Sputum Analysis

Examining sputum to aid in diagnosis began in classical times with the physicians of Greece and Rome. Galen (A.D. 130-201), the foremost Roman physician during the reign of Marcus Aurelius, described using sputum analysis specifically to diagnose respiratory diseases. Sputum analysis is still an important aid in evaluating patients.

Because abnormal airway secretions tend to collect during sleep, the best time to take a coughed-up sputum specimen is shortly after waking. The ideal preparation is first rinsing your mouth and gargling with an antiseptic to prevent bacteria in your throat and mouth from contaminating your airway secretions. Because mucus cells disintegrate quickly, the specimen should be brought to your doctoror the laboratory he usespromptly for examination.

The examination will include sputum color and consistency. In stable bronchitis, mucus is translucent (clear), thick, and sticky. During a respiratory infection, the mucus increases greatly in quantity and becomes opaque and yellow. When color indicates an infection, the bacteria will be cultured and identified so the most effective antibiotic can be prescribed.

Other Tests

Two other tests are sometimes used to assess a COPD patient's condition. One is an exercise test. The otheras far from exercise as you can getis a sleep study. Let's look at each one in some detail.

Exercise Test: This is commonly called a "stress test." But don't let the name frighten you! A stress test is not designed to overwork or exhaust you, but simply to determine the level of physical activity you can comfortablyand safelycarry out, and how long you can comfortably and safelydo it.

Normally, a person's heart limits the amount of strenuous work he can do and the exercise test identifies this heart-determined limit. COPD has changed that. These patients are limited by their respiratory system. Here, the exercise test is used to identify this limit, and see how it may be safely extended.

First, the exercise test shows how debilitated new patients are. They can measure exactly how hard the patients are breathing and how hard their hearts are working at the point they become uncomfortably short of breath. By comparing this with their pulmonary function test results, they know how much of their dyspnea is due to inalterable respiratory limitation, and how much to simply being out of shape. Then they can plan an appropriate reconditioning program. During this reconditioning program, a repeat exercise test every so often tells themand the patienthow well he is doing.

They can also see if a patient who has normal blood gases (that is, adequate oxygen and carbon dioxide levels) at rest becomes underoxygenated during exercise. These patients, and those whose oxygen level is always low, return for a second exercise test. Then they see if breathing supplemental oxygen during this test extends their exercise time. (Research shows that oxygen can improve exercise performance and lengthen lifespan in COPD patients with low oxygen in their blood.) If it does, then they know that supplemental oxygen is important in this patient's treatment program.

The test itself is usually done on a treadmill or a bicycle ergometer. If you undergo an exercise test, both your heart rate and oxygen saturation (how much of your blood actually contains oxygen, compared to how much should be carrying oxygen) are continuously measured.

Polysomnography: A sleep test (called polysomnography) determines whether a patient needs supplemental oxygen at night. Oxygen in arterial blood can drop during sleep. It happens in some presumably healthy peopleand it eventually happens in everyone with COPD.

There are two reasons. The greatest drop occurs during sleep's dream stage (called REM sleep, for the rapid eye movements that occur during dreams). Intercostal muscle activity normally decreases during this time, and the COPD patient's ineffective diaphragm can't, working alone, maintain adequate ventilation. Another cause is the greater accumulation of airway secretions during sleep because coughing is infrequent then. (Patients who are voluminous mucus producers are particularly vulnerable to small airway obstruction during sleep.) Both these mechanisms decrease sleep oxygenation indirectly as well, because they result in a mismatch of ventilation and blood flow in the air sacs.

At the End

Arriving at the formal diagnosis of COPD takes all the above kinds of information into account to determine (1) the predominant nature of the patient's airway obstruction, that is, is it primarily chronic bronchitis or emphysema, and (2) its severity, for example, is the obstruction somewhat reversible, and is the heart already involved. Some patients, though, do not fall into a neat category. Then physicians must add the fruits of their experience and intuition to complete the picture.