COPD

Question 1

COPD definition

Answer 1

• A systemic disease (!)
• Characterized by airflow limitation that is not fully reversible
• Progressive and associated w/ abnormal inflammatory response of the lung to noxious particles/gases
• Chronic bronchitis: productive cough for 3 mo in 2 consecutive years
• Emphysema: permanent destructive enlargement of airspaces distal to terminal bronchioles accompanied by loss of alveolar attachments
• Small airway disease: inflammation and narrowing of the peripheral airways

Question 2

Risk factors for COPD

Answer 2

• Tobacco smoke
• Second hand smoke (passive smoking)
• Ambient air pollution
• Hyperresponsive airways: asthma may progress to COPD due to remodeling of airways
• Higher prevalence in men
• Ocupational exposures
• Bacterial infections (H influenzae and chlamydia pneumoniae important)

Question 3

Genetic factors of COPD

Answer 3

• COPD only developing in a minority of heavy smokers (10-20%)
• A1 AT deficiency associated w/ lower lobe, pan lobular emphysema
• 95% of people w/ A1 AT def are homozygous for Z allele (PiZZ)
• Cytokines (TNF a, IL 8) and MMPs cause elastolytic destruction of alveoli and contribute to development of COPD

Question 4

Clinical characteristics

Answer 4

• Hx: smoking, cough w/ mucous production (usually in acute exacerbations), possibly fevers, chills, sweats, usually have dyspnea
• Ventilatory limitations: hyperinflation, dead-space ventilation, CO2 retention, lactic acidosis
• Gas exchange limitations: hypoxemia, hypercapnia, lactic acidosis
• Cardiac dysfxn: right ventricular hypertrophy, co pulmonale (R sided HF due to pulmonary HTN), LV failure
• Skeletal muscle dysfxn due to deconditioning, oxidative stress, systemic inflammation, hypoxemia, chronic steroid use, weight loss
• Resp muscle dysfxn: from chronic overload and hyperinflation (diaphragm gets flatter)

Question 5

COPD as a systemic disease

Answer 5

• Increased frequency of respiratory illness
• May experience wheezing, dyspnea
• Hyperinflated lungs, severe airflow restriction, and relatively normal blood gases at first
• Emphysema: there is relatively normal V/Q matching (both are decreased), since the ratio remains equal the A-a gradient is normal
• Bronchitis: V decreases more than Q, thus V/Q ratio decreases and the A-a gradient is widened

Question 6

Physical exam of COPD

Answer 6

• Thin, underweight, barrel chest
• Prolonged expiration, pursed lips (emphysema)
• Decreased breath sounds, hyper resonance to percussion (hyper inflated lungs)
• Use of accessory muscles to respire

Question 7

Diagnostic findings

Answer 7

• CXR: hyperinflation, flat, depressed diaphragms, increased space behind sternum
• PFTs: Decrease in FEV and FVC, w/ the FEV/FVC ratio being less than .7
• No response to bronchodilators (if there is its asthma)
• Flow volume curve: downward expiratory concavity, indicating expiratory flow problem
• TLC, RV both increased
• DLCO is decreased in emphysema (destruction of alveoli), normal or slightly high in asthma (air trapping but no alveolar destruction), and increased in chronic bronchitis (increased hematocrit)
• Arterial blood gases: hypoxemia (increases risk of pulm HTN and cor pulmonale), and hypercapnia

Question 8

Complications of COPD

Answer 8

• Decline in COPD pts related to progressive reduction in FEV1 leading to respiratory failure
• Exacerbations associated w/ airway inflammation and physiologic deterioration
• Complications include: hypoxic pulm HTN-> cor pulmonale (R HF due to pulm HTN), frequent repiratory tract infections, weight loss, loss of appetite, respiratory failure

Question 9

Principles of management

Answer 9

• Chronic O2 therapy (maintain PaO2 above 55)
• Bronchodilators give a little relief
• Phosphodiesterase inhibitors relax airways and have anti-inflammatory effects
• Corticosteroids during acute exacerbations
• Antibiotics
• Pulmonary rehab and good nutrition

Question 10

Flow volume curves 1

Answer 10

• Emphysema: curve is shifted far to the left (larger lung volumes due to air trapping), peak expiratory flow reduced, most important: extreme downward concavity
• Asthma: curve is shifted slightly to the left (slightly increased lung volumes), peak expiratory flow reduced, slight downward concavity
• Asthma looks like emphysema curve but not as shifted to the left and concavity not as extreme
• Restrictive diseases: curve is shifted to right (decreased lung volumes), narrow base (VC), and decreased peaks w/ intact flow curve
• Shape is same as normal, but its more compressed and shifted to the right

Question 11

Flow volume curves 2

Answer 11

• Variable intrathoracic obstruction: flattening of expiratory limb w/ semi-intact inspiratory limb (slight flattening near end of expiration), slightly narrow base
• Can be due to mucus plug, tumor pressing on bronchi
• Variable extrathoracic obstruction: inspiratory limb greatly eliminated but expiratory limb intact
• Due to paralyzed vocal cord (outside chest: inspiration is limited, inside chest: expiration is limited)
• Fixed obstruction: both inspiratory and expiratory limbs are greatly reduced
• Due to damage to trachea, subglotic stenosis