How is shortness of breath (dyspnea) graded using the New York Heart Association (NYHA), Modified Medical Research Council (mMRC), and Borg scales?

Grading Shortness of Breath: Clinical Scales and Their Applications

Modified Medical Research Council (mMRC) Scale

The mMRC scale is a 5-point functional dyspnea scale (grades 0-4) that assesses breathlessness based on activity limitations, with scores ≥2 indicating high symptom burden and increased mortality risk in COPD patients 1, 2.

mMRC Grade Definitions:

• Grade 0: No breathlessness except during strenuous exercise 1
• Grade 1: Breathlessness when hurrying or walking up a slight hill 1
• Grade 2: Walks slower than peers due to breathlessness, or must stop for breath when walking at own pace on level ground 1
• Grade 3: Stops for breath after walking approximately 100 meters or after a few minutes on level ground 1
• Grade 4: Too breathless to leave the house, or breathless when dressing/undressing 1

Clinical Application:

• The mMRC measures symptom impact or burden rather than real-time intensity, making it appropriate for assessing functional disability and long-term disease severity 1, 3
• An mMRC score ≥2 combined with severe spirometry (GOLD grade 3-4) and/or ≥2 exacerbations yearly identifies high-risk COPD patients requiring intensive treatment 1, 2
• Increased mMRC levels independently predict mortality in COPD 1, 2

Borg Scale

The Borg scale (typically 0-10 modified version) measures real-time sensory-perceptual intensity of dyspnea during exercise or acute episodes, where 0 represents no breathlessness and 10 represents maximal breathlessness 1, 3.

Key Characteristics:

• The Borg scale captures what breathing feels like at a specific moment, making it ideal for exercise testing and acute symptom monitoring 1, 3
• It correlates well with objective measures like peak expiratory flow rate (PEFR) and oxygen saturation in acute bronchospasm 4
• In asthma patients, mean Borg scores decreased from 5.1 to 2.4 post-treatment, correlating significantly with PEFR improvement (r = -0.31, p <0.05) 4
• In COPD patients, mean Borg scores decreased from 6.0 to 3.0 post-treatment, with stronger correlation to PEFR changes (r = -0.42, p <0.001) 4

Clinical Application:

• Use the Borg scale for acute dyspnea assessment during emergency department visits, exercise testing, or pulmonary rehabilitation 4, 5
• Target scores ≥4 for symptom-relieving interventions, with scores ≥7 requiring urgent management 3

New York Heart Association (NYHA) Classification

While the evidence provided does not detail NYHA grading specifically, it is a 4-class functional classification system used primarily for heart failure patients to grade activity-related symptoms.

Critical Distinction: Choosing the Right Scale

Select your dyspnea scale based on the measurement domain you need to assess 1, 3:

Use mMRC when:

• Assessing functional impact on daily activities and quality of life 1, 3
• Risk-stratifying COPD patients for prognosis and treatment intensity 1, 2
• Incorporating dyspnea into composite prognostic indices (BODE, ADO, DOSE) 2

Use Borg Scale when:

• Measuring real-time symptom intensity during exercise testing 1, 3
• Monitoring acute dyspnea in emergency settings 4
• Assessing immediate response to bronchodilator therapy 4

Common Pitfall:

Do not use the mMRC to assess acute dyspnea intensity or exercise-induced symptoms—it measures functional disability, not real-time sensation 1, 3. Conversely, do not use the Borg scale for long-term functional assessment or prognosis, as it captures only momentary intensity 1.