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THEJOURNALOFALTERNATIVEANDCOMPLEMENTARYMEDICINE
Volume 15, Number 7, 2009, pp. 711–717
ªMaryAnnLiebert, Inc.
DOI: 10.1089=acm.2008.0609
Effect of Slow- and Fast-Breathing Exercises on Autonomic
Functions in Patients with Essential Hypertension
1 1 2 1
Monika Mourya, M.D., Aarti Sood Mahajan, M.D., Narinder Pal Singh, M.D., and Ajay K. Jain, M.D.
Abstract
Objectives: Breathing exercises practiced in various forms of meditations such as yoga may influence autonomic
functions. This may be the basis of therapeutic benefit to hypertensive patients.
Design: The study design was a randomized, prospective, controlled clinical study using three groups.
Subjects: The subjects comprised 60 male and female patients aged 20–60 years with stage 1 essential hyper-
tension.
Intervention: Patients were randomly and equally divided into the control and other two intervention groups,
who were advised to do 3 months of slow-breathing and fast-breathing exercises, respectively. Baseline and
postintervention recording of blood pressure (BP), autonomic function tests such as standing-to-lying ratio (S=L
ratio), immediate heart rate response to standing (30:15 ratio), Valsalva ratio, heart rate variation with respiration
(E=I ratio), hand-grip test, and cold presser response were done in all subjects.
Results: Slow breathing had a stronger effect than fast breathing. BP decreased longitudinally over a 3-month
period with both interventions. S=L ratio, 30:15 ratio, E=I ratio, and BP response in the hand grip and cold
pressor test showed significant change only in patients practicing the slow-breathing exercise.
Conclusions: Both types of breathing exercises benefit patients with hypertension. However, improvement in
boththesympatheticandparasympatheticreactivitymaybethemechanismthatisassociatedinthosepracticing
the slow-breathing exercise.
Introduction and BP;10 it decreases sympathetic activity during altitude
induced hypoxia,11 leads to better oxygenation, decreases
utonomicimbalanceisoneofthemultifactorialcauses peripheral chemoreceptor function, and improves exercise
Aof essential hypertension currently.1 The side-effects, performance and baroreflex function and sensitivity.12 Slow
cost of antihypertensive drugs, and nonadherence to medi- spontaneous breathing is independently associated with low
cation have led to the search for a nonpharmacological ap- levels of central sympathetic outflow. Fast breathing, on the
proach to control blood pressure (BP) either as an initial or other hand, is known to increase the BP and the heart rate,
adjunct treatment. Several studies and recent meta-analysis and enhance sympathetic drive to the myocardium. This
13
have demonstrated that lifestyle modifications such as phys- effect has been observed in normal individuals. Other re-
ical exercise, salt restriction, weight reduction, relaxation and searchers, however, have reported no alteration in cardio-
stress-relieving techniques, yoga, meditation (especially vascular parameters or autonomic regulation following the
transcendental meditation), qigong and Zen Buddhist medi- practice of fast breathing.9 Therefore, the effects of fast
tation, biofeedback, and modern practices that involve use of breathing in people with hypertension need to be thoroughly
breathing devices are capable of lowering BP.2–8 evaluated, to ensure its safety in prescribing it to these
One common practice in many of these therapeutic mea- patients.
sures is the use of breathing exercises of different depth and Yogic pranayama involves both slow- and fast-breathing
frequency. Voluntarily controlling the breathing is likely to exercises, whose therapeutic potential needs scientific ex-
bring about alterations in the autonomic responses. The planations. Since there has been no comprehensive system-
frequency of respiration differentially affects the cardiovas- atic study stating and comparing the effects of slow- and
cular system. Slow breathing is generally believed to de- fast-breathing exercises on autonomic functions in patients
crease the basal heart rate, heart rate response to standing,9 with hypertension, the present study aimed to evaluate the
1 2
Department of Physiology and Department of Medicine, Maulana Azad Medical College, New Delhi, India.
711
712 MOURYAETAL.
efficacy and safety of these breathing exercises and also to practice any new yogic technique or exercise other than that
study whether the mechanism involved an alteration of the prescribed during the study period. Groups 2 and 3 patients
sympathetic or parasympathetic reactivity or both. were asked to come daily over a period of 2 weeks (14
working days) to learn the breathing exercise technique.
Methods Once the technique was learned, they were instructed to
The study was conducted in the Department of Physiol- strictly practice the exercises for 15 minutes twice daily 10–12
ogy, Maulana Azad Medical College, New Delhi. It included hours apart, for a period of 3 months. If required, they could
60 patients of either sex in the age group 20–60 years with also use recorded cassettes and time their breathing rate or
essential hypertension attending the medical outpatient de- ask others to time them.
partment and hypertensive clinic of Lok Nayak Hospital, A questionnaire was given to all the patients who were
New Delhi. Ethical clearance from the institute’s committee asked to follow up at the clinic every month to ensure mo-
wasobtainedprior to the initiation of the study. The patients tivation and compliance. The participants were instructed
were graded as stage 1 hypertension according to the that they could practice their breathing exercise any time
guidelines established by the European Society of Cardiol- during the day if they missed the specific time.
ogy, with the systolic BP between 140 and 159mm Hg and At the end of 3 months, BP and autonomic function tests
diastolic BP between 90 and 99mm Hg. Some patients were wererepeatedinthesamelaboratory,atthesametimeforall
without medication, while others were receiving either di- patients, who were advised not to do any breathing exercise
uretics or angiotensin-converting enzyme inhibitors or both onthedayoftesting. All female patients were asked to come
as per standard treatment guidelines.14 preferably in the postmenstrual period for testing. Two (2)
Patients who were not in the age group or stage of hy- patients did not practice slow-breathing exercises regularly
pertension mentioned, with normal autonomic function tests, and 3 could not learn the technique of fast breathing in spite
with a history of smoking, alcohol or drug intake, receiving of all efforts, and 2 patients started dieting. They were not
drugs that alter the heart rate and subjects already per- discouraged from visiting the hypertension clinic or breath-
forming breathing or yogic exercises were excluded from the ing exercise sessions, but their results are not included in the
study. Similarly, patients with secondary hypertension, dia- groups mentioned here.
betes mellitus, chronic breathing disorders, congestive heart Assessment of autonomic function tests
failure, ischemic heart disease, chronic atrial fibrillation,
previous stroke, psychiatric disorder, or clinical evidence of Autonomic function tests were carried out on each patient
malnutrition were not included. around 9 am, at an ambient laboratory temperature between
168Cand208C. They were familiarized with the testing pro-
Study Groups cedures to allay any apprehension or anxiety associated with
The patients with stage 1 hypertension were equally di- the test. The patients had been instructed to come 1–2 hours
vided in three groups, each group comprising 20 patients after a light meal and to refrain from caffeinated drinks.
based on power analysis and previous studies, with or A baseline recording of various autonomic function tests
without medication. was done. One (1) or more than one abnormal test was con-
15
sidered as an indication of autonomic dysfunction. All mea-
Group 1. Patients without intervention. surementsofheartrateweredonefromacontinuousrecording
Group 2. Patients prescribed slow-breathing exercises. of ECGinleadII,andsystemicarterialBPwasmeasuredfrom
Group 3. Patients prescribed fast-breathing exercises. the left upper arm with patients in a sitting position using an
appropriate-size cuff and zero-error mercury sphygmoma-
Experimental Protocol nometerbyauscultatorymethod.BaselineBPwastakeninthe
The patients were informed that they were part of a study yogalaboratorybetween9and10am,after5minutesofrest,1
protocol, and informed consent was obtained. The yoga in- minuteapartuntilthelasttworeadingsdidnotdifferbymore
structor and his team asked each subject to pick up one of the than 10%inbothsystolicanddiastolic BPvalues.The average
60 slips (20 for each group) to allocate the group. The resident value of these measurements represented the BP.
and technician involved in recording BP and autonomic The following autonomic function tests were performed
functions were unaware of the type of breathing exercise according to the well-validated procedures described by
Bannister and Mathias.16 Autonomic dysfunction was clas-
practiced by the patient. The patients were advised not to sified according to results of the standard battery of test.17
discuss this with them or with other patients in the laboratory. These functions have been standardized in the laboratory
Ahealthcheckup,whichincludedhistory,anthropometric and the results are reproducible.
measurements of height and weight, and a detailed general
and systemic examination, was performed before the study Standing to lying ratio (S/L ratio)
was started. Laboratory investigations included estimation
of hemoglobin, blood sugar, lipid profile, blood urea, serum The patient was asked to stand and then to lie on a couch
creatinine, urine routine and microscopic examination, and a without any support. A continuous ECG was recorded from
baseline 12-lead electrocardiogram (ECG). A baseline re- 20 beats before to 60 beats after lying down. The point at
cording of BP and all autonomic function tests mentioned which the patient started to lie down was precisely marked.
later was done. S=L ratio was calculated as the ratio of longest R-R interval
Patients were instructed to continue with their routine during the 5 beats before lying down to shortest R-R interval
lifestyle and diet without further modification and not to during 10 beats after lying down. The maximum ratio of
BREATHING EXERCISES INFLUENCE BLOOD PRESSURE 713
three trials was considered. An S=L ratio of >1 was taken as systolic BP >15mm Hg and diastolic BP >10mm Hg was
normal and <1 is taken as abnormal. considered as normal.21
Immediate heart rate response to standing Experimental protocol for slow- and fast-breathing
(30:15 ratios) exercise
Eachpatient was asked to lie supine quietly on a couch for Patients were called in groups of 4–6, daily at 9 am,ina
5 minutes with sphygmomanometer and ECG leads at- well-ventilated room specially designated for the study with
tached. After a basal recording of the heart rate, the patient an ambient room temperature maintained at 168C–208C, in
wasaskedtostandupimmediately,andchangesintheheart the Department of Physiology of Maulana Azad Medical
rate were noted for 1–3 minutes. A point was marked on the College. They were made to sit comfortably on the floor in
ECGrecord to identify the point of standing. The 30:15 ratio yogic padmasana position to relax for about 5 minutes. The
was calculated by taking the ratio of R-R interval at beat 30 breathing exercise was demonstrated daily for the first few
and at beat 15 after standing. The 30:15 ratio is normally days until the technique to achieve the desired rate was
>1.04 and considered abnormal if <1. learned, perfected, and confirmed by a yogic instructor.
Subsequently, the patients performed the exercises them-
Valsalva ratio selves and the technique was checked on subsequent visits to
the department.
Patients were seated comfortably with the nose clipped
and a mouthpiece inserted between the teeth and lips. The Slow-breathing exercise technique9
other end of the mouthpiece was connected to a mercury
manometer. The patient was asked to breathe forcefully into The patient was first asked to close one nostril with a
a mouthpiece and maintain an expiratory pressure of 40mm thumb and slowly breathe in completely through the other
Hgfor15second. Acontinuous ECG was recorded 1 minute for 6 seconds. This nostril was then closed and the patient
before the maneuver, during the maneuver, and 45 seconds exhaled through the other nostril over a period of 6 seconds.
following strain release. Valsalva ratio was taken as the ratio These steps completed one breathing cycle. An attempt was
of longest R-R interval after the strain to the shortest R-R made to keep the breathing rate about 5–6 breaths per
interval during the strain. A value >1.45 was taken as nor- minute. Such alternate nostril breathing cycles were repeated
mal, between 1.20 and 1.45 as borderline, and <1.20 was continuously for a period of about 15 minutes in one sitting.
considered as abnormal.18 Alternate nostril breathing was chosen because breathing
through a particular nostril can affect autonomic functions.
Heart rate variation with respiration (E/I ratio) Right nostril breathing increases sympathetic activity while
left nostril breathing decreases it.22–25
Resting heart rate was recorded and then the patient was
asked to breathe deeply at a rate of six breaths per minute, Fast-breathing exercise technique9
allowing 5 seconds each of inspiration and expiration. The
expiratory to inspiratory heart rate ratio was calculated as Patients were instructed to breathe quickly and deeply,
the sum of the six longest R-R intervals divided by the sum with an inhalation and exhalation time of 1 second each for 1
of the six shortest R-R intervals. Values were compared to minute, following which they were given 3 minutes of rest.
normal age-related values.19 The procedure was repeated 4 to 5 times over a period of 15
minutes.
Hand grip test Statistical Analysis
The patients held the hand grip dynamometer in the The study outcomes were the average weight, systolic and
dominant hand, compressing it with maximum effort, and diastolic BP changes, heart rate, and BP changes in response to
the tension generated was noted. The maximum of the three various autonomic function tests. The change in all variables
efforts with a 1-minute interval between each was considered at baseline and at 3 months postintervention was evaluated
as maximumisometrictension(Tmax).Thepatientwasthen using analysis of variance (ANOVA). Having established this
asked to maintain a pressure equivalent to 30% of T max for variation, ANOVA for repeated measures was done for each
5 minutes. BP was recorded after every 30 seconds from the group within and between subjects to see the change of 3
nonexercising arm. The rise in diastolic BP just before the monthsinterventionfrombaseline.Inaddition,theintergroup
release of grip was taken as the index of sympathetic re- variation was assessed by using unpaired t test. The difference
sponse. Diastolic BP >15mm Hg was considered as normal, within the group was assessed with the help of paired t test.
11–15mmHgasborderline, and <10mm Hg as abnormal.20
2
Pearson’s w test was done to see whether the three groups
Cold pressor response varied in terms of gender representation.
This was the last of the series of tests performed. One (1) Results
hand of the patient was immersed in cold water at 48C–68C. Patient characteristics
BP was recorded from the other arm before the procedure
wasstarted (baseline) and at 30-second intervals for a period The three groups of patients with essential hypertension
of 2 minutes. Maximum increase in the systolic and diastolic were comparable and balanced in terms of height, weight,
pressure during the test procedure was noted. The rise in and body mass index. There was no difference in the groups
714 MOURYAETAL.
Table 1. Physical Characteristics and Details of Antihypertensive Therapy in the Three Groups of Patients
Parameters Group 1 (n¼20) Group 2 (n¼20) Group 3 (n¼20)
Gender (male=female) 12=810=10 9=11
Height (cm) 158.805.28 161.955.34 158.107.12
Weight (kg) 63.156.94 63.906.83 62.407.74
Weight after 3 months (kg) 62.806.72 63.806.61 61.407.23
2
BMI (kg=m ) 2 24.82.10 24.31.41 24.81.64
BMI after 3 month (kg=m ) 24.72.07 24.31.38 24.51.58
Number of patients on ACE inhibitors 10 8 4
Number of patients on diuretics 10 2 4
Number of patients on ACE inhibitors plus diuretics 0 2 4
Result represents data of subjects who completed the study. All values are meanstandard deviation. Comparison of baseline and
postintervention; *p<0.05 is significant. No significant difference was observed.
BMI, body–mass index; ACE, angiotensin-converting enzyme inhibitor.
basedongender(p¼0.627).Allpatientsingroup1,and60% Effects of treatment and breathing exercises on BP
of patients in each of the other two groups were on antihy- and autonomic functions (intergroup comparisons)
pertensive therapy (Table 1). For the others, breathing exer- One-way ANOVA showed a significant change between
cises were the only form of intervention. groups for both BP and autonomic functions (p¼0.000 for
Baseline BP and autonomic functions all except p¼0.005 for Valsalva response).
Intergroup differences in autonomic function test (after
One-wayANOVAshowednodifferenceinbaselinesystolic treatment and breathing exercises) were seen (Table 2). In all
and diastolic BP in the three groups (p¼0.725, 0.899, respec- groups, between-subjects change from baseline to 3-month
tively) (Figs. 1 and 2). Intergroup comparison using unpaired t intervention was significant (p¼0.000 each). Post-treatment
test confirmed this (p¼0.804, 0.766, and 0.634 for systolic and comparisons in these functions with the slow-breathing
p¼0.882,0.760,and0.653fordiastolicBPbetweengroups1and group were more marked due to improvement in the latter
2, 1 and 3, and 2 and 3, respectively). S=L ratio and 30:15 ratios group.
in groups 1 and 2, E=I ratio in groups 2 and 3, and BP response
to hand grip test (HGT) and cold pressor response (CPR) in all Effects of treatment and breathing exercises on BP
three groups was lower than normal values. Valsalva ratio was and autonomic functions (intragroup comparisons)
normal in all three groups. Baseline autonomic differences ex- No significant change in systolic as well as diastolic BP
isted among the three groups (p¼0.000 in S=L ratio, 0.009 in was recorded in group 1 patients at the end of 3 months of
30:15 ratio, 0.022 for HGT, p¼0.020 for systolic BP of CPR as
shownbyANOVAandsupportedbyttestinTable2).
FIG. 1. Comparison of baseline and postintervention sys- FIG. 2. Comparison of baseline and postintervention dia-
tolic blood pressure (SBP) in three groups of hypertensive stolic blood pressure (DBP) in three groups of hypertensive
patients. (Group 1: Patients without intervention; Group 2: patients. (Group 1: Patients without intervention, Group 2:
Patients prescribed slow-breathing exercises; Group 3: Pa- Patients prescribed slow breathing exercises, Group 3: Pa-
tients prescribed fast-breathing exercises; n¼20 each). All tients prescribed fast breathing exercises; n¼20 each). All
values represent mean with standard deviation. values represent mean with standard deviation.
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