A study of autonomic nervous system status in children of asthmatic parents.

Asthmatic patients are known to have autonomic abnormalities. This study evaluated the status of autonomic nervous system in children of asthmatic parents for any occurrences of autonomic abnormalities that are known to occur in asthma. In this study autonomic function tests were conducted in children (5 to 10 years of age) divided into two groups: Group A had children from non-asthmatic parents as Control Group and Group B had children from asthmatic parents as Test Group. Both the groups had healthy children showing no clinical signs and symptoms of asthma, allergy or any illness known to affect autonomic nervous system. In response to various parasympathetic function tests (S/L ratio, 30:15 ratio, valsalva ratio and tachycardia ratio) and sympathetic function tests (handgrip test and cold pressor test) done, the two groups did not show any statistically significant dissimilarity for any of the parameters. The results of our study showed that there were no autonomic abnormalities found in the children of asthmatic parents. Thus this study indicates that the autonomic defects seen in asthmatics could be secondary to asthma and not because of autonomic aberrations inheritance in asthmatics as shown by earlier few studies supporting the possible role of inherited automatic reactivity in the pathogenesis and progression of asthma.

Autonomic reactivity to cold pressor test in prehypertensive and hypertensive medical students.

Autonomic reactivity to stress has been hypothesized to be a marker for subsequent neurogenic hypertension. Medical training is highly stressful particularly for those who are beginning their medical education. The present study was undertaken to study the autonomic reactivity to cold pressor test in prehypertensive and hypertensive undergraduate medical students. One hundred and seventeen undergraduate medical students between 17-21 years of age got examined for blood pressure and stress level. Twelve Hypertensives and eight prehypertensives selected from the above subjects and twenty normotensives underwent cold pressure test (CPT) to assess autonomic reactivity to laboratory induced stress. 10.25% of the subjects were found to be hypertensive and 6.83% pre hypertensive. On the stress scale 53% had mild stress, 7% showed moderate stress while none had stress as a major problem. There was no correlation between BP and stress score. On CPT, BP increased significantly in all the three groups (hypertensive, prehypertensive and normotensive) but came back to basal levels within 5 minutes indicating normal autonomic response. Rise of BP was higher in hypertensive group as compared to normotensive group. The rise of diastolic and mean BP during CPT was significantly higher in subjects having family history of hypertension. Forty percent of normotensive subjects had more than 20 mm Hg rise in systolic BP on CPT. Adolescents must be routinely screened to detect asymptomatic hypertension. The CPT may identify individuals with an occult physiological abnormality that predisposes them to hypertension in their later life.

Effect of Graded Head-Up Tilt & Head-Reverse Tilt on the Sympathetic Nervous System Versus Parasympathetic Nervous System

The study was undertaken on 150 healthy human subjects of both the sexes in the age group of 18- 38 years to assess the effect of graded head-up tilt (HUT) and head-reverse tilt (HRT) on sympathetic nervous system Vs parasympathetic nervous system. The tilt positions used were 00, 300, 600, 300R and 00R. The parameters and test performed were pulse rate, blood pressure, cold pressor test, QTC interval, valsalva ratio and expiratory-inspiratory (E:I) ratio. On graded head-up tilt (600) pulse rate and diastolic blood pressure showed significant increase. Cold pressor test and QTc interval showed significant increase from 300 to 600 tilt. The valsalva and E:I ratios did not show any significant change on graded HUT. On reversal of tilt all the parameters showing significant increase returned to near pre-tilt values. These responses clearly indicate that graded HUT leads to decrease in parasympathetic reactivity but increase in sympathetic reactivity, which is more significant during higher tilt levels (300 to 600). On reversal of tilt both the parasympathetic reactivity and the sympathetic reactivity i.e. autonomic reactivity return to normal pre-tilt level.