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Of what value are electrocardiograms of seals, alligators, turtles, grunions, pearl divers, sea lions, or mud skippers to clinical medicine?
All these ECG subjects share one common activity: they dive, or experience periodic asphyxia while in a foreign oxygen-intake environment. And in diving, each manifests a distinct bradycardia and significant decrease in peripheral circulation.
This asphyxia-induced bradycardia parallels the selective ischemia which occurs in man during hemodynamic crises, such as shock and coronary insufficiency.
"The diving creature may provide a very useful tool with which to study the changes in blood flow distribution as seen in shock and other pathological states," according to Robert W. Elsner, PhD, associate research physiologist at the Scripps Institution of Oceanography in La Jolla, Calif,
Evidence from dogs and from seals of pronounced ischemia in renal and mesenteric circulation as well as in muscle circulation during asphyxia indicates that this "probably occurs in man, although
Asphyxia-Induced Bradycardia. JAMA. 1964;187(9):21–24. doi:10.1001/jama.1964.03060220067035