Cardiovascular reflex responses to apnoeic face immersion and mental stress in diabetic subjects.

The cardiovascular reflex responses to apnoea accompanied by immersion of the face in water and to mental stress, have been investigated in 21 diabetic subjects. Apnoeic face immersion caused bradycardia and forearm vasoconstriction (in seven subjects), bradycardia and forearm vasodilation (three subjects), tachycardia and forearm vasoconstriction (three subjects), or tachycardia and forearm vasodilatation (eight subjects). Mental stress evoked a tachycardia and forearm vasodilatation in all subjects. The abnormalities in the responses to apnoeic face immersion are most readily accounted for by loss of vagal and/or vasoconstrictor function.