Respiratory Care: Respiratory Care |

Course of Decline of Lung Function Based on Tolerance to Noninvasive Ventilation in Patients with Amyotrophic Lateral Sclerosis FREE TO VIEW

Tanmay Panchabhai, MD; Erik Pioro, MD; Loutfi Aboussouan, MD; Xiaofeng Wang, PhD; Qi Zhang, MS; Eduardo Mireles-Cabodevila, MD
Author and Funding Information

Cleveland Clinic Foundation, Beachwood, OH

Copyright 2016, American College of Chest Physicians. All Rights Reserved.

Chest. 2016;149(4_S):A533. doi:10.1016/j.chest.2016.02.556
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SESSION TITLE: Respiratory Care

SESSION TYPE: Original Investigation Poster

PRESENTED ON: Saturday, April 16, 2016 at 11:45 AM - 12:45 PM

PURPOSE: In a large cohort of patients with ALS, we sought to: 1) objectively model the course of lung function decline and 2) determine the impact of noninvasive positive pressure ventilation (NIPPV) on the pattern of decline of lung function.

METHODS: We reviewed spirometric variables on 515 patients diagnosed with probable or definite ALS (World Federation of Neurology El Escorial criteria) from 9/1/2003 to 01/31/2014. Based on the best fit from a non-parametric assessment of the data, a bi-asymptotic, four-parameter segmented non-linear mixed effects model was used to investigate the course of the predicted forced vital capacity (FVCP) in patients with ALS who were either tolerant or intolerant to NIPPV. Tolerance was defined as use of NIPPV for a minimum of 4 hours during the day. Maximization likelihood estimation with adaptive Gaussian quadrature was applied to solve the non-linear models and estimate the model parameters.

RESULTS: A bi-asymptotic model provided an excellent fit of the data suggesting an accelerated rate of decline of lung function prior to an inflection point, followed by a slowing rate of decline. When analyzed separately, FVCP was the same in intolerant and tolerant groups before the onset of lung function decline (upper asymptote: 76 and 72% respectively, p=0.08) and at final FVCP (lower asymptote: 42% and 39% respectively p=0.15). The inflection point (mid-way between the asymptotes) occurred significantly sooner in intolerant vs. tolerant patients (6.7 vs. 4.3 months prior to initiation of NIPPV; p=0.01) but the rate of loss of FVCP at that point was slower in intolerant vs. tolerant subjects (2.4% per month vs. 3.4% per month). At NIPPV initiation, the vital capacity was 46% in both groups, likely reflecting the indication for NIPPV initiation once FVCP is at or below 50%, and slope of FVCP decline was 1.1% per month in intolerant vs. 1.5% per month in tolerant subjects.

CONCLUSIONS: Decline of FVCP starts later but is more rapid in patients with subsequent adherence to NIPPV. There is no beneficial effect of NIPPV on the course of decline of spirometric variables. Importantly, by the time NIPPV is initiated, subjects have already lost about 85% of the expected range of lung function.

CLINICAL IMPLICATIONS: The association of NIPPV tolerance with rapid rate of decline may indicate predominant diaphragmatic involvement. Current guidelines for the FVCP threshold for initiation of NIPPV in patients with ALS may need to be revised to assess whether earlier NIPPV has an impact on lung function.

DISCLOSURE: The following authors have nothing to disclose: Tanmay Panchabhai, Erik Pioro, Loutfi Aboussouan, Xiaofeng Wang, Qi Zhang, Eduardo Mireles-Cabodevila

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