Lung Functional Test Flashcards
What is the purpose of Lung Function Tests (LFT)?
Provide information on:
* How much air can be moved
* How fast can the air be moved
* The diffusion capacity of the alveolar-capillary membrane
* Response to treatment e.g. bronchodilator responsiveness
What factors influence normal values in Lung Function Tests?
Factors include:
* Height
* Age
* Gender
* Ethnicity
What is the Peak Expiratory Flow Rate (PEFR)?
Highest flow that can be generated during a forced expiration from full inspiration.
Normal: 300-600 l/min
What is the normal range for Vital Capacity (VC)?
Normal: 3-6 litres (± 80% of TLC)
What is Forced Vital Capacity (FVC)?
Volume of gas expelled after full inspiration, similar to VC but forced.
Normal: equal to VC
What does Forced Expiratory Volume in one second (FEV1) measure?
Volume of gas expelled in the first second of a forced exhalation.
Normal: 80% of VC; 2-4 litres
What is the normal FEV1/FVC ratio?
Normal: 70-80%
What is Total Lung Capacity (TLC)?
Total volume of gas in the lungs after maximal inspiration.
Normal: 3-8 litres
What is Functional Residual Capacity (FRC)?
Volume of gas remaining in the lungs at the end of tidal expiration.
Normal in standing: ± 40% of TLC; 2.4 litres
What is Tidal Volume (TV)?
Volume of air inhaled and exhaled during one cycle.
Normal: 300-800 ml (5-7 ml/kg ideal body weight)
What is Inspiratory Reserve Volume (IRV)?
Amount of additional air that can be inspired above normal tidal inspiration.
Normal: 3.1 litres
What does Expiratory Reserve Volume (ERV) represent?
Additional amount that can be exhaled after tidal expiration.
Normal: 1.2 litres
What is Residual Volume (RV)?
Volume of remaining air in the lungs after maximal expiration.
Normal: 20-30% TLC
What is Minute Ventilation/Volume?
Volume of gas breathed in and out per minute.
Normal: 5-7 l/min
What are the three methods for measuring Total Lung Capacity (TLC)?
Methods include:
* Total body plethysmography
* Gas dilution
* Nitrogen washout
What is the significance of spirometry in lung function testing?
Measures FEV1 and FVC from a maximal forced expiration after a maximal inspiration.
What defines an acceptable effort in spirometry?
Criteria include:
* Lack of artefact (no cough, glottic closure)
* No hesitation at start of test
* Adequate exhalation
* Reproducibility of largest FVC and FEV1
What indicates an obstructive pattern in spirometry?
Reduced FEV1 in relation to a normal FVC.
FEV1/FVC < 75%
What indicates a restrictive pattern in spirometry?
Reduced VC and TLC, possibly caused by:
* Increased lung stiffness
* Pleural disease
* Decreased mobility of thoracic cage
* Impaired muscle function
What does a Flow-Volume Loop measure?
Plots Flow vs Volume to measure resistance from smaller airways.
What is meant by effort-dependent and effort-independent flow in a Flow-Volume Loop?
During inspiration and initial expiration, flow is effort-dependent; latter expiration is effort-independent.
What does the Peak Flow measure?
Measures the amount of air forcibly expelled after a full inspiration.
What is the normal spirometry result for FEV1/FVC?
FEV1/FVC > 75%
Fill in the blank: The normal range for FVC is _______.
3-6 litres
