This study found that similar improvements in asthma symptoms, reliever use, and ICS dose were achieved in subjects with mild to moderate asthma using a technique which focused on the nasal route of breathing, hypoventilation, and breath holding, and a breathing technique incorporating non‐specific upper body manoeuvres. Importantly, these changes were achieved without impacting negatively on underlying disease control, as measured by lung function and airways responsiveness. Devising a credible control for complementary medicine interventions has been acknowledged as a difficult task,12,13,14,15
and previous studies examining breathing exercises for asthma have used a variety of control arms including asthma education and relaxation, but this approach has limited the conclusions which can be drawn about the efficacy of the breathing technique itself. Instead, we used a second breathing technique for which there was no previous evidence of efficacy in a randomly selected asthma population, and in which there was no attempt to modulate pattern of breathing. Unlike previous studies,16,17,18,19,20,21,22,23
we also matched all process elements of the two interventions, including the instruction about symptom relief, so that the only variable was the exercises themselves. The similarity of the improvements seen in both groups, despite the widely disparate nature of the breathing exercises they were using, suggests that the observed changes were more likely to be attributable to one or more of the shared process
elements—such as the instruction to use the exercises initially in place of reliever for symptom relief—than to the breathing exercises themselves.
Although we found significant improvements in reliever use, some patient centred outcomes and ICS dose, there were no significant changes in physiological parameters. With one exception,18
no previous study of breathing techniques has found an improvement in lung function5
or airway hyperresponsiveness,19
and there is no evidence that upper body exercises such as those used for group B would impact on lung function. Our results confirm no change in end tidal CO2
, as also reported by Bowler et al
While data for end tidal CO2
and mannitol challenge in the present study should be interpreted with caution due to missing data, these findings—together with the measurement of airway resistance by the forced oscillation technique—strongly suggest that the improvements observed with both breathing techniques were not measurably related to physiological changes.
It has also been suggested6
that the failure of previous studies of breathing techniques to demonstrate improvements in lung function was due to a bronchoconstricting effect of deep breaths during PEF monitoring. However, we failed to find evidence that 2 week periods of PEF monitoring were detrimental, with even small improvements occurring in some measures. Our findings therefore suggest that breathing techniques do not mask any benefit or cause deterioration in other measures of asthma control.
Previous studies of breathing techniques have shown a trend towards a reduction in ICS dose. We found a significant and similar reduction in ICS dose in both groups, with no negative impact on other outcome measures. It is unlikely that this was due to improvement in airway inflammation, given the lack of change in indirect airway hyperresponsiveness. However, some of our subjects may have been relatively overtreated with ICS at entry, as many clinicians rely on markers such as reliever use to indicate whether a patient's ICS dose is appropriate. Further, other researchers have been able to reduce ICS doses by approximately 50% in a clinical trial setting in the absence of any other intervention.24
Despite the lack of physiological improvement, any strategy which facilitates ICS reduction has important clinical implications and useful applications.
There are several possible mechanisms to explain the reliever reduction observed in this study. One possibility is that this effect was due to participation in a clinical trial (Hawthorne effect25
). However, this would be an oversimplification given that reliever reduction was substantial (86% by study end) and was sustained over 8 months. For both groups there were more symptom‐free days at baseline (group A: 23.5%, group B: 22.1%) than reliever‐free days (group A: 6.7%, group B: 8.3%). Similar disparities have been observed in other asthma studies,26
suggesting that patients may often use their reliever for prevention rather than actual relief of symptoms. Presumably, any instruction which defers or delays the taking of a β2
agonist will minimise its habitual and pre‐emptory use. Thus, while breathing exercises may not confer any particular physiological benefit, the process of using breathing techniques as first line symptom treatment may allow people to substantially reduce their use of β2
agonist. This itself may be beneficial by reducing adrenergic side effects, by reducing response to allergens, or by reducing mast cell tachyphylaxis.27,28,29
Another possible explanation for the overall improvements is that the subjects recruited were a “special” group in terms of their personality or breathing style. No specific tests of personality, anxiety, or depression were administered. The fact that breathing exercises were mentioned in some recruitment material may have attracted subjects who were more likely to respond to the interventions, enabling both breathing techniques to function as “very active placebos”. However, the baseline clinical characteristics of the subjects from this study, including symptom and reliever frequency, were similar to those from a more conventional clinical trial recently conducted at the same centres.30
While it is possible that the relaxation elements of both interventions assisted in reducing anxiety and hence in reducing the perceived need for reliever, the subscores for the mood domains of the AQLQ (which includes questions about anxiety) were very low in our subjects at baseline, indicating minimal impact of anxiety and—unlike in previous studies16,17,23
—minimal opportunity for improvement in asthma related quality of life. These subscores remained largely unchanged throughout the study, suggesting that the large reduction in β2
agonist use was not primarily due to the relief of anxiety. There has been considerable interest in the concepts of dysfunctional breathing and hyperventilation syndrome,31
but the clinical importance of such conditions in people with asthma has not yet been established. The Nijmegen questionnaire has been used to assess dysfunctional breathing, but was not included in the present study as there is considerable overlap with the symptoms of asthma itself. A previous study of asthmatic patients with high Nijmegen scores showed improved quality of life with a breathing technique similar to our group B intervention, but there was no reduction in reliever use or ICS dose.23
Although some patients in the present study may have satisfied the criteria for hyperventilation, the randomisation process should have ensured that they were equally distributed between both treatment arms.
Although there was little change in AQLQ score, improvements were seen in other patient centred outcome measures including Patient Global Assessment of Control and ACQ scores. These improvements suggest that the subjects' self‐efficacy was enhanced, which may have been due to a reduction in medication facilitated by breathing techniques. While the “ideal” study would include a group of control subjects who were instructed to withhold reliever without any substitute, gaining the agreement of subjects and the approval of an ethics committee would undoubtedly be difficult. In the present study, subjects in both groups were provided with a strategy that offered an alternative to reliever use which they appeared to accept as plausible and credible. We suggest that the combination of these factors enabled patients to reduce their reliever use in the absence of any other change.
In summary, this study shows that two completely different types of breathing techniques, taught by video, can lead to a similar level of improvement in asthma outcomes particularly those relating to the use of a short acting β2 agonist. These improvements are of a magnitude similar to that observed in conventional clinical trials which assess pharmacological interventions to improve asthma control, and are therefore clinically important. The improvement observed was substantial and sustained, but was not associated with a measurable effect on physiological parameters of airway inflammation. Given the magnitude of the differences in content of the two breathing techniques which were used in the present study, it appears likely that the observed clinical improvements were not due to the use of a particular type of exercise but to the process of both routine and as‐required exercises that reinforce a message of relaxation and self‐efficacy and provide a deferral strategy for β2 agonist use. Breathing techniques may be useful in the management of patients with mild asthma symptoms who use reliever frequently, but at present there is no evidence to favour shallow breathing techniques over non‐specific upper body manoeuvres.