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Inhalation Challenge TestAka: Methacholine Challenge

See Also
Indication
1. Suspected Asthmatic disease
Contraindications
1. FEV1 <65% of predicted
Physiology
1. Tests airway reactivity to airway constrictors
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
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
References
1. Crapo (2000) Am J Respir Crit Care Med 161:309

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This page was written by Scott Moses, MD. This page was last revised before 5/10/08, prior to consistent tracking of revision date. This page was last published on 5/10/2008. Please send comments and questions to the editor. Contact information may be found on the page About the Family Practice Notebook. These pages are best viewed with Microsoft Internet Explorer 6.0.