Dysfunctional breathing or breathing pattern disorder: New perspectives on a common but clandestine cause of breathlessness

Dysfunctional breathing (DB) denotes breathing pattern disorders that result in breathlessness. Other non-respiratory symptoms may be present and co-existent organic respiratory disease may be present. Hyperventilation (HV) is the most widely recognized type of DB but other formats include periodic sighing, upper thoracic breathing pattern, mouth breathing and breathing asynchrony.1, 2 Different types of DB often co-exist in a single person. There is now considerable evidence that DB is common and may contribute to breathlessness, particularly in asthma that is unresponsive to optimized conventional treatments.3 However, the diagnosis is frequently overlooked, and DB remains poorly understood and researched. To date there is no consensus definition of DB and no 'gold standard' has been established for diagnosis. Consequently, estimates of DB prevalence in general populations and diseases such as asthma and COPD are highly variable. Studies often utilize the Nijmegen questionnaire as a diagnostic tool which was not its intended purpose. Thomas and co-workers found DB in 6%–10% of a general population but as high as 30% in people with asthma.4, 5 More recently studies from Denmark6 and Australia3 reported prevalences of 30% and 47%, respectively in severe asthma. In these reports, patients with DB tended to have poor asthma control, lower quality of life and associated comorbid conditions such as anxiety, depression and vocal cord dysfunction/inducible laryngeal obstruction (VCD/ILO). In patients studied at a hospital respiratory clinic we have reported prevalence of 27% and 47% in asthma and COPD respectively.7 Despite methodological reservations, these studies indicate that DB is a common finding that may be a 'treatable trait'—a potentially modifiable factor that should be considered in people with unexplained breathlessness or breathlessness that is out of keeping with the degree of organic disease. The association between DB and VCD/ILO (another hidden cause of dyspnoea) is particularly complex—and important (see Figure 1). We have previous postulated that DB may lead to laryngeal activation with resultant inspiratory closure provoking a sensation of dyspnoea in people with VCD|ILO.8 Recent studies have supported this putative link. Lee and co-workers studied people with severe asthma who had verified VCD/ILO and found that DB was the strongest predictor (OR = 4.9) of a diagnosis of VCD/ILO.9 Whether DB can induce VCD/ILO in healthy people and perhaps more readily in people with asthma is a key question but surprisingly no studies have been reported. Limited studies in the 1990's had used laryngoscopy with HV and found that it can induce paradoxical and other vocal cord behaviours10, 11 but whether diagnostic criteria for a diagnosis of VCD/ILO were achieved was not reported. Links between DB and other disorders are poorly researched. There has been reports that COVID-19 can induce VCD/ILO12 and it is feasible that DB and/or VCD/ILO can contribute to breathlessness in long COVID. This possibility remains to be investigated. Identification of DB has usually employed the Nijmegen questionnaire.13 However, the questionnaire was validated initially only in exercise-induced HV but it has been extrapolated to other settings. A small validation study in asthma has been reported14 and scores >23 are considered positive. Other diagnostic instruments include the Self-Evaluation of Breathing Questionnaire (SEBQ),15 Breathing Pattern Assessment Tool (BPAT)16 and specialized physiotherapist assessment.9 Recently a simplified breathing pattern assessment scoring tool was proposed in athletes17 and sophisticated optoelectronic monitoring has been reported in athletes.18 These methods all have inherent strengths and weaknesses, and the current research trend is to use a combination of diagnostic modalities.3, 6, 9 As noted, since no gold standard exists beyond expert assessment, validation of various diagnostic approaches poses challenges increased by the heterogeneity of types of DB. Current treatments are not based on a strong evidence base. Two breathing retraining strategies are usually employed, with considerable variation. In the Papworth method patients are taught slow nasal breathing with a strong emphasis on diaphragmatic movement. Short-term studies have shown benefit3, 19, 20 but long-term studies are lacking. The Buteyko technique provides patients with training in controlled hypoventilation and may have benefit in asthma despite absence of improvements in lung function.21 Some treatments for VCD/ILO employ breathing techniques that might also address DB.22 A digital self-guided breathing retraining intervention has shown some benefit on quality of life but had no impact on lung function and inflammatory parameters.19 Finally, pulmonary rehabilitation has shown convincing benefit in COPD23 and other lung disorders24 but there have been no studies reported in DB. The strategy has been proposed for adaptation outside COPD and merits further research in DB.25 At present DB finds itself in limbo. The absence of gold standard diagnostic criteria means that making a definitive diagnosis of DB, and implementing evidence-based management is a vexing and amorphous goal. There appears to be little prospect that this will change. A fundamental step is to agree on a gold standard definition of DB. This could proceed along the lines of work that has been done to establish global consensus on VCD/ILO diagnosis,26 and this step would allow for the generation of a unified evidence base from which diagnostic and treatment studies could arise. New approaches are required to heighten awareness of DB. Similar to structured assessment approaches in airways disease, DB should be considered as part of the complex breathlessness workup. Clinically, given the close relationship between VCD/ILO and DB, it may be optimal to co-assess rather than consider in isolation. Put another way, if thinking of one, think of the other.27 How could co-investigation be implemented? Research study designs that investigate the disorders jointly should be prioritized. Modern laryngoscopy leveraging high fidelity iPhone recording and ultrathin endoscopes that improve patient comfort can be utilized with simultaneous assessment of the larynx, and DB.26 Dynamic CT can swiftly establish a diagnosis of VCD/ILO, and perhaps CT based case-finding for VCD/ILO could also raise the profile of DB via structured reporting processes or future work evaluating markers of breathing patterns on CT.28 Importantly, prospective studies of DB and VCD/ILO could elucidate the complex bidirectional relationship between DB and VCD/ILO and enhance detection and management. In summary, the conundrums surrounding DB pose considerable challenges. Further research should be prioritized in healthy people and in diseases such as asthma and COPD and should aim to clarify 'normal breathing' as well as relationships of DB with abnormal laryngeal function, particularly VCD/ILO. As in VCD/ILO,26, 29 we need new initiatives to help to increase consumer and physician awareness, improve understanding of DB and to propel new research, particularly focusing on standardizing and validating a diagnostic and therapeutic approach suitable for widespread uptake for this important and common condition. Open access publishing facilitated by Monash University, as part of the Wiley - Monash University agreement via the Council of Australian University Librarians. Philip Bardin is Editor-in-Chief of the journal and co-author of this article. He was excluded from the peer-review process and all editorial decisions related to the acceptance and publication of this article.