Investigations

1st investigations to order

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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.[18]

Result

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

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Result
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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

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Result
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Checked in patients who are acutely sick, 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

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Result
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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@5708dc7b[Figure caption and citation for the preceding image starts]: COPD chest x-ray (AP view): hyperinflated lung, flattened diaphragm, increased intercostal spacesFrom the collection of Manoochehr Abadian Sharifabad, MD [Citation ends].com.bmj.content.model.Caption@1417a5aa[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 viewFrom the collection of Manoochehr Abadian Sharifabad, MD [Citation ends].

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

Result

hyperinflation

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Result
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This test may be considered to assess severity of an exacerbation and may show polycythemia (hematocrit >55%), anemia, and leukocytosis.[1]

Result

elevated hematocrit, possible increased WBC count

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

Result

signs of right ventricular hypertrophy, arrhythmia, ischemia

Investigations to consider

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Result
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Useful for resolving diagnostic uncertainties and for 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

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Result
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Provides better visualization of type and distribution of lung tissue damage and bulla formation than CXR. com.bmj.content.model.Caption@4640d339[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 in preoperative assessment.

Result

hyperinflation

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Result
Test

In patients with frequent exacerbations, severe airflow limitation, and/or exacerbations requiring mechanical ventilation, sputum should be sent for culture.[1]

Result

infecting organism

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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 nonsmokers). 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.[19]

Result

should be normal in patients with COPD

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Result
Test

Can be of value in patients with a disproportional degree of dyspnea compared with spirometry.[21] 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).[22] Exercise testing is of use in selecting patients for rehabilitation.

Result

poor exercise performance or exertional hypoxemia is suggestive of advanced disease

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Result
Test

Obstructive sleep apnea, a common finding in patients with COPD, is associated with increased risk of death and hospitalization in patients with COPD.[20]

Result

elevated apnea-hypopnea index and/or nocturnal hypoxemia

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Result
Test

Respiratory muscle function may be tested if dyspnea or hypercapnia are disproportionately increased with respect to FEV1, as well as in patients with poor nutrition and those with corticosteroid myopathy.[23]

Result

reduced maximal inspiratory pressure

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