Gas exchange Practice Questions

Question 1

A 33-year-old woman is brought to the emergency department 30 minutes after being rescued from a fire in her apartment. She reports nausea, headache, and dizziness. Physical examination shows black discoloration of her oral mucosa. Pulse oximetry shows an oxygen saturation of 99% on room air. The substance most likely causing symptoms in this patient primarily produces toxicity by which of the following mechanisms?

Accepted Answer

Competitive binding to heme

Answer

Inhibition of mitochondrial complex V

Answer

Degradation of 2,3-bisphosphoglycerate

Answer

Oxidation of Fe2+

Answer

Rise in serum pH

Question 2

A 71-year-old man is admitted to the ICU with a history of severe pancreatitis and new onset difficulty breathing. His vital signs are a blood pressure of 100/60 mm Hg, heart rate of 100/min, respirations of 27/min, temperature of 36.7°C (98.1°F), and oxygen saturation of 85% on room air. Physical examination shows a cachectic male in severe respiratory distress. Rales are heard at the base of each lung. The patient is intubated and a Swan-Ganz catheter is inserted. Pulmonary capillary wedge pressure is 8 mm Hg. An arterial blood gas study reveals a PaO2: FiO2 ratio of 180. The patient is diagnosed with acute respiratory distress syndrome. In which of the following segments of the respiratory tract are the cells responsible for the symptoms observed in this patient found?

Accepted Answer

Alveolar sacs

Answer

Terminal bronchioles

Answer

Bronchi

Answer

Respiratory bronchioles

Answer

Bronchioles

Question 3

A 32-year-old woman presents with progressive shortness of breath and a dry cough. She says that her symptoms onset recently after a 12-hour flight. Past medical history is unremarkable. Current medications are oral estrogen/progesterone containing contraceptive pills. Her vital signs include: blood pressure 110/60 mm Hg, pulse 101/min, respiratory rate 22/min, oxygen saturation 88% on room air, and temperature 37.9℃ (100.2℉). Her weight is 94 kg (207.2 lb) and height is 170 cm (5 ft 7 in). On physical examination, she is acrocyanotic. There are significant swelling and warmth over the right calf. There are widespread bilateral rales present. Cardiac auscultation reveals accentuation of the pulmonic component of the second heart sound (P2) and an S3 gallop. Which of the following ventilation/perfusion (V/Q) ratios most likely corresponds to this patient’s condition?

Accepted Answer

1.3

Answer

1

Answer

0.8

Answer

0.5

Answer

0.3

Question 4

An investigator is conducting a study on hematological factors that affect the affinity of hemoglobin for oxygen. An illustration of two graphs (A and B) that represent the affinity of hemoglobin for oxygen is shown. Which of the following best explains a shift from A to B?

Accepted Answer

Increased body temperature

Answer

Decreased serum pCO2

Answer

Increased serum pH

Answer

Decreased serum 2,3-bisphosphoglycerate concentration

Answer

Increased hemoglobin γ-chain synthesis

Question 5

Four days after undergoing an elective total hip replacement, a 65-year-old woman develops a DVT that embolizes to the lung. Along with tachypnea, tachycardia, and cough, the patient would most likely present with a PaO2 of what?

Accepted Answer

85 mmHg

Answer

120 mmHg

Answer

100 mmHg

Answer

110 mmHg

Answer

60 mmHg

Question 6

A 63-year-old man is brought to the emergency department, 30 minutes after being involved in a high-speed motor vehicle collision. He is obtunded on arrival. He is intubated and mechanical ventilation is begun. The ventilator is set at a FiO2 of 60%, tidal volume of 440 mL, and positive end-expiratory pressure of 4 cm H2O. On the third day of intubation, his temperature is 37.3°C (99.1°F), pulse is 91/min, and blood pressure is 103/60 mm Hg. There are decreased breath sounds over the left lung base. Cardiac examination shows no abnormalities. The abdomen is soft and not distended. Arterial blood gas analysis shows:
pH 7.49
pCO2 29 mm Hg
pO2 73 mm Hg
HCO3- 20 mEq/L
O2 saturation 89%
Monitoring shows a sudden increase in the plateau airway pressure. An x-ray of the chest shows deepening of the costophrenic angle on the left side. Which of the following is the most appropriate next step in management?

Accepted Answer

Insertion of a chest tube

Answer

CT scan of the chest

Answer

Administer levofloxacin

Answer

Close observation

Answer

Increase the PEEP

Question 7

A 35-year-old woman volunteers for a study on respiratory physiology. Pressure probes A and B are placed as follows:
Probe A: between the parietal and visceral pleura
Probe B: within the cavity of an alveolus
The probes provide a pressure reading relative to atmospheric pressure. To obtain a baseline reading, she is asked to sit comfortably and breathe normally. Which of the following sets of values will most likely be seen at the end of inspiration?

Accepted Answer

Probe A: -6 mm Hg; Probe B: 0 mm Hg

Answer

Probe A: 0 mm Hg; Probe B: -1 mm Hg

Answer

Probe A: -4 mm Hg; Probe B: 0 mm Hg

Answer

Probe A: -4 mm Hg; Probe B: -1 mm Hg

Answer

Probe A: -6 mm Hg; Probe B: -1 mm Hg

Question 8

In which of the following pathological states would the oxygen content of the trachea resemble the oxygen content in the affected alveoli?

Accepted Answer

Pulmonary embolism

Answer

Emphysema

Answer

Exercise

Answer

Pulmonary fibrosis

Answer

Foreign body obstruction distal to the trachea

Question 9

A 19-year-old male soccer player undergoes an exercise tolerance test to measure his maximal oxygen uptake during exercise. Which of the following changes are most likely to occur during exercise?

Accepted Answer

Decreased physiologic dead space

Answer

Increased apical ventilation-perfusion ratio

Answer

Decreased alveolar-arterial oxygen gradient

Answer

Increased arterial partial pressure of oxygen

Answer

Increased pulmonary vascular resistance

Question 10

During a clinical study examining the diffusion of gas between the alveolar compartment and the pulmonary capillary blood, men between the ages of 20 and 50 years are evaluated while they hold a sitting position. After inhaling a water-soluble gas that rapidly combines with hemoglobin, the concentration of the gas in the participant's exhaled air is measured and the diffusion capacity is calculated. Assuming that the concentration of the inhaled gas remains the same, which of the following is most likely to increase the flow of the gas across the alveolar membrane?

Accepted Answer

Treadmill exercise

Answer

Deep exhalation

Answer

Entering a cold chamber

Answer

Standing straight

Answer

Assuming a hunched position

Gas exchange

Study Resources

Lessons

Questions

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Lessons

Oxygen transport in blood

Hemoglobin-oxygen binding

Oxygen-hemoglobin dissociation curve

Bohr effect and rightward shifts

2,3-DPG effects on oxygen affinity

Carbon dioxide transport

Chloride shift mechanism

Ventilation-perfusion matching

Diffusion limitation vs perfusion limitation

Alveolar-arterial oxygen gradient

Hypoxemia mechanisms

Altitude physiology

Diving physiology

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