Q: A patient has a tidal volume of 500 ml and a dead space volume of 150 ml. If their respiratory rate is 12 breaths per minute, what is their alveolar ventilation rate (AVR)?

$$AVR = 12 \times (500 - 150) = 4200 \text{ ml/min}$$

Q: According to Dalton's Law, what is the partial pressure of oxygen in atmospheric air at sea level if the total atmospheric pressure is 760 mm Hg and oxygen makes up 20.9% of the air?

$$PP_{O_2$} = 760 \times 0.209 = 159 \text{ mm Hg}$$

Question 1

Which of the following best describes transpulmonary pressure, and why is it physiologically important?

Accepted Answer

It is the difference between intrapulmonary pressure and intrapleural pressure; it is essential for keeping the lungs expanded.

Question 2

During quiet inspiration, which muscles are primarily responsible for increasing thoracic cavity volume, and what is the resulting change in intrapulmonary pressure?

Accepted Answer

Diaphragm and intercostal muscles; intrapulmonary pressure drops by about 1 mm Hg below atmospheric pressure.

Question 3

Which equation correctly represents Boyle's Law as applied to pulmonary ventilation?

Accepted Answer

$$P_1$$ $$V_1$$ = $$P_2$$ $$V_2$$

Question 4

Which factor would most likely increase airway resistance during an asthma attack?

Accepted Answer

Parasympathetic stimulation causing bronchoconstriction

Question 5

What is the primary function of pulmonary surfactant, and which cells produce it?

Accepted Answer

It decreases surface tension in alveoli; produced by Type II alveolar cells.

Question 6

Which of the following would decrease lung compliance?

Accepted Answer

Fibrosis of lung tissue

Question 7

A patient has a tidal volume of 500 ml and a dead space volume of 150 ml. If their respiratory rate is 12 breaths per minute, what is their alveolar ventilation rate (AVR)?

Accepted Answer

$$AVR = 12 	imes (500 - 150) = 4200 	ext{ ml/min}$$

Question 8

Which respiratory volume cannot be measured directly by spirometry and why?

Accepted Answer

Residual volume; because it is the air remaining in the lungs after maximal expiration.

Question 9

According to Dalton's Law, what is the partial pressure of oxygen in atmospheric air at sea level if the total atmospheric pressure is 760 mm Hg and oxygen makes up 20.9% of the air?

Accepted Answer

$$PP_{O_2$} = 760 	imes 0.209 = 159 	ext{ mm Hg}$$

Question 10

Which of the following best explains why alveolar air has a lower $$PO_2$$ and higher $$PCO_2$$ than atmospheric air?

Accepted Answer

Conducting zone passageways humidify the air and gas exchange with blood adds $$CO_2$$ and removes $$O_2.$$

Question 11

Which of the following mechanisms is responsible for the coupling of ventilation and perfusion in the lungs?

Accepted Answer

Arteriole diameter changes in response to alveolar $$PO_2$$; bronchiole diameter changes in response to alveolar $$PCO_2.$$

Question 12

Which of the following best describes the oxygen-hemoglobin dissociation curve?

Accepted Answer

It is sigmoidal, indicating cooperative binding of $$O_2 to $$hemoglobin.

Question 13

During vigorous exercise, why does the venous reserve of oxygen become physiologically significant?

Accepted Answer

Because only 25% of $$O_2 is $$unloaded during the first pass through tissues, leaving a reserve for increased demand.

Question 14

Which of the following would shift the oxygen-hemoglobin dissociation curve to the right, facilitating $$O_2$$ unloading at the tissues?

Accepted Answer

Increased temperature, increased $$PCO_2$$, decreased pH

Question 15

Which of the following is NOT a mechanism underlying non-respiratory air movements?

Accepted Answer

Sigh: rapid, shallow breathing to increase $$O_2$$ uptake

Question 16

Which of the following best explains why increasing the depth of breathing is more effective than increasing the rate for improving alveolar ventilation?

Accepted Answer

Deeper breaths increase tidal volume, reducing the proportion of air lost to dead space.

Question 17

Which of the following is the correct formula for lung compliance ($$C_L$$)?

Accepted Answer

$$C_L = \Delta V_L / \Delta P$$

Question 18

Which of the following would most likely decrease the rate of gas exchange across the respiratory membrane?

Accepted Answer

Increased thickness due to pneumonia

Physiology of the Respiratory System: Structured Study Notes

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