Postural change of forced vital capacity predicts some respiratory symptoms in ALS

The detection of respiratory muscle weakness in ALS is necessary to plan in itiation of noninvasive positive pressure ventilation and begin discussion of advanced directives. The authors measured the erect seated and supine fo rced vital capacity (FVC) in 38 patients with ALS and 15 controls. The supi ne FVC is significantly lower and the erect - supine FVC difference is sign ificantly greater in patients with complaints of dyspnea, orthopnea, and da ytime fatigue.