Lung Function Tests and Common Lung Conditions Flashcards
What is an obstructive lung disease?
Obstruction of air flow especially on expiration
What is a restrictive lung disease?
Restriction of lung expansion
What two diseases come under Chronic Obstructive Pulmonary Disorder?
Chronic bronchitis and emphysema.
What is chronic bronchitis?
Inflammation of the bronchi
What 3 condtions come under obstrcutive lung disorders?
Asthma, Chronic bronchitis and emphysema
Do obstrcutive lung disorders affect inspiration or expiration?
Expiration
What does idiopathic mean?
The cause of the disease is uknown.
What are the four restrcitive lung disorders?
Fibrosis, Infant Respiratory distress syndrome, oedema and pneumothorax.
What is spirometry?
It is a technique commonly used to measure lung function.
How can the measuremnts of spirometry be classed?
Static or dynamic
What does a static test mean in spirometry?
The only volume measred is the volume exhaled or inhaled.
What does a dynamic test mean in spirometry mean?
The time taken to exhale a certain volume.
What can spirometry measure?
Inspiratory reserve volume, expiratory reserve volume, tidal volume, inspiratory capacity, vital capacity (anything that doesn’t have the residual volume included.)
What is the forced expiratory volume in 1 second?
It is taking a deep breath and seeing what volume of air you can push out in 1 second.
What is the forced vital capacity?
It is how much you can breath out over however long it takes.
What is the normal FEV1:FVC ratio/percentage?
80%
How does an obstructive disease affect spirometry?
Rate at which air is exhaled is slower, total expired volume (FVC) is also reduced, major effect is on airways and so FEV1 is reduced to a greater extent than FVC and so the ratio is reduced.
How does a restrictive disease affect spirometry?
It decreases the FEV1 but this is only because there isn’t much air in the lungs anyway, but FVC is reduced because there isn’t much air in the lungs anyway. However they are both reduced but within proportion and so the ration is close to normal and even higher than normal. Absolute rate of airflow is reduced.
How does compliance vary with inspiration?
Compliance is very low at the start of inspiration and then it increases greatly at the end of inspiration. For large chnages in intrapleural pressure at the start of inpiration we have a small chnage in volume. For small changes intrapleural pressure at the end of inspiration there is a large chnage in volume.
How does compliance vary with expiration?
Compliance is low at the start of expiration, compliance increases towards the end of xpiration.
Quick note
Inspiratory and expiratory curves are not superimosed onto each other, it requires a greater change in pressure to reach a particular lung volume during inspiration, than to maintain that volume during expiration.
Why does inspiration require a greater change in pressure?
- Overcome lung inertia during inspiration
* Overcome surface tension during inspiration
What is transpulmonary pressure?
The relationship between alveolar pressure and the intrapleural pressure (always positive).
What is the average FEV1 for a healthy male?
4 litres
What is the forced vital capacity for a healthy male?
5 litres
What are the FEV and FVC for an obstructive respiratory disorder?
FEV decreases (significantly) FVC is also reduced FRC may be increased Ratio is reduced
What are the FEV and FVC for an restrictive respiratory disorder?
Absolute rate of airflow is reduced (FEV redcued) Total volume is reduced due to limitations to lung expansion (FVC) Ratio remains constant or can increase as a large proportion of volume can be exhaled in the first second.
