Emphysema Workup

Updated: Aug 31, 2016
  • Author: Kamran Boka, MD, MS; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Workup

Laboratory Studies

The following laboratory studies are useful:

  • Arterial blood gas analysis: Patients with mild chronic obstructive pulmonary disease (COPD) have mild-to-moderate hypoxemia without hypercapnia. As the disease progresses, hypoxemia worsens and hypercapnia develops.
  • Hematocrit: Chronic hypoxemia may lead to polycythemia. A hematocrit value higher than 52% in men and higher than 47% in women is indicative of the condition. Patients should be evaluated for hypoxemia at four times: at rest, with ambulation, with exertion, and during sleep. Correction of hypoxemia should reduce secondary polycythemia in patients who have quit smoking.
  • Serum bicarbonate: Chronic respiratory acidosis leads to compensatory metabolic alkalosis. In the absence of blood gas measurements, serum bicarbonate levels are useful for following disease progression.
  • Serum alpha1-antitrypsin: Of the approximately 75 different alleles for alpha1-antitrypsin (AAT) deficiency variants, 10-15 are associated with serum levels below the protective threshold of 11 mmol/L. The most common severe variant is the Z allele, which accounts for 95% of the clinically recognized cases of severe AAT deficiency. The diagnosis of severe AAT deficiency is confirmed when the serum level falls below the protective threshold value (ie, 3-7 mmol/L). Specific phenotyping is reserved for patients in whom serum levels are 7-11 mmol/L or when genetic counseling or family analysis is needed.
  • Sputum evaluation: In patients with stable chronic bronchitis and in emphysema, the sputum is mucoid and the predominant cells are macrophages. With an exacerbation, the sputum becomes purulent, with excessive neutrophils and a mixture of organisms visualized through Gram staining. Streptococcus pneumoniae and Haemophilus influenzae are pathogens frequently cultured during exacerbations.
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Imaging Studies

Chest radiograph

Frontal and lateral chest radiographs reveal signs of hyperinflation: flattening ("coving") of diaphragms, increased retrosternal air space (see on lateral chest films), and a long narrow heart shadow. Rapid tapering vascular shadows accompanied by hyperlucency of the lungs are signs of emphysema. With complicating pulmonary hypertension, the hilar vascular shadows become prominent; right ventricular enlargement and an opacity in the lower retrosternal air space may also occur.

Note the images below.

Chest radiograph shows hyperinflation, flattened d Chest radiograph shows hyperinflation, flattened diaphragms, increased retrosternal space, and hyperlucency of the lung parenchyma in emphysema.
An emphysematous lung shows increased anteroposter An emphysematous lung shows increased anteroposterior (AP) diameter, increased retrosternal airspace, and flattened diaphragms on posteroanterior (PA) film.
An emphysematous lung shows increased anteroposter An emphysematous lung shows increased anteroposterior (AP) diameter, increased retrosternal airspace, and flattened diaphragms on lateral chest radiograph.
The differential diagnosis of unilateral hyperluce The differential diagnosis of unilateral hyperlucent lung includes pulmonary arterial hypoplasia and Swyer-James syndrome. The expiratory chest radiograph exhibits evidence of air trapping and is helpful in making the diagnosis. Swyer-James syndrome is unilateral bronchiolitis obliterans, which develops during early childhood.
Lateral chest radiograph of Swyer-James syndrome m Lateral chest radiograph of Swyer-James syndrome may demonstrate some of the features of emphysema.

CT scan

High-resolution CT (HRCT) scanning is more sensitive than standard chest radiography. HRCT scanning is highly specific for diagnosing emphysema and outlines bullae that are not always observed on radiographs. A CT scan is indicated when the patient is being considered for a surgical intervention such as bullectomy or lung-volume reduction surgery. A CT scan is not indicated in the routine care of patients with COPD.

Note the images below.

A CT scan shows emphysematous bullae in upper lobe A CT scan shows emphysematous bullae in upper lobes.
Diffuse emphysema secondary to cigarette smoking. Diffuse emphysema secondary to cigarette smoking.
A CT scan showing severe emphysema and bullous dis A CT scan showing severe emphysema and bullous disease.
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Other Tests

Pulmonary function tests

These measurements are necessary for the diagnosis of obstructive airway disease and for assessments of its severity. In addition, spirometry is helpful for assessing responses to treatment and disease progression.

Forced expiratory volume in 1 second (FEV1) is a reproducible test and is the most common index of airflow obstruction. Lung volume measurements show an increase in total lung capacity, functional residual capacity, and residual volume. The vital capacity is decreased.

DLCO is decreased in proportion to the severity of emphysema.

Lung mechanics and gas exchange worsen during acute exacerbations.

As many as 30% of patients have an increase in FEV1 of 15% or more after inhalation of a bronchodilator. The absence of bronchodilator response does not justify withholding bronchodilator therapy. Studies have shown that most patients with emphysema and COPD will have a small but significant degree of reversibility of airflow obstruction (defined as 12% and at least 200 mL improvement in the FEV1).

Note the images below.

Pressure-volume curve is drawn for a patient with Pressure-volume curve is drawn for a patient with restrictive lung disease and obstructive disease and is compared to healthy lungs.
Flow-volume curve of lungs with emphysema shows ma Flow-volume curve of lungs with emphysema shows marked decrease in expiratory flows, hyperinflation, and air trapping (patient B) compared to a patient with restrictive lung disease, who has reduced lung volumes and preserved flows (patient A).
Forced expiratory volume in 1 second (FEV1) can be Forced expiratory volume in 1 second (FEV1) can be used to evaluate the prognosis in patients with emphysema. The benefit of smoking cessation is shown here because the deterioration in lung function parallels that of a nonsmoker, even in late stages of the disease.
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Staging

The FEV1 is used to stage the severity of COPD. It is normalized as a percentage of predicted for healthy controls. The following Global Initiative for Chronic Obstructive Lung Disease staging system is widely used (note that the postbronchodilator FEV1 is used):

  • Stage I (mild) - FEV 1 of 80% or more of predicted
  • Stage II (moderate) - FEV 1 of less than 80% and 50% or more of predicted
  • Stage III (severe) - FEV 1 less than 50% and 30% or more of predicted
  • Stage IV (very severe) - FEV 1 less than 30% of predicted or FEV 1 less than 50% and chronic respiratory failure

Respiratory failure is defined as a PaO2 less than 60 mm Hg (kPa 8.0) or a PaCO2 higher than 50 mm Hg (kPa 6.7).

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