Fig. 4— Accuracy was assessed for all 12 device types for measuring diffusing capacity of the lung for carbon monoxide (DL,CO) used by the sites in the present study, by calculating the mean of the absolute values of the difference between the measured and target DL,CO values. Mean absolute differences plus 95% confidence intervals are presented for each machine at each of the tank gas/inspired volume (VI) combinations used. a) VI 4.5 L, low concentration of CO; b) VI 4.5 L, high concentration of CO; c) VI 3.5 L, low concentration of CO; d) VI 3.5 L, high concentration of CO. Manufacturers of the devices were as follows. Zan300: nSpire Health, Longmont, CO, USA. Spirotech: VIASYS Healthcare, Yorba Linda, CA, USA. SensorMedic: Sensor Medics, Yorba Linda. SandMKeystone: S&M Instruments Co., Doylestown, PA, USA. Piston: Piston, Budapest, Hungary. MediSoft: Medisoft, Dinant, Belgium. MedGraph: Medical Graphics Corp., St Paul, MN, USA. Lungtest 1000: MES, Krakow, Poland. Jaeger: Jaeger, Würzberg, Germany. GansHorn: Ganshorn Medizin Electronic, Niederlauer, Germany. CosMed: Cosmed, Rome, Italy. Collins: Ferraris Respiratory, Louisville, KY, USA.