Respiratory measurements, respiratory symptoms, and quality of life in ALS: results from the REVEALS study

<i>Objective</i>: Progressing respiratory weakness throughout the course of amyotrophic lateral sclerosis (ALS) is clinically associated with distressing symptoms, including dyspnea, orthopnea, and difficulty clearing secretions. Fatigue, poor sleep, and reduced quality of life are also considered to be associated with declining respiratory function. Respiratory measurements guide prescription of interventions, which aim to alleviate symptoms. The relationships between respiratory measurements and patient reported symptoms are currently unclear. <i>Method</i>: The REVEALS study was a longitudinal, observational, multisite study of decline in respiratory function in people with ALS attending six European centers. Respiratory measures (forced and slow vital capacity (F/SVC), sniff nasal inspiratory pressure (SNIP), and peak cough flow) were collected, as were the presence of respiratory symptoms and simple quality of life, fatigue and sleep measures. We used Bayesian's multivariate models to explore the associations of the respiratory measures with outcome variables. <i>Results</i>: Two hundred and eighty participants completed in-person assessments over a median of 8 (IQR 2.3, 14.1) months, with 974 data collection timepoints. The probability of reporting symptoms including dyspnea, orthopnea, and difficulty clearing secretions increased with decreasing respiratory measurement scores. The probability of reporting moderately low quality of life and moderate fatigue also increased with decreasing test scores, but reported sleep quality was not associated with respiratory scores. <i>Conclusion</i>: Respiratory weakness in people with ALS was associated with symptoms including dyspnea, orthopnea, and difficulty clearing secretions. The probability of reporting symptoms increased incrementally as respiratory weakness increased, supporting the use of both respiratory measurements and the presence of symptoms in making decisions about clinical interventions.