DIAGNOSIS AND TREATMENT OF REFLUX COUGH
Thank you very much for your letter about this lady. I think the most important thing is to be confident of the diagnosis. Over the last five years it has become increasingly obvious to me that there is a very characteristic history in patients with reflux cough, which can all be explained with the knowledge of the pathophysiology of reflux.
Almost all reflux is due to transient openings of the lower oesophageal sphincter (LOS). The LOS closes while we are asleep, increasing pressure by about 5-10 mmH2O. Reflux cough then is rare at night. When it does occur it indicates a very lax LOS. In complete contrast to asthma the reflux cougher wakes without coughing. Itís when they get up, usually on reaching the bathroom or going down the stairs that they start coughing. This is the LOS opening physiologically to allow gas trapped in the stomach overnight to escape. Other patients start coughing with food, particularly breakfast. There are two times when this occurs, firstly during the act of swallowing, usually dry foods such as toast or biscuits. What happens is the pharyngeal lower oesophageal sphincter reflex causes LOS opening and the patient coughs just as they are about to swallow. Secondly, classic reflux occurs post prandially. However, reflux cough occurs earlier than heartburn, since the stomach acid has been neutralised by the food. The key is to remember that reflux cough is not the same as heartburn and is a much less closely acid related phenomenon than heartburn.
Another set of symptoms, which are often dismissed as non specific, which in reality are highly specific, is cough on phonation. Typically the patient will be speaking on the telephone (raised intra abdominal pressure through sitting) and right in the middle of a sentence the patient will start coughing and frequently have to hand the receiver over to someone else. This is the diaphragm, which normally holds the LOS shut, being used for phonation and allowing reflux waves to slip past. A similar phenomenon occurs on singing and laughing. Frequently the reflux wave hits the larynx and leads to aphonia or a change in the quality of the voice.
It is important to realise that the reflux frequently goes all the way to the larynx and indeed the American ENT surgeons call it laryngopharyngeal reflux. It gives rise to sore throat, a characteristic tickle and the desire to clear oneís throat; patients will be swallowing repeatedly. Often there is a funny taste in the mouth and I am sure that some of the nasal symptoms people complain of is reflux going up the back of the nose. It can even go up the Eustachian tubes and a paper in the Lancet a year or so ago described pepsin being found in the middle ears of a considerable number of children who were having grommets inserted.
Having made a firm clinical diagnosis of reflux cough then courage and persistence is needed to treat it. Firstly, work by Don Castell in North Carolina shows that conventional acid suppression, whilst working very well for heartburn, does not cause anything like sufficient acid suppression for reflux cough. PPIs have a very short half life in the body and if one is to achieve total acid suppression one needs to give them twice daily with meals, breakfast and tea, and 300 mg of Ranitidine at night to block the histamine led nocturnal acid secretion. I would normally try this regime for two months. If this fails then Gaviscon Advance works quite well in some patients. It is particularly effective in patients with abnormal LOS manometry. Next we would try a monthís worth of Metoclopramide 10 mg tds or Domperidone 10 mg tds. Maxalon seems to work better. These are our first line treatments and usually at this point if there is treatment failure I would ask for oesophageal manometry and pH monitoring, since if there is significant acid reflux the best option may be fundoplication. We have a group of patients who refuse or are unable to go down this route and then our second line agents, magnesium, Baclofen (increases LOS tone) and anti cholinergic agents can be tried. Finally, opiates can be very helpful at low dose (MST 5mg bd), although the side effect profile is intolerable in some of the ladies.
PROFESSOR ALYN H MORICE
Professor of Respiratory Medicine
Head of Division of Academic Medicine