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C Laboratory
evaluation
1. CBC: Polycythemia may be
indication of chronic hypoxemia or nocturnal desaturation. Elevated WBC during
acute respiratory
insufficiency may be an indication of bacterial infection
2. Pulmonary function tests:
Spirometry to assess severity
of obstruction. Lung volumes to determine presence of air trapping (the helium
dilution technique may underestimate lung volumes in the presence of severe
bullous emphysema; may need to use body plethysmography). Diffusing capacity to
assess degree of destruction of alveolar capillary surface area. May provide
clue that patient will desaturate with activity. Patients with low DLCO are more
likely to desaturate. Flow-volume loop to help distinguish emphysema from
asthma. In asthmatic, the flows are reduced at all lung volumes; in emphysema
there is expiratory coring indicative of collapse of airways or unequal emptying
of different parts of the lung variably affected by the emphysema.
3. Chest x-ray; computerized
tomography CXR: presence of hyperinflation (retrosternal clear space, flat
diaphragm, AP diameter); localization of bullous disease to distinguish
classical emphysema (upper zones) from alpha-1-antitrypsin deficiency (basilar
disease). CT scan is not utilized on routine basis. It is more sensitive at
assessing the degree of bullous disease than chest x-ray; necessary if
contemplating volume reduction surgery/bullectomy (need to assess whether
bullous disease is homogeneous or heterogeneous and status of remaining lung).
4. Oximetry: Determine whether
patient is hypoxemic at rest and with exercise. Necessary for justifying
supplemental oxygen (or can use arterial blood gas, but ABG does not lend itself
to exercise assessment)
IV. Management Issues
Education
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