Coughing

What causes persistent coughing in reflux?

There are two theories as to how GERD causes cough. Firstly, reflux of substances from the stomach may directly irritate the throat and/or airways and lungs, especially the larynx. Historically acid was always thought to be responsible. However, weakly acidic reflux and possibly other substances including Pepsin may also irritate the throat and airways by a direct chemical effect. Modern diagnostic tests can also identify gaseous reflux events at the top of the oesophagus and these probably contain irritating substances from the stomach in aerosolised form.

The second theory is that reflux events into the oesophagus can cause cough via nervous reflexes. It is thought that this may reflect an early protective mechanism to protect the lungs from reflux damage. GERD is one of the recognised causes of Cough Hypersensitivity Syndrome in which the nerves of the respiratory tract become sensitised and more easily provoked to cause coughing.

There is also a probable link between cough, reflux and asthma. Asthma can cause a cough and is more common in patients with reflux. Direct injury to the small airways in the lung by reflux may precipitate an asthma attack or it may be caused by nervous reflexes. Interestingly treating GERD can help asthma symptoms including shortness of breath and cough.

Finally, GERD may be associated with other lung conditions including bronchiectasis and pulmonary fibrosis. These can cause a cough in their own right.

Finally, SIBO can cause LPR symptoms including a cough.

How is a persistent cough due to reflux diagnosed?

The cause of a cough is diagnosed by a combination of a clinician listening to a patient’s “history”, physical examination including visualisation of the throat and then diagnostic tests. This process is ideally undertaken within the context of a multi-disciplinary team. There are some features that may suggest reflux is responsible. These include;

• Other reflux symptoms
• Associated with eating
• Worsened by lying down or at night
• Symptoms helped by anti-acid medications such as PPIs

It’s important to note that there are often no specific indicators that reflux is responsible and so for instance failure to respond to PPIs does not indicate that reflux isn’t responsible. Equally, it is often important that diseases of the lungs and airways are ruled out before diagnosing GERD as the cause of a cough. For instance, it may co-exist with asthma independently and treatment of this cure the cough.

Diagnostic tests for GERD and cough include;

• Laryngoscopy. A flexible laryngoscope is a this tube that inserted through the nose to allow direct visualisation of the throat and especially the larynx.
• Gastroscopy: Otherwise known as upper GI endoscopy this involves inserting an endoscope through the mouth or nose into the oesophagus and then through the stomach and duodenum (together known as the “foregut”). The endoscope has a high definition camera enabling the operator to look for structural abnormalities such as hiatus hernias. They will also evaluate the lining of the foregut, for instance identifying oesophagitis, Barrett’s oesophagus and ulcers. If necessary samples of tissue (biopsies) can be taken for analysis. The examination can be performed with local anaesthetic spray, intra-venous sedation or under general anaesthetic.
• 24 hour catheter reflux monitoring. A small tube (catheter) is inserted through the nose to the bottom of the oesophagus and measures reflux events usually over 24 hours at the bottom as well as the top of the oesophagus. It will also include a pH sensor in the stomach to ensure normal acid production. The catheter is attached to a recorder about the size of a mobile phone and patients can record when they experience symptoms allowing correlation between the two. These are known as “symptom associations”. pH testing assesses acidic/non acidic reflux events. Modern testing includes impedance which offers the advantage that it also distinguishes between liquid, solid and gas reflux events. Impedance can therefore identify reflux and its relationship with cough. 
• Oesophageal pH capsule reflux test. The Bravo test involves attaching a tiny capsule during a gastroscopy onto the lining of the oesophagus just above the stomach. This records acid reflux over a period of 48-96 hours. Instead of a catheter it sends the data wirelessly to a recorder and falls off after the test is complete. The procedure is usually performed under conscious sedation. 
• Salivary Pepsin Test. It is now possible to measure the concentration of Pepsin in the saliva. This may suggest evidence of GERD. However, while this test can be a useful indicator is not considered sufficiently accurate to definitively diagnose GERD. A negative tests does not rule reflux out while a positive test does not categorically confirm the diagnosis.
• SIBO/Intolerance Tests; breath tests are most commonly used to diagnose small intestinal bacterial overgrowth (SIBO) and malabsorption of sugars such as lactose or fructose. In the case of SIBO, following drinking a sugar solution the exhaled breath is tested over two hours to measure the production of hydrogen and methane gases by gut bacteria.

What are the treatments for coughing?

Reaching the right diagnosis is key to planning treatment. When a cough is caused by GORD an escalating strategy depending on effectiveness is usually recommended.

Lifestyle changes;

• Dietary changes such as eating smaller meals, avoiding trigger foods, eating earlier in the day
• Losing weight
• Stopping smoking
• Elevating the head of the bed at night

Medications;

• Alginates such as Gaviscon
• Simple anti-acids such as sodium bicarbonate
• H2 blockers such as Famotidine and Nizatadine
• Proton pump inhibitors (PPIs) such as Omeprazole and Nexium
• Others including Baclofen and Sildinafil which can relax the oesophageal muscle may be helpful

Anti-reflux procedures;

• TIF
• Laparoscopic fundoplication
• Laparoscopic LINX
• Laparoscopic RefluxStop

Page reviewed by: Mr Nick Boyle BM MS FRCS 01/09/24