Lecture 5 (Respiration 2) Flashcards
What is total ventillation?
Total ventilation is the volume of air moved out of the lungs per unit time
How do you calcite total ventilation? (at rest)
And what should the values be at rest?
Total ventilation = Tidal volume x Breathing frequency
6 litres/min = 0.5 litres x 12 breaths per minute
What two zones are the respiratory system made up of? (2)
Respiratory system
Conducting zone
Which zone of the respiratory system does gas exchange take place in?
Respiratory zone
Why doesn’t all the fresh air reach the alveoli?
Some air stays in dead zone
How much CO2 do we produce per minute?
200ml
How does partial pressure change when hyperventilating?
Same amount of CO2 released, bigger volume is expired so partial pressure drops from 40 to 20?
What happens when you hyperventilate? (3)
-Decreased partial pressure
-Reduces CO2 in blood
-So you have Alkalosis
What happens when you hypoventilate? (3)
-Increased partial pressure
-Increases CO2 in blood
-So you have Acidosis
How does ventilation change at different parts of the lung? (2)
-Lowest ventilaltion as Apex
-Highest ventilation at Base
Describe the parts of the lung (apex and base) in terms of compliance and starting volume? (2)
At apex = larger starting volume – lower compliance
At base = smaller starting volume – higher compliance
How does gravity affect ventilation in lungs?
If your upside down ventilation rate switches so highest is always at the bottom and west at top
Why is ventilation lower at top of lungs? (3)
-At top of lungs have the lung weight pulling down, creates a greater vacuum (more negative pressure)
-Leads to alveoli in apex having greater starting volume
-and lower compliance
Why is ventilation higher at bottom of the lungs? (2)
-Weight pushes down and reduces interpleural pressure
What is Compliance?
Compliance is link between change in volume and pressure
What is Perfusion?
The passage of blood through vessels
What are the two types of blood pressure and explain them? (4)
-Systemic and pulmonary blood pressure
-Systemic is high pressure system with a high resistance
-Pulmonary is a low-pressure system with a low resistance
Why is pulmonary blood pressure low?
Blood only needs to go from heart to top of the lungs in pulmonary so only low pressure needed
Why is system blood pressure high?
Because blood needs to be pumped around the body
What is the relation of volume per min between systemic and pulmonary pressure?
The volume must stay the same inn both cirulations
When is pulmonary resistance at its lowest?
When lungs are at Functional Residual Capacity
What is residual capacity and functional residual capacity? (2)
Functional residual capacity - the volume remaining in the lungs after a normal, passive exhalation
Residual capacity - the volume remaining when you have expired as much air as possible
What is pulmonary resistance linked to? (2)
Resistance in lungs is linked between circulation and volume
What are the two types of blood pressure in the lungs? (pulmonary circulation)
Alveolar Vessels: Capillaries and slightly larger vessels surrounded on all sides by alveoli
Extra-Alveolar Vessels: vessels that are not surrounded by alveoli
What is transmural pressure?
Transmural pressure is volume in alveoli and blood vessel
What happens with changes in inter-pleural pressure (high or low) in terms of diameter of vessels and resistance? (4)
-Larger vacuum in inter-pleural space has effect of expanding extra alveolar vessels and resistance goes down
-Small interpleural pressure, diameter of vessels gets smaller so more resistance
When is the pulmonary resistance at its lowest?
At functional residual capacity
How does resistance go down at residual capacity? (3)
When Residual volume, expired as much air as you can
-So alveoli have a small volume
-Allows capillaries and blood vessels for space to expand
-These vessels have lower resistance
How does resistance go up when breathing in? (3)
When you breathe in lungs expand,
-Alveolar volume expands
-Compresses capillaries, diameter of vessels goes down
-Resistance goes up
How do extra-alveolar vessels differ in terms of resistance when you breathe in and out? (2)
-Effects reversed so resistance goes up when you breathe out
-Goes down when you breathe in
How do Alveolar vessels change in terms of resistance when you breathe in and out? (2)
-Resistance goes down when you breathe out
-Goes up when you breathe in
What are the 3 states capillaries are in at the lungs? (3)
-At rest capillaries are open and allow blood to flow through
-Capillaries that are open, pressure is enough to keep them open but not force blood through
-And some that are completely closed with no blood blow
What is capillary recruitment?
Having capillaries in different states
-open allow blood
-open don’t allow blood
-closed don’t allow blood
That open with increased pressure and allow blood to flow
What is the purpose of capillary recruitment? (2)
-So pulmonary circulation can accommodate extra pressure and flow of blood
-By opening up these vessels you reduce resistance as there is more pathways for blood to flow through
What does lung perfusion depend on? (2)
Perfusion depends on your posture and gravity
How does perfusion change in different parts of the lung? (3)
-At the base of the lung, we tend to have maximum perfusion and minimum at apex
-Slight dip at the very base
Where is the reference point for pulmonary circulation pressures?
Outside the heart at the level of the left atrium
What is the pressure in pulmonary arterials and venues? (2)
PPA - Pressure in pulmonary arterioles – Mean of about 15mmHg = 20 cm H2O
PPV - Pressure in pulmonary venules - Mean of about 8mmHg = 10 cmH2O
How do Pv and Pa (pulmonary article/venule pressure) change even 1cm above of below heart?
Drops by 1cm of H2O
What is Pa (alveolar pressure) relative to?
Model pressure is relative to atmospheric pressure, the model considers the point when there is no movement of air (when no difference pressure is 0cm H2O)
What is Ptm?
Transmural pressure gradient across the wall of the vessel
When is zone 1 used in lung?
Zone 1 only occurs in hemorrhage or when connected to ventilator where air is forced into lungs
(Blood vessels squeezed down preventing blood flow, low pressure)
Where is zone 2 of the lung?
Above the heart
Describe the pressure in zone 2 of the lungs? (3)
-The higher you go the pressure drops off a bit
-Same gradient drop and pressure in alveoli
-Blood vessel capillary is constricted
-The closer you go to level of heart the less the blood vessel capillary is constricted
-Small increases in pressure is enough to pop open these vessels
Describe zone 3 in the lung in terms of pressure and blood flow? (3)
-Added pressure from gravity, expand capillaries that accommodate more blood flow
-At the base of the lung more drop off, capillaries expanded through alveoli and extra are constricted due to low inter-pleural pressure
-Low blood flow into capillaries due to constriction of alveolar vessels
How do you find ventilation/perfusion ratio?
What does this influence?
-Ratio = Ventilation / Perfusion
-Blood gas composition
Where in the lung is Ventilation perfusion ratio highest and lowest? (2)
Ventilation perfusion ration is highest at base and lowest at apex
When does ventilation/perfusion ratio become infinity?
In dead space
Because there is no exchange the gas composition in the affected alveoli becomes the same as moist inspired air
What happens at local reduction of ventilation (shunt)? (3)
(caused by tumor of foreign body)
V/P ratio goes towards 0 and body reacts by redirecting air to other areas of lungs, local bronchoconstriction and vasoconstriction to parts of the lung
How do you get Ventilation/Perfusion mismatch?
Sleviolar dead space - ratio goes to 0
How do you get Ventilation/Perfusion mismatch?
Sleviolar dead space - ratio goes to 0
How do you get Ventilation/Perfusion mismatch?
Sleviolar dead space - ratio goes to 0
