Adaptations to deep breath-hold diving: respiratory and circulatory mechanics

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Adaptations to deep breath-hold diving: respiratory and circulatory mechanics

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Title: Adaptations to deep breath-hold diving: respiratory and circulatory mechanics
Author: Leith, DE
Abstract: Respiration and circulation in diving mammals are characterized by interrelated adaptations of structure, function, and behavior that are incompletely described and understood. This speculative survey touches some of them. a) Arterial blood flow can be controlled by vasoconstriction not only in arterioles but also in large arteries. The latter physiology is not well known. b) Mechanisms that might regulate and limit nitrogen uptake are not clear, although Scholander's suggestion that airspaces become gas-free during deep dives is still accepted. c) Systemic arterial retes may be able to store oxygenated blood in some diving mammals. If so, O2 in the lung might be "skimmed off" early in a dive, leaving the N2 behind. d) Variable clusters of interdependent adaptations in diving mammals include compliant chest walls that avoid thoracic squeeze; inspiratory breath holds that maintain high lung volumes; large tidal volumes that nearly empty the lung at end-expiration (so there is near-complete turnover of lung gas with each breath); airways that are "armored" by cartilage rings all the way out to the airspaces (so that they do not close and trap gas in the lung and do permit high expiratory flow rates even at very low lung volumes); submucosal vascular retes that may prevent airway squeeze; a puzzling difference in the cross-sectional areas of trachea and bony nares; and very large lungs in shallow divers (sea otters). Study of mammalian adaptations to deep diving promises to illuminate basic issues in physiology.
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org )
URI: PMID: 2678665
http://archive.rubicon-foundation.org/2515
Date: 1989

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  • Undersea Biomedical Research Journal
    The Undersea Baromedical Research journal was published by the Undersea Medical Society, Inc. (now the Undersea and Hyperbaric Medical Society) quarterly from 1974 to 1992 when the name changed to the Undersea and Hyperbaric Medicine Journal.

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