Final answer:
The Methacholine challenge test involves inhaling increasing concentrations of methacholine to measure airway responsiveness and to diagnose asthma, with spirometry tests conducted after each dosage.
Step-by-step explanation:
The Methacholine challenge test is performed to assess airway hyperresponsiveness and diagnose conditions like asthma. This test is particularly useful when standard pulmonary function tests are inconclusive. The procedure includes the following steps:
- The patient inhales increasing concentrations of methacholine aerosol, which is a substance that can cause airway constriction.
- A spirometry test is carried out after each inhalation to measure the effect on lung function.
- The goal is to determine if and at what concentration the patient's airways react by narrowing. This is indicated by a decrease of at least 20% in FEV1 (Forced Expiratory Volume in one second).
Throughout this process, the patient is monitored closely for any signs of respiratory distress, and bronchodilators are available to reverse the effects of methacholine if necessary.