Q: A patient is receiving oxygen therapy at sea level. If the atmospheric pressure is 760 mm Hg and the oxygen concentration in the air is 21%, what is the partial pressure of oxygen ($$P_{O_2$}) in $$the inspired air?

$$P_{O_2$} = 760 \times 0.21 = 159.6 mm Hg$$

Q: A climber ascends to high altitude where atmospheric pressure drops to 500 mm Hg. If oxygen remains 21% of the air, what is the new partial pressure of oxygen ($$P_{O_2$}$$)?

$$P_{O_2$} = 500 \times 0.21 = 105 mm Hg$$

Q: A patient’s functional residual capacity (FRC) is measured using the helium dilution technique. If the initial helium concentration ($$C_1) is 10$$%, the final concentration ($$C_2) is 7$$%, and the initial volume ($$V_1) is 3 L$$, what is the FRC ($$V_2$$)? Use the formula $$V_2$$ = $$V_1$$ \left( \frac{$$C_1$$}{$$C_2$$} - 1 \right)$$.

$$V_2 = 3$$ \left( \frac{10}{7} - 1 \right) = 3 \left(1.4286 - 1\right) = 3 \times 0.4286 = 1.286$$ L

Question 1

A patient is receiving oxygen therapy at sea level. If the atmospheric pressure is 760 mm Hg and the oxygen concentration in the air is 21%, what is the partial pressure of oxygen ($$P_{O_2$}) in $$the inspired air?

Accepted Answer

$$P_{O_2$} = 760 	imes 0.21 = 159.6 mm Hg$$

Question 2

Which equation correctly represents the Ideal Gas Law?

Accepted Answer

$$PV = nRT$$

Question 3

According to Boyle's Law, what happens to the pressure of a gas if the volume is halved while temperature and amount of gas remain constant?

Accepted Answer

The pressure doubles

Question 4

Dalton's Law states that the total pressure of a mixture of gases is:

Accepted Answer

The sum of the partial pressures of each individual gas

Question 5

A climber ascends to high altitude where atmospheric pressure drops to 500 mm Hg. If oxygen remains 21% of the air, what is the new partial pressure of oxygen ($$P_{O_2$}$$)?

Accepted Answer

$$P_{O_2$} = 500 	imes 0.21 = 105 mm Hg$$

Question 6

Which of the following best describes Henry's Law in the context of respiration?

Accepted Answer

The amount of gas dissolved in a liquid is proportional to its partial pressure in the gas phase

Question 7

Which factor will most significantly decrease airway resistance according to Poiseuille’s Law?

Accepted Answer

Increasing the radius of the airway

Question 8

A patient’s functional residual capacity (FRC) is measured using the helium dilution technique. If the initial helium concentration ($$C_1) is 10$$%, the final concentration ($$C_2) is 7$$%, and the initial volume ($$V_1) is 3 L$$, what is the FRC ($$V_2$$)? Use the formula $$V_2$$ = $$V_1$$ \left( \frac{$$C_1$$}{$$C_2$$} - 1 \right)$$.

Accepted Answer

$$V_2 = 3$$ \left( \frac{10}{7} - 1 ight) = 3 \left(1.4286 - 1ight) = 3 	imes 0.4286 = 1.286$$ L

Question 9

Which of the following is NOT measured directly by simple spirometry?

Accepted Answer

Residual Volume (RV)

Question 10

During inspiration, which of the following best explains why air flows into the lungs?

Accepted Answer

Alveolar pressure drops below atmospheric pressure

Question 11

If the total pressure of a gas mixture is 760 mm Hg and the partial pressures of $$N_2$$, $$O_2$$, $$CO_2$$, and $$H_2O$$ are 600 mm Hg, 150 mm Hg, 5 mm Hg, and 5 mm Hg respectively, which law is being demonstrated and what is the sum of the partial pressures?

Accepted Answer

Dalton's Law; $$600 + 150 + 5 + 5 = 760 mm Hg$$

Question 12

Which of the following changes would most likely increase the functional residual capacity (FRC) in the lungs?

Accepted Answer

Decreased elastic recoil of lung tissue

Question 13

A patient with Coal Worker's Pneumoconiosis (Black Lung Disease) is likely to have which of the following changes in lung function?

Accepted Answer

Decreased cross-sectional airway area and increased airway resistance

Question 14

Which of the following best describes the relationship between airway diameter and resistance to airflow?

Accepted Answer

Resistance is inversely proportional to the fourth power of the radius ($$R \propto \frac{1}{r^4$})$$

Question 15

Which of the following is a direct consequence of humidifying inspired air in the respiratory tract?

Accepted Answer

The partial pressure of oxygen in alveolar air decreases

Question 16

If a patient’s tidal volume (TV) is 500 mL, expiratory reserve volume (ERV) is 1200 mL, and residual volume (RV) is 1300 mL, what is the functional residual capacity (FRC)?

Accepted Answer

$$FRC = ERV + RV = 1200 + 1300 = 2500 mL$$

Question 17

Which of the following statements about positive pressure ventilation is correct?

Accepted Answer

Air is pushed into the lungs by increasing pressure at the airway opening

Question 18

Which of the following is the correct formula for calculating airway resistance ($$R) $$using Poiseuille’s Law?

Accepted Answer

$$R = \frac{8 \eta L}{\pi r^4$}$$

Question 19

Which of the following is a major determinant of the bulk flow of air during ventilation?

Accepted Answer

The difference in pressure between alveoli and atmosphere

Properties of Air, Gas Laws, and Functional Lung Volumes

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