Blood supply, Gas exchange and lung pathologies affecting diffusion Flashcards
What does the bronchial circulation supply ?
Supplies oxygenated blood via bronchial arteries arising from systemic circulation to lung tissues
What % does bronchial circulation comprise of left heart output ?
2%
What vessel drains blood to left atrium ?
Pulmonary vein
What does the pulmonary circulation consist of ?
L and R pulmonary arteries
Where do the left and right pulmonary arteries arise from ?
Right ventricle
What does the left and right pulmonary arteries carry ?
Entire cardiac output from RV
What does the pulmonary artery supply ?
Dense capillary network surrounding the alveoli
Where does the blood return to after supplying the capillary network surrounding alveoli ?
Oxygenated blood is returned to left atrium via pulmonary vein
How is the pulmonary circulation described ?
High flow, low pressure system
25/10mmHg
What is the partial pressure of O2 in alveoli ?
100mmHg (13.3kPa)
What is the partial pressure of CO2 in alveoli ?
40mmHg (5.3kPa)
What do partial pressures in the systemic venous blood reflect ?
What’s happening in our peripheral tissues
What do partial pressures in systemic arterial blood reflect ?
What’s happening in our alveoli
What does A stand for ?
Alveolar
What does a stand for ?
Arterial blood
What does ṽ stand for ?
Mixed venous blood (e.g. pulmonary artery)
What are the values of PAO2 and PACO2 ?
Alveolar PO2- 100mmHg (13.3kPa)
Alveolar PCO2- 40mmHg (5.3kPa)
What are the values of PaO2 and PaCO2 ?
Arterial PO2- 100mmHg (13.3kPa)
Arterial PCO2- 40mmHg (5.3kPa)
What are the values of PṽO2 and PṽCO2 ?
Venous PO2- 40mmHg (5.3kPa)
Venous CO2- 46mmHg (6.2kPa)
How does the air diffuse across the membranes between the alveoli and the blood circulation ?
Diffusion across the partial pressure gradient
What is the rate of diffusion across the membrane directly proportional to ?
The gas partial pressure gradient
Gas solubility
The available surface area
What is the rate of diffusion across the membrane inversely proportional to ?
The thickness of the membrane
When is the rate of diffusion across the membrane most rapid ?
Over small distances
What does gas need to be in, in order to be able to diffuse across the alveolar membrane ?
Gas needs to be in solution
What are the solubilities of O2 and CO2 ?
O2- not very soluble
CO2- very soluble so van diffuse much faster
What gas (CO2 or O2) has the greatest pressure gradient ?
O2
Describe the overall rates of equilibrium of CO2 and O2 ?
Similar because of the greater pressure gradient for O2
How has the anatomy of the lung adapted to maximise gas exchange ?
Large surface area
Minimum diffusion distance
Thin cell membranes (type I alveolar cells, capillary)
What happens to the surface area of alveoli in emphysema ?
Reduced surface area
What are the features of fibrotic lung disease ?
Thickened alveolar membranes slows gas exchange
Loss of lung compliance (decrease) may decrease alveolar ventilation, increase in effort of inspiration
Decrease in PO2
increase in PCO2
What are the features of pulmonary oedema ?
Fluid in interstitial space increases diffusion distance
Arterial pCO2 may remain normal due to higher solubility in water
Impact on PO2 in blood
What are features of Asthma ?
Increased airway resistance decreases airway ventilation because bronchioles are constricted
What are the features of emphysema ?
loss of surface area Major impact on diffusion Increase in compliance, increase in effort of expiration Decrease in PO2 Increase in PCO2
