effects, although the combined effect of mining activities and high altitude has not been adequately studied. Careful selection of workers, appropriate acclimatization, and limited on-site surveillance can help control most health risks. Further research is necessary to more completely understand the risks of mining at altitude and delineate what characteristics of potential employees put them at risk for altitude-related morbidity or mortality.