# Dyspnoea Approach and Cardiopulmonary Exercise Testing > Dyspnoea approach for NEET-PG Medicine covering cardiac versus pulmonary breathlessness, MRC grading, breathing reserve and what exercise testing separates. - Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/dyspnoea-approach-and-cardiopulmonary-exercise-testing - Exam / course: NEET-PG · Subject: Medicine - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-14 - Last updated: 2026-10-14 - Reference basis: Harrison's Principles of Internal Medicine; Murray and Nadel's Textbook of Respiratory Medicine; Davidson's Principles and Practice of Medicine - How to cite: "Dyspnoea Approach and Cardiopulmonary Exercise Testing", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/dyspnoea-approach-and-cardiopulmonary-exercise-testing ## Direct answer Dyspnoea is the subjective sensation of breathlessness, and a structured approach separates cardiac, respiratory, haematological and deconditioning causes. Cardiopulmonary exercise testing measures oxygen uptake, anaerobic threshold and ventilatory response during exercise. A low anaerobic threshold with a steep ventilatory equivalent for carbon dioxide and a reduced oxygen pulse points to cardiac limitation. A low breathing reserve at peak effort points to lung or respiratory muscle limitation. ## What you must remember - **MRC grade:** a five-point scale, with grade 1 breathless only on strenuous exertion and grade 5 too breathless to leave the house or dress. - **Cardiac clues:** orthopnoea, paroxysmal nocturnal dyspnoea, raised JVP, third heart sound and a raised natriuretic peptide suggest left heart failure or valve disease. - **Respiratory clues:** wheeze, chronic sputum, crackles, clubbing and abnormal spirometry or DLCO suggest COPD, asthma or interstitial disease. - **Other causes:** anaemia, obesity, deconditioning and anxiety-related hyperventilation are diagnoses of exclusion after organic causes are checked. - **CPET outputs:** peak oxygen uptake, anaerobic threshold, the ventilatory equivalent slope for carbon dioxide, oxygen pulse and breathing reserve. - **Breathing reserve:** the gap between maximum voluntary ventilation and peak exercise ventilation, reduced in lung or respiratory muscle limitation. ## A 60-year-old with breathlessness on climbing stairs A 60-year-old man has breathlessness on climbing one flight of stairs, with mild ankle swelling and a smoking history. His spirometry shows a mild obstructive pattern, but his symptoms seem out of proportion to it, so the cause is unclear. A patient who reports breathlessness must be placed in a category before testing, because the same symptom arises from the heart, lungs, blood and muscles. The steps below move from history to the specialised exercise test. 1. **Characterise the breathlessness:** Onset, exertional threshold, orthopnoea, paroxysmal nocturnal dyspnoea and the speed of progression are recorded first. 2. **Grade the severity:** The MRC scale quantifies disability and helps track response to treatment over time. 3. **Examine for clues:** Raised JVP, a third heart sound, crepitations, wheeze, clubbing, pallor and oedema direct the next investigations. 4. **Investigate first-line:** An ECG, chest X-ray, full blood count, spirometry with DLCO and a natriuretic peptide help separate cardiac from pulmonary causes. 5. **Image when needed:** Echocardiography assesses valves and ventricular function, CT pulmonary angiography looks for embolism, and HRCT examines interstitial disease. 6. **Use CPET for unclear cases:** Cardiopulmonary exercise testing is ordered when the cause remains uncertain, and it separates cardiac, ventilatory and deconditioning limitation. ## Where the exam tests breathlessness The exam tests whether you assign the right system before ordering the right test. - **Trap:** attributing breathlessness to the lungs without an echocardiogram — **Correct:** heart failure and valve disease are common causes of dyspnoea, and natriuretic peptide and echocardiography help exclude them. - **Trap:** reading normal spirometry as proof that the lungs are normal — **Correct:** spirometry can miss interstitial disease, pulmonary vascular disease and deconditioning, so DLCO and CPET help. - **Trap:** ordering CPET first in every breathless patient — **Correct:** CPET is used for unclear cases after basic tests, because its interpretation needs the clinical context. - **Trap:** labelling every breathlessness as anxiety — **Correct:** anxiety is a diagnosis of exclusion, and organic causes must be excluded first. ## Frequently asked questions ### What separates cardiac from pulmonary breathlessness on cardiopulmonary exercise testing? Cardiac limitation shows a low anaerobic threshold, a steep ventilatory equivalent for carbon dioxide and a reduced oxygen pulse, with breathing reserve usually preserved. Pulmonary limitation shows a low breathing reserve at peak effort, meaning ventilation itself cannot meet the demand. ### What is the MRC dyspnoea scale used for? The MRC dyspnoea scale grades breathlessness from grade 1, which occurs only with strenuous exertion, to grade 5, which prevents leaving the house or dressing. It quantifies disability in a simple way and is used to track response to treatment in chronic heart and lung disease. ### What is breathing reserve in cardiopulmonary exercise testing? Breathing reserve is the difference between maximum voluntary ventilation and the minute ventilation reached at peak exercise, expressed as a percentage. A low breathing reserve at peak effort suggests that the lungs or respiratory muscles limit exercise, rather than the heart. ### When is cardiopulmonary exercise testing ordered in dyspnoea? Cardiopulmonary exercise testing is ordered when the cause of breathlessness remains unclear after basic cardiac and respiratory tests, or when exercise limitation must be quantified. It helps distinguish cardiac, ventilatory and deconditioning limitation, and it is interpreted alongside imaging and spirometry.