ventilation and compliance 2

Question 1

Surfactant released from type 2 cells in lungs

Answer 1

• Reduces surface tension- makes breathing easier
• Prevents the alveoli from collapsing
• Increases compliance- reduces tendency of the lung of recoiling
• More effective in small alveoli- cells which produce surfactant are together so more concentrated
• Production begins in week 25 of pregnancy and reaches completion during week 36- premature babies have infant respiratory distress syndrome

Question 2

Compliance

Answer 2

Changes in volume of lungs relating to changes in pressure

Describes the stretchability of the lungs not the elasticity

Question 3

High compliance vs Low compliance

Answer 3

High= large increase in volume with small decrease  in pressure
Low= small  increase  In volume with large  decrease in pressure

Question 4

compliance in normal respiration

Answer 4

Normal= change in pressure greater to reach change in volume during inspiration.
Need to overcome:
-Tissue inertia: pressure of tissues when they are started to become inflated
-Surfactant release: initially alveolar surfactant is subepithelial- need to start stretching out alveoli in order to have surfactant release which then makes it easier to achieve a change in pressure
Expiration:
-Changes in volume require a greater pressure towards the beginning of expiration as they have they press against the chest wall making it Harden
-Also need a higher pressure in order to release more surfactant as the alveoli are Compressed

Question 5

Changes in Volume-pressure at base/apex of lungs

Answer 5

Apex= smaller change in volume for given change in pressure
Alveolar ventilation decreases from apex to base
Compliance decreases from apex to base
Alveoli at base are crushed between lungs and diaphragm -less inflated-more compliant
Alveoli at the apex more inflated at FRC.

Question 6

Obstructive diseases

Answer 6

Due to obstruction of air flow
Increases airway resistance
Asthma, COPD

Question 7

Restrictive diseases

Answer 7

Due to restriction of lung expansion
Loss of compliance 
Pulmonary fibrosis
Oedema
Infant respiratory distress syndrome 
Pneumothorax

Question 8

Spirometry

Answer 8

Measures lung function 
Static= volume exhaled
Dynamic=volume exhaled in given period of time 
Can measure TV, IRV, ERV, VC, IC
In normal healthy male 
FEV =4.0 
FVC= 5.0 
FEV/FVC = 80 %
in obstructive disease 
FEV=1.3
FVC=3.1
fev/fvc =45%
In restrictive disease
FEV=2.8
FVC=3.1
FEV/FVC= 90%

Question 9

Explanation for changes in FEV and FVC in obstructive and restrictive respiratory disease?

Answer 9

In obstructive:

• Rate of exhalation is slower
• total volume is reduced
• both FEV1 and FVC decrease but in FEV it falls more so ratio reduced

In restrictive:

• Absolute rate of airflow is reduced
• Total volume decreases
• FEV and FVC both fall- ratio stays the same

Question 10

Does compliance increase/ decrease with:

• pulmonary fibrosis
• emphysema

Answer 10

Fibrosis =greater work during inspiration due to excess fibrosis tissue
Pulmonary Fibrosis: Decreases- less stretchy material

Question 11

compliance in emphysema

Answer 11

Emphysema= greater work during expiration due to loss of elasticity of lungs.
Transpulmonary pressure becomes negative during expiration as the intrapleural pressure is so great due to work.
Compliance increases as there is less fewer elastic fibres so less work to fight against