Chapter 33

Pulmonology

1 Describe the difference between obstructive and restrictive pulmonary disease on pulmonary function testing

In chronic obstructive pulmonary disease (COPD), the functional expiratory volume in 1 second divided by the total forced vital capacity (FEV₁/FVC) is less than normal (the normal value [0.75 to 0.80] should be given in the question). In restrictive lung disease, FEV₁/FVC is often normal. FEV₁ may be equal in both conditions, but the ratio of FEV₁/FVC is always different.

2 What causes emphysema?

Emphysema is almost always a result of smoking (even second-hand smoke). If you have a young person with minimal smoke exposure (fewer than 5 years), then think of alpha₁-antitrypsin deficiency.

3 How do you recognize and treat asthma?

Watch for chronic wheezing in “allergic” children with a family history of asthma or allergies. In the acute setting, treat with beta₂ agonists. Use steroids if the attack is severe or does not respond to beta₂ agonists. Inhaled glucocorticoids (preferred agent), leukotriene modifiers (zafirlukast, montelukast, zileuton), long-acting beta-agonists, and cromolyn are prophylactic agents and are not used for acute attacks. Phosphodiesterase inhibitors (theophylline, aminophylline) are older agents that are now infrequently used. Do not prescribe beta blockers for asthmatics or patients with COPD; they block the beta₂ receptors that are needed to open the airways.

4 What is the concern with the use of long-acting beta-agonists (LABAs) in the treatment of asthma?

The bottom line is that the United States Federal Drug Administration (FDA) has recommended that LABAs not be used as solo agents in the treatment of asthma in children or adults because of an increased risk of death. The advisory recommends that LABAs not be used alone as initial therapy for asthma of any severity, that they not be added when asthma control is actively deteriorating, that they only be used long-term in patients whose asthma cannot be adequately controlled with other asthma controller medications, and that the LABA be discontinued, if possible, once asthma control is achieved.

5 What is a common cause of wheezing in children younger than age 2 years?

Respiratory syncytial virus (RSV) infection, which classically occurs in the winter and causes a fever. Asthma may also be the cause but usually is associated with a chronic history.

6 What should you think if a patient with acute asthma stops hyperventilating or has a normal carbon dioxide (CO₂) level?

Beware the asthmatic who is no longer hyperventilating or whose CO₂ is normal or rising. The patient should be hyperventilating, which causes low CO₂. If the patient seems calm or sleepy, do not assume that he or she is “okay.” Such patients probably are crashing; they need an immediate arterial blood gas analysis and possible intubation. Fatigue alone is sufficient reason to intubate. Remember also that any patient with COPD may normally live with a higher CO₂ and lower oxygen (O₂) level. Treat the patient, not the laboratory value. If the patient is asymptomatic and talking to you, the laboratory value should not cause panic.

7 When should you intubate?

As a rough rule of thumb, think about intubation in any patient whose CO₂ is greater than 50 mm Hg or whose O₂ is less than 50 mm Hg, especially if the pH in either situation is less than 7.3 while the patient is breathing room air. Usually, unless the patient is crashing rapidly, a trial of oxygen by nasal cannula or face mask is given first. If it does not work or if the patient becomes too tired (use of accessory muscles is a good clue to the work of breathing), intubate. Clinical correlation is always required; patients with chronic lung disease may be asymptomatic at laboratory value levels that seem to defy reason. Alternatively, laboratory values may look great, but if the patient is becoming tired from increased work of breathing, intubation may be needed.

8 What should you do if a patient has a solitary pulmonary nodule on chest radiograph?

The first step is to compare the current film with old films (if available). If the lesion has not changed in more than 2 to 3 years, it is very likely to be benign. A nodule that has increased in size on serial imaging should be biopsied or excised. Computed tomography (CT) scans are used to evaluate and follow a solitary pulmonary nodule. A nodule that has a low probability of being malignant can be followed with serial CT scans. Positron emission tomography (PET) scan is used to evaluate intermediate probability nodules. A nodule that has a high probability of being malignant should be excised.

9 What classic clues point to the cause of a solitary pulmonary nodule?

 Immigrant: Think of tuberculosis; do a skin test.

 Southwest United States exposure: Think of Coccidioides immitis.

 Cave explorer, exposure to bird droppings; Ohio/Mississippi River valleys (Midwest): Think of histoplasmosis.

 Smoker older than age 50 years: Think of lung cancer; order bronchoscopy and biopsy.

 Person younger than 40 years with none of the previous: Think of hamartoma.

10 What should you know about pulmonary function in the setting of surgery?

A baseline chest radiograph is not part of the standard preoperative evaluation, but is often used for patients older than age 60 years or patients with known pulmonary or cardiovascular disease. Preoperative pulmonary function testing is somewhat controversial, and the question probably will not appear on the Step 2 examination. Overall, the best indicator of possible postoperative pulmonary complications is preoperative pulmonary function. The best way to reduce pulmonary complications postoperatively is to stop smoking preoperatively, especially when stopped at least 8 weeks before surgery. Aggressive pulmonary toilet, incentive spirometry, minimal narcotics, and early ambulation help prevent or minimize postoperative pulmonary complications. Lastly, remember that the most common cause of a postoperative fever in the first 24 hours is atelectasis.

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