Determining Peak Cough Flow Cutoff Values to Predict Aspiration Pneumonia Among Patients With Dysphagia Using the Citric Acid Reflexive Cough Test

Objective: To investigate the clinical usefulness of the peak cough flow generated during the citric acid reflexive cough test (0.28 mol/L) by determining the appropriate cutoff values that could accurately predict aspiration pneumonia within the first 6 months after onset. Design: Retrospective analysis of a prospectively maintained database. Setting: University-affiliated hospital. Participants: Patients (N=163) with first-ever diagnosed dysphagia attributable to cerebrovascular disease, who had undergone the citric acid reflexive cough test on the same day they underwent the instrumental assessment of swallowing, such as videofluoroscopy or the functional endoscopic swallowing test. Interventions: Not applicable. Main Outcome Measures: Peak cough flow (L/min) from the citric acid reflexive cough test. Results: A final 163 patients had full medical records with 6-month follow-up. Receiver operating curve analysis showed that peak cough flow cutoff values set at 59 L/min were significantly associated with aspiration pneumonia (area under the curve [AUC] 95% confidence interval =0.88 [0.83-0.93]). This cutoff value significantly (P<.001) predicted the risk of aspiration pneumonia with an odds ratio of 21.56 (9.62-48.28). A multivariate regression logistic regression analysis model including initial dysphagia severity, low body mass index, and decreased level of cognition showed that inclusion of the peak cough flow from the citric acid reflexive cough test significantly improved the predictive model of aspiration pneumonia within the first 6 months after onset (AUC=0.91 vs 0.79). Conclusions: Those with reflexive cough strength less than 59 L/min may be at high risk of respiratory infections within the first 6 months after dysphagia onset. Objective measurement of reflexive cough strength may help to predict those at risk of aspiration pneumonia.