What does the Nitrogen Wash Out method evaluate?

The Nitrogen Wash Out method is primarily used to evaluate Functional Residual Capacity (FRC), which is the volume of air remaining in the lungs after a normal expiration. This technique involves having a patient breathe in 100% oxygen, which replaces nitrogen in the lungs. As the nitrogen is washed out, the concentration of nitrogen is measured in exhaled breaths. The changes in nitrogen concentration over time allow for the calculation of FRC, providing insight into lung function.

Understanding FRC is crucial for assessing conditions that affect lung volumes, such as obstructive or restrictive lung diseases. The method directly measures the amount of nitrogen present, making it a reliable way to evaluate how much air is left in the lungs after exhalation, highlighting its importance in respiratory evaluations.