Certified Transport Registered Nurse Certification Practice Exam

What phase of the capnography waveform does the plateau represent?

1. Inhalation phase

2. Exhalation phase

3. Initial phase

4. End of exhalation phase

The correct answer is: Exhalation phase

The plateau phase of the capnography waveform corresponds to the exhalation phase, specifically reflecting steady-state CO2 levels in the breath. During this phase, CO2 is being released from the lungs as a result of alveolar gas exchange, and this leads to a rise in the concentration of carbon dioxide in the exhaled air. The plateau indicates that the breath sample is primarily composed of alveolar gas, which is enriched with CO2, hence the waveforms stabilize at a certain level. This stability in the capnography reading shows that gas exchange is occurring efficiently, as the patient is continually exhaling CO2 that has been exchanged in the alveoli. Understanding the role of the plateau in the context of the full capnography waveform is crucial for transport nurses, as it provides insights into the patient's respiratory status and ventilation effectiveness.