Changes in left ventricular activity during apnea and face immersion.

Apneic face immersion in water has been analyzed with respect to its effects upon heart rate and ventricular function in a group of highly trained teenaged swimmers of both sexes. Both parameters have been studied on a beat-by-beat basis throughout the maneuvers and analysis of the systolic time intervals has provided a noninvasive tool for studying changes in ventricular function. It was observed that the pre-ejection period of systole is lengthened, while left ventricular ejection time shows little change with apnea, face wetting (27 degrees C), or a combination of these. This decrease in ventricular function, however, lags behind the previously well-recognized decrease in heart rate, a difference which is particularly obvious when face immersion is performed in the postexercise state. This suggests ventricular function changes are regulated separately from heart rate changes and thus may be a secondary effect. Analysis of the face immersion reflex on a beat-by-beat basis has also revealed a more rapid development of bradycardia with colder (15 degrees C) water. A model has been developed to describe the face immersion reflex in the light of these findings and previous information.