Slader, Reddel, Spencer, Belousova, Armour, Bosnic-Anticevich, Thien and Jenkins have just published a paper in Thorax
that reports that breathing techniques can substantially reduce medication use by people with mild asthma. Double blind randomised controlled trial of two different breathing techniques in the management of asthma
[Full Paper in pdf
.] Although the participants in the trial cover a wide age-range, the selection criteria included people from the age of 15. The findings of this trial may be of some interest to parents or health professionals who would like to modify the use of medication to the most appropriate level, particularly in young people where the use of medication can cause particular concern to parents.
Summary of the study and results
Slader and her colleagues have published the results of their examination into the impact of breathing techniques on the management of asthma. They reported that breathing techniques cut the use of reliever inhalers by more than 80% and halved the dose of preventer inhaler required in the people with mild asthma who participated in the study.
The researchers compared the impact of two breathing techniques on symptoms, lung function, use of medication and quality of life among 57 adults with mild asthma. The participants, who used a preventer inhaler and required reliever inhaler at least four times a week, were randomly assigned to one or other breathing technique.
One technique focused on shallow, nasal breathing with slow exhalations (Group A), and the second technique used breathing-timing inhalations and exhalations in synch with upper body exercises such as shoulder rotations and arm curls, accompanied by relaxation (Group B).
Participants were instructed to practise their breathing exercises twice a day for around 25 minutes over a period of 30 weeks (self-reported median time spent actually practising the exercises was 12 mins in Group A and 16 mins in Group B). The participants were also encouraged to use a shorter version of their exercises in place of reliever medication, and to use their inhalers if the exercises did not work after three to five minutes.
Use of reliever medication fell by 86% in both groups, a process which began within weeks of starting the exercises, and was maintained over eight months.
At the start of the study, participants used around three puffs of reliever each day, which fell to approximately one puff every third day by the close of the study. Preventer medication dose halved among the participants.
Quality of life scores remained unchanged in both groups, but good asthma control was maintained even though inhaler use was reduced. There were no changes in lung function or airway responsiveness in either group.
As both groups came to depend less on medication by the end of the study, despite the differences in the techniques used, the authors suggest 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.
Comments and discussion
Although a table summarises the interventions, it would be helpful if the researchers were to make the videos generally available for scrutiny. As described, the exercises may have otherwise engaged some of the accessory muscles for respiration, or given greater freedom of movement to the diaphragm, encouraging abdominal rather than thoracic breathing. The authors write that
[d]evising a credible control for complementary medicine interventions has been acknowledged as a difficult task[.]
However, in the absence of a fuller description of the exercises and how they were implemented by Group B participants, it is not clear that the researchers have achieved an adequately controlled breathing technique to act as a control in this trial. The "non-specific upper-body manoeuvres" may have unintentionally promoted abdominal breathing (not a variable that is assessed in this study). The "control of breathing" exercises are not specified beyond "good posture and relaxation" (both of which may give greater freedom of movement to the diaphragm). And we learn that the route of breathing was not specified with "both mouth and nasal breathing demonstrated".
I would have liked to read a post-study follow-up with the Group B participants to establish what they understood by "control of breathing": e.g., for some people this might have been pursed-lips breathing (although this might not have been demonstrated on the video) or prolonged exhalations and a lower respiratory rate. I would like to know if the participants alternated between mouth and nasal breathing, in conjunction with the video, or if they failed to notice the difference because no attention was drawn to it. Some of these questions might have been answered if the researchers had included an analysis of any participant enquiries or any recurrent issues at the 2 weekly reviews.
Route of breathing and end tidal CO2 measurement
The results are interesting but although the "shallow, nasal breathing with slow exhalations" sounds similar to Buteyko, it is not the Buteyko technique
. For the sake of internal consistency, the videos were standardised in the two conditions. The exercises were taught as something that should be practised twice everyday and used as a rescue remedy at symptom onset.
It is not clear whether Group A were encouraged to breathe in and out through the nose wherever practical
(e.g., as per the Buteyko Method) rather than just during the practice period (it seems as if there was no instruction on this point). However, where route-of-breathing (ROB)information is available, the authors report that 14/14 of Group A used nasal breathing. This report is tempered by the study criteria for ROB. The criteria were that a participant was predominantly nasal breathing if 50% or more of breaths were from the nose and 40% or fewer of the breaths were from the mouth (and vice versa for predominantly mouth ROB): where the proportion of both nasal and mouth were between 40-50%, subjects were classified as having mixed ROB. There are no additional data to determine ROB when breathing in or out.
The novel measurement method makes it difficult to cross-compare these data for ROB and ETCO2 with those of previous studies. The authors describe problems with the fragility of the device used to measure both ROB and ETCO2.
The device consisted of a headset, with a flexible arm holding two probes. The probes were positioned in front of the mouth and the nares respectively, as close as possible without touching the face. A thin, transparent sheet of plastic was positioned between the probes to minimise mixing of airflow.
Although the device was designed to be less obtrusive than commonly-used equipment, without a diagram or photograph, it is not clear that it is. There is no indication of the size of the probes nor how they were adjusted to capture the airstream from different parts of the mouth. Presumably the 2 minute recording of data typically captured the nasal cycle of breathing in through one nostril and out through another (where applicable). It is possible to envisage that insufficient data points were recorded if the nasal cycle switched during the recording period. Although the probes and were "as close as possible" to the mouth and nares there may have been contamination of the samples with room air and this might have affected the measurements. Again, without a diagram, it is not possible to determine the location of the intake port. Data from "incomplete or fragmented breaths" were discarded although respiratory instability is suggested as a distinctive feature of people with disordered breathing linked to, for example, panic disorder
which may be co-morbid with asthma.
The authors report reliability testing of the device for calibration by "five repeated measures of end tidal CO2 on a single subject on the same day", however, I would argue that this is not a valid reliability test as described. If the authors meant 5 consecutive sessions within (say) a 30 minute period then they should state that. Otherwise, there may be diurnal fluctuation in ETCO2 measurements, or a difference in results following consumption of food or a caffeinated drink or a number of other variables that might influence the ETCO2 reading.
On a personal note, I would have found it easier to understand the ETCO2 readings and comments associated with them if the authors had consistently converted the units of measurement between %, mmHg and kPa
rather than leaving it as an exercise for the reader or if they consistently quoted one of them. I would also have liked some discussion about the difference in ETCO2 levels obtained from control subjects and those with asthma in this study and the Osborne study
to which they later refer. In the Osborne study, with a smaller age-range of subjects, the
[e]quivalent values for PETCO2 were 4.89 (0.09) kPa and 5.28 (0.09) kPa, [in the patient and control groups] respectively (mean difference 0.39 kPa (95% CI 0.12 to 0.66), p<0.01).
This Slader trial does not specify an age-range for the "20 normal (non-asthmatic, non-smoking) adults": the authors report that the
median end tidal CO2 value for these subjects was 4.86% (36.9mmHg; 4.92kPa), approximately 1% higher than for our asthmatic subjects.
At the quoted values, the asthmatic subjects in the Osborne study had a similar ETCO2 to the control subjects in this trial: 4.89kPa versus 4.92kPa respectively. Although the Bowler study
has a wider age-range of subjects, the reported mean ETCO2 for the Buteyko Breathing Method and other experimental control groups during the run-in to the trial were similar (BBT, 33 ± 5 mmHg; control, 32 ± 4 mmHg) with similar results after three months (BBT, 35 ± 3 mmHg; control, 33 ± 3 mmHg). In the Bowler study,
the normal subjects had significantly higher mean ET CO2 levels (41 ± 4 mmHg) than both the BBT and the control groups.
The ROB measurements (i.e. nasal versus mouth breathing: data available in the online pdf supplement) were obtained under distraction conditions (filling out questionnaires) that are not neutral, but have previously been reported as linked to increased mental load, breath-holding and an increased ETCO2
. Over the course of the study the ETCO2 measurements dropped in both groups and this might indicate some habituation to the distraction task with possibly less breath-holding and a lesser impact on ETCO2 levels. However, the authors caution that both the ROB and ETCO2
assessments have missing data; further, the participant numbers are small.
The ETCO2 readings are not broken down by sex: there is no information about variations in women who may present ETCO2 fluctuations related to their menstrual cycle.
Participants' implementation of instructions
The authors state that participants were offered face-to-face tuition but there is no report that anyone accepted that offer. A researcher contacted the participants in both groups on a regular basis to check that they were doing their exercises and to answer any questions about technique. However, neither the online supplement nor the paper reports participant enquiries.
Meuret and her colleagues studied psychophysiological responses to breathing instructions
. These findings echo previous work by Meuret which suggested that "[t]echniques taught in [breathing training] must take account of respiration rate and tidal volume in the regulation of blood gases (pCO2)
". They reported that overall:
- an increase in tidal volume (TV) was counterbalanced by a decrease in ventilation rate
- a decrease in TV was counterbalanced by an increase in ventilation rate.
They sum up their findings as follows:
We conclude that in calm people breathing instructions that might be expected to raise pCO2 levels fail to do so. Feedback of end-tidal pCO2 may be a superior way of teaching people not to hyperventilate.
It seems plausible to argue that without appropriate physiological feedback (e.g., ETCO2), the participants would not able to gauge the appropriate implementation of their breathing exercises (particularly in Group A). However, it would not have been practical to include such feedback in the experimental design used by Slader and her colleagues.
Overall, the authors attribute the reductions in medication use more to the process and other factors in the trial than to the breathing techniques. There have been several media reports that have labelled the shallow, nasal breathing method as Buteyko
but the reported elements are not the whole Buteyko Method, nor are these elements of the exercises appropriately applied. I would argue that this trial was not a study of the Buteyko Method but of elements that were not necessarily taught to be used appropriately by the participants nor was there a check for effective implementation. In the absence of feedback during the exercises, it is possible that although Group A were taught a hypoventilation technique, there may have been alveolar hyperventilation (as per Meuret).
Changes in medication use
The authors summarise a Cochrane review of breathing exercises for asthma
that reports a decreased use of short-acting reliever medication but
no consistent evidence of improved disease control such as reduced requirement for anti-inflammatory medication, reduced airway hyperresponsiveness, or improved lung function.
In this study, the authors report an 86% reduction in reliever use and a 50% reduction in the dosage of inhaled corticosteroids. They acknowledge that
these changes were achieved without impacting negatively on underlying disease control, as measured by lung function and airways responsiveness.
They speculate that
while breathing exercises may not confer any particular physiological benefit, the process of using breathing techniques as first line symptoms treatment may allow people to substantially reduce their use of [beta2] agonist. This itself may be beneficial by reducing adrenergic side effects, by reducing response to allergens, or by reducing mast cell tachyphylaxis.
They further speculate that some of the "subjects may have been relatively overtreated with ICS at entry" although they do not discuss how this might have influenced their results.
The authors conclude that
[t]hese improvments 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.
They re-affirm that they believe it is the process rather than the breathing-techniques that is important because it provides "a deferral strategy for [beta2] agonist use". They argue that there is some evidence to support inhaler dependence and overuse by asthmatics.
The significant reduction in medication prompts the speculation that future pharmacological trials should include a behavioural intervention as a comparison for some of their experimental groups. Although the authors of this study made a contribution towards meeting the criteria identified in the Cochrane Review
, they have not given sufficient detail to qualify as "full descriptions of treatment methods" as called for by the Cochrane reviewers. There is insufficient evidence to know whether or not the instruction or implementation is similar to what might have been achieved with the face-to-face guidance of a Buteyko practitioner, although, surprisingly, the reductions in medication use are in line with those reported in studies that have assessed the Buteyko technique.
This study examined elements such as nasal breathing without explaining the theoretical underpinning as to why it is thought to be effective or valuable: similarly for the outcome measurement of ETCO2. There is no discussion of alveolar or systemic hypocapnea and why this might contribute to the symptoms of asthma: there is no discussion as to whether the hypoventilatory exercises were intended to promote eucapnea in the Group A participants.
Although this is an interesting paper and has excited some interest in various media, this trial is not an assessment of the Buteyko Method. The researchers do not claim to have examined the Buteyko Method in this trial but they do introduce various elements that are popularly associated with the Buteyko technique.