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CRRAB II- FINAL > Pulmonary Phys- Trachte > Flashcards

Flashcards in Pulmonary Phys- Trachte Deck (66):

How do gases move across the blood-gas interface?

Goes from high pressure to low pressure!


What 2 things does gas movement across a barrier depend on?

Cross sectional area


What makes up the anatomical dead space?

Trachea to terminal bronchioles

(longer neck = increased dead space!)

NOTE* intubation can also increase dead space


What does compliant mean in terms of the lungs? What would increase it? decrease it?

Change in lung volume for a given change in pressure (stiffness)

-Compliance is decreased in pulmonary fibrosis, pneumonia, pulmonary edema

-Compliance is increased in emphysema, normal aging


What is the role of surfactant?

reduces surface tension and prevents alveolar collapse

**probably represents a key factor allowing for terrestrial life


What are the 4 general causes of reduced oxygen in the blood?

1. reduction in ventilation
2. Drugs (opiates)
3. brain damage
4. breath holding


What is tidal volume?

The amount of air inspired and expired in each breath

Usually around 500 mls


What is vital capacity?

the maximum volume of air that can be exhaled after a maximum inspiration

Usually about 6,000 ml


What is residual volume?

the amount of remaining in the lungs after a maximal expiration (never able to get rid of it, unless your lung collapses).
In a maximal expiration you are blowing out your expiratory reserve volume.

Usually about (1,500 mL)


What is functional residual capacity?

the amount of air remaining after a typical exhalation
(expiratory reserve volume + residual volume)


What does smoking paralyze in the lungs?

mucous-ciliary elevator


What is the volume amount remaining after a typical exhalation?

2500 mL (residual volume + expiratory reserve volume)

Function residual Volume = expiratory reserve volume + residual volume


How do you measure the functional residual capacity?

Helium gas dilution technique


What is total ventilation?

the amount of air entering and leaving the lung each MINUTE

Tidal volume x respirations per minute


What happens to functional residual capacity in obstructive diseases?

It goes UP!


How do you determine the volume of dead space?

Fowler's single breath N2 washout


Which part of the lungs are ventilated better?

Lower regions of the lung are ventilated better than upper regions


What is the driving force of diffusion?

PRESSURE difference


Is CO a diffusion or perfusion limited?

Diffusion limited!

Only the diffusion barrier is creating resistance to flow of air, RBC affinity is so great that little rise in the blood partial pressure of carbon monoxide with tie in the capillary


Is O2 a diffusion or perfusion limited process?

Perfusion limited!

It is going to equilibrate and stop moving across barrier unless blood flow increases


What 3 gases are Perfusion Limited?

Nitrous Oxide
Carbon Dioxide


What would you use to measure diffusion capacity?

Use carbon monoxide because it is NOT perfusion limited


What happens to compliance in a pneumothorax?



What is LaPlaces Law?

Tension = (Pressure x radius)/2


If you increase ventilation, the concentration of what alveolar gas will decrease?



Why are lower regions of the lungs ventilated better?

More of a negative pressure


NE, 5HT, and histamine do what to pulmonary vessels?

Contract--increase resistance


Acetylcholine, isoproterenol, and prostacyclin do what to pulmonary vessels?

Relax--decrease resistance


What does the respiratory quotient tell you?
How do you figure it out?

What type of fuel you are burning


Describe the 3 zones of perfusion of pulmonary blood flow.

Zone 1: Alveolar pressure>arterial pressure>venous pressure.
This is the alveolar dead space!! Lung apex

Zone 2: Arterial pressure>Alveolar pressure>venous pressure

Zone 3: Arterial pressure >venous pressure>alveolar pressure....Flow is dependent on the arterial-venous pressure dfference! This is the normal situation in the circulatory system. Occurs in midregions and base of lung.


Describe the mechanism of constriction of blood vessels perfusing hypoxic regions of the lungs.

The inhibition of voltage gated K channels depolarizes the membrane...An increase in intracellular calcium occurs...Vasoconstricion.


why is there less fluid leakage in the lungs than in systemic circulation?

Lower hydrostatic pressure in the capillaries! Good thing


If the gradient for CO2 to move into the alveoli is much smaller than the gradient for oxygen to enter the blood, why do we have equal amounts moving across the alveoli?

CO2 is more permeable!


What is the equation for Alveolar PO2?WE NEED TO KNOW THIS!

Alveolar PO2 = PIO2 - [PACO2/R]

PIO2 is inspired air PO2
PACO2 is alveolar PCO2
R is respiratory quotient (1 if carbohydrates, 0.7 if fat)


Can 100 % O2 correct the hypoxemia resulting from a shunt?



If the PO2 is 150 and the PCO2 is 0 in the alveoli, what are you thinking?

Still ventilated


If the PO2 is 40 and the PCO2 is 46 in the alveoli, what are you thinking?

There is perfusion but no ventilation!


What part of the lung has a higher ventilation/perfusion ratio?



Relate surfactant to the Law of Laplace

P= 2T/r

P= collapsing pressure
T= surface tension
r= radius

Alveoli have a tendency to collapse on expiration as radius decreases - surfactant decreases alveolar surface tension and prevents collapse

It also reduces variation in distending pressures amongst spheres of varying sizes. (prevents small spheres from emptying into larger spheres)


What are two examples of when O2 might become diffusion limited rather than perfusion limited?

-Pulmonary disease states (may have thick diffusion barrier, and so O2 does not become saturated before RBC reaches end of capillary)

-Breathing low PO2 (like at high altitudes) = pressure gradient becomes smaller and results in less diffusion


Is Oxygen still perfusion-limited during exercise?

Yes! Normally O2 saturates 1/3 of the way through the capillary (0.25 sec)

During exercise, blood flow increases dramatically, but saturation still happens before RBC traverses the capillary


During what point in respiration is resistance the lowest?

Resistance is lowest at functional residual capacity


What happens to arteriolar resistance in the lungs as blood oxygen content decreases?

Arteriolar resistance increases as blood oxygen content decreases


What are two causes of hypoxemia when there is a normal A-a gradient?

-Alveolar hypoventilation (may be from suppressed central respiratory drive like sedation, or in disease with decreased inspiratory capacity like myasthenia gravis or obesity)

-Inspiration of air with low PO2 (high altitudes!)


What happens to pO2 and pCO2 in arterial blood during exercise?

Stays the same!!!

Partial pressures change in venous blood (increased pCO2, and decreased pO2)

However there is increased O2 consumption, and increased delivery to tissues! But partial pressure stays the same


In controlling ventilation, what to central chemoreceptors primarily respond to? why?

Respond to increased PaCO2

H+ cannot cross BBB, CO2 diffuses and is converted to bicarb and H+ by CA.


In controlling ventilation, what do peripheral chemoreceptors primarily respond to?

Sense arterial PaO2, and are stimulated by hypoxemia

**also stimulated by hypercapnia but not as important as central chemoreceptors in that regard


In controlling ventilation, what do receptors in the lung respond to primarily?

Pulmonary stretch receptors! (Herring-Breuer Reflex) YOGA!

And irritant receptors


What is the most relevant for day-to-day control of ventilation according to Trachte?

CO2!!! (1 mmHg increased in PCO2, leads to a 2-3 L increase in ventilation if PO2 is held constant)

Except for two conditions: O2 is important in altitude adaptions and COPD.


Why are the lungs less likely to experience edema compared to other circulations?

Low hydrostatic pressure!!


What are some of the metabolic functions of the lungs?

-Inactivates bradykinin (through ace)
NOTE* this is why you get a cough with an ACE inhibitor
-Removes serotonin from circulation
-Metabolizes and synthesizes prostaglandins and leukotrienes


What is an important role of PGE in pulmonary/systemic circulation?

Keeps ductus arteriosis open in fetal circulation

To close - give indomethacin (COX inhibitor)


What are some non-ventilation functions of the lungs?

Reservoir for blood- when we lay down blood drains from the legs to the lungs

Filters blood - thrombi from periphery cannot get to brain!


What 3 things in general would cause an increased A-a gradient?

V/Q mismatch
Diffusion limitations


What are two things can damage the extremely thin walls of pulmonary vessels?

Increased capillary pressure
Increased alveolar pressure


What three things could make oxygen a diffusion limited gas, rather than perfusion limited gas?

High altitudes: decreased pressure gradient

Emphysema: decreased diffusion surface area

Fibrosis: thickened diffusion barrier


What is the fick equation to determine pulmonary blood flow?

Pulmonary blood flow = VO2 consumed/ (CAO2-CVO2)


What is the mechanism for causing hypoxic pulmonary vasoconstriction? Does it involve nerves?

No! Does NOT involve nerves

Uses voltage gated K channels - hyper polarize membrane - increases Ca+ concentration - vasoconstriction


Why is cough a common side effect of ACE inhibitor drugs?

ACE in the lung normally inactivates bradykinin

With an ACE inhibitor there is a higher concentrated of activated bradykinin leading to cough


Which has more affinity for hemoglobin... O2 or CO? How do you treat someone with CO poisoning?

CO has greater affinity! Treat with hyperbaric oxygen


How does decreased pH affect the oxygen association curve?

Shifts right- less affinity for O2


How does increased CO2 affect the oxygen association curve? (Bohr effect)

Shifts right- less affinity for O2


How does increased temperature affect the oxygen association curve?

Shifts right- less affinity for O2


How does increased 2, 3 BPG affect the oxygen association curve?

Shifts right- less affinity for O2


How will emphysema affect compliance of the lungs?

It will increase!

Fibrosis would decrease compliance


Is intrapleural pressure higher at the base or the apex of the lung?

Intrapleural pressure is higher at the apex

Weight of lung pressing against chest wall