Q: Calculate the alveolar ventilation rate for a person with a tidal volume of 500 mL, a dead space of 150 mL, and a respiratory rate of 12 breaths per minute. Use the formula: $$AVR = (V_T - V_D) \times f.$$

$$AVR = (500 - 150) \times 12 = 4,200 mL/$$min

Question 1

Which type of hypoxia is most likely to occur in a patient with severe anemia, and why?

Accepted Answer

Anemic hypoxia, because the blood cannot carry enough oxygen due to low hemoglobin.

Question 2

A climber at high altitude experiences shortness of breath and low arterial $$P_{O_2$}. $$Which type of hypoxia is this, and what is the primary cause?

Accepted Answer

Hypoxic hypoxia; due to low environmental oxygen.

Question 3

Which law explains why air flows into the lungs during inspiration?

Accepted Answer

Boyle's Law: $$P_1$$ $$V_1$$ = $$P_2$$ $$V_2$$

Question 4

During normal quiet breathing, which muscle is primarily responsible for inspiration?

Accepted Answer

Diaphragm

Question 5

A patient suffers a puncture wound to the chest, resulting in a pneumothorax. What happens to the intrapleural pressure and the lung?

Accepted Answer

Intrapleural pressure increases to atmospheric pressure, causing lung collapse.

Question 6

According to the Law of Laplace, what happens to the pressure inside a smaller alveolus compared to a larger one, assuming equal surface tension?

Accepted Answer

The pressure is higher in the smaller alveolus.

Question 7

Which cell type is responsible for producing pulmonary surfactant, and what is its main function?

Accepted Answer

Type II alveolar cells; reducing surface tension

Question 8

A newborn is diagnosed with infant respiratory distress syndrome (IRDS). What is the underlying physiological problem?

Accepted Answer

Low surfactant production, causing high surface tension and alveolar collapse

Question 9

Why is the partial pressure of oxygen ($$P_{O_2$}) in $$the alveoli (~100 mmHg) lower than in atmospheric air (~160 mmHg)?

Accepted Answer

Because anatomical dead space causes mixing of fresh and stale air.

Question 10

Calculate the alveolar ventilation rate for a person with a tidal volume of 500 mL, a dead space of 150 mL, and a respiratory rate of 12 breaths per minute. Use the formula: $$AVR = (V_T - V_D) 	imes f.$$

Accepted Answer

$$AVR = (500 - 150) 	imes 12 = 4,200 mL/$$min

Question 11

Which of the following best describes the effect of obstructive pulmonary diseases (e.g., asthma, COPD) on lung volumes?

Accepted Answer

Decreased inspiratory capacity and increased residual volume

Question 12

During forced expiration, which muscles are primarily recruited to assist the process?

Accepted Answer

Internal intercostals and rectus abdominis

Question 13

If the compliance of the lung decreases, what is the most likely physiological consequence?

Accepted Answer

The lungs become stiffer, making inspiration more difficult.

Question 14

Which of the following equations correctly represents the Law of Laplace as it applies to alveoli?

Accepted Answer

$$P = \frac{2T}{r}$$

Question 15

A patient with carbon monoxide poisoning is experiencing hypoxia. Which type is this and why?

Accepted Answer

Anemic hypoxia; CO binds hemoglobin, preventing oxygen transport.

Question 16

Which of the following best explains why expiration is more difficult than inspiration in obstructive lung diseases?

Accepted Answer

Airways narrow during expiration, increasing the effect of obstructions.

Question 17

Which of the following is true regarding the relationship between alveolar pressure and atmospheric pressure at the end of inspiration?

Accepted Answer

Alveolar pressure equals atmospheric pressure.

Question 18

Which of the following best describes the function of surfactant in the lungs?

Accepted Answer

It decreases surface tension, especially in small alveoli, to prevent collapse.

Question 19

A patient with a pulmonary embolism (blood clot in the lung) is most likely to experience which type of hypoxia?

Accepted Answer

Ischemic hypoxia

Question 20

Which of the following best explains why mammals are considered 'tidal breathers'?

Accepted Answer

Air enters and exits the lungs through the same pathway.

Respiratory System: Mechanics, Gas Exchange, and Pathology

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