CPFT Practice Exam 2025 – Complete Test Prep Guide

The gas dilution method is specifically utilized in pulmonary function testing to measure lung volumes, and helium dilution is a prime example of this approach. This technique involves the patient breathing a known concentration of helium mixed with a known volume of gas. Since helium is not absorbed by the lungs, changes in its concentration can be used to calculate the volume of the lungs.

In this process, the initial and final concentrations of helium are measured, allowing for the determination of the total lung capacity (TLC) and functional residual capacity (FRC). This method is particularly useful in patients with obstructive lung diseases where other methods, like body plethysmography, may not provide accurate results due to airflow limitations.

In contrast, other devices mentioned serve different purposes; for instance, a peak flow meter primarily measures peak expiratory flow rates, helping monitor asthma and other respiratory conditions. A spirometer is used for measuring forced vital capacity and forced expiratory volume but does not utilize the gas dilution method to assess lung volumes. Lastly, an oximeter measures blood oxygen saturation and does not provide information about lung volumes at all. Therefore, the gas dilution method is exclusive to the helium dilution technique when assessing lung volumes.