Lecture 6.2: Lung Function Testing Flashcards
What is included in the Lung Function Report? (9)
• Vital Capacity
• FEV1 (before and after bronchodilators)
• FEV1/FVC ratio
• Peak Expiratory Flow Rate
• FRC
• RV
• TLC
• RV/TLC
• Transfer factor (carbon monoxide conductance)
Why is Lung Function Testing done?
• The mechanical condition of the lungs
• Resistance of the airways
• Diffusion across alveolar membrane
Volume: What is Vital Capacity?
Maximum Inspiration to Maximum Expiration
What limits Vital Capacity? (2)
Maximum Inspiration:
• Compliance of the lungs
• Force of inspiratory muscles (diaphragm, intercostal muscle)
Maximum Expiration:
• Increasing airway resistance
• As the lungs are compressed
What is Single Breath Spirometry?
Subject fills lungs from atmosphere and then once connected to mouthpiece
breathes out as far and fast as possible
What are the long forms of FEV(1) and FVC?
• FEV1 = Forced Expiratory Volume in 1 Second
• FVC = Forced Vital Capacity
What is Forced Vital Capacity (FVC)? Typical Value? Determining Factors?
• The maximum volume that can be expired from full lungs
• Typically 5l in healthy adult
• Dependent on age, height and sex
What is Forced Expiratory Volume in 1 Second (FEV1)? Typical Value? What can impact this value?
• Measures how easy it is to get air out
• A good indicator of the state of your airways
• Reduced if airways are narrowed
• Normally >70% FVC (typical values 66-83%
What is the FEV1/FVC ratio? Typical Value?
• Is the ratio of the forced expiratory volume in the 1st second to the forced vital
capacity of the lungs
• The normal value for this ratio is above 0.75-85, though this is age dependent
What do FEV1/FVC ratio values of less than 0.70 indicate?
Values less than 0.70 are suggestive of airflow limitation with an obstructive pattern
What is a Restrictive Deficit? What happens to FEV1 and FVC?
• Lungs are difficult to fill
• They are stiff
• Weak muscles
• Problem with chest wall
• They will start less full (reduced FVC)
• But air will come out normally (normal FEV1)
• FEV1/FVC ratio is normal (or higher) – i.e. ≥ 0.7
What is an Obstructive Deficit? What happens to FEV1 and FVC?
• Airways narrowed causing increased resistance in expiration
• Slower air flow (Reduced FEV1)
• No limitation to filling (FVC relatively normal)
• FEV1/FVC ratio is <0.7
What is Peak Expiratory Flow Rate (PEFR)?
Peak flow measurement is a quick test to measure air flowing out of the lungs
What is a Peak Flow Meter? What is it used for? Problems?
• Simple, cheap device
• Screening test for airway narrowing
• Insensitive
• Screening for asthma
• Monitoring asthma at home
Measurement of Serial Dead Space: Nitrogen Washout
• Subject takes one normal breath of pure oxygen
• Breathes out via meter measuring % nitrogen
• Initially only oxygen expired from airways
• Then mixture of oxygen and air (inc Nitrogen) from alveoli
• Volume expired at transition is serial dead space
• Also used to measure (indirectly) ventilation perfusion matching