Patient-ventilator asynchrony with nocturnal noninvasive ventilation in ALS

Background: American Academy of Neurology (AAN) practice parameters for amyotrophic lateral sclerosis (ALS) include noninvasive positive pressure ventilation (NIV) for a forced vital capacity (FVC) ≤50%predicted. Despite the limited ability of NIV systems to deliver adequate ventilation synchronous with patient demand, nocturnal patient-ventilator asynchrony has not been systematically studied in patients with ALS prescribed such NIV.

Methods: Twenty-three consecutively recruited patients with ALS reporting consistent use of nocturnal NIV (nNIV) prescribed for FVC ≤50% or orthopnea underwent home nocturnal polysomnography (PSG) on their current nNIV regimen (all used bilevel positive airway pressure). PSG recorded airflow, NIV pressures, thoracic and abdominal respiratory effort, and O₂ saturation by pulse oximetry (SpO₂). Patient-ventilator asynchrony was calculated as an asynchrony index (AI), the number of episodes of asynchrony per hour of nocturnal recording time (RT).

Results: Nineteen patients had an adequate PSG. Their mean AI was 69 ± 46 SD (range 15–146/hour). Mean asynchrony time as a percent of RT was 17% ± 19%. Mean nadir SpO₂ was 85% ± 7%. In multiple regression analysis, no demographic, functional severity (including FVC and ALS Revised Functional Rating Scale), or NIV (including pressure levels and duration of NIV prescription) variables were significantly predictive of degree of patient-ventilator asynchrony.

Conclusions: These findings document frequent nocturnal patient-ventilator asynchrony in patients with ALS consistently using nNIV prescribed as per current AAN practice parameters, and suggest that use of nNIV per these parameters is unlikely to provide patients with ALS optimal nocturnal ventilatory support.