Forced Oscillation Technique
Lung Oscillometry (FOT)
Non-effort dependent lung function testing ideal for children, elderly patients, and those who struggle with traditional spirometry. FOT excels at detecting small airway dysfunction, especially useful to detect smoking related damage.
What is FOT / oscillometry?
Forced Oscillation Technique (FOT), also called Oscillometry, is an advanced lung function test that measures airway resistance and reactance using gentle sound waves. Unlike spirometry, it only requires you to breathe normally through a mouthpiece.
During the test, small pressure oscillations are superimposed on your normal breathing. The device analyzes how your airways respond to these oscillations, providing detailed information about both large and small airway function.
Who should consider a FOT test?
Children
FOT requires only normal breathing, making it perfect for young children who cannot perform the forceful maneuvers needed for spirometry.
Elderly patients
Older adults with fatigue or coordination difficulties can easily complete FOT testing without the effort required for standard PFT.
Poor spirometry effort
When patients cannot produce acceptable spirometry due to coughing, pain, or breathing difficulty, FOT provides reliable alternative data.
Smokers
FOT is highly effective for the early detection of changes in smokers. It offers valuable insights into lung health before symptoms become prominent.
What to expect during the test
The FOT test is quick, painless, and usually takes upto 10 minutes only.
Sit comfortably
You will sit comfortably and breathe normally through a mouthpiece while wearing a nose clip.
Support Your Cheeks
You will place your hands on your cheeks to keep them still while gentle sound waves enter your lungs.
Relaxed breathing
Unlike other tests, you do not need to blow out hard or fast; just breathe normally.
Instant Report
The software analyses your report and instantly produces a detailed report.
Understanding your report parameters
| Parameter | What it measures |
|---|---|
| Z (Total Lung Impedance) | The total opposition to airflow, combining both resistance and reactance. |
| R5 (Total Respiratory Resistance) | Resistance measured at 5 Hz, representing the entire respiratory tract (proximal and distal). |
| R20 (Proximal Airway Resistance) | Resistance at 20 Hz, reflecting the state of large, central airways. |
| R5 - R20 | Peripheral Airway Resistance. The difference indicates small airway (distal) dysfunction. |
| X5 (Distal Reactance) | Reflects small airway obstruction, lung elasticity (stiffness), and heterogeneity. |
| AX (Reactance Area) | An integral of the reactance curve; represents the physiological state of distal lung and parenchyma. |
| Fres (Resonant Frequency) | Frequency where inertial and capacitive properties cancel out; indicates obstruction or restriction. |
| X5 Inspi / Expi | Phase-Specific Reactance. Differences can suggest specific patterns like expiratory flow limitation. |
Role of FOT in Asthma and COPD
FOT in Asthma
Particularly valuable for detecting small airway dysfunction and assessing bronchodilator response. It can identify abnormalities during symptom-free periods and help monitor disease control. In children, it provides reliable data even when spirometry cannot be performed.
FOT in COPD
Helps characterize the type and location of obstruction. It detects small airway disease not apparent on spirometry, particularly in early-stage COPD. FOT parameters often correlate better with symptoms and quality of life than FEV1 alone.
How doctors use FOT results?
Detect early airway narrowing that may not show up on spirometry
Assess small airway disease, often missed by routine tests
Differentiate between asthma, COPD, and other lung conditions
Monitor response to inhalers or treatment over time
Evaluate symptoms like breathlessness or cough even when other reports are 'normal'
Frequently asked questions
How does FOT differ from Spirometry?
The primary difference is effort. Spirometry requires forceful blowing; FOT only requires normal tidal breathing.
What does the result indicate?
It maps your respiratory health by measuring Resistance (blockage), Reactance (stiffness), and resonant frequency.
Living in a polluted city?
FOT detects 'silent' inflammation and small airway dysfunction from pollutants like PM2.5 before they cause major damage.
Is it safe for children?
Yes, it is non-invasive and requires no complex maneuvers, making it ideal for children.
How to prepare for a FOT test
The Forced Oscillation Technique (Lung Oscillometry) is a simple, non-invasive breathing test. To ensure accurate results, please follow these simple steps:
Avoid heavy meals
At least 2 hours before the test
Do not smoke
For 4–6 hours prior
Avoid vigorous exercise
For 2 hours before testing
Wear loose clothing
Comfortable, doesn't restrict breathing
Avoid caffeine
Coffee, tea, energy drinks for 2–4 hours
Continue regular medications
Unless your doctor has advised otherwise
Why choose Aelira Lung Care for FOT testing?
Expert Interpretation
Accurate results by lung specialists
Advanced FOT Systems
Latest oscillometry technology
Effortless Testing
Ideal for children & elderly
Same-Day Reports
Quick turnaround with analysis
Get FOT / oscillometry test in Delhi
Aelira Lung Health Centre offers advanced FOT testing at our Green Park, South Delhi location. Our oscillometry equipment provides detailed small airway assessment with comfortable, effort-free testing for all age groups.
Ready to book your FOT test?
Get accurate results with expert interpretation at Aelira Lung Health Centre, Green Park, South Delhi.