Pulmonology Book

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Inhalation Challenge Test

Aka: Inhalation Challenge Test, Methacholine Challenge
  1. See Also
    1. Pulmonary Function Test
    2. Lung Volumes
    3. Diffusing Capacity
  2. Indication
    1. Suspected Asthmatic disease
  3. Contraindications
    1. FEV1 <65% of predicted
  4. Physiology
    1. Tests airway reactivity to airway constrictors
  5. Technique
    1. Equipment to treat Status Asthmaticus readily available
    2. Pulmonary Function Tests performed at baseline
    3. Exposure to airway constrictor or irritant
      1. Methacholine (most common)
      2. Histamine
      3. Cold Air
      4. Hypertonic mist or hypotonic mist
    4. Pulmonary Function Tests repeated after exposure
  6. Interpretation
    1. Negative test suggests Asthma not present
    2. Positive test: 20% decline in FEV1 after exposure
      1. False positive in 8% of normal patients
      2. Asthma
      3. Emphysema
      4. Bronchiectasis
      5. Cystic Fibrosis
  7. References
    1. Crapo (2000) Am J Respir Crit Care Med 161:309-29

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