CARDIOVASCULAR-RESPONSES ELICITED BY DIFFERENT SIMULATED DIVING MANEUVERS

It has been documented that placing an icebag on the forehead causes s imilar cardiac and vascular responses as face immersion. There has bee n disagreement concerning the contribution of separate cold stimulatio n on the face and breathholding in the diving response. This study set out to unravel the extent to which these two factors contribute indiv idually to the observed cardiovascular changes during the combined man oeuvre. It further aimed to reveal whether peripheral vascular respons es to these stimuli are different in forearm and calf. We observed a s ignificant rapid increase in the RR-interval, which was maintained unt il the end of the 25-s observation period and a homogeneous vasoconstr iction in forearm and calf, despite minor changes in arterial blood pr essure, during breathholding, placing the icebag on the forehead and t he combined stimuli. Cardiac and peripheral vascular responses to the combined manoeuvre did not differ significantly from the responses eli citated by the two stimuli separately. This test is another example th at illustrates the heterogeneous cardiovascular response involving bot h parasympathetic and sympathetic activation. Moreover, since the iceb ag on the forehead test is technically easy to perform and does not re quire the active co-operation of the patient, it may be a valid method to replace a full face immersion test accompanied by breathholding.