Structure and Function of Carotid Bodies at High Altitude
The mechanism of respiratory drive during acclimatization to environmental hypoxia is a much debated question. Rahn and Otis (1949) formulated and summarized the question in an alveolar PO 2 — PCO 2 diagram, which is partially reproduced in Fig. 1.1. This figure shows alveolar ventilatory responses in humans to acute (broken lines) and chronic (solid line) exposure to altitudes. The altitude diagonals for sea level, 10,000 ft and 18,000 ft (RQ = 0.85), are also shown. The solid line connecting A and B represents the alveolar values of the acclimatized newcomers to high altitude. Point A is the sea-level value, and the dotted line originating at this point is the response to acute hypoxia. Point B is the alveolar value for humans acclimatized at approximately 10,000 ft, and the dotted line passing through B again indicates the ventilatory responses to acute changes in altitude. If a man were transported to 10,000 ft from sea level, his alveolar pathway would start at A and proceed along the dotted line to the intersection with the 10,000-ft diagonal. With time it would travel down the 10,000-ft altitude diagonal to its intersection with the acclimatized curve (point B). If the man returned to sea level, his alveolar pathway would travel from B on the dotted line to the right until it intersects the sea-level diagonal, and from there proceed to point A along the diagonal in several days.
KeywordsHigh Altitude Carotid Body Ventilatory Response Chronic Hypoxia Acute Hypoxia
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