Hypercapnia in diving: a review of CO₂ retention in submersed exercise at depth.
Abstract
Carbon dioxide (CO₂) retention, or hypercapnia, is a known risk of diving that can
cause mental and physical impairments leading to life-threatening accidents. Often,
such accidents occur due to elevated inspired carbon dioxide. For instance, in cases
of CO₂ elimination system failures during rebreather dives, elevated inspired partial
pressure of carbon dioxide (PCO₂) can rapidly lead to dangerous levels of hypercapnia.
Elevations in PaCO₂ (arterial pressure of PCO₂) can also occur in divers without a
change in inspired PCO₂. In such cases, hypercapnia occurs due to alveolar hypoventilation.
Several factors of the dive environment contribute to this effect through changes
in minute ventilation and dead space. Predominantly, minute ventilation is reduced
in diving due to changes in respiratory load and associated changes in respiratory
control. Minute ventilation is further reduced by hyperoxic attenuation of chemosensitivity.
Physiologic dead space is also increased due to elevated breathing gas density and
to hyperoxia. The Haldane effect, a reduction in CO₂ solubility in blood due to hyperoxia,
may contribute indirectly to hypercapnia through an increase in mixed venous PCO₂.
In some individuals, low ventilatory response to hypercapnia may also contribute to
carbon dioxide retention. This review outlines what is currently known about hypercapnia
in diving, including its measurement, cause, mental and physical effects, and areas
for future study.
Type
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https://hdl.handle.net/10161/15586Collections
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Show full item recordScholars@Duke
Anne Cherry
Associate Professor of Anesthesiology
Sophia Dunworth
Assistant Professor of Anesthesiology
John Jacob Freiberger
Adjunct Associate Professor in the Department of Anethesiology
Dr Freiberger works on the translation of basic science research on reactive oxygen
species signaling into clinical practice involving hyperbaric oxygen (HBO). He has
performed animal experiments in the use of HBO for ischemic preconditioning and he
is currently funded to conduct a randomized controlled trial of the use of HBO for
the treatment of bisphosphonate-induced osteonecrosis of the jaw. The mechanisms of
action for HBO in the treatment of: diabetic wounds, bony and soft tissue rad
Richard Edward Moon
Professor of Anesthesiology
Research interests include the study of cardiorespiratory function in humans during
challenging clinical settings including the perioperative period, and exposure to
environmental conditions such as diving and high altitude. Studies have included gas
exchange during diving, the pathophysiology of high altitude and immersion pulmonary
edema, the effect of anesthesia and postoperative analgesia on pulmonary function
and monitoring of tissue oxygenation. Ongoing human studies include the effect of
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