Cough

Introduction

Cough is a common presenting symptom in primary care settings across Canada. As a future Canadian physician preparing for the MCCQE1, understanding the intricacies of cough diagnosis and management is crucial. This guide will help you navigate through the key concepts, with a focus on Canadian guidelines and practices.

Definition and Classification

A cough is a protective reflex that helps clear the airways of irritants, foreign particles, and excess secretions. For MCCQE1 preparation, it's essential to understand the classification of cough:

Etiology

Understanding the common causes of cough is crucial for MCCQE1 success. Here's a mnemonic to help remember the most frequent etiologies in the Canadian context:

CANADA COUGHS

• Chronic Obstructive Pulmonary Disease (COPD)
• Asthma
• Neoplasm
• Angiotensin-Converting Enzyme (ACE) inhibitors
• Drip (Post-nasal)
• Acute viral or bacterial infection

• Cystic Fibrosis
• Occupational exposures (relevant in Canadian industries)
• Upper airway cough syndrome
• Gastroesophageal reflux disease (GERD)
• Heart failure
• Smoking-related conditions

Clinical Approach

When preparing for the MCCQE1, remember the importance of a thorough clinical approach to cough. Here are the key steps:

Management

Management of cough in Canada follows evidence-based guidelines. Here's a general approach:

1. Treat the underlying cause
2. Symptomatic relief:
   • Over-the-counter cough suppressants (dextromethorphan)
   • Honey for cough in children (as per Canadian Paediatric Society guidelines)
3. Avoid unnecessary antibiotic use (aligning with Canadian antibiotic stewardship programs)

Canadian Guidelines

The Canadian Thoracic Society provides guidelines for the management of cough in adults. Key points include:

• Chest X-ray and spirometry are recommended as initial investigations for chronic cough
• Empiric treatment trials are suggested for common causes (GERD, asthma, upper airway cough syndrome)
• Referral to a cough specialist is recommended if cough persists despite treatment of common causes

Key Points to Remember for MCCQE1

• Classify cough based on duration (acute, subacute, chronic)
• Remember the "CANADA COUGHS" mnemonic for etiology
• Conduct a thorough history and physical examination
• Consider occupational exposures relevant to Canadian industries
• Follow Canadian guidelines for investigations and management
• Be aware of antibiotic stewardship principles in Canadian healthcare
• Understand the role of over-the-counter medications and natural remedies (e.g., honey) in cough management

Sample Question

# Sample Question

A 45-year-old woman presents with a persistent dry cough for the past 10 weeks. She has no history of smoking and denies any shortness of breath or chest pain. Her physical examination is unremarkable, and her chest X-ray is normal. She has been taking lisinopril for hypertension for the past 3 months. Which one of the following is the most appropriate next step in management?

- [ ] A. Prescribe a short course of oral corticosteroids
- [ ] B. Order high-resolution CT scan of the chest
- [ ] C. Switch lisinopril to a calcium channel blocker
- [ ] D. Start empiric treatment for gastroesophageal reflux disease
- [ ] E. Refer for bronchoscopy

Explanation

The correct answer is:

• C. Switch lisinopril to a calcium channel blocker

This patient's presentation is consistent with chronic cough (duration >8 weeks) likely caused by an ACE inhibitor (lisinopril). ACE inhibitor-induced cough is a well-known side effect, occurring in up to 10% of patients, and can develop weeks to months after starting the medication.

The most appropriate next step is to switch the ACE inhibitor to an alternative antihypertensive medication, such as a calcium channel blocker. This aligns with Canadian hypertension guidelines, which recommend considering medication side effects in treatment decisions.

Other options are less appropriate:

• A: Corticosteroids are not indicated without evidence of airway inflammation.
• B: High-resolution CT is not necessary given the normal chest X-ray and lack of concerning symptoms.
• D: While GERD is a common cause of chronic cough, it's less likely given the temporal relationship with ACE inhibitor use.
• E: Bronchoscopy is an invasive procedure and not indicated as a first-line investigation in this scenario.

This question tests your ability to recognize medication side effects and manage hypertension in the context of other medical issues, which are important skills for Canadian physicians and key areas of focus for the MCCQE1.

References

1. Canadian Thoracic Society. (2022). Canadian Thoracic Society Cough Guideline. Retrieved from https://cts-sct.ca/guideline-library/ (opens in a new tab)

2. O'Byrne, P. M., et al. (2021). Canadian Thoracic Society asthma guideline update 2021: Diagnosis, management, and prevention of asthma in preschoolers, children, and adults. Canadian Journal of Respiratory, Critical Care, and Sleep Medicine, 5(6), 348-361.

3. Bourbeau, J., et al. (2019). Canadian Thoracic Society Clinical Practice Guideline on pharmacotherapy in patients with COPD – 2019 update of evidence. Canadian Journal of Respiratory, Critical Care, and Sleep Medicine, 3(4), 210-232.

4. Canadian Paediatric Society. (2021). Recommendations for the use of over-the-counter cough and cold medications in children. Paediatrics & Child Health, 26(1), 56-57.

5. Hypertension Canada. (2020). 2020 Hypertension Canada Guidelines for the Prevention, Diagnosis, Risk Assessment, and Treatment of Hypertension in Adults and Children. Canadian Journal of Cardiology, 36(5), 596-624.