Breathing retraining to improve dyspnoea and walking distance in patients with interstitial lung diseases: A randomised controlled trial

Introduction

Interstitial lung disease (ILD) is a term used for a group of conditions in which changes to the interstitium, due to a combination of inflammation and fibrosis, are observed (Swigris et al. 2008). Dyspnoea is the hallmark progressive symptom in this group of conditions, which may be severe and disabling leading to severe physical impairment, exercise limitations and poor quality of life (Swigris et al. 2005; Kondoh et al. 2005; Martinez et al. 2005; Swigris et al. 2008) with accompanying aerobic and skeletal muscle deconditioning, leading to social isolation and impaired emotional well-being (Swigris et al. 2008).

The importance of including pulmonary rehabilitation (PR) as part of the symptom management for patients with ILD is being given more importance, especially when noting the marked improvements in dyspnoea and exercise tolerance in patients with chronic obstructive pulmonary disease (COPD) (Sciriha et al. 2005; Walter et al. 2006). Such an intervention is now recommended as part of the management of ILD (Raghu et al. 2011; Raghu et al. 2015; Sciriha et al. 2019).

Recently, breathing retraining as part of the management of COPD has been investigated, with research reporting marked improvements in dyspnoea (Garrod et al. 2005; Spahija et al. 2005; Bianchi et al. 2007; Nield et al. 2007). The reasons for such improvements relate to the reduction of dynamic airway compression and air trapping which is brought about with prolonged expiration (O’Donnell et al. 1987). In addition, it is apparent that breathing retraining using pursed lip breathing is also effective in improving walking distances in people with COPD (Garrod et al. 2005).

Despite just a few studies recommending breathing retraining in COPD patients (Garrod et al. 2005; Spahija et al. 2005; Bianchi et al. 2007; Nield et al. 2007), other studies including one by Vitacca et al. (1998) questioned the validity of this technique, stating that breathing retraining using deep diaphragmatic breathing is not recommended for persons with COPD, as it worsens dyspnoea. This conclusion was based on the reduction of the efficiency of the diaphragm caused by its asynchronous and paradoxical breathing movements. These inconsistencies have led to debates about the importance of including such techniques in the management of dyspnoea in COPD. Since the findings are inconclusive (Vitacca et al. 1998; Garrod et al. 2005; Spahija et al. 2005; Bianchi et al. 2007; Nield et al. 2007; Bhatt et al. 2012), and noting the impact that dyspnoea has on the physical status and health related quality of life in patients with a diagnosis of ILD, the need to explore the benefits of this technique in patients with ILD is warranted (Raghu et al. 2011). Findings may lead to better management of dyspnoea as one of the main patient-reported symptoms in ILD.

Method

This paper reports a randomised controlled trial. Data obtained for both the experimental and control groups were recorded at the start of week 0 (baseline) and the end of week 12, during which PR sessions were held twice weekly.

Participants

68 subjects with a confirmed diagnosis of ILD, were referred to the PR service by respiratory consultants from the medical outpatients of a local hospital serving the population needs of a small independent jurisdiction of approximately 500,000 persons, with the prevalence of patients with ILD estimated to be at 24.9 per 100,000 population. These subjects were all found to be medically stable by the respiratory physicians and had been free from exacerbations for the 3 months prior to their recruitment. Pharmacological treatment was assured to be optimal by the medical doctors. Each participant was provided with written information about the programme and were invited to participate in this study.

Following an assessment by both a medical practitioner and a physiotherapist, 27 subjects accepted to participate in this study (Figure 1).

Figure 1: Consort flow diagram.

The inclusion criteria included age (18 years and over), oxygen saturation (>92% at rest with or without the use of supplementary oxygen), a willingness to participate in the rehabilitation classes, a stable cardiovascular system and the absence of neurological or orthopaedic problems which could interfere with rehabilitation and did not have other lung pathologies including COPD or bronchiectasis. Those subjects who required modifications to their drug therapy due to exacerbations during the trial were excluded from the study. Participants were then randomly allocated by a 3rd person – in doing so blinding the selection to the researcher. 15 participants were allocated to the control group that followed a 12-week PR programme and 12 participants were allocated to the experimental group that followed the same 12-week PR programme with the addition of breathing retraining.

Measurements

All the subjects were assessed before being enrolled and then on completion of the PR programme. The following outcomes were measured: lung function tests, 6-minute walk test (6MWT) and dyspnoea scores before and exactly following the 6MWT.

The 6-minute walk test (6MWT)

The 6MWT was performed indoors, in accordance with the guidelines of the American Thoracic Society (ATS 2002). Each participant was instructed to walk at their perceived maximum intensity along a pre measured, 30-metre corridor, consisting of a flat hard surface, marked clearly by two cones at either end, for 6 minutes. The total distance walked was measured.

The dyspnoea Borg scale

The Borg scale is a valid and reliable scale that was used to assess dyspnoea scores at rest and on exertion (Nishiyama et al. 2010). Before and after the 6MWT, each participant was asked to rate their perceived levels of breathlessness. Participants were familiarised with the scale before the start with explanations provided as to the different scoring levels so each participant could each rate their own perceived level of breathlessness and in order to ensure that each had the same explanation of how to rate their breathlessness.

Intervention

All 27 subjects followed a multidisciplinary-led PR programme which was delivered twice weekly for 12 weeks at an outpatient department in a local general hospital. Each session lasted 2 hours, with the 1st hour consisting of exercises made up of 5 minutes warm-up, walking on a treadmill, (the speed of which was devised from the 6-minute walking test and the time gradually increased throughout the weeks); step-climbing, arm ergometry, cycling using a stationary bike and also strength training for the upper and lower limbs using free weights. The intensity of the exercise programme was one set at 70% of their maximum heart rate measured using a pulse oximetre. Inspiratory muscle training, a routine procedure to this PR programme, was also carried out using the Respironics IMT Threshold Trainer® for 15 minutes at the end of this 1-hour session. All participants were then instructed to complete IMT at home for 30 minutes, 5 days per week, with adherence assessed through a diary system. In addition to this, the experimental group was given an exercise programme of breathing retraining consisting of pursed-lip breathing, breathing control and diaphragmatic breathing exercises as described below.

Breathing control (BC)

Involved encouraging each patient to use his/her lower chest to breathe whilst relaxing the upper chest, head, neck and shoulders.

Pursed-lip breathing (PLB)

Involved the patient having to inhale through the nose then exhale slowly and evenly through the mouth against a resistance created by pursing the lips with an aim of controlling the respiratory rate and decreasing the levels of breathlessness.

Diaphragmatic breathing (DB)

Involved encouraging each patient to inhale slowly and deeply through the nose for a count of 2 and exhale slowly through pursed lips for a count of 4. During this breathing exercise the participant was encouraged to move out the abdominal wall with reduction of upper rib cage movement during inspiration, to keep neck muscles relaxed and to place their hands on their abdomen if one was performing an exercise which did not require the use of the hands.

Participants in this group, whilst undergoing the exercise component of PR, were constantly instructed, advised and monitored throughout the intervention to ensure that such exercises were integrated in the regime, with the breathing control and pursed lip breathing carried out during the PR programme.

Included in the PR programme, both the control and the experimental groups received educational sessions discussing several topics including aspects about their condition, pharmacological measures, coping with a chronic condition, dietary aspects and chest clearance. The experimental group received 2 additional, educational sessions on breathing retraining delivered by the physiotherapist running the PR programme. All participants were then given a home exercise programme consisting of exercises similar to those that were carried out during the session. The home exercises were monitored by means of a home diary system provided to each participant at the start of the programme.

Ethical considerations

Signed informed consent was requested from all the participants with the possibility to withdraw from the programme at any time without prejudice. Data collected was coded to ensure patient anonymity and the information collected was used only for the study purposes. No inducement was offered. Ethical approval was sought and obtained from the University of Malta Research and Ethics Committee (067/2017) and Clinical Registration (NCT03729583).

Statistical analysis

Statistical analysis was carried out using Statistical Package for Social Science (SPSS) software version 25. Baseline characteristics and exercise data are presented as median and interquartile range (IQR). After having tested for normality using the Shapiro-Wilk test, the Wilcoxon signed rank test was used to compare changes in dyspnoea scores before and after the 6MWT, and the walking distance, at baseline and on completion of the PR programme, for both the experimental and control groups. The Mann-Whitney U test was then used to compare the differences between the experimental and control groups by demographic variables (for example, age, height, weight) and functional variables (for example, 6MWT and Borg scales).

Results

The baseline characteristics of all the participants are presented in Table 1.

Table 1: Demographic characteristics at baseline.

6MWT: 6-minute walk test; IQR: interquartile range.

No significant differences were identified in height (p = 0.85), weight (p = 0.58), 6MWD (p = 0.064), Borg scale at rest and the Borg scale on exertion (p = 0.70; p = 0.30 respectively) between the participants of the experimental and control groups. Although there was a significant difference (p = 0.015) identified in age with the experimental group consisting of older participants than the control group, the age of the participants was not found to correlate with outcome measures in this study using the spearman correlation test. Experimental group: correlations between age and 6MWD = r = 0.69, p = 0.832; Borg scale at rest r = -0.093, p = 0.775; Borg scale on exertion r = -0.282, p = 0.374. Control group: correlations between age and 6MWD = r = -0.065, p = 0.817, Borg scale at rest r = 0.208, p = 0.458, Borg scale on exertion r = -0.447, p = 0.095.

Comparisons were made within the experimental and control group respectively to examine whether there were any significant changes in dyspnoea scores measured before and after the 6MWD at between baseline and at the 12-week time point. Breathing retraining with PR resulted in statistically significant improvements in dyspnoea scores for the experimental group post exertion Figure 2, as measured using the Borg scale over the 12-week PR intervention (median 3.0 (IQR 1–5) at week 0 to 2.5 (IQR 0.2–3.75), p = 0.033), but not for dyspnoea measures pre-exertion (0 (IQR 0–2) and at week 12 (0 (IQR 0–0) p = 1.000).

Figure 2: Figure showing changes in the dyspnoea Borg scale on exertion in the experimental and control group.

No significant differences in dyspnoea scores were found in the control group which did not obtain any statistically significant changes in dyspnoea scores both at rest (week 0: 0 (IQR 0–0), week 12: 0 (IQR 0–2) p = 0.139) and post exertion (week 0: 3 (IQR 0–4), week 12: 2 (IQR 1–4) p = 0.608).

When comparing both groups at the 12th week, statistically significant improvements were noted for the experimental group in dyspnoea scores at rest (U = 28.000; p = 0.029). On the other hand, when comparing the dyspnoea scores following exertion, the difference in improvement was not statistically significant (U = 51.500; p = 0.971) as presented in Figure 2.

6MWT measure

Both the experimental (p = 0.017) and control group (p = 0.003) reported statistically significant improvements in the 6MWT between baseline and following the 12-week PR programme. The experimental group covered a median total walking distance of 475m (IQR 437–521) and the control group, a median value of 413m (IQR 394–450) (Figure 3). However, when analysing the 6MWT scores at the 12th week between the experimental and control groups, a statistically significant difference was identified (U = 18.500; p = 0.015).

Figure 3: Figure showing changes in the 6-minute walk test in the experimental and control group.

Discussion

The addition of breathing retraining to a regular 12-week PR programme have been shown to add improvements in dyspnoea scores and also in the 6MWD in a group of patients with a diagnosis of ILD. Although not all gains reached statistical significance, this study will serve for further studies in this field searching for better outcomes in the management of symptoms in ILD patients.

There is little research on the effects of breathing retraining on dyspnoea scores and walking distance in patients with interstitial lung disease; results which would have important clinical implications in the management on SOB (shortness of breath). The identification of better outcomes through additional interventions such as breathing retraining, will allow health care providers to offer support to these patients to better patient management. This is regarded as a significant step in the right direction since patients who are symptomatic will eventually develop other co-morbidities such as depression, which in turn results in a decline in health status (Swigris et al. 2008). Therefore, such interventions may have a greater positive impact on the health status associated with this condition, and would also merit further investigation.

Evidence shows that breathing retraining is beneficial in COPD patients as it improves the 6MWT (O’Donnell et al. 1987; Steier et al. 2008; Holland et al. 2010; Bhatt et al. 2012) and a reduction of dyspnoea levels (Spahija et al. 2005; Garrod et al. 2005; Bianchi et al. 2007; Nield et al. 2007). In this study, in which breathing retraining was included to the normal PR programme, at the 12th week comparisons between the groups found statistically significant differences in the pre-exertion dyspnoea scores (U = 28.000; p = 0.029), and in the 6MWD (U = 18.500; p = 0.015) for the experimental group.

The reasons for these better outcomes in dyspnoea scores at rest and following the 6MWT for the experimental group may be explained. Having incorporated breathing control in with a high intensity PR programme, might have enabled the patients to be in a better position to meet with the demands of the programme whilst learning to control their breathing pattern, something which was not applicable for the control group. In light of this, the participants in the experimental group might have focused on pacing the exercise task requested, learning to control their breathing pattern, therefore controlling the respiratory rate and in turn preventing hyperventilation. As a result, it may be hypothesised that the respiratory muscles are able to deal with the increased demand causing less lactic acid production as the programme progressed. It is known that lactic acidosis induced by exercise increases the stress on the ventilatory system due to a buildup of carbon dioxide, a finding which has been reported to occur in patients suffering from COPD (Souza et al. 2010) and would merit investigation in ILD patients, something which to the knowledge of the authors has not been look into. Dyspnoea scores at rest improved throughout the programme and this may be attributed to the slower and deeper breathing associated with breathing retraining using pursed lip breathing. This is known to prolong expiratory time which in turn, might have mediated a reduction in the resting respiratory rate (Bianchi et al. 2007), possibly resulting in a reduction of minute ventilation and ventilatory work as tidal volume remained unchanged. This in theory, would allow more time for ventilation/perfusion matching (Muller et al. 1970; Hsia et al. 1999) resulting in the reduction of dyspnoea at rest in the experimental group subjects.

Even though not all the evidence points towards the efficacy of breathing retraining in improving dyspnoea scores in all patients with a diagnosis of COPD (Vitacca et al. 1998; Fernandes et al. 2011; Bhatt et al. 2012) the findings from this study show that breathing retraining might benefit patients with a diagnosis of ILD. The difference in lung pathology between ILD and COPD may account for this difference. COPD is an obstructive condition unlike ILD which is a restrictive condition, making those who have COPD more disposed to dynamic hyperinflation. Dynamic hyperinflation increases the mechanical load on inspiratory musculature and also reduces their mechanical advantage resulting in the greater severity of dyspnoea and distortion in chest wall movement (Gibson 1996). In view of such mechanical changes, as Bianchi et al. (2012) concluded, breathing retraining using PLB is useful in patients who manage to deflate their chest wall but not in those that hyperinflate during PLB. With such a difference in the lung pathology, breathing retraining may be regarded as favourable for ILD patients as it allows for better gaseous exchange and less workload on the inspiratory muscles (Wilkens et al. 2010).

When comparing dyspnoea scores for both groups on exertion, the difference in improvement found for the experimental group (p = 0.897) after 12 weeks was statistically insignificant. Despite this, the median score on the Borg scale post exertion (median value of 2.50 (IQR 0.3–3.8)) was better than that of the control group (median value 2, (IQR 0.5–4)) after 12 weeks. These findings confirm that breathing retraining does lower dyspnoea scores as reported by Nield et al. (2007) and Bhatt et al. (2012) in patients with COPD possibly due to the prolonged expiration. A sustained increase in the strength of the inspiratory musculature as a result of the addition of breathing retraining, might have resulted in less force being generated with each breath, that in turn may have led to less motor output of the muscles of respiration and to a reduction in the work of breathing (Nield et al. 2007). Overall, breathing retraining did show added benefits to the already documented benefits of PR in improving exertional dyspnoea in ILD patients. These added benefits may help these patients to perform other activities with less shortness of breath and in doing so enhance their quality of life (Swigris et al. 2005).

Statistically significant improvements in the 6MWT were also noted following the 12-week PR programme in both groups, with changes in distance being more significant in the experimental group (U = 18.500; p = 0.015). Hence breathing retraining has a role in improving functional exercise capacity in ILD patients by improving the walking distance. The reason for this may lie in the understanding that the experimental group developed a lower work rate for breathing on exertion. In doing so, a decrease in the metabolic energy requirements of respiratory muscles might have allowed the locomotory muscles to maximise their performance (Hsia 1999; Aliverti et al. 2008). This would help also in decreasing the levels of anxiety associated with SOB and hence account for the decrease in dyspnoea scores at rest in this group (Tselebis et al. 2016).

Breathing retraining performed by patients with COPD improved the 6MWT (Steier et al. 2008), mediated by an increased diaphragmatic excursion and a reduced respiratory rate resulting in decreased dyspnoea. Despite this, consideration must be taken when comparing the results to the current study involving ILD patients. The primary limitations to exercise in COPD patients may be ventilatory limitation and skeletal muscle dysfunction (Pepin et al. 2007) whilst in ILD patients this may be circulatory factors and impaired pulmonary gas exchange (Agusti et al. 1991) characterised by exercise induced hypoxaemia.

Conclusion

In conclusion, whilst noting that the sample size of this current study was small and that there were trends of improvement, that would be best repeated using larger cohorts of patients, it found that the addition of breathing retraining to a 12-week PR programme resulted in better dyspnoea scores and greater exercise tolerance in patients with ILD. These findings signpost that breathing retraining should be considered into the management of dyspnoea in those persons who have from ILD.

Key points

• The addition of breathing retraining to a PR programme led to additional improvements in dyspnoea scores and also functional capacity as assessed using the 6MWT in a group of patients with a diagnosis of ILD compared to the control group who only received PR.

• This study will serve as a pilot study and as a call for further research to explore further means on how to assist in the management of dyspnoea in patients with ILD.

• With guidelines for the management of ILD recommending the importance of PR together with the pharmacological management, this study continues to add on the importance of this intervention for these patients with breathing retraining being one of the possible areas to have incorporated in PR as a possible and effective strategy to help improve shortness of breath (SOB).

Acknowledgements

The authors wish to thank all the participants who made this study possible.

Author disclosures

All the above mentioned authors report that this study was self-funded and having no competing interests, financial benefits or conflicts of interest. Preliminary results of this research study were presented in the Malta Medical School Conference held between the 28th and 1st December 2018.

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