Question 171
A 31-year-old male is brought to the emergency room by friends because of his difficulty breathing. About 18 hours before his presentation to the emergency room, they reported he had been exposed to a benzene spill at his place of work. While he felt fine after the accident, his current symptoms have developed rapidly over the past 2 hours. Of the following, what is the most likely primary mechanism for his clinical presentation?
A. Insufficient amount of surfactant
B. Necrosis of alveolar epithelial cells
C. Tumor embolism
D. Delayed allergic reaction to the chemical exposure
E. Rapid overgrowth of bacteria
Answer for Question 171
Answer: B (Necrosis of alveolar epithelial cells)
Explanation: Given his rapid onset of shortness of breath within 1 day from a pulmonary chemical exposure, he most likely has acute respiratory distress syndrome (ARDS). Acute respiratory distress syndrome develops due to damage to the alveolar epithelial and/or endothelial cells, which result in leakage of protein-rich fluid into the alveolar airspaces and the resultant formation of hyaline membranes. While a loss of surfactant can occur during the process of ARDS it is not the primary mechanism for the clinical presentation. In hyaline membrane disease in premature infants, a deficiency of surfactant is the primary mechanism for the clinical presentation. While tumor embolism, a delayed allergic reaction to the chemical exposure, or a rapid overgrowth of bacteria could each have the potential for a rapid onset pulmonary-centered clinical process, each of these would be rare compared to the likelihood of ARDS in the above clinical scenario.
Question 172
A 25-year-old male has had a fever and cough productive of a thick yellow-green sputum for one week. He reports occasional sharp chest pain associated with the cough or breathing. Although he felt he had a cold that he could shake, he is now presenting to the emergency room, as over the past 2 hours, he has developed rapidly increasing shortness of breath. His vital signs are blood pressure of 142/83 mmHg, heart rate of 112 bpm, and respiratory rate of 30 bpm. Physical examination reveals no friction rub and the heart sounds do not sound distant. Of the following, which radiographic finding, if not already present, should develop shortly?
A. Bilateral opacities
B. A wedge-shaped opacity in the right lower lobe
C. A widened mediastinum
D. An enlarged cardiac silhouette
E. Diffuse consolidation of the entire lower lobe of the left lung
Answer for Question 172
Answer: A (Bilateral opacities)
Explanation: The patient most likely had a bacterial pneumonia for one week, which could produce fever, a productive cough, and pleuritic chest pain. However, given his rapid change, resulting in progressive dyspnea, tachypnea and tachycardia, he has most likely developed acute respiratory distress syndrome (ARDS). One of the most common causes of ARDS is pneumonia. The characteristic x-ray finding would be bilateral opacities (due to filling of the alveolar airspaces with a mixture of inflammatory cells, and protein-rich edema fluid). ARDS is a diffuse disease process, and thus, the x-ray findings are typically bilateral. A wedged-shaped opacity in the right lower lobe could indicate an infarct due to a pulmonary thromboembolus, which can also present with acute respiratory insufficiency and patients can have a pleuritic chest pain, but he has no risk factors described for a pulmonary thromboembolus (e.g., immobility). A widened mediastinum is consistent with an aortic dissection, and the patient is not described to have hypertension, and the clinical presentation in the week prior is not characteristic for an aortic dissection. An enlarged cardiac silhouette would indicate cardiac hypertrophy or a tamponade. While acute pericarditis can occur in association with pneumonia and could present with increasing shortness of breath, the absence of friction rub and non-distant heart sounds do not support what would already be a relatively rare complication of pneumonia. A diffuse consolidation of the entire lobe of the left lung is consistent with a lobar pneumonia, which he most likely has; however, it would not fully explain the sudden change in clinical status.
Question 173
A 71-year-old male with a 10 year history of Alzheimer’s disease is identified by nursing home staff to have labored breathing. He is taken to the emergency room where a physical examination reveals a blood pressure of 138/81 mmHg, respiratory rate of 29 bpm, and heart rate of 109 bpm. He is admitted to the hospital. Over the next 6 hours, his condition worsens with increasing shortness of breath, and he develops bilateral rales. A chest x-ray reveals bilateral opacities in the pulmonary parenchyma throughout. He has no friction rub, and no S3 or S4 are heard on auscultation of the heart. Microscopic examination of this lungs would reveal which of the following?
A. Proteinaceous exudates layered on the alveolar septa
B. Extensive lymphatic tumor micro-emboli
C. Innumerable microscopic venous thrombi
D. Extensive eosinophilic infiltrates
E. Extensive plasma cell infiltrates
Answer for Question 173
Answer: A (Proteinaceous exudates layered on the alveolar septa)
Explanation: Given the sudden change in his clinical status with rapidly increasing dyspnea associated with tachypnea and tachycardia, acute respiratory distress syndrome (ARDS) is a good possibility. Aspiration is a common cause of ARDS and can easily occur in a patient with long-standing Alzheimer disease. The bilateral opacities are also characteristic of ARDS, which would have been the cause of the rales. Congestive heart failure is in the differential diagnosis for ARDS, and with CHF patients would often have an S3. The characteristic histologic feature of ARDS is hyaline membranes, which are proteinaceous exudates layered on the alveolar septa. While all of the other choices could cause an acute respiratory decline, each would be rare compared to ARDS in the background of aspiration.
Question 174
A 59-year-old male with a 3 year history of increasing shortness of breath presents to his family physician for further testing. He has a 45 pack-year smoking history. The dyspnea is not accompanied by chest pain. He also reports that he frequently coughs up thick sputum, often for months at a time over the past three years. Auscultation of his chest reveals decreased breath sounds and occasional wheezes and crackles. Of the following, which set of parameters is most consistent with his disease process?
Answer for Question 174
Answer: C (Increased TLC (total lung capacity), severely decreased FEV1 (forced expiratory volume), decreased FVC (forced vital capacity), and increased RV (residual volume)).
Explanation: In an older male with a >40 pack-year smoking history, who presents with chronic dyspnea associated with a chronic productive cough, and who has decreased breath sounds on physical examination and occasional wheezes and crackles, the most likely diagnosis is chronic obstructive pulmonary disease. In individuals with COPD, the FEV1 is severely decreased, and the residual volume is increased – the disease process is obstructive, so air cannot be exhaled, and air is trapped. The FVC is usually normal or decreased, and the total lung capacity can be increased, decreased or normal. Importantly, the FEV1/FVC ratio is decreased; in restrictive lung disease, the residual and TLC are decreased and the FEV1/FVC ratio is normal or increased.