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  1. H. M. Gallo1,
  2. R. O. Crapo1,
  3. R. L. Jensen1
  1. 1LDS Hospital, Salt Lake City, UT


A DLCO simulator creates a precisely known target DLCO value by injecting known volumes and concentrations of gas into a DLCO instrument. DLCO simulations were performed weekly on each of three instrument models used in our pulmonary laboratory. High-precision test gases (± 1%) were used for both the simulator and instrument tested. An inspired volume of 4.5 L was used for all tests. At each test session eight simulations were done on each device, four each with midlevel and low-level simulated alveolar gas samples. The first trial of each set was discarded as a system flush. The remaining three trials were analyzed. A difference from target of ± 2.0 DLCO units (mL CO/min/mm Hg) was set as the threshold to initiate an investigation into possible causes of error. In addition, two bio-control subjects were concurrently tested weekly to check for trends.

The graph shows DLCO differences from target for one device. When the DLCO difference from the target value was greater than ± 2.0 DLCO units, the device was taken out of service and carefully checked for possible sources of error. On four occasions the DLCO difference exceeded the ± 2.0 DLCO unit threshold. In each instance, specific problems were identified and fixed. During the weeks that errors were found, the bio-control data did not suggest that measurement errors were present. Regular use of a DLCO simulator can help maintain high-quality test results and identifies problems that bio-control testing may not immediately identify.

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