[Evaluation of ventilatory functions in amyotrophic lateral sclerosis]

As the clinical signs of amyotrophic of lateral sclerosis (ALS) are late and not specific, spirometric measurements, study of respiratory strength muscles and analysis of night respiratory parameters are used to evaluate ventilatory functions. The prognostic value of vital capacity is well established, but with a poor sensitivity to detect the initial form of ALS. Gazometric parameters remain normal for a long time. Hypercapnia is late and due to a major reduction in the force of the inspiratory muscles. Level of diurnal venous bicarbonate could detect nighttime hypoventilation. Noninvasive techniques (Pimax, Pemax, snifftest) are available to explore the strength of respiratory muscles. Sleep is characterized by a long period of hypoventilation, essentially during REM-sleep. There are no guidelines concerning the appropriate mode, type and rhythm of explorations of diurnal and nocturnal respiratory functions.