A 62-year-old man comes to the office due to shortness of breath. His symptoms have progressed over the last few months and have begun to limit his daily activities. He has no other medical problems and takes no medications. The patient drinks 3 or 4 alcoholic beverages a week and has a 50-pack-year smoking history. Physical examination reveals decreased breath sounds and scattered wheezes bilaterally. Chest x-ray is shown below. Which of the following parameters is most likely to be increased in this patient?

Question

A 62-year-old man comes to the office due to shortness of breath.  His symptoms have progressed over the last few months and have begun to limit his daily activities.  He has no other medical problems and takes no medications.  The patient drinks 3 or 4 alcoholic beverages a week and has a 50-pack-year smoking history.  Physical examination reveals decreased breath sounds and scattered wheezes bilaterally.  Chest x-ray is shown below.  Which of the following parameters is most likely to be increased in this patient?

Quizplus · Accepted Answer

11ec160b_3b33_1f82_9249_e1c0ddcd0eb5_MD0001_00 This patient's chest x-ray reveals hyperinflated lungs and a flattened diaphragm (compared to normal), consistent with chronic obstructive pulmonary disease (COPD). COPD involves components of chronic bronchitis and emphysema, both of which contribute to air-trapping and hyperinflation. The outward expanding pressure created by the chest wall and the inward collapsing pressure created by the lungs are in equilibrium at the functional residual capacity (FRC). In patients with COPD, decreased elasticity of the alveoli (from emphysema) results in decreased collapsing pressure created by the lungs to expel air. Bronchial airway thickening and obstruction (from chronic bronchitis) further impairs lung collapse by impeding the expulsion of air. The decrease in collapsing pressure causes the chest wall to expand outward until the expanding pressure of the chest is balanced by the collapsing pressure of the lungs. A new pressure equilibrium is reached at a higher lung volume (ie, higher FRC) and, as a result, residual volume and total lung capacity are also increased. (Choice A) The diffusing capacity of the lung for carbon monoxide (DLCO) largely depends on the thickness and total surface area of the alveolar capillary membrane. In emphysema, interalveolar wall destruction decreases the alveolar-capillary surface area, reducing DLCO. Patients with emphysema may have decreased DLCO even when there is little evidence of expiratory airflow obstruction on spirometry. (Choice B) Expiratory airflow rates are reduced in COPD due to inflammatory and fibrotic narrowing of the bronchi (chronic bronchitis) and decreased alveolar elastic recoil (emphysema). (Choice C) In COPD, forced vital capacity is usually decreased due to expiratory airflow obstruction limiting the total expiratory volume. (Choice E) Emphysema causes lung elastic recoil to decrease secondary to destruction of interalveolar walls. Educational objective: Chronic obstructive pulmonary disease involves components of chronic bronchitis and emphysema. Bronchial airway obstruction from chronic bronchitis and decreased alveolar elasticity from emphysema result in air-trapping and lung hyperinflation. The functional residual capacity is increased, as are residual volume and total lung capacity. __________ References: Why does the lung hyperinflate? (http://www.ncbi.nlm.nih.gov/pubmed/16565428)

A 62-Year-Old Man Comes to the Office Due to Shortness