Cough effectiveness during airway invasion in adults with oropharyngeal dysphagia: A systematic review of literature

BACKGROUND: Cough and swallowing share common neuroanatomic pathways, leading to an overlap between their mechanisms. Despite the widely recognised role of cough as an airway defence mechanism, empirical evidence supporting its effectiveness for airway clearance is lacking. OBJECTIVE: This review summarises and appraises available evidence regarding the effectiveness of cough in response to airway penetration and/or aspiration during videofluoroscopic swallow study (VFSS) or flexible endoscopic evaluation of swallowing (FEES) in adults with oropharyngeal dysphagia (OD) of any aetiology. METHODS: The Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines were followed. Literature search was conducted in March 2023 and updated in March 2024 across six databases without publication status, language, or date restrictions. Two independent reviewers performed screening, with disagreements resolved through consensus and majority vote. The principal investigator conducted data extraction and quality appraisal using the Downs and Black checklist. RESULTS: Of 6,049 studies retrieved, 25 met the eligibility criteria. Due to heterogeneous reporting, a summary of participant demographics could not be compiled. Absence of a standardised method for measuring cough effectiveness meant meta-analysis was impossible. Nonetheless, an effective cough response to penetration/aspiration was noted for some participants within 17 studies, ineffective cough responses for some within 17 studies, while one study reported a partially effective cough response for participants. CONCLUSIONS: Robust evidence on cough effectiveness is lacking due to study heterogeneity and inconsistent reporting. Developing a standardised tool to assess cough effectiveness would ensure consistency and comparability across studies, improving clinical reporting of VFSS and FEES outcomes.