V/Q mismatch Practice Questions

Question 1

A 21-year-old man presents to his physician because he has been feeling increasingly tired and short of breath at work. He has previously had these symptoms but cannot recall the diagnosis he was given. Chart review reveals the following results:

Oxygen tension in inspired air = 150 mmHg
Alveolar carbon dioxide tension = 50 mmHg
Arterial oxygen tension = 71 mmHg
Respiratory exchange ratio = 0.80

Diffusion studies reveal normal diffusion distance. The patient is administered 100% oxygen but the patient's blood oxygen concentration does not improve. Which of the following conditions would best explain this patient's findings?

Accepted Answer

Septal defect since birth

Answer

Use of opioid medications

Answer

Pulmonary fibrosis

Answer

Pulmonary embolism

Answer

Vacation at the top of a mountain

Question 2

A 75-year-old female presents to your office with her daughter. The patient states that she feels perfectly well and that she does not know why she is present. The daughter states that over the last several years, the patient has become forgetful and recently forgot her grandchild's name, along with the groceries she was supposed to buy. She was also found lost 10 miles away from her house last week. The daughter also states that the patient has had urinary incontinence over the last few months and has been seeing little children in the morning that are not present. The patient denies any recent falls. Her vitals are normal and her physical exam does not reveal any focal neurological deficits. Her mini-mental status exam is scored 22/30. What is the most accurate test for this patient?

Accepted Answer

MRI scan of head

Answer

CT angiography of head

Answer

CT scan of head

Answer

Lumbar puncture

Answer

PET scan of head

Question 3

Which mechanism is primarily responsible for the increase in pulmonary diffusing capacity during exercise?

Accepted Answer

Pulmonary capillary recruitment

Answer

Decreased airway resistance

Answer

Reduced membrane thickness

Answer

Increased alveolar ventilation

Question 4

A 78-year-old man is brought in to the emergency department by ambulance after his wife noticed that he began slurring his speech and had developed facial asymmetry during dinner approximately 30 minutes ago. His past medical history is remarkable for hypertension and diabetes. His temperature is 99.1°F (37.3°C), blood pressure is 154/99 mmHg, pulse is 89/min, respirations are 12/min, and oxygen saturation is 98% on room air. Neurologic exam reveals right upper and lower extremity weakness and an asymmetric smile. Which of the following is the next best step in management?

Accepted Answer

CT head

Answer

Alteplase

Answer

MRI brain

Answer

Aspirin

Answer

CTA head

Question 5

A 72-year-old man presents to the emergency department after a fall. The patient was found lying down on the floor in his room in his retirement community. The patient has a past medical history of Alzheimer dementia and a prosthetic valve. His current medications include donepezil and warfarin. His temperature is 97.7°F (36.5°C), blood pressure is 85/50 mmHg, pulse is 160/min, respirations are 13/min, and oxygen saturation is 97% on room air. The patient is started on IV fluids and a type and screen is performed. Laboratory values are ordered as seen below.

Hemoglobin: 13 g/dL
Hematocrit: 39%
Leukocyte count: 5,500 cells/mm^3 with normal differential
Platelet count: 225,000/mm^3

INR: 2.5
AST: 10 U/L
ALT: 12 U/L

A chest radiograph and EKG are performed and are within normal limits. A full physical exam is within normal limits. The patient's vitals are repeated. His temperature is 99.5°F (37.5°C), blood pressure is 110/70 mmHg, pulse is 90/min, respirations are 10/min, and oxygen saturation is 98% on room air. Which of the following is the best next step in management?

Accepted Answer

CT scan

Answer

Urgent blood transfusion

Answer

Fresh frozen plasma

Answer

Exploratory laparoscopy

Answer

Exploratory laparotomy

Question 6

A 24-year-old male is brought in by ambulance to the emergency department after he was found unresponsive at home for an unknown length of time. Upon arrival, he is found to be severely altered and unable to answer questions about his medical history. Based on clinical suspicion, a panel of basic blood tests are obtained including an arterial blood gas, which shows a pH of 7.32, a pCO2 of 70, and a bicarbonate level of 30 mEq/L. Which of the following is most likely the primary disturbance leading to the values found in the ABG?

Accepted Answer

Respiratory acidosis

Answer

Metabolic alkalosis

Answer

Respiratory alkalosis

Answer

Metabolic acidosis

Answer

Mixed alkalosis

Question 7

During heavy exercise, what is the primary mechanism for maintaining arterial pH despite increased lactic acid production?

Accepted Answer

Hyperventilation

Answer

Increased bicarbonate reabsorption

Answer

Phosphate buffering

Answer

Increased hydrogen secretion

Question 8

A 35-year-old man presents to pulmonary function clinic for preoperative evaluation for a right pneumonectomy. His arterial blood gas at room air is as follows:

pH: 7.34
PaCO2: 68 mmHg
PaO2: 56 mmHg
Base excess: +1
O2 saturation: 89%

What underlying condition most likely explains these findings?

Accepted Answer

Chronic obstructive pulmonary disease

Answer

Cystic fibrosis

Answer

Bronchiectasis

Answer

Obesity

Answer

Acute respiratory distress syndrome

Question 9

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 10

Two days after undergoing left hemicolectomy for a colonic mass, a 62-year-old man develops shortness of breath. His temperature is 38.1°C (100.6°F), pulse is 80/min, respirations are 22/min, and blood pressure is 120/78 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 88%. Cardiopulmonary examination shows decreased breath sounds and decreased fremitus at both lung bases. Arterial blood gas analysis on room air shows:
pH 7.35
PaO2 70 mm Hg
PCO2 40 mm Hg
An x-ray of the chest shows a collapse of the bases of both lungs. Which of the following is the most likely underlying mechanism of this patient's hypoxemia?

Accepted Answer

Decreased ratio of ventilated alveoli

Answer

Increased anatomic dead space

Answer

Decreased hemoglobin oxygen-binding capacity

Answer

Decreased chest wall compliance

Answer

Increased tidal volume

V/Q mismatch

Study Resources

Lessons

Questions

Flashcards

Lessons

Ventilation-perfusion ratio concept

Normal V/Q distribution

Alveolar dead space (high V/Q)

Shunt physiology (low V/Q)

Gravity effects on V/Q distribution

V/Q ratio and gas exchange

Hypoxic pulmonary vasoconstriction

V/Q mismatch in COPD

V/Q mismatch in pulmonary embolism

V/Q mismatch in ARDS

V/Q scan principles

Oxygen therapy effects on V/Q mismatch

Ventilator strategies addressing V/Q

Practice Questions

Flashcards

About V/Q mismatch for USMLE

Lessons in V/Q mismatch

Master V/Q mismatch