Pulmonary Function Tests Flashcards
What is FEV1?
- Forced expiratory volume in 1 second
- maximum volume of air that can be forcefully expire within 1 seconds after maximal inspiration
What is FVC?
- Forced vital capacity
- total amount of air exhaled after maximal inspiration during entire FEV test (over 6 seconds)
What is the FEV1 : FVC?
Represents proportion of patient’s FVC that they are able to expire in the first second of forced expiration
What does a FEV1 : FVC ratio of <70% tell us?
Obstructive condition
What is tidal volume?
Volume of air moving in and out of our lungs at rest
What is inspiratory reserve volume?
Additional amount of air that can be inhaled after normal inspiration
(how much more air can be breathed in above TV)
What is expiratory residual volume?
Additional amount of air that can be exhaled after normal expiration
(how much more air we can breath out beyond TV)
What is residual volume?
Amount of air left in the lungs after maximal forced expiration
What are the 4 lung volumes?
Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Residual volume
What are the 4 lung capacities?
Total lung capacity
Vital capacity
Inspiratory capacity
Functional residual capacity
What is inspiratory capacity?
Equation
Total volume of air can be inspired
tidal volume + inspiratory reserve volume
What is functional residual capacity?
Equation
Volume of air remaining after passive expiration
expiratory reserve volume + residual volume
What is vital capacity?
Equation
Volume of air exhaled after maximum inspiration
inspiratory reserve volume + total volume + expiration reserve volume
What is total lung capacity?
Equation
Volume of air in lungs after maximum inspiration
IRV + TV + ERV + RV
What are pulmonary function tests used for?
- To measure lung volumes, rate of airflow + gas exchange
- diagnose patients with respiratory symptoms
- establish severity + progression of lung disease
- assess treatment response
- monitor patients on meds with lung toxicity
Types of pulmonary function tests
- Peak flow rate meter
- Spirometry
- (Diffusing capacity for carbon monoxide)
- (Body plethysmography)
What are the contraindications of Spirometry?
- eye surgery: due to ^ pressure in eye during procedure
- thoracic, abdominal, brain, ENT or vascular surgery
- lung disease: haemoptysis, pneumothorax, PE
- ear infection
- CVS disease - angina, MI, serve HTN
- aneurysms
- acute nausea, vomiting or diarrhoea
- infections control issue: TB, cold, flu
- confused patients
What is peak flow test useful for?
Monitoring people with asthma
What is peak expiratory flow?
Maximum airflow rate attained during forced expiration
What is a normal peak expiratory flow value?
What is used to measure it?
- > 80% of predicted average value based on height, gender + age
- peak flow rate meter
What are the two graphs used in Spirometry?
Volume time plot
Flow volume loop
What is the total lung capacity + residual volume on a flow volume loop?
- total lung capacity: volume of air present in lungs at transition from maximum inspiration to expiration LEFT
- residual volume: volume air present in lungs at the transition between expiration to inspiration RIGHT
How can you use Spirometry to differentiate between asthma and COPD?
- Both obstructive lung disease: FEV1/FVC <70%
- asthma is reversible but COPD is irreversible
- give patient a bronchodilator
- if asthmatic, FEV1 should improve by >12%
- if COPD, no improvement / <12%
How is obstructive lung disease characterised on Spirometry?
- reduced FEV1
- FEV1:FVC ratio <0.7
- initial part of curve on volume-time plot rises less steeply
- coving/scalloping on flow volume loop in expiration
How is restrictive lung disease characterised on Spirometry?
- normal or reduced FEV1
- reduced proportionately FVC
- FEV1:FVC ratio normal >0.7
- reduced TLC on flow-volume graph + shrunk in size (smaller volumes)
What is diffusing capacity carbon monoxide part of?
Peak flow tests
What does peak flow meter measure?
Maximum airflow rate after maximal inspiration
What do diffusing capacity carbon monoxide test do?
- Determines how much O2 travels from alveoli to bloodstream by measuring CO diffusion
- Provides info on alveolar-capillary membrane
What does an abnormal DLCO with normal chest x ray + spirometry suggest?
Problem with vascular part of membrane
e.g. idiopathic pulmonary arterial hypertension, choleric thrombo-embolic disease of lung
What would investigations of idiopathic pulmonary arterial hypertension show?
Normal spirometry
Normal CXR
Abnormal DLCO
How do you calculate the peak expiratory flow rate using Spirometry?
Maximum slope of curve gradient
How can you work out the FVC on a flow-volume graph?
RV - TLC
(Between the 2 x intercepts)
Flow volume loops in chronic obstructive disease
coving/scalloping
Flow volume loop in restrictive lung disease
Shrunken
Wizard’s hat
When is the baseline for peak flow determined?
When patient is asymptomatic
What factors are use to work out predicated peak flow values?
Height
Gender at birth
Age
(Ethnicity)
How long can it take for a patient with severe COPD to force all the air out of their lungs in Spirometry?
15 seconds
What units is flow measured in?
L/sec
What pattern is seen on flow volume loop in a restrictive lung disease?
Wizard’s hat
Shrunken/reduced volume
