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A cough may be a good thing or a bad thing. Mostly, it's a good thing. It alerts your nervous system, both consciously and subconsciously, that some problem is in the respiratory airways that shouldn't be there. This is not the case where someone has a psychogenic problem where they cough when they feel nervous, stressed or threatened. It is a signal and a reflex that something is there that threatens the integrity of the airways. It could be viruses or germs, cigarette smoke, dust, second-hand smoke, air pollution, small particulate matter or a green pea that slipped by the epiglottis. The epiglottis is a covering flap muscular and cartilage structure that keeps anything but air from entering the trachea when you swallow food.
The most common causes of persistent cough in 9 out of 10 cases are post-nasal drip. Acid refluxed up to the trachea from the stomach (called "GERD"), and asthma are other additional cases. The other 10% can include bacteria and viruses, certain medication like ACE inhibitors, and chronic lung disease.
The cough reflex itself is mediated by the vagus nerve. It can receive signals from the airway surfaces or stretch receptors in the lungs. The cough reflex starts with a deep inspiration of air. Then the diaphragm contracts strongly to expel the air, but the epiglottis is closed by the reflex. This closure causes a significant pressure rise in the chest. The epiglottis then opens abruptly and allows the air to violently exit. It works wonderfully to remove phlegm, debris, mucus, a fungus or fluid from the airways. It is a vital defense mechanism to remove infection and foreign bodies. If nothing consequential is there, the cough may be dry and is said to be "non-productive."
When doctors talk about a cough, they may describe it in one of three ways. If it has been present less than three weeks, they refer to it as acute. Again this could be caused by bacteria or viruses causing an upper respiratory infection, dust or foreign substances or bronchitis. The second way they prescribe it is as sub acute. This might be caused by an infection that hangs on a little longer, by post-nasal drip, or by something that made somebody's GERD worse. The third way to describe it can be as chronic, which is a cough that lasts longer than eight weeks. This could be caused by a chronic infection such as tuberculosis, chronic bronchitis, or Heaven forbid a tumor which has grown on an airway surface. It could be caused by asthma, one of the most common causes of chronic cough. Once again GERD can be chronic and the cause as well as post-nasal drip. Some infectious diseases other than TB can cause chronic symptoms. One example is Whooping cough in which the cough can hang on for many weeks. Another cause is Respiratory Syncytial Virus, called RSV. This can cause an infant to cough for a year or more. There are chronic medical conditions like congestive heart failure or sarcoidosis which could lead to persistent symptoms. All the causes of chronic are beyond the scope of this article, but suffice it to say, your doctor has a lot of things to consider when a patient coughs.
Let's talk about the treatment. The first step is to address the underlying cause. This might include prescribing erythromycin or another antibiotic for Whooping . It might include prescribing an antiviral for RSV or the flu. It might be to tell the patient to desist any and all cigarette smoking. It might include prescribing an H2 blocker or a proton pump inhibitor for GERD, or changing the GERD patient's eating habits. It might be preventive before the cough by giving DPT and measles immunization. It might be treating other underlying medical conditions.
The symptomatic treatment for cough is controversial, and certain prohibitions can apply in many ways. If a child is under four, you shouldn't give any old cough syrup without checking with doctor. These can affect the respiratory drive mechanism in little ones with disastrous results. Over the age of two things with lemon and honey are probably safe. An older child might do well with cough drops. The next thing to consider is whether it is productive or non-productive. It is not a good idea to give suppressants like codeine and Dextromethorphan for a productive cough. It is better to give medicines which liquefy and break up the secretions so they can be coughed up. These are called 'expectorants"; an example would be Guiafencin. If it is dry and non-productive, a suppressant might be appropriate: codeine and dextromethorphan work by dulling the vagus nerve. There's another non-narcotic product which suppresses it by anesthetizing the lung stretch receptors.
There are certain signs that call for a physician evaluation as soon as possible. One would be a fever at or above 101F. This suggests a bacterial infection or pneumonia. Another would be discolored sputum greenish, yellow, and rust-colored or with blood in sputum. This suggests something more serious. A persistent chest pain is another reason: Some people can expel so hard that they crack a rib, or somebody with emphysema can pop an Emphysema bleb, causing air in the chest outside the lung causing a spontaneous pneumothorax. If someone had been bothered by calf pain for days, sharp chest pain could suggest a blood clot to the lungs, a serious emergency. Another would be severe shortness of breath or wheezing, suggesting an acute severe asthma attack.
These are some thoughts on the cough. Remember it's mostly a good thing, protecting our airways from infections and foreign bodies. Sometimes it can be a sign that something is going on that needs a serious professional evaluation. A good rule of thumb is, as in most medical problems, "when in doubt, get it checked out!" See your physician ASAP.
