Methacholine inhalation is a diagnostic test used to assess airway hyperresponsiveness or the likelihood of having asthma. It involves inhaling a methacholine solution to stimulate the airways and evaluate their response.

Methacholine is a bronchoconstrictor, meaning it causes the airways to narrow. During the test, gradually increasing concentrations of methacholine are inhaled through a nebulizer. Spirometry measurements are taken before and after each inhalation to evaluate the level of bronchoconstriction.

Methacholine inhalation is performed to assess airway hyperresponsiveness, which is commonly associated with asthma. The test helps in diagnosing asthma, determining the severity of the condition, and monitoring its progression or response to treatment.

Methacholine inhalation is usually performed in a controlled medical setting, such as a doctor's office or respiratory lab. The patient breathes in increasing doses of methacholine through a nebulizer while spirometry readings are taken periodically. The test is stopped once a certain level of bronchoconstriction is reached, or if sufficient evidence of airway hyperresponsiveness has been obtained.

Methacholine inhalation is generally safe, but some individuals may experience temporary bronchoconstriction during the test. Common side effects include coughing, wheezing, shortness of breath, headache, and throat irritation. These effects typically resolve within a short period after the test.

The duration of the test varies depending on the patient's response. It usually takes about 30 to 60 minutes to complete.

Specific instructions regarding asthma medications may vary, but in general, it's advisable to avoid using short-acting bronchodilators (rescue inhalers) for a few hours before the test. Long-acting bronchodilators (controller medications) may need to be stopped for a specific period before the test, as advised by your healthcare provider.

Methacholine inhalation has a high sensitivity in diagnosing airway hyperresponsiveness associated with asthma. However, it is not entirely specific to asthma as other respiratory conditions may also cause bronchoconstriction. Additional tests and clinical evaluation are required for a definitive diagnosis.

Yes, children can undergo methacholine inhalation testing. However, age-specific protocols and considerations are taken into account to ensure the safety and accuracy of the test in pediatric patients.