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Study of the reflex heart rate response in humans to apneic facial immersion (simulated diving) and its modifications showed that bradycardia caused by simple application of cold compresses to the face (cold face test) correlated well with that produced by the simulated diving reflex. Bilateral application of cold stimulus to the individual divisions of the trigeminal nerve revealed the ophthalmic division to be the most sensitive pathway for this reflex. The cold face test was standardized in 50 normal individuals and further validated in 10 patients by comparison with the simulated diving reflex, the Valsalva maneuver, and administration of atropine. Patients with diabetes mellitus, brainstem stroke, multiple sclerosis, or Shy-Drager syndrome developed less than normal bradycardia or minimal tachycardia in response to the cold facial stimulus. The cold face test is a novel, simple, safe, and economical test of the integrity of trigeminal-brainstem-vagal reflex pathways, can be utilized practically to assess vagal and brainstem dysfunctions, and has the special advantage of being applicable even in an uncooperative or comatose patient.
Khurana et al. (Fri,) studied this question.