Characteristics of impaired voluntary cough function in individuals with amyotrophic lateral sclerosis

Abstract

Objective: Although cough impairment (dystussia) is common in individuals with amyotrophic lateral sclerosis (ALS) and contributes to a reduced physiologic capacity to defend the airway, characteristics of dystussia have not yet been delineated. Therefore, we aimed to compare voluntary cough spirometry airflow patterns between individuals with ALS and healthy age and gender-matched controls.

Methods: Thirty-two individuals with a diagnosis of probable-definite ALS (El-Escorial Criterion) and 29 healthy age and gender-matched controls underwent voluntary cough spirometry testing. Two blinded raters derived six objective voluntary cough airflow measures including: peak inspiratory phase duration, peak inspiratory flow rate, compression phase duration, peak expiratory rise time, peak expiratory flow rate, and cough volume acceleration. Independent samples t-tests with Cohen's d effect sizes were performed between Healthy versus ALS groups for cough metrics (alpha =0.05).

Results: ALS individuals demonstrated prolonged inspiratory phase and expiratory phase rise time durations, reduced inspiratory and expiratory flow rates, and lower cough volume acceleration during voluntary cough production compared with healthy controls (p < 0.05). No differences in compression phase duration were observed (p > 0.05).

Conclusions: This study compared characteristics of voluntary cough airflow patterns of individuals with ALS to healthy-matched controls. Findings identified impairments in both inspiratory and expiratory voluntary cough airflow, resulting in slower, weaker, and thus less effectiveness voluntary cough production in ALS individuals. These data afford insight into the impaired physiology underlying inadequate airway clearance and secretion management in individuals with ALS.

Keywords: Voluntary cough; airway protection; amyotrophic lateral sclerosis; dystussia; spirometry.

Figure 1.

Schematic of the experimental setup for voluntary cough testing. LabChart (ADInstruments, Version 8) interfaced with the power lab and spirometry bridge to record cough motor parameters.

Figure 2.

A voluntary cough spirometry waveform of a healthy control depicting the three primary phases of cough: inspiratory compression and expiratory, from which objective temporal airflow parameters are computed.

Figure 3.

Voluntary cough spirometry depicting A) cough flow with distinct inspiratory and expiratory parameters in a healthy control, and aberrant cough flow in two individuals with ALS with B) spinal-onset and C) bulbar-onset disease type.