In:
Journal of Applied Physiology, American Physiological Society, Vol. 122, No. 4 ( 2017-04-01), p. 844-852
Abstract:
High-altitude pulmonary edema (HAPE) is a potentially fatal condition affecting high-altitude sojourners. The biggest predictor of HAPE development is a history of prior HAPE. Magnetic resonance imaging (MRI) shows that HAPE-susceptible (with a history of HAPE), but not HAPE-resistant (with a history of repeated ascents without illness) individuals develop greater heterogeneity of regional pulmonary perfusion breathing hypoxic gas (O 2 = 12.5%), consistent with uneven hypoxic pulmonary vasoconstriction (HPV). Why HPV is uneven in HAPE-susceptible individuals is unknown but may arise from regionally heterogeneous ventilation resulting in an uneven stimulus to HPV. We tested the hypothesis that ventilation is more heterogeneous in HAPE-susceptible subjects ( n = 6) compared with HAPE-resistant controls ( n = 7). MRI specific ventilation imaging (SVI) was used to measure regional specific ventilation and the relative dispersion (SD/mean) of SVI used to quantify baseline heterogeneity. Ventilation heterogeneity from conductive and respiratory airways was measured in normoxia and hypoxia (O 2 = 12.5%) using multiple-breath washout and heterogeneity quantified from the indexes S cond and S acin , respectively. Contrary to our hypothesis, HAPE-susceptible subjects had significantly lower relative dispersion of specific ventilation than the HAPE-resistant controls [susceptible = 1.33 ± 0.67 (SD), resistant = 2.36 ± 0.98, P = 0.05], and S acin tended to be more uniform (susceptible = 0.085 ± 0.009, resistant = 0.113 ± 0.030, P = 0.07). S cond was not significantly different between groups (susceptible = 0.019 ± 0.007, resistant = 0.020 ± 0.004, P = 0.67). S acin and S cond did not change significantly in hypoxia ( P = 0.56 and 0.19, respectively). In conclusion, ventilation heterogeneity does not change with short-term hypoxia irrespective of HAPE susceptibility, and lesser rather than greater ventilation heterogeneity is observed in HAPE-susceptible subjects. This suggests that the basis for uneven HPV in HAPE involves vascular phenomena. NEW & NOTEWORTHY Uneven hypoxic pulmonary vasoconstriction (HPV) is thought to incite high-altitude pulmonary edema (HAPE). We evaluated whether greater heterogeneity of ventilation is also a feature of HAPE-susceptible subjects compared with HAPE-resistant subjects. Contrary to our hypothesis, ventilation heterogeneity was less in HAPE-susceptible subjects and unaffected by hypoxia, suggesting a vascular basis for uneven HPV.
Type of Medium:
Online Resource
ISSN:
8750-7587
,
1522-1601
DOI:
10.1152/japplphysiol.00494.2016
Language:
English
Publisher:
American Physiological Society
Publication Date:
2017
detail.hit.zdb_id:
1404365-8
SSG:
12
SSG:
31
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