Breathing–swallow dysfunction in COPD: How silent aspiration may be contributing to exacerbations

In health, coordination of breathing with swallow is critical to ensure effective ingestion of nutrients and to avert aspiration. In disease conditions such as chronic obstructive pulmonary disease (COPD), safe swallow is of particular importance as aspiration has been linked to serious adverse respiratory outcomes. There is now considerable evidence of breathing–swallow dysfunction leading to aspiration with increased rates of acute exacerbations of COPD (AECOPD) in a substantial subgroup of patients with COPD. These findings warrant reflection and merit careful consideration by clinicians involved in the care of this patient group. The potential risk of AECOPD caused by prandial aspiration has received scant attention. A recent large prospective study has established that patients with verified aspiration, detected during stable disease, have increased propensity to develop AECOPD. The study employed two methods of ingestion (self-paced and fast-paced cup drinking) using a 100-ml volume of ultra-thin liquid and videofluoroscopy in 151 patients with verified and stable COPD of all severities. Findings indicated that severe AECOPD episodes were more frequent over a 12-month period if aspiration was detected (50% vs. no aspiration 18%; OR = 4.5; p = 0.001). Severe AECOPD was also more common in patients with silent aspiration (in whom cough was entirely absent during the event) and patients with aspiration experienced a shorter time to a first AECOPD event (Figure 1). No factors predictive of aspiration and AECOPD could be identified in multivariate analyses and notably there were no links with COPD severity, lung hyperinflation, BMI, baseline oral health risk measurements, baseline presence of dysphonia, comorbidities, long-term oral corticosteroids, sedatives, Eating Assessment Tool-10 and Airway Questionnaire 20. Aspiration as a causative factor in AECOPD episodes thus appears to be life-threatening in a subgroup of patients and should be considered as an important modifiable factor to be taken into consideration for inclusion in future exacerbation risk prediction models. A key question is whether the way patients with COPD swallow is altered leading to aspiration and worsening of preexisting disease. Drinking at a faster rate can be challenging in COPD and may require respiratory–swallow reconfiguration to ensure airway protection. This possibility was also examined, and the investigators detected a longer total swallow duration, longer time per swallow and lower swallow frequency in patients with aspiration. This was noted during both self-paced and fast-paced drinking. It is uncertain if this swallow pattern is the cause or effect of aspiration; however, it is likely related to physiological or compensatory modification induced by breathing–swallow dysfunction. Surprisingly, there was no difference in aspiration comparing self-paced and fastpaced drinking suggesting that patients may respond (perhaps not deliberately) to aspiration by adjusting swallow behaviour. These findings provide conditional support for aspiration risk minimization strategies such as pausing between swallows or use of single sips over consecutive swallows. These strategies could improve integration of breathing with swallow efficiency, minimize interruption to laryngeal closure and expiratory phase of swallows, whilst enabling opportunity for secondary swallows to clear any post-swallow residue. What approaches are needed to identify and mitigate aspiration risk, particularly in COPD? A high index of suspicion is warranted in patients with this common condition, especially in people with frequent episodes of AECOPD. Accurate diagnosis of aspiration is essential and the importance of using methodologies that aid detection of aspiration, particularly silent and episodic aspiration events, cannot be overstated. Creative use of modern informative and diagnostically accurate radiographic or endoscopic instrumentation is vital and recent observations support the advantages of a diagnostic process employing sequential, ultra-thin, liquid drinking to detect impaired airway protection and aspiration. Repetition of swallowing tasks and testing on more than one occasion can provide enhanced ability for the clinician to detect aspiration and to estimate ongoing risk. Patients with COPD tend to be older and use of standardized questionnaires and other instruments to detect and measure frailty and sarcopenia is essential to quantify related comorbidities. Finally, quantitative combined measurements of swallow and respiratory activity, particularly during and following repeated swallowing, may provide additional information and inform management. Important questions remain. Repeated episodes of aspiration may have serious consequences, but it is not clear if interventions need to be implemented in selected patients such as people with low AECOPD rates, those with frailty and those in whom other pertinent comorbidities are present. Alternatively, adopting a ‘wait-and-see’ approach can be considered to determine clinical significance of breathing–swallow dysfunction over time and the need for intervention based on an individual’s evolving health and COPD profile. Current evidence supporting therapeutic intervention specific to the COPD population is limited and requires confirmation. Received: 28 July 2021 Accepted: 14 September 2021