Sensitivity to vasovagal maneuvers in normal children and adults.

In 15 male and 15 female healthy subjects who were 10 to 48 years of age, we studied alterations in heart rate and finger blood flow in response to the cold pressor test and four strong vasovagal maneuvers: diving response (apneic facial exposure to an ice water bag), Valsalva maneuver (forced expiration against a column of mercury to 40 to 50 mm Hg), unilateral carotid sinus massage, and oculocardiac reflex (inflation of a Honan balloon against one eye). Peripheral vasoconstriction as a consequence of the diving response paralleled the vasoconstriction from the cold pressor test, but it preceded the bradycardia that resulted from the diving response maneuver. In contrast, the rate of finger blood flow was high during the bradycardia that followed stage 4 of the Valsalva maneuver. Changes in heart rate correlated with age for the diving response, the Valsalva maneuver, and the oculocardiac reflex. Changes in heart rate and finger blood flow were not dependent on sex. The change in heart rate noted with the diving response was significantly correlated with that noted with the Valsalva maneuver and the oculocardiac reflex. Changes in finger blood flow did not correlate with changes in heart rate for any maneuver. This study provides a response profile of relative sensitivities to strong vasovagal maneuvers in normal children and adults.