Physiology: Surfactant, Compliance and Lung function tests Flashcards
What is surfactant?
detergent like fluid which reduces surface tension
What is surface tension?
attraction of water molecules which is seen in a air - water interface
What cells produce surfactant
Type II alveolar cells
What does surfactant do in the lungs? (5)
Reduces tendency for alveoli to collapse
Increases lung compliance
Reduces lungs tendency to recoil
Makes breathing work easier
More effective in smaller alveoli as the surfactant molecules are close together
When does surfactant production start and finish in embryos?
~25 week it starts and finishes ~36 week mark
What is the production of surfactant stimulated by in embryos?
Thyroid hormones and cortisol
What respiratory problem do some premature babies suffer from?
Infant Respiratory Distress Syndrome (IRDS)
What fills the alveoli in utero?
Saline
What is the definition of compliance?
how much of a volume change for any give change in pressure
Ie how stretchable the lungs are
What does a high compliance in the lungs mean?
large increase in lung volume for a small decrease in ip pressure
What does low compliance mean?
Small increase in lung volume for a large decrease in ip pressure
What is emphysema and what respiratory effort is required?
Loss of elastic tissue
Expiration requires a lot of effort
What is Fibrosis and what respiratory effort is required?
Inert fibrous tissue
Inspiration requires an increase in effort
What is the difference in pressure volume relationship at different areas of the lungs?
at the base the volume change is greater for any given change in pressure when compared to the apex of the lung
Where is alveolar ventilation greatest when compared in the lungs?
Greatest at the base when compared to the apex
Where is compliance higher in the lung?
Compliance is higher at the base when compared to the apex of the lung
Which alveoli are smaller in the lung and why?
Alveoli are smaller at the base of the lung due to the weight of the compressing on the alveoli
What is an obstructive lung disease?
Obstruction of air flow in the lungs
What is a restrictive lung disease?
Restriction in lung expansion
What are examples of Obstructive Lung Diseases?
Asthma
COPD
What are examples of Restrictive Lung Diseases?
Fibrosis
Infant Respiratory Distress Syndrome
Pulmonary Oedema
Pneumothorax
What is a test to measure lung function?
Spirometry
What can be the measurements be classified in in spirometry?
Static - only volume exhaled is considered
Dynamic - time taken to exhale a certain volume
What is FEV1/FVC?
FEV1 - forced expiratory volume in 1sec
FVC - Forced vital capacity
What should a normal FEV1/ FVC measure?
80%
What should someone with a obstuctive lung disease FEV1/ FVC measure and why?
Rate of air exhaled is slower
FEV1 is greatly decreased
FVC is slighlty decreased
The ratio is majorly decrease ie 40%
What should someone with a Restrictive lung disease FEV1/ FVC measure and why?
Airflow rate is reduced greatly
Total volume is reduced greatly
Ratio either stays the same of increases
What is the FEF25-75?
average of the expired flow in the middle of FVC
Normal range is greater the FEV1/FVC
