Certified Respiratory Therapist Practice Exam

If a back extrapolated volume during FVC testing is less than 150 ml, what does this indicate?

1. The test was invalid

2. The patient performed well

3. The patient hesitated during the test

4. The patient needs to be recounseled on technique

The correct answer is: The patient performed well

A back extrapolated volume of less than 150 ml during Forced Vital Capacity (FVC) testing suggests that the patient did not have a significant delay before starting the forced exhalation. This indicates good compliance with the test procedure, where the patient is expected to initiate the expiration immediately after the maximal inspiration, reflecting a well-executed maneuver. A small back extrapolated volume implies that the patient effectively began exhaling without hesitation, which typically correlates with the patient performing well during the test. In this context, a minimal back extrapolated volume can also enhance the reliability of the FVC results, supporting the notion that the forced expiration was performed correctly and providing a clearer assessment of the patient's lung function.