Yoga and Cardiology
Immediate Effect of Speciﬁc Nostril Manipulating Yoga Breathing Practices on Autonomic and Respiratory Variables
Abstract he effect of right, left, and alternate nostril yoga breathing (i.e., RNYB, LNYB, and ANYB, respectively) were compared with breath awareness (BAW) and normal breathing (CTL). Autonomic and respiratory variables were studied in 21 male volunteers with ages between 18 and 45 years and experience in the yoga breathing practices between 3 and 48 months. Subjects were assessed in ﬁve experimental sessions on ﬁve separate days. The sessions were in ﬁxed possible sequences and subjects were assigned to a sequence randomly.
Each session was for 40 min; 30 min for the breathing practice, preceded and followed by 5 min of quiet sitting. Assessments included heart rate variability, skin conductance, ﬁnger plethysmogram amplitude, breath rate, and blood pressure. Following RNYB there was a signiﬁcant increase in systolic, diastolic and mean pressure. In contrast, the systolic and diastolic pressure decreased after ANYB and the systolic and mean pressure were lower after LNYB. Hence, unilateral nostril yoga breathing practices appear to inﬂuence the blood pressure in different ways. These effects suggest possible therapeutic applications.
In 1895 Kayser first described ‘changes in the amount of blood flowing through the cavernous tissues of the nasal conchae’. This has come to be called the nasal cycle. The cycle was considered an ultradian rhythm during which the patency and efficiency of the right and left nostrils changed alternately with varying periodicity (Stoksted 1953). However the earlier accepted view that 80% of healthy individuals have a regular nasal cycle was re-examined by
a study which used numerical measures of reciprocity and quantified the division of airflow between the nasal passages
over time (Flanagan and Eccles 1997). Hourly measurements of unilateral nasal airflow were made for 8 h in 52 volunteers. A numerical definition of the nasal cycle was derived based on (i) the correlation between unilateral airflows and (ii) an airflow distribution ratio between the two nasal airways. Only 11 of the 52 volunteers had patterns of nasal airflow which met this definition. This was 21% of the volunteers studied. This suggested that earlier descriptions of the nasal cycle as being a regular cyclical henomenon in most healthy individuals required further understanding.
In a different kind of investigation, the time periods of multiple systems during sleep and waking rest were studied in three healthy adults, assessing ten variables which included the nasal cycle (Shannahoff-Khalsa and Yates 2000). Time series analysis detected periods at 115–145, 70–100 and 40–65 min across all variables. Hence at present the concept of spontaneous changes in nasal patency in humans remains a possibility, though the physiological mechanisms underlying this cycle are not clear (Okhi et al. 2005). It is recognized that nasal blood vessels influence nasal airflow and hence nasal airflow is regulated by autonomic and central controls (Eccles 2000).
This is related to the fact that sympathetic nerves supplying the nose are regulated by the hypothalamus and vasomotor areas of the brainstem. Despite this need for clarity in understanding the nasal cycle there is an interest in understanding the physiological changes associated with spontaneous changes in nasal patency and those associated with unilateral forced nostril breathing. For example unilateral forced nostril breathing (UFNB) through the right nostril significantly increased blood glucose while left nostril breathing lowered it (Backon 1988). In a single subject it was seen that right UFNB reduced the involuntary blink rate whereas left UFNB increased involuntary blink rates (Backon and Kullock 1989). Also, right UFNB decreased the intraocular pressure whereas left UFNB increased it.
These findings suggested that right unilateral forced nostril breathing is associated with a generalized increase in sympathetic tone, and can hence be correlated with the ‘active phase’ of the basic rest activity cycle (Werntz et al. 1983). Another study examined the effects of UFNB on the functioning of the heart (Shannahoff-Khalsa and Kennedy 1993). This involved three experiments. For two of them the subjects breathed at the rate of 6 breaths per minute and for the third their breath rate was rapid (i.e., 2–3 breaths/s). Using impedance cardiography it was shown that at a breath rate of 6 per minute, right UFNB increased the heart rate compared to left UFNB, which lowered the heart rate. Also the stroke volume was higher with left UFNB and left UFNB also increased the end diastolic volume.
Apart from the lateralized effects on the autonomic nervous system, recordings of the electroencephalogram (EEG) suggested that nasal patency was inversely coupled to alternating dominance of activity in the two cerebral hemispheres, mediated through the autonomic nervous system (Werntz et al. 1983). However this was not seen in another study. In ten untrained subjects nasal decongestion was altered by having the subjects lie in the lateral recumbent position, occluding the contralateral nostril (Velikonja et al. 1993). Cortical activation and laterality were estimated based on ratios of low beta and high alpha bandwidths, relative to each other and between hemispheres. The study did not support the hypothesis of hemispheric activation correlated with nasal patency in subjects untrained in breathing techniques. Similarly, as for unilateral forced nostril breathing, a study on the immediate effects of ninostril yoga breathing related to the performance in a hemisphere-specific task, also did not support the description of nasal patency being coupled with lateralization of cerebral function. Hence the effects of nostril patency on cerebral hemispheric activation remain unresolved.
In addition to spontaneous shifts in nostril patency and unilateral forced nostril breathing, changes in nostril patency have been induced through yoga practice. The ancient Indian science of Yoga uses voluntary regulation of the breathing to make breathing rhythmic, facilitate relaxation and induce a state of mental calmness (Swami Vivekananda 1973). Some of these breathing techniques involve inhalation and exhalation through one nostril selectively (Swami Muktibodhananda 1999). These yoga breathing techniques allow the effects of selective nostril breathing to be studied, when carried out presumably without effort, for specified periods.
One month of right nostril yoga breathing practiced for a few minutes at a time, four times a day, increased the baseline oxygen consumption by 37% (Telles et al. 1994). Left nostril yoga breathing and alternate nostril yoga breathing also increased baseline oxygen consumption, but the magnitude of change was lesser than for right nostril yoga breathing (i.e., 24 and 18%, respectively). Left nostril yoga breathing also increased the volar galvanic skin resistance (suggestive of a decrease in sympathetic activity). The immediate effects of 45 min of right nostril yoga breathing were compared to those of an equal duration of normal breathing, in another study (Telles et al. 1996). Right nostril yoga breathing increased systolic blood pressure by 9.4 mm Hg, increased oxygen consumption by 17%, and decreased digit pulse volume (suggestive of an increase in vasomotor sympathetic activity) by 45%.
There has been no study comparing the immediate effects of right, left and alternate nostril yoga breathing practiced by the same individuals on different occasions. Hence, the present study was planned to study the effects of these three yoga breathing practices, compared to breath awareness and normal breathing, on autonomic and respiratory variables in normal volunteers.
Keywords Right nostril yoga breathing Left nostril yoga breathing Alternate nostril yoga breathing Unilateral nostril yoga breathing Autonomic and respiratory variable