Oxygen Saturation During Breath Holding
Shallow water “black-out” or syncope is a recognised problem amongst divers. The term “shallow water” is used to indicate depths down to 30 m. Various mechanisms have been incriminated. These fall largely into the two groups, neurogenic and respiratory. The first category will include the mixed autonomic responses to sudden immersion in cold water, stimulus of the fifth cranial nerve and the bradycardia of apnoea. These can lead to severe dysrhythmias, acute heart failure and cardiac arrest. The respiratory causes include acute CNS oxygen toxicity when diving with pure oxygen—a specialised and uncommonly used technique—and the effects of nitrogen solution in body fluids. The last may cause problems both in scuba and snorkel divers in this depth range. Of the coincidental causes of syncope, epilepsy is rare, but less so the interactions of drugs with changes in oxygen, nitrogen and carbon dioxide tensions.
KeywordsToxicity Dioxide Rubber Explosive
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