Ventilation and compliance 2 Flashcards
What is the purpose of surfactant in type 2 cells
reduces surface tension on alveoli wall
How is surface tension created on the alveoli
the air water interface, causing a water interaction to apply pressure on to the alveoli
BASICALLY
the net movement of water means the water surrounding the alveoli will push into the middle
How is surfactant more effective in smaller alveoli
is more concentrated
How does the surfactant overcome the surface tension
contains the surface area and decreases the pressure
What would happen if surfactant wasn’t present in alveoli
As the pressure is higher in the smaller alveoli they would push out all the air and collapse, which would then move into the larger alveoli increasing its surface area SUPER ALVEOLI - decreasing overall surface area though
What are the benefits of surfactant
reduces lungs tendency to recoil
prevents collapsing of alveoli
increase lungs compliance
makes it easier to breathe
What respiratory disease is associated with premature babies
Respiratory distress syndrome
making it harder for them to breathe as haven’t produced surfactant
When does surfactant production start and end
start - 24 weeks gestation
complete - 36 weeks gestation
What does babies breath in the utero and why is this easier than air?
They breathe in saline which requires less pressure than breathing in air due to not needing to overcome the surface tension created by an air water interface
What is compliance?
The stretchability of the lungs
Define high compliance
Large increase in lung volume for small decrease in pressure
Define low compliance
Small increase in lung volume for large decrease in pressure
What two factors alter compliance
age
disease
What respiraratory disorder has a high compliance but struggles with expiration
EMPHYSEMA
How does emphysema occur
expiration is passive, recovered by elastic coil, if you loose the elasticity, the expiration needs to be actively push the air out.
What else can cause emphysema
destruction of alveoli
What causes Fibrosis
Excess Fibrous connective tissue causes the compliance to decrease, resulting in a more difficult inspiration
What are the two different classifications of lung diseases
Obstructive - increased airway resistance
Restrictive - loss of lung compliance
What does obstructive lung diseases affect mostly
expiration
What are examples of obstructive lung diseases
asthma
emphysema
chronic bronchitis
what causes chronic bronchitis
inflammation of the bronchi
In restrictive lung disease what does loss of compliance cause
lung stiffness
incomplete lung expansion
Name four restrictive lung diseases
oedema
fibrosis
infant respiratory syndrome
pneumothorax
What is the name of the test to measure lung function
spirometry
What are the two spirometry test
static - volume exhaled
dynamic - time taken to exhale a certain value
What type of respiratory volumes can spirometry measure
Measure anything that doesn’t include the residual volume
What is the ratio FEV1/FVC a measure of
The measure of the percentage of air expired in a second compared to how much can be expired over all
What is a normal FEV1/FVC value
80%
Whys is spirometry not a good indicator on the health of your ventilation
In restrictive disorders the total volume expired but the lung is reduced but the ratio remains constant therefore the test allure that you are healthy
In an obstructive disorder what affect does this have on the FEV1/FVC ratio
Rate at which air is exhaled is much slower so the FEV is reduced altering the FEV/FVC ratio
What is the Forced expiratory flow
average expired flow in the middle of an FVC
Why does the Alveolar ventiation declines with height from base to apex
greater volume change at the bottom of the lungs as the alveoil go from not inflated to fully flatted compared to the apex which is already partially flatted
