Long-Term Stability of a Portable Carbon Monoxide Single-Breath Diffusing Capacity Instrument.
BACKGROUND
The 2005 American Thoracic Society/European Respiratory Society guidelines for single-breath diffusing capacity of the lung for carbon monoxide (DLCO) recommend a weekly biological control test and/or DLCOsimulator to detect instrument error drift. Very little has been published regarding the results of such a quality assurance program. Our aim was to analyze the long-term stability of a portable DLCOinstrument.


METHODS
We used a new EasyOne Pro system and checked its accuracy using a DLCOsimulator with 2 reference gases (concentration A: carbon monoxide [CO] = 0.1% and helium = 6.52%; concentration B: CO = 0.08% and helium = 7.21%) during the first 3 y of use in our large clinical laboratory. To detect instrument drift, a healthy woman (MSC), age 43 y old at baseline, tested herself every week during this period of time.


RESULTS
More than 6,000 spirometry and 5,000 DLCOmaneuvers were done using this instrument for patients during these 3 y. There were no failures in the daily volume and flow checks or the CO and helium calibration checks performed automatically by the instrument. The differences between the simulator DLCOand the measured DLCOwere -0.91 ± 1.33 mL/min/mm Hg and -0.61 ± 1.45 mL/min/mm Hg for concentration A and concentration B, respectively. The results of the 110 biological control tests were: mean 30.8 ± 1.7 mL/min/mm Hg (95% CI 30.5-31.1), coefficient of variation of 5.4% in DLCO, and repeatability of 2.5 mL/min/mm Hg. Only 4 measurements were outside ±3 mL/min/mm Hg (3.6%). Her mean alveolar volume was 4.2 ± 0.25 L with coefficient of variation of 6.2%; her inspired volume was 3.05 ± 0.14 L, and coefficient of variation = 4.5%.


CONCLUSIONS
Measurements of DLCOwere stable over the 3-y period without any need for manual recalibration of the instrument. The biological control was as good as the DLCOsimulator to evaluate this kind of device in a long-term laboratory quality control program.
Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas," México, Distrito Federal, México.
Laura
L
Gochicoa-Rangel
Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas," México, Distrito Federal, México.
Rogelio
R
Pérez-Padilla
Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas," México, Distrito Federal, México.
Juan Carlos
JC
Vázquez-García
Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas," México, Distrito Federal, México.
Mónica
M
Silva-Cerón
Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas," México, Distrito Federal, México.
Silvia
S
Cid-Juárez
Departamento de Investigación en Epidemiología y Ciencias Sociales en Salud, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas," México.
David
D
Martínez-Briseño
Department of Medicine, University of Arizona, Tucson, Arizona.
Paul L
PL
Enright
Department of Medicine, Pulmonary Division, University of Utah, Salt Lake, Utah.
Robert
R
Jensen
Departamento de Fisiología Respiratoria, Instituto Nacional de Enfermedades Respiratorias "Ismael Cosío Villegas," México, Distrito Federal, México. luistorreb@gmail.com.
Luis
L
Torre-Bouscoulet
D000328:Adult; D002248:Carbon Monoxide / Q000378:metabolism*; D005260:Female; D006801:Humans; D011653:Pulmonary Diffusing Capacity / Q000295:instrumentation*; D011786:Quality Control; D015203:Reproducibility of Results; D013997:Time Factors
D002248:Carbon Monoxide
biological control; diffusing capacity for carbon monoxide; quality control; simulator