The most common cause of death in patients with amyotrophic lateral sclerosis (ALS) is respiratory failure, often in the period of 2–5 years, with a small percentage of patients surviving up to 10 years or more. The aim of the study was to evaluate the significance of pulmonary function tests in prediction of mortality and definition of indications for noninvasive mechanical ventilation (NIMV).

Material and methods:
This retrospective-prospective study was performed at the Clinic of Pulmonology, Clinical Centre of Serbia in the period from January 2015 to December 2017. Patients with diagnosis of ALS established according to El Escorial criteria were included.

The study included 76 patients with ALS, 50 (65.85%) with spinal and 26 (34.2%) with bulbar form of disease. Forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were higher in spinal form of ALS, and the difference was statistically significant when compared to bulbar form. Form of disease, FVC < 70%, maximum inspiratory pressure (PImax) < 50 and maximum expiratory pressure (PEmax) < 50 were significant factors for survival. The patients with bulbar form of disease had 2.174 (95.0% CI: 1.261–3.747) higher risk for death.

Our study points to the significance of timely application and early start of NIMV in patients with ALS as an important approach to defer functional impairment, which would mean that the criteria, in our country, for application of these devices must be changed, not only regarding the value of current functional diagnostic tests used in everyday practice in patients with ALS but also in regard to the introduction of new diagnostic tests, such as sniff nasal inspiratory pressure and/or polysomnographic testing.