In patients with amyotrophic lateral sclerosis (ALS), non-invasive mechanical ventilation (NIV) is usually initiated in an in-hospital regime. The investigators evaluated if NIV initiated in an outpatient setting can be as effective as regards patients' adherence. The investigators also evaluated factors predicting NIV adherence and disease progression.

All patients with a definite ALS diagnosis, aged > 18 years, referred to the ALS outpatient clinics of the Fondazione Salvatore Maugeri Institute of Lumezzane (Brescia) and Istituto Don Gnocchi Onlus (Milano), Italy, for respiratory functional assessments for the purpose of early initiation of NIV were considered. Patients who were in clinically stable condition and without chest infections during the previous 3 months were considered eligible for the study.

Between March 2011 and March 2014, during an outpatient visit, the patients were randomized 1:1 to two groups for NIV initiation: outpatient vs. inpatient protocol.

In both groups a diurnal NIV initiation trial was performed using pressure-support ventilators in spontaneous/timed mode with a preset tidal volume (300 ml/kg) and a fixed back-up respiratory rate (12 breaths/min). The trial included: choice of the mask, setting of ventilator pressure, at least 2 hours of NIV under supervision.

Then, the patients underwent the nighttime NIV initiation trial for a maximum of 20 nights according to the outpatient vs. inpatient protocol.

NIV trial was stopped when: 1) patients used NIV > 4 hours/night for 3 consecutive nights, 2) patients and caregivers were able to manage with ventilator, 3) patients failed after 10 consecutive educational sessions.

At enrollment (T0), the end of NIV initiation trial (T1) and after 3 months from the end of the trial (T2) respiratory function tests, blood gas analysis, and sleep study were performed.

At T1 the investigators assessed NIV acceptance (as a minimum of 3 consecutive days >4 h/night), and dyspnea symptoms by VAS (day/night), staff and patients' satisfaction.

At T2: NIV adherence (>120 h/month) and patients' satisfaction.

Inclusion Criteria:

• consecutive patients
• definite ALS diagnosis
• aged > 18 years
• in clinically stable condition
• referred to the ALS outpatient clinics of the Fondazione Salvatore Maugeri Institute of Lumezzane (Brescia) and the Istituto Don Gnocchi Onlus (Milano), Italy for respiratory functional assessment for the purpose of early initiation of NIV
• no chest infections during the previous 3 months.

Exclusion Criteria:

• cognitive impairment
• refusal to participate
• severe comorbidities and contraindications to NIV (arrhythmias, cardiac failure, history of pneumothorax)
• distance from hospital > 40 km, travel problems to attend the outpatient clinic