Paroxysmal Gamma brain waves produced during the Bhramari Pranayama [1] which are associated with positive thought, feeling of happiness and acts as natural antidepressant [2].

Lots of diseases occur due to stress in a modern society. Hypertension is one of the commonest stress-induced cardiovascular disorder, posing a major public health challenge to population in socioeconomic and epidemiological transition [3]. Relief of stress and regular aerobic exercise are employed as general non drug therapeutic intervention in all patients with hypertension [4].

In the study of hypertension, cold pressor test, introduced by Hines and Brown [5,6] was employed to measure the cardiovascular reactivity [6,12]. The persons hyper-reactive to cold pressor test are susceptible for early onset of hypertension [7-11]. We tested whether regular practice of Bhramari pranayama for 3 months can reduce the cardiovascular hyper-reactivity.

For the present study, subjects selected were healthy, sedentary, nonsmoker- first year medical students of Shyam Shah Medical College, Rewa (M. P.) [age group 18 to 24 yrs] with no cardio respiratory disorders. Total subjects were 54 (32 females and 22 males). Study design chosen was pre and post test and we included only the experimental group.

Blood pressure was measured in supine posture by Sphygmomanometer [12].

For cold pressor test, a thick walled thermocol box measuring 38 cm × 26 cm × 18 cm, closed from all sides, was used. A hole was made in the centre of the top of the box to allow entry to one hand of the subject. Another small hole was made at the corner of the top of the box for laboratory thermometer. Before starting the experiment the box was filled a mixture of ice and water and the laboratory thermometer was placed such that its mercury bulb was immersed in the mixture of ice and water [8].

Temperature inside the box was measured about 3^°-4^° C. The hand was immersed in cold water up to the wrist for one minute (cold stress). An elevation above the basal level of more than 20 mm of Hg in systolic or of more than 15 mm in diastolic was considered as hyper-reactive response [13].

We made subjects to perform Bhramari Pranayama. Volunteers performed expiration (Rechak) after inspiration (Poorak) and to produce sound like flying wasp during expiration [14].

First of all detailed history and the general examination of all subjects was done and then casual BP was recorded. For 90 days they performed Bhramari pranayama daily. The schedule for pranayama was as follows:-

Morning: - Performed 15 times and relaxed.

Evening: - Performed 15 times and relaxed.

Pranayama was performed in empty stomach, in morning before breakfast and in evening before dinner [15]. Before and after pranayama 5 min relaxation posture was maintained.

Statistical analysis was done by students paired t test, using SPSS software version 11.

Our results showed that Bhrmari pranayama(a type of slow breathing) caused significant reduction in the cardiovascular hyperreactivity There was no significant change in basal BP but BP rise after 1 min cold stress showed a significant reduction. Initially mean systolic BP after 1min cold stress was 139 ± 8.83 mm Hg which reduced to 134 ± 5 mm Hg (t = 2.94, p< 0.01), while diastolic blood pressure reduced from 91 ± 7.5 mm Hg to 88 ± 4.42 mm Hg (t = 4.74, p<0.01). Also initially the rise in systolic blood pressure due to cold stress was 19.24 ± 4.17 mm Hg that became 15.71 ± 2.85 mm Hg with (t = 6.4, p<0.01), and initial rise in diastolic blood pressure was 14.67 ± 2.85 mm Hg which became 11.62 ± 1.86 mm Hg (t = 5.6, p< 0.01)(Tables 1-5).

Earlier study showed a significant reduction of blood catecholamine level in subjects following the practice of shavasana for 3 months [16]. In this study, significant reduction in BP after cold stress was noted which might be due to low catecholamine in blood.

Study to evaluate the effects of slow breathing training, Bhramari pranayama on cardio-respiratory system modulation in patients with essential hypertension reported a reduction in SBP, DBP and mean arterial pressure (MAP); a decline in respiratory rate, increase in tidal volume and thoracic expansibility [17]. Present study corroborates the results of the previous study and we noted reduction in blood pressure produced due to cold stress.

Table 1: No. of Hyper-reactor Subjects. Out of 54 subjects, 21 subjects were hyper-reactor to Cold Pressor Test.

Table 2: Table Showing Basal Blood Pressure and effect of Cold Stress on Basal Blood Pressure with their Mean Value & Standard Deviation.

Table 3: Table showing changes in blood pressure in mm Hg during cold pressor test in hyper-reactors before and after three months pranayama.

Table 4: Table showing comparison of various Parameters (Pulse Rate, Respiratory Rate) in the hyper-reactor subjects before and after Pranayama.

Table 5: Table showing change in hyper-reactivity to cold pressor test after 3 months of pranayama.

It was also reported that the stress level was reduced after a practice of various pranayamas for 2 months indicating reduction in sympathetic drive and increase in parasympathetic dominance to the heart [18].

As a result of excessive stress, both the cerebral cortex and subcortical areas (the limbic system and the hypothalamic areas) become disturbed. These emotional disturbances ultimately lead to changes in functions of autonomic nervous system [19]. We produced similar autonomic disturbance including cardiac sympathetic activation and parasympathetic withdrawal by application of cold pressor test [20] and found that these disturbances were counterbalanced by doing regular practice of Bhramari Pranayama for 3 months.

Bhramari Pranayama probably relaxes the cerebral cortex (supported by the presence of gamma waves) and by increasing parasympathetic predominance and/or inhibition of vasomotor centre (VMC) in medulla by cortico-hypothalamic descending pathway which was reflected by reduced hyper-reactivity to cold pressor test after 3 months training of Bhramari Pranayama.

We thank Dr. Vidya Garg for her valuable suggestions and whole of the staff of Department of Physiology, S. S. Medical College Rewa.