A 22-year-old man comes to the office due to an intermittent cough for the past 6 months. He experiences slight wheezing and difficulty breathing, especially in the nighttime and early morning. The patient has no recent history of fever, chills, rigors, sputum production, or upper respiratory tract infections. During a basketball game last week, he had an episode of wheezing for which he went to the emergency department; after 2 nebulizer treatments, the wheezing resolved. He has been otherwise healthy and takes no medications. The patient does not use tobacco, alcohol, or illicit drugs. He has lived in the same house for several years and has no pets. There is no family history of lung disease. Vital signs are within normal limits. Lung examination reveals normal tactile fremitus and percussion on both sides. There are no crackles, wheezing, or other adventitious sounds heard on lung auscultation. Cardiac examination reveals regular heart sounds with no murmurs. The posteroanterior and lateral chest radiographs reveal no abnormalities. What will be the most likely finding on pulmonary function tests?

Question

A 22-year-old man comes to the office due to an intermittent cough for the past 6 months.  He experiences slight wheezing and difficulty breathing, especially in the nighttime and early morning.  The patient has no recent history of fever, chills, rigors, sputum production, or upper respiratory tract infections.  During a basketball game last week, he had an episode of wheezing for which he went to the emergency department; after 2 nebulizer treatments, the wheezing resolved.  He has been otherwise healthy and takes no medications.  The patient does not use tobacco, alcohol, or illicit drugs.  He has lived in the same house for several years and has no pets.  There is no family history of lung disease.  Vital signs are within normal limits.  Lung examination reveals normal tactile fremitus and percussion on both sides.  There are no crackles, wheezing, or other adventitious sounds heard on lung auscultation.  Cardiac examination reveals regular heart sounds with no murmurs.  The posteroanterior and lateral chest radiographs reveal no abnormalities.  What will be the most likely finding on pulmonary function tests?

Quizplus · Accepted Answer

Explanation: This young patient with an intermittent cough and wheezing that worsen on exercise likely has asthma, which is characterized by intermittent, reversible airway obstruction. The diagnosis of asthma is often strongly suggested by clinical presentation but should be confirmed by pulmonary function testing (PFT) (or in-office spirometry). In patients with active symptoms at the time of testing, PFT should reveal the characteristic obstructive pattern consisting of a reduced FEV1 and a reduced FEV1/FVC ratio (total lung capacity and diffusing capacity of the lungs for carbon monoxide [DLCO] are typically normal or sometimes elevated). In these patients, a bronchodilator (eg, albuterol) can be administered and should result in significant improvement in FEV1 (eg, >15% from baseline). In contrast, those without active symptoms at the time of testing (such as this patient) are likely to have normal PFT findings. The administration of methacholine in these patients is likely to cause >20% reduction in FEV1, which is diagnostic of airway hyperresponsiveness. Most patients with asthma have a positive methacholine challenge (high sensitivity), and a negative test is reliable in ruling out asthma (high negative predictive value). A positive test commonly occurs in other disease processes (eg, chronic obstructive pulmonary disease), making the specificity for asthma only moderate. (Choices A and E) The total lung capacity is reduced in restrictive lung disease (eg, interstitial lung disease, obesity hypoventilation syndrome). FEV1 and FVC are both decreased but fairly proportionally; therefore, the FEV1/FVC ratio is normal or increased. (Choice C) Pulmonary arterial hypertension (due to intimal hyperplasia of the pulmonary arteries) causes reduced DLCO due to a combination of impaired blood delivery to the pulmonary capillaries and impaired diffusion of gas across the alveolar-pulmonary capillary membrane. Lung volumes are typically normal. (Choice D) Like asthma, chronic obstructive pulmonary disease demonstrates an obstructive pattern on PFT characterized by a reduced FEV1/FVC ratio. DLCO is also reduced (allowing for diagnostic differentiation from asthma) due to emphysematous destruction of the alveolar-pulmonary capillary membrane. Educational objective: Asthma is characterized by intermittent, reversible airway obstruction. Asymptomatic patients typically demonstrate normal pulmonary function testing, but obstruction (>20% reduction in FEV1) can be provoked by methacholine challenge. References: Diagnostic work-up in patients with possible asthma referred to a university hospital. (http://www.ncbi.nlm.nih.gov/pubmed/26557251)

A 22-Year-Old Man Comes to the Office Due to an Intermittent