Week 9 - Lung Perfusion

Question 1

What is lung emphysema?

Answer 1

• decreases lung stiffness
• creates bigger air pockets in alveoli
• easy to inflate and collapse the lung
• low pressure needed to increase lung volume

Question 2

What is lung fibrosis?

Answer 2

• increases lung tissue thickness
• increases its resistance
• dampens response of lungs
• high pressure needed to increase volume by little

Question 3

What is chronic obstructive pulmonary disorder?

Answer 3

• develops from emphysema
• bronchial tubes collapse after alveolar damage
• air is trapped inside lungs
• cannot deflate fully
• reduces gas exchange

Question 4

What is pulmonary oedema?

Answer 4

• from negative pressure
• barrier distance increased
• from extra fluids entering the alveolus
• and gap between capillary and alveolus widening
• caused from infections
• can cause secondary drowning
• small amount of water enters the lung, which can be unnoticeable

Question 5

Why do lungs not ventilate evenly?

Answer 5

• intrapleural pressure is the pressure in the pleural cavity
• always negative
• less negative at the bottom due to gravity pressure from lungs
• base alveoli are more compressed
• most room to expand
• most ventilation occurs
• perfusion is highest here for efficiency

Question 6

What happens if rates of perfusion and ventilation are unequal?

Answer 6

• ventilation dominates perfusion
• O₂ rises
• arteriolar smooth muscle relaxation
• vessel dilation
• decreased vascular resistance
• to increase blood flow
• CO₂ decreases
• airway smooth muscle contraction
• constriction of airways
• increased airway resistance

Question 7

How does COVID19 cause happy hypoxemia?

Answer 7

• low PaO₂
• but no dyspnea
• due to left shift of oxyhaemoglobin curve
• normal Hb saturation but low PaO₂
• patient is not in distress
• pulmonary shunts are also created
• blood does not pass by alveoli
• anatomic shunt if zero perfusion
• physiologic shunt if reduced perfusion
• causes oedema and loss of surfactant and collapse
• VQ mismatch creates dead space
• COVID19 blocks ACE2 receptor for angiotensin conversion
• increased angiotensin II causes pulmonary vasoconstriction