2nd semester Ventilation
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What must you have for flow to occure?
A pressure gradient
What is the formula for volume flowrate according to Poisuilles Law?
What is the formula for resistance to flow according to Poisuilles Law?
What is Reynolds number?
The ratio of the fluids initial forces to its drag forces . It is a unit less number, and when it reaches 2000 the gas flow becomes turbulent
Turbulent flow normally happens in which airways? and laminar flow normally happens in what airway?
Laminar flow = smaller airways
Turbulent flow = larger airways
Increased elastic resistance normally happens with what disease?
Increased air flow resistance normally happens with what type of diseases?
Asthma and emphysema
(means they need more time to get the air out)
What is minuet ventilation?
How is it measured?
What is the normal value?
"F" is the same as "__".
1. Volume/Time moved into or out of the lungs
2. Measured by collecting expired volume for a fixed time
3. Normal value is 6.0 L/min
(F (frequency) & RR (resp. rate) are the same thing)
What is "Anatomic Dead Space"?
What areas does it include? (5)
What does ventilation of those areas result in?
1. anatomic dead space is a volume of the lung that is not involved in gas exchange
2. this includes : the mouth, pharynx, larynx, trachea, and bronchi
3. ventilation of these areas results in no gas gas exchange
1.)What is optimal gas exchange?
2.)What type of capillary blood flow do the well ventilated areas and poorly ventilated areas?
1.) Individual regions of the lung are ventilated in proportion to their capillary blood flow
2.) well ventilated regions ideally have high capillary blood flows, and poorly ventilated regions ideally have little capillary blood flow.
In real lungs, ventilation and blood flow are not ______.
Some areas have dead space or shunt. what does dead space and shunt mean?
Gas exchange is ____ _____ _____ in portions of the lung.
2. Dead space- well ventilated but poorly perfused regions
Shunt- poorly ventilated but well perfused regions
3. less than optimal
With alveolar dead space you should treat the lung as if ...... ?
You should partition ....?
as if only two type as of alveoli exist; those with ideal gas exchange and those without.
partition poorly ventilated units
Alveolar dead space (VDA) "as if" ....
volume contained in the units with no gas exchange.
Does dead space get involved with blood flow or gas exchange?
What is the definition of physiological dead space?
The total effective volume of the lung NOT involved in IDEAL gas exchange
More dead space = increased ____.
In a healthy supine individual;
1. Their ventilation and perfusion should be relatively _____.
2. What should their alveolar dead space be at?
3. Their physiological d.s and anatomical d.s should be _____.
4. What increases physiological d.s? (2)
2. alveolar d.s near zero
3. phys. d.s = anatomical d.s
4. upright position, and when disease alters ventilation / perfusion relationships
What is the Bohr Equation?
What is the foundation for this equation? (3 points)
- 1. Used to measure physiological dead space
- (average of exhaled CO2)
- 2. Foundation:
- a. All Co2 comes from alveolar gas (none from dead space or atmosphere).
- b. Arterial PaCO2 equals alveolar PACO2
- c. Conservation of mass
What is the Bors equation formula for arteries and alveoli?
- Vd PACO2 - PECO2
- --- = ------------------
- VT PACO2
(same for arterial. Just replace "PACO2" with "PaCO2" )
What are the normal values for Bohrs equation?
- Vd 40 mmHg - 28 mmHg
- --- = ------------------------- = 0.3
- VT 40 mmHg
Vd = 0.3 (500 ml) = 150 ml
Ventilator adjustments and respiratory efficiency:
1. What happens when you increase tidal volume? (2)
2. What happens when you increase respiratory frequency? (2)
1. alveolar ventilation INCREASES & dead space ventilation is UNCHANGED.
2. alveolar ventilation INCREASES & dead space ventilation INCREASES
What 2 major things happen within the alveoli? (2-2)
- O2 consumption:
- 1. rate O2 enters the alveoli
- 2. rate taken up by blood
- CO2 production:
- 1.rate released by blood
- 2.rate CO2 expired
- normal values= 200 <-- CO2 produced
- 250 <--O2 consumed
1.What are the normal values for the Respiratory Exchange Ratio?
2.What is the ratio normally less than?
3.What does this mean?
1. CO2 production =200 ml/min
O2 consumption =250 ml/min
2. ratio is normally less than 1.0
3. This means that expiratory minuet ventilation is slightly LESS than inspiratory minuet ventilation.
What is the RQ formula?
what substrate utilization can change these values? (4)
RQ (lung) equals RQ ______ in steady a state?
1. CO2 production / O2 utilization in the cell metabolism
3. carbohydrates = 1.0 (highest), fats =0.7, proteins = 0.8, average mixed diet = 0.8
RQ (lungs) = RQ (cell metabolism) in a steady state.
Factors determining alveolar PCO2:
1. Does inspired air have CO2?
2. When you increase CO2 production, what happens to alveolar PCO2?
3. When you increase alveolar ventilation (VA), what happens to alveolar PCO2?
2. increases alveolar PCO2
3. Decreases alveolar PCO2
What are 3 things that can increase CO2 production?
exercise, fever, or hyperthyroidism (increased metabolic rate)
What are 3 factors that determine alveolar PO2? and what does it increase or decrease alveolar PCO2 & PO2. ?
1. Inspired O2
2. Increases metabolic activity (increase oxygen uptake and DECREASES alveolar PO2)
3. Increases alveolar ventilation (increase flow of fresh air through alveoli and INCREASES alveolar PO2.
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