31/12/2025
Chronic cough with normal CXR
A "normal CXR" in a chronic cough patient is the starting line for a diagnostic challenge. The "smart" way to manage this is to move away from the traditional "anatomic approach" (treat drip, then asthma, then reflux) and adopt the Cough Hypersensitivity Syndrome (CHS) paradigm.
Here is the expert-level management protocol:
1. The "Smart" Exclusion (Before you start)
тАв The ACE-Inhibitor Trap: Do not just ask if they started it recently. Cough can develop years after starting.
тАв Smart Move: Stop the ACE-I. Switch to an ARB. Wait 4 weeks. If cough persists, it wasn't the drug.
тАв The CT Threshold: If the cough is > 8 weeks and CXR is normal, a Non-Contrast CT Chest is often warranted to rule out conditions invisible on plain film:
тАв Small central bronchiectasis.
тАв Early ILD (e.g., focal fibrotic changes).
тАв Carcinoid tumor / Endobronchial lesion.
2. Phenotyping the Inflammation (The "Treatable Traits")
Don't guess; phenotype. Using biomarkers avoids "therapeutic trials" that last months.
тАв Trait 1: Eosinophilic Inflammation (The Steroid Responders)
тАв Diagnoses: Cough Variant Asthma (CVA) OR Non-Asthmatic Eosinophilic Bronchitis (NAEB).
тАв The Smart Diff:
тАв CVA: Positive Methacholine Challenge + High FeNO.
тАв NAEB: Negative Methacholine Challenge + High Sputum Eosinophils (>3%).
тАв Why it matters: NAEB patients do not have bronchoconstriction. Bronchodilators will fail. They need high-dose Inhaled Corticosteroids (ICS) alone.
тАв Trait 2: Upper Airway Cough Syndrome (UACS)
тАв The Smart Move: CXR sinus views are useless. If you suspect "silent" sinusitis, order a CT Sinus.
тАв Rx: Aggressive nasal hygiene (Saline rinse + Intranasal steroid + Antihistamine/Decongestant) for 2-4 weeks.
тАв Trait 3: Gastro-Esophageal Reflux (GERD/LPR)
тАв The Trap: 50% of reflux-induced cough is non-acid or weakly acidic. PPIs will fail.
тАв The Smart Move: If a 4-week trial of high-dose PPI fails, do not double the dose. Order 24h Impedance-pH monitoring. If non-acid reflux is found, the solution is Baclofen, Prokinetics (Itopride), or FundoplicationтАФnot more Omeprazole.
3. Managing "Unexplained" Chronic Cough (UCC)
When the triad (Asthma, GERD, UACS) is negative or treated, the diagnosis shifts to Cough Hypersensitivity Syndrome. This is a neuropathy of the vagus nerve.
A. The Neuromodulator Ladder
Treat this like neuropathic pain. The goal is to dampen the hypersensitive cough reflex arc.
1. Gabapentin: Start low (300 mg HS) and titrate up to 900тАУ1800 mg/day.
тАв Evidence: High-quality RCT evidence for efficacy in UCC.
2. Pregabalin: Easier dosing profile than Gabapentin.
3. Amitriptyline: 10тАУ25 mg at night. Good if the patient also has insomnia or laryngeal paresthesia ("tickle" in the throat).
4. Morphine (Low Dose): 5mg SR BID. Highly effective for refractory cough but reserved for end-stage or severe cases due to side effects.
B. The Non-Pharmacological "Game Changer"
тАв Speech & Language Therapy (Speech Pathology):
тАв Refer for "Laryngeal Hygiene" and "Cough Suppression Techniques."
тАв Why: Chronic cough creates a loop where coughing irritates the vocal cords, causing more coughing. Specialized physiotherapy breaks this cycle. Efficacy is comparable to Gabapentin without the sedation.
4. The Cutting Edge: P2X3 Antagonists
тАв Gefapixant: The first-in-class P2X3 receptor antagonist.
тАв Mechanism: It blocks the ATP-gated ion channels on the vagal afferent nerves, directly stopping the signal initiation.
тАв Status: Approved in some regions (check local availability).
тАв Side Effect: Dysgeusia (taste disturbance) is the main limiting factor.
"Smart" Algorithm
1. Visit 1: Stop ACE-I. Check FeNO & Spirometry.
тАв High FeNO/Reversible: Treat as Asthma (ICS/LABA).
тАв Normal: Empiric UACS therapy (Nasal steroid + rinse).
2. Visit 2 (4 weeks later): Cough persists?
тАв CT Chest (Rule out structural).
тАв Sputum Induction (Rule out NAEB).
тАв Trial of PPI (only if heartburn/regurgitation present).
3. Visit 3 (8 weeks later): Cough persists?
тАв Diagnosis: Refractory Chronic Cough (Hypersensitivity).
тАв Start Neuromodulator: Gabapentin 300mg HS (titrate).
тАв Refer: Speech Therapy for cough suppression.
4. Visit 4: Still coughing?
тАв Consider Gefapixant or low-dose Opiates.
тАв Review for rare causes (Tracheobronchopathia osteochondroplastica, Tonsillar hypertrophy).
