Name of the Procedure:

Methacholine Chloride Inhalation Test (MCT) or Methacholine Challenge Test

Summary

The Methacholine Chloride Inhalation Test involves inhaling a nebulized solution of methacholine chloride to test lung function. Methacholine causes the airways to constrict, and responses are measured to diagnose conditions like asthma.

Purpose

This procedure is primarily used to diagnose asthma by assessing how responsive a person’s airways are to methacholine. It helps in identifying bronchial hyperreactivity, which is indicative of asthma.

Indications

• Persistent cough
• Difficulty breathing
• Wheezing episodes not explained by other causes
• Suspected asthma or hyperreactive airway conditions
• Normal spirometry but with asthma symptoms

Preparation

• Avoid caffeine, smoking, and certain medications (e.g., bronchodilators) for a specified period before the test.
• Engage in light meals to avoid a full stomach.
• Wear comfortable clothing.
• Perform baseline spirometry to assess pre-test lung function.

Procedure Description

1. Baseline spirometry is performed.
2. The patient inhales increasing doses of methacholine via a nebulizer under controlled conditions.
3. After each dose, spirometry is conducted to measure lung function.
4. The procedure continues until a significant drop in lung function is detected or the maximum dose is reached.
5. A bronchodilator may be administered if airway constriction occurs, to open the airways and reverse symptoms.

Duration

The entire test typically takes 1-2 hours, including preparation, administration, and post-test monitoring.

Setting

The procedure is conducted in a pulmonary function lab within a hospital or outpatient clinic.

Personnel

• Respiratory therapists
• Pulmonologists
• Nurses
• Technicians specializing in pulmonary function testing

Risks and Complications

• Minor discomfort or throat irritation from inhaling the solution
• Shortness of breath, coughing, or wheezing
• Rarely, severe bronchospasm requiring immediate treatment with a bronchodilator

Benefits

• Accurate diagnosis of asthma and other reactive airway conditions
• Improved management of respiratory symptoms
• Personalized treatment plans based on specific airway hyperreactivity

Recovery

• Immediate recovery is expected after administration of a bronchodilator if needed.
• Patients can typically resume normal activities shortly after the test.
• Follow-up appointments may be scheduled to discuss results and treatment strategies.

Alternatives

• Exercise-induced bronchoconstriction test
• Exhaled nitric oxide measurements
• Histamine challenge test
• Direct observation and trial treatment with bronchodilators and corticosteroids These alternatives vary in their diagnostic accuracy and applicability depending on the patient’s specific condition.

Patient Experience

During the test, patients might experience mild to moderate respiratory discomfort, similar to asthma symptoms. Healthcare providers will ensure comfort and safety, managing any adverse reactions promptly. The sensation of breathlessness or tightness usually subsides quickly after the procedure, especially if a bronchodilator is used.