Obstructive Lung Disease

Aka: Obstructive Lung Disease, Obstructive Lung Function, Asthma-COPD Overlap

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II. Causes

  1. Alpha-1-Antitrypsin Deficiency
  2. Asthma
  3. Bronchiectasis
  4. Bronchiolitis Obliterans
  5. Chronic Obstructive Pulmonary Disease
  6. Cystic Fibrosis
  7. Silicosis (early stages)

III. Diagnosis: Obstructive Lung Disease

  1. Criteria
    1. FEV1 to FVC Ratio <0.7 (or <LLN or for children<85% of predicted) AND
    2. Normal FVC or FVC response to Bronchodilator
  2. Approach
    1. Assess Severity
      1. See FEV1 interpretation above
    2. Assess Bronchodilator response
      1. Bronchodilator response with FEV1 or FVC increased >12% at any age (or >200 ml in adults)
        1. Consistent with reversible Obstructive Lung Disease (Asthma)
      2. Inadequate Bronchodilator response
        1. Consistent with irreversible Obstructive Lung Disease (COPD)

IV. Diagnosis: Asthma

  1. Spirometry
    1. Lung function tests may be normal without exacerbation (Intermittent Asthma, Exercise induced Asthma)
    2. FEV1 and FEV1/FVC ratio reduced
    3. FEV1 improves >12% or 200 ml after Bronchodilator
    4. Partially reversible airflow obstruction
    5. Peak Expiratory Flow >20% variation over 2 weeks
  2. Risk Factors
    1. Prematurity
    2. Tobacco Exposure
    3. Obesity
    4. Atopy (Asthma with Allergic Rhinitis and Eczema)
    5. Asthma Family History
  3. Symptoms
    1. Shortness of Breath
    2. Chest tightness
    3. Wheezing
    4. Variable cough

V. Diagnosis: Chronic Obstructive Pulmonary Disease (COPD)

  1. Spirometry
    1. Post-Bronchodilator FEV1 to FVC Ratio: 0.7
    2. Minimal reversibility with Bronchodilator (contrast with Asthma)
    3. DLCO diminished in Emphysema
    4. Increased Total Lung Capacity
    5. Increased Residual Volume
    6. Peak Flow <350 L/min
  2. Risk Factors
    1. Tobacco Abuse
    2. Alpha-1-Antitrypsin Deficiency
    3. Air pollutants (outdoor, indoor or Occupational Asthma)
  3. Symptoms
    1. Dyspnea
    2. Chronic Cough
    3. Recurrent lower respiratory tract infections

VI. Diagnosis: Asthma-COPD Overlap

  1. Background
    1. Not considered a distinct condition, but rather a patient with features shared between the 2 diagnoses
    2. Primarily managed as Asthma, with additional therapies considered from the COPD arsenal
    3. Those with persistent Asthma are much higher risk for developing COPD with aging (RR 12.5)
      1. Approximately 25% of COPD patients have a history of comorbid Asthma
      2. Silva (2004) Chest 126(1): 59-65 [PubMed]
      3. de Marco (2013) PloS One 8(5): e62985 [PubMed]
  2. Spirometry
    1. FEV1 and FEV1/FVC ratio persistently reduced despite Bronchodilator (as seen in COPD)
    2. FEV1 improves >12% or 200 ml after Bronchodilator (as seen in Asthma)

VII. References

  1. Johnson (2014) Am Fam Physician 89(5): 359-66 [PubMed]
  2. Zeller (2023) Am Fam Physician 107(3): 247-52 [PubMed]

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