Pulmonary Blood Flow, Gas Exchange and Transport Flashcards
What two circulation supply the lungs with blood
Bronchial - nutritional
Pulmonary - gas exchange
What does the bronchial circulation supply
supplying oxygenated blood from the aorta to the airway smooth muscle, nerves and lung tissue.
What kind of pressure system is the pulmonary and bronchial circulation
Pulmonary: high flow low pressure system
Bronchial: Low flow high pressure system
What does the pulmonary circulation surround, and what does it supply it with
Surrounds dense capillary network surrounding the alveoli
supplying it with the deoxygenated cardiac output from the right ventricle pulmonary artery and returning oxygenated blood to the left atrium from the pulmonary vein
What gradient do the gas exchange at the alveoli follow
the partial pressure gradient (diffusion)
What is the rate of the gas diffusion at the alveoli proportional to
partial pressure
gas solubility
available surface area
The rate of diffusion is inversely proportional to what at the alveoli
the thickness of the membrane
When is diffusion most rapid
over short distances
In emphysema what causes the oxygen diffusion level to decrease
the surface area is decreased due to destruction of the alveoli
In fibrosis what causes the oxygen diffusion levels to decrease
thickened alveolar membrane
What lung disease increases the diffusion distance
pulmonary oedema
How does asthma decrease airway ventilation
Increases airway resistance
What kind of relationship does ventilation and perfusion have in the alveoli
a complimenting relationship
What is perfusion/ Blood flow directly proportional to
vascular resistance
What is blood flow distribution influenced by
arterial (hydrostatic) pressure and aveolar pressure
Where is the blood flow in the lungs high
The bottom of the lungs then declines with ascending height
What would cause blood flow to be high
when arterial pressure exceeds alveolar pressure therefore decreasing vascular resistance
Why does the ratio of the ventilation to perfusion decrease from the bottom of the lungs to the apex
as the pulmonary artery pressure is low therefore more susceptible to the effects of gravity and this gives rise to a great degree of variability in blood flow within the lung
The matching ratio of the ventilation to perfusion is 1, but where does that majority of mismatch occur
at the apex of the lung
If ventilation is less than perfusion in a mismatch what is the outcome
The ventilation of an alveoli is decreased this means that the blood is not oxygenated, therefore the deoxygenated blood will further dilute the oxygenated blood from other alveolus, and CO2 levels increase
what is the passage of blood through poorly ventilated alveoli (areas) called
shunt
What is the control mechanism in response to a shunt?
Constriction of the under ventilated arteriole diverting the blood flow to better ventilated alveoli
What triggers the constriction of the arteriole in the response of a shunt
Hypoxia
What does the increasing CO2 levels due to a shunt cause
Mild bronchodilation
What create the alveolar dead space
When the ventilation is greater than the perfusion
What is the outcome of alveolar dead space
Increase alveolar PO2, which causes pulmonary dilation
Decrease alveolar PCO2, which causes bronchial constriction
The response eventually returns the ventilation perfusion ratio back to one
The results of the alveolar dead space is opposite to the effects of what
shunt
what is the Physiological Dead Space composed of
alveolar dead space and the anatomical dead space
Define Anatomical Dead Space
refers to air in the conducting zone of the respiratory tract unable to participate in gas exchange as walls of airways in this region are to thick
What is the pulmonary arterial pressure
systolic - 25mmHg
diastolic - 8mmHg
Why is overall rates of equilibrium for oxygen and CO2 similar
because greater pressure difference for oxygen
Moving from 100mmHg to 40mmHg compared to CO2
What action is the pulmonary circuit involved in
gas exchange
What is the partial pressure gradient of oxygen and CO2 from the alveoli to the blood capillaries
O: 100mmHg to 40mmHg = 60mmHg
CO2: 46mmHg - 40mmHg = 6mmHg
How is the partial pressure gradient for CO2 much less that oxygen but displace a similar volume per minute
CO2 is more soluble than oxygen so diffuse easier
How many Kpa are their per 1mmHg
0.133
What is the abbreviation A and a stand for
A - alveolar pressure
a - arterial blood pressure (oxygenated blood)
What is the volume of gas exchange in the alveoli for oxygen and CO2
oxygen - 250ml/min
CO2 - 200ml/min
what circulation is shunt more common to occur in
Bronchial circulation
what does it mean in the oxyhaemoglobin dissociation curve moves to the right
HB increased affinity
