Understanding the Human Cough
Earlier today, I walked by my waiting room and heard a chorus of coughing. Yes, it's the season for respiratory illness: the common cold, bronchitis, sinusitis, croup, pneumonia, and influenza. Among all the common symptoms of respiratory illness, cough is probably the most annoying and feared among patients. There are several different aspects of cough, including function, characteristics among different illnesses, "red flags" for concern, and treatment.
In short, cough is one of our body's mechanisms of defense. It's a reflexive response to something in the respiratory tract that shouldn't be there. This may simply be a piece of food that "went down the wrong tube," or it could be a mucous buildup in response to an infection. The mucous traps debris and infectious particles (bacteria or viruses), and the cough removes them from the body. Occasionally, the cough occurs due to patches of inflammation and swelling along the respiratory tree.
Different qualities and associations with a cough can offer clues as to the the cause of an illness. Cough is often described as productive or non-productive (whether or not mucous comes up with the cough). Further, the color of the mucous is often qualified as clear, yellow, green and the consistency as thick or thin.
Really, with infection, mucous quality is not so telling, save one exception. Rust-colored mucous coughed up should raise suspicion for pneumonia caused by the bacteria pneumococcus. The rust color comes from microscopic blood.
While the color or quality of the mucous isn't much help in determining a cause, the sound of the cough can give important information. The following are common examples of characteristic coughs:
- "Barking seal" cough with stridor (whistling inspiration) in a child: think croup
- Accented cough, coming in attacks that gives the appearance of choking followed by a "whooping" inspiration: think pertussis (whooping cough)
- "Brassy" cough with musical breathing (wheezing): think RSV (respiratory syncytial virus) bronchiolitis or asthma
A Mere Annoyance or Reason for Worry?
For most, cough is merely an annoyance and will resolve on it's own. Certain "red flags" do exist, however, which could signal something more serious. As stated earlier, rust-colored mucous associated with illness should raise concern for pneumonia. Cough associated with difficulty breathing requires treatment, whether it is croup, whooping cough, RSV, asthma, or another cause. Coughing up blood also requires further investigation to rule out cancer or tuberculosis.
Incessant coughing may or may not warrant concern. With illness, such as a cold, symptoms typically resolve after 7-10 days. Occasionally, a "post-bronchitic" cough persists as an unwanted remnant. This all-too-common consequence of bronchial irritation occurs when the cold leaves irritation from nasal drainage. Breathing in, this creates a tickle or a catch and a responsive cough. The cough irritates this area in the back of the throat and the vicious cycle ensues. This cough can persists for weeks or months after a respiratory illness.
Cough that persists, however, and is not related to a cold or other respiratory illness, should be further investigated. Causes can vary widely from a side effect of medication (commonly a blood pressure medication called an ACE-inhibitor) to undiagnosed asthma or allergies to cancer.
The main reason to treat a cough is to break a cycle. Beyond the annoyance, cough can interrupt sleep significantly, which decreases quality of life, and prolong healing of the causal illness. With post-bronchitic cough, stopping the cough for a period of a few days allows the bronchial tissue to heal, halting the cycle of cough.
Cough that is a symptom of more significant illness should not be treated without addressing the cause. While a number of over-the-counter medications are available to treat cough in adults, the most effective remedy is considered to be codeine, a prescription narcotic. With children, OTC medications have been discontinued for the most part. Before this time, however, buckwheat honey was shown to be equally effective and a much safer option for children over the age of one.
Cough is a common complaint with many different causes. The most discerning quality and association of cough is its characteristic sound. Certain "red flag" symptoms such as persistence, presence of blood, or association with difficulty in breathing should prompt medical investigation.