Lung Volumes and Lung Function Testing Flashcards
What is tested in lung function testing
Mechanical condition of the lungs
Resistance of the airways
Diffusion across the alveolar membrane
How does a spirometer work and what does it measure (vaguely)
Breath in and out of the drum which raises and lowers as the water is displaced; a pen then tracks out the breathing pattern
It measures lung volume
What are all the initials
TLC: Total Lung Capacity VC: Vital Capacity TV: Tidal Volume FRC: Forced Residual Capacity IRV/ERV: Inspiratory/Expiratory Reserve Volume RV: Residual Volume
Tidal Volume
Volume of air entering and leaving the lung with each normal breath (approx 0.5l)
Vital Capacity Volume
Volume of air expired out after a deep breath in and a deep breath out
(TV+IRV+ERV)
Inspiratory Reserve Volume
Extra volume of air inspired above the normal tidal volume with full force
Expiratory Reserve Volume (ERV)
Extra volume of air expired by forceful expiration at the end of normal tidal expiration
Resitdual Volume
Volume of air remaining in lungs after the most forceful expiration
Functional Residual Capacity
Amount of air left in lungs after normal expiration (Expiratory reserve volume + Residual Volume)
Total Lung Capacity
Maximum Volume of air the lungs can hold (Vital Capacity + Residual Volume)
Vitalograph
Device used to measure forced vital capacity (FVC) and FEV1 (Volume expired in first second, typically >70% FVC)
Tell patient to inhale very deeply, then exhale as hard and long as possible and use as much effort as possible
Usually take the best result of 3 trials
Helium Dilution System
Known concentration of helium and volume in this system
Compare system before breathing helium vs after
C2 is known because we can measure it
Used to measure FRC and thus TLC/RV since spirometer cannot
YOU ARE NOT EXPECTED TO KNOW FORMULAS
Nitrogen Washout
Calculates the amount of nitrogen in lungs to reverse engineer a way to calculate total lung capacity containing O2
Restrictive Deficits
Pulmonary fibrosis and scoliosis
FVC is reduced but FEV1 is relatively normal
FEV1:FVC remains mostly normal/increased
Think that the airways are fine but lungs are compressed
Obstructive Deficits
Asthma, COPD
FEV1 is reduced but FVC mostly normal
Think that the airways are obstructed but lung capacity is not affected
Analyse vitalograph results
Red is restrictive (2.8–>3.0), orange is obstructive (3.1–>5) and yellow is normal (4.5–>5)
PEF Rate
Peak Expiratory Flow Rate
Curve indicates exhalation (as hard as possible)
Flow Volume Loops
Red is restrictive, orange is obstructive and yellow is normal
Note that for red, the shape is the same because the airways are normal but the proportions are affected
Peak Flow Meter
Diffusion Conductance
