Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
A 67-year-old man is evaluated for a 6-month history of worsening exertional dyspnea. He has a history of severe COPD diagnosed 4 years ago and previously had minimal exertional symptoms. However, he now notes shortness of breath when walking short distances that is limiting his activity level. He does not have chest pain, gastrointestinal symptoms, or sleep-related symptoms. Medical history is otherwise unremarkable. Medications are a twice-daily fluticasone/salmeterol inhaler and an as-needed albuterol/ipratropium metered-dose inhaler. He has a 55-pack-year smoking history but stopped smoking at the time of his COPD diagnosis.
On physical examination, temperature is 37.0 °C (98.6 °F), blood pressure is 130/84 mm Hg, pulse rate is 82/min, and respiration rate is 16/min; BMI is 24. Oxygen saturation breathing ambient air is 93%. Jugular venous distention is noted. Pulmonary examination reveals distant breath sounds and no wheezes. Cardiac examination discloses an accentuated S2 and regular rhythm. Abdominal examination is unremarkable, and there is bilateral lower extremity edema to the level of the ankles.
A chest radiograph shows hyperinflation, prominent central pulmonary arteries, and no infiltrates. A transthoracic echocardiogram shows normal left ventricular size and function with an ejection fraction of 60% and a right ventricular systolic pressure of 52 mm Hg.
Which of the following is the most appropriate diagnostic test to perform next?
A. High-resolution CT
B. Oxygen measurement during sleep and exertion
C. Polysomnography
D. Right heart catheterization for pressure measurement
MKSAP Answer and Critique
The correct answer is B: Oxygen measurement during sleep and exertion.
The most appropriate diagnostic test to perform next is an oxygen measurement during sleep and exertion. This patient with underlying lung disease has a 6-month history of exertional dyspnea with evidence of pulmonary hypertension (PH) on physical examination and echocardiography. In this setting, PH is most commonly the result of chronic hypoxia causing diffuse pulmonic vasoconstriction; if untreated, this may result in vascular remodeling and sustained PH. Treatment of this form of PH due to underlying lung disease (group 3 classification) focuses on treatment of the underlying lung disease and specifically addressing hypoxia, if present. Although this patient’s resting oxygen saturation is within the low-normal range, he may be experiencing sustained hypoxia while asleep or with periods of increased oxygen demand, such as exercise. Therefore, measurement of oxygen saturation with sleep (overnight pulse oximetry) and with exertion (such as with a 6-minute walk test) may determine the need for oxygen therapy in this patient.
High-resolution CT (HRCT) scanning provides detailed information about the lung parenchyma and is particularly valuable for evaluating suspected diffuse parenchymal lung diseases. However, this patient has documented COPD without evidence of another underlying lung process. Therefore, HRCT would not be expected to provide additional useful clinical information in this patient.
There is little evidence in this patient’s clinical history to suggest sleep-disordered breathing, and he is not overweight. Therefore, polysomnography is not immediately indicated as a next step in evaluation.
Right heart catheterization is typically used to evaluate PH of unclear cause, and it is generally not necessary when PH is believed to be related to underlying lung disease. In addition, right heart catheterization would not effectively assess the status of the underlying lung disease or the need for supplemental oxygen.
Key Point
- Oxygen measurement during sleep (overnight pulse oximetry) and exertion (such as with a 6-minute walk test) may determine the need for oxygen therapy in patients with pulmonary hypertension due to underlying lung disease (group 3 classification).
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