Underwater bradycardia.

Abstract

Te presence of a reflex mechamsm m man which triggers a bradycardia during apnea has gained rather wide acceptance in the literature. In resting man, there has been observed a heightened bradycardia with apneic face immersion in water. Past investigators have observed both a &dquo;breath holding&dquo; and a &dquo;water immersion&dquo; or &dquo;diving&dquo; reflex in the resting man. However, there is disagreement in the studies which have investigated the presence of these reflexes in exercising man. Several investigators observed bradycardia during apneic dmes. Anderson3 12 concluded that bradycardia persists in spite of vigorous exercise as in the case of diving vertebrates. Craig and Medd 15 criticized the lack of control of work in earlier studies and concluded that