Employing the Forced Oscillation Technique for the Assessment of Respiratory Mechanics in Adults

This protocol helps to minimize biological and measurement variability to ensure the acquisition and reporting of forced oscillation technique parameters, or FOT parameters, is standardized and straightforward for the technician to follow. In addition to its ease of performance, the main advantage of FOT is its ability to provide an assessment of the distal or small airways, an area that is not easily accessible by other lung function techniques. We are beginning to see many new and exciting clinical applications for FOT, including at-home daily monitoring in lung disease as well as the optimization of ventilator settings.

Coaching proper FOT performance is different from other pulmonary function tests in that the goal is to ensure the individual is performing the test in a calm and relaxed manner while tidal breathing. Demonstrating the procedure will be Matthew Watson, a clinical exercise physiologist from our laboratory. Start by preparing supplies and materials before the individual's arrival.

Choose a quiet and comfortable environment to perform testing. Provide an adjustable chair without wheels to ensure that the individual's feet are flat against the floor. To verify impedance test load, open the calibration or verification menu in the software, then insert the test load device into the FOT device and complete the verification procedure according to the manufacturer's recommendations.

Once done, review and save the verification results. Before starting the test, let the individual know about the approximate duration of a single acquisition and the number of replicates to be taken. Inform the visual that the device will start oscillations after a brief observation period and about the sensations to be experienced from the oscillations, such as fluttering or vibrations in the chest and mouth.

Avoid swallowing during the testing period. Provide the individual with a disposable antibacterial filter and nose clip to be used for testing. The individual will have to sit upright with the feet flat on the floor and the chin facing up for the duration of the testing period.

Demonstrate to the individual to create a seal with the lips and teeth on the mouthpiece while keeping the tongue relaxed. For the testing, the individual is required to place open palms against cheeks with fingertips near the temple and thumbs following the mandibular line. The elbows should be flared in a comfortable position to ensure chest expansion.

Instruct the individual to maintain regular quiet breathing on the mouthpiece until asked to stop. While adhering to hygiene and infection control standards, perform measurements by attaching the antibacterial filter to the device. confirm that the individual is positioned correctly with the nose clip in place and mouth tightly sealed around the mouthpiece of the device.

After the individual completes several respiratory cycles of stable, passive and comfortable tidal breathing ensure that the device automatically begins acquiring data. When at least three are artifact-free breaths are acquired during a single acquisition, ask the individual to remove the mouthpiece. Identify artifacts through visual inspection.

To do so, monitor the depth or tidal volume and rate of breathing or respiratory frequency in real time during acquisition to visually ensure stable and quiet breathing patterns for each replicate. When done, inspect the replicate manually to exclude artifacts such as cough, swallowing, leak or other interruptions to flow and pressure traces that can be viewed in real time. Then review automatic software detection of artifacts.

To assess variability, acquire at least three acceptable replicates containing artifact-free breaths followed by calculating the within session coefficient variation, or CoV, for total resistance at the lowest frequency of five Hertz. If the CoV is more than 10%obtain additional replicates until the acceptable within session CoV of less than 10%When the within session CoV criteria were met, the average FOT indices were calculated as the average of measurements. The mean of all replicates was plotted for respiratory resistance and reactance at each measured frequency.

Bronchodilator assessment was performed by measuring the respiratory resistance and reactance before and after the administration of the bronchodilator. Ensuring measurements are acceptable, free of artifacts and repeatable are the most important aspects of FOT that require attention from the technician. FOT does not replace traditional pulmonary function assessments of airflow, volumes and diffusion.

These assessments are critical to achieving a complete evaluation for the lung.