Butz et al. (A-10) evaluated the duration of benefit derived from the use of noninvasive positive-pressure ventilation by patients with amyotrophic lateral sclerosis on symptoms, quality of life, and survival. One of the variables of interest is partial pressure of arterial carbon dioxide (PaCO2). The values below (mm of Hg) reflect the result of baseline test- ing on 30 subjects as established by arterial blood gas analyses. 40.0 54.5 47.0 42.0 34.0 44.3 54.0 43.0 54.0 48.0 53.9 41.8 58.0 53.6 56.9 33.0 43.1 52.4 37.9 45.0 34.5 40.1 33.0 59.9 62.6 54.1 45.7 40.6 56.6 59.0 SOURCE: M. Butz, K. H. Wollinsky, U. Widemuth-Catrinescu, A. Sperfeld, S. Winter, H. H. Mehrkens, A. C. Ludolph, and H. Schreiber, "Longitudinal Effects of Noninvasive Positive-Pressure Ventilation in Patients with Amyotrophic Lateral Sclerosis," American Journal of Medical Rehabilitation, 82 (2003) 597-604.