Ventilation-perfusion ratio concept — MCQs

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?

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?

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?

A 30-year-old patient presents to clinic for pulmonary function testing. With body plethysmography, the patient's functional residual capacity is 3 L, tidal volume is 650 mL, expiratory reserve volume is 1.5 L, total lung capacity is 8 L, and dead space is 150 mL. Respiratory rate is 15 breaths per minute. What is the alveolar ventilation?

A 22-year-old man volunteers for a research study on lung function. He has no history of lung disease or allergies and does not smoke. His pulmonary blood flow is measured in the various labeled segments of the lungs while standing. Then the volunteer, still standing, is given very low continuous positive airway pressure and the blood flow measured again. Which of the following sets of findings are most likely to be present in the second measurements relative to the first?

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

A 72-year-old man with coronary artery disease comes to the emergency department because of chest pain and shortness of breath for the past 3 hours. Troponin levels are elevated and an ECG shows ST-elevations in the precordial leads. Revascularization with percutaneous coronary intervention is performed, and a stent is successfully placed in the left anterior descending artery. Two days later, he complains of worsening shortness of breath. Pulse oximetry on 3L of nasal cannula shows an oxygen saturation of 89%. An x-ray of the chest shows distended pulmonary veins, small horizontal lines at the lung bases, and blunting of the costophrenic angles bilaterally. Which of the following findings would be most likely on a ventilation-perfusion scan of this patient?

A 62-year-old man is brought to the emergency department with a 2-day history of cough productive of yellowish sputum. He has had fever, chills, and worsening shortness of breath over this time. He has a 10-year history of hypertension and hyperlipidemia. He does not drink alcohol or smoke cigarettes. His current medications include atorvastatin, amlodipine, and metoprolol. His temperature is 38.9°C (102.0°F), pulse is 105/min, respirations are 27/min, and blood pressure is 110/70 mm Hg. He appears in mild distress. He has rales over the left lower lung field. The remainder of the examination shows no abnormalities. Leukocyte count is 15,000/mm3 (87% segmented neutrophils). Arterial blood gas analysis on room air shows: pH 7.44 pO2 68 mm Hg pCO2 28 mm Hg HCO3- 24 mEq/L O2 saturation 91% An x-ray of the chest shows a consolidation in the left lower lobe. Asking the patient to lie down in the left lateral decubitus position would most likely result in which of the following?

A 68-year-old man comes to the emergency room with difficulty in breathing. He was diagnosed with severe obstructive lung disease a few years back. He uses his medication but often has to come to the emergency room for intravenous therapy to help him breathe. He was a smoker for 40 years smoking two packs of cigarettes every day. Which of the following best represents the expected changes in his ventilation, perfusion and V/Q ratio?

A 21-year-old man is admitted to the intensive care unit for respiratory failure requiring mechanical ventilation. His minute ventilation is calculated to be 7.0 L/min, and his alveolar ventilation is calculated to be 5.1 L/min. Which of the following is most likely to decrease the difference between minute ventilation and alveolar ventilation?