Methacholine Inhalation Research Articles

Validation of a single concentration inhalation provocation test (SCIPT) in children

Background:A new method to assess bronchial responsiveness (BR) using a single concentration methacholine has already been validated in adults with asthma1. Since the geometrical dimensions of the airways in children are different, and deposition of the inhaled aerosol also differs in children, results from studies in adults cannot simply be extrapolated to children.Aim of the study:validation of a single-concentration inhalation provocation method in children.Methods:Twenty-three subjects performed three methacholine inhalation challenge tests. The first two challenges according to method A: doubling doses, beginning with 0.03 mg to a maximum of 1.8 mg (maximal cumulated dose 3.6 mg), were administered with the Jeager Masterscope, Aerosol Provocation System (APS), medic aid sidestream nebulizer. The third challenge according method B: doubling doses, beginning with 0.002mg to a maximum of 1.8mg (maximal cumulated dose 3.5 mg), were administered with a Devillbiss 646 nebulizer. The degree of BR is expressed as a PD20. A difference of <1,5 dose step is assumed to be due to intra individual variation.Results:I.C.C. between method A and B is 0.80 and between both tests according method A 0.91. Comparing challenges 1 and 2, and 1 and 3 showed good agreement according to Bland and Altman.2Conclusion:This single concentration method is an accurate method of measuring BR in children.

Respiratory impedance response to a deep inhalation in children with history of cough or asthma.

The aim of this study was to describe the change in respiratory impedance induced by a deep inhalation (DI) in children who developed a positive response to inhalation of methacholine (Mch). Eighteen children aged 4.5-12.5 years, presenting with chronic cough or doctor-diagnosed asthma, were studied at baseline after inhalation of Mch and after inhalation of a bronchodilator. Respiratory resistance (Rrs) and reactance (Xrs) were measured by the forced oscillation technique, varying transrespiratory pressure at 12 Hz around the head. The tidal flow (V') and volume (V) dependence of Rrs before and after the DI was characterized according to the equation Rrs = K1 + K2 x /V'/ + K3 x V. DI induced no significant change at baseline or after inhalation of a bonchodilator. During Mch challenge, Rrs and K1 were significantly lower, and K3 and Xrs significantly less negative after DI than before, during both inspiration and expiration; there was no change in K2. We conclude that DI results in a decrease in Rrs in children with induced bronchoconstriction. The associated changes in Xrs, K1, and K3, and lack of decrease in K2, suggest that dilatation of airways occurs at the bronchial level, with little contribution of the upper airways or of a change in breathing patterns.

Mild intermittent asthma: CT assessment of bronchial cross-sectional area and lung attenuation at controlled lung volume.

To evaluate, with thin-section computed tomography (CT), changes in bronchial cross-sectional area and lung attenuation induced by bronchial stimulation in patients with mild intermittent asthma, at a given lung volume monitored with pneumotachography. Twelve patients with mild intermittent asthma who were nonsmokers (National Institutes of Health staging) and six nonsmoking healthy volunteers, age and sex ratio-matched, were examined by using helical thin-collimation CT at the level of basal bronchi at 65% of total lung capacity. Three sets of acquisitions were obtained: at baseline and after inhalation of methacholine and then salbutamol. Cross-sectional areas of bronchi greater than 4 mm(2) were segmented and calculated from CT images. Lung attenuation was measured in the anterior, lateral, and posterior areas of the right lung parenchyma. Gas trapping was evaluated by using thin-section CT at residual volume in six of the patients with asthma. Statistical analysis included two factors repeated-measurement analysis of variance and Mann-Whitney and Kruskal-Wallis nonparametric tests. Bronchial cross-sectional areas and lung attenuation did not vary significantly compared with baseline values following bronchial challenge in healthy volunteers or patients with asthma. However, in patients with asthma, bronchial cross-sectional areas were significantly smaller than in healthy volunteers, except after inhalation of salbutamol. Lung attenuation and anteroposterior attenuation gradient were significantly higher in patients with asthma than in healthy patients (P <.001). Air-trapping scores were significantly higher after methacholine challenge. Helical thin-collimation CT at controlled lung volume and at full expiration associated with bronchial challenge may help evaluate bronchoreactivity and inflammation in mild intermittent asthma.

Determinants of bronchial responsiveness to methacholine at school age in twin pairs.

The methacholine inhalation challenge test (MIC) was used to evaluate bronchial responsiveness in 67 children who were the products of multiple pregnancies when they were 7-15 years old. At birth, 30 (45%) infants had intrauterine growth retardation (IUGR; birth weight <2 SD below normal birth weight, or birth weight difference >1.3 SD between twin-pairs), and 59 (88%) were born before 37 weeks of gestation. None of the children had doctor-diagnosed asthma. The provocative dose of methacholine causing a 20% fall in Wright's peak expiratory flow (WPEF) (PD20) was below 1,000 microg in 10 (15%) children, and they were classified as MIC responders. There were no differences in perinatal or neonatal factors between MIC responders and nonresponders; in particular, MIC responses did not differ between IUGR infants, and children with appropriate growth for gestational age (AGA) at birth. There were seven discordant pairs in which one child was a MIC responder and the other was not; 5 responders were IUGR, and 2 were AGA children (ns). Respiratory tract infections after the neonatal period were equally common in IUGR and AGA children. However, these infections were associated with later bronchial hyperresponsiveness. Doctor-diagnosed respiratory infections, numbers of antibiotic courses, episodes of otitis media, and the need for adenoidectomy, tonsillectomy, and tympanostomy were more common in MIC responders than in nonresponders. We conclude that IUGR was not associated with subsequent bronchial hyperresponsiveness in twin pairs assessed by the MIC test. A significant relationship was seen between bronchial hyperresponsiveness and infections after the neonatal period.

In search of childhood asthma: questionnaire, tests of bronchial hyperresponsiveness, and clinical evaluation

Background: The definition or diagnosis of asthma is a challenge for both clinicians and epidemiologists. Symptom history is usually supplemented with tests of bronchial hyperresponsiveness (BHR) in spite of their...

Methacholine, cold air and exercise challenge tests in the diagnosis of bronchial responsiveness at school age: A follow-up study from birth to school age

ABSTRACT Background The aim of the present study was to compare three bronchial challenge tests for assessing bronchial hyperresponsiveness (BHR) in twin pairs followed up from birth to school age. Methods We studied three different bronchial challenge tests (methacholine inhalation challenge, cold air inhalation challenge and exercise-bronchodilation tests) at school age in 29 children born at or before 38 weeks gestation (median 35 weeks gestation) from multiple pregnancies. The children had been followed up from birth and were examined at the age of 7-15 years (median age 10 years). Results Bronchial hyperresponsiveness was found in 28-34% of children when these tests were analyzed separately. Eight children (28%) were exercise responders; two of them and three additional children were bronchodilator responders. Thus, 11 children (38%) had a pathologic result in the exercise-bronchodilation test. Ten children (34%) responded to cold air and nine children (31%) responded to methacholine inhalation. At least one test was pathologic in 18 children (62%), but only two children (7%) responded in all three challenges. A positive result in the exercise-bronchodilation test was associated with cold air reactivity, but not with methacholine reactivity. The exercise and cold air tests detected predominantly the same children. No differences were found in bronchial challenge test results between children who, at birth, were appropriately grown and those who had intrauterine growth retardation. conclusions Bronchial hyperresponsiveness was common (up to 62%) at school age in children born as moderately preterm. The outdoor exercise-bronchodilation test found 61% of all BHR cases. Bronchial hyperresponsiveness was not associated with intrauterine growth status. The most sensitive test was the cold air inhalation challenge and a good agreement was seen between this test and the exercise challenge outdoors.

Forced Expiratory Time and Bronchial Hyperresponsiveness to Methacholine

Pulmonary function tests (PFTs) are normally performed prior to methacholine inhalation challenges (MICs). In contrast to normal baseline spirometry (FEV1, FEF25%–27%, FVC), we have observed patients with positive MICs having shortened forced expiratory times (FET100%) in the baseline pre-MIC PFT. We prospectively evaluated the correlation of abnormalities in baseline pre-MIC FET100% in patients who have positive vs. negative MICs. Prospective analysis of baseline pre-MIC FET100% and MIC results in suspected asthmatics with normal lung exams, spirometry and chest x-rays. Using a PC20 FEV1 of ≤ 8 mg/ml methacholine, there were 115 positive and 69 negative MICs. The mean (±1 SD) FET100% in the positive MIC group was 3.57 ± 1.68 sec vs. 4.73 ± 1.60 sec in the negative group. The difference in these means was statistically significant (p < 0.0001). There was a statistically significant difference in the incidence of FET100% < 4 sec in the positive (55.65%) vs. the negative (30.43%) MIC group, p < 0.001. There was also a statistically significant difference in the incidence of positive MIC in FET100% < 4 sec (75.29%) vs. FET100% ≥ 4 sec (51.52%), p < 0.001. Our results suggest that in our highly selected, well-characterized population, FET100% < 6 sec is common and FET100% < 4 sec correlates with an increased likelihood of having a positive MIC.

Methacholine Challenge: Test-Shortening Procedures

Validation of test-shortening procedures for the 2-min tidal breathing methacholine challenge method. Retrospective chart review. Tertiary-care university clinical pulmonary function laboratory. One thousand subjects aged 10 to 85 years (mean +/- SD, 44.5 +/- 16.0 years), 44.5% male, referred for methacholine challenge. Two-minute tidal breathing methacholine challenge was performed, with both physician and technician access to published test-shortening procedures. There were 315 positive test results (provocative concentration of methacholine causing a 20% fall in FEV(1) [PC(20)] < or = 8 mg/mL) and 685 negative test results. The subjects with positive test results were less likely to be male (39.1 vs 47.5%; p < 0.02) and had lower FEV(1) (91.8 +/- 14.9% predicted vs 97.2 +/- 13.9% predicted; p < 0.001). The average starting PC(20) was between 0.5 mg/mL and 1.0 mg/mL; the most common PC(20) was 1 mg/mL (67%). There were 431 skipped concentrations in 380 subjects. The mean number of methacholine inhalations was 3.7 +/- 1.1 (3.9 +/- 0.1 for negative test results vs 3.3 +/- 1.2 for positive test results; p < 0.001). Eighteen subjects had a > or = 20% FEV(1) fall on the first inhalation, and 11 subjects had a > or = 20% FEV(1) fall after a skipped concentration. In only one case (0.1%) an FEV(1) fall > or = 40% on the first concentration was reported, compared with no cases after a skipped concentration and seven cases with a > or = 40% FEV(1) fall after a routine doubling dose step-up. The 2-min tidal breathing methacholine test in clinical practice can be safely shortened to an average of less than four inhalations using starting concentrations based on FEV(1), asthma medication, and clinical features, and by occasionally omitting concentrations.

Effect of apocynin on ozone-induced airway hyperresponsiveness to methacholine in asthmatics

Apocynin is an inhibitor of NADPH oxidase present in inflammatory cells such as eosinophils and neutrophils. We investigated the effect of inhaled apocynin on ozone-induced bronchial hyperresponsiveness in vivo. Seven mild atopic asthmatics participated in a placebo-controlled, cross-over study with two exposures to O 3 at 2-week intervals. Apocynin (3 ml of 0.5 mg/ml) was inhaled 2 times before and 6 times after O 3 exposure at hourly intervals. At 36 h before and 16 h after O 3 exposure, methacholine inhalation challenge tests (Mch) were performed, and PC 20 and maximal % fall from baseline (MFEV 1) were calculated from dose-response curves. O 3-induced change in PC 20 (ΔPC 20) after placebo treatment was −1.94 ± 0.39 DD (mean ± SEM doubling dose Mch) ( p = .001) and apocynin was −0.6 ± 0.33 DD ( p = .17). The difference between apocynin and placebo treatment was 1.3 DD ± 0.42 ( p = .02). O 3-induced ΔMFEV 1 was 11.9 ± 1.5% ( p = .008) during placebo inhalation and 3.85 ± 1.8% during apocynin ( p = .47). Apocynin reduced the ΔMFEV 1 by 8.05% compared to placebo ( p = .025). We conclude that apocynin markedly reduced O 3-induced hyperreactivity for Mch as well as maximal airway narrowing. The results suggest that apocynin may have a role in preventing ozone-induced exacerbations of asthma.

Effects of deep inspiration on bronchoconstriction in the rat

It is important to understand the mechanisms by which a deep inspiration (DI) affects bronchoconstriction in rodents so that their relevance as animal models of asthma can be assessed. We investigated the effect of DI on respiratory input impedance after methacholine inhalation in four groups of rats: a control group, a group receiving DI prior to challenge, and two groups receiving different degrees of DI after challenge. We measured respiratory input impedance for 15 min following a challenge. This provided time-courses approximating the resistance of the conducting airways and the impedance of the respiratory tissues. We found no significant difference in the peak changes in airway resistance comparing the control group and any of the DI groups following challenge. However, the peak increase in tissue impedance was reduced in the group receiving the largest DI after challenge. Our results thus suggest that the DIs that we administered were neither bronchodilatory nor bronchoprotective, but that they were able to reduce the amount of airway closure occurring following bronchoconstriction.

Strain dependence of airway hyperresponsiveness reflects differences in eosinophil localization in the lung.

Different strains of mice exhibit different degrees of airway hyperresponsiveness after sensitization to and airway challenge with ovalbumin. Antibody responses in BALB/c mice far exceeded those in C57BL/6 mice; in contrast, although responsiveness to methacholine was much higher in the BALB/c mice, the number of eosinophils in the bronchoalveolar lavage fluid was higher in C57BL/6 animals. Sensitized and challenged BALB/c mice developed increases in lung resistance and decreases in dynamic compliance after methacholine or 5-hydroxytryptamine inhalation. C57BL/6 mice only exhibited significant levels of responsiveness when dynamic compliance was monitored in response to inhaled 5-hydroxytryptamine. Eosinophils accumulated in the peribronchial and peripheral lung tissue in BALB/c mice but were distributed diffusely in the peripheral lung tissue of C57BL/6 mice. Thus, in addition to differences in antibody responses and cholinergic agonist reactivity, differences in the responses of large and small airways may reflect the selective distribution of eosinophils in lung tissue.

Regulation of murine airway responsiveness by endothelial nitric oxide synthase.

Nitric oxide (NO) is a potent vasodilator, but it can also modulate contractile responses of the airway smooth muscle. Whether or not endothelial (e) NO synthase (NOS) contributes to the regulation of bronchial tone is unknown at present. Experiments were designed to investigate the isoforms of NOS that are expressed in murine airways and to determine whether or not the endogenous release of NO modulates bronchial tone in wild-type mice and in mice with targeted deletion of eNOS [eNOS(-/-)]. The presence of neuronal NOS (nNOS), inducible NOS (iNOS), and eNOS in murine trachea and lung parenchyma was assessed by RT-PCR, immunoblotting, and immunohistochemistry. Airway resistance was measured in conscious unrestrained mice by means of a whole body plethysmography chamber. The three isoforms of NOS were constitutively present in lungs of wild-type mice, whereas only iNOS and nNOS were present in eNOS(-/-) mice. Labeling of nNOS was localized in submucosal airway nerves but was not consistently detected, and iNOS immunoreactivity was observed in tracheal and bronchiolar epithelial cells, whereas eNOS was expressed in endothelial cells. In wild-type mice, treatment with N-nitro-L-arginine methyl ester, but not with aminoguanidine, potentiated the increase in airway resistance produced by inhalation of methacholine. eNOS(-/-) mice were hyperresponsive to inhaled methacholine and markedly less sensitive to N-nitro-L-arginine methyl ester. These results demonstrate that the three NOS isoforms are expressed constitutively in murine lung and that NO derived from eNOS plays a physiological role in controlling bronchial airway reactivity.

Age-dependent relationship between bronchial hyperresponsiveness to methacholine and total serum IgE level in asthmatic children

A relationship between nonspecific bronchial hyperresponsiveness and allergic airway inflammation has been reported in children and in adults with asthma, but the relationship in infants with asthma is still unclear. To evaluate the relationship between bronchial hyperresponsiveness and total serum IgE level throughout childhood. Bronchial reactivity to methacholine from the age of 1 to 16 years was studied by methacholine inhalation challenge using transcutaneous oxygen pressure (tcPO2) monitoring. Two hundred one asthmatic children (boys:girls = 132:69; 7.3+/-4.0 years of age, mean +/- SD) were enrolled in this study. The tcPO2 was measured using a tcPO2 monitor. Serial doses of methacholine were doubled until a 10% decrease in tcPO2 from the baseline was reached. The cumulative dose of methacholine at the inflection point of tcPO2 was considered to represent the bronchial reactivity to methacholine. There was no relationship between the cumulative dose of methacholine at the inflection point of tcPO2 and total serum IgE level in the group of children aged 1 to 4 years (P = 0.212), but significant correlations were found in the groups aged 5 to 10 years and 11 to 16 years (P = 0.044 and P = 0.014, respectively). We conclude that there is an age-dependent relationship between bronchial reactivity to methacholine and the total serum IgE level and that inhaled allergens, which were more common allergens in older children, may have some effects on the degree of bronchial reactivity to methacholine in children with asthma.

Relationship between bronchial hyperresponsiveness and development of asthma in children with chronic cough.

To evaluate the relationship between bronchial hyperresponsiveness (BHR) and the development of asthma in children with chronic cough, we performed methacholine inhalation challenges and transcutaneous oxygen pressure (tcPO2) measurements in 92 children with chronic cough aged from 1-13 years (55 boys and 37 girls; mean, 5.3 years) and followed them for > or = 10 years. Forty-four age-matched children with asthma (24 males and 20 females; mean, 6.5 years) and 44 age-matched children without cough or asthma served as controls (18 males and 26 females; mean, 4.6 years). Consecutive doubling doses of methacholine were inhaled until a 10% decrease in tcPO2 from baseline was observed. The cumulative dose of methacholine at the inflection point of the tcPO2 record (Dmin-PO2) was considered to represent hyperresponsiveness to inhaled methacholine. After 10 years or more of follow-up, 60 of the 92 subjects with cough answered our questionnaire, and 27/60 had been diagnosed with asthma. There was a statistical difference in Dmin-PO2 between the children who presented with chronic cough originally and who developed asthma (asthma-developed group) and those who did not develop asthma (asthma-free group). There was no difference in the value of Dmin-PO2 between the asthma-developed group and the asthma group, or between the asthma-free group and the age-matched control group. Among the children with chronic cough, there was no difference in Dmin-PO2 between girls and boys, either in the asthma-developed group or in the asthma-group. We conclude that 45% of the children with a chronic cough in early life developed asthma, and that BHR in children with chronic cough during the childhood period is a strong risk factor for the development of asthma.

Diesel exhaust enhances airway responsiveness in asthmatic subjects.

Particulate matter (PM) pollution has been associated with negative health effects, including exacerbations of asthma following exposure to PM peaks. The aim of the present study was to investigate the effects of short-term exposure to diesel exhaust (DE) in asthmatics, by specifically addressing the effects on airway hyperresponsiveness, lung function and airway inflammation. Fourteen nonsmoking, atopic asthmatics with stable disease, on continuous treatment with inhaled corticosteroids, were included. All were hyperresponsive to methacholine. Each subject was exposed to DE (particles with a 50% cut-off aerodynamic diameter of 10 microm (PM10) 300 microg x m(-3)) and air during 1 h on two separate occasions. Lung function was measured before and immediately after the exposures. Sputum induction was performed 6 h, and methacholine inhalation test 24 h, after each exposure. Exposure to DE was associated with a significant increase in the degree of hyperresponsiveness, as compared to after air, of 0.97 doubling concentrations at 24 h after exposure (p < 0.001). DE also induced a significant increase in airway resistance (p=0.004) and in sputum levels of interleukin (IL)-6 (p=0.048). No changes were detected in sputum levels of methyl-histamine, eosinophil cationic protein, myeloperoxidase and IL-8. This study indicated that short-term exposure to diesel exhaust, equal to high ambient levels of particulate matter, is associated with adverse effects in asthmatic airways, even in the presence of inhaled corticosteroid therapy. The increase in airway responsiveness may provide an important link to epidemiological findings of exacerbations of asthma following exposure to particulate matter.

Comparisons of Peak Diurnal Expiratory Flow Variation, Postbronchodilator FEV1 Responses, and Methacholine Inhalation Challenges in the Evaluation of Suspected Asthma

The validity of peak expiratory flow variation (PEFvar) as defined by National Heart, Lung, and Blood Institute (NHLBI) guidelines as a diagnostic tool for suspected asthma or its comparative value to methacholine inhalation challenge (MIC) or postbronchodilator (BD) FEV(1) responses has not been formally assessed. We prospectively analyzed the correlation of 28 different PEFvar indexes (including 4 NHLBI-compatible indexes) with MIC and pre-BD and post-BD FEV(1) responses in suspected asthmatic subjects with normal findings on lung examination, chest radiography, and baseline spirometry. Participants were asked to record peak expiratory flow four times daily for 2 to 3 weeks, followed by an MIC. During a minimum 6-month follow-up period, a clinical diagnosis of asthma was made or ruled out based on testing results and response to antiasthma therapy. Medical school-affiliated subspecialty private practice of allergy, asthma, and immunology. One hundred twenty-one suspected asthmatic patients with normal findings on lung examination, chest radiography, and baseline spirometry. Fifty-seven subjects completed both the peak flow diary and the MIC and were accepted for statistical analysis. There were no statistically significant correlations between any peak expiratory flow index and MIC. Among the three diagnostic tools evaluated, MIC had the highest sensitivity (85.71%). All the PEFvar indexes and post-BD responses had low sensitivity and high false-negative rates. PEFvar and post-BD FEV(1) responses are poor substitutes for MIC in the assessment of patients with suspected asthma with normal findings on lung examination, chest radiography, and spirometry. Our findings warrant a reconsideration of the NHLBI guidelines recommendation of the utility of PEFvar as a diagnostic tool for asthma in clinical practice.

Noninvasive Method to Measure Airway Obstruction in Nonanesthetized Allergen-Sensitized and Challenged Mice

Background: Conventional methods used to measure bronchoconstriction are invasive, technically demanding and time consuming. Objectives: Our purpose was to evaluate a noninvasive method, by barometric whole-body plethysmography (WBP), to evaluate bronchoconstriction and bronchial hyperreactivity in mice induced by ovalbumin (OA) inhalation challenge in comparison with an invasive method. Enhanced pause (P_enh) was used as an index of airway obstruction. Methods: Eight mice were sensitized by OA (group I) and then challenged with OA. Twenty-four hours later, pulmonary function testing (PFT) was measured by WBP at baseline and after a methacholine (MCh) inhalation challenge. Eight weight-matched normal mice served as controls (group II). Four hours after PFT in a nonanesthetized condition, all animals were anesthetized and paralyzed. Baseline PFT was performed by the maximal forced expiratory maneuver (MFEM), and then the animals were given varying doses of acetylcholine (ACh; 25, 50, 75, 100 µg/kg) injected through the jugular vein. Five seconds after ACh injections, pulmonary functions were examined, including MFEM, peak airway pressure and total lung compliance. After completing PFT, bronchoalveolar lavage (BAL) was performed, the animals were sacrificed, and the lungs were examined histologically. Results: Group I had increased P_enh in response to MCh in the nonanesthetized condition and decreased flow in the anesthetized condition, characterized by greater decreases in MFEM flow rates MFEF 50% and MFEF 25% than the control group. The peak flows, MFEF 75%, MFEF 50% and MFEF 25%, for group I were lower than those for group II at doses of ACh higher than 25 µg/kg. There were concentration-dependent increases in P_enh in response to aerosolized MCh in both groups, but the P_enh in response to aerosolized MCh was significantly enhanced in group I when compared with controls. The doses of MCh required for 100% increases in P_enh were significantly reduced for sensitized and challenged mice. There was a positive correlation between provocative doses PD200 P_enh MCh, PD20 MFEF 50% ACh and PD20 MFEF 25% ACh. There was a negative correlation between the PD200 P_enh MCh and the percentage of eosinophils in BAL fluid. There was an increased total cell count and an increased percentage and absolute number of eosinophils and lymphocytes in the BAL fluid of sensitized animals. OA-sensitized mice also had a severe inflammatory reaction of airway and lung tissue, characterized by congestion, edema and inflammatory cell infiltration and desquamation of bronchial epithelial cells. Conclusion: The noninvasive method of WBP can be used to evaluate airway obstruction and hyperreactivity induced in mice by allergen challenge.

Assessment of oxidant stress in allergic asthma by measurement of the major urinary metabolite of F2-isoprostane, 15-F2t-IsoP (8-iso-PGF2alpha).

Asthma is a chronic inflammatory disease of the airways which may involve an oxidant injury to the lung. Assessment of oxidant stress is difficult in vivo, but measurement of F2-isoprostanes (F2-IsoPs), free radical-catalysed products of arachidonic acid, appears to offer a reliable approach for quantitative measurement of oxidative stress status in vivo. We have recently developed a mass spectrometric assay for 2,3-dinor-5,6-dihydro-15-F2t-IsoP (15-F2t-IsoP-M), the major urinary metabolite of the F2-IsoP, 15-F2t-IsoP (8-iso-PGF2a). Measurement of the urinary excretion of this metabolite offers a reliable index of oxidative stress status in vivo that has advantages over measuring unmetabolized F2-IsoPs in urine and plasma. To assess the occurrence of oxidative stress in patients with atopic asthma following allergen exposure in vivo by measuring the urinary excretion of 15-F2t-IsoP-M. Analysis of 15-F2t-IsoP-M by GC-NICI-MS in nine mild atopic asthmatics following inhaled allergen provocation and four asthmatic subjects after inhaled challenge with methacholine. Urinary excretion of 15-F2t-IsoP-M increased at 2 h after allergen challenge and remained significantly elevated in all urine collections during the subsequent 8-h period of the study compared to the baseline value (ANOVA, and Student-Newman-Keuls multiple comparisons test). No increase in the urinary excretion of 15-F2t-IsoP-M occurred after inhalation of methacholine. Allergen challenge causes an oxidant injury in human atopic asthmatics. 15-F2t-IsoP-M is a valuable marker of oxidant stress in vivo.

Acute changes in bronchoconstriction influences exhaled nitric oxide level.

In previous studies the exhaled nitric oxide (NO) level of asthma patients was investigated only in association with bronchial inflammation, and whether the degree of bronchoconstriction itself influences the exhaled NO level has never been investigated. We therefore evaluated the effect of inhalation of a bronchoconstrictor (methacholine) or a bronchodilator (salbutamol) on the exhaled NO level of healthy volunteers and asthma patients. The exhaled NO level of the healthy volunteers decreased after methacholine inhalation. The exhaled NO level of patients with mild or moderate persistent asthma, who had no asthma attacks on the day of measurement, increased after salbutamol inhalation, and the exhaled NO level of asthma patients during asthma attacks increased after salbutamol inhalation followed by intravenous drip infusion of aminophylline. It is suspected that large amounts of NO are trapped in the lung distal to the constricted airway, contributing little to the exhaled NO level at the mouth. However, we expect that the trapped NO is exhaled at a larger fraction after the dilatation of the constricted small airway, thereby increasing the exhaled NO level at the mouth. In conclusion, the results of this study suggest that acute changes in bronchoconstriction themselves influence the exhaled NO level independently of the change in NO synthase activity associated with airway inflammation.

The Relation Between Bronchodilator Response, Airway Hyperresponsiveness and Serum Eosinophil Cationic Protein (ECP) Level in Moderate to Severe Asthmatics

Background Bronchial asthma is characterized by a reversible airway obstruction, airway hyperresponsiveness, and eosinophilic airway inflammation. The bronchodilator response(BDR) after short acting beta agonist inhalation and PC20 with methacholine inhalation are frequently used for diagnosing bronchial asthma, However, the relationship between the presence of a bronchodilator response and the degree of airway hyperresponsiveness is uncertain. Therefore, the availability of a eosinophil cationic protein(ECP) and a correlation ECP with a bronchodilator response and airway hyperresposiveness was investigated. Method A total 71 patients with a moderate to severe degree of bronchial asthma were enrolled and divided into two groups. 31 patients with a positive bronchodilator response and 38 patients with a negative bronchodilator response were evaluated. In both groups, the serum ECP, peripheral blood eosinophil counts, and total IgE level were measured and the methacholine bronchial provocation test was examined. Results There were no differences observed in age, sex, atopy, and baseline spirometry in both groups. The peripheral eosinophil counts showed no difference in both groups, but the ECP level in group 1 (bronchodilator responder group) was higher than in group 2(non-bronchodilator responder group) (22.4±20.7 vs 14.2±10.4, mean±SD). The PC20 in group 1 was significantly lower than in group 2 (1.14±1.68 vs 66±2.98). There was a significant positive correlation between the BDR and ECP, and a negative correlation between the bronchial hyperresponsiveness and ECP. Conclusion The bronchodilator response significantly correlated with the bronchial hyperresponsiveness and serum ECP in the moderate to severe asthma patients. Hence, the positive bronchodilator response is probably related with active bronchial inflammation and may be used as a valuable index in treatment, course and prognosis of bronchial asthma.