Pulmonary blood flow, gas exchange and transport 1-3 Flashcards
(25 cards)
What are the 2 blood supplies to the lungs?
Bronchial circulation (nutritive) and pulmonary circulation (gas exchange)
What is bronchial circulation to the lungs?
Supplied via the bronchial arteries arising from systemic circulation from left side of heart to supply oxygenated blood to lungs
What is pulmonary circulation (gas exchange)?
Carries deoxygenated blood from the RV of the heart to the lungs then returns oxygenated blood to LA of heart
What system is pulmonary circulation?
High flow, low pressure
What is the relationship between ventilation and perfusion?
Ventilation (air getting to alveoli L/min) should be ideally the same as perfusion (local blood flow L/min)
What is the distribution of blood flow in the lungs influenced by?
Hydrostatic (blood) pressure and alveolar pressure
Where in the lungs is there an imbalance in the ventilation-perfusion ratio?
Base and apex
Ventilation-perfusion ratio at the base of the lung
Blood flow is high because arterial pressure exceeds alveolar pressure so perfusion>ventilation
Ventilation-perfusion ratio at the apex of the lung
Blood flow is low because arterial pressure is less than alveolar pressure so perfusion
Where does the majority of ventilation perfusion mismatch occur in the lungs?
Apex
What is autoregulation in V/Q mismatch?
Occurs when ventilation
What is shunt?
Blood that flows through a poorly ventilated region without being oxygenated (perfused but not ventilated)
Local control mechanism for shunt
Tissue around under-ventilated alveoli constrict their arterioles, diverting blood to better ventilated alveoli
What is autoregulation known as when ventilation>blood flow?
Alveolar dead space (oxygen gets into alveoli but not enough blood flow for gas exchange)
What is the rate of diffusion DIRECTLY proportional to?
Partial pressure gradient
Gas solubility
Available surface area
What is the rate of diffusion INVERSELY proportional to?
Thickness of the membrane
Why are the diffusion rates of O2 and CO2 so similar even though the partial pressure gradient of O2 is much bigger?
CO2 is more soluble in water so diffuses faster
What is physiological dead space?
Alveolar + anatomical dead space
How many ml of O2 per litre of plasma?
3ml
What does haemoglobin increase the O2 carrying capacity of whole blood to?
200ml
What is the O2 demand of resting tissues?
250ml/min
What percentage of arterial O2 is extracted by peripheral tissues?
25% at rest
How can a reduced PO2 affect saturation of RBCs?
Halve RBC saturation
What is the arterial partial pressure of O2?
It refers to the O2 in solution and is determined by O2 solubility and the partial pressure of O2 in the gaseous phase that is driving O2 into solution
