Name of the Procedure:

Inhalation Bronchial Challenge Testing
(Also known as Methacholine Challenge Test, Histamine Challenge Test)

Summary

Inhalation Bronchial Challenge Testing involves inhaling a mist containing histamine, methacholine, or similar compounds to assess hyperreactivity of the bronchial tubes. This helps diagnose conditions like asthma.

Purpose

The procedure identifies bronchial hyperresponsiveness, which is indicative of asthma. It helps confirm or rule out asthma, gauge severity, and monitor response to treatment.

Indications

• Symptoms of asthma (wheezing, coughing, shortness of breath)
• Unexplained respiratory symptoms
• Assessing asthma control or severity
• Pre-employment or pre-enrollment evaluations for certain professions or activities

Preparation

• Avoid using bronchodilators and other specific respiratory medications as directed by the physician prior to the test.
• Refrain from smoking and rigorous exercise on the day of the test.
• Inform the healthcare provider about any existing respiratory conditions or infections.
• No fasting is required.

Procedure Description

1. The patient performs baseline pulmonary function tests (PFTs) to measure lung function.
2. The patient inhales increasing concentrations of methacholine or histamine via a nebulizer.
3. After each dose, pulmonary function tests are repeated to measure any changes in lung function.
4. The process continues until a significant change in lung function occurs, or the test reaches the maximum allowable dose.
5. Bronchodilators may be administered at the end of the test to reverse any bronchoconstriction.

Duration

Approximately 1–2 hours, including preparation and recovery time.

Setting

Performed in a pulmonary function lab, hospital, or outpatient clinic equipped with the necessary monitoring devices.

Personnel

• Pulmonologist or respiratory specialist
• Respiratory therapist
• Nurses or medical technicians to assist with monitoring and care

Risks and Complications

• Temporary bronchoconstriction leading to difficulty breathing, coughing, or wheezing
• Rarely, severe asthma attack requiring emergency treatment
• Mild side effects from the compounds, such as throat irritation or headache

Benefits

• Accurate diagnosis of bronchial hyperreactivity and asthma
• Helps tailor appropriate asthma treatment plans
• Can prevent misdiagnosis and unnecessary treatment

Recovery

• Normal activities can typically be resumed immediately after the test.
• Patients may experience mild, temporary symptoms (wheezing, shortness of breath) which usually resolve with the use of a bronchodilator.
• Follow-up instructions are provided, and further appointments may be scheduled based on the results.

Alternatives

• Peak flow monitoring
• Spirometry without challenge testing
• Exhaled nitric oxide measurement
• Each alternative offers differing sensitivity and specificity for diagnosing asthma; the choice can depend on patient-specific factors.

Patient Experience

During the test, patients may experience mild to moderate shortness of breath or wheezing, which should be temporary. Discomfort is usually minimal, and bronchodilators are available to alleviate symptoms if they occur. Post-test, patients typically return to their daily routines quickly.