FOT (Forced Oscillation Technique)
Non-invasive test measuring airway resistance and lung mechanics in real-time
What is FOT?
Forced Oscillation Technique (FOT) is a non-invasive pulmonary function test that measures airway resistance and lung mechanics by applying small oscillations (vibrations) at the mouth during normal breathing. Unlike spirometry, FOT requires minimal patient cooperation and effort, making it ideal for children, elderly, and patients unable to perform forced breathing maneuvers.
FOT provides real-time assessment of airway properties including resistance, reactance, and compliance. It is particularly useful for detecting small airway obstruction and assessing treatment response in obstructive airway diseases.
Why is FOT important? It helps physicians:
- Detect small airway obstruction before spirometry changes
- Assess patients unable to perform spirometry
- Measure bronchodilator or bronchoconstrictor response
- Monitor disease progression and treatment efficacy
- Provide reliable testing for children and uncooperative patients
Key Parameters Measured by FOT
Resistance (R)
Opposition to airflow in the airways. Elevated in obstructive conditions.
Reactance (X)
Elastic and inertive properties of respiratory system. Negative values indicate stiffness.
Resonant Frequency (Fres)
Frequency where reactance equals zero. Elevated in obstructive disease.
Compliance (C)
Lung and chest wall elasticity. Decreased in restrictive disorders.
Clinical Indications for FOT
- Children unable to perform spirometry cooperation
- Elderly patients with limited respiratory effort capacity
- Detection of small airway disease
- Asthma diagnosis and management
- COPD assessment and monitoring
- Evaluation of bronchodilator response
- Patients with neuromuscular disorders
- Pre- and post-operative respiratory assessment
Preparation for FOT
Avoid Bronchodilators
Skip bronchodilators for 4-6 hours before the test if possible.
Light Meal Only
Eat light meal at least 1 hour before test. Avoid heavy meals.
Comfortable Clothing
Wear loose clothing that does not restrict chest or abdominal movement.
Relax Before Test
Allow patient to rest and calm down for 5-10 minutes before testing.
How FOT is Performed
FOT testing typically takes 10-20 minutes:
- Patient sits comfortably with nose clip applied
- Mouthpiece is gently placed in mouth with gentle cheek support
- Small oscillating pressure signal delivered to airways
- Patient continues breathing normally during measurement
- Multiple measurements at different frequencies performed
- Results generated immediately by computer analysis
Advantages: No forceful breathing required, minimal patient effort, suitable for all ages, quick results, and excellent reproducibility.
After FOT Testing
Normal Activities Immediately
No restrictions. Resume normal activities right after the test.
Results Review
Physician will discuss results and interpret in clinical context.
Bronchodilator Response Testing
Optional repeat testing after bronchodilator to assess reversibility.
Treatment Plan
Results help guide treatment decisions and management strategies.
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