Final answer:
The technologist should report the average of the two trials of the exhaled nitric oxide test (FENO), since the two results are consistent and within an expected range of variability.
Step-by-step explanation:
A subject performing an exhaled nitric oxide test (FENO) with results showing 45 parts per billion (ppb) in the first trial and 42 ppb in the second trial should proceed with reporting the average of the two trials. This is based on the assumption that the FENO values are consistent and within an acceptable range of variability. As the results are fairly close to each other, they do not suggest a technical error or a significant inconsistency that would warrant repeating the test or dismissing it as inconclusive. Moreover, there is no suggestion that the flow rate should be changed, as this would likely be based on protocol or troubleshooting rather than standard result interpretation.