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Louis-philippe Boulet - One of the best experts on this subject based on the ideXlab platform.
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airway response to methacholine following eucapnic voluntary hyperpnea in athletes
PLOS ONE, 2015Co-Authors: Valérie Bougault, Julie Turmel, Evelyne Blouin, Louis-philippe BouletAbstract:Aim To evaluate the changes in airway responsiveness to methacholine Inhalation Test (MIT) when performed after an eucapnic voluntary hyperpnea challenge (EVH) in athletes. Methods Two MIT preceded (visit 1) or not (visit 2) by an EVH, were performed in 28 athletes and 24 non-athletes. Twelve athletes and 13 non-athletes had airway hyperresponsiveness (AHR) to methacholine, and 11 athletes and 11 non-athletes had AHR to EVH (EVH+). Results The MIT PC20 post-EVH was significantly lower compared to baseline MIT PC20 by 1.3±0.7 doubling-concentrations in EVH+ athletes only (p<0.0001). No significant change was observed in EVH- athletes and EVH+/EVH- non-athletes. A significant correlation between the change in MIT PC20 post-EVH and EVH+/EVH- status and athlete/nonathlete status was found (Adjusted R2=0.26 and p<0.001). Three (11%) athletes and one (4%) non-athlete had a change in the diagnosis of AHR when MIT was performed consecutively to EVH. Conclusion The responsiveness to methacholine was increased by a previous indirect challenge in EVH+ athletes only. The mechanisms for such increase remain to be determined. MIT and EVH should ideally be performed on separate occasions as there is a small but possible risk to obtain a false-positive response to methacholine when performed immediately after the EVH. Trial Registration ClinicalTrials.gov NCT00686491
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Airway Response to Methacholine following Eucapnic Voluntary Hyperpnea in Athletes
2015Co-Authors: Valérie Bougault, Julie Turmel, Evelyne Blouin, Louis-philippe BouletAbstract:AimTo evaluate the changes in airway responsiveness to methacholine Inhalation Test (MIT) when performed after an eucapnic voluntary hyperpnea challenge (EVH) in athletes.MethodsTwo MIT preceded (visit 1) or not (visit 2) by an EVH, were performed in 28 athletes and 24 non-athletes. Twelve athletes and 13 non-athletes had airway hyperresponsiveness (AHR) to methacholine, and 11 athletes and 11 non-athletes had AHR to EVH (EVH+).ResultsThe MIT PC20 post-EVH was significantly lower compared to baseline MIT PC20 by 1.3±0.7 doubling-concentrations in EVH+ athletes only (p
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perception of bronchoconstriction following methacholine and eucapnic voluntary hyperpnea challenges in elite athletes
Chest, 2014Co-Authors: Simon Couillard, Julie Turmel, Valérie Bougault, Louis-philippe BouletAbstract:Objective Self-reported respiratory symptoms are poor predictors of exercise-induced bronchoconstriction (EIB) in athletes. The objective of this study was to determine whether athletes have an inadequate perception of bronchoconstriction. Methods One hundred thirty athletes and 32 nonathletes completed a standardized questionnaire and underwent eucapnic voluntary hyperpnea (EVH) and methacholine Inhalation Test. Perception scores were quoted on a modified Borg scale before each spirometry measurement for cough, breathlessness, chest tightness, and wheezing. Perception slope values were also obtained by plotting the variation of perception scores before and after the challenges against the fall in FEV 1 expressed as a percentage of the initial value [(perception scores after − before)/FEV 1 ]. Results Up to 76% of athletes and 68% of nonathletes had a perception score of ≤ 0.5 at 20% fall in FEV 1 following methacholine. Athletes with EIB/airway hyperresponsiveness (AHR) had lower perception slopes to methacholine than nonathletes with asthma for breathlessness only ( P = .02). Among athletes, those with EIB/AHR had a greater perception slope to EVH for breathlessness and wheezing ( P = .02). Female athletes had a higher perception slope for breathlessness after EVH and cough after methacholine compared with men ( P P Conclusions Minimal differences in perception of bronchoconstriction-related symptoms between athletes and nonathletes were observed. Among athletes, the presence of EIB/AHR, older age, and female sex were associated with slightly higher perception scores.
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seasonal variations of cough reflex sensitivity in elite athletes training in cold air environment
Cough, 2012Co-Authors: Julie Turmel, Valérie Bougault, Louis-philippe BouletAbstract:Exercise-induced cough is common among athletes. Athletes training in cold air often report an increasingly troublesome cough during the winter season. Chronic airway irritation or inflammation may increase the sensory response of cough receptors. The aim of this study was to evaluate the seasonal variability of cough reflex sensitivity to capsaicin in elite athletes. Fifty-three elite winter athletes and 33 sedentary subjects completed a respiratory questionnaire and a capsaicin provocation Test during the summer, fall, and winter. Allergy skin prick Tests, spirometry, eucapnic voluntary hyperpnea Test (EVH), methacholine Inhalation Test (MIT), and induced sputum analysis were also performed. In athletes, the prevalence of cough immediately after exercise was high, particularly during winter. Athletes often showed a late occurrence of cough between 2-8 h after exercise. The cough reflex sensitivity to capsaicin was unchanged through the seasons in both athletes and non-athlete subjects. No significant correlations were found in groups between cough reflex sensitivity to capsaicin and the number of years in sport training, the number of hours of training per week, EVH response (% fall in FEV1), airway responsiveness to methacholine (PC20), airway inflammation or atopy. The prevalence of cough immediately and a few hours after exercise is high in athletes and more frequently reported during winter. However, cough does not seem to be associated with cough reflex hypersensitivity to capsaicin, bronchoconstriction, or airway inflammation in the majority of athletes.
Lutz Beckert - One of the best experts on this subject based on the ideXlab platform.
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air travel hypoxemia vs the hypoxia Inhalation Test in passengers with copd
Chest, 2008Co-Authors: Paul T Kelly, Maureen P. Swanney, Chris Frampton, Leigh M. Seccombe, Matthew J. Peters, Lutz BeckertAbstract:Background Limited data are available comparing air travel with the hypoxia Inhalation Test (HIT) in passengers with COPD. The aim of this study was to assess the predictive capability of the HIT to in-flight hypoxemia in passengers with COPD. Methods Thirteen passengers (seven female passengers) with COPD (mean [± SD], FEV 1 /FVC ratio, 44 ± 17%) volunteered for this study. Respiratory function Tests were performed preflight. Pulse oximetry, cabin pressure, and dyspnea were recorded in flight. The HIT and a 6-min walk Test were performed postflight. The in-flight oxygenation response was compared to the HIT results and respiratory function parameters. Results All subjects flew without the use of oxygen, and no adverse events were recorded in-flight (mean cabin altitude, 2,165 m; altitude range, 1,892 to 2,365 m). Air travel caused significant desaturation (mean preflight oxygen saturation, 95 ± 1%; mean in-flight oxygen saturation, 86 ± 4%), which was worsened by activity (nadir pulse oximetric saturation [Sp o 2 ], 78 ± 6%). The HIT caused mean desaturation that was comparable to that of air travel (84 ± 4%). The mean in-flight partial pressure of inspired oxygen (P io 2 ) was higher than the HIT P io 2 (113 ± 3 mm Hg vs 107 ± 1 mm Hg, respectively; p o 2 showed the strongest correlation with in-flight Sp o 2 ( r = 0.84; p Conclusion Significant in-flight desaturation can be expected in passengers with COPD. The HIT results compared favorably with the air travel data, with differences explainable by P io 2 and physical activity. The HIT is the best widely available laboratory Test to predict in-flight hypoxemia.
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air travel hypoxemia vs the hypoxia Inhalation Test in passengers with copd commentary
Chest, 2008Co-Authors: Lawrence C Mohr, Maureen P. Swanney, Chris Frampton, Leigh M. Seccombe, Matthew J. Peters, Paul T Kelly, Lutz BeckertAbstract:Background: Limited data are available comparing air travel with the hypoxia Inhalation Test (HIT) in passengers with COPD. The aim of this study was to assess the predictive capability of the HIT to in-flight hypoxemia in passengers with COPD. Methods: Thirteen passengers (seven female passengers) with COPD (mean [± SD], FEV 1 /FVC ratio, 44 ± 17%) volunteered for this study. Respiratory function Tests were performed preflight. Pulse oximetry, cabin pressure, and dyspnea were recorded in flight. The HIT and a 6-min walk Test were performed postflight. The in-flight oxygenation response was compared to the HIT results and respiratory function parameters. Results: All subjects flew without the use of oxygen, and no adverse events were recorded in-flight (mean cabin altitude, 2,165 m; altitude range, 1,892 to 2,365 m). Air travel caused significant desaturation (mean preflight oxygen saturation, 95 ± 1%; mean in-flight oxygen saturation, 86 ± 4%), which was worsened by activity (nadir pulse oximetric saturation [SpO 2 ], 78 ± 6%). The HIT caused mean desaturation that was comparable to that of air travel (84 ± 4%). The mean in-flight partial pressure of inspired oxygen (PIO 2 ) was higher than the HIT PIO 2 (113 ± 3 mm Hg vs 107 ± 1 mm Hg, respectively; p < 0.001). The HIT SpO 2 showed the strongest correlation with in-flight SpO 2 (r = 0.84; p < 0.001). Conclusion: Significant in-flight desaturation can be expected in passengers with COPD. The HIT results compared favorably with the air travel data, with differences explainable by PIO 2 and physical activity. The HIT is the best widely available laboratory Test to predict in-flight hypoxemia.
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Normobaric hypoxia Inhalation Test vs. response to airline flight in healthy passengers.
Aviation space and environmental medicine, 2006Co-Authors: P. Kelly, Maureen P. Swanney, Chris Frampton, Leigh M. Seccombe, Matthew J. Peters, Lutz BeckertAbstract:Introduction: There is little data available to determine the normal response to normobaric hypoxia Inhalation Testing (NHIT) and air travel. Quantifying a healthy response may assist in the evaluation of passengers considered at risk for air travel. The aims of this study were: 1) to quantify the degree of desaturation in healthy subjects during a NHIT and air travel; and 2) assess the validity of the NHIT when compared with actual in-flight responses. Methods: There were 15 healthy adults (age 23-57; 10 women) who volunteered for this study. Preflight Tests included lung function, arterial blood gas, pulse oximetry (Spo 2 ), and NHIT (inspired oxygen 15%). Spo 2 and cabin pressure were measured continuously on each subject during a commercial air flight (mean cabin altitude 2178 m; range 1719-2426 m). In-flight oxygenation was compared with the preflight NHIT. Results: Lung function Testing results were normal. There was significant desaturation (Spo 2 ) during the NHIT (pre: 98 ± 2%; post: 92 ± 2%) and at cruising altitude (pre: 97 ± 1%; cruise: 92 ± 2%). There was no difference between the final NHIT Spo 2 and the mean in-flight Spo 2 . There was a significant difference between the lowest in-flight Spo 2 (88 ± 2%) vs. the lowest NHIT Spo 2 (90 ± 2%). Discussion: Oxygen saturation decreases significantly during air travel in normal individuals. In this group of healthy passengers the NHIT approximates some, but not all, aspects of in-flight oxygenation. These results can be used to describe a normal response to the NHIT and air-travel.
Valérie Bougault - One of the best experts on this subject based on the ideXlab platform.
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airway response to methacholine following eucapnic voluntary hyperpnea in athletes
PLOS ONE, 2015Co-Authors: Valérie Bougault, Julie Turmel, Evelyne Blouin, Louis-philippe BouletAbstract:Aim To evaluate the changes in airway responsiveness to methacholine Inhalation Test (MIT) when performed after an eucapnic voluntary hyperpnea challenge (EVH) in athletes. Methods Two MIT preceded (visit 1) or not (visit 2) by an EVH, were performed in 28 athletes and 24 non-athletes. Twelve athletes and 13 non-athletes had airway hyperresponsiveness (AHR) to methacholine, and 11 athletes and 11 non-athletes had AHR to EVH (EVH+). Results The MIT PC20 post-EVH was significantly lower compared to baseline MIT PC20 by 1.3±0.7 doubling-concentrations in EVH+ athletes only (p<0.0001). No significant change was observed in EVH- athletes and EVH+/EVH- non-athletes. A significant correlation between the change in MIT PC20 post-EVH and EVH+/EVH- status and athlete/nonathlete status was found (Adjusted R2=0.26 and p<0.001). Three (11%) athletes and one (4%) non-athlete had a change in the diagnosis of AHR when MIT was performed consecutively to EVH. Conclusion The responsiveness to methacholine was increased by a previous indirect challenge in EVH+ athletes only. The mechanisms for such increase remain to be determined. MIT and EVH should ideally be performed on separate occasions as there is a small but possible risk to obtain a false-positive response to methacholine when performed immediately after the EVH. Trial Registration ClinicalTrials.gov NCT00686491
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Airway Response to Methacholine following Eucapnic Voluntary Hyperpnea in Athletes
2015Co-Authors: Valérie Bougault, Julie Turmel, Evelyne Blouin, Louis-philippe BouletAbstract:AimTo evaluate the changes in airway responsiveness to methacholine Inhalation Test (MIT) when performed after an eucapnic voluntary hyperpnea challenge (EVH) in athletes.MethodsTwo MIT preceded (visit 1) or not (visit 2) by an EVH, were performed in 28 athletes and 24 non-athletes. Twelve athletes and 13 non-athletes had airway hyperresponsiveness (AHR) to methacholine, and 11 athletes and 11 non-athletes had AHR to EVH (EVH+).ResultsThe MIT PC20 post-EVH was significantly lower compared to baseline MIT PC20 by 1.3±0.7 doubling-concentrations in EVH+ athletes only (p
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perception of bronchoconstriction following methacholine and eucapnic voluntary hyperpnea challenges in elite athletes
Chest, 2014Co-Authors: Simon Couillard, Julie Turmel, Valérie Bougault, Louis-philippe BouletAbstract:Objective Self-reported respiratory symptoms are poor predictors of exercise-induced bronchoconstriction (EIB) in athletes. The objective of this study was to determine whether athletes have an inadequate perception of bronchoconstriction. Methods One hundred thirty athletes and 32 nonathletes completed a standardized questionnaire and underwent eucapnic voluntary hyperpnea (EVH) and methacholine Inhalation Test. Perception scores were quoted on a modified Borg scale before each spirometry measurement for cough, breathlessness, chest tightness, and wheezing. Perception slope values were also obtained by plotting the variation of perception scores before and after the challenges against the fall in FEV 1 expressed as a percentage of the initial value [(perception scores after − before)/FEV 1 ]. Results Up to 76% of athletes and 68% of nonathletes had a perception score of ≤ 0.5 at 20% fall in FEV 1 following methacholine. Athletes with EIB/airway hyperresponsiveness (AHR) had lower perception slopes to methacholine than nonathletes with asthma for breathlessness only ( P = .02). Among athletes, those with EIB/AHR had a greater perception slope to EVH for breathlessness and wheezing ( P = .02). Female athletes had a higher perception slope for breathlessness after EVH and cough after methacholine compared with men ( P P Conclusions Minimal differences in perception of bronchoconstriction-related symptoms between athletes and nonathletes were observed. Among athletes, the presence of EIB/AHR, older age, and female sex were associated with slightly higher perception scores.
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seasonal variations of cough reflex sensitivity in elite athletes training in cold air environment
Cough, 2012Co-Authors: Julie Turmel, Valérie Bougault, Louis-philippe BouletAbstract:Exercise-induced cough is common among athletes. Athletes training in cold air often report an increasingly troublesome cough during the winter season. Chronic airway irritation or inflammation may increase the sensory response of cough receptors. The aim of this study was to evaluate the seasonal variability of cough reflex sensitivity to capsaicin in elite athletes. Fifty-three elite winter athletes and 33 sedentary subjects completed a respiratory questionnaire and a capsaicin provocation Test during the summer, fall, and winter. Allergy skin prick Tests, spirometry, eucapnic voluntary hyperpnea Test (EVH), methacholine Inhalation Test (MIT), and induced sputum analysis were also performed. In athletes, the prevalence of cough immediately after exercise was high, particularly during winter. Athletes often showed a late occurrence of cough between 2-8 h after exercise. The cough reflex sensitivity to capsaicin was unchanged through the seasons in both athletes and non-athlete subjects. No significant correlations were found in groups between cough reflex sensitivity to capsaicin and the number of years in sport training, the number of hours of training per week, EVH response (% fall in FEV1), airway responsiveness to methacholine (PC20), airway inflammation or atopy. The prevalence of cough immediately and a few hours after exercise is high in athletes and more frequently reported during winter. However, cough does not seem to be associated with cough reflex hypersensitivity to capsaicin, bronchoconstriction, or airway inflammation in the majority of athletes.
Julie Turmel - One of the best experts on this subject based on the ideXlab platform.
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airway response to methacholine following eucapnic voluntary hyperpnea in athletes
PLOS ONE, 2015Co-Authors: Valérie Bougault, Julie Turmel, Evelyne Blouin, Louis-philippe BouletAbstract:Aim To evaluate the changes in airway responsiveness to methacholine Inhalation Test (MIT) when performed after an eucapnic voluntary hyperpnea challenge (EVH) in athletes. Methods Two MIT preceded (visit 1) or not (visit 2) by an EVH, were performed in 28 athletes and 24 non-athletes. Twelve athletes and 13 non-athletes had airway hyperresponsiveness (AHR) to methacholine, and 11 athletes and 11 non-athletes had AHR to EVH (EVH+). Results The MIT PC20 post-EVH was significantly lower compared to baseline MIT PC20 by 1.3±0.7 doubling-concentrations in EVH+ athletes only (p<0.0001). No significant change was observed in EVH- athletes and EVH+/EVH- non-athletes. A significant correlation between the change in MIT PC20 post-EVH and EVH+/EVH- status and athlete/nonathlete status was found (Adjusted R2=0.26 and p<0.001). Three (11%) athletes and one (4%) non-athlete had a change in the diagnosis of AHR when MIT was performed consecutively to EVH. Conclusion The responsiveness to methacholine was increased by a previous indirect challenge in EVH+ athletes only. The mechanisms for such increase remain to be determined. MIT and EVH should ideally be performed on separate occasions as there is a small but possible risk to obtain a false-positive response to methacholine when performed immediately after the EVH. Trial Registration ClinicalTrials.gov NCT00686491
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Airway Response to Methacholine following Eucapnic Voluntary Hyperpnea in Athletes
2015Co-Authors: Valérie Bougault, Julie Turmel, Evelyne Blouin, Louis-philippe BouletAbstract:AimTo evaluate the changes in airway responsiveness to methacholine Inhalation Test (MIT) when performed after an eucapnic voluntary hyperpnea challenge (EVH) in athletes.MethodsTwo MIT preceded (visit 1) or not (visit 2) by an EVH, were performed in 28 athletes and 24 non-athletes. Twelve athletes and 13 non-athletes had airway hyperresponsiveness (AHR) to methacholine, and 11 athletes and 11 non-athletes had AHR to EVH (EVH+).ResultsThe MIT PC20 post-EVH was significantly lower compared to baseline MIT PC20 by 1.3±0.7 doubling-concentrations in EVH+ athletes only (p
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perception of bronchoconstriction following methacholine and eucapnic voluntary hyperpnea challenges in elite athletes
Chest, 2014Co-Authors: Simon Couillard, Julie Turmel, Valérie Bougault, Louis-philippe BouletAbstract:Objective Self-reported respiratory symptoms are poor predictors of exercise-induced bronchoconstriction (EIB) in athletes. The objective of this study was to determine whether athletes have an inadequate perception of bronchoconstriction. Methods One hundred thirty athletes and 32 nonathletes completed a standardized questionnaire and underwent eucapnic voluntary hyperpnea (EVH) and methacholine Inhalation Test. Perception scores were quoted on a modified Borg scale before each spirometry measurement for cough, breathlessness, chest tightness, and wheezing. Perception slope values were also obtained by plotting the variation of perception scores before and after the challenges against the fall in FEV 1 expressed as a percentage of the initial value [(perception scores after − before)/FEV 1 ]. Results Up to 76% of athletes and 68% of nonathletes had a perception score of ≤ 0.5 at 20% fall in FEV 1 following methacholine. Athletes with EIB/airway hyperresponsiveness (AHR) had lower perception slopes to methacholine than nonathletes with asthma for breathlessness only ( P = .02). Among athletes, those with EIB/AHR had a greater perception slope to EVH for breathlessness and wheezing ( P = .02). Female athletes had a higher perception slope for breathlessness after EVH and cough after methacholine compared with men ( P P Conclusions Minimal differences in perception of bronchoconstriction-related symptoms between athletes and nonathletes were observed. Among athletes, the presence of EIB/AHR, older age, and female sex were associated with slightly higher perception scores.
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seasonal variations of cough reflex sensitivity in elite athletes training in cold air environment
Cough, 2012Co-Authors: Julie Turmel, Valérie Bougault, Louis-philippe BouletAbstract:Exercise-induced cough is common among athletes. Athletes training in cold air often report an increasingly troublesome cough during the winter season. Chronic airway irritation or inflammation may increase the sensory response of cough receptors. The aim of this study was to evaluate the seasonal variability of cough reflex sensitivity to capsaicin in elite athletes. Fifty-three elite winter athletes and 33 sedentary subjects completed a respiratory questionnaire and a capsaicin provocation Test during the summer, fall, and winter. Allergy skin prick Tests, spirometry, eucapnic voluntary hyperpnea Test (EVH), methacholine Inhalation Test (MIT), and induced sputum analysis were also performed. In athletes, the prevalence of cough immediately after exercise was high, particularly during winter. Athletes often showed a late occurrence of cough between 2-8 h after exercise. The cough reflex sensitivity to capsaicin was unchanged through the seasons in both athletes and non-athlete subjects. No significant correlations were found in groups between cough reflex sensitivity to capsaicin and the number of years in sport training, the number of hours of training per week, EVH response (% fall in FEV1), airway responsiveness to methacholine (PC20), airway inflammation or atopy. The prevalence of cough immediately and a few hours after exercise is high in athletes and more frequently reported during winter. However, cough does not seem to be associated with cough reflex hypersensitivity to capsaicin, bronchoconstriction, or airway inflammation in the majority of athletes.
Ann J Woolcock - One of the best experts on this subject based on the ideXlab platform.
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house dust mite allergens a major risk factor for childhood asthma in australia
American Journal of Respiratory and Critical Care Medicine, 1996Co-Authors: Jennifer K Peat, Euan R Tovey, Brett G Toelle, Michelle M Haby, E J Gray, A Mahmic, Ann J WoolcockAbstract:If house dust mite allergen (Der p I) is an important cause of asthma, there should be a direct relationship between level of exposure to this allergen and asthma severity. To examine this, we studied six large random samples of children in different regions of New South Wales, Australia. We measured recent wheeze by questionnaire, airway hyperresponsiveness (AHR) by histamine Inhalation Test and sensitization to house dust mites by skin prick Tests. Current asthma was defined as the presence of recent wheeze and AHR. We measured Der p I levels in the beds of approximately 80 children in each region. In regions where Der p I levels were high, more children were sensitized to house dust mites, and these children had significantly more AHR and recent wheeze. After adjusting for sensitization to other allergens, we found that the risk of house dust mite-sensitized children having current asthma doubled with every doubling of Der p I level. There was a modest correlation between AHR and Der p I exposure in in...
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changing prevalence of asthma in australian children
BMJ, 1994Co-Authors: J K Peat, R H Van Den Berg, W F Green, C M Mellis, Stephen R Leeder, Ann J WoolcockAbstract:Abstract Objective : To investigate whether prevalence of asthma in children increased in 10 years. Design : Serial cross sectional studies of two populations of children by means of standard protocol. Setting : Two towns in New South Wales: Belmont (coastal and humid) and Wagga Wagga (inland and dry). Subjects : Children aged 8-10 years: 718 in Belmont and 769 in Wagga Wagga in 1982; 873 in Belmont and 795 in Wagga Wagga in 1992. Main outcome measures : History of respiratory illness recorded by parents in self administered questionnaire; airway hyperresponsiveness by histamine Inhalation Test; atopy by skin prick Tests; counts of house dust mites in domestic dust. Results : Prevalence of wheeze in previous 12 months increased in Belmont, from 10.4% (75/718) in 1982 to 27.6% (240/873) in 1992 (P Conclusions : We suggest that exposure to higher allergen levels has increased airway abnormalities in atopic children or that mechanisms that protected airways of earlier generations of children have been altered by new environmental fators.
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importance of house dust mite and alternaria allergens in childhood asthma an epidemiological study in two climatic regions of australia
Clinical & Experimental Allergy, 1993Co-Authors: J K Peat, Stephen R Leeder, Euan R Tovey, Craig Mellis, Ann J WoolcockAbstract:The relation of house dust mite allergen levels to asthma and allergy was examined in two population samples of children aged 8-11 years in northern New South Wales. We studied 805 children in Lismore (a hot, humid, coastal region) and 770 in Moree/Narrabri (a hot, dry inland region). Respiratory symptoms were measured by questionnaire, bronchial hyperresponsiveness (BHR) by histamine Inhalation Test, and allergy by skin-prick Tests. Current asthma was defined as the presence of both wheeze in last 12 months and BHR. Der p I levels were measured in dust from the bed and floors in the homes of 57 randomly selected children in the coastal region and of 74 inland children. Der p I levels were significantly higher by the coast (83.0 vs 11.2 microg/g, P < 0.001). House dust mite sensitivity was of similar prevalence in both regions (28.6 vs 26.4%, n.s.) but Alternaria sensitivity was higher inland (4.0 vs 15.2% P<0.001). Bronchial responsiveness was more severe in coastal children sensitized to house dust mites and in inland children who were sensitized to Alternaria. The adjusted odds ratios for current asthma in children sensitized to house dust mites were 21.3 (95% CI 10.5, 43.2) by the coast and 2.7 (95% CI 1.3, 5.4) inland, and in children sensitized to Alternaria were 3.4 (95% CI 1.3, 9.1) in the coastal region and 5.6 (95% CI 3.1, 10.1 inland. These studies suggest that high house dust mite allergen levels in a humid, subtropical region act to significantly increase bronchial responsiveness in sensitized children, and that Alternaria allergens have a similar but less potent action in a dry, rural region.