Influence of age and gender on cold pressor response in Indian population.

Cold pressor test (CPT) is a simple and well documented laboratory test to evaluate the propensity for hypertension and sympathetic autonomic functions. Role of sex hormones was tested in the present study for the cold pressor response (CPR) in young adults of both sexes and in elderly population. The subjects comprised of young male (n=55), female (n=32) medical students of 17-25 years and elderly males (n=39) and females (n=25) of 50-70 years of age. The CPT was carried out in young and elderly males and females with one minute immersion of one hand in ice cold water (0-4°C). Both in young males and females the absolute rise in SBP and DBP in response to Cold pressor test (CPT) was highly significant, with diastolic percent rise exceeding systolic. In comparison to young males, the females showed greater percent rise in SBP and DBP. Similarly, in elderly groups of both sexes, CPR was associated with significant absolute rise in SBP and DBP with diastolic percent rise more than systolic in males only. Both in young versus elderly males and young versus elderly females comparison yielded comparable percent rise in SBP and DBP. The SBP and DBP percent rise was again comparable between elderly males and females. The greater responsiveness to CPT in young females could be attributed to increased pain sensitivity to cold, and/or genetic and hereditary factors overwhelming the hormonal protection offered by estrogen and nitric oxide (NO).

Influence of alternate nostril breathing on cardiorespiratory and autonomic functions in healthy young adults.

Alternate nostril breathing (ANB) may modulate cardio-respiratory and autonomic functions. However, the studies are scarce and results highly conflicting. The present study was conducted in healthy young volunteers comprising of males (n=20) and females (n=20) in range of 17-22 years. In both groups respiratory rate (RR/min), heart rate (HR/ min), systolic blood pressure (SBP; mm Hg), diastolic blood pressure (DBP; mm Hg), peak expiratory flow rate (PEFR; L/min) and galvanic skin resistance (GSR; microV) were recorded thrice; once as control and then after 15 min (acute exposure) and following 8 wks of training in ANB (15 min daily). In males the control RR was 16.60 +/- 2.01, HR 75.75 +/- 11.07, SBP-115.9 +/- 7.33, DBP 70.4 +/- 6.28 and PEFR 550.00 +/- 51.50. After 15 min of ANB-RR (14.75 +/- 1.41, P<0.001), HR (68.45 +/- 12.41, P<0.01) and SBP (113.6 +/- 6.04, P<0.05) fell significantly. After 8 wks of ANB training RR (12.35 +/- 1.35, P<0.0001), HR (63.20 +/- 11.11, P<0.001), SBP (109.5 +/- 5.61, P<0.001), declined to much greater extent and PEFR (571.50 +/- 46.26, P<0.01) rose significantly. In females the control RR was 17.25 +/- 1.89, HR-74.90 +/- 12.85, SBP-106.70 +/- 6.91, DBP-68.70 +/- 5.52 and PEFR-394.50 +/- 44.89. After 15 min of ANB RR (15.05 +/- 1.54, P<0.001) and HR (64.75 +/- 9.80, P<0.001) showed significant decline with concomitant rise in PEFR (407.00 +/- 2.31, P<0.05). Following 8 wks training the decrement in RR (12.60 +/-1.50, P<0.0001) and HR (63.30 +/- 8.65, P<0.001) was maintained. SBP (103.10 +/- 4.92, P<0.001) and DBP (65.8 +/- 5.54, P<0.001) decreased further and PEFR (421.00 +/- 38.51 P<0.001) rose, GSR was unaffected by ANB in both males and females. These results suggest that in general there is a tilt towards parasympathetic dominance by alternate nostril breathing. This breathing may be a useful adjuvant to medical therapy of hypertension and COPD.

The effects of right and left nostril breathing on cardiorespiratory and autonomic parameters.

The responses of right nostril breathing (RNB) and left nostril breathing (LNB) on cardio-respiratory and autonomic functions were investigated in healthy student volunteers of both sexes. The RNB and LNB groups comprised of 10 males and 10 females in each in age range of 17-22 years. Initially, in both groups control values of respiratory rate (RR), heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBF), peak expiratory flow rate (PEFR) and galvanic skin resistance (GSR) were recorded. The same parameters were recorded after 15 min (acute exposure) and 8 wks of training in RNB and LNB. In males RR (P<0.0001), SBP (P<0.05) and DBF (P<.05) fell significantly after 15 min of RNB. After 8 wks training in RNB, HR (P<0.01) decreased, SBP (P<0.001) declined more profoundly and RR (P<0.0001) and DBP (P<0.05) decrement was maintained. After 15 min of LNB, RR (P<0.01), HR (P<0.01), SBP (P<0.001) and DBP (P<0.01) declined significantly, on 8 wks training, RR (P<0.0001) and HR (P<0.001) decreased further, the decrement in SBP (P<0.001) and DBP (P<0.01) was the same. In females, RR alone fell significantly (P<0.05) after 15 min RNB. After 8 wks RR decrement was more profound (P<0.0001) and DBP also declined significantly (P<0.01). Similarly, 15 min LNB resulted in significant reduction in RR (P<0.001) and HR (P<0.05) only. Following 8 wks, of training in LNB, in addition to RR (P<0.0001) and HR (P<0.05) decrement, SBP (P<0.01) and DBP (P<0.05) also fell significantly. Both in males and females, GSR did not change significantly (P>0.05) either after RNB or LNB (15 min/8 wks). PEFR rose significantly (P<0.05) only in females after 8 wks of LNB. The results suggest that there are no sharp distinctions between effects of RNB and LNB either acute exposure (15 min) or after training (8 wks). However, there is a general parasympathetic dominance evoked by both these breathing patterns.

Electrocardiographic changes following exercise in the congenitally deaf school children: relationship with Jervell Lange Neilsen syndrome (the Long QT syndrome).

The present study was conducted to test the effects of exercise stress on the ECG of the congenitally deaf children from school for deaf, in view of the occurrence of the Jervell-Lange Neilsen (Surdo Cardiac) variant of the Long QT Syndrome (LQTS) in them. An ECG Lead II was recorded at rest and after two minutes of static jogging. For comparison, the same protocol was repeated in normal healthy children from another school. ECG were analysed for the calculation of corrected QT interval (QTc) by Bazett's equation QTc = QT/square root of R-R and also for the evidence for other abnormalities. Both in the normal and deaf children, exercise did not produce significant (P > 0.05) change in QTc from their resting values. However, when pre and post exercise QTc values of deaf children were compared with normal children, the female deaf had significantly longer QTc (P < 0.01) both at rest and after exercise than normal female children. Normal children did not show significant ECG abnormality either at rest or on exercise. On the contrary many of their counter part (deaf) exhibited occasional ECG abnormality at rest but plethora of abnormalities after exercise viz., sinus arrhythmias, sinus pauses, ST depression, T-inversion, biphasic-T, notched-T, T-alternans, nodal ectopics and junctional rhythm. These results lend credence to the hypothesis of sympathetic imbalance and repolarisation defects in deaf children's heart, which in more severe form could pass into frank Jervell-Lange Neilsen variant of the Long: QT Syndrome.

Influence of divalent cations on rabbit atria and modification of catecholamine response on pacemaker cells.

Spontaneously beating isolated atria of rabbits responded to Mn++ and Co++ with a progressively increasing negative chronotropism and inotropism, which was reversible by washout and by elevating the bath concentration of Ca++. The cumulative dose response curve for adrenaline for chronotropic response was markedly shifted to the right in the presence of Mn++ or Co++. This effect was also reversible. Verapamil produced only a moderate decline in spontaneous rate and contractility and did not block the chronotropic response to adrenaline. It is concluded that Mn++ and Co++ block the action of catecholamine on the pacemaker cells and they differ at least in part from organic calcium channel antagonists in their mechanism of action.

Evidence for both H and H2-histamine receptors in rabbit atria.

Spontaneously beating isolated atria of rabbits responded to histamine (0.5-16 micrograms/ml) with positive chrono- and inotropism. However, the inotropic response was greater than chronotropic one. The concentration-response curve of histamine for chronotropic effect was markedly shifted to the right in the presence of 0.5 micrograms/ml metiamide (H2-receptor antagonist), which per se augmented the control contractile amplitude in all the experiments. The rightward shift of chronotropic concentration response curve with mepyramine (H1-antagonist) was, however, moderate. On the contrary, the inotropic concentration response curve of histamine was shifted to much greater extent to right with mepyramine (0.62 micrograms/ml) than with metiamide, thus suggesting a greater share of H1 than H2-receptors in the mediation of positive inotropic effect of histamine. The chronotropic effect appears to be mediated predominently by H2-receptors. Unlike metiamide, mepyramine did not alter the spontaneous frequency or amplitude of contraction. The present study, thus lends support for dual histamine receptors in rabbit atria.

A mechanism of action of phenylephrine on heart.

Phenylephrine exerted a positive chronotropic and inotropic effect on isolated, spontaneously beating, atria of reserpinised rabbits. Addition of phenoxybenzamine and phentolamine resulted in a depression of control contractile amplitude. Practolol, however, was devoid of this effect. The positive inotropic response to phenylephrine was significantly antagonised by all the three blockers used, while positive chronotropic response was annulled by phentolamine and practolol, but not with phenoxybenzamine. It is, therefore, suggested that phenylephrine exerts its cardiostimulant effects through mediation of both alpha and beta-1 adrenoceptors. A probable mechanism of action could be, that phenylephrine acts on some specific chemical group, shared by alpha and beta1 receptors. This specific group is probably blocked by both alpha and betaceptor antagonists separately, so phenylephrine becomes ineffective in presence of these antagonists.

The role of nerves in the production of cardiac arrest during surgical anaesthesia.

The role of cardiac nerves in the production of cardiac arrest during surgical anaesthesia on coronary ligated hypoxic heart has been studied. When atropinished coronary ligated dogs were exposed to hypoxia the terminal event was a cardiac asystole in 88% of the dogs. In propranolol treated dogs, or in dogs where sympathetic ganglia upto T6 were bilaterally removed earlier, coronary ligation and hypoxia produced ventricular extrasystoles, ventricular tachycardia and repeated sinus arrest followed by ventricular fibrillation. The possibility of the origin of arrythmia from the damaged myocardium, and the presence of an intact vagus in the production of ventricular fibrillation has been discussed.