Certified Pulmonary Function Technologist (CPFT) Practice Exam

During a Nitrogen washout test, if nitrogen suddenly spikes in the middle of the test, what is the likely cause?

1. The patient is breathing normally

2. The patient took their mouth off the mouthpiece or there is a leak

3. Moisture entered the system

4. The equipment needs calibration

The correct answer is: The patient took their mouth off the mouthpiece or there is a leak

A sudden spike in nitrogen levels during a Nitrogen washout test typically indicates an interruption in the integrity of the testing setup. When a patient removes their mouth from the mouthpiece or if a leak occurs within the system, it can lead to a rapid and unexpected increase in nitrogen concentration because the ambient air, which contains a higher percentage of nitrogen (around 78%), is being introduced into the system. In this scenario, the expected decrease in nitrogen levels due to the washout process is disrupted. Instead of seeing a consistent decline in nitrogen concentration as the nitrogen is washed out of the lungs, the sudden influx of atmospheric nitrogen leads to an unexpected spike. This disruption compromises the accuracy of the test, as it reflects problems with how well the patient is participating in the test or with the equipment setup itself. Other options, like a patient breathing normally, would not result in an unexpected spike in nitrogen levels as they would be continuously expiring nitrogen. Similarly, moisture entering the system generally affects baseline measurements, but it would not directly cause a sudden spike during the test. Lastly, while equipment calibration issues can lead to inaccuracies, they manifest in different ways and would not specifically cause a sudden spike in the nitrogen concentration.