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Background Recent studies have reported that obstructive sleep apnea (OSA) patients present alterations in right ventricular (RV) structure and function. However, large randomized controlled trials evaluating the impact of OSA on the right ventricle are lacking. Methods A comprehensive electronic database (PubMed, Web of Science, and Google Scholar) and reference search up to October 30, 2016, was performed. A systematic review and meta-analysis were performed to assess RV structure and function in OSA patients based on conventional echocardiography and tissue Doppler imaging. Results Twenty-five studies with 1,503 OSA patients and 796 controls were included in this study. OSA patients exhibited an increase in RV internal diameter (weighted mean difference (WMD) (95% confidence intervals (CIs)) 2.49 (1.62 to 3.37); p = 0.000) and RV wall thickness (WMD (95% CIs) 0.82 (0.51 to 1.13); p = 0.000). Furthermore, OSA patients had a significantly elevated RV myocardial performance index (WMD (95% CI) 0.08 (0.06 to 0.10); p = 0.000), decreased RV S' (WMD (95% CI) −0.95 (−1.59 to −0.32); p = 0.003), tricuspid annular plane systolic excursion (WMD (95% CI) −1.76 (−2.73 to −0.78); p = 0.000), and RV fractional area change (WMD (95% CI) −3.16 (−5.60 to −0.73); p = 0.011). Conclusion OSA patients display RV dilatation, increased wall thickening, and altered RV function.

Chronic high altitude hypoxia leads to an increase in red cell numbers and hemoglobin concentration. However, the effects of long-term intermittent hypoxia on hemoglobin concentration have not fully been studied. The aim of this study was to evaluate hemoglobin levels in workers commuting between an elevation of 3,800 m (2-week working shift) and lowland below 1,700 m (2 weeks of holiday). A total of 266 healthy males, aged from 20 to 69 years (mean age 45.9 ± 0.6 years), were included into this study. The duration of intermittent high altitude exposure ranged from 0 to 21 years. Any cardiac or pulmonary disorder was excluded during annual check-ups including clinical examination, clinical lab work (blood cell count, urine analysis, and biochemistry), ECG, echocardiography, and pulmonary function tests. The mean hemoglobin level in workers was 16.2 ± 0.11 g/dL. Univariate linear regression revealed an association of the hemoglobin levels with the years of exposure. Hemoglobin levels increased 0.068 g/dL [95% CI: 0.037 to 0.099, p < 0.001] for every year of intermittent high altitude exposure. Further, after adjusting for other confounding variables (age, living at low or moderate altitude, body mass index, and occupation) using multivariable regression analysis, the magnitude of hemoglobin level changes decreased, but remained statistically significant: 0.046 g/dL [95% CI: 0.005 to 0.086, p < 0.05]. Besides that, a weak linear relationship between hemoglobin levels and body mass index was revealed, which was independent of the years of exposure to high altitude (0.065 g/dL [95% CI: 0.006 to 0.124, p < 0.05]). We concluded that hemoglobin levels have a linear relationship with the exposure years spent in intermittent hypoxia and body mass index.

High altitude (HA) presents inhospitable environmental conditions that adversely affects human physiology and metabolism. Changes in physiological functions are reported during high altitude exposure, but the changes vary with physical state, culture habits, geographical locations, and genetic variation of individual. The present study was carried out to explore the variation in acclimatization pattern of two different ethnic groups in relation to cardiovascular functions, lipid profile and body composition. The study was carried out on 30 human volunteers (20 Indian and 10 Kyrgyz) initially at Bishkek for basal recording and on day 3, 7, 14, and 21 of high altitude (3200 m) induction and again on day 3 of de-induction. On altitude exposure significant decrease in body weight was observed both in Indian (day 14, p<0.001) and Kyrgyz (day 3, p<0.01) subjects. Decreased levels of total body water, extra cellular and intra cellular body water were also observed in both the groups. Significant reduction in body mass index (p<0.01), fat free mass (p<0.01), body cell mass (p<0.01) and body volume (p<0.01) was also observed in Kyrgyz subjects, whereas in Indian subjects the changes were not significant in these variables on high altitude exposure. Diastolic blood pressure and heart rate increased significantly on day 3 (p<0.001 and p<0.01, respectively) of induction in Indian subjects; whereas in Kyrgyz significant increase was observed on day 14 (p<0.05) in both the cases. High density lipoprotein (HDL) cholesterol levels increased significantly on day 7 of HA exposure in both the groups. Results indicate that the Indian and Kyrgyz groups report differently, in relation to changes in cardiovascular functions, lipid profiles, and body composition, when exposed to HA. The difference observed in acclimatization pattern in the two groups may be due to ethnic/genetic variation of two populations.

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