Chapter 41. Altitude Physiology and Illness, Diving Medicine, and Hyperbaric Oxygen Therapy

Clayton T Cowl, MD, MS, FCCP
DOI: 10.1378/pulm.26.41
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  • Review atmospheric composition and the basics of altitude physiology including gas laws.

  • Understand symptoms and clinical approach to high-altitude illnesses.

  • Appreciate issues with air travel for special populations with cardiopulmonary conditions.

  • Discuss basic concepts of diving medicine including contraindications, risks, and untoward events.

  • Recognize early effects of drowning or near drowning.

  • Know the accepted indications and general principles of hyperbaric oxygen therapy.


From the depths of the oceans to the outer reaches of the earth's atmosphere, we are bathed in a pressure environment. The principles of physiology are useful in describing observed changes at depth or altitude and include laws that explain the behavior of gases. The atmosphere is divided into several layers, including the troposphere, where weather exists. Hypobaric hypoxia exists at high altitudes in which the pressure exerted by the atmosphere is so low that tissue hypoxia results because of lack of alveolar driving pressure. Several conditions are associated with respiratory abnormalities at terrestrial altitude, including acute mountain illness, high-altitude pulmonary edema, and high-altitude cerebral edema. Because of decreased pressure at altitude, special consideration should be provided for individuals with preexisting cardiopulmonary disease. Thousands of people participate in diving activities each year, making important to understand the basic concepts of diving physiology and some of the unique pulmonary risks encountered while diving. Hyperbaric oxygen therapy provides an increased partial pressure of oxygen to poorly vascularized tissues in patients with difficult-to-heal vascular wounds and radiation-induced tissue breakdown and has also been useful in managing acute sequelae of arterial gas embolisms or histotoxic hypoxia from carbon monoxide inhalation. As with other procedural interventions in medicine, there are also contraindications to hyperbaric oxygen that should be carefully managed.


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