Elevated pulmonary artery pressure and brain natriuretic peptide in high altitude pulmonary edema susceptible non-mountaineers.

Exaggerated pulmonary pressor response to hypoxia is a pathgonomic feature observed in high altitude pulmonary edema (HAPE) susceptible mountaineers. It was investigated whether measurement of basal pulmonary artery pressure (Ppa) and brain natriuretic peptide (BNP) could improve identification of HAPE susceptible subjects in a non-mountaineer population. We studied BNP levels, baseline hemodynamics and the response to hypoxia (FIo2 = 0.12 for 30 min duration at sea level) in 11 HAPE resistant (no past history of HAPE, Control) and 11 HAPE susceptible (past history of HAPE, HAPE-S) subjects. Baseline Ppa (19.31 ± 3.63 vs 15.68 ± 2.79 mm Hg, p < 0.05) and plasma BNP levels (52.39 ± 32.9 vs 15.05 ± 9.6 pg/ml, p < 0.05) were high and stroke volume was less (p < 0.05) in HAPE-S subjects compared to control. Acute hypoxia produced an exaggerated increase in heart rate (p < 0.05), mean arterial pressure (p < 0.05) and Ppa (28.2 ± 5.8 vs 19.33 ± 3.74 mm Hg, p < 0.05) and fall in peripheral oxygen saturation (p < 0.05) in HAPE-S compared to control. Receiver operating characteristic (ROC) curves showed that Ppa response to acute hypoxia was the best variable to identify HAPE susceptibility (AUC 0.92) but BNP levels provided comparable information (AUC 0.85). BNP levels are easy to determine and may represent an important marker for the determination of HAPE susceptibility.

Long-term stay at low altitude (1,200 m) promotes better hypoxia adaptation and performance.

Acute exposure to high altitude hypoxia is known to decrease physical performance. The exercise performance increases during moderate altitude training (2000-3000 m) but benefits are overshadowed by adverse effect associated with hypoxia. Therefore, the study was designed to address whether low altitude of 1200 m could increase exercise performance without any adverse effects and a correlation with stay period (stay > 6 month) was optimized. In the present study residents of lower altitude (1200 m altitude) (LA) and sea level (SL) residents were subjected to sub-maximal exercise test and their exercise response in terms of post-exercise heart rate and change in oxygen saturation was compared. Post-exercise peak heart rate (129.89 ± 13.42 vs 146.00 ± 11.81, p < 0.05) was significantly lower and arterial oxygen saturation (SpO2) after exercise had a significant fall (95.3 ± 2.26% vs 98 ± 0% p < 0.001) in LA residents. The hematological parameters like hemoglobin (Hb) and hematocrit (Hct) taken as markers of physiological adaptation, were also found to be significantly higher in LA as compared to SL residents (Hb 16.13 ± 0.70 vs 14.2 ± 0.87, p < 0.001 and Hct 47.4 ± ?2.08 vs 44.0 ± ?0.72, p <0.001). Overall, the study highlights that physiological adaptation at 1200 m results into a better exercise response and hematological benefit compared to sea level residents.

Prevalence of dry eye at high altitude: a case controlled comparative study.

High altitude is associated with physiological as well as pathological changes in the eye related to adverse environmental conditions that result in increased tear evaporation and contribute to a higher incidence of dry eye in these regions. We aimed to study the difference in prevalence of dry eye at high altitude and at low altitude. The prevalence of dry eye among the natives and the army soldiers who were recently posted at high altitude was also studied and compared. 200 adults above 20 years of age were enrolled. 100 subjects were recruited at a high altitude region (study group), of which 50 were native Ladakhis and 50 were soldiers recently posted at Leh, Ladakh, India (height; 3300 m above sea level; temperature: 18 degrees C to 24 degrees C). 100 subjects, age and sex matched, were screened at a low altitude region, New Delhi, India (218 m above sea level; temperature: 19 degrees C to 24 degrees C) to serve as the control group. Prevalence of dry eye was assessed through standard questionnaires (McMonnies' Questionnaire (MMI), Ocular Surface Disease Index Questionnaire (OSDI), and Schirmer's basic secretion test. On the basis of the parameters studied (symptoms, MMI, OSDI and Schirmer's test), dry eye was diagnosed in 20% of subjects screened at high altitude and in 9% of subjects in the control group screened at low altitude. In the study group, the prevalence of dry eye was significantly higher amongst the native population (54%) than in the army soldiers who were recently posted at that region (26%). The difference was statistically significant (p<0.005). In conclusion, dry eye is more common at high altitude, particularly in the native population. Awareness among people residing at high altitude and the treating medical personnel needs to be created for early detection and treatment of dry eye to prevent vision-threatening complications.