Pulmonary Function Tests Flashcards
What are the two main types of respiratory disorders?
Obstructive and Restrictive
What are restrictive disorders?
Extra-airways disorders which restrict the ability of the lungs to entirely fill with oxygen
What are obstructive disorders?
Airways diseases which are associated with obstructed airflow
what is the Forced Vital Capacity (FVC)?
the maximum amount of air which you can forcibly exhale from your lungs after fulling inhaling
what does FVC stand for?
The forced vital capacity
On a flow volume loop, which direction is exhalation?
expiration = going up
On a flow volume loop, which direction is inhalation?
inspiration = Going down
How do you calculate the vital capacity from a flow volume loop?
The difference between the two places the loop crosses the x axis
what is the tidal volume?
The amount of air inhaled and exhaled per breath
What does PEF stand for
Peak Expiratory Flow
what piece of equipment measures peak respiratory flow rate
peak flow meter
What is PEF?
the maximum flow rate - peak of the flow loop
What are 4 reasons which spirometric pulmonary function tests might be undertaken?
- Evaluate symptoms eg breathlessness
- Monitor the progression of a lung disease over time
- Monitor the efficacy of the treatment
- Use it as a screening tool in the absence of sympoms
Describe how a flow volume loop would look for a patient with Mild Obstructive disease?
Reduced FVC, Coving of the exhalation curve
What are the major disadvantages of the spirometric pulmonary function tests?
Heavy reliance on technique and can be rather uncomfortable for patients which reduces their motivation to apply maximum effort
What does a flow volume loop look like for a patient with severe obstructive disease? - 3
Reduced FVC
Indented exhalation Curve
Reduced Peak Expiratory Flow
What does a flow volume loop like for patients with a restrictive disease? - 2
Reduced FVC
Narrow Curve
What does the Flow Volume Curve loop like for someone with a variable extrathoracic obstruction?
Blunted inspiratory curve
Otherwise normal
What does the Flow Volume Curve loop like for someone with a variable intrathoracic obstruction?
Blunted Expiratory Curve
Otherwise normal
What does the Flow Volume Curve loop like for someone with a fixed airway obstruction?
Blunted inspiratory cure
Blunted expiratory curve
Otherwise normal
How do work out the PEF from a flow volume loop
Highest observed y value
How to calculate the FEV1 from a spirometer pulmonary test?
Read the Y value from X=1 second
How to calculate the Peak Expiratory Flow Rate on spirometer graph?
Read up from x=0.2 seconds and multiply by 300 for L/minute
What does a spirometer curve look like in a obstructive disease?
Low Peak Expiratory Flow and FVC/FEV1 ration, and small FVC
Why does an obstructive condition result in a shall spirometer curve?
Severe airflow limitation caused by narrowing of the medium and small airways
Respiratory muscle weakness and increased lung compliance may contribute to the reduced ability of the lungs to generate the pressure required to clear the lungs quickly
Why might there be a wavy airflow pattern after a certain period of time despite having normal airflow?
Patients may be unable to hold the expiration further - manifestation of the Hering-Breuer reflex where afferent signals from the airways lead to simulation of inspiration and cessation of expiratory muscle force
What are some causes of extra-pulmonary restrictive diseases?
Obesity, Pneumoconiosis, Pulmonary fibrosis and severe burns
in Spirometry-Volume time curves, what is on the X axis
time (seconds)
in Spirometry-Volume time curves, what is on the Y axis
Volume (Litres)
what is FEV1
forced expiratory volume in 1 second
how to calculate FEV1 to FVC ratio
FEV1/FVC
what limitation, expiratory or inspiratory does intrathoracic obstruction cause
creates expiratory limitation
what limitation, expiratory or inspiratory does extrathoracic obstruction cause
creates inspiratory limitation
what is a variable obstruction?
obstruction that responds to pressure changes, eliciting varying degrees of obstruction during the respiratory cycle
