Oscillometry Healthcare Professional Toolkit

• Be used across the lifespan
• Assess young children
• Monitor an individual’s environmental or occupational exposures over time
• Provide insight into airway caliber
• Assess reduced lung compliance
• Detect small airway dysfunction
• Track treatment response after bronchodilator or anti-inflammatory therapy
• Predict COPD exacerbations
• Manage disease long-term

Oscillometry may lead to improved health outcomes by:

• Objectively evaluate early changes in respiratory health and response to medication therapy in populations when other meds are not available.
• Predicting COPD exacerbations. 
• Informing treatment responsiveness and treatment plans during an asthma exacerbation 
• Reactance parameters were found to be more sensitive in identifying poor asthma control than spirometry, supporting the use of oscillometry to complement spirometry in the clinical management of asthma
• By assessing lung abnormalities early, oscillometry may then reduce the need for medications which could then reduce healthcare costs and the long-term effects of high-dose inhaled corticosteroids.  

The current gold standard test used to diagnosis asthma and COPD is spirometry. For this reason, most experts recommend that oscillometry should not be used as a standalone diagnostic tool but rather in conjunction with spirometry, plethysmography, and clinical history and other investigations such as chest imaging and appropriate blood work.

However, oscillometry can be clinically useful as outlined above in the “What Is the Clinical Usefulness of Oscillometry in the Assessment and Management of Lung Disease” section.

Indications for oscillometry use include:

1. If the patient is unable to perform spirometry, oscillometry is recommended (i.e. too young, too old, or situations where patients are unable to follow instruction to perform spirometry; presence of contraindication to forced expiratory maneuvers but at risk for undiagnosed lung disease). Normal oscillometry can rule out underlying lung disease. Abnormal oscillometry indicates need for further assessment. 
2. If results from spirometry are normal, but the patient remains symptomatic, oscillometry is recommended and subsequent follow up is indicated. 
3. Oscillometry can be helpful in early detection and diagnosis of lung disease as it is more sensitive than spirometry at assessing small airway dysfunction.
4. Oscillometry can be used to monitor medication treatment response.
5. Monitor an individual’s environmental or occupational exposures over time. 
6. Oscillometry can also help predict COPD exacerbations and can be used during an exacerbation to inform treatment. 
7. Assess bronchodilator responses and airway hyperresponsiveness when spirometry is not possible or in addition to spirometry. 

When implementing oscillometry in clinical practice, consider the following:

1. Have at least one clinic staff adequately trained in performing the procedure. 
2. Establish written protocols and procedures to match the intended use and audience 
3. Testing can be performed in an exam or procedure room. Some devices are portable and can be performed at bedside.
4. Oscillometry should be conducted first, if other lung function tests such as spirometry are planned during the same clinic visit. This ensures that oscillometry is evaluated at FRC. Tests that require deep breaths and forced maneuvers will change the lung volume.
5. Testing generally takes 15 minutes if it measures a patient’s baseline lung function. If obtaining a pre- and post-bronchodilator response, 30 minutes should be allocated.

See “How to conduct an oscillometry test” section in the downloadable “Oscillometry:  A toolkit for healthcare professionals” for more information.  

Steps to conduct an oscillometry test include:

1. Equipment and software set up
2. Patient preparation
3. Quality control during the test
4. Determine acceptable measurements
5. Determine measurement exclusion
6. Ensure measurement repeatability
7. Post-bronchodilator response – optional
8. Reporting results

Steps to Oscillometry Interpretation:

Please refer to the video above and the downloadable Oscillometry: A toolkit for healthcare professionals for further details on oscillometry test result interpretation.

Steps to interpretating oscillometry test results include:

1. Check quality metrics (COV1 coherence)
   1. Coefficient of Variation: <10% for adults, <15% for children (R5 parameter)
   2. Repeat at least 3 tests for a valid session
2. Review R5, total resistance
   1. R5 (resistance at 5Hz) reflects the total respiratory system resistance from central and peripheral airways
   2. Increased R5 suggests overall airway narrowing, as in asthma, COPD, or acute bronchoconstriction.
   3. Normal R5 means total airway resistance is within expected limits
3. Review R5-R20, small airway resistance
   1. R20 (resistance at 20 Hz) primarily reflects large/central airways
   2. R5-R20 means small airway narrowing, often the earliest sign of obstructive lung disease
   3. A normal R20 but elevated R5-R20 can indicate isolated small airway disease
   4. R19 and R5-19 can be interpreted in the same way as R20 and R5-20
4. Review X5:   Small airway reactance
   1. X5 (reactance at 5 Hz) reflects the elastic and inertial properties of peripheral airways
   2. More negative increased X5 values means stiffer, less compliant small airways
   3. This is seen in restriction, such as fibrosis or interstitial lung disease and in severe small airway obstruction, such as asthma and COPD
5. Review AX:   Area under the Reactance Curve
   1. AX is the integrated area under the reactance curve from 5 Hz to Fres (resonant frequency or zero-crossing)
   2. Increased AX indicates greater small airway dysfunction and can amplify findings from X5
   3. AX is highly sensitive to early changes in small airways
6. Identify the pattern (peripheral, restrictive, obstructive)
7. Add within-breath analysis, expiratory flow limitation or inspiratory flow limitation detection
8. Consider reversibility, pre- and post-bronchodilator

According to technical standards supported by the American Thoracic Society (ATS) and European Respiratory Society (ERS), oscillometry (FOT) is used to detect asthma through measures of increased respiratory resistance (R) and reactance (X).   Recommended bronchodilator responsiveness (BDR) thresholds for asthma, based on the 95^th percentile in healthy individuals, are defined as:

• R5 ↓ by ≥40%
• X5 ↑ by ≥50%
• AX ↓ by ≥80%

• Lack of device and software standardization
• Limited guideline support
• Interpretation challenges
• Technical challenges
• Clinical efficacy evidence
• Cost and equipment availability
• Inability to bill for both oscillometry and spirometry at the same visit.  
• Cost and equipment availability 

1. Refer to the manufacturer's instruction manual for specific device instructions. 
2. Select New Patient, if appropriate, and enter the patient's information such as first and last names, date of birth, birth sex, height, weight and smoking history. 
3. Ensure that the correct waveform is selected depending on the device.  
4. King (2020) recommends performing regular biological controls as part of your clinic’s procedures. 
5. Ensure that the appropriate set of reference values is selected (Deprato, 2022). Chang (2022) recommends the following reference values: Oostveen or Brown for adults and Nowowiejska for children ages 3 to 17. However, newer reference equations for pediatrics are now available (Ducharme, 2025). 
   NOTE: The preferred and availability of reference values may differ depending on the patient population and oscillometry device manufacturer. It is ideal to use the reference equations developed with the specific device that is being used. 

1. Follow the normal screening procedures for the pulmonary function lab or clinic. There is no evidence that oscillometry transmits respiratory pathogens (Wu, 2021). 
2. Ensure that the patient has not had any recent dental or facial surgeries, such as tooth extractions, and can form a proper tight seal around the mouthpiece. 
3. Ensure that the patient is as relaxed as possible, is not wearing tight-fitting clothing and withholds from tobacco use and vigorous exercise at least 1 hour prior to testing. 
4. Perform oscillometry prior to other pulmonary function tests, such as spirometry or exhaled nitric oxide (FeNo) testing.  
5. Withhold bronchodilators prior to testing, unless otherwise instructed by a referring provider. Record patient's usage of bronchodilators, dosage, time/date of last administration and any medication allergies. 
6. Verify the patient's information: first and last names, date of birth, birth sex and height. 
7. Measure the patient's height without shoes, with feet together, standing as tall as possible with the eyes level and looking straight ahead, and the back flush against a wall or flat surface.  
   NOTE: For patients unable to stand erect, height may be estimated using arm span. For patients aged 25 years or older, where height measurements have been made previously in the same laboratory, remeasuring height at subsequent visits within 1 year may not be necessary. 

1. Attach a single-patient-use bacterial/viral filter to the oscillometry device.
2. Ensure that the oscillometry device is ready in the testing mode.
3. Explain the test to the patient.
   • Describe the sensation generated by oscillations such as "vibrations" or "fluttering."
   • Instruct the patient to breathe normally while holding their cheeks with their palm and fingers and using their thumbs to support the soft tissue of the jaw during measurements. If they are unable to hold their cheeks themselves, you may hold it for them.
   • Explain to the patient that swallowing should be avoided and the tongue must be below the mouthpiece during the test.
   • It can be helpful for younger children to first handle and put on the nose clips and practice putting the oval end of the filter in their mouth.
4. Positioning:
   • Device:If holding the device, the operator should sit or stand in front of the patient and be able to view both the patient and the computer screen showing the measurement recording.
     • If using a support arm, make sure the device is positioned so the mouthpiece is directly in front of the participant’s mouth and the participant’s torso is upright without slouching down or reaching up.
   • Patient:The patient should sit upright in a chair with feet on the floor, or they may sit in their caregiver’s lap.
     • The operator can stand behind the participant to hold cheeks while watching the screen and checking for mouth seal.
5. Cheek Support: The patient (if able) should gently support their cheeks with their hands with thumbs under jawbone (not too tight). If unable, another person can stand behind the patient and apply very gentle pressure to the patient’s cheeks. If a patient is sitting in a caregiver’s lap, a caregiver can hold cheeks.
6. Nose clip: Nose clip should completely seal the nasal passages. Use tissue paper if the nose clip is slipping. If a child is not tolerating, another person can gently pinch the child’s nose shut.
7. Mouth Seal: Mouth should completely seal around the filter opening so that there is no air leak.
8. Tongue: Tongue should not occlude filter opening and can be positioned under the filter opening.
9. Head Tilt: Gently position the device such that the participant faces approximately 15 degrees upwards from the horizontal plane to ensure there is no compression on the upper airways that could lead to elevated resistance readings.
10. For young children, a video may provide a needed distraction. Ensure the video screen is directly in front of the participant or slightly above eye level during the test.
11. Ask the patient to wet his/her lips before wrapping them around the mouthpiece to form a proper, tight seal.
12. Instruct the patient to continue steady, quiet breathing through the filter. NOTE: Supplementary oxygen must be turned off during measurements to avoid any drift into the oscillometry device.
13. Remind the patient of the 30 second test duration and the minimum requirement of three measurements.
14. Before starting the test, watch for at least 3 steady breaths on the testing screen to ensure that the patient is breathing at their normal resting respiratory rate. It is helpful to take a baseline respiratory rate before doing the test for reference. Coach patients to slow breathing rate if they are breathing faster than normal.
15. Start recording. Continue watching patient and screen, coach gentle steady breathing with consistent tidal volume and respiratory rate, and make sure mouth is sealed around the filter. NOTE: During the test, inform the patient of the time remaining during each measurement.

1. Ensure that the patient’s breathing during the test is representative of their resting breathing state before they start the test.
2. During the measurement recordings, watch the breathing traces and patient behavior. Things to observe and correct:
   • Leak around the mouthpiece
   • Nasal passages not fully occluded
   • Rapid breathing that was not present before the test started
   • Very slow or deep breathing that was not present before the test started
   • Irregular/variable breathing or combinations of rapid/deep/shallow breathing
   • Breath holding or glottis closure
   • Tongue occluding the mouthpiece opening
   • Swallowing, coughing, laughing, talking, or humming
3. Measurement Acceptability: At least 3 (ideally at least 5) breaths that are free from artifact in each recording.
   • Oscillometry device software programs may have algorithms that automatically exclude breaths with artifacts, and manual exclusions may be possible.
   • Note: Children normally have a higher respiratory rate and will have many breaths over a 20–30 second recording. Adults will have a slower respiratory rate and the recording time may need to be extended to have 3–5 breaths in one recording.
   • The R and X values that are reported for each individual recording are averaged from the non-excluded data collected over that recording period.
4. After obtaining the first 1–2 measurements, review the results and the breathing traces and coach the patient if needed. Look for steady breathing in the time traces—there should be minimal variation in tidal volume and respiratory rate during the recording. Impedance measurements are sensitive to breathing volume and rate. It is important for the breathing volume and rate to reflect the patient’s resting state.
5. Review the plots of R and X across the spectrum of frequencies measured.
   • Typically, R at the lowest frequency (e.g., R5) will be greater than or similar to R at the next highest frequency (e.g., R10 or R11). The R curve should not bend significantly towards zero.
   • Similarly, X at the lowest frequency (e.g., X5) should be less than X at the next highest frequency (e.g., X10 or X11). The X curve should not bend significantly towards zero.
   • If these paradoxical curved bends are present, this could indicate leaking and/or panting into the device. Check that the patient has a proper mouth seal and is breathing at their resting rate.
   • Caution should be used in interpreting the 5 Hz values in these cases as they may be artificially closer to zero due to breathing and/or signal processing artifact.
   • If available, choice of a pediatric waveform starting at a higher frequency (e.g., 7 or 8 Hz) may improve results in the preschool age group who naturally have a higher respiratory rate.
6. Continue taking 3–4 more measurements and reviewing results.
   • Unlike spirometry, where the single “best” maneuver is selected for reporting, the current convention is to report the average of each R and X value from at least 3 acceptable measurements.
   • It is advisable to take more than the minimum of three measurements to ensure the possibility of including at least 3 acceptable measurements on average.
7. Measurement Exclusion:
   • Measurements with breathing artifacts/abnormal patterns or obvious abnormalities, or that do not include at least 3 whole breaths, should be excluded from the test average.
   • R and X curves that fall significantly out of the cluster of the other measurement curves (clear outliers) and are accompanied by breathing artifact or evidence of non-resting breathing patterns should be excluded from the test average.
   • Coherence is a statistical measure that shows how reliable the signal is between the pressure oscillations sent into the airway and the airflow measured coming out. High coherence (close to 1) means there is a good signal, little noise, and a reliable measurement. Low coherence means the signal is contaminated by noise, irregular breathing, coughing, swallowing, leaks, or movement. In the past, coherence was used to judge if a test was good quality. However, current guidelines indicate that you should not rely on coherence as a standalone criterion for measurements of acceptability.
8. Measurement Repeatability:
   • An acceptable test has at least 3 repeatable measurement recordings that each have 3–5 acceptable breaths.
   • Per current guidelines, repeatability means that the coefficient of variation (CoV = standard deviation/mean) in R5 (or the lowest frequency resistance) is:
     • CoV < 15% in children
     • CoV < 10% in adults
   • In addition, the R and X curves should not show significant variability across the frequency spectrum.

1. Administer bronchodilator via a valued-holding chamber. Ensure acceptable technique. 
2. Record the method and number of doses administered.  
3. Wait for at least 15 minutes.  
4. Repeat above testing steps assess post-bronchodilator response  

1. Discard patient's mouthpiece and nose clip.
2. Use disinfectant wipes to clean the oscillometry device and patient's chair.

1. Include patient's first and last names, height, age, and birth sex.
2. Include input signal frequencies and duration of individual recordings.
3. Report the mean of acceptable and reproducible measurements and the CoV for these reported measurements.
4. Select and report reference equations.
5. Include impedance graph demonstrating Rrs and Xrs versus oscillation frequency.
6. Include post-bronchodilator response with dosage and method of administration including z-scores and absolute percentage change - optional