The bloodstream transports gases throughout the body. Blood is pumped into the lungs, where it deposits carbon dioxide, a waste product, and receives oxygen. The fine balance and control between the heart and lungs prevents shortness of breath even when you exercise. Shortness of breath (dyspnea) that occurs at rest or with little exercise can be acute or chronic, but in either case it is caused by diseases of the heart or lungs, or both. Occasionally, illnesses such as anemia or excess thyroid hormone (hyperthyroidism) tax the heart so that it must work overtime. The result is shortness of breath.
Sudden breathlessness can occur without warning, and it can be frightening. You may feel that you are choking because you are unable to catch your breath. Depending on the cause, there may also be pain in the chest, cough, heart palpitations, dizziness, light-headedness, and mental confusion.
One of the common causes of sudden breathlessness is heart failure. Acute heart failure, or pulmonary edema, means that the pumping action of the heart suddenly becomes impaired. Instead of the heart being able to effectively pump the blood that has been brought to it, the blood backs up and collects in the lungs, thereby interfering with the exchange of oxygen and carbon dioxide.
The common causes of acute heart failure are heart attacks (myocardial infarction), a sudden irregularity of the heart rhythm (cardiac arrhythmia), or conditions that suddenly overtax the heart, such as severe anemia, hyperthyroidism, or a pulmonary embolism. Immediate emergency-room care and hospitalization are required for heart failure. Medications such as diuretics, morphine, and digoxin are used because they drain the fluid from the lungs and improve the efficiency of the heart’s pumping action. An electrocardiogram, chest X-ray, and blood tests may be necessary to find the exact cause and best treatment for this condition.
Even though the pulmonary (lung) causes of sudden breathlessness can be as dramatic as the cardiac (heart) causes, in most cases lung causes are more gradual, even during an acute situation.
A collapsed lung (pneumothorax) can also cause sudden breathlessness. In this situation one of the small air sacs in the lung ruptures, and air rushes out of the lung and into the pleural space between the lung and the chest wall. The lung loses air and collapses. Sometimes there is sudden pain with the episode. Chronic bronchitis and emphysema are often responsible for a collapsed lung. Immediate medical attention is required to allow the lung to reexpand.
Other common respiratory causes of sudden breathlessness are infections such as acute bronchitis or pneumonia. You may not know that you have these diseases until an attack of acute breathlessness occurs. You may have had a recent cold or flu with some cough, phlegm, or fever. Sometimes a rapid progression of symptoms occurs within a few hours and you may become short of breath. The most important clue to a lung infection is coughing and yellowish or green phlegm.
Another condition that causes shortness of breath is a pulmonary embolism. A blood clot (thrombus) forms either in the veins of the legs or pelvis and makes its way to the heart and lungs. The clot blocks the blood flow from the heart to the lungs and interferes with breathing. Other symptoms can be chest pain and coughing up blood. This is a medical emergency that requires hospitalization and rapid treatment with anticoagulants (blood thinners) to prevent further blood clots from forming. Very rarely, emergency surgery is done to remove the blood clot from the lungs.
You are most at risk for pulmonary embolism if you have had surgery or have suffered from a severe illness that has required prolonged bed rest. Operations and fractures, especially when occurring after an accident, pose the greatest danger. However, there is a good chance for a complete recovery. I treated a spry 93-year-old woman who had fractured her hip. She agreed to hip surgery and was doing well until three days after the operation, when she suddenly developed severe pain in her chest and became short of breath. She was diagnosed as having pulmonary embolism. Despite her age, she made an excellent recovery. Three years later, she is still an active, involved, and very independent woman.
A number of less common events can cause sudden breathlessness. In some, following an inflammatory illness or viral infection, the lungs accumulate excess scar tissue. The body tries to counteract the inflammation and produces a jellylike material which fills the lungs and interferes with their proper function.
Inhaling a noxious material during a fire or breathing some chemical that may inflame the lung can also cause sudden breathlessness.
In most cases of sudden breathlessness, hospitalization is required for proper investigation and treatment. First-aid measures by a physician or in an emergency room can be life-saving, such as expelling the air from the chest in a case of pneumothorax, improving the severe fluid congestion in heart failure, or giving oxygen after removing a person from a smoke-filled room. Most of these conditions respond to treatment, but urgent medical attention improves the chances of recovery.
Unlike the sudden causes of shortness of breath, the chronic causes may be gradual and therefore more insidious. It may take many days, weeks, or months before you are aware that you no longer can undertake your normal activities because of shortness of breath.
If you have heart disease, you may discover that you pant after exertion. You might feel short of breath lying in bed, especially when you lie flat, and find that raising the head of your bed or using more pillows makes you comfortable. Sometimes you become breathless only in the middle of the night. Getting up and walking around sometimes helps. You may begin to notice that your legs swell, which is usually worse at the end of the day. This edema can be so gradual that you may not be aware of it.
If you have not had a heart attack or rheumatic fever, you may not be aware that you have heart disease. Some people know only that they had high blood pressure for many years before the symptoms of chronic heart failure show up. If you begin to experience these symptoms, heart failure might be diagnosed. Your physician will usually do a number of tests, including a chest X-ray, an electrocardiogram, and blood tests. Treatment, often with a combination of medications, is usually successful.
Like chronic heart failure, chronic pulmonary breath-lessness progresses gradually, often occurring with a cough, excessive phlegm, or wheezing. Sometimes there are no symptoms other than the awareness that physical activity has become more difficult.
Shortness of breath from lung disease is more common if you smoke. This is by far the most common cause of chronic respiratory disease. Unfortunately, many people continue to smoke even though they know the connection between smoking and their symptoms. You may have had wheezing and coughing for many years, or other symptoms that signify the development of chronic bronchitis and emphysema.
Exposure to lung irritants from work, such as occurs in miners, grain handlers, and people who worked in dusty atmospheres for many years or with irritant chemicals can also cause chronic lung disease and chronic breathlessness. Your work history should be given to your doctor when you discuss your history and respiratory symptoms.
As in heart failure, with pulmonary disease you may notice some swelling in your legs, especially if the disease is severe. You may learn to partially close your lips as you walk which makes breathing seem easier, and notice your hands tend to be gray or blue. You may have little tolerance for cold weather, which often aggravates breathlessness. Tests for these symptoms include a chest X-ray, an electrocardiogram, and pulmonary function tests, which allow the physician to determine the cause and extent of the lung damage and measure the response to treatment.
On rare occasions your physician may recommend a lung biopsy, in which a small piece of lung tissue is removed and examined under a microscope. This facilitates a diagnosis that may have been difficult to determine by other means.
Another condition that causes breathing difficulty is pleural effusion (an accumulation of fluid between the lung and chest wall). Often, the physician can remove this fluid to relieve symptoms and diagnose the reason for its accumulation. The causes include heart failure, infections, inflammatory diseases, and tumors. Thoracentesis (removal of fluid) is usually painless and has very little risk.
Occasionally, a pleural biopsy may be necessary, in which a needle is inserted to remove a small piece of the pleura (lining of the chest wall). This is simpler than a lung biopsy, and it helps to clarify the cause of fluid accumulation.
Most people with chronic lung disease causing breathlessness can be helped if medical advice is followed. Stopping smoking is the single most important step you can take.
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