title: The human dive reflex: an experimental, topographical and physiological analysis.
abstract: This study examined the eliciting conditions, response topography and autonomic nervous system (ANS) control of the dive reflex as evoked in humans. Twenty-four subjects received eight trials in each of the three treatment conditions: breath holding without face immersion (BH); face immersion without breath holding (FI); and the "full dive" FIBH condition. It was the combination of both FI and BH in 23 +/- 0.5 degrees C water that was necessary to elicit the dive reflex. A precise topographical analysis differentiated the FIBH condition from the FI and BH control conditions in terms of the emergence of a secondary component initiated approximately 12 seconds after trial onset. During this secondary component, augmentation of bradycardic (mean = 16.3 bpm) and digital vasoconstrictive (mean = -24.9%) responses were maintained throughout the duration of the 40-second dive. A joint consideration of the heart rate and the T-wave amplitude measures as indices of the action of both branches of the ANS suggested that the dive reflex involves concurrent sympathetic and parasympathetic activation. A potential conditioning application of the dive reflex for countering paroxysmal supraventricular tachycardia was discussed.
mesh_terms: D000293:Adolescent; D000328:Adult; D002320:Cardiovascular Physiological Phenomena; D004242:Diving; D004562:Electrocardiography; D005145:Face / Q000502:physiology; D005260:Female; D005385:Fingers / Q000098:blood supply; D006339:Heart Rate; D006801:Humans; D008297:Male; D012018:Reflex / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D014661:Vasoconstriction; D014666:Vasomotor System / Q000502:physiology