Clinical Significance of Cough Peak Flow and Its Non-Contact Measurement via Cough Sounds: A Narrative Review

Coughing is the primary defence mechanism against foreign bodies in the central airways and can quantitatively be assessed by cough peak flow (CPF). We conducted a narrative review of the literature on CPF, which is most commonly used for evaluating cough strength. This review regards the method for measurement of CPF, the cough-related factors influencing CPF, the clinical significance of CPF evaluation, and a novel cough strength prediction method using cough sounds. Furthermore, this review presents various cutoff thresholds that predict extubation failure in patients on mechanical ventilation, acute respiratory failure, and aspiration risk. The published clinical evidence of CPF demonstrates reasonable diagnostic accuracy, predictive power, and validity, although additional studies on the non-contact measurement of CPF via cough sounds with better-quality methodologies are required.