cough is an onomatopoeic word in most languages (e.g.
kuchen, tosse, tossa, toux). It has been called the ‘watchdog of the lungs’. When it barks it warns you that there may be an intruder (inhalation of an irritant), there may be something wrong in the house (lung disease), or perhaps the dog is asking for attention (communication). Cough always requires interpretation.
A cough is a deep inspiration, followed by a powerful expiratory effort while the
larynx (voicebox) is reflexly closed by bringing together the vocal cords; then the larynx suddenly opens, allowing a rapid flow of air from the lungs which will repel the intruder or expel the material in the airways that needs to be coughed up. Cough is the most violent of respiratory acts. Put your hands on your abdomen and cough and you will see. Expiratory pressures in the chest may be three times that of blood pressure (and occasionally coughing can break blood vessels), and the airflow velocity in the larynx may approach supersonic levels. During coughing the airways in the chest are squeezed, and the expiratory blast forces
mucus secretions through these narrow passages out into the open air. The associated cough sound is part of the definition of cough. The sound varies, from a simple single or double pattern of ‘dry’ cough, due, for example, to laryngitis, to the bubbling, rumbling cough sound of disease with much mucus in the airways.
Cough is the commonest and sometimes the most distressing symptom of lung disease, far more so than breathlessness or pain, and can be caused by over 100 chest and lung diseases. Probably the most frequent cause of coughing is cigarette
smoking, but this has never been assessed because smokers do not complain to the doctor; they would be told to stop smoking, which is not what they want to hear. Although only the first breaths of cigarette smoke cause cough, and the smoker rapidly becomes acclimatized, smoking causes mucus secretion in the bronchi, and this produces the typical early morning smokers' cough. Later, and unfortunately, the smoker may develop
chronic bronchitis, characterized by chronic cough and
phlegm production.
The commonest disease to cause cough is upper airway infection (due to influenza, sinusitis, etc.), but there are some bizarre causes, such as an earwig in the external ear (which is supplied by the same nerve as the lungs). Cough can be psychological, as Sigmund Freud recognized when some of his patients presented with ‘hysterical cough’, including the first historical case of psychoanalysis, Anna O. Unlike sneezing, hiccough, and yawn, cough can be voluntarily produced with its complete pattern, and we may use it as a form of communication. The speaker may cough (clear his throat) to attract the attention of his audience, and the audience may get its revenge by ‘coughing him down’. Voluntary or not, coughing can ‘drown the parson's saw’ (Macbeth).
It seems common experience in concert halls and theatres that we cannot suppress a cough, although the cougher and his neighbours may disagree about this. However, cough due to upper airway infection can be suppressed for quite long (5–20 min) periods, so perhaps the old adage that ‘love and cough cannot be hid’ is wrong in both respects.
John Widdicombe
