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Predictors of Ineffective Cough during a Chest Infection in Patients with Stable Amyotrophic Lateral Sclerosis

¹ Respiratory Care Unit and ² Department of Respiratory Medicine, Hospital Clínico Universitario, Universitat de Valencia, Valencia, Spain

Correspondence and requests for reprints should be addressed to Emilio Servera, M.D., Respiratory Medicine Department, Hospital Clínico Universitario, Avda. Blasco Ibáñez 17, E46010 Valencia, Spain. E-mail: emilio.servera{at}uv.es

Rationale: In patients with neuromuscular diseases, a chest infection is associated with a reduction in respiratory muscle function that may result in decreased cough effectiveness.

Objectives: To determine if a clinical or functional parameter in patients with amyotrophic lateral sclerosis (ALS) in a stable condition could predict spontaneous cough ineffectiveness during a respiratory tract infection.

Methods: Forty consecutive patients with ALS referred to our Respiratory Care Unit were studied during a one-year follow-up.

Measurements and Main Results: FEV₁, FVC, FEV₁/FVC, peak cough flow (PCF), peak velocity time (PVT), maximum inspiratory and expiratory pressures, and bulbar dysfunction evaluation using the Norris scale bulbar subscore (NBS). A total of 26 patients (65%) had spontaneous cough ineffectiveness during a respiratory tract infection. The best variables to predict nonassisted cough during a respiratory tract infection were NBS (p < 0.01) with a cutoff point of 29 (sensitivity, 0.89; specificity, 0.90; positive predicted value, 0.88; negative predictive value, 0.87), PCF (p < 0.001) with a cutoff point of 4.25 L/s (sensitivity, 0.74; specificity, 0.85; positive predictive value, 0.71; negative predictive value, 0.85), and PCF/PVT (p < 0.001) with a cutoff point of 28.88 L/s² (sensitivity, 0.77; specificity, 0.96; positive predictive value, 0.91; negative predictive value, 0.89).

Conclusions: In patients with stable ALS, bulbar dysfunction (NBS < 29), PCF (< 4.25 L/s), and PCF/PVT (< 28.88 L/s²) could predict the risk of ineffective spontaneous cough during a respiratory tract infection.

Key Words: amyotrophic lateral sclerosis • assisted cough • neuromuscular disease • noninvasive ventilation • peak cough flow

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Respiratory problems are the main cause of morbidity and mortality in patients with amyotrophic lateral sclerosis due to hypoventilation and ineffective cough. During a chest infection, an effective cough in medically stable situations can become ineffective in these patients. What This Study Adds to the Field In patients with medically stable amyotrophic lateral sclerosis, spontaneous cough ineffectiveness during chest infections can be predicted satisfactorily using clinical and functional parameters.