Chest radiography: Almost always normal in patients with asthma. It is recommended in the evaluation of severe or difficult-to-control asthma and for the detection of comorbid conditions (e.g., allergic bronchopulmonary aspergillosis, eosinophilic pneumonia, or atelectasis due to mucous plugging).
Hematology: CBC with differential WBC analysis to screen for eosinophilia or significant anemia may be helpful in certain cases. Markedly elevated eosinophil percentages (>15%) may be due to allergic asthma but should prompt consideration of alternative diagnoses, including parasitic infections, drug reactions, and syndromes of pulmonary infiltrates with eosinophilia. An alpha-1 antitrypsin level is recommended in nonsmokers with persistent and irreversible airflow obstruction to exclude emphysema due to alpha-1 antitrypsin deficiency.
Allergy tests: Allergic sensitivity to specific allergens can be assessed by either skin tests or blood tests for allergen-specific IgE. Aeroallergens (house dust mite, cat or dog dander, cockroach, pollen, and mold spore antigens) are most commonly implicated in asthma. Food allergens rarely cause isolated asthmatic symptoms. Total IgE levels are sometimes helpful. A very high level (>1,000 IU/mL) suggests the associated conditions of eczema or allergic bronchopulmonary aspergillosis.
Suggested Reading
National Asthma Education and Prevention Program: Expert Panel Report III: Guidelines for the Diagnosis and Management of Asthma
. Bethesda, MD: National Heart, Lung, and Blood Institute, 2007. (NIH publication no. 08–4051): Full text available online:
www.nhlbi.nih.gov/guidelines/asthma/asthgdln.htm
.
CARDIAC HEART FAILURE
See Chapter
3
, Cardiovascular Disorders.
CHRONIC OBSTRUCTIVE PULMONARY DISEASE
Definition
Chronic bronchitis with emphysema, also known as chronic obstructive pulmonary disease (COPD), is in most cases a sequel of many years of active smoking. It refers to a group of diseases that cause airflow blockage and breathing-related problems. COPD results from complex interactions between clinical and genetic risk factors. Definite or possible risk factors for COPD include inhalational exposure (e.g., smoking), increased airway responsiveness, atopy, and antioxidant deficiency. Genetic risk factors for COPD include a variety of gene polymorphisms, antioxidant-related enzyme dysfunction, metalloproteinase dysregulation, and abnormalities that cause excess elastase.
The Global Initiative for Chronic Obstructive Lung Disease (GOLD)—a report produced by the National Heart, Lung, and Blood Institute (NHLBI) and the World Health Organization (WHO)—defines COPD as “a preventable and treatable disease with some significant extrapulmonary effects that may contribute to the severity in individual patients. Its pulmonary component is characterized by airflow limitation that is not fully reversible. The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases.”
Classification of severity of COPD.
An FEV
1
/FVC <
70% indicates airflow limitation and the possibility of COPD
.
Stage 0
—at risk: normal spirometry; chronic symptoms (cough, sputum production); FEV
1
/FVC <70%.
Stage I
—mild: with or without chronic symptoms (cough, sputum production); mild airflow limitation (FEV
1
/FVC
1
>80% predicted).
Stage II
—moderate: Worsening airflow limitation (FEV
1
/FVC <70%; 50% < FEV
1
<80% predicted), with shortness of breath typically developing during exertion.
