Under what condition should pulmonary function testing be terminated?

The most appropriate condition to terminate pulmonary function testing is when there are no reproducible tracings after a set number of attempts, which in this case is indicated as 8 attempts. Reproducibility is crucial in pulmonary function tests to ensure that the results obtained are reliable and can accurately reflect the patient's lung function. If multiple attempts yield no reproducible results, it suggests that something may be amiss, such as issues with technique, effort, or patient understanding of the procedure.

In testing procedures, it's important to set a limit because continuing beyond a certain point can lead to fatigue or frustration for the patient, which may compromise further attempts as well. This limit should be practical, and standard practice often involves stopping after several attempts while still prioritizing patient safety and comfort.

The other choices involve different numbers of attempts or circumstances. For example, terminating after fewer attempts may not align with protocols that allow for sufficient data collection to assess lung function accurately. Moreover, simply terminating when the patient expresses discomfort, while important for safety, might lead to insufficient data if it occurs too early in the testing process. Hence, the correct answer emphasizes the alignment of testing standards with the need for reliable, reproducible results.