Effects of early introduction of non-invasive positive pressure ventilation based on forced vital capacity rate of change: Variation across amyotrophic lateral sclerosis clinical phenotypes.

Abstract

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease associated with high morbidity and mortality. We evaluated the ability of pulmonary function tests to predict disease progression by ALS clinical phenotypes, and the timing of the introduction of non-invasive positive pressure ventilation (NIPPV). A cohort study was performed in all adult patients who fulfilled El Escorial criteria at a tertiary-care academic medical centre for veterans in the USA from 1 January 2010 to 31 December 2014. Eligible patients underwent sitting and supine forced vital capacity (FVC) and the FVC rate of change (RoC) per month was calculated. ALS Functional Rating Scale-Revised (ALSFRS-R) scores were collected. A total of 137 patients were included in our analysis. The average survival from ALS onset was 31.40 (±40.04) months. The general cohort median (IQR) RoC was -0.87 (-2.55 to 0.34)/-0.65 (-2.55 to 0.70) % per month (P=0.81) of the sitting/supine FVC, respectively. However, mean monthly RoC varied among the ALS phenotypes, with higher variation among global ALS, where greater decline in RoC was noted. The average time from ALS onset to tracheostomy was 27.88 (±22.21) months. The average sitting/supine FVC RoC for subjects requiring tracheostomy was -2.86 (±3.77)/-3.63 (±3.75) at the time of tracheostomy, compared to -1.190 (±2.38)/-1.07 (±3.78) for those who did not require the procedure. Although NIPPV use did not result in statistically significant improvements in either the sitting or supine FVC %, it did slow the RoC decline of patients with global ALS phenotypes. Initiation of NIPPV based on decline in RoC rather than the absolute value of either sitting or supine FVC may result in early stabilisation of ALS patients' pulmonary deterioration for the global clinical phenotype, and thus may have the potential for prolonging survival until tracheostomy or death.