Investigations

1st investigations to order

spirometry

Test
Result
Test

COPD is classified based on the patient's FEV1 and its percentage of the predicted FEV1. In cases where FVC may be hard to measure, FEV6 (forced expiratory volume at 6 seconds) can be used. [21]

Result

FEV1/FVC ratio <0.70; total absence of reversibility is neither required nor the most typical result

pulse oximetry

Test
Result
Test

Checked as part of vital signs on acute presentation. A good pulse wave should be picked up by the device. In patients with chronic disease, an oxygen saturation of 88% to 90% may be acceptable.

If <92% arterial or capillary blood gases should be checked. [1]

Result

low oxygen saturation

ABG

Test
Result
Test

Checked in patients who are acutely unwell, especially if they have an abnormal pulse oximetry reading. Should also be performed in stable patients with FEV1 <35% predicted or with clinical signs suggestive of respiratory failure, or if peripheral arterial oxygen saturation is <92%.

Hypercapnia, hypoxia, and respiratory acidosis are signs of impending respiratory failure and possible need for intubation.

Result

PaCO₂ >50 mmHg and/or PaO₂ of <60 mmHg suggests respiratory insufficiency

CXR

Test
Result
Test

Seldom diagnostic, but useful in ruling out other pathologies.

Increased anteroposterior ratio, flattened diaphragm, increased intercostal spaces, and hyperlucent lungs may be seen. com.bmj.content.model.Caption@12a2c293 [Figure caption and citation for the preceding image starts]: COPD chest x-ray (AP view): hyperinflated lung, flattened diaphragm, increased intercostal spaces From the collection of Manoochehr Abadian Sharifabad, MD [Citation ends]. com.bmj.content.model.Caption@693f2a35 [Figure caption and citation for the preceding image starts]: COPD chest x-ray (lateral view): hyperinflated lung, flattened diaphragm, increased antero-posterior diameter (barrel chest) in lateral view From the collection of Manoochehr Abadian Sharifabad, MD [Citation ends].

May also demonstrate complications of COPD, such as pneumonia and pneumothorax.

Result

hyperinflation

FBC

Test
Result
Test

This test may be considered to assess severity of an exacerbation and may show polycythaemia (haematocrit >55%), anaemia, and leucocytosis. [1]

Result

raised haematocrit, possible increased WBC count

ECG

Test
Result
Test

Risk factors for COPD are similar to those for ischaemic heart disease, so comorbidity is common.

Result

signs of right ventricular hypertrophy, arrhythmia, ischaemia

Investigations to consider

sputum culture

Test
Result
Test

In an acute exacerbation, empirical antibiotics should be given if the patient has three cardinal symptoms: increase in dyspnoea, sputum volume, and sputum purulence; or if the patient has two of the cardinal symptoms, if increased purulence of sputum is one of the two symptoms; or if the patient requires mechanical ventilation. In patients with frequent exacerbations, severe airflow limitation, and/or exacerbations requiring mechanical ventilation, sputum should be sent for culture. [1]

Result

infecting organism

pulmonary function tests

Test
Result
Test

Useful for resolving diagnostic uncertainties and preoperative assessment. [1] Requires specialist laboratory facilities.

Decreased diffusing capacity of the lung for carbon monoxide (DLCO) is supportive of emphysema over chronic bronchitis.

Result

obstructive pattern, decreased DLCO

chest CT scan

Test
Result
Test

Provides better visualisation of type and distribution of lung tissue damage and bulla formation than CXR. com.bmj.content.model.Caption@4b1cbbf9 [Figure caption and citation for the preceding image starts]: COPD chest CT: hyperinflated lung, emphysematous changes, and increased antero-posterior diameter (barrel chest) From the collection of Manoochehr Abadian Sharifabad, MD [Citation ends].

In contrast to smoking-related COPD, alpha-1 antitrypsin deficiency mainly affects lower fields.

Useful in excluding other underlying pulmonary disease and for pre-operative assessment.

Result

hyperinflation

alpha-1 antitrypsin level

Test
Result
Test

Low level in patients with alpha-1 antitrypsin deficiency. Test is done if there is high suspicion for alpha-1 antitrypsin deficiency, such as a positive family history and atypical COPD cases (young patients and non-smokers). The World Health Organization recommends that all patients with a diagnosis of COPD should be screened once, especially in areas with high prevalence of alpha-1 antitrypsin deficiency. [22]

Result

should be normal in patients with COPD

exercise testing

Test
Result
Test

Can be of value in patients with a disproportional degree of dyspnoea compared with spirometry. [24] It can be performed on a cycle or treadmill ergometer, or by a simple timed walking test (e.g., 6 minutes, or duration <6 minutes). [25] Exercise testing is of use in selecting patients for rehabilitation.

Result

poor exercise performance or exertional hypoxaemia is suggestive of advanced disease

sleep study

Test
Result
Test

Obstructive sleep apnoea, a common finding in patients with COPD, is associated with increased risk of death and hospitalisation in patients with COPD. [23]

Result

elevated apnoea-hypopnoea index and/or nocturnal hypoxaemia

respiratory muscle function

Test
Result
Test

Respiratory muscle function may be tested if dyspnoea or hypercapnia are disproportionately increased with respect to FEV1, as well as in patients with poor nutrition and those with corticosteroid myopathy. [26]

Result

reduced maximal inspiratory pressure

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