CPFT Practice Exam 2025 – Complete Test Prep Guide

The correct choice identifies the four methods used to measure total lung capacity (TLC) accurately.

Body box, also known as body plethysmography, is a technique that assesses lung volume by measuring the changes in pressure and volume within a sealed chamber as the patient breathes. This method allows for an accurate determination of lung volume, including TLC, by taking into account the air trapped in the lungs that is not measured by standard spirometry.

Helium dilution involves having the patient breathe in a known concentration of helium, which is soluble in blood and not absorbed by the lungs. By measuring the change in concentration of helium after it mixes with the air in the lungs, the total lung capacity can be calculated.

Nitrogen washout is another method where the patient breathes 100% oxygen, which helps wash out the nitrogen that was initially in the lungs. By calculating the volume of nitrogen exhaled, the total lung capacity can also be estimated.

Radiologic estimates, while useful for assessing lung volume, are not typically classified as direct measurements of TLC in the same way as the other methods listed. This differentiates the correct answer from other options that may include methods not primarily used or less reliable for assessing total lung capacity compared to the selected