Concordant Validity of a Digital Peak Cough Flow Meter to Assess Voluntary Cough Strength in Individuals with ALS

Peak cough flow represents an important metric directly related to the physiologic ability of an individual to defend the airway or expel tracheal aspirate. Given the high prevalence of dysphagia and dystussia in individuals with amyotrophic lateral sclerosis (ALS) and recent findings that the expiratory phase of voluntary cough is significantly impaired in ALS individuals, we aimed to determine the reproducibility of an affordable, portable peak cough flow (PCF) meter for the assessment of cough production in individuals with ALS. 109 individuals with ALS completed voluntary cough testing using both the research cough spirometry equipment and a digital peak cough flow meter. Maximum peak expiratory cough flow rates were obtained from each device. Analyses included paired t test, Pearson's correlation, and Lin's concordance correlation to determine the degree of agreement and reproducibility between cough measurement devices (alpha = 0.05). Mean differences between peak cough flow test values (L/min) across instruments were not statistically significant (mean difference =  - 2.93; 95% CI - 18.67, 12.82; p = 0.713). PCF values obtained from the digital peak cough flow meter and the research cough spirometry equipment were strongly associated (r = 0.826, p < 0.000) and demonstrated a high level of agreement and reproducibility (ρ_c = 0.824, 95% CI 0.754, 0.876). These data validate the use of an inexpensive and portable digital peak cough flow device to index peak cough flow strength in individuals with ALS. This assessment could easily be incorporated into a multidisciplinary ALS clinical setting to index the physiologic ability of an individual to protect the airway.