Arterial stiffness and endothelial dysfunction at high altitude

Currently, pulmonary vascular endothelial dysfunction is reported to be one of the pathogenic mechanisms of pulmonary hypertension, including high-altitude pulmonary hypertension. However, direct assessment of pulmonary vascular endothelium function is possible only by using complicated invasive methods, which are not always available even in specialized centers. Systemic vascular endothelial function assessment with a noninvasive photoplethysmographic method in combination with saliva nitric oxide level measurement is a fast and easily reproducible test that may indirectly indicate the development of pulmonary vascular endothelial dysfunction and, as a consequence, pulmonary hypertension. The aim of the study was to evaluate arterial stiffness and endothelial function in healthy volunteers at low (760 m) and high altitudes (3,600 m above sea level). Methods. Healthy volunteers ( n = 140: 47 men, 93 women; average age – 22.53 ± 2.09 years) took part in the observational longitudinal two-stage prospective study. At each of the two consecutive stages, at low and high altitudes, arterial Stiffness (SI) and vascular Reflexion (RI) index were measured using a noninvasive photoplethysmographic method, the level of nitric oxide (NO) in saliva by colorimetric method, and hemodynamics of the pulmonary circulation by echocardiography. The statistical analysis of the study findings was carried out using the SPSS Statistics 20 program. Results. At low altitude, none of the participants showed any disorders of pulmonary hemodynamics, arterial SI and RI, or endogenous NO. During the first 2 days at high altitude, a transient increase of mPAP to more than 20 mmHg was developed ( p < 0.05) in 29,7% participants, which was accompanied by a statistically significant increase in the SI (on day 1) and RI (on day 1 and 2) values. The opposite changes were observed in the endogenous NO level, which showed a decrease on the first day at high altitude ( p < 0.05). Conclusion. Some healthy volunteers developed a transient increase in mPAP at high altitude. This is accompanied by a statistically significant increase in SI and RI and a statistically significant decrease in endogenous NO levels, which may indicate the development of endothelial dysfunction.