Cardiopulmonary Anatomy & Physiology: Essentials of Respiratory Care: RTAD 122 Respiratory Physiology Diffusion Questions Flashcards

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Des Jardins Ch 4 and 19
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Define diffusion of pulmonary gases and differentiate between diffusion gradients and pressure gradients.

Pulmonary gases-Oxygen and Carbon dioxide diffuse until they are in balance
between the blood and the alveoli.

Pressure gradients- move gas form high to low pressure concentration and primary mechanism is to move air in and out of the lungs (move in the same direction in or out of the lungs)

Diffusion gradient-movement of individual gas from high to low concentration (individual gas continue to move independently from other gases from high pressure area to low pressure area)


Describe the transfer of gas molecules across the alveolar capillary membrane.

The passive movement of gas molecules from area of high partial pressure to area of low partial pressure until balance occurs

Must diffuse through the alveolar-capillary
membrane 9 layers in about .75 secs


3. Explain Dalton’s law in its relationship to gas mixtures and partial pressure of gases.

Each gas generates its own pressure

The pressure of the total gas mix is equal to the
sum of the partial pressures of each separate gas


4. Barometric pressure (PB) is primarily derived from what four gases?

Nitrogen, Oxygen, Carbon dioxide, and Argon


5. What is the (PB) at sea level and relate this to Dalton’s law?


The barometric pressure is a function of daltons law and pressure is the sum of the gases N2,02,C02, and argon


6. According to Dalton’s law, if, in dry air, Nitrogen had a partial pressure of 600.8 mm Hg, Oxygen 159.0
mm Hg, and Carbon Dioxide 0.2 mm Hg, the total pressure would equal?



7. What effect will an increase or decrease of the (PB) have on the percent concentration of an atmospheric

even though barometric pressure decreases with altitude, concentration of all atmospheric gases remains the same at both high and low elevations

In other words, percentage of oxygen always approximately 21 percent


8. In Keystone Colorado, and I hit the golf ball (successfully) and then I go to sea level and hit the same golf
ball identically to my drive in Colorado, which ball will have more yardage and why?

The golf ball in Colorado due to the BP being less


9. Compare the partial pressures of gases in the air, alveoli, and blood.



Carbon dioxide-0.2

Water Vapor-0.0

Nitrogen dioxide-600.8



Carbon dioxide-40.0

Water Vapor-47.0

Nitrogen dioxide-573.0



Carbon dioxide-40.0

Water Vapor-47.0

Nitrogen dioxide-573.0


10. Referring to table 4-1 in your text, explain why the partial pressure of oxygen is higher in dry air as
compared to the partial pressure of oxygen in alveolar gas.

It has to compete with PAC02 and water vapor partial pressure


11. Begin to familiarize yourselves with the ideal alveolar gas equation (refer to Dave’s lecture).

PACO2=(PB-PH02) FIO2-PaCO2(1.25)


12. Name and locate the 9 layers of the alveolar-capillary membrane that gas molecules must diffuse through.

Just know there are 9 layers of the alveolar capillary membrane that gas molecules diffuse through


13. Name several conditions that may increase the alveolar-capillary membrane thus inhibiting the movement
of gases across it.

Alveolar collapse(Atelectasis)

Thickening of alveolar wall(alveolar fibrosis)

Alveolar capillary destruction(emphysema)

Alveolar consolidation (pneumonia)

Frothy secretions (pulmonary edema)

Interstitial edema


14. From the point of non-oxygenated blood entering the alveolar-capillary membrane system, to the
oxygenated blood leaving the system, explain how the diffusion process works.

Oxygen moves from the alveoli into the blood and the CO2 moves from the blood to the alveoli


15. In a resting healthy individual, under normal conditions, state how many seconds it take for oxygen
pressure and carbon dioxide pressure to reach equilibrium and to move through the alveolar-capillary
system (total transit time).

.075 seconds


16. Contrast the above normal conditions with those of exercise and various pulmonary disease states.

During exercise blood passes through the alveolar-capillary system at a faster rate

Time for diffusion decreases to less than 0.75 seconds

Healthy lungs will meet the time requirement
for diffusion to take place as it should
PaO2 100 mm Hg

Pulmonary diseases
Time for diffusion to take place may not be
adequate causing a reduced
PaO2 60 mm Hg


17. In the presence of certain pulmonary disease, the time available to achieve oxygen equilibrium in the
alveolar-capillary system may not be adequate. How will this affect the PaO2?

It will decrease


18 Explain how Fick’s Law relates to gas diffusion and how it can be applied to certain clinical conditions.

Directly proportional

decreased alveolar surface area-alveolar collapse or alveolar fluid decreased ability of O2 to enter the pulmonary capillary blood

decreases PA02 (P1-P2)-high altitude or hypoventilation

decreased the diffusion of 02 into the pulmonary capillary blood(FIO2 increase pressure gradient)

Inversely related- increased avleolar tissue thickness- alveolar fibrosis or edema or decreased movement of 02 across the alveolar capillary membrane


19. Contrast perfusion limited and diffusion limited.
Additional Reading – Chapter 19

Perfusion-The transfer of gas across the alveolar wall is function amount of blood that flows past Alveoli

Diffusion limited The movement of gas across the alveolar wall is the function of the integrity of the alveolar capillary membrane itself


20. Explain the effects of altitude on atmospheric PO2, thePAO2 and the PaO2.

all are decreased


21. Define acclimatization and why this process is necessary before ascending into high altitudes.

If you ascend to high altitudes from sea level, you
need to adjust

If sudden exposure to an altitude such as the summit of Mount Everest occurs without acclimatization, loss of consciousness could occur
in minutes due to oxygen tension


22. Explain the term chronic hypoxia and how it relates to altitude.

not enough oxygen reaching the tissues


23. At altitude, how is the oxygen carrying capacity of the blood improved?

– Stimulant for RBC production from bone marrow

RBC production for 6 weeks and production
levels out