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Refractory period during provocation with eucapnic hyperventilation and methacholine

K M Hurwitz1, J M Roach, G J Argyros

  • 1Department of Medicine, Walter Reed Army Medical Center, Washington, D.C. 20307-5001.

American Journal of Respiratory and Critical Care Medicine
|June 1, 1994
PubMed
Summary
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Methacholine inhalation challenge (MIC) reduces the bronchoconstriction response to eucapnic voluntary hyperventilation (EVH) in asthma patients. EVH may also blunt subsequent MIC responses in highly sensitive individuals.

Area of Science:

  • Pulmonology
  • Respiratory Medicine
  • Clinical Immunology

Background:

  • Eucapnic voluntary hyperventilation (EVH) and methacholine inhalation challenge (MIC) are common methods to induce bronchoconstriction in asthma.
  • Refractory periods are known after hyperventilation or exercise but not typically after MIC.

Purpose of the Study:

  • To investigate if EVH or MIC can induce a refractory period, thereby blunting the response to the other challenge in asthmatic patients.

Main Methods:

  • Sixteen asthmatic patients underwent both EVH and MIC on separate days.
  • The order of the challenges was randomized (EVH then MIC, or MIC then EVH).
  • Bronchoconstriction was measured by the decline in FEV1 and the provocation dose (PD20) for methacholine.

Related Experiment Videos

Main Results:

  • MIC significantly attenuated the bronchoconstrictor response to a subsequent EVH challenge (30% reduction in FEV1 decline, p=0.0026).
  • EVH showed a trend towards blunting the MIC response, particularly in patients highly sensitive to methacholine (PD20 increased significantly, p=0.069).

Conclusions:

  • Methacholine inhalation challenge can induce a refractory period affecting subsequent eucapnic voluntary hyperventilation response.
  • Eucapnic voluntary hyperventilation may also induce refractoriness to methacholine, especially in the most sensitive asthma patients.