Blood supply, gas exchange, ventilation & perfusion Flashcards
What pulmonary blood vessel travels away from the heart? what does it carry?
Pulmonary artery - CO2 to the lungs
What pulmonary blood vessel travels towards the heart? What does it carry
O2 from the lungs to be pumped to the systematic circulation
What circulation delivers oxygenated blood to airway smooth muscle, nerves and lung tissue?
Bronchial circulation (nutritive)
What is the bronchial circulation supplied by?
The bronchial arteries that arise from the systematic circulation
The entire cardiac output from the right ventricle is carried by what circulation
Pulmonary circulation (gas exchange)
What does the pulmonary circulation consist of?
Left and right pulmonary arteries
What does the pulmonary circulation supply/do?
The dense capillary network surrounding the alveoli and returns oxygenated blood to the left atrium via the pulmonary vein
Is the pulmonary circulation a high or low flow and pressure
High flow, low pressure
What gradients drive gas exchange?
Partial pressure gradients
What do these abbreviations stand for: A a ṽ in relation to blood?
A - alveolar
a - arterial blood
ṽ - mixed venous blood
What kind of membrane do gases move across?
Permeable
The rate of diffusion across the membrane is directly proportional to what?
The partial pressure gradient (similar to conc. gradient)
The gas solubility
The available surface area
The rate of diffusion across the membrane is inversely proportional to what?
The thickness of the membrane
When is diffusion most rapid?
Over short distances
What is more soluble in water, carbon dioxide or oxygen?
Carbon Dioxide
What do systolic/diastolic mean?
Systolic - max blood presssure when the heart is contracted
Diastolic - min blood pressure when the heart is relaxed
What are the normal systolic pressures?
Pulmonary systolic pressure = 25mmHg
Systemic systolic pressure = 120mmHg
Whats the diference between the pressure of the pulmonary vein and artery that causes blood to flow? And why is it clinically important?
About 10mmHg as it is small it only takes a little patholgy to disrupt the blood flow. (Systemic is normally 100mmHg)
What happens in emphysema?
The destruction of the alveoli reduces surface area for gas exchange
In Emphysema, what are the values of Alveolar PO2 and Capillary PO2 relative to normal values?
Alveolar PO2 – normal or low Capillary PO2 –low
What happens in fibrotic lung disease?
The alveolar membrane thickens which slows don gas exchange
Also the loss of lung compliance may decrease alveolar ventilation
In Fibrotic Lung Disease, what are the values of Alveolar PO2 and Capillary PO2 relative to normal values?
Alveolar PO2 – normal or low Capillary PO2 – low
What happens in a pulmonary oedema
The fluid in the interstitial space increases which causes the diffusion space to increase in distance
In Pulmonary Oedema, what are the values of Alveolar PO2 and Capillary PO2 relative to normal values?
Alveolar PO2 – normal Capillary PO2 –low
In a pulmonary Oedema, why might arterial PCO2 remain normal?
CO2 has a higher solubility in water
How does asthma affect gas exchange?
Bronchioles constrict which increases airway resistance which decreases airway ventilation
In asthma, what are the values of Alveolar PO2 and Capillary PO2 relative to normal values?
Alveolar PO2 – low
Capillary PO2 –low
What pressures influence the distribution of blood flow in the lungs?
Hydrostatic blood pressure and alveolar pressure
What is blood flow inversely proportional to?
Vascular resistance
At the base of the lungs, blood flow is BLANK because?
High because arterial pressure exceeds alveolar pressure and vascular resistance is therefore low.
At the apex of the lungs, blood flow is BLANK because?
Low because arterial pressure is less than alveolar pressure. This compresses the arterioles and vascular resistance is increased.
When arterial pressure is less than alveolar pressure, blood flow will be
Reduced
There is a mismatch in Ventilation:Perfusion when the ratio is
Greater or lower than 1.0
If ventilation decreases in a group of alveoli, what effect will this have on PCO2 and PO2?
PCO2 - increases
PO2 - decreases
What is “shunt”?
The passage of blood flow through areas of the lung that are poorly ventilated
What effect is there on arterioles when there is decreased tissue PO2 around under-ventilated alveoli?
Arterioles will constrict to divert blood to better ventilated alveoli
Constriction in response to hypoxia is particular to what vessels?
Pulmonary vessels only
The systematic vessels dilate
Alveolar dead space is…
Alveoli that are ventilated but not perfused, opposite to a shunt
What happens to alveolar partial pressures during alveolar dead space?
PA O2 increases
PA CO2 decreases
What does a PA O2 increase lead to in alveolar dead space?
Pulmonary vasodilation
What does a PA CO2 decrease lead to in alveolar dead space?
Bronchial constriction
What is the purpose of these two responses?
To increase perfusion and to a lesser extent decrease ventilation, bringing the ratio back towards 1
Physiological Dead Space is…
The alveolar dead space + anatomical dead space
