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Introduction ⬇

Bronchial provocation tests involve exposing the patient to specific triggers in order to identify bronchial hyperreactivity. Two types of bronchial provocation tests include the methacholine challenge and the histamine challenge. The asthmatic patient is more sensitive to the bronchoconstrictive effects of cholinergic agents (e.g., methacholine or histamine) than is the healthy person as observed on a spirometry test. Raw tests are also sensitive monitors of response to bronchoconstrictive agents. Spirometry measurements are obtained after administration of inhaled medication to measure airway constriction.

Procedure ⬆ ⬇

  1. Have the patient assume the seated position. Place nose clips on the nose and instruct the patient to breathe normally through a mouthpiece/filter (bacterial/viral) combination into the spirometer.

  2. Have the patient perform a forced expiratory maneuver and measure and record the baseline FEV1 (or Raw measurement).

  3. The patient will inhale increasing concentrations of methacholine chloride (0.062–16.00 mg/mL) or histamine by nebulizer. Repeat the FVC or Raw maneuver after each successive concentration is inhaled. A 20% reduction in the FEV1 (primary outcome variable) or 35% increase in Raw is considered a positive response.

  4. Administer an inhaled bronchodilator when or if a decrease of >20% from baseline is reached.

  5. If a patient goes through all dilution ratios and a 20% reduction in the FEV1 or >35% increase in Raw is not reached, the test is considered negative.

  6. Remember that if the methacholine causes no change, histamine testing may be ordered.

  7. See Chapter 1 for guidelines for intratest care.

Clinical Implications ⬆ ⬇

A positive response to methacholine or histamine is consistent with bronchial hyperreactivity. Approximately 5%–10% of asthmatic persons do not respond to the methacholine challenge test.

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain the purpose and procedure of the test and the need for patient cooperation. Assess the patient’s ability to follow verbal instructions.

  2. Withhold bronchodilators for 8 hours and antihistamines for 48 hours before testing, if tolerated.

  3. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Administer a bronchodilator, as ordered, to reverse the effects of bronchospasm triggered by administration of medication.

  2. Review test results; report and record findings. Modify the nursing care plan as needed.

  3. Explain the possible need for follow-up testing and treatment.

  4. If the test is positive, advise the patient to avoid antigens that may be causing hypersensitivity reactions and bronchospasms.

  5. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Clinical Alert

  1. Inhalation of methacholine can cause bronchospasm, chest pain, shortness of breath, and general discomfort.

  2. These effects can be reversed with a bronchodilator.

Reference Values ⬆

Normal