Discussion
The results provided evidence to support the hypothesis that HQG, as an adjunct home exercise program, better maintained the improvement in the functional capacity gained from a pulmonary rehabilitation program among patients with COPD until the 6-month FU than the conventional program. The result was more apparent when the subjects complied with the HQG protocol. This finding is not surprising, because the word gong in Chinese literally refers to ‘‘skills or accomplishment cultivated through committed and regular practice.’’ Participating only in a few sessions of HQG training is not adequate to produce any improvement in health status. Moreover, the effect sizes for functional capacities (i.e., 0.92–0.94) appeared larger than those for the QOL subscales (i.e., all below 0.59). The phenomenon is also
noted in our prior studies, which suggested that it took accumulation of more improvement in physical function over a longer time to make the effect generalized to subjective report of better outcomes among the Chinese population.6,7 Despite the fact that our study had much improvement to address the methodological shortcomings of prior qigong studies (e.g., stricter measures to ensure randomization and
allocation concealment, recruiting more subjects, longer FU period, etc.), there are still limitations that might have confounded the validity of our results. First, our male subjects outnumbered female subjects, which may restrict general- ization of the results to female patients. However, this is characteristic of this patient group in the Hong Kong Chinese population, as males seemed to be more affected or known to
the public health care system than females. Second, the attrition rates for the two groups were high: 27.5% and 30%. This might be due to the fact that our subjects were older and frailer. All were in fact above years 70 of age with FEV1 values below 40% of the corresponding predicted values.
They might suffer other insidious chronic medical diseases or repeated acute COPD exacerbations, which affected their participation. Acute COPD exacerbations, which have an impact on long-term outcomes and the progress of the disease, should have been reported to facilitate result interpretation.
However, as prior consent from patients was not sought and thus approval from related authority, related information through the electronic records of the hospital data system for the ‘‘dropped out’’ and ‘‘loss FU’’ cases could not be validated due to the personal data privacy policy. Fortunately, the attrition rates of the two groups appeared comparable, which suggested that the plausible underlying conditions did not contribute a bias favoring either group. In future research, we recommend inclusion of younger subjects,
preferably with an age range from 60 to 70 years, to minimize the attribution rate. Meanwhile, a system to check possible reasons for attrition should be made available. Third, the rate of withdrawal from the HQG training protocol was also high (17.9%). Although the learning of HQG is easy, our current mode of HQG training, with only four individual training sessions and a set of self-training materials, might not
be adequate for some patients who were slow in acquiring new motor skills. Closer monitoring of their progress in learning and perceived self-efficacy might help identify particular subjects who may need a longer coaching time. Finally, caution must be taken regarding the generalization of results to a non-Chinese population. One of the characteristics of our participants is thatthey had a positive view towards HQG even though they have not had the chance to receive it in the past. This may be due to their values regarding some practices based on TCM. This positive attitude toward the intervention might have contributed to their participation and hence to the outcome. As a result, the results may not be readily applicable to those with a Western cultural background. These people may not have a positive attitude
toward HQG, which is not relevant to their own culture. However, with increasing awareness of and interest in this modality among theWestern population, hopefully similar results
will be obtained among non-Chinese patients in the near future. The basic physiologic mechanism that underpinned the improvement remains unclear. What is certain is that the improvement cannot be explained by ‘‘overload,’’ which is regarded as the conventional exercise training principle. The
‘‘overload’’ principle reflects the concept of intensity, and implies that in order for the muscle to improve in structure and/ or function, it must be taxed beyond a critical level. The metabolic requirement for performing movements of HQG and t’ai chi belongs to a ‘‘low-intensity’’ physical activity. TheMETs is estimated to range from 1.5 to 2.6,32 and the mean of the induced maximum heart rates ranges from 43% to 49% of predicted maximum heart rates. On the other hand, ‘‘highintensity’’ exercise may produce adverse effects, such as muscle wasting and disturbed breathing pattern, which then may reduce exercise capacity among patients with COPD. Therefore, the authors believe that there should be a different physiologic mechanism to explain how HQG improved the functional capacity of the subjects in this study. Physiologic research efforts on ‘‘effects of low-intensity muscle activities on anti-inflammation,’’ ‘‘respiratory sinus arrhythmia,’’ and ‘‘meditation-induced specific brain wave patterns’’ provide hints for future exploration. ‘‘Repetitive low-intensity muscle contractions’’ facilitate the modulation of systemic inflammation by upregulating interstitial interleukin-6.36 Slow breathing, through the ‘‘Respiratory sinus arrhythmia’’ mechanism, produces a downregulating effect on the vagal tone and promotes efficiency in gaseous exchange. Muscles contractions in harmony with slow breathing facilitate venous return to the heart from the periphery through the ‘‘respiratory muscle pump’’ mechanism. Meditation involves internalized focus of attention. It produces specific brain-wave patterns (e.g., higher slow a coherence, increases in left-sided anterior activation, etc.), which are associated with positive mood and improvement in immune function. Moreover, the review of HQG practice among clinical populations suggests that the psychophysiologic outcomes are systemic in nature, which include enhancing circulation, improving ventilation, and strengthening immune responses. These are in line with the current concepts of the development of complementary and alternative medicine. On the other hand, the effect of systemic inflammation on the pathophysiology and morbidity of COPD has attracted increasing concerns. The effect of HQG on COPD is proposed to be directly related to the modulation of systemic inflammation and strengthening ofimmune responses and/or mediated through the enhancement of circulatory function. Following this proposed mechanism,
biomarkers documenting the inflammation such as Creactive protein, interleukin-6, and tumor necrosis factor-a, should be included in future studies.