Session 6: Spirometry and Lung Function Measurements Flashcards
What is spirometry?
Measuring of breath. It records the volume of air that is breathed in and out and generates tracings of air flow.
What are the tracings generated by the spirometer used for?
To calculate vital capacity, tidal volume and the flow rate of air movement.
Also forced expiration volume.
Why would you use a spirometer?
Diagnosis, however the tests are rarely diagnostic on their own.
Patient assessment
Research purposes
What should be higher, FVC when seated or standing?
FVC standing > FVC seated
What will forced flow-volume measurements show us?
How much air can the subject blow out?
How fast is the air expelled?
Pattern of change in flow-volume curve
Response to treatment
Change with age and growth
Progression of a disease
What is FVC?
Forced vital capacity
The maximal amount of air that the patient can forcibly exhale after taking a maximal inhalation.
Only thing left is the residual volume
What is FEV1?
Forced expiration volume
Volume exhaled in the first second of forced exhalation.
What is peak expiratory flow?
Maximal speed of airflow as the patient exhales
Explain what a time volume graph is.
When volume exhaled is matched against time.
What is the FEV1:FVC ratio?
A ratio of how much air is exhaled in the first second of forced exhalation (FEV1) compared to how much can possible be exhaled (FVC).
What is a normal FEV1:FVC ratio?
When FEV1 is above 70% of FVC.
How does the FEV1:FVC ratio help?
It can determine what type of lung disease a patient might have.
If FEV1 <70% of FVC. What is this in indication of?
Obstructive defect.
What is the FEV1:FVC ratio in restrictive disease?
Normal
How can the FEV1:FVC ratio be normal in restrictive lung disease?
Because both FEV1 and FVC are reduced proportionately.
Typical conditions where an obstructive pattern can be seen.
COPD
Asthma
Typical conditions where a restrictive pattern can be seen.
Diffuse lung fibrosis
In normal individual, what is the peak flow mostly affected by?
Resistance of the large airways
In individuals with severe obstruction of the smaller airways like in asthma. What will be affected?
The peak expiratory flow rate.
Explain the flow volume curve in mild obstructive disease.
The curve gets scooped out
Explain the flow volume curve in severe obstruction.
The curve is scooped out but the PEFR is also reduced.
Explain the flow volume loop in restrictive lung disease.
It is characterised by a decrease in FVC.
This leads to a narrow flow volume loop where PEFR is not significantly reduced because there is no obstruction.
This leads to a narrow and tall flow loop.
In order to determine whether an obstructive condition is due to asthma or COPD, how can the spirometry test be conducted further?
By giving B2 agonists like salbutamol.
How would B2 agonists differ in the spirometer test between asthma and COPD?
There will be a significant improvement of FEV1:FVC in asthma as well of the flow volume loop.
No significant change in COPD.
Why is spirometry tests done sitting down even though FVCstanding>FVCsitting?
Because high intrathoracic presure can lead to reduced CO and cerebral outflow.
This can lead to fainting.
What does this indicate?
Variable upper airway obstruction of airways like a laryngeal polyp.
What does this indicate?
Fixed upper airway obstruction like tracheal stenosis
Movement of trace in inspiration.
Upward deflection
Movement of trace in expiration.
Downwards deflection
How to measure residual volume.
Diane hudman says this can’t be measured.
Work book says:
Helium dilution test
How to measure dead space.
Nitrogen washout method
How to measure diffusion capacity.
Carbon monoxide transfer factor
What is a normogram?
A diagram to standardise FVC and predict it.
The measured value is compared to that of healthy people of the same gender, age and height.
What is the right diagram an indication of?
Asthma
