Cough Case 3

A 60-year-old man presents to the emergency department complaining of shortness of breath, cough, and copious sputum production. He states that he has been coughing for years, and has had increased sputum production for several months each year. On examination, he is
obese, afebrile, cyanotic, and in acute distress. Coarse rales are auscultated bilaterally at the lung bases. He smokes two packs of cigarettes a day and has a seventy-five pack-year smoking history. A chest x-ray film appears normal, except for slightly enlarged lung fields.

Q 1

Which of the following is the most likely diagnosis?
/ A. Chronic bronchitis
/ B. Emphysema
/ C. Myocardial infarction
/ D. Pneumonia
/ E. Pulmonary embolus

Q 2
As this patient waits in the emergency department, his condition begins to deteriorate. He turns increasingly blue and an arterial blood gas is drawn. His PO2 is 45 mm Hg, which under normal conditions means that his hemoglobin would be 75% saturated. Which of the following
mechanisms could cause a hemoglobin saturation of less than 75% at this pO2?
/ A. Decreased 2,3-DPG Ievels
/ B. Decreased hemoglobin
/ C. Decrease in body temperature
/ D. Decreased PCO2
/ E. Decreased serum pH

Q 3
Why must care be exercised when administering O2 to this patient?
/ A. Administering O2 washes out alveolar CO2 and inhibits respiration
/ B. Chronic hypoxia alters the blood-brain barrier such that CO2 cannot diffuse into the medullary apneustic center
/ C. Chronic hypoxia induces atrophy in the dorsal respiratory group in the medulla
/ D. Increased PO2 worsens CO2 retention by decreasing respiratory drive
/ E. O2 is acutely toxic to the chronically hypoxic alveolar epithelium

Q 4
The mucus seen in this patient is derived from which of the following cell types?
/ A. Alveolar macrophages
/ B. Goblet cells
/ C. Neuroendocrine cells
/ D. Type l pneumocyte
/ E. Type ll pneumocyte

Q 5
Which of the following spirometry profiles would most likely be seen in this patient?
/ A. Decreased TLC, decreased FEV1
/ B. Decreased TLC, decreased RV
/ C. Decreased TLC, increased FEV1
/ D. EIevated TLC, decreased FEV1
/ E. NormaI TLC, decreased FEV1

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Cough Case 3 Answers


A1
The correct answer is A. This patient has findings classic for the "blue bloater" of chronic bronchitis. Patients with chronic bronchitis have excessive tracheobronchial mucus production sufficient to cause cough with expectoration for at least three months of the year for more than two consecutive years. "Blue bloaters" are named for their obese body habitus, copious sputum production, and cyanotic episodes. This condition may occur initially without airway obstruction, but eventually, most patients progress to obstructive disease.
Patients with emphysema (choice B) represent another form of COPD. They are known as "pink puffers" because they do not become cyanotic until they decompensate. They display a thin body habitus and belabored breathing. This patient is not consistent with the pink puffer of emphysema.
This patient does not have the classic findings for myocardial infarction (choice C), which include: chest pressure or pain, shortness of breath, and/or pain that radiates to the jaw or left arm.
It is unlikely that this patient has pneumonia (choice D). Patients with pneumonia have cough with purulent sputum production, but they are usually febrile and have chest x-ray opacities.
While the diagnosis of pulmonary embolus (choice E) is elusive due to its varied presentations, it is unlikely that this patient has a pulmonary embolus. Findings for PE include pleuritic chest pain, shortness of breath, hemoptysis, and a history of calf pain indicative of deep vein thrombosis.

A2
The correct answer is E. A decrease in pH (an increase in H+ concentration) decreases the affinity of hemoglobin for O2. This facilitates unloading of oxygen from hemoglobin to the tissues. Choices A, C, and D increase the affinity of hemoglobin for O2, and thus cause the Hb to retain the O2.
Choice B is a distracter

A3
The correct answer is D. In a patient with normal respiratory function, the PCO2 and pH of cerebrospinal fluid drives the respiratory center in the medulla oblongata. As serum PCO2 rises, increased CO2 diffuses across the blood-brain barrier. When this CO2 is buffered with the high HCO3- of cerebral spinal fluid, the concentration of H+ rises accordingly. The chemosensitive cells in the medulla's respiratory center respond to this localized decrease in pH by stimulating ventilation. The pH in the CSF returns to nearly normal, more quickly than the renal compensation of the arterial pH, which takes 2-3 days. Patients with chronic CO2 retention will have an abnormally low ventilation for their PCO2 because the pH of their CSF is nearly normal. Therefore, in patients with chronic CO2 retention, arterial hypoxemia becomes their primary ventilatory stimulus. When the patient is given supplemental O2, the PO2 rises, and the hypoxic stimulation disappears, and respiration can become markedly depressed. The PCO2-dependent respiratory drive does not revert immediately, and thus the patient hypoventilates and retains CO2, which may precipitate coma, stupor, or death.
Administering O2 at high flow rates (choice A) may wash out alveolar CO2, but this is not the mechanism for hypoventilation of the chronically hypoxic patient.
Chronic hypoxia does not alter the diffusing capacity of the BBB (choice B).
Chronic hypoxia does not cause the respiratory center to atrophy (choice C).
Chronically high O2 concentrations can damage the alveolar epithelium, but in the acute setting, it does not alter its diffusion capabilities (choice E).

A4
The correct answer is B. In chronic bronchitis, goblet cell hyperplasia is seen in the airways. This hyperplasia, caused by chronic irritation (usually by tobacco smoke), results in increased mucus secretion and formation of mucus plugs. These mucus plugs obstruct the airways, and are responsible for part of the obstructive component of chronic bronchitis. Some degree of loss of elastic recoil of the airways is also seen and further adds to the obstructive component of the disease.
Alveolar macrophages (choice A) do not secrete mucus. They have a phagocytic function.
Neuroendocrine cells (choice C) are present in the respiratory tract. They are the cell of origin for oat cell carcinomas, and the neuroendocrine capabilities of these cells become evident with the paraneoplastic syndromes seen in this high-grade carcinoma.
Type I pneumocytes (choice D) comprise the majority of alveolar epithelium. They provide the majority of the surface area on which gas exchange occurs.
Type II pneumocytes (choice E) secrete the alveolar surfactant that allows alveoli of different diameters to inflate at the same pressure.

A5
The correct answer is E. Patients with chronic bronchitis tend to have normal TLC and decreased FEV1. Patients with chronic bronchitis do not typically have the increased TLC that their counterparts with emphysema have. They may however, have a modestly increased residual volume due to air trapping distal to mucus plugs. Similarly these mucus plugs obstruct the airways, creating the obstructive component of chronic bronchitis. Hence a decreased FEV1 is noted.
Choices A and B are not typical of any common pulmonary disorder.
Choice C is consistent with restrictive lung disease. The increased fibroelastic elements in the lung parenchyma decrease the lung capacity, while allowing the airways to remain open at increasingly lower pressures. Thus, a decreased TLC is seen with an increased FEV1.
Choice D is consistent with emphysema. These patients have destruction of the fibroelastic elements of the lung. As a result, the TLC increases. With decreased elastic tissue, the airways collapse at higher airway pressures, and a decreased FEV1 is seen.