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

Abstract

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