Blood Supply, Gas Exchange, Ventilation and Perfusion Flashcards
(40 cards)
What are the partial pressures of deoxygenated blood?
PO2: 40mmHg
PCO2: 46mmHg
Rate of diffusion is directly proportional to what?
Partial pressure gradient
Gas solubility
Surface area
Rate of diffusion is inversely proportional to what?
Membrane thickness
Why is the rate of CO2 diffusion so high despite the low pressure gdt?
CO2 much more soluble in water than O2
How does pulmonary oedema decrease the rate of diffusion?
Increased diffusion distance due to fluid in the interstitial space
What is ventilation?
Air getting to alveoli
What is perfusion?
Local blood flow
Where is the lung is blood flow best? Why?
The base
Because arterial pressure exceeds alveolar pressure
Roughly where in the lung does blood flow equal perfusion?
Rib 3
What are the local control measures to avoid shunt?
Bronchoconstriction to poorly perfused alveoli
Vasoconstriction to poorly ventilated alveoli
What is alveolar dead space?
Alveoli that are ventilated but not perfused
What is shunt?
Passage of blood through areas of the the lung that are poorly ventilated
What is Physiological Dead Space?
Alveolar and Anatomical dead space
Where is CO2 carried in the blood?
Solution in plasma
PaO2 is not the same as what?
Arterial O2 concentration
How much arterial O2 is extracted by peripheral tissues at rest?
25%
How much O2 in the blood is bound to Hb?
98%
How long is blood in contact with the alveoli?
0.75s
Why do fetal Hb (HbF) and myoglobin have a higher affinity for O2 than HbA?
To extract O2 from maternal blood?
What is anaemia?
Condition where the O2 carrying capacity of blood is compromised
What affect does decreasing blood pH have on affinity?
(acidosis)
Reduced affinity
What effect does increased temperature have on affinity?
Reduced affinity
What effect does increased PCO2 have on affinity?
Reduced affinity
What effect does having no 2, 3DPG have on affinity?
Huge increase in affinity
