Test for autonomic function to establish the norm: a useful tool for evaluation in various clinical disorders

RESUMO

Little information is available regarding the responses of the Jamaica population to the Valsalva manoeuvre (VM), a test to investigate the integrity of the autonomic nervous system (ANS). This study is aimed at investigating the cardiac automonic control in the Jamaican population, to explore the range of responses and to establish the norm. Such an explorative investigation provides an important tool to uncover autonomic dysfunction in psychosomatic, cardiopulmonary, metabolic and neural disorders. Fifity male and fifty female Jamaicans, who were apparently healthy and did not indulge in any drug use and smoking, are asked to perform the VM in a semirecumbent position. A tachograph (Grass model) and standard electrocardiographic leads are used for the graphic presentation of the subjects' beat-to-beat heart changes. The Valsava ratio (VR) is calculated by dividing maximum tachicardia and maximum bradicardia during the VM. The mean VR for the female (2.41 ñ 0.18) is greater than for the male (1.63 ñ 0.27) p < 0.001). Female subjects exhibit a higher basal hearth rate (88 ñ 6 as aginst 77 ñ 7 in the male) and a greater magnitude of bradycardia (33 as against 4 in the male). The values for VR are above the minimum of 1.5 proposed in the literature. Relatice roles of the sympathetic and parasympathetic nervous systems may differ in the male and the female subjects, thus accounting for a higher VR in the female. This test is simple, safe, noninvasive and reproducible and is useful to detect the abnormal autonomic function in various conditions, including states of pregnancy and stress