A Preliminary Investigation of Acoustic Features for Remote Monitoring of Respiration in ALS

There is a substantial need to establish reliable approaches for low-burden at-home monitoring of respiratory function for people with amyotrophic lateral sclerosis (PALS). This preliminary study assessed the potential of acoustic features extracted from a smartphone passage reading task to serve as clinically meaningful outcome measures reflecting instrumental and self-reported respiratory function measures.

Thirty-six PALS completed an in-clinic slow vital capacity (SVC) task, followed by at-home completion of surveys and audio recording of a reading passage using a smartphone application. Speaking rate and pause features were extracted offline. Correlation analysis evaluated the relationship between the acoustic features and both instrumental (SVC) and self-reported (respiratory subscale of the self-entry version of the ALS Functional Rating Scale-Revised; ALSFRS-RSE) measures of respiratory function. Receiver operator characteristic (ROC) with area under the curve (AUC) analysis evaluated the utility of acoustic features for classifying participants with and without respiratory involvement.

SVC and respiratory self-ratings were significantly correlated with pause, but not rate, measures. Percent pause time was the most strongly correlated acoustic feature with both SVC (r = -0.62) and ALSFRS-RSE respiratory subscale ratings (r = -0.43). ROC analysis revealed that percent pause time classified participants presenting with respiratory involvement based on instrumentation (SVC < 70% predicted [AUC = 0.70]; SVC < 50% predicted [AUC = 0.88]) and self-ratings when using the respiratory ALSFRS-RSE score cut-off of < 11 (AUC = 0.78), but not < 12 (AUC = 0.61).

Percent pause time, extracted from a smartphone-recorded passage reading, offers a promising index for remote assessment and monitoring of respiratory function in PALS.