Cough Diagnosis

  • Diagnosis

    A cough is a sudden and strong release of air from the lungs. It is not an illness, but a protective reflex designed to help you clear foreign material or excess secretions, such as mucus, from your airways.

    Coughs are often categorized based on two characteristics—whether or not they produce or expel mucus, and how long they last. A productive cough is one that produces or expels sputum (also known as mucus or phlegm). Productive coughs help clear and protect the lungs and other parts of the lower respiratory tract from infectious mucus and other potentially harmful agents. Nonproductive, or “dry” coughs, produce little or no sputum; they are usually the result of a minor irritation in the throat.

    A cough can be very brief, lasting just long enough to clear something from your throat. Or it can last for several days, weeks, or even months. An acute cough is one that lasts for less than three weeks. A chronic cough persists for more than three weeks. Acute coughs can become chronic.

    An estimated 14% to 23% of non-smoking adults have a chronic cough, which is why coughing is the fifth most common reason people visit their doctor. Among smokers, the incidence of chronic cough is even higher: Approximately 25% of people who smoke one-half pack per day and 50% who smoke more than two packs per day report having a chronic cough.

    Coughing is an automatic reflex that begins when your body senses that something has entered your airways that shouldn't be there. Nerves called cough receptors, which are located near the surface of the upper and lower passages of the respiratory tract, sense the presence of the unwanted material and send distress signals to your brain. The brain then relays messages to your lungs and respiratory muscles, which force you first to take a deep breath and then to exhale forcefully.

    The force behind a cough occurs because the opening to your windpipe (the glottis), located at the back of your throat, momentarily closes as you exhale. While the glottis is closed, extra pressure builds up in your lungs. Then, when the glottis finally opens, the air explodes out, helping to dislodge particles from your airways.

    Some structures located near the airways, such as the pericardium (the sac that surrounds the heart), the esophagus (swallowing tube), diaphragm (large muscle that brings air in and out of the lungs), and stomach also have receptors that can initiate a cough. If you have GERD, for example, acid from the stomach that creeps up into the esophagus can irritate receptors in the lower esophagus, triggering a cough.

    Coughing can be caused by many different conditions and illnesses Table 01. Bronchitis caused by cigarette smoking is the leading cause of chronic cough. Among non-smokers, coughs are usually the result of an upper respiratory infection (such as acute bronchitis, the common cold, or the flu); postnasal drip, asthma, or gastroesophageal reflux disease (GERD). These conditions are by far the most common causes of chronic cough. Among children, sinus infections (sinusitis) are also a common cause. More serious conditions that may cause cough, such as tuberculosis, are not nearly as common.

    Table 1.  Common Causes of Coughing

    Cause Comments
    Viral infections, such as the common cold, influenza (the flu), croup, and acute bronchitis In non-smokers, viral infections are the most common cause of cough. The excess mucus produced by these infections trigger the cough.
    Postnasal drip Mucus dripping down the back of the throat can lead to a chronic cough. Many acute respiratory illnesses can cause short bouts of postnasal drip. Chronic postnasal drip is usually the result of a sinus infection (sinusitis) or allergies.
    Asthma Asthma causes the airways to become clogged with mucus, which then stimulates coughing. In people with mild asthma, coughing is sometimes the only symptom of the disease.
    Gastroesophageal reflux disease (GERD) When acid from the stomach backs up into the lower esophagus, it can irritate nerve receptors, leading to a persistent dry cough. Less commonly, tiny particles of the acid are aspirated into the lungs, triggering a cough to expel the unwanted substance.
    Smoking Cigarette smoke contains irritants that the lungs try to get rid of through coughing. In addition, prolonged exposure to smoke destroys cilia, the tiny hairlike formations that line the airways and whose job it is to sweep harmful materials from the lungs. Once cilia are destroyed, mucus cannot be expelled normally, which leads to a chronic cough.
    Inhalation of a foreign object If a tiny object or piece of food is accidentally inhaled into the lower respiratory tract, it can trigger a violent cough.
    Stress A cough that disappears during sleep may be caused by stress.
    Allergies Allergies can lead to postnasal drip, which can trigger a chronic cough.
    Bacterial infections, such asbronchiectasis, (the abnormal destruction and widening of the large airways), bacterial pneumonia, pertussis (whooping cough) or sinus infection (sinusitis) The excess mucus produced by these infections trigger the cough. With bacterial infections, the mucus coughed up is often rusty or greenish in color.
    Congestive heart failure A dry, persistent cough is a symptom of congestive heart failure. Often, the cough worsens at night.
    Environmental pollution Breathing in irritants, such as tobacco and other smoke, dust, and noxious fumes can trigger a cough.
    Emphysema A chronic, mild cough is a symptom of emphysema.
    Lung cancer Among non-smokers, a chronic cough is rarely a sign of lung cancer. Coughing can be a symptom of lung cancer among smokers, but most smokers are used to a ?smoker's cough,? and tend not to report it to their doctor.
    Atelectasis (partial lung collapse) A partial lung collapse can be caused by foreign objects or secretions that block the airways, lung disease, or a tumor pressing on a lung. The body then stimulates the coughing reflex in an attempt to clear the airways.
    Certain medications Angiotensin-converting enzyme (ACE) inhibitors and beta-blockers, which are both prescribed to treat high blood pressure, can cause a chronic dry cough in some people who take the drugs.
    Habit Some people cough out of habit or nervousness.
    Emotional or psychological problems More common in children than adults, a psychogenic cough has no apparent physical cause, but is related instead to an underlying emotional or psychological problem.
    Tuberculosis One of the symptoms of this disease is a dry cough that eventually may turn into a productive cough with blood-stained sputum.

    A cough is itself a symptom of an underlying condition or disease. A cough may be the sign of a serious health problem when:

    • blood is being coughed up
    • chest pain accompanies the cough
    • breathing is difficult or short and shallow
    • unintentional weight loss has occurred along with chronic coughing
    • a fever accompanies the cough that lasts more than one day

    If you have any of the above symptoms, you should call your doctor.

    Having one of the many different underlying conditions or diseases that can trigger the cough reflex will raise your risk of developing either an acute or a chronic cough Table 02.

    Table 2.  Clues to Common Causes of Cough

    If... Your cough may be the result of...
    You are a smoker ?Smokers'? bronchitis
    Your cough began after an upper respiratory infection or after exposure to an allergen Postnasal drip
    You have postnasal drip (mucus dripping down the back of the throat, usually due to allergies or sinus infection) Postnasal drip, perhaps caused by asthma
    You have facial or tooth pain Sinus infection (sinusitis)
    You have heartburn or a sour taste in your mouth Gastroesophageal reflux disease (GERD)
    You are taking an ACE inhibitor or beta-blocker for high blood pressure The medication
    You are wheezing Asthma
    You are wheezing at night Asthma or congestive heart failure
    Your cough worsens at work Environmental pollution
    Your cough is producing rust-colored or greenish phlegm Pneumonia
    You have been loosing weight unintentionally Lung cancer or tuberculosis

    In many cases, a cough has more than a single cause.

    Your doctor will begin the diagnosis with a thorough medical history. He or she will ask you questions about your cough and about other symptoms you may be having. Your answers will provide clues as to what might be triggering the cough

    Your doctor will give you a physical exam, during which he or she will use a stethoscope to listen to your lungs. The doctor will also “percuss” your lungs, which involves placing one hand on your chest and thumping it with the fingers of the other hand. The ensuing vibration helps the doctor determine the size and condition of the lungs.

    Your doctor may also wish to obtain an x-ray of your chest and/or your sinuses to check for evidence of pneumonia, sinus infection, or other condition. You may also be asked to give a sample of your sputum so it can be tested in a laboratory for bacterial infection. For this test you will simply be asked to cough deeply and spit sputum into a sterile container.

    Depending on the results of your examination and x-rays, your doctor may order further diagnostic tests. Which particular tests are ordered will depend on what the doctor suspects may be the cause of your cough.

    • Bronchoprovocation. This test, also known as a methacholine inhalation challenge, is used to diagnose asthma. During the test, you will inhale increasing doses of the drug methacholine and then exhale into a mouthpiece while a monitoring device called a spirometer measures your lung function-specifically, how much air is in your lungs and how much you can breathe out in one second. Methacholine usually reduces lung function in people with asthma but not in people who do not have asthma. The test by trained staff with bronchodilator drugs available, should any airflow obstruction be produced.
    • Bronchoscopy. This test is used to diagnose cancer or the presence of a foreign object in the airways. A flexible, pencil-thin tube, called a fiberoptic bronchoscope, is gently inserted into either your nose or mouth and then into the bronchial passages of the lungs. The tube contains a tiny light source and lens, which allows your doctor to see the inner surfaces of the airways. Tiny instruments can also be passed down into the tube to remove material from the airways, including a tissue sample for analysis (an endobronchial biopsy). You will be given a mild sedation before the procedure to relieve anxiety, and a numbing drug, lidocaine, will be sprayed onto the back of your throat and into your lungs to keep you from coughing while the tube is in your airways.
    • Pulmonary function tests. These tests are used to diagnose chronic bronchitis and other lung diseases. They measure how well the lungs can receive, hold, and use air. The tests involve exhaling into a special mouthpiece attached to a monitoring device (spirometer).
    • Barium swallow. This test is used to diagnose gastroesophageal reflux disease (GERD). A barium swallow is an x-ray of the throat and esophagus, the tube connecting the throat to the stomach. For this test, you will drink a cup of barium, a thick, chalky fluid that can be seen on x-rays. A radiologist will use a video x-ray machine to follow the barium as it passes through your digestive system. If the barium moves from the stomach back into the esophagus, you may have GERD.
    • pH probe. With this test, which is also used to diagnose gastroesophageal reflux disease, a small tube with a sensor that measures acidity is inserted through the nose and down into the end of the esophagus. The tube is then connected to a recording device that is worn at the waist. Insertion of the tube takes about 15 minutes. You will then be sent home and told to go about your normal activities. After 12 to 24 hours, you will return to your doctor’s office to have the tube removed and the recordings analyzed for signs of acid reflux.
    • Magnetic resonance imaging (MRI). This test, which uses a magnetic field to take images of the body’s internal organs, helps physicians diagnose a host of diseases and conditions, including those affecting the lungs. For the test, you will be placed inside a large donut-shaped machine. To ensure that you remain still for the test, which can take 30 minutes or longer, you will be sedated or given anesthesia.
    • Computed tomography (CT). This test, which is sometimes called a CAT scan, takes x-ray pictures of slices of the body to produce a cross section of body tissues and organs. For the test, you will lie down on a special scanning table as the donut-shaped scanner rotates around you. The procedure, which is painless, usually takes no longer than half an hour.

    You can prevent a cough by preventing the underlying conditions and diseases that can trigger the cough reflex.

    • To prevent viral infections: Wash your hands frequently. Build up your immune system by eating well; engage in regular, moderate exercise, drink plenty of water, and do not smoke.
    • To prevent gastroesophageal reflux disease: Maintain a reasonable weight. Try eating smaller, more frequent meals. Avoid foods that cause stomach acid to back up into your esophagus, such as tomatoes, citrus fruits, chocolate, coffee, alcohol, and peppermint. Do not lie down after meals.
    • To prevent sinus infections: If you have allergies, try to avoid contact with substances that cause allergy attacks. Avoid cigarette smoke and other air pollutants, which can also irritate sinus passages. Wash your hands frequently to avoid respiratory infections such as the common cold and flu, which can lead to sinus infections.
    • To prevent bronchitis: Don't smoke. Also, limit your exposure to potentially damaging chemical irritants, including indoor pollutants such as aerosol deodorants, insecticides, and hair sprays.

  • Prevention and Screening

    You can prevent a cough by preventing the underlying conditions and diseases that can trigger the cough reflex.

    • To prevent viral infections: Wash your hands frequently. Build up your immune system by eating well; engage in regular, moderate exercise, drink plenty of water, and do not smoke.
    • To prevent gastroesophageal reflux disease: Maintain a reasonable weight. Try eating smaller, more frequent meals. Avoid foods that cause stomach acid to back up into your esophagus, such as tomatoes, citrus fruits, chocolate, coffee, alcohol, and peppermint. Do not lie down after meals.
    • To prevent sinus infections: If you have allergies, try to avoid contact with substances that cause allergy attacks. Avoid cigarette smoke and other air pollutants, which can also irritate sinus passages. Wash your hands frequently to avoid respiratory infections such as the common cold and flu, which can lead to sinus infections.
    • To prevent bronchitis: Don't smoke. Also, limit your exposure to potentially damaging chemical irritants, including indoor pollutants such as aerosol deodorants, insecticides, and hair sprays.

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