Chronic obstructive pulmonary disease

 Definitions  
COPD   is defined as a progressive disorder of airway obstruction ( decreased FEV 1 , decreased  FEV 1 /FVC) with little or no reversibility.
COPD includes chronic bronchitis (chronic cough with sputum production),  emphysema (destruction and expansion of alveolar air spaces), and  small airways disease (narrowing of the small bronchioles). Although airway hyperresponsiveness is characteristic of asthma, a percentage of individuals with COPD have airway hyperresponsiveness to external stimuli, infections, and, in some cases, to allergens.

COPD is favored by:
  Age of onset >35 yrs
  Smoking
  Chronic dyspnea
  Sputum production
  No marked diurnal or day-to-day FEV 1       variation.

Chronic bronchitis   is defined   clinically   as cough and sputum production on most days  for 3 months in 2 successive years. There is no increase in mortality if lung function is normal. Symptoms improve in 90% of patients if they stop smoking.

Emphysema   is defined   histologically   as enlargement of the air spaces distal to the terminal bronchioles, with destruction of the alveolar walls.

Prevalence   ~14 million in the United States.

COPD mortality:   126,000 deaths/yr in the United States.

Pink puffers and blue bloaters  

Pink puffers   have increased alveolar ventilation, a near normal  PaO2 , and a normal or low  PaCO2 . Patients have shortness of breath, yet maintain adequate ventilation without cyanosis. Blue bloaters  have decreased alveolar ventilation, with a low  PaO2  and a high PaCO2 . They can be cyanotic but usually are not breathless; may go on to develop cor pulmonale. Their respiratory centers are relatively insensitive to CO2 , and they rely on their hypoxic drive to maintain respiratory effort— supplemental oxygen should be given with care . Although the traditional differentiation of pink puffers versus blue bloaters suggests that pink puffers have emphysema and blue bloaters have chronic bronchitis, more recent clinical studies show elements of both are present in COPD, and physiological/physical differentiation is no longer relevant.

Clinical features

Symptoms:  Cough, sputum, dyspnea, and wheeze.

Signs: Tachypnea, use of accessory muscles of respiration, hyperinflation,   decreased  cricosternal distance (<3 cm),   decreased  expansion, resonant or hyperresonant percussion, quiet breath sounds (e.g., over bullae), wheeze, cyanosis, cor pulmonale.

Complications:   Acute exacerbations ± infection, polycythemia, respiratory failure, cor pulmonale (edema, JVP increased ), pneumothorax (ruptured bullae), lung cancer.

Tests
CBC: PCV  increased.
CXR:  Hyperinflation (>6 anterior ribs seen above diaphragm in mid-clavicular line), flat hemidiaphragms, large central pulmonary arteries,   decreased  peripheral vascular markings, bullae.   ECG:   Right atrial and ventricular hypertrophy (cor pulmonale).
ABG: PaO2 decreased   ± hypercapnia. Lung function: Obstructive + air trapping (FEV 1   <80% of predicted, FEV 1 /FVC ratio <70%, TLC increased  , RV increased  , DLCO decreased  in emphysema).