A 34-year-old woman comes to the physician's office due to worsening shortness of breath over the last 6 months. She can no longer walk a block or climb a flight of stairs without stopping to catch her breath. The patient is occasionally lightheaded when trying to exert herself. An albuterol inhaler prescribed 3 months ago has provided little relief. She does not use tobacco.
Pulse oximetry on room air is 97% at rest and drops to 92% on walking in the office hallway. The patient's BMI is 26 kg/m². Lung examination is normal.
Chest x-ray is unremarkable. Echocardiogram shows moderate right ventricular dilation and hypokinesis with increased flow velocities through the tricuspid valve.
Which of the following is most likely to be seen on pulmonary function testing?
DLCO = diffusing capacity for carbon monoxide; FEV1 = forced expiratory volume in 1 second; FVC = forced vital capacity.

Question

Quizplus · Accepted Answer

11ec193a_98e9_3336_853d_61bd1d6bbccf_MD0002_00 This patient's normal lung examination and right-sided heart failure seen on echocardiography suggest pulmonary hypertension. As there is no evidence of chronic lung disease or left heart failure, this patient likely has pulmonary arterial hypertension (PAH). Spirometry is usually normal in patients with PAH, although a mild to moderate decrease in lung volumes may be seen in some patients with advanced disease. PAH mainly affects the small pulmonary arteries and capillaries. Muscularization of small arteries and medial and intimal thickening of the muscular arteries lead to a decrease in the volume of blood in pulmonary capillaries. Pulmonary hypertension from thromboembolic disease is secondary to a reduction in area of the pulmonary vascular bed. Both mechanisms lead to ventilation-perfusion mismatch, evidenced by the decline in the diffusing lung capacity of carbon monoxide (DLCO) on pulmonary function testing (PFT). This is particularly true of symptomatic PAH. DLCO may be normal in early-stage, asymptomatic PAH (Choice C). (Choice A) Patients with asthma may have airway obstruction (FEV1/FVC <0.70) and a normal DLCO. (Choice D) Abnormal spirometry (low FEV1 and FVC) with obstructive defect (FEV1/FVC <0.70) and reduced DLCO is seen in later stages of COPD (earlier in emphysema). (Choice E) Abnormal spirometry (low FEV1 and FVC) with preserved FEV1/FVC ratio is seen in interstitial lung disease. Educational objective: Pulmonary artery hypertension affects the small pulmonary arteries and capillaries. The resulting ventilation perfusion mismatch leads to a reduced diffusing capacity of carbon monoxide. Spirometry usually remains unaffected. __________ References: Early detection of pulmonary vascular disease in pulmonary arterial hypertension: time to move forward. (http://www.ncbi.nlm.nih.gov/pubmed/21616950) Pulmonary function in primary pulmonary hypertension. (http://www.ncbi.nlm.nih.gov/pubmed/12651053)

A 34-Year-Old Woman Comes to the Physician's Office Due to Worsening