The primary functions of the lungs are gas exchange, maintaining acid-base status, filtering blood, acting as a blood reservoir, and metabolizing some compounds. The blood-gas interface is ideally suited for gas exchange, with a large surface area of around 100 square meters and a thin surface of 0.3 micrometers. Room air is 21% oxygen, and the partial pressure of oxygen in inspired gas can be calculated using an important equation. Pulmonary blood pressure is very low at around 15 mmHg due to the low resistance of pulmonary circulation, while systemic blood pressure is around 80 mmHg.

1. Pulmonary Physiology
CHAPTER 1
Structure and Function

2. Primary functions of the lung
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Gas exchange
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Bring in O2
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Remove CO2
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Maintain acid base status
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Filter blood
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Blood reservoir
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Metabolizes some compounds

3. Blood-Gas Interface
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Ideal suited for gas exchange
–
Large surface area
●
–
Thin surface
●
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“the size of a tennis court”-100 square meters
0.3 micrometers (1/1,000,000)
Diffusion (or movement of gas) is proportional
to surface area and inversely proportional to
thickness

4. Air
●
●
●
Room air is 21% oxygen
The partial pressure of oxygen in inspired gas
is calculated by multiplying the percent oxygen
by atmospheric pressure (after subtracting
water vapor)
This is a very important equation. You will see
it again.
–
Po2=FiO2(760-47)

5. Example
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0.5 x (760-47) = 356 mm Hg

6. Breathing
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Not all the air we breath in is used for gas
exchange
–
The airways used to get air to the alveoli are the
conducting airways (figure 1-4 in text).
●
●
This contributes to dead space
Any area of ventilated lung that is not perfused it dead
space

7. Blood Flow
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Pulmonary arterial blood pressure is very low
–
–
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Due to low resistance of pulmonary circulation
Normal pressure about 15 mmHg
Systemic blood pressure is about 80 mm Hg

8. Structure and Function
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Normal CT

9. Structure and Function
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Interstitial lung disease

10. Structure and Function
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Food for thought
–
How do other lung diseases show how structure
affects function?
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How is this demonstrated radiographically?
–
How is this demonstrated on blood gases?