Abstract 066: Adaptive and physiological cerebrovascular changes at high altitudes: a systematic review and meta‐analysis

Introduction moderate altitude, considered over 1,500 meters (about 4921 ft) above sea level (m.a.s.l), is a particular environment due to the lower oxygen pressure that conditions the development of adaptive mechanisms such as cerebrovascular changes expressed in cerebral blood flow (CBF). Several...

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Autores principales: Julio A. Chirinos, P. Zila-Velasque, Pamela Grados‐Espinoza, Sebastian Abanto-Urbano, Mely Olarte-Durand, Martha Isabel Vilca-Salas, Paula Moran-Ballon, Victor Velásquez‐Rimachi, Kateriny Margot Regalado-Rodríguez, Carlos Quispe‐Vicuña, Fernando Terry, Carlos Alva‐Díaz
Formato: Conference abstract
Lenguaje:inglés
Publicado: 2024
Materias:
high altitude
cerebral blood flow
cerebral autoregulation
middle meningeal artery
cerebral oxygen saturation
cerebrovascular resistance
cerebral venous oxygen saturation
cerebral blood volume
cerebral oxygen extraction fraction
hypoxia
high-altitude adaptation
High Altitude and Hypoxia
Cardiovascular and Diving-Related Complications
Spaceflight effects on biology
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Sumario:Introduction moderate altitude, considered over 1,500 meters (about 4921 ft) above sea level (m.a.s.l), is a particular environment due to the lower oxygen pressure that conditions the development of adaptive mechanisms such as cerebrovascular changes expressed in cerebral blood flow (CBF). Several studies have explored changes in CBF in small populations, however, changes at different altitudes, populations and units of measurement have not been described. These characteristics have been associated with cerebrovascular adaptation Methods We systematically searched databases (PubMed‐Medline, Embase, Web of Science, Scopus and Google Scholar) until January 2022 for studies evaluating cerebrovascular changes resulting from exposures at altitudes greater and lower than 1500 m.a.s.l. The Newcastle‐Ottawa scale and RoB‐2 tools was used to assess the risk of bias from observational studies and randomized clinical trials, respectively. A meta‐analysis using a random‐effects model to estimate pooled effects was realized for each outcome and a narrative synthesis when this was not possible. GRADE criteria were used to identify the certainty of evidence for each result. Results We included 58 studies (2 randomized clinical trials and 56 non‐randomized clinical trials) with 1959 patients. Most studies were at low risk of bias. We found that in the middle meningeal artery, altitude higher than 1500 m.a.s.l may reduce autoregulatory index (MD −0.42, 95% CI −0.67 to −0.18, I2 84%, 2 studies, low certainty), cerebral oxygen saturation (MD −5.65, 95% CI −8.63 to −2.67, I2 91%), cerebral oxygen saturation (MD −5.65, 95% CI ‐8.63 to ‐2.67, I2 91%) and cerebral oxygen saturation (MD ‐5.65, 95% CI ‐8.63 to ‐2.67, I2 91%): ‐8.63 to ‐2.67, I2: 91%, 3 studies, low certainty), cerebrovascular resistance (MD: ‐25.04, 95% CI: ‐75.61 to 25.54, I2: 100%, 2 studies, low certainty) and Cerebrovascular Conductance (MD: ‐0.01, 95% CI: ‐0.05 to 0.03, I2: 0%, 2 studies, low certainty). Similarly, in the internal carotid and vertebral artery, altitude may increase global cerebral blood flow (MD 200.82, 95% CI 47.17 to 354.46, I2 70%, 2 studies, low certainty). Conclusion Exposure to altitudes above 1500 m.a.s.l reduces autoregulation and cerebral oxygen saturation but increases overall cerebral blood flow. These changes could indicate cerebrovascular adaptations to lower oxygen pressures, although the evidence is of low certainty due to variability between studies.

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