Voluntary Cough Airflow Differentiates Safe Versus Unsafe Swallowing in Amyotrophic Lateral Sclerosis

Abstract

Dysphagia and aspiration are prevalent in amyotrophic lateral sclerosis (ALS) and contribute to malnutrition, aspiration pneumonia, and death. Early detection of at risk individuals is critical to ensure maintenance of safe oral intake and optimal pulmonary function. We therefore aimed to determine the discriminant ability of voluntary cough airflow measures in detecting penetration/aspiration status in ALS patients. Seventy individuals with ALS (El-Escorial criteria) completed voluntary cough spirometry testing and underwent a standardized videofluoroscopic swallowing evaluation (VFSE). A rater blinded to aspiration status derived six objective measures of voluntary cough airflow and evaluated airway safety using the penetration-aspiration scale (PAS). A between groups ANOVA (safe vs. unsafe swallowers) was conducted and sensitivity, specificity, area under the curve (AUC) and likelihood ratios were calculated. VFSE analysis revealed 24 penetrator/aspirators (PAS ≥3) and 46 non-penetrator/aspirators (PAS ≤2). Cough volume acceleration (CVA), peak expiratory flow rise time (PEFRT), and peak expiratory flow rate (PEFR) were significantly different between airway safety groups (p < 0.05) and demonstrated significant discriminant ability to detect the presence of penetration/aspiration with AUC values of: 0.85, 0.81, and 0.78, respectively. CVA <45.28 L/s/s, PEFR <3.97 L/s, and PEFRT >76 ms had sensitivities of 91.3, 82.6, and 73.9 %, respectively, and specificities of 82.2, 73.9, and 78.3 % for identifying ALS penetrator/aspirators. Voluntary cough airflow measures identified ALS patients at risk for penetration/aspiration and may be a valuable screening tool with high clinical utility.

Keywords: Amyotrophic lateral sclerosis; Aspiration; Cough; Deglutition; Deglutition disorders; Screen.

Figure 1

Example of voluntary cough spirometry waveform depicting derived objective measures. Four temporal measures that include inspiratory phase duration, compression phase duration, expiratory phase duration and peak expiratory flow rate (PEFR) are shown. In addition, measures of peak inspiratory flow rate (PIFR) and peak expiratory flow rate (PEFR) are identified. Cough volume acceleration (CVA) is not depicted but is calculated by dividing PEFRT by PEFR (i.e. CVA=PEFR/PEFRT).

Figure 2

Videofluoroscopic image and voluntary cough airflow waveform examples from an ALS patient who demonstrated safe swallowing (PAS=1, Figure 2A) and an ALS patient who aspirated without a cough response (PAS=8, Figure 2B). The aspirator demonstrated a smaller peak inspiratory flow rate (PIFR), a longer compression phase duration (CPD), and a smaller peak expiratory flow rate (PEFR). Asp= aspiration.

Figure 3

Receiver operator curves (ROC) for voluntary cough airflow measures that were significant to identify penetrator/aspirators (PAS ≥3).