It's rush hour in your lungs. Your bronchial highways are packed tightly with bumper-to-bumper congestion, and you're honking and hacking. Every inhalation is a fight for an exit ramp off that breathing bottleneck.   Congestion means different things to different people. Some use the term to describe a tightness in their lungs, as if a wide strap were affixed firmly across the chest, says Richard L. Sheldon, M.D., a pulmonologist and internist at Beaver Medical Clinic in Banning, California. They also may find it difficult to breathe or feel short of breath. If by congestion you mean a tightness in the chest, it's likely that you have asthma. If this is the case, you may notice a dry cough or wheezing as your constricted and swollen bronchial passages try to move air in and out.

Tightness and congestion also could indicate heart trouble. The lungs fill with fluid because the heart isn't pumping properly. Clues to look out for include swollen ankles, shortness of breath, awakening at night with difficulty breathing, chest pain and palpitations (or irregular heartbeat) as well as a history of heart problems.

When other people complain of congestion, "they describe a lot of soupy stuff down there in their lungs," says Dr. Sheldon. "They're usually coughing up a lot of that soupy stuff, too." If you feel as if there's burning in your windpipe or like you're trying to breathe through the froth of a tall glass of root beer, chances are you have some sort of respiratory irritation or infection. Something is harassing your bronchial tubes enough to force them to counterattack by increasing the production of mucus, according to Anne L. Davis, M.D., associate professor of clinical medicine in the Division of Pulmonary and Critical Care Medicine at New York University Medical Center and assistant to the director of chest service at Bellevue Hospital Center in New York City.

An irritant in the air—such as pollution, dust, pollen, smoke or chemicals—may be responsible, says Dr. Davis. If it is, the congestion may be fleeting, leaving soon after you've escaped the irritant. But sometimes there can be a lag time of six to eight hours.

If your congestion is caused by an infection, you'll probably know it, says Charles P. Felton, M.D., chief of pulmonary medicine at Harlem Hospital Center and a clinical professor of medicine at Columbia University College of Physicians and Surgeons in New York City. The phlegm that you cough up will be yellow, green or brown. You'll also have a fever or the chills, and you won't feel very well. The infection could be anything from a mild cold to severe bronchitis or pneumonia, says Dr. Felton. Latent chronic bronchitis or emphysema also could be stirred from its slumber by a milder bug, he says.