Ch. 7 Beachey

What is the most common cause of resting hypoxemia?

• A mismatch between ventilation and diffusion

• A mismatch between ventilation and permeability

• A mismatch between ventilation and dead space

• A mismatch between ventilation and blood flow

Why is N2O the ideal gas for measuring the extent to which pulmonary blood contributes to the diffusion rate?

• Blood can absorb N2O at a greater rate than N2O can diffuse across the alveolar-capillary membrane.

• If N2O is inhaled, the pulmonary capillary blood reaches its maximum capacity for N2O almost instantly.

• If N2O is inhaled, the pulmonary capillary blood reaches its maximum capacity for N2O slowly.

• Blood can absorb N2O at a slower rate than N2O can diffuse across the alveolar-capillary membrane.

Which of the following is the main limiting factor for oxygen transfer rate?

• Perfusion

• Diffusion

• Solubility

• Molecular weight of the gas

If oxygen equilibrium between the alveolus and capillary never occurs because of thickened membranes, oxygen transfer is then truly:

• perfusion limited.

• diffusion limited.

• concentration limited.

• perfusion and diffusion limited.

Why is CO the ideal gas for measuring the extent to which the alveolar-capillary membrane itself impedes the diffusion rate?

• Blood can absorb CO at a greater rate than CO can diffuse across the alveolar-capillary membrane.

• CO is lighter than O2.

• CO can diffuse across the alveolar-capillary membrane faster than blood can absorb it.

• CO is heavier than O2.

When breathing 21% oxygen, what is the inspired oxygen partial pressure?

• Approximately 80 mm Hg

• Approximately 100 mm Hg

• Approximately 140 mm Hg

• Approximately 160 mm Hg

Which of the following conditions can increase the length of the diffusion path?

• Fibrotic thickening of alveolar and capillary walls

• Surfactant in the alveoli

• Capillary vasocontriction

• Presence of alveolar macrophages

How do you obtain the diffusion capacity for oxygen?

• It is obtained by multiplying DLCO by 1.23.

• It is obtained by multiplying DLCO by 24.

• It is obtained by dividing DLCO by 1.23.

• It is obtained by dividing DLCO by 24.

The DLCO is useful in differentiating emphysema from what other obstructive diseases?

• Asthma

• Pneumonia

• ARDS

• Bronchiectasis

What is the PAO2 of a person breathing room air at sea level, with a PaCO2 equal to 40 mm Hg and an R equal to 0.8?

• Approximately 80 mm Hg

• Approximately 90 mm Hg

• Approximately 100 mm Hg

• Approximately 110 mm Hg