Respiratory strand: Lecture 8 - Matching Lung Ventilation to Lung Perfusion Flashcards
What is ventilation and what unit is it measured in?
- movement of gases in and out of the lungs
- occurs through airways
- measured in change in volume per unit time e.g L/min
What is perfusion, where does it occur and what unit is it measured in?
- Blood flow through any organ e.g lungs
- Occurs through blood vessels
- measured as flow of blood/unit time
Are apical and basal alveoli the same size? If not, why?
No, apical alveoli are about 4 times larger than basal alveoli in the upright posture
This is due to the effect of gravity
Which regions of the lungs have the best ventilation?
- basal regions of lungs have better ventilation than apical regions
- basal alveoli can expand more than apical alveoli
What is bronchial circulation?
-nutrition to lung tissue
-bronchial artery from thoracic aorta
-bronchial vein to superior vena cava
-2% of cardiac output
image slide 8
How is pulmonary circulation different to systemic circulation?
lungs receive full cardiac output but at a much lower pressure compared to systemic circulation
What is the function of the pulmonary artery?
Carries deoxygenated blood from the right ventricle to the lung
What are extra-alveolar vessels?
- pulmonary artery splits into right and left branches to supply the respective side lung
- each branch then successfully splits into smaller branches closely following airway divisions called extra alveolar vessels
- not part of gas exchange
- running through lung parenchyma
What happens during pulmonary circulation beyond terminal bronchioles?
blood vessels form capillary beds (starting with smaller arterioles) where gas exchange starts
What is meant by a ‘sheet of blood’?
- blood flowing through rich network of capillaries forms a ‘sheet’ of blood with a high surface area
- very efficient gas exchange
What is emphysema?
- widespread destruction and dilation of distal airway
- regional destruction of vascular beds
- poor gas exchange and hypoxia
Where in the pulmonary circulation does gas
exchange start?
Small arterioles
What is hydrostatic pressure?
Force exerted by weight of a fluid (blood/water) due to gravity
How is hydrostatic pressure related to pulmonary circulation?
-column of blood exerting different hydrostatic pressure in different areas of lungs in relation to the position of the right ventricle
What are the 3 lung zones?
Zone 1:
- alveolar dead space
- good ventilation but no perfusion
- no gas exchange
- apices of the lungs
- Palv>Part>Pvein
- poor blood flow
Zone 2:
- recruitment zone: blood flow increases
- lower down than zone 1
- Arterial pressure increases due to higher hydrostatic pressure
- more capillaries
Zone 3:
- distension (swelling) zone: lung bases
- hydrostatic forces raise Parterial and Pvenous above Palveolar
- continuous blood flow
- blood flow determined by difference between alveolar pressure and pulmonary venous pressure
