The Role of Autonomic
Nervous System
in Rapid Breathing Practicesof both frequency and time. Removing the frequencies of
respiration did influence the high frequencies i.e. theparasympathetic activity. The mode of breathing did not
influence low-frequency oscillations (sympathetic ones), andthey persisted during apnea. This study proves theindependence of low-frequency rhythms (sympathetic) from
respiratory activity and suggests that the close correlations
that may exist among arterial pressures, R-R intervals, andmuscle sympathetic nerve activity at respiratory frequencies
result from the influence of respiration on these measures.
These are mediated through vagus. These results suggested
that the correlation between respiration and autonomic
rhythms is limited to parasympathetic rhythms.

Dr K.K. Deepak, MD, PhD
Additional Professor
Department of Physiology
All India Institute of Medical
Sciences, New Delhi

The respiration is a unique physiologic function, which is
automatic. It is normally maintained without volition but could
be modified to great extent by volition. It has an ability tomodulate several visceral functions. The relationship in not
one way, there are several physiological states like pain,
emotion, and cardiovascular challenges that modify the
respiration in a patterned manner. For this reason the
respiration has emerged is an important subject matter forpsychosomatic studies both as dependent parameter and alsoa modifier of psychophysiological states.

Chemically mediated cardiovascular responses induce both
hyperventilation and sympathetic activation. These responses
are likely to have different effects on variability incardiovascular system. The effect of hyperventilation on theinteractions between changes in R-R interval (RR) and muscle
sympathetic nerve activity (MSNA) and changes inneurocirculatory variability has been examined by Van De
Borneet et al (2001) in four conditions: 1) controlled breathing,2) maximal end-expiratory apnea, 3) isocapnic voluntary
hyperventilation, and 4) hypercapnia-induced
hyperventilation. The sympathetic drive to periphery (asmeasured by MSNA) increased by about 70% during apnea.
This did not change during isocapnic hyperventilation but
showed more than double increase during hypercapnic
hyperventilation. The total parasympathetic drive to
myocardium (as measure by HRV of R-R intervals) decreased
during both isocapnic and hypercapnic hyperventilation.
There was intense tachycardia during hypercapnic
hyperventilation. This study categorically shows that
respiration can induce oscillation in various autonomic drives,
which lose their concordance (Van De Borneet et al 2001)
under extremes of physiological conditions. Such changes inphysiological limits may be forming potent stimuli to induce
long-term changes (adaptations?) in the autonomic set-up.

1. The effect of respiration on autonomic rhythms
In the autonomic nervous system various rhythms are present,
these include very low frequencies (0.001 to 0.04 Hz, relates tothermoregulatory cycles), low frequencies (0.04 to .15 Hz,
relates to sympathetic rhythm) and high frequencies (0.15 to
0.4 Hz, relates to parasympathetic rhythm). The relationshipbetween the respiration and parasympathetic is manifested
as sinus arrhythmia , the heightened form of which can beseen during deep breathing. Even at rest this relationship exists
and is mainly due to central spill over of respiratory drive to
cardiac centers in the brain, besides some peripheral factors.
In our autonomic function lab, we are able to quantify theseautonomic rhythms (Deepak et al 1999. Deepak et al 2000,
Deepak et al 1996). Raghuraj and colleagues (1998)
demonstrated that a type of rapid breathing (Kapalbhati)enhances the sympathetic drive to myocardium (Lowfrequency power of HRV), enhanced the sympathovagal
balance towards sympathetic side. This was also accompanied
by decreases in vagal tone (high frequency power of HRV).
While alternating nostril breathing at slow pace did notchange thease autonomic drives significantly.

1.1 Hemodynamic responses
Hyperventilation is a powerful physiological stimulus andhas been used in epileptic patients to induce provocation toprecipitate incipient seizures. Hyperventilation is also wellknown to affect the myocardial electrical activity in subjects
without heart disease. It can produce spasm in patients withangina. The autonomic nervous system appears to play a
mediator’s role in these responses. A Greek study subjected
369 healthy volunteers (200 men, 169 women) to prolonged
hyperventilation (30 breaths/minute for 5 min and 10 min
recovery) under continuous ECG monitoring and to exercise
testing (Alexopoulos and colleagues, 1995). Hyperventilation
resulted in an immediate (within the first min), significant
increase in heart rate, a further small increase at 2nd minute of

Badra et al (2001) studied the influence of three types ofbreathing [spontaneous, frequency controlled at 0.25 Hz (i.e.
15 per minute), and hyperventilation with 100% oxygen] andapnea on R-R interval, arterial pressure, and sympathetic
rhythms (measured by inserting microelectrodes in the muscle,
called muscle sympathetic nerve activity or MSNA) in healthy
young adults. They quantified autonomic rhythms for low(0.05-0.15 Hz) and high (0.15-0.3 Hz, this frequency falls in
respiratory range) frequencies; estimated vagal baroreceptorcardiac reflex gain at low frequencies and muscle sympathetic
nerve spectra. Coherence among signals varied as functions
42

sequences of hypocapnic hyperventilation. In second part ofthe study colonic tone and sensation were assessed duringisocapnic hyperventilation and abdominal compression.
Hypocapnic hyperventilation, but not eucapnic
hyperventilation or abdominal compression, significantly
increased colonic tone and sensitivity to balloon distention
without altering humoral mediators or splanchnic blood
volume. Plasma norepinephrine level increased andsplanchnic blood volume decreased during 5 minutes after
hyperventilation, consistent with homeostatic responses(Bharucha et al 1996). In another study Ford et al (1995) haveshown that Hypocapnic but not isocapnic hyperventilation
produced an increase in colonic tone and phasic contractility
in the transverse and sigmoid regions and an increase in pulse
rate and pulse interval variability. The findings are consistent
with inhibition of sympathetic innervations to the colon or
direct effects of hypocapnia on colonic smooth muscle, or both.
These physiological gut responses suggest that some of thechanges in colonic function are caused by altered autonomic
control mechanisms. It is likely that these effects ofhyperventilation may be mediated from direct effect of CO2
washout on colonic muscle. However, reflex changes from
central autonomic control of colonic smooth muscle may not
be ruled out.

hyperventilation, and a subsequent small decrease in heart
rate at later portion of hyperventilation period. A sudden
reduction of about 20% in heart rate was observed on stoppageof hyperventilation. Males showed slightly higher increase inheart rate then females. The blood pressure showed rises withhyperventilation, with their highest value towards the end.
The double product (heart rate-pressure product) increasedby 43.6% with hyperventilation, a change that was only 19.1%of the respective rate-pressure product observed with exercise.
This study proves that hyperventilation induces tremendous
sympathetic stimulation thus, producing elaborate anddramatic hemodynamic response. The detailed analysis
suggested that the smoking blunts hyperventilation induced
hemodynamic response.

1.2 Local vascular changes
Hyperventilation induced chemoreflex not only induces
powerful generalized autonomic changes but also induces
local circulatory changes. In one study local blood flow inremote organs (the anterior tibial muscle and the skin of thecalf) were measured during 3 minute prolonged
hyperventilation by Steurer et al 1995. Duringhyperventilation, mean muscle blood flow increased in normal
subjects as well as patients of hyperventilation syndrome. Thechanges of skin blood flux during hyperventilation were notsignificant. The blood flow response did not differ significantly
in controls and patients. This is paradoxical response when
we analyze this in light of generalized circulatory responses.
During generalized responses, the blood pressure shoots up
and there is intense sympathetic discharge (Alexopoulos etal, 1995, Van De Borneet al 2001). Possibly the release ofvasoactive substances and/or a stimulation of the autonomic
nervous system could have mediated the response observedby Steurer et al 1995. However it appears that local responses
are compensatory adjustment to generalized changes induces
by integrated autonomic reflexes.

2. Respiratory responses to autonomic challenges
In physiological systems, the two variables can influence eachother depending on time of occurrence. As we know that the
respiration influences the autonomic rhythms, it is also true
the autonomic challenges are able to modify the respiration.
Naschitz et al (2000) studied this equation. They compared
the ventilatory responses to autonomic challenge evoked by
upright tilting. The upright tilting is best-known stimulus toincrease the sympathetic activity. In our lab we havedemonstrated the effect of head-up tilting on theparasympathetic reactivity (Jahan et al 1996). Patients ofchronic fatigue syndrome were tilted on a head-up tilt table
after giving adequate rest in lying posture. During and after
tilt the blood pressure (BP), heart rate (HR), respiratory rate
(RR), and end-tidal pressure of carbon dioxide were measured
The blood pressure, heart rate, respiratory rate, and during
end-tidal pressure of carbon dioxide during lying posture
were similar in both patients and controls. During tilt, patientswith chronic fatigue syndrome developed significantly lower
systolic blood pressure, diastolic blood pressure, and, and an
end-tidal pressure of carbon dioxide. There were significant
increases in heart rate and respiratory rate. The patients ofchronic fatigue syndrome showed intense hyperventilationand postural tachycardia in response to postural stress. Thus,
altered respiratory and cardiovascular responses may form
good objective tests to assess chronic fatigue syndrome which
otherwise is often missed for long period or patient receives
unnecessary diagnostic test drills. This finding also indicates
towards modifiability of respiratory function as a consequenceof sympathetic challenge.

1.3 Gastrointestinal effects
The gastrointestinal system is one system which is consistently
responsive to the stress. Our lab has shown the alteredautonomic functions in the patients of irritable bowel
syndrome (Punyabati et al 2002), non-ulcer dyspepsia (Shelke2001) and duodenal ulcers (Hoq et al 1998). As stated above
the hyperventilation-induced hypocapnia affects
hemodynamic Function. It also affects other organs namely
the colon. Symptoms attributable to hyperventilation arecommon among patients with the irritable bowel
syndrome(IBS). It has been suggested that hyperventilation
may exacerbate the alimentary symptoms of IBS.
Hyperventilation is a one of the regular experiment performedin the physiology classes in undergraduate teaching currently.
Typical colonic sensation is common experience with the one
who has performed hyperventilation. Probably the reduced
carbon dioxide level increases the colonic motility. In an
excellent study, Bharucha et al 1996 has tried to prove therelationship between humoral mediators, splanchnic blood
volume and hypocapnia. In first part of study, colonic tone,
sensation, plasma levels of cortisol, beta-endorphin, selected
gut neuropeptides, norepinephrine, epinephrine, andsplanchnic blood volume were measured during two

3. The emotion-autonomic responses-respiration
relationshipA large body of literature is available to suggest the relationshipbetween emotional exteriorization and respiratory changes.
43

Hyperventilation has been largely considered in theories ofpanic disorder. Wilhelm et al (2001) performed a peculiar
study. They examined the predictive value of psychologicaland physiological parameters pertaining to voluntary
hyperventilation. Physiological responses were recorded in
14 patients of panic disorder, 24 patients of social phobia,
and 24 controls. The subjects/patients were made to exercise
six cycles of 1-minute of fast breathing alternating with 1
minute of recovery, followed by 3 minutes of fast breathing
and 10 minutes of recovery. Speed of fast breathing was kept
at 18 cycles/minute by using audio-pacing, and depth aimed
at achieving an end-tidal pCO2 of 20 mmHg by feedback. These
values were achieved equally by all groups. During fastbreathing, both groups of patients reported more anxiety thancontrols, and their feelings of difficulty in breathing. Skin
conductance declined more slowly in panic disorder patientsover the six 1-minute fast breathing periods. At the end of the
final 10-minute recovery, panic disorder patients reported
more awareness of breathing, dyspnea, and fear of being shortof breath, and their pCO2s, heart rates, and skin conductancelevels had returned less toward normal levels than in othergroups. Their lower pCO2s were associated with a higher
frequency of sigh breaths. The patients of panic disorder andsocial phobia showed more distress than controls to equalamounts of hypocapnia. The patients of panic disorder haddelayed recovery of physiological parameters and symptoms
than social phobia patients or controls. (Wilhelm et al 2001).
Thus, the relationship between respiration and autonomic
goes haywire in patients of panic disorder and social phobia,
the same can be utilized for settling the diagnosis along withclinical symptoms. In another in-flight study on phobiacs,
the respiratory rate and minute ventilation, indicators ofhyperventilation, did not differ between phobiacs andcontrols, however, the phobiacs paused more duringinspiration than did controls. Phobiacs also showed moreskin conductance fluctuations and less respiratory sinus
arrhythmia (Wilhelm and Roth 1988). These results certainly
indicate that monitoring of multiple physiological parametersin the real environment is informative.

harder to imagine the scripts vividly and reported lower levelsof subjective arousal. This study suggests two important
things firstly, there is a definite relationship among emotion,
autonomic responses and respiration; second, the autonomic
responses are important mediator emotion-induced
respiratory changes irrespective of the type of emotions.

4. Mechanisms of integration of respiratory
induced psychosomatic changes and Clinicalapplication
A Russian research investigated the autonomic instability(vegetocirculatory dystonia) and hyperventilation syndrome,
who did not have any detectable organic lesion of nervous
system. The scientists used a complex treatment method,which included the breathing exercises with feedback
mechanisms, the correction of psychosomatic and vascular
disturbances, the massage of neck region and a head,
psychotherapy, angioprotective, vegeto- and psychotropic
drug therapy. The disappearance of acute vascular attacks
and episodes of migraine, the normalization of all breathing
parameters were observed in all 35 patients. The study suggeststhat breathing practices can form a part of management
strategies for illness.
We our selves have carried out a large study to document theautonomic changes during Sudarshan Kriya (a well definedsequence of rhythmic breathing with paced breathing at
varying rates and depths interspersed with definite pauses,
described elsewhere in this book). The results will be publishedsoon. Several beneficial effects have been reported consequent
to rhythmic rapid breathing accompanied by adequate pauses
at varying degrees of breathing rate. This book elsewhere
describes these positive changes. In pursuance tounderstanding of pieces of information cited above thefollowing hypothesis is put forward to explain the beneficial
effects of Sudarshan Kriya. Our physiological systems haveimmense capacity to adapt any intense physiological stimuli
if it falls within the tolerance limits. The body system over a
period attempts to blunt the response. This theory is largely
evidenced by physiological system when they are exposed toaltered environmental adverse situations like high altitude,
chronic hypoxia, chronic thermal changes in the environment.
How the Sudarshan Kriya can reduce stress levels over a
period is an enigma to be answered? It is hypothesized that
repeated episodes of rapid breathing results in hypocapnic
internal milieu. This results in sequences of
sympathoexicitation in a session or may have a repeatedsequence over several sessions (Fig 1).

In an entirely diagonal connotation, enhanced breathing(hyperventilation) forms a part of a fight-or-flight response,and it gets stimulated when the person is extremely agitated.
It is also seen when there are intense negative emotions. A
study using emotional imagery found hyperventilation
responses during imagery of high-arousal scenes. Theseemotional imagery scripts bring about autonomic changes.
These autonomic changes may modulate the hyperventilatory
responses. A research group for stress, health, and well-beingat department of Psychology, University of Leuven has carriedout a research (Van Diest et al 2001) to delineate therelationship between emotional changes and respiratorychanges. They used four emotional scripts—depicting
relaxing, fearful, depressive, and pleasant situations—
without suggestions of autonomic or respiratory responses.
After each imagery trial, participants rated their imagery. The
results showed significant drop in end tidal carbon dioxideduring the fearful and pleasant scripts. In the subjects who
did not imagine concomitant autonomic changes (assuggested), this effect was much smaller. Subjects imagining
scripts without autonomic response information found it

Fig 1
Rhythmic, short lasting hyperventilation efforts within
physiological limits
Repeated episodes of sympathetic excitation
Altered sympathetic reactivity
Better ability to tolerate stress episodes
44

Ford MJ, Camilleri MJ, Hanson RB, Wiste JA, Joyner MJ.
Hyperventilation, central autonomic control, and colonic tonein humans. Gut 1995 Oct;37(4):499-504

Fig. 2
Rhythmic, short lasting hyperventilation efforts
interspersed with recovery pauses

Jahan N. Deepak KK, Kaushal N, Paudel BH. Effect of gradedhead-up tilt on parasympathetic reactivity. Indian J Physiol
Pharmacol, 1996; 40:4, 309-317.

Episodes of sympathetic excitation interspersed withlowered sympathetic tone

Hoq MN, Deepak KK Sharma MP, Bijlani RL Lowered
sympathetic reactivity in patients with non-bleeding duodenal
ulcers. Indian J Gastroenterol 1999;18:112-114

Gradual recovery of sympathetic tone with each episodeNaschitz JE, Rosner I, Rozenbaum M, Gaitini L, Bistritzki I,
Zuckerman E, Sabo E, Yeshurun D. The capnography headup tilt test for evaluation of chronic fatigue syndrome. Semin
Arthritis Rheum 2000 Oct;30(2):79-86

Relaxing yet thinking clearlyThus, the physiological systems are going to oppose thisstimulus and this may result in blunting of sympathetic
response. The repeated episodes of this blunting may extend
to other physiologic situation where sympathetic excitation
plays important role in shaping the manifestation namely,
the stress related sympathoexcitation. Thus, in a controlled
situation, the Sudarshan Kriya may provide antidote to stressby physiologically counteracting the sympathetic effects. In anormal situation (in absence of stress) the practice of rapid
breathing interspersed with adequate pauses of slow
breathing, may provide tool for relaxation and vivid imagery(Fig. 2). How much the suggestibility contributes to these
psychosomatic responses, is a matter of future study. Whatever
the case may be the respiratory rhythm is a powerfulphysiological stimulus, which has a capacity to alter several
psychosomatic functions.

Poliakov VA, Tsverianishvili GK. Psychoautonomic andneurovascular disorders in patients with autonomic vascular
dystonia and the hyperventilation syndrome and methods
for their correction. Zh Nevropatol Psikhiatr Im S S Korsakova
1995;95(4):25-7
Punyabati O, Deepak KK, Taneja Indu, Pujari G, Sharma MP.
Heart Rate Variability in patients with Irritable Bowel
Syndrome. Indian J Physiol Pharmacol 2001, 45: 84.
Raghuraj P Ramakrishna AG, Nagendra HR. Effect of two
related yogic breathing techniques on heart rate variability
Indian J Physiol Pharmacol 1998;42(4)467-472.
Shelke A. Autonomic function in non-ulcer dyspepsia. A
doctoral thesis submitted to All India Institute of Medical
Sciences 2001.

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