histamine inhalation test

The histamine inhalation test is one of the bronchial drug challenge tests. Inhalation of bioactive mediator histamine by nebulization directly stimulates bronchial smooth muscle contraction, and also stimulates cholinergic nerve endings, reflexively causes smooth muscle contraction, leading to bronchospasm, and then using lung function indicators to determine the degree of bronchoconstriction, The reactivity was measured. Basic Information Specialist Category: Respiratory Examination Category: Other Inspections Applicable gender: whether men and women apply fasting: not fasting Analysis results: Below normal: Normal value: no Above normal: negative: Negative excludes asthma Positive: The positive result of this test indicates the diagnosis of bronchial asthma, histamine PC20FEV18mg/ml, PD20FEV17.8μmol is positive. Tips: Inappropriate crowd: 1. Severe airway obstruction, asthma attack. 2. Hypertension, coronary heart disease, hyperthyroidism, pregnancy, cardiopulmonary dysfunction. Normal value The test was negative. Clinical significance 1. To diagnose diseases with increased airway responsiveness, the positive results of this test indicate the diagnosis of bronchial asthma, while the negative excludes asthma. 2. Evaluation of the efficacy of bronchodilator drugs. 3. Chronic bronchitis, emphysema, airway responsiveness has a certain degree of increase. 4. Allergic rhinitis, airway responsiveness between normal and asthma. Abnormal results bronchial asthma, chronic bronchitis, emphysema, allergic rhinitis. People who need to check: 1. Patients with asthma without typical symptoms, or suspected asthma, need to be tested. 2. In the course of asthma treatment, airway responsiveness needs to be measured to guide the drug users. 3. In the study of the pathogenesis of asthma, airway responsiveness cases need to be determined. Precautions Pre-inspection contraindications: This test has certain risks. Doctors with clinical experience should be present during the experiment, and emergency medicines such as β2-receptor stimulant inhaler, 0.1% epinephrine for injection, oxygen and infusion equipment should be available. Requirements for examination: The drug inhaled during the test starts from a small dose and gradually increases the dose. The quality of the test shall be controlled, and the instrument and measurement method shall be standardized. Repeat the test should be done at the same time each day. Inspection process 1. tidal breathing method (continuous inhalation method): (1) Preparation of reagent: Histamine was diluted with physiological saline, diluted in a concentration of 0.03 mg/ml to 16 mg/ml, and diluted at 4 ° C for use. It should be placed at room temperature for 30 minutes before use. (2) Prepare test equipment, equipment, and rescue equipment and medicines. Subjects discontinued bronchodilators before the test, theophylline, β2-receptor or anticholinergic drugs were stopped for 12 hours, antihistamines were stopped for 48 hours, corticosteroids were orally discontinued for 24 hours, and inhalation therapy was stopped for 12 hours. (3) The subject wears a perforated mask and is connected with the nebulizer outlet. The inlet of the nebulizer should be connected with a compressed air pump or an oxygen cylinder. The pressure of the gas source is 3.5kgf/cm2 and the flow rate is 5L/min-7L. /min. (4) Before the test, the subject rested for 15 minutes, and the forced expiratory volume (FEV1) value was measured twice for one second, and the highest value was taken as the basic control. (5) In the nebulizer, 5 ml of physiological saline was sprayed, and the tidal breath was taken, and the physiological saline was inhaled for 2 minutes to stop. FEV1 was measured and compared with the baseline value, reduced by less than 10%, continue the drug test, if it is reduced by more than 10%, rest for 5 minutes and then inhaled physiological saline, retest FEV1, if the result is the same as last time, indicating that the diluent itself can increase gas Road reactivity, no drug testing. (6) Drug test: If there is no reaction in the saline airway, the histamine will be inhaled sequentially from the lowest concentration, and the tidal breath will be absorbed. Each concentration will be absorbed for 2 minutes. After the end of the absorption, the FEV1 and other indicators will be measured until the FEV1 decreases by ≥20. %until. 2. Measurement method (intermittent inhalation method): (1) Preparation of reagents, preparation of instruments, preparation of subjects before the test, and tidal breathing. (2) The aerosol discharge was calibrated using a Devibiss: N.40 nebulizer with an average emissions of 0.003 ml per helium. Five nebulizers were used in one test, and physiological saline and four different concentrations of the drug solution were added. The histamine concentrations were: 3.125, 6.25, 25, 50 mg/ml. (3) The third item of the same method. (4) The nebulizer mouth tube is placed between the upper and lower teeth of the test subject, and a nose clip is worn. First, take saline, breathe three times, and slowly inhale 1s-2s to the total amount of lungs by calming the end of expiration (functional residual position). Breathing after 3s of breath, inhalation begins with the hand control of the nebulizer by the tester. Give a saline solution. After 60s, measure FEV1 twice (the difference must be 100m1) and record its high value. (5) Inhale the drugs in the order of the table (the method is the same as above). After each dose is taken, measure the FEV1 index and immediately take another dose until the FEV1 is reduced by 20% or the highest dose after inhaling the normal saline. The test is terminated. . Inhaled bronchodilator drugs. (6) Formula for calculating the percentage decrease of FEV1: (basic FEV1 - the highest FEV1 after drug absorption) / basic FEV1 × 100%. (7) Draw a dose response graph and determine the drug concentration required to reduce FEV1 by 20% in the graph. Description: The ordinate is FEV1 (% basic control value), and the abscissa is the inhaled drug concentration. a represents the normal person curve. b represents the curve of asthma patients. The result is judged: Histamine PC20FEV 18 mg / ml, PD20FEV 17.8 μmol was positive, greater than the above values ​​for the test negative. Not suitable for the crowd Inappropriate crowd: 1. Severe airway obstruction, asthma attack. 2. Hypertension, coronary heart disease, hyperthyroidism, pregnancy, cardiopulmonary dysfunction.