Int J Yoga. 2015 JanJun; 8(1): 62–67.doi: 10.4103/09736131.146067 PMCID: PMC4278137
Effect of yoga regimen on lung functions including diffusion capacity in coronary artery disease patients: A randomized controlled study
Asha Yadav, Savita Singh, KP Singh,1 and Preeti Pai
Department of Physiology, University College of Medical Sciences, Delhi, India
1Department of Medicine, University College of Medical Sciences, Delhi, India
Address for correspondence: Dr. Asha Yadav, Department of Physiology, University College of Medical Sciences, Dilshad Garden, Delhi
110 095, India. Email: email@example.com
Copyright : © International Journal of Yoga
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Lung functions are found to be impaired in coronary artery disease (CAD), congestive heart failure, left ventricular dysfunction, and after cardiac surgery. Diffusion capacity progressively worsens as the severity of CAD increases due to reduction in lung tissue participating in gas exchange.
Aims and Objectives:
Pranayama breathing exercises and yogic postures may play an impressive role in improving cardio respiratory efficiency and facilitating gas diffusion at the alveolocapillary membrane. This study was done to see the effect of yoga regimen on lung functions particularly diffusion capacity in CAD patients.
Materials and Methods:
A total of 80 stable CAD patients below 65 years of age of both sexes were selected and randomized into two groups of 40 each. Group I CAD patients were given yoga regimen for 3 months which consisted of yogic postures, pranayama breathing exercises, dietary modification, and holistic teaching along with their conventional medicine while Group II CAD patients were put only on conventional medicine. Lung functions including diffusion capacity were recorded thrice in both the groups: 0 day as baseline, 22nd day and on 90th day by using computerized MS medisoft Cardiorespiratory Instrument, HYP’AIR Compact model of cardiorespiratory testing machine was manufactured by P K Morgan, India. The recorded parameters were statistically analyzed by repeated measures ANOVA followed by Tukey's test in both the groups. Cardiovascular parameters were also compared before and after intervention in both the groups.
Statistically significant improvements were seen in slow vital capacity, forced vital capacity, peak expiratory flow rate, maximum voluntary ventilation, and diffusion factor/ transfer factor of lung for carbon monoxide after 3 months of yoga regimen in Group I. Forced expiratory volume in 1st sec (FEV1), and FEV1 % also showed a trend toward improvement although not statistically significant. HR, SBP and DBP also showed significant improvement in GroupI patients who followed yoga regimen.
Yoga regimen was found to improve lung functions and diffusion capacity in CAD patients besides improving cardiovascular functions. Thus, it can be used as a complimentary or adjunct therapy along with the conventional medicine for their treatment and rehabilitation.
Keywords: Coronary artery disease, pulmonary function tests, pranayama, yoga regimen
Coronary artery disease (CAD) is defined as impairment of heart function due to inadequate blood flow to the heart against its demand, caused by obstructive changes in the coronary circulation to the heart. Prevalence of CAD is greatly increasing in our country for the last several years and is expected to assume epidemic proportions soon. CAD causes more deaths and disabilities, and incurs greater economic costs than any other illness in the developed as well as developing countries. Projections based on the Global Burden of Disease Study estimate that by the year 2020, the burden of atherothrombotic cardiovascular disease in India would surpass that in any other region in the world.  Studies in India have documented a fivefold higher prevalence of coronary heart disease in the urban as compared to the rural population.
 Over the last three decades, progress in coronary artery bypass grafting and percutaneous interventions has improved the prognosis of CAD, but has not been able to address the basic etiopathology of CAD. [3,4] These are merely providing palliative relief at a high cost.
The lungs are linked in series with the cardiac pump, and they are not only influenced by mechanical alterations in pump function but also by neurohumoral modulators and cytokines involved in the pathogenesis of various heart diseases. [5,6] It has also been proposed that increased levels of circulating cytokines such as tumor necrosis factorα and interleukin6 in CAD patients may induce changes in lung parenchyma.  High left atrial pressure may also induce chronic remodeling of the pulmonary vasculature and its wall thickening. There may also be an enhanced degree of airway reactivity.  Elevation of the capillary pressure causes alveolarcapillary membrane stress failure (i.e., increase in
capillary permeability to water and ions, and disruption of local regulatory mechanisms for gas exchange), leading to a decrease in membrane conductance, an increase in capillary blood volume and subsequent impairment of diffusion capacity. [9,10] Diffusion factor of the lung for carbon monoxide (DLCO) may give an early indication of alveolarcapillary membrane dysfunction in CAD patients as data is lacking in stable patients of CAD.
There is a growing incidence of anxiety and stress related diseases like CAD for which conventional medicine offers only relief from symptom, not from the disease. The new millennium has heralded an unprecedented increase in such disorders and appropriate preventive and remedial measures are needed to be taken. Yogic exercises and pranayama may improve breathing patterns due to which respiratory bronchioles may be widened and perfusion of a large number of alveoli can be carried out efficiently. Yogic regimen may change the milieu at the bronchioles and the alveoli particularly at the alveolar capillary membrane to facilitate diffusion and transport. Studies done by several researchers showed that yogic lifestyle intervention decreases the stenosis of coronary artery, decreases the anginal episodes, retards atherosclerosis, decreases sympathetic activity and improves exercise tolerance. [11,12,13,14,15,16] Adiponectin, interleukin6, and various other cardiovascular disease risk makers are also found to be modified by a shortterm yogabased lifestyle intervention in obese people.  We havenot come across any study showing the effect of a comprehensive yoga regimen on lung diffusion capacity in CAD patients to the best of our knowledge. Reports are available on improvement in lung functions and DLCO after yogic lifestyle intervention in asthma and chronic obstructive pulmonary disease (COPD) patients. [18,19]
As very few studies are available on the effect of yoga practices on lung functions and none on diffusion capacity in stable CAD patients, it is therefore, endeavored to study the effect of yogic regimen and lifestyle modification on lung diffusion capacity and other lung functions in patients with stable CAD.
MATERIALS AND METHODS
A total of 80 patients with stable CAD of age group 45-65 years (55.78 ± 8.95) were recruited from the Outpatient Department of Medicine, Guru Teg Bahadur Hospital, Delhi. All the patients were on regular conventional drug therapy. Most of them were on angiotens in converting enzyme inhibitors of calcium channel blockers along with aspirin. The subjects were selected on the basis of certain inclusion and exclusion criteria.
Angiographically proven CAD Stable CAD for the last 26 years Middle socioeconomic class.
History of any previous illness such as stroke, unstable angina, myocardial infarction, tuberculosis, diabetes mellitus, and renal disease
Any disease known to affect lung function as well as the course of CAD such as asthma and COPD Any history of smoking as it is a confounding factor.
This was a prospective randomized parallel group controlled study on patients with CAD, conducted in the cardiorespiratory lab of the Department of Physiology, University College of Medical Sciences (UCMS), Delhi. The ethical clearance from the Ethical Committee of the institution was obtained before starting the study. All the subjects underwent complete physical and clinical assessment as given in the performa.
Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean blood pressure (MBP) were also recorded in both the groups. Informed and written consent from each subject was taken before recruiting him/her in the study.
Due to the nonavailability (to the best of our knowledge) of any clearcut article on the effect of yogic intervention on DLCO, sample size of 80 was arbitrarily decided on the basis of observations mentioned by other researchers on other parameters of pulmonary function tests (PFTs) such as FEV1, forced vital capacity (FVC), and peak expiratory flow rate (PEFR). After the initial screening for selection criteria, the selected 80 CAD patients were randomized into two groups of 40 each according to a computer generated randomization list (www.randomization.com). After this all the patients in both the groups underwent a baseline recording of PFTs and single breath DLCO in the cardiopulmonary lab of Department of Physiology, UCMS. PFTs were recorded thrice in all the subjects and the best of the three was considered for analysis. After the basal recording Group I CAD patients underwent yoga regimen which included yogic postures, pranayama, dietary modifications and holistic teaching [Table 1] along with the conventional medicine while Group II patients were put only on conventional treatment.
Blinding and masking
As this was an interventional study double blinding was not possible. Here, the statistician who did the randomization, data analyst, and the researcher who carried out the assessments were blinded to the intervention and treatment status of the patients.
Intervention for the yoga group
All the patients in Group I followed yoga regimen daily for 3 months (90 days). A yoga instructor taught them yogasanas and pranayamas daily for 60 min (6 days/week) in the Yoga Lab of the Physiology Department. This was followed by lectures and group discussions. These sessions were aimed at understanding the need for lifestyle change, weight management and stress and anxiety management their diet was also modified and protein rich pulses, green vegetables, juicy fruits, and very less fat were included as per recommended by the dietician. After this they were asked to practice the whole yoga regimen at home for the next 10 weeks. Compliance was checked telephonically once in 3 days and they were called to the lab weekly for the followup.
Intervention for the control group
Group II patients continued their conventional medical treatment after the baseline measurements of lung function tests and they were also put on yoga regimen once they have completed their 3 months followup as controls.
Recording of all the parameters of PFTs in both the groups were done thrice during the study period: First on 0 day as basal recording and then repeat recordings were taken on 22nd day and on 90th day after the
intervention. Different parameters which were recorded were: Slow vital capacity (SVC), FVC, forced expiratory volume in 1st sec (FEV1), FEV1 /FVC ratio, PEFR, maximum voluntary ventilation (MVV),
and single breath DLCO. These lung functions were assessed by using computerized MS medisoft Cardio respiratory Instrument, HYP’AIR Compact model of cardiorespiratory testing machine was manufactured by P K Morgan, India. The data was analyzed and the results were shown on the computer screen. A total of three tests were performed for all the parameters of PFTs and the best of the three fulfilling the criteria of reproducibility and vitality was considered for analysis. Cardiovascular parameters such as HR, SBP, DBP, and MBP were recorded again in both the groups 90 days of intervention.
The data was analyzed intergroup as well as intragroup by using SPSS (Statistical Package for the Social Sciences)is a software used for statistical analysis and is developed by IBM. The baseline values of the two groups were checked for normal distribution by nonparametric KolmogorovSmirnov test. PFTs and
DLCO within the groups repeated thrice were compared by using repeated measures ANOVA followed by Tukey's test. Significance was considered when P < 0.05. For comparison of PFTs and diffusion capacity between the two groups, unpaired Student's ttest was applied. Cardiovascular parameters HR, SBP, DBP and MBP were compared after 90 days of intervention in both the groups by using paired student's ttest.
The mean ± standard deviation of SVC, FVC, FEV1, FEV1 %, PEFR, MVV, and DLCO in Group I CAD patients before yogic regimen and after 22nd and 90th day of yogic regimen are given in Table 1. These subjects showed a significant improvement in almost all the parameters of PFTs and in diffusion capacity
(DLCO). The PFTs of CAD patients who were on conventional medicine only served as controls are shown in Table 2. These patients did not show significant improvement in lung functions on 22nd day and
90th day. Table 3 is depicting the intergroup comparison of these subjects and controls after 90 days of intervention where Group I CAD patients followed yogic regimen along with conventional medicine while Group II patients were only on conventional medicine. Patients on yogic regimen showed significant improvement in SVC, FVC, FEV1, PEFR, MVV, and DLCO.
Group I patients who followed yoga regimen showed significant improvement in all the cardiovascular parameters (HR, SBP, and DBP) after 90 days while Group II patients who were on conventional treatment did not show much improvement [Table 4].
In this study, an improvement in almost all the parameters of PFTs SVC, FVC, FEV1 %, PEFR, MVV, and DLCO was observed in CAD patients after following 3 months of yoga regimen. These improvements are statistically significant in CAD patients on yoga with conventional medicine as compared to patients mon conventional medicine only.
This could be because of reduction of sympathetic reactivity attained with yogic training which may allow bronchodilatation by correcting the abnormal breathing patterns and reducing the muscle tone of inspiratory and expiratory muscles. Due to improved breathing patterns, respiratory bronchioles may be widened and perfusion of a large number of alveoli can be carried out efficiently.  Yogic practice covers the entire field of our existence from physical, sensory, emotional, mental and spiritual to the highest selfrealization. One of the hallmarks of yoga is balance which is of both body and mind. Yoga improves the circulation and there is better perfusion of tissues. It increases the strength of respiratory muscles and reduces sympathetic reactivity thereby helps to reduce stress and anxiety which aggravate the severity of CAD.
The further advantage of yogic breathing lies in the fact that it is more a vertical breathing. By this vertical breathing all the alveoli of both the lungs open out evenly. Due to the even expansions of all the alveoli, a vast expense of alveolar membrane is available for exchange of gases. The larger the surface available for the process of diffusion, the better is the process.  Generally a small portion of lung capacity is been utilized. This inadequate supply of oxygen results in improper waste disposal from the body. The body functions are slowed down and the cells fail to regenerate themselves due to lack of sufficient energy. Pranayama, a well regulated breathing exercise increases the depth of breathing and expands lungs more than normal and recruits previously closed alveoli. Moreover, endurance power of the lung muscle also improves after adopting yoga. 
Ornish et al. showed short term and long term benefits of lifestyle changes (without using cholesterol lowering drugs) on coronary lesions and clinical manifestations of CAD.  Manchanda et al. showed similar benefits in Indian patient population in both these studies, number of subjects were small.  Recent study done in Global Hospital and Research Centre at Mt. Abu on 123 CAD patients and 360 coronary lesions showed a significant improvement not only in hormonal profile (which showed increased levels of endorphins, serotonin and decreased level of catecholamine), lipid profile, quality of life, but also showed a significant regression of atherosclerotic lesions angiographically in the yoga group.  We have also seen significant improvement in cardiovascular parameters such as HR, SBP, and DBP after 90 days yoga regimen in CAD patients.
Very few reports are available which document an improvement in lung functions and prevention of complications after following yoga based lifestyle modification. Our previous pilot study on CAD patients reported an improvement in PEFR, ratio of FEV1 :FVC (FEV1 %), MVV, and forced midexpiratory flow (2575) after following 2 weeks of pranayama breathing exercises.  The limitation of this study were that the sample size was small, patients performed only pranayama and DLCO could not be recorded. In the present study, the subject size was bigger and they followed a proper yoga based lifestyle which included yogic postures, pranayama, diet management along with holistic teaching for a longer duration, that is, 3 months. Yogic exercises and pranayama may improve lung functions and prevent serious cardio respiratory complications by emphasizing optimal physical and mental conditioning. Yogic lifestyle modification therapy can be used as an adjunct to pharmacological treatment in CAD patients to achieve optimal results.
Strength of the study
Strength of our study is that it is first randomized control trial depicting the improvement in PFTs especially in diffusion capacity after following a longer duration of yoga regimen (3 months) under the guidance of a yoga instructor. Cardiovascular parameters HR, SBP, DBP and MBP were compared after
90 days of intervention in both the groups by using paired student's Ttest.
Limitations of the study
We have recruited CAD patients irrespective of their gender so the differences on the basis of gender have not been seen in this study. Cardiovascular parameters such as HR, SBP, DBP, and MBP were recorded before and after intervention but the correlation between respiratory and cardiovascular parameters were not done in this study.
In spite of tremendous advancement in medical technology conventional medicine has proved ineffective in tackling many disorders which have psychosomatic origin. Complementary therapy like yogic exercises and pranayama breathing can be encouraged in CAD patients for their treatment and rehabilitation.
The study was sponsored by grants in aid from Central Council for Research in Yoga and Naturopathy (CCRYN), Department of Ayush, Ministry of Health and Family Welfare, New Delhi. We express our sincere gratitude and thanks to all our patients for keeping faith in us and following the yogic regimen as instructed.
Source of Support: Nil
Conflict of Interest: None declared.
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Effects of yoga training in patients with chronic obstructive pulmonary disease: a systematic review and meta-analysis
Xun-Chao Liu1,2*, Lei Pan3*, Qing Hu2, Wei-Ping Dong2, Jun-Hong Yan4, Liang Dong1
1Department of Respiratory Medicine, Qilu Hospital, Shandong University, Jinan, Shandong 250012, China; 2Department of Respiratory Medicine, Heze Municipal Hospital, Heze, Shandong 274031, China; 3Department of Respiratory and Critical Care Medicine, 4Department of Clinical Medical Technology, Affiliated Hospital of Binzhou Medical University, Binzhou, Shandong 256603, China
*These authors contributed equally to this work.
Correspondence to: Liang Dong, MD. Department of Respiratory Medicine, Qilu Hospital of Shandong University, 107# Wenhua Xi Road, Jinan
250012, China. Email: firstname.lastname@example.org.
Introduction: Currently, several studies have assessed the effect of yoga training on the management of chronic obstructive pulmonary disease (COPD), but these studies involved a wide variation of sample and convey inconclusive results. Hence, the present study was performed a systematic review and meta-analysis to investigate the efficacy of yoga training in COPD patients.
Methods: PubMed, EMBASE, the Cochrane Library, Google Scholar, and ClinicalTrials.gov databases were searched for relevant studies. The primary outcomes were forced expiratory volume in one second (FEV1), FEV1% predicted (% pred). Secondary outcomes included 6-min walking distance (6 MWD), arterial oxygen tension (PaO2), and arterial carbon dioxide tension (PaCO2). Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated, and heterogeneity was assessed with the I2 test.
Results: Five randomized controlled trials (RCTs) involving 233 patients fulfilled the inclusion criteria. Yoga training significantly improved FEV1 (WMD: 123.57 mL, 95% CI: 4.12-243, P=0.04), FEV1% pred (WMD: 3.90%, 95% CI: 2.27-5.54, P<0.00001), and 6 MWD (WMD: 38.84 m, 95% CI: 15.52-62.16, P=0.001).
However, yoga training had no significant effects on PaO2 (WMD: 1.29 mmHg, 95% CI: –1.21-3.78, P=0.31) and PaCO2 (WMD: –0.76 mmHg, 95% CI: –2.06-0.53, P=0.25).
Conclusions: The current limited evidence suggested that yoga training has a positive effect on improving lung function and exercise capacity and could be used as an adjunct pulmonary rehabilitation program in COPD patients. However, further studies are needed to substantiate our preliminary findings and to investigate the long-term effects of yoga training.
Keywords: Chronic obstructive pulmonary disease (COPD); yoga; pulmonary function; meta-analysis
Submitted Feb 18, 2014.Accepted for publication May 13, 2014. doi: 10.3978/j.issn.2072-1439.2014.06.05
View this article at: http://dx.doi.org/10.3978/j.issn.2072-1439.2014.06.05
Chronic obstructive pulmonary disease (COPD) is an important cause of morbidity and mortality and poses a major public health problem. By 2020, COPD is predicted to rank as the third leading cause of death worldwide, whereas its social burden will rank fifth (1-3). COPD is characterized by irreversible airflow obstruction, a gradual decline in lung function, loss of lung tissue, reduced quality
of life, and high rates of mortality. The Global Initiative for Chronic Obstructive Lung Disease (GOLD) management includes a reduction in symptoms, complications, and exacerbations, improved exercise tolerance, improved health status, and reduced mortality (2). Recent evidence-based clinical practice guidelines and statements have shown that pulmonary rehabilitation is widely accepted as the most effective non-pharmacotherapy in the management of COPD (4). Research have indicated that various exercises, such as upper extremity exercise (5), Tai Chi (6), and yoga training (7), can relieve dyspnea, improve lung function, and improve the quality of life of COPD patients. Furthermore, a physical therapist-assisted intensive flexibility training that focuses on stretching and rib cage mobilization can significantly improve 6-min walking distance (6 MWD) (8).
Yoga originated in ancient India, and may denote the union between the individual self and the transcendental self. The body’s organs and systems are cleansed through asanas (postures) and pranayama (controlling the breath). Along with meditation, yoga asanas and pranayama have become popular in the West, and the practice of yoga has become “westernized.” Postures are taught as ends in themselves, that is, to heal an illness, reduce stress, or to look better (9). Yogic exercises have been shown to have positive effects on people with asthma (10,11), cardiac diseases (12), diabetes (13), tuberculosis (14), depressive disorders (15), osteoarthritis (16), and pleural effusion (17).
A number of clinical trials have suggested that yoga training may improve the pulmonary function of patients with COPD (18,19), but the quality of these studies have not been evaluated systematically. Therefore, we undertook a s y s t e m a t i c r e v i e w a n d m e t a - a n a l y s i s o f a v a i l a b l e randomized controlled trials (RCTs) to assess the efficacy of yoga training on pulmonary function and other clinical endpoints in patients with COPD.
Data sources and search strategy
Th e f ol low in g e lec tron ic da ta ba se s w ere se ar ch ed : PubMed, Embase databases, Cochrane Central Register of Controlled Trials, Google Scholar, and ClinicalTrials. gov (until Jan 2014). The employed keywords were “yoga” and “COPD,” or “yoga” and “COPD”. The searches were limited to English publications in humans as well as RCTs. Bibliographies of all potentially relevant studies, articles (including unpublished data and meta-analyses), and international guidelines were manually searched. Furthermore, we also attempted to contact the authors of potentially relevant studies to obtain additional information.
The following inclusive selection criteria inPICOS order involved the following: (I) population: patients with COPD; (II) intervention: yoga training with or without other
treatments; (III) comparison intervention: any type of control; (IV) outcome measures: the primary outcomes were forced expiratory volume in one second (FEV1) and FEV1% predicted (% pred), whereas secondary outcomes included 6 MWD, arterial oxygen tension (PaO2), and arterial carbon dioxide tension (PaCO2); and (V) study design: RCT reported in a full paper article.
For each candidate article, Xun-Chao Liu and Lei Pan recorded the characteristics of the patients being studied, i.e., first author, year of publication, COPD stage, sample size of the study population (intervention/control), grade, staging, age, study design, Jadad scale, interventions (i.e., style of intervention, training frequency, exercise time, and duration), outcome parameters, and their results. Liang Dong checked all of the data. Disagreements were resolved by discussion.
Quality assessment and risk-of-bias assessment
The methodological quality of each research was evaluated using the Jadad scale (20). A score ≤2 indicates low quality, whereas a score ≥3 indicates high quality (21). The risk of bias was assessed using the Cochrane Handbook for Systematic Reviews of Interventions (http://ims.cochrane.org/revman). Two authors (Xun-Chao Liu and Lei Pan) subjectively reviewed all studies and assigned a value of ‘high,’ ‘low,’ or ‘unclear’ to the following: (I) selection bias (was there adequate generation of the randomization sequence? was allocation concealment satisfactory?); (II) blinding (i.e., performance bias and detection bias) (was there blinding of participants, personnel, and outcome assessment?); (III) attrition bias (were incomplete outcome data sufficiently assessed and dealt with?); (IV) reporting bias (was there evidence of selective outcome reporting?); and (V) other biases (was the study apparently free of other problems that could place it at a high risk of bias?).
This systematic review and meta-analysis is reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement (22). We used Revman version 5.1 software for all data and statistical analyses. For continuous outcomes, the pooled mean difference was calculated by using the weighted
Articles identified through database
Additional articles through other
Excluded based on the
titles and abstracts (n=2)
Potentially relevant articles screened (n=9)
Reason for exclusion:
study design (n=4)
Studies included in qualitative synthesis (meta-
analysis) (Randomized controlled trials=5)
mean difference (WMD). Heterogeneity was assessed with the I2 statistic and defined as low (I2≤25%), moderate (25%<I2≤50%), or high (I2>50%) (23,24). A random-effects model was undertaken whether heterogeneity was high or not. Potential publication bias was not assessed because of the limited number of studies (<10) included in each analysis. A P value of <0.05 was considered statistically significant. The overall treatment effect was compared with its minimal clinically important difference (MCID).
Figure 1 shows the study search process according to PRISMA guidelines (22). Of the 11 studies retrieved from the initial search, six met our inclusion criteria (7,18,19,25-27), but one study was excluded upon secondary analysis (27). The reasons for exclusion are presented in Figure 1. Finally, five RCTs, which had a combined cohort size of
233 participants, were selected for this meta-analysis, and their main characteristics are presented in Table 1. The sample size per RCT ranged from 30 to 100. These studies were published between 1978 and 2012, and their duration ranged from 12 weeks to 9 months. Four RCTs reported FEV1 (18,19) or FEV1% (7,25), and two RCTs reported
6 MWD (7,25). Meanwhile, two RCTs reported PaO2
and PaCO2 (18,19). The mean Jadad score of the studies included was 2.4 (SD=0.89). The risk of bias analysis is presented in Table 2.
Two RCTs reported primary outcomes as FEV1 (18,19), and another two RCTs reported FEV1% pred (7,25). The aggregate results of these studies suggested that yoga training was associated with a significant improvement in FEV1 [WMD: 123.57 mL, 95% confidence interval (CI): 4.12-243, P=0.04] (Figure 2) and FEV1% (WMD:
3.90, 95% CI: 2.27-5.54, P<0.00001) (Figure 3). The
test for heterogeneity was not significant (FEV 1 : P for heterogeneity=0.68, I 2 = 0%; FEV %: P for heterogeneity=0.39, I2=0%). We subsequently performed sensitivity analyses to explore potential sources of heterogeneity. The mean changes of FEV1 were greater than the MCID (>100 mL) (28).
Meanwhile, two RCTs reported results in terms of 6 MWD (7,25). The aggregate results of these studies suggested that yoga training was associated with a statistically significant improvement in 6 MWD (WMD: 38.84 m, 95% CI: 15.52-
62.16, P=0.001). The results for the heterogeneity test was not significant (P for heterogeneity=0.08, I2=67%) (Figure 4). Subsequently, the mean changes of 6 MWD were greater than the MCID (>26 m) (29). Two RCTs reported PaO2 and PaCO2 (18,19), and these studies suggested that yoga training was not associated with a significant difference on PaO2 (WMD: 1.29 mmHg, 95% CI: –1.21-3.78, P=0.31) or PaCO2 (WMD: –0.76 mmHg, 95% CI: –2.06-0.53,
|Table 1 Characteristics of randomized controlled trials included in the meta-analysis|
|Patients No. (I/C), Age (years), Form or style Study design/ First author Protocol Duration
Grade, Staging (Mean, I/C) Yoga group Control group Jadad score
|Donesky- 29 (14/15), Stable, 69.9±9.5 Pranayama, Usual-care 60 min/per time 12 w RCT/2
Cuenco NR asana control 2 times/w
|Soni 60 (30/30), Stable, 30-60 Pranayama, Conventional 45 min/d 2 mon RCT/2
et al./2012 Mild or Moderate asana treatment
|Kulpati 75 (25/50), NR, NR 50.6/48.65 Pranayama Conventional 30 min/per time 12 w RCT/2
et al./1982 treatment 2 times/d and breathing
|Tandon 24 (12/12), Stable, <65 Yogic Physiotherapy 60 min/per time 9 mon RCT/2
et al./1978 NR breathing breathing 1-4 w: 3 times/w; exercises exercises 5-8 w: 2 times/w; and postures 9 w-9 mo: 2 times/w
|Katiyar 45 (23/22), Stable, 53.3/51.1 Pranayama Usual-care 30 min/per time 3 mon RCT/4
et al./2006 severe control 6 times/w
|I/C, intervention/control; RCT, randomized controlled trial; NR, not reported.|
|Table 2 Assessing risk of bias|
|Sequence Allocation Incomplete outcome Selective outcome Free of other
generation concealment data addressed reporting bias
|Donesky-Cuenco et al./2009 Unclear No No Yes Yes Unclear|
|Soni et al./2012 Unclear No No Yes Yes Unclear|
|Kulpati et al./1982 Unclear No No Yes Yes Unclear|
|Tandon et al./1978 Unclear No No Yes Yes Unclear|
|Katiyaret al./2006 Yes No Yes Yes Yes Unclear|
P=0.25). The test for heterogeneity was not significant
(PaO : P for heterogeneity=0.47, I2=0%; PaCO : P for heterogeneity=0.23, I2=31%) (Figures 5,6).
of COPD treatment (30-33). Studies have indicated an increase in tidal volume and FVC, reduction in respiratory
rate, increase in FEV , FEV %, maximum voluntary
This study is the first meta-analysis to evaluate the effects of yoga training on COPD patients. Our results suggested that yoga training has a positive improvement effect on lung function and exercise capacity and could be used as an adjunct pulmonary rehabilitation program for COPD patients.
Currently, no drugs could hinder the progress of COPD, but lung training and pulmonary rehabilitation have been shown to reduce disability in many chronic respiratory diseases and have become valuable means
ventilation, and breath holding capacity after short-term yoga practice (34,35). Furthermore, studies suggested that yoga training may improve exercise capacity, prevent lung function decline, improve quality of life, and reduce dyspnea in patients with COPD (36,37). However, these studies did not provide adequate data or sufficient clinical evidence to support the beneficial effects of yoga training on these relevant findings.
Our results suggested that yoga training improved FEV1 or FEV1% pred in four studies (7,18,19,25). However, the results required comparison with the MCID, which is defined as the smallest change in the measurement used to evaluate the clinical significance of intervention effects. The
Figure 2 Meta-analysis of randomized controlled trials evaluating effects of yoga training on FEV1 by the random-effects model. FEV1,
forced expiratory volume in one second.
Figure 3 Meta-analysis of randomized controlled trials evaluating effects of yoga training on FEV1% by the random-effects model. FEV1,
forced expiratory volume in one second.
Figure 4 Meta-analysis of randomized controlled trials evaluating effects of yoga training on 6WMD by the random-effects model. WMD, weighted mean difference.
Figure 5 Meta-analysis of randomized controlled trials evaluating effects of yoga training on PaO2 by the random-effects model. PaO2,
arterial oxygen tension.
Figure 6 Meta-analysis of randomized controlled trials evaluating effects of yoga training on PaCO2 by the random-effects model. PaCO2,
arterial carbon dioxide tension.
MCID is claimed to be a 100-mL change in FEV1 from baseline (28), and the 123.57 mL increment in FEV1 in our study is greater than the MCID. This result indicates that yoga training can have a clinical effect on COPD patients. Unfortunately, we failed to compare further the FEV1% pred with the MCID because of insufficient available data. Our meta-analysis also found that yoga training statistically improved 6 MWD in patients with COPD. The 38.84 m change for 6 MWD was greater than the MCID (≥26 m) (29). However, our meta-analysis showed that yoga training did not affect arterial blood gas analyses, which included PaO2 and PaCO2. PaO2 and PaCO2 are affected by various factors, such as temperature factors (38), breathing frequency (39), varying levels of light intensities (40), sampling location, blood volume, and inspection time (41). We believed that PaO2 and PaCO2 are not suitable evaluation parameters of yoga training in COPD patients because of their instability. However, further study is needed to investigate this noteworthy topic.
The mechanisms of yoga training responsible for its beneficial effects that differ from other forms of exercise have yet to be elucidated. Several factors may be responsible for the beneficial effects seen in the patients undergoing yoga training aside from exercises (42-45). Yoga training aids in toning up general body systems (42), increasing respiratory stamina, relaxing chest muscles, expanding the lungs, raising energy levels, and calming the body (43). Additionally, yoga training improves blood circulation and increases the strength of respiratory muscles (44). Finally, yoga training also helps patients to breathe more deeply by utilizing the shoulder, thoracic, and abdominal muscles efficiently (45).
Yoga training can provide a complementary strategy for patients with COPD. Apart from relaxing tense muscles, yoga can also alleviate mental pressure (15). However further studies are needed to examine the effectiveness of
yoga training compared with other breathing exercises. Our study showed follow-up durations that ranged from
12 weeks to 9 months, and the long-term effects of yoga training optimal exercise duration currently remain unknown. Future research should focus on optimizing training intensity, duration, and frequency. Moreover, it should be emphasized that the severity may greatly influence the effect of yoga. However, not all studies have noted the severity of COPD patients. Further research should focus on the relationship between the severity and efficacy in COPD patients, which can help to determine the best yoga exercise prescription and the best suitable patients. Finally, most studies lacked other physiological outcome measures, such as inflammatory biomarkers, continuous monitoring, sensitive measures of change, and peripheral muscle strength. Further studies that focus on these will enrich clinical evidence regarding yoga.
Several limitations are identified in our study. First, included trials significantly varied in terms of interventions protocol, duration, patient populations, severity, and study quality, which limit the conclusive extent for the overall effectiveness of yoga training on FEV1, FEV1% pred, 6 MWD, and blood gas analysis in COPD patients. Secondly, our analysis is based on only five RCTs, and only a maximum of two studies were available for the main outcomes. In addition, studies ranged from 1978 to 2012 hence it encompasses a wide time frame which may affect
the results as over the years better drugs are available such anticholinergics to ameliorate symptoms of COPD and more standardized and accurate methods are available to measure some clinical endpoints such as lung function and arterial blood gas analysis. Moreover, these studies have a wide variation in patient populations. The smaller sample size of trials may have significantly overestimated the treatment effect. Finally, several missing and unpublished data may lead to bias.
Journal of Thoracic Disease, Vol 6, No 6 Jun 2014
Our meta-analysis suggested that yoga training that lasts from 12 weeks to 9 months may improve lung function and functional exercise capacity in patients with COPD compared with conventional therapy. Moreover, we suggest that yoga could be a useful adjunct pulmonary rehabilitation program for COPD patients. To help clarify the issue, further rigorously designed, larger-scale trials should be conducted to evaluate the long-term effects of yoga training in COPD patients.
We would like to thank the authors of the original studies included in this meta-analysis.
Disclosure: The authors declare no conflict of interest.
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