Exercise, a major component of a pulmonary rehabilitation program (PRP), is generally well recognized for its clinical utility in the management of patients with chronic obstructive pulmonary disease (COPD). Despite this, many issues remain unresolved, including specific modalities, optimal intensity, interplay among subject characteristics (eg, severity of the diseases and coexisting muscle wasting) on exercise intensity, and the best strategies for reinforcing regular exercise habits.1,2 These issues require further attention when patients are older and more frail, especially for those home-bound individuals whose activity space is limited. qigong (QG) and tai chi (TC) are forms of cultural sport activities that use the principles of traditional Chinese medicine (TCM). They have been reported to be alternative exercises in the rehabilitation of patients with COPD.3 Qigong and TC should not be new to the Western culture because they have been an acceptable component of self-management programs involving other chronic diseases such as fall prevention, cardiovascular diseases, and hypertension.4–6
Qigong and TC have been actively developed over the past 200 years. Although originating from different roots (QG from TCM and TC from martial arts), they share many concepts and techniques, especially in the area of health promotion. According to TCM, “Qi” refers to vital energy traveling along the meridians inside the body to sustain life, while “Gong” literally means regular practice. Free flow of “Qi” is essential for good health, while blockage of it would result in illness. The practice of QG/TC is usually a combination of physical and mental training, emphasizing the following: (1) focusing attention; (2) coordinating breathing with movements; (3) aligning proper posture, especially the spine; (4) interlacing muscle contraction and relaxation in a rhythmic sequence and at a constant rate; and (5) recruiting movements or muscle activities not commonly used in daily activities.7,8
Qigong and TC may serve as a home exercise program after a standard center-based PRP has been completed. This systematic review identified the current evidence published in peer-reviewed journals and conducted a meta-analysis to determine whether using QG/TC resulted in enhanced selected health outcomes compared with conventional exercise programs in patients with COPD.
Two international databases (MEDLINE and EMBASE) and 3 Chinese databases (Wanfang Data China Online Journals–Medicine/Hygiene Series, China Academic Journals–Medicine/Hygiene Series [Qingdao Site], and China Academic Journals–Medicine/Hygiene Series [Beijing site]) were searched for original articles published between 1990 and 2012. The following key words and their corresponding terms in Chinese were used: Qigong OR Qi Gong OR Chi Kung OR Taichi OR Tai Chi OR Tai Ji OR Taiji AND COPD OR chronic obstructive pulmonary disease OR chronic obstructive lung disease OR chronic obstructive airway disease OR emphysema OR chronic airflow limitation OR chronic airway obstruction AND RCT OR randomized controlled trial. Additional terms that defined the Chinese names of the 4 standardized forms of QG—Liuziju (art of expiration in producing 6 different sounds), Baduanjin (8 excellent movements), Yinjinjang (tendon-changing classics), and Wuqinxin (frolics of 5 animals)—were also integrated into the search of the Chinese databases.9 Abstracts were reviewed to screen out duplicated and irrelevant studies. Full-text versions of relevant studies were obtained and reviewed to determine their compliance with the inclusion criteria. Citations in these studies were reviewed for any potential studies that were not identified by the database searches.
The following criteria were applied to determine the eligibility of the randomized controlled trials (RCTs) to be included in the analysis. First, subjects were >45 years of age with a diagnosis of COPD. The disease severity was classified as severe to very severe stages (ie, <50% predicted value of the forced expiratory volume in the first second of expiration [FEV1]) according to the GOLD (Global Initiative for Chronic Obstructive Lung Disease) guideline.10 Second, the principal intervention was QG and/or TC. If QG/TC was integrated with other TCM modalities, such as herbal medicine or acupuncture, the QG/TC component should have involved >50% of the intervention duration. The QG/TC intervention could have been (1) either a component of a conventional PRP or a stand-alone program; (2) either a home or a center-based program; (3) either practiced alone or in a group. For the comparison group, the intervention could involve various aerobic exercises (eg, walking, stationary cycling, or ball games) and/or breathing exercises (eg, diaphragmatic breathing or pursed lip breathing) that are commonly used in a PRP. Third, outcomes included at least one measure commonly reported by a conventional PRP, such as a measure of lung function, exercise capacity, or quality of life scores. Finally, the period for outcomes evaluation was 3 months or greater, and there was at least one followup assessment performed 3 to 6 months postintervention.
Data Extraction and Quality Assessment
Data were extracted independently by the authors. The quality of each of the studies was appraised using the Physiotherapy Evidence Database (PEDro) scale.11 When a study had been registered in the PEDro database, the published PEDro rating was used.
Outcomes data were pooled for meta-analysis only when at least one-third of the included RCTs reported the same outcome variable. The sources for these data were primarily from published reports.12–19 Data collected at baseline and at the longest followup assessment between 3 and 6 months were used. When studies included patients of different age groups and of different disease severities, only data for those patients >45 years of age and with moderate to severe levels of COPD were extracted. The effect size was estimated from the difference between the group means, divided by the variances pooled from both the treatment and control groups. Weighted mean differences and 95% CIs were calculated using Cochrane Collaboration software, Review Manager, Version 4.2 for Windows (Nordic Cochrane Centre, Copenhagen, Denmark). When studies incorporated another control group receiving no active exercise interventions, a separate analysis comparing QG/TC to no exercise was conducted.
There were 37 RCTs identified as a result of the database searches, and 19 of these trials were excluded from the analysis. On the basis of the review of abstracts, reasons for exclusion included duplication in multiple databases (n = 15), trial not started (n = 1), study design did not comply with RCT methodology (n = 2), and trial was of an irrelevant topic (n = 1). For the remaining 18 RCTs, we attempted to retrieve the full-text articles. Another 6 RCTs were excluded at this stage for the following reasons: full-text article was not available,20 confusing data presentation,21,22 QG/TC was not the principal intervention component,23 and the period for outcomes evaluation was less than 3 months for 2 trials.24,25 Finally, 12 RCTs were included in the qualitative synthesis and meta-analysis (Figure 1).12–19,26–29
Characteristics of Included Trials
Four trials were published in English,12,13,26,27 whereas all of the other trials were published in Chinese. However, 7 of the articles in Chinese included an English abstract. All 12 trials were conducted in China or Hong Kong where the major population is Chinese. Five trials were conducted in settings under the care of respiratory specialists,12–15,17 and 3 trials recruited subjects from more than one setting.12,26,27Table 1 shows the demographic characteristics of the subjects, subject allocation, and followup for each trial. The total number of subjects was 1178. Most subjects were older adults (mean age, 68 years), and the ratio of male to female participants was 3.4:1. Six trials used a 2-group design consisting of QG/TC and conventional PRP including exercise. The other 6 trials used a 3-group design that involved QG/TC, conventional PRP including exercise, and a control group (no exercise). All of the QG/TC protocols were included as an additional component to the existing PRP, except in one trial where there was an additional group, QG/TC as a stand-alone program, which resulted in the only 4-group design.15
In total, 494 individuals engaged in QG/TC training, 429 participated in conventional exercise training, and 255 received just health advice and no exercise training. The number of subjects lost to followup was 159. No serious adverse events were reported. Table 2 summarizes the characteristics of the QG/TC and exercise protocols for each trial. The 2 most common forms of QG were Liuzijue (n = 5 trials) and Baduanjin (n = 3 trials). Tai chi was adopted in 4 trials and included 13-Form TC QG, 24-Form Simplified TC, and Chen-Style TC. The most common form of conventional exercise was walking, usually integrated with pursed lip breathing. Both QG/TC and conventional exercise were performed using a similar manner across studies: approximately 30 to 60 minutes per session, not less than 4 times per week, and not less than 3 months. However, only 4 trials reported compliance rates for their respective training protocols.12,13,26,27
Concerning the quality of these selected RCTs, the PEDro scores ranged from 4 to 7, with an average of 5.25. Low levels of achievement were noted in the criteria of blinding (0%-25%), the criteria of allocation concealment (8%), and the criteria of intention-to-treat analysis (25%) (Table 3). Five trials were registered in the PEDro database,12,13,15,26,27 and 4 trials appeared to have concerns about the CONSORT criteria as CONSORT flow diagrams were included in the report.12,13,26,27
Outcome variables commonly reported included FEV1, forced vital capacity (FVC), FEV1/FVC, 6-Minute Walk Test (6MWT), the St George Respiratory Questionnaire, and Chronic Respiratory Questionnaire (Table 4). The following points summarize the results of the 12 RCTs12–19,26–29 included in this review. Qigong and TC consistently resulted in improved outcomes when compared with conventional exercise groups and the control (no exercise) group. Other than selected outcomes for lung function, exercise capacity, and quality of life scores, additional benefits were noted by some studies (Table 4). Liu et al12 reported the level of TNF-alpha, a marker indicating the presence of systematic inflammation, seemed to be stabilized among the QG practitioners, while there were increases among the conventional exercise group and the no exercise group during the 6-month followup.12 These results indicated that QG may have a positive effect on systematic inflammation. Moreover, other than in patients in a stable condition, QG/TC had the potential of being applied to patients with COPD who were recovering from acute exacerbations.14
As only FEV1/FVC ratio and 6MWT were adopted as the outcome measures in more than 33% of studies, the related data were combined for analysis. Quality of life scales were adopted by 5 trials. However, 3 trials used the St George Respiratory Questionnaire and the other 2 trials used Chronic Respiratory Questionnaire, making it hard for pooling the data together. For FEV1/FVC, the weighted mean difference for the mean gain in FEV1/FVC was 0.62 (95% CI, 0.30-0.93) comparing QG/TC and conventional exercise groups (Figure 2). When a comparison was conducted between QG/TC and no exercise groups, the weighted mean difference was 2.90 (95% CI, 2.37-3.43) (Figure 3). For 6MWT distance, the weighted mean difference for 6MWT distance was 12.18 (95% CI, 10.32-14.05) m when comparing the QG/TC and conventional exercise groups (Figure 4). When comparing QG/TC and no exercise groups, the mean value was 37.77 (95% CI, 35.42-40.12) m (Figure 5). Both analyses supported the fact that QG/TC had slightly improved outcomes for relieving airflow limitation and improving exercise capacity of patients with COPD when compared with conventional exercise. The effect size was larger when comparing QG/TC and the no exercise group. However, only in the case of comparing 6MWT distance between QG/TC and the no exercise group was the weighted mean difference of 37.77 m greater than the commonly adopted minimal clinically significant value of 35 m.30
Limitations of this Review
Some of the findings in this systematic review, especially the meta-analysis, should be interpreted with caution. In pulmonary rehabilitation, it is generally agreed that exercise training does not improve lung mechanics. Rather, it is accepted that exercise can optimize the function of other systems so that the effects of lung dysfunction are decreased.31 However, our meta-analysis identified an approximate 3-unit difference in favor of the QG/TC for the FEV1/FVC ratio, which is inconsistent with the generally accepted understanding. This finding is consistent with improvement in lung function by using QG training that has been reported among healthy participants,32 using a slow and deep breathing pattern. This breathing pattern is consistent with QG/TC exercises, and this technique has been proposed as a therapeutic approach to address the air-trapping and airflow limitation caused by COPD.33
There are several limitations of this review. First, data were not pooled from all of the trials. For example, only 3 trials contributed to the calculation of the difference previously mentioned in FEV1/FVC ratio between QG/TC and no exercise. Second, the internal validity of the results was affected by the limitations in the methodology of these trials. Third, all trials were conducted in China or Hong Kong and involved only Chinese subjects. This limits generalizing the results to populations in other cultures. Interestingly, a recent study reported improved outcomes for COPD patients from Europe using TC as an exercise training modality.34
Despite the above limitations, these 12 RCTs offered some positive evidence supporting QG/TC having slightly increased benefits compared with conventional exercise. Instead of suggesting it as a replacement for conventional exercise, QG/TC can be considered as an alternative and/or a supplementary format for physical activity, especially for the frail COPD patients. Qigong and TC has the advantage that when patients live in small environments, are homebound, and/or have concerns about the additional cost of using portable oxygen for outdoor exercise, QG/TC can be practiced at home. For exercise to be integrated into the lifestyle of patients, exercise modalities should be fun, meaningful, and affordable. Increased choices definitely mean more flexibility to suit different needs and preferences of individual patients. In addition, in areas where conventional PRP may not readily available to patients,35 QG/TC can be considered as the primary form of exercise, because the effect size between QG/TC and no exercise was favorable for the patients using QG/TC. Qigong and TC group exercise program being led by a peer and audiovisual training materials are readily available and provide valuable instructions. Qigong and TC can be used as a preliminary exercise program before patients begin a formal, supervised PRP. Two of the 4 standardized QG protocols, Liuzijue and Baduanjin, would be appropriate for a preliminary exercise program. Both of these protocols have adequate training materials that are published in Chinese, as well as English.
According to the PEDro scale, there were obvious methodological limitations to the studies included in this review and analysis that threatened internal validity. In future research trials involving QG/TC, investigators are encouraged to address issues such as allocation concealment, blinding, use of intention-to-treat analysis, and improving and reporting compliance to training protocols. Blinding of patients and therapists is difficult to achieve, but investigators can consider blinding the statisticians when data are analyzed. Moreover, investigators should also consider implementing multicenter trials of a larger scale and adoption of a common quality of life scale as an outcome measure. In addition, the analysis should be supplemented with one for subjects who can use a QG/TC protocol.36
To further investigate the therapeutic value of QG/TC in patients with COPD, investigators should research the potential underlying mechanisms that result in benefits from these forms of traditional Chinese exercises. The improvement in outcomes as a result of using QG/TC may likely be explained by a stabilization or reduction of systematic inflammation, as was noted in one of the trials included in this review.12 Similar anti-inflammatory effects of QG/TC were also reported in patients with cancer.37 In the recent decade, there has been a growing recognition of the role of chronic, systemic, and low-level inflammation related to the pathogenesis, as well as complications, in patients with COPD, although the origin of such systemic inflammation remains poorly understood.38–40 Whether exercise can confer an anti-inflammatory effect in patients with COPD is still in the early stages of study.41 Current evidence highlights that the potential benefit may be the result of interactions of various factors, such as type, intensity, and duration of exercise and the presence of muscle wasting.42,43 For example, high-intensity exercise may intensify the systemic inflammatory response and to some extent contribute to the aggravation of muscle wasting, especially among those COPD patients with established cachexia.44,45 On the contrary, in patients with cardiovascular diseases who have a similar component of systematic inflammation, regular, submaximal exercise may induce a decrease in markers of systemic inflammation.46,47 Matching the optimal exercise intensity to the individual patient may be important in managing the impact of systemic inflammation. This concept is consistent with the Yin-Yang concepts of the TCM, which stress the importance of balance and equilibrium. Thus, it is hypothesized that QG/TC, being reported as aerobic exercise of low to medium intensity,48,49 may be a safer exercise for patients with COPD. On the one hand, it can minimize the risk of inducing muscle damage; while on the other hand, it can produce an anti-inflammatory effect. Such an anti-inflammatory effect may be further enhanced by the stress reduction effects through QG/TC practice,50,51 as stress was reported to have an impact on systemic inflammation among patients with COPD.52,53 Future research should be aware of the potential confounding effect of statins, a medication commonly used among COPD patients to control cardiovascular risk and also known to have an effect on inflammatory markers.54
This systematic review provides evidence to support the fact that traditional Chinese exercises like QG and TC could be an alternative and/or supplementary exercise in pulmonary rehabilitation. Compliance to a program of these exercises for no less than 3 months could help reduce airflow obstruction and improve exercise capacity among patients with COPD. This review also indicates that integration of Eastern and Western medicine could produce improved outcomes. In future research, larger-scale, multicenter trials with improved adherence to CONSORT criteria and in-depth investigation into the underlying mechanisms facilitating the physiologic adaptations to exercise training should be conducted.
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