Key distinguishing features of the most common diagnoses
|Worse Lying Down||Possible||No||No||Yes||No|
|Swelling of Ankles||No||Possible||No||Yes||No|
Possible:Peak flow, U&E, LFT, ESR/CRP, BNP, ECG, spirometry.
Small Print:Pulse oximetry, serum precipitins, CT scan, hospital-based tests for pulmonary embolism, pleural tap, echocardiogram, bronchoscopic biopsy or nodal aspiration.
- CXR: The single most useful investigation. Will reveal or give clues to many of the causes listed.
- FBC essential to look for anaemia; ESR/CRP raised in carcinoma, inflammation and infection.
- U&E and LFT: Impaired renal function will contribute to CCF; LFT may show signs of disseminated carcinoma.
- Peak expiratory flow rate variability in asthma (guidance recommends testing fractional exhaled nitric oxide in suspected asthma but this may not be practical, or available); more comprehensive lung function tests (spirometry) are more helpful to diagnose COPD and other lung diseases.
- ECG: Heart failure is unlikely if the ECG is normal.
- BNP: Likely to be elevated in heart failure.
- Pulse oximetry: Helps guide assessment of severity and decisions about oxygen therapy but of little help in making the diagnosis.
- Serum precipitins: In suspected extrinsic allergic alveolitis.
- Referral for more difficult cases may result in CT (e.g. for bronchiectasis), pleural tap (diagnostic and therapeutic for pleural effusion), echocardiography (for heart valve lesions and assessment of left ventricular function), hospital-based tests for pulmonary embolism and bronchoscopic biopsy or nodal aspiration (for sarcoidosis).
- Cardiac failure may arise as a complication of COPD. Remember this possibility if a patient with COPD complains of gradually increasing breathlessness unrelieved by standard treatment.
- Do not forget to listen to the heart sounds, especially if there is no clear respiratory cause and the patient is not in cardiac failure – aortic stenosis may cause significant shortness of breath.
- In the young and middle-aged, sighing speech and shortness of breath worse with stress or without any clear pattern – especially if the patient does not consistently have a problem with exercise – are likely to be caused by hyperventilation.
- Weight loss and clubbing with shortness of breath suggest bronchial carcinoma, though bronchiectasis is possible – arrange an urgent CXR.
- Wheeze may be present in cardiac failure – crepitations may not. Look for other signs of CCF in the elderly and consider appropriate investigation and treatment.
- Remember that acute causes can supervene at any time – for example, beware of pneumothorax in the asthmatic.
- Cardiac failure has a poor prognosis; look for an underlying cause (e.g. hypertension) and arrange echocardiography with a view to starting ACE inhibitors.
- Don’t forget anaemia as a possible cause – contrary to popular belief this tends to cause shortness of breath rather than tiredness.