Patients present with symptoms. Doctors are trained to recognise disease. There is no better illustration of these two different paradigms than cough. Unfortunately for the patient, the sensory input triggering the cough reflex may arise from anywhere in the territory of the vagus nerve. Thus, chronic cough may be caused by conditions treated by at least three different specialists—the ENT surgeon, the gastroenterologist, and the chest physician. Because of our speciality led view of the world, the doctor may not have received training in the condition causing the symptom. There is a risk of treating the patient for the condition with which the doctor is familiar rather than that most likely to be the cause of the cough. In a recent survey of over 300 patients who had asked for information about chronic cough, most had consulted at least one specialist of whom 69% were chest physicians. Presumably the treatment had not worked, which is why they needed further information; this suggests an urgent need for greater understanding. For this reason, Thorax has commissioned a review series on the aetiology and treatment of this disabling and socially isolating symptom.

In contrast to experience in general chest clinics,¹ there is extensive literature to support the very high treatment success rates seen in specialist cough clinics throughout the world,² supporting grounds for optimism. Most of these therapeutic successes are achieved without resorting to sophisticated specialised investigations. The clinical history is the major clue to the diagnosis in chronic cough. However, knowledge of the pathophysiology of the various conditions is vital to understanding these clues. In the differentiation of asthmatic and reflux cough, for example, the diurnal variability of the cough is often sufficient to make the diagnosis. In 1698 Sir John Floyer³ first described the still unexplained nocturnal exacerbations of asthma symptoms, and nocturnal cough remains a common symptom of cough predominant asthma. In contrast, a patient with reflux cough will rarely cough at night. Appreciation of this requires a knowledge of the physiology of the lower oesophageal sphincter.⁴ The sphincter closes at night, diminishing reflux and causing the cough to abate. The patient with reflux cough wakes peacefully and not as in Floyer’s own graphic description of the morning exacerbation “at first waking the fit takes me”. Rather, the paroxysms of coughing start when the patient gets up and the sphincter opens to allow for belching. It is hoped that this series of reviews will provide the reader with valuable clinical pointers to aid in the management of these potentially challenging patients.

In the last two reviews of the series, recent developments in the physiology and pharmacology of cough will be summarised. For many years the term “cough receptor” has been used in what is no more than the description of the type of nerve fibre transmitting the stimulus. In the last few years the first genuine cough receptor—the VR1—has been cloned, and there has been a rapid increase in the basic knowledge of cough receptor function. From this may arise treatments which may be effective in the single most common presenting complaint for which new patients seek medical advice.⁵