Asthma affects 3% to 5% of the U.S. population.

Asthma is a chronic, episodic disease of the airways with protean manifestations and is best viewed as a syndrome. Important features of this syndrome include the following:

Asthma treatment has four key components:

The most objective indicator of asthma severity is the measurement of airflow obstruction by spirometry or peak expiratory flow, although spirometry is preferred.

Spirometry in an asthmatic typically shows obstructive airway disease with reduced expiratory flows [reduced FEV₁/forced vital capacity (FVC) ratio] that improve on administration of bronchodilator therapy; lack of 12% or more bronchodilator response does not rule out asthma.

An estimated 24 million Americans are afflicted with chronic obstructive pulmonary disease (COPD).

The Global Initiative for Chronic Obstructive Lung Disease (GOLD) report defines COPD as “a disease state characterized by airflow limitation that is not fully reversible. The airflow limitation is usually both progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases.”

Recent studies identify a composite index combining Body mass index, airflow Obstruction, Dyspnea, and Exercise capacity (the BODE index), as well as the inspiratory capacity-to-total lung capacity ratio, as better than the forced expiratory volume in 1 second in predicting the risk of death in COPD.

Although smoking is the single most important risk factor for COPD, about 15% to 20% of cases occur in neversmokers.

Severe deficiency of alpha-1 antitrypsin accounts for emphysema in approximately 2% to 3% of adult COPD patients.

Pulmonary function testing is essential to establish a diagnosis of COPD and its severity.

The typical spirometric abnormalities in COPD consist of a reduction in the FEV₁ and in the ratio of the FEV₁ to the FVC.

The single-breath diffusing capacity for carbon monoxide is usually reduced in emphysema.

Commonly used therapy for stable COPD includes

The only interventions that have been shown to prolong survival and affect the natural history of COPD are limited oxygen therapy (continuous or nocturnal) for the chronically hypoxemic patient and smoking cessation.

In certain patients, noninvasive positive-pressure ventilation (NPPV) is successful for preventing endotracheal intubation, reversing hypercapnia, and reducing mortality and hospitalization in acute exacerbations of COPD (AECOPD).

In appropriately selected patients with COPD, lung volume reduction surgery (LVRS) has been shown to increase survival, health-related quality of life, and exercise capacity.