Breathing techniques are among the most popular complementary medicine modalities used by people with asthma.^1–,⁴ A Cochrane review concluded that breathing exercises for asthma, such as Buteyko, yoga and diaphragmatic breathing, led to decreased use of short acting β₂ agonists and a trend towards improvement in quality of life, but no consistent evidence of improved disease control such as reduced requirement for anti-inflammatory medication, reduced airway hyperresponsiveness, or improved lung function.⁵ Some proponents of breathing techniques have suggested that the failure to demonstrate improvement in lung function measures such as ambulatory peak expiratory flow (PEF) was due to the deep inspirations and forced expirations required with such monitoring.⁶ Additionally, the Cochrane review⁵ highlighted the need for further studies to evaluate the impact of breathing techniques on symptom free days, physiological measurements, and airway inflammation.

This study was designed to test the hypothesis that breathing techniques aimed at reducing tidal volume and rate of breathing and encouraging the nasal route of breathing would result in greater improvement in asthma symptoms and measures of disease control, and allow a greater reduction of inhaled corticosteroid (ICS) use than non-specific upper body exercises. A secondary hypothesis was that twice daily peak flow monitoring has no detrimental effect on asthma outcomes during treatment with either form of breathing exercise.

METHODS

Study design

The study was a double blind, randomised, controlled, multicentre comparison of two breathing techniques—one (group A) aimed at reducing tidal volume, reducing hyperventilation and encouraging nasal route of breathing, and the other (group B) involving non-specific upper body mobility exercises. After a 2 week run in period on pre-existing treatment, subjects were randomised (fig 1⇓) using computer generated permuted blocks (block size of four). Subjects learned and practised their exercises by video instruction (see details under Interventions section and in table 1⇓). They were asked to practise their routine exercises twice daily (approximately 26 minutes). For symptoms normally requiring reliever, subjects in both groups were advised to use a shorter set of their allocated breathing exercises (3–5 minutes) first and to take reliever if symptoms persisted. Dose reductions in ICS of 50% were attempted at weeks 16 and 22 for eligible subjects (see online supplement).

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Table 1

 Exercise descriptions

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Figure 1

 Schematic of study design. Inhaled corticosteroid (ICS) dose remained constant until week 16, after which two successive dose reductions of 50% were attempted for subjects who satisfied the eligibility for reduction criteria (weeks 16 and 22). *ICS dose reduction if clinically indicated (both groups).

RESULTS

Fifty seven subjects were randomised (28 to group A and 29 to group B). Nine subjects (five from group A and four from group B) withdrew before completion of the study (fig 2⇓). Blinding of randomisation allocation was not broken for any subject. Baseline demographic and clinical characteristics are shown in table 2⇓. At baseline, subjects had mild airway obstruction and used on average 3 puffs reliever/day. Asthma related quality of life was well preserved and was slightly better in group B at baseline (p = 0.0417). There were no significant differences in other variables.

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Figure 2

 Patient disposition.

During the study there was no significant difference between the groups in the self-reported time spent on routine daily exercises (group A: median 12 min/day (IQR 7–20); group B: 16 min/day (IQR 8–20); p = 0.66). Median overall adherence to twice daily electronic monitoring was 62%.

Secondary outcome measures (weeks 1–12)

Reliever use

Both groups had a dramatic reduction in reliever use commencing from week 1 after randomisation (fig 3⇓), with no significant differences between the groups at week 12. The proportion of reliever-free days increased in both groups between baseline and week 12 (group A: median baseline 6.7%, week 12 53.5%, p = 0.001; group B: baseline 8.3%, week 12 55.3%, p = 0.0001) with no significant differences between groups (p = 0.49 at baseline; p = 0.19 at week 12).

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Figure 3

 Reliever use reduction.

Other variables

There was no significant difference between ACQ scores at week 12 (p = 0.234). However, there was a statistically significant improvement in ACQ at week 12 in group B (p = 0.0324) but not in group A (p = 0.49; see online supplement). A significant improvement in ACQ was seen for group B even when the components for β₂ agonist use and lung function were omitted (see online supplement).

There were no significant differences between groups in Patient or Physician Global Assessments at week 12, although Physician Global Assessment improved significantly for group B but not group A compared with baseline (p = 0.0467 and p = 0.073, respectively).

There was no significant difference between groups in clinic FEV₁ at week 12 (p = 0.30), although there was a small reduction in FEV₁ (0.084 l) by week 12 in group B (p = 0.0359). There were no consistent differences between the two groups at week 12 for airway responsiveness to mannitol, or for mean airway resistance before and after deep inspiration. The airway responsiveness data need to be interpreted with caution due to missing data (see online supplement).

There was no difference between the groups at week 12 in volume of deep inspiration and number of breaths per minute (see online supplement), end tidal CO₂, or route of breathing, and no significant changes in any of these measures within either group during weeks 0–12. The end tidal CO₂ and route of breathing data need to be interpreted with caution due to missing data (see online supplement).

DISCUSSION

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–,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–,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.¹⁶ 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–,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 studies^16,17,23—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.