Human Anatomy & Physiology (9th Edition)

Published by Pearson
ISBN 10: 0321743261
ISBN 13: 978-0-32174-326-8

Chapter 22 - The Respiratory System - Review Questions - Critical Thinking and Clinical Application Questions - Page 847: 4


Mary Ann's symptom's are diagnostic of decompression sickness , a syndrome frequently experienced by scuba divers who do not allow enough time to decompress after scuba diving. In this case Mary Ann did not have any symptoms while she was a sea level in the Bahamas, Her symptoms and signs only manifested at about 8,000 feet during her airplane trip back home. This is the special case of altitude decompression illness/sickness. The signs and symptoms (SS) are typical --joint pain, nausea, and shortness of breath (dyspnea).

Work Step by Step

Scuba diving requires breathing air( N2, O2 and CO2) under higher than atmospheric partial pressures. This means that significantly larger amounts (%) of these gases become dissolved in the blood than is the case at sea level partial pressures. The extra oxygen can be used by the tissues and this allows the driver to remain under water longer than usual. Nitrogen is an inert gas and is not usable by tissues. Although it is not very soluble in plasma or tissue fluids at atmospheric pressures, under compression the amount dissolved increases. It has been shown that the amount of nitrogen dissolved in plasma or tissue fluid is directly proportional to partial pressure of nitrogen ( Henry's Law). The small increase of the amount of nitrogen in the blood is fine, as long as the diver stays under water ; however, as he/she ascends to the surface and the pressures drops towards atmospheric pressure, and scuba gear is removed, the partial pressure of the gases decline towards normal. As a result gases tend to come out of solution. Nitrogen is less soluble than oxygen or carbon dioxide and so comes out of solution most readily. As the nitrogen comes out of solution if forms blebs and bubbles. These bubbles of nitrogen from tissues tend to accumulate around joints, get into the blood stream, and travel to the lungs and brain. Mary Ann had a mild case of altitude decompression sickness; her symptoms resolved on landing from her flight . But decompression sickness may be prolonged, severe --even fatal--, if lungs and and central nervous system become seriously affected. Symptoms can vary from skin itch, tingling , crawling feeling under skin of arms and legs, swelling, to headaches confusion, seizures, vomiting, abdominal and chest pain, confusion, seizures and unconsciousness. Divers should ascend slowly and allow at least 12 hours between last dive and an airplant flight. Note: According to Henry's Law , the amount of gas dissolved is directly proportional to the partial pressure of the gas in the gas phase,
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