Prevalence of pulmonary hypertension and its association with respiratory disturbances in obese patients living at moderately high altitude

Obesity: An Impact with Cardiovascular and Cerebrovascular Diseases

The authors sought to correlate the complex sequel of obesity with various parameters known to develop metabolic syndrome viz. insulin resistance, dyslipidemia, hypertension etc., as these anomalies are linked to vascular atherosclerosis and outbreak of cardiovascular and cerebrovascular diseases.  A comprehensive online survey using MEDLINE, Scopus, PubMed and Google Scholar was conducted for relevant journals from 1970 till present time (2023) with key search terms like: 'obesity', 'leptin', type-2 diabetes', 'atherosclerosis', 'cardiovascular and cerebrovascular diseases'. The findings of the reports were compared and correlated. The information was then collated for developing this review. Reports showed that in human obesity, hyper-leptinemia could induce hyperglycemia, which in turn templates hypercholesterolemia. Persisting hypercholesterolemia over a period of time may en-route atherosclerosis in blood vessels. Thus obesity has been considered as a template for originating hyperglycemia, hypercholesterolemia and outbreak of vascular atherogenesis or in other words, obesity in long run can trigger atherosclerosis and its related disorders e.g. heart attack and stroke. Literature survey shows that primarily, co-morbidities of human obesity start with leptin and insulin resistance and then multiplies with metabolic irregularities to an extreme that results in pathogenesis of heart attack and stroke. Atherosclerosis associated cardiovascular and cerebrovascular events are independent risks of obese subjects and particularly in the cases of persisting obesity.

The Association of Body Mass Index With the Risk of Pulmonary Hypertension in Adults: A Systematic Review and Meta-Analysis of Observational Studies

Backgrounds

Findings regarding the association of body mass index (BMI) with pulmonary hypertension (PH) are conflicting, and there is no systematic review and meta-analysis to summarize the results. Therefore, the purpose of this systematic review and meta-analysis is to assess this relationship.

Methods

To detect the relevant articles, PubMed, Scopus, and Google Scholar were searched until February 2021. Included essays were pooled using a random-effect model. Cochrane Q-test and I²-test was applied to assess between-study heterogeneity.

Results

Fourteen articles (eight cross-sectional and four cohort studies) were included in the meta-analysis. The meta-analysis of comparing highest vs. lowest BMI categories did not indicate a significant association between BMI and PH (Summary Effect Estimate: 1.59 (95% CI: 0.50, 5.07, I² = 92.3). Furthermore, The summary risk estimate for a one-unit increment in BMI was 1.01 (95 % CI: 0.99, 1.03), with high heterogeneity, I² = 73.5 %, P heterogeneity <0.001). Subgroup analysis showed significant positive association between BMI and the risk of PH in studies controlled for cofounders, and studies with higher sample sizes (≥2,000).

Conclusion

There is no significant association between BMI and risk of pulmonary hypertension. Further studies are required to confirm these findings.

Evaluation of right ventricular performance and impact of continuous positive airway pressure therapy in patients with obstructive sleep apnea living at high altitude

Obstructive sleep apnea syndrome (OSAS) can lead to alterations in right ventricular (RV) performance and pulmonary vascular haemodynamics. Additionally, altitude-related hypoxia is associated with pulmonary vasoconstriction, and the effect of high-altitude on the pulmonary circulation in OSAS patients can be further altered. We sought to assess alterations in RV morphology and function in OSAS patients living at high altitude by way of 2-dimensional speckle tracking echocardiography (2D-STE), real-time 3- dimensional echocardiography (RT-3DE) and cardiac biomarkers. We also evaluate the impact of continuous positive airway pressure (CPAP) treatment on RV performance. Seventy-one patients with newly diagnosed OSAS and thirty-one controls were included in this study. All individuals were assessed for cardiac biomarkers as well as underwent 2D-STE and RT-3DE. Forty-five OSAS patients underwent CPAP therapy for at least 24 weeks and were studied before and after CPAP treatment. RT-3DE was used to measure RV volume, and calculate RV 3D ejection fraction (3D RVEF). Peak systolic strain was determined. Cardiac biomarkers, including C-reactive protein (CRP), N-terminal pro-B-type natriuretic peptide, and cardiac troponin T were also measured. Right atrium volume index, RV volume, RV volume index, systolic pulmonary artery pressure (sPAP), pulmonary vascular resistance (PVR) and level of serum CRP were significantly higher in OSAS group, while OSAS patients showed lower 3D RVEF and RV longitudinal strains. Compared to the patients with sPAP < 40 mmHg, RV longitudinal strains in patients with sPAP ≥ 40 mmHg were lower. Both RV global longitudinal strain and sPAP were associated with apnea–hypopnea index. Patients treated with 6 months of CPAP therapy had significant improvement in RV geometry and performance. RV structural abnormalities and RV function impairments were observed in OSAS patients living at moderate high altitude compared to control highlanders. The reversibility of these changes after application of CPAP were further confirmed.

Involvement of overweight and lipid metabolism in the development of pulmonary hypertension under conditions of chronic intermittent hypoxia

There is growing evidence that exposure to hypoxia, regardless of the source, elicits several metabolic responses in individuals. These responses are constitutive and are usually observed under hypoxia but vary according to the type of exposure. The aim of this review was to describe the involvement of obesity and lipid metabolism in the development of high-altitude pulmonary hypertension and in the development of acute mountain sickness under chronic intermittent hypoxia. Overweight or obesity, which are common in individuals with long-term chronic intermittent hypoxia exposure (high-altitude miners, shift workers, and soldiers), are thought to play a major role in the development of acute mountain sickness and high-altitude pulmonary hypertension. This association may be rooted in the interactions between obesity-related metabolic and physical alterations, such as increased waist circumference and neck circumference, among others, which lead to critical ventilation impairments; these impairments aggravate hypoxemia at high altitude, thereby triggering high-altitude diseases. Overweight and obesity are strongly associated with higher mean pulmonary artery pressure in the context of long-term chronic intermittent hypoxia. Remarkably, de novo synthesis of triglycerides by the sterol regulatory element-binding protein-1c pathway has been demonstrated, mainly due to the upregulation of stearoyl-CoA desaturase-1, which is also associated with the same outcomes. Therefore, overweight, obesity, and other metabolic conditions may hinder proper acclimatization. The involved mechanisms include respiratory impairment, alteration of the nitric oxide pathways, inflammatory status, reactive oxygen species imbalance, and other metabolic changes; however, further studies are required.

Influence of gender in monocrotaline and chronic hypoxia induced pulmonary hypertension in obese rats and mice

BACKGROUND

Obesity and pulmonary hypertension (PH) share common characteristics, such as augmented inflammation and oxidative stress. However, the exact role of obesity in the pathology of PH is largely uninvestigated. Therefore, we have hypothesized that in the context of obesity the gender difference may have influence on development of PH in animal models of this disease.

METHODS

Animal experiments were conducted in monocrotaline (MCT) and chronic hypoxia (HOX) models of PH. Lean and obese Zucker rats or B6 mice of both genders were used for MCT or HOX models, respectively. Echocardiography, hemodynamic measurements, histology and immuno-histochemistry were performed to analyze various parameters, such as right ventricular function and hypertrophy, hemodynamics, pulmonary vascular remodeling and lung inflammation.

RESULTS

Both lean and obese male and female Zucker rats developed PH after a single MCT injection. However, negligible differences were seen between lean and obese male rats in terms of PH severity at the end stage of disease. Conversely, a more prominent and severe PH was observed in obese female rats compared to their lean counterparts. In contrast, HOX induced PH in lean and obese, male and female mice did not show any apparent differences.

CONCLUSION

Gender influences PH severity in obese MCT-injected rats. It is also an important factor associated with altered inflammation. However, further research is necessary to investigate and reveal the underlying mechanisms.

Obesity as a Conditioning Factor for High-Altitude Diseases

Obesity, a worldwide epidemic, has become a major health burden because it is usually accompanied by an increased risk for insulin resistance, diabetes, hypertension, cardiovascular diseases, and even some kinds of cancer. It also results in associated increases in healthcare expenditures and labor and economic consequences. There are also other fields of medicine and biology where obesity or being overweight play a major role, such as high-altitude illnesses (acute mountain sickness, hypoxic pulmonary hypertension, and chronic mountain sickness), where an increasing relationship among these two morbid statuses has been demonstrated. This association could be rooted in the interactions between obesity-related metabolic alterations and critical ventilation impairments due to obesity, which would aggravate hypobaric hypoxia at high altitudes, leading to hypoxemia, which is a trigger for developing high-altitude diseases. This review examines the current literature to support the idea that obesity or overweight could be major conditioning factors at high altitude.

Right ventricular geometry and mechanics in patients with obstructive sleep apnea living at high altitude

PURPOSE

Repetitive obstruction of larynx during sleep can lead to daytime pulmonary hypertension and alterations in right ventricular morphology and function in a small fraction of obstructive sleep apnea syndrome (OSAS) patients. Environmental effects, particularly high altitude, can modify the effects of OSAS on pulmonary circulation, since altitude-related hypoxia is related with pulmonary vasoconstriction. This potential interaction, however, was not investigated in previous studies.

METHODS

A total of 41 newly diagnosed OSAS patients were included in this study after pre-enrolment screening. Two-dimensional, three-dimensional, and Doppler echocardiographic data were collected after polysomnographic verification of OSAS. Three-dimensional echocardiograms were analyzed to calculate right ventricular volumes, volume indices, and ejection fraction.

RESULTS

Systolic pulmonary artery pressure (38.35 ± 8.60 vs. 30.94 ± 6.47 mmHg; p = 0.002), pulmonary acceleration time (118.36 ± 16.36 vs. 103.13 ± 18.42 ms; p = 0.001), right ventricle (RV) end-diastolic volume index (48.15 ± 11.48 vs. 41.48 ± 6.45 ml; p = 0.009), and RV end-systolic volume index (26.50 ± 8.11 vs. 22.15 ± 3.85; p = 0.01) were significantly higher in OSAS patients, with similar RV ejection fraction (EF) between groups. No significant differences were noted in other two-dimensional, Doppler or speckle-tracking strain, measurements. Both RVEF and pulmonary acceleration time were predictors of disease severity.

CONCLUSIONS

A greater degree of RV structural remodeling and higher systolic pulmonary pressure were observed in OSAS patients living at high altitude compared to healthy highlanders. The reversibility of these alterations with treatment remains to be studied.

Relationship of obesity and insulin resistance with the cerebrovascular reactivity: a case control study

Background

Obesity is associated with increased risk for stroke. The breath-holding index (BHI) is a measure of vasomotor reactivity of the brain which can be measured with the transcranial Doppler (TCD). We aim to evaluate obesity as an independent factor for altered cerebrovascular reactivity.

Methods

Cerebrovascular hemodynamics (mean flow velocities MFV, pulsatility index, PI, resistance index, RI, and BHI) was determined in 85 non-obese (Body Mass Index, BMI ≤27 kg/m²) and 85 obese subjects (BMI ≥35 kg/m²) without diabetes mellitus and hypertension. Anthropometric and metabolic variables, and scores to detect risk for obstructive sleep apnea (OSA) were analyzed for their association with the cerebrovascular reactivity.

Results

The BHI was significantly lower in subjects with obesity according to BMI and in subjects with abdominal obesity, but the PI and RI were not different between groups. There was a linear association between the BMI, the HOMA-IR, the Matsuda index, the waist circumference, and the neck circumference, with the cerebrovascular reactivity. After adjusting for insulin resistance, neck circumference, and abdominal circumference, obesity according to BMI was negatively correlated with the cerebrovascular reactivity.

Conclusions

We found a diminished vasomotor reactivity in individuals with obesity which was not explained by the presence of insulin resistance.

Obesity and pulmonary hypertension: a review of pathophysiologic mechanisms

Pulmonary hypertension (PH) is a potentially life-threatening condition arising from a wide variety of pathophysiologic mechanisms. Effective treatment requires a systematic diagnostic approach to identify all reversible mechanisms. Many of these mechanisms are relevant to those afflicted with obesity. The unique mechanisms of PH in the obese include obstructive sleep apnea, obesity hypoventilation syndrome, anorexigen use, cardiomyopathy of obesity, and pulmonary thromboembolic disease. Novel mechanisms of PH in the obese include endothelial dysfunction and hyperuricemia. A wide range of effective therapies exist to mitigate the disability of PH in the obese.

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.

Lung disease at high altitude

Large numbers of people travel to high altitudes, entering an environment of hypobaric hypoxia. Exposure to low oxygen tension leads to a series of important physiologic responses that allow individuals to tolerate these hypoxic conditions. However, in some cases hypoxia triggers maladaptive responses that lead to various forms of acute and chronic high altitude illness, such as high-altitude pulmonary edema or chronic mountain sickness. Because the respiratory system plays a critical role in these adaptive and maladaptive responses, patients with underlying lung disease may be at increased risk for complications in this environment and warrant careful evaluation before any planned sojourn to higher altitudes. In this review, we describe respiratory disorders that occur with both acute and chronic exposures to high altitudes. These disorders may occur in any individual who ascends to high altitude, regardless of his/her baseline pulmonary status. We then consider the safety of high-altitude travel in patients with various forms of underlying lung disease. The available data regarding how these patients fare in hypoxic conditions are reviewed, and recommendations are provided for management prior to and during the planned sojourn.

Obesity and obesity-initiated metabolic syndrome: mechanistic links to chronic kidney disease

There is an epidemic of obesity and the metabolic syndrome in the United States and across the world. Both entities are associated with high mortality, mainly as a result of cardiovascular disease. The epidemic of obesity has been paralleled by an increase in the incidence of chronic kidney disease (CKD). Several recent epidemiologic studies have shown that obesity and the metabolic syndrome are independent predictors of CKD. In addition to diabetes and hypertension, several other mechanisms have been postulated to initiate and maintain kidney injury in patients with obesity and the metabolic syndrome. This article reviews the recent epidemiologic data linking obesity and the metabolic syndrome to CKD and summarizes the potential mechanisms of renal injury in this setting, with a focus on the role of inflammation, lipotoxicity, and hemodynamic factors. Potential preventive and therapeutic modalities based on the limited evidence available are discussed.

Perianesthesia respiratory care of the bariatric patient

Our nation's obesity problem has reached epidemic proportions and is only projected to worsen. The morbidly obese patient is at risk for experiencing a multitude of health-related conditions. Morbidly obese patients are presenting for surgery at an increasing rate, especially with the growing popularity of weight-loss surgery. Therefore the perianesthesia nurse has to remain informed of optimal care strategies for this sometimes challenging population. The obese patient presents with distinct respiratory care considerations of which the perianesthesia nurse must be knowledgeable. This review article will specifically focus on the respiratory care of the bariatric patient presenting for surgery.

Comparative physiology of hypoxic pulmonary hypertension: historical clues from brisket disease

Some of the most valuable contributions to science have come about serendipitously, and, in 1913, when George Glover and Issac Newsom were commissioned by Colorado cattle ranchers to study high mountain disease, there was no way to anticipate the tremendous impact they would have on the study of high-altitude cardiopulmonary physiology. It was through the study of this agricultural malady that the correlation between chronic hypoxia, pulmonary hypertension, medial hypertrophy of the small pulmonary arteries, and right ventricular (RV) hypertrophy was recognized. The amount of vascular smooth muscle comprising the medial layer of pulmonary arteries varies significantly across species and can be used to predict the magnitude of pulmonary hypertension and RV hypertrophy elicited in response to chronic hypoxia. Within species, age and gender both significantly influence the severity of chronic hypoxic pulmonary hypertension and RV hypertrophy. However, despite all that we now know about hypoxic pulmonary hypertension, the specific mechanism(s) that differentiate the hypo- from the hyperresponder have yet to be elucidated. Adventitial fibroblast differentiation, circulating vascular progenitor cells, the presence or absence of specific vascular smooth muscle phenotypes, the upregulation or downregulation of vasoactive mediators, splice variants of oxygen-sensitive transcription factors, upregulation of growth factors, Ca(2+) sensitization, and/or the Rho/Rho-kinases signaling cascade could all potentially play a role in determining the extent of the vascular response to hypoxia within a species. Understanding the mechanisms that determine why some people, as well as some animals, exhibit a marked susceptibility to hypoxia is an important endeavor with far-reaching implications.