TY - JOUR
T1 - Dark adaptation at high altitude
T2 - An unexpected pupillary response to chronic hypoxia in Andean highlanders
AU - Healy, Katherine
AU - Labrique, Alain B.
AU - Miranda, J. Jaime
AU - Gilman, Robert H.
AU - Danz, David
AU - Davila-Roman, Victor G.
AU - Huicho, Luis
AU - León-Velarde, Fabiola
AU - Checkley, William
N1 - Publisher Copyright:
© Mary Ann Liebert, Inc. 2016.
PY - 2016/9
Y1 - 2016/9
N2 - Chronic mountain sickness is a maladaptive response to high altitude (>2500 m above sea level) and is characterized by excessive erythrocytosis and hypoxemia resulting from long-term hypobaric hypoxia. There is no known early predictor of chronic mountain sickness and the diagnosis is based on the presence of excessive erythrocytosis and clinical features. Impaired dark adaptation, or an inability to visually adjust from high- to low-light settings, occurs in response to mild hypoxia and may serve as an early predictor of hypoxemia and chronic mountain sickness. We aimed to evaluate the association between pupillary response assessed by dark adaptometry and daytime hypoxemia in resident Andean highlanders aged ≥35 years living in Puno, Peru. Oxyhemoglobin saturation (SpO2) was recorded using a handheld pulse oximeter. Dark adaptation was quantitatively assessed as the magnitude of pupillary contraction to light stimuli of varying intensities (-2.9 to 0.1 log-cd/m2) using a portable dark adaptometer. Individual- and stimulus-specific multilevel analyses were conducted using mixed-effect models to elicit the relationship between SpO2 and pupillary responsiveness. Among 93 participants, mean age was 54.9 ± 11.0 years, 48% were male, 44% were night blind, and mean SpO2 was 89.3% ± 3.4%. The magnitude of pupillary contraction was greater with lower SpO2 (p < 0.01), and this dose relationship remained significant in multiple variable analyses (p = 0.047). Pupillary responsiveness to light stimuli under dark-adapted conditions was exaggerated with hypoxemia and may serve as an early predictor of chronic mountain sickness. This unexpected association is potentially explained as an excessive and unregulated sympathetic response to hypoxemia at altitude.
AB - Chronic mountain sickness is a maladaptive response to high altitude (>2500 m above sea level) and is characterized by excessive erythrocytosis and hypoxemia resulting from long-term hypobaric hypoxia. There is no known early predictor of chronic mountain sickness and the diagnosis is based on the presence of excessive erythrocytosis and clinical features. Impaired dark adaptation, or an inability to visually adjust from high- to low-light settings, occurs in response to mild hypoxia and may serve as an early predictor of hypoxemia and chronic mountain sickness. We aimed to evaluate the association between pupillary response assessed by dark adaptometry and daytime hypoxemia in resident Andean highlanders aged ≥35 years living in Puno, Peru. Oxyhemoglobin saturation (SpO2) was recorded using a handheld pulse oximeter. Dark adaptation was quantitatively assessed as the magnitude of pupillary contraction to light stimuli of varying intensities (-2.9 to 0.1 log-cd/m2) using a portable dark adaptometer. Individual- and stimulus-specific multilevel analyses were conducted using mixed-effect models to elicit the relationship between SpO2 and pupillary responsiveness. Among 93 participants, mean age was 54.9 ± 11.0 years, 48% were male, 44% were night blind, and mean SpO2 was 89.3% ± 3.4%. The magnitude of pupillary contraction was greater with lower SpO2 (p < 0.01), and this dose relationship remained significant in multiple variable analyses (p = 0.047). Pupillary responsiveness to light stimuli under dark-adapted conditions was exaggerated with hypoxemia and may serve as an early predictor of chronic mountain sickness. This unexpected association is potentially explained as an excessive and unregulated sympathetic response to hypoxemia at altitude.
KW - chronic mountain sickness
KW - hypoxemia
KW - impaired dark adaptation
KW - oxyhemoglobin saturation
KW - portable field dark adaptometer
KW - pupillary contraction
UR - http://www.scopus.com/inward/record.url?scp=84990181234&partnerID=8YFLogxK
U2 - 10.1089/ham.2016.0041
DO - 10.1089/ham.2016.0041
M3 - Article
C2 - 27454014
AN - SCOPUS:84990181234
SN - 1527-0297
VL - 17
SP - 208
EP - 213
JO - High Altitude Medicine and Biology
JF - High Altitude Medicine and Biology
IS - 3
ER -