COPD

Alternative names

COPD; Chronic obstructive airway disease; Chronic obstructive lung disease

Definition

Chronic obstructive pulmonary disease (COPD) is a group of lung diseases involving limited airflow and varying degrees of air sac enlargement, airway inflammation, and lung tissue destruction. Emphysema and chronic bronchitis are the most common forms of COPD.

Causes, incidence, and risk factors

The leading cause of COPD is smoking, which can lead to the two most common forms of this disease, emphysema and chronic bronchitis.

Prolonged tobacco use causes lung inflammation and variable degrees of air sac (alveoli) destruction. This leads to inflamed and narrowed airways (chronic bronchitis) or permanently enlarged air sacs of the lung with reduced lung elasticity (emphysema). Between 15% and 20% of long-term smokers will develop COPD.

Other risk factors for COPD are passive smoking (exposure of non-smokers to cigarette smoke from others), male gender, and working in a polluted environment. Rarely, an enzyme deficiency called alpha-1 anti-trypsin deficiency can cause emphysema in non-smokers.

Symptoms

• Shortness of breath (dyspnea) persisting for months to years
  
• Wheezing
  
• Decreased exercise tolerance
  
• Cough with or without phlegm
  

Signs and tests

An examination often reveals increased work involved in breathing: nasal flaring may be evident during air intake, and the lips may be pursed (the shape lips make when you whistle) while exhaling.

During a flare of disease, chest inspection reveals contraction of the muscles between the ribs during inhalation (intercostal retraction) and the use of accessory breathing muscles. The respiratory rate (amount of breaths per minute) may be elevated, and wheezing may be heard through a stethoscope.

A chest X-ray can show an over-expanded lung (hyperinflation), and a chest CT scan may show emphysema.

A sample of blood taken from an artery (arterial blood gas) can show low levels of oxygen (hypoxemia) and high levels of carbon dioxide (respiratory acidosis). Pulmonary function tests show decreased airflow rates while exhaling and over-expanded lungs.

Treatment

Treatment for COPD includes inhalers that dilate the airways (bronchodilators) and sometimes theophylline. The COPD patient must stop smoking. In some cases inhaled steroids are used to suppress lung inflammation, and, in severe cases or flare-ups, intravenous or oral steroids are given.