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Biomedical subjects

H Turcotte

Publications and source records attributed to H Turcotte.

At least 37 records · Page 2Linked to original sources
PubMed1994

Five-year changes in airflow obstruction and airway responsiveness in mild to moderate asthma.

We documented changes in airflow obstruction and airway responsiveness to histamine after a period of 5 +/- 1 y in 40 subjects with mild to moderate asthma, 14 men and 26 women, aged 20-68 y (mean: 43.6 y). Asthma had to be stable at both evaluations. Each subject answered a respiratory questionnaire and expiratory flows and airway responsiveness to histamine were measured. No significant difference was found between the sub-groups based on atopic status and medication use for mean 5-y changes in FEV1 or PC20. However, although severity of asthma was similar in both groups, the number of subjects who significantly increased their FEV1 or PC20 at 5 y tended to be higher in the group using corticosteroids regularly (> 9 months/y): FEV1: 35.7%, PC20: 42.9% compared to those using them intermittently (< 3 months/y): FEV1: 23.3%, PC20: 35.3% (p > 0.05). This difference was related to recent (< 6 months) use of inhaled corticosteroids. On the other hand, the number of subjects with a significant reduction in FEV1 or PC20 after 5 y was lower when inhaled corticosteroids were used regularly: FEV1: 14.3%; PC20: 28.6%, compared to intermittently: FEV1: 41.2%; PC20: 41.2%, although this difference was not statistically significant. Changes in FEV1 or PC20 at 5 y were not correlated with the duration of asthma, the number of months on inhaled corticosteroids, or age at the time of diagnosis. Airway responsiveness was most often improved in atopics compared to non-atopics. In conclusion, overall 5-y changes in FEV1 or PC20 in our group of subjects were minimally influenced by the duration of the asthma and age at the time of diagnosis. The number of subjects with improved airway responsiveness was higher among atopics and after regular use of inhaled corticosteroids. Further prospective studies should be done on the long-term influence of regular vs. intermittent use of inhaled corticosteroids on the natural history of asthma.

Administration, Inhalation↗
PubMed1993

Influence of natural antigenic exposure on expiratory flows, methacholine responsiveness, and airway inflammation in mild allergic asthma.

BACKGROUND: This study looked at respiratory symptoms, peak expiratory flow rates (PEFRs), airway responsiveness to methacholine and inflammatory changes on bronchial biopsies, bronchial lavage (BL), and bronchoalveolar lavage (BAL) during natural antigenic exposure in nine subjects with pollen-sensitized seasonal asthma. METHODS: The subjects recorded daily symptoms of asthma, cough and rhinitis, and morning and evening PEFRs between January and September, during and out of the pollen exposure. Baseline forced expiratory volume in 1 second, forced vital capacity, and methacholine responsiveness were measured every 3 to 4 weeks. BAL, BL, and bronchial biopsies were performed in the pollen season at the initial increase of asthma symptoms and out of pollen exposure. RESULTS: At the time of bronchoscopy during the pollen season compared with out of season, asthmatic subjects had an increase in asthma symptom score (1.18 +/- 0.24/0.44 +/- 0.18, p < 0.05), a reduction of PEFR (407 +/- 23/442 +/- 20 L/min, p = 0.02), and a decrease in PC20 (1.15/1.48 mg/ml, p = 0.05). In asthmatic subjects, median BAL and BL cell counts and cell differentials during or out of antigenic exposure were similar, but BAL and BL eosinophils and metachromatic cells counts were always higher than in healthy subjects. In comparison with controls, biopsies obtained in asthmatic subjects showed airway lesions such as epithelial desquamation, squamous cell metaplasia, thickening of basal membrane, inflammatory cells (p < 0.05 for neutrophils), edema, and ciliary abnormalities. During pollen exposure, inflammatory signs increased, but this change was only significant for the extent of epithelial desquamation and neutrophil counts. No significant correlation was found between the intensity of airway inflammation and changes in airway responsiveness. CONCLUSIONS: In subjects with mild allergic asthma and pollen-induced asthma, seasonal antigenic exposure was associated with an increase in epithelial shedding and in the number of neutrophils on bronchial biopsies, suggesting a mild increase in baseline airway inflammation. However, these changes were not correlated with increases in airway responsiveness.

Adult↗
PubMed1993

Perception of acute or progressive resistive loads in normal and asthmatic subjects.

To determine if the rapidity of increase in airway resistance influences its perception, we looked at the perception of acute and progressive expiratory resistive loads in 9 controls (CN) and 9 asthmatics (AS). Each had 4 single-blind tests in a randomized order, during which resistances were increased from 0 to 24 cm H2O/l/s in 1, 3 or 6 steps or decreased in 6 steps. Dyspnea scores were recorded on a modified Borg scale (0-10). FEV1 and lung volumes were measured in all subjects initially and after the last resistance applied during tests C and D. Tidal volume, respiratory rate, the ratio of inspiratory time over total breathing time (Ti/Ttot) and minute ventilation were measured throughout each test. Borg scores were not significantly different from one test to the other. Overall, AS tended to have a higher perception of resistive loads than CN, although it did not reach statistical significance. FEV1 did not change significantly in both groups between the tests and before and after application of resistances. Functional residual capacity was not significantly different between AS and CN or before and after the tests. Residual volume was higher in AS (mean of the 4 tests: 1.6 +/- 0.05 l) compared to CN (1.1 +/- 0.14 l) (p = 0.003) but was unchanged after the applied resistances. Ti/Ttot ratio was similar for AS and CN and decreased significantly from 0 to 24 cm H2O/l/s in both groups (all tests, p < 0.01). Respiratory rate was higher in CN than in AS at all resistances (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Perception of breathlessness during early and late asthmatic responses.

We looked at the perception of breathlessness associated with bronchoconstriction during early (EAR) and late (LAR) asthmatic responses to inhaled antigens and its correlation with the rate of fall of expiratory flows. Twenty-eight asthmatics were studied (12 male, 16 female, 18 to 38 yr of age). Breathlessness was evaluated on a modified Borg scale (0 to 10) before each FEV1 measurement, obtained at regular intervals for as long as 8 h after the antigen challenge. The rate of the fall in FEV1 was calculated from the maximal percent fall obtained during the EAR or the LAR and the time lapse from the onset of the reaction to the maximal fall in FEV1. Ten subjects had an isolated early and 18 had a dual asthmatic response after allergen challenge. Dual responders perceived a similar percent fall in FEV1 (mean percent fall: EAR, 20.7 +/- 1.6%; LAR, 21.5 +/- 1.6%) more intensely during the EAR than during the LAR, with median Borg scores (range) of, respectively, 2.0 (0.5 to 4) and 0.5 (0 to 3.0) (n = 18, p < 0.001). The median rate of the fall in FEV1 was: EAR, 2.09 (0.77 to 6.6) %/min; LAR, 0.11 (0.05 to 0.36) %/min (n = 18, p < 0.001). The rate of the fall in FEV1 during either EAR or LAR was strongly correlated with the Borg scores; the slower the fall, the weaker the perception (p < 0.001). We conclude that LAR are poorly perceived compared with EAR and that this may be due to the temporal adaptation to the slow and progressive bronchoconstriction in LAR.

Adolescent↗
PubMed1992

Influence of a single antigenic challenge on the pattern of airway response to exercise in asthma.

We studied 14 atopic subjects with mild asthma (six men and eight females) to document whether allergen exposure can change the pattern of response to exercise. Each had an exercise test at 80% of the VO2 max for six minutes before (exercise 1) and 48 hours (exercise 2) after an allergen inhalation test (AIT). FEV1 was measured at regular intervals up to eight hours after each challenge. On the day following AIT, spontaneous changes in FEV1 were measured for eight hours (control day). Airway responsiveness (AR) to histamine was measured at the beginning of the study, then 24 hours after AIT and at the end of the 2nd exercise. Mean early fall in FEV1 after exercise 1, AIT and exercise 2 were, 24.9 +/- 3.2%, 24.5 +/- 2.2%, and 27.6 +/- 3.8%, respectively. Airway responsiveness to histamine was increased at 32 and 56 hours post-AIT with a mean PC20 (SEM) of 0.50 (0.40, 0.62) and 0.93 (0.74, 1.17) mg/mL compared with 1.87 (1.33, 2.61) at baseline (P less than .05). Allergen inhalation test induced an isolated early asthmatic response (EAR) in four subjects, an equivocal response (late fall in FEV1: 5% to 15%) in four and a definite late asthmatic response (LAR) in six. No subject had a LAR before the AIT but two with a LAR after allergen exposure developed a late response to exercise after the AIT. This last was only partly explained by an increased diurnal variation of expiratory flows.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Near-fatal asthma: clinical and physiologic features, perception of bronchoconstriction, and psychologic profile.

We studied 19 subjects with asthma (11 men and eight women, aged 20 to 66 years), 6 months to 5 years after a near-fatal (NF) episode of asthma (NF group). Mean duration of asthma was 16.3 +/- 2.4 years. On reevaluation, all subjects were using an inhaled beta 2-agonist and inhaled steroids (mean daily dose of budesonide, 1070 micrograms [N = 5], and beclomethasone, 1079 micrograms [N = 14]). Two subjects were taking prednisone, 10 and 15 mg/day. Subjects were matched for age, sex, atopic status, baseline FEV1, and medication use to a control group (C group) of subjects with asthma who had never experienced an NF asthma episode. All subjects had the following evaluation: (1) questionnaire on the characteristics of their asthma, (2) spirometry, (3) morning and evening measurements of peak expiratory flow rates (PEFR) with daily recordings of asthma symptoms for 4 weeks, and (4) psychometric evaluation with the Minnesota Multiphasic Personality Inventory. Ten subjects of the NF group and 13 of the C group had a methacholine challenge with scoring of dyspnea on a modified Borg scale. Mean percent predicted (+/- SEM), FEV1, FVC, and PEFR were similar for the NF and C groups with respective values of 63.4 (4.4), 61.3 (5.6), 81.1 (4.5), 79.1 (3.8), 61.3 (5.6), and 62.4 (6.1). Geometric mean of the provocative concentration of methacholine causing a 20% drop in FEV1 (milligrams per milliliter) was 0.61 for the NF group (N = 10) and 1.18 for the C group (N = 13).(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis, Respiratory↗
PubMed1991

Relationship between changes in diurnal variation of expiratory flows, lung volumes and respiratory symptoms after acute asthma.

We looked at the comparative recovery of asthma symptoms and changes in airflow obstruction after an acute exacerbation of asthma in 26 asthmatics, aged 18-69 years (mean = 43). In the 4 weeks following the acute episode, they recorded their respiratory symptoms and twice-daily peak expiratory flow rates (PEFR). In 14 subjects, lung volumes were also measured on days 1, 7 and 30. Mean initial FVC and FEV1 [+/- SEM (% predicted)] were 2.30 +/- 0.16 (61%) and 1.18 +/- 0.08 (39%). The rate of improvement of airflow obstruction initially paralleled that of asthma symptoms in subjects with mild or with a recent onset of asthma. On the first study day, diurnal variation of PEFR was minimal, increased rapidly during the first week of treatment and stabilized thereafter. Mean daily delta PEFR was significantly higher in the first than at the fourth week (P = 0.005). Recovery of asthma symptoms was associated with an overall reduction in FRC and RV but there was no significant correlation between FRC or RV and dyspnea score or PEFR. Perception of airflow obstruction was generally lower, improvement of symptoms slower and of smaller amplitude in those with long-standing asthma. In conclusion, during recovery from acute asthma: (1) diurnal variation of PEFR is initially minimal, increases rapidly after beginning steroids and stabilize in the two following weeks; (2) in patients with more than mild or long-standing asthma, and magnitude and range of perception of asthma symptoms is reduced and correlates less with PEFR; and (3) no significant correlation could be found between FRC or RV and dyspnea score or PEFR.

Acute Disease↗
PubMed1991

Influence of water content of inspired air during and after exercise on induced bronchoconstriction.

This study looked at the influence of inspired air water content on exercise-induced bronchospasm (EIB). On separate days, 12 mild asthmatics (4M, 8F), aged 18-39 yrs (mean: 27 yrs), performed four six minute steady-state exercises on ergometer at 80% of their maximum workload. Exercises were randomized to the following inspired air conditions: dry air (0% relative humidity (RH] during exercise followed by dry (DD) or humid air (100% RH) (DH) after exercise, humid air during exercise followed by dry (HD) or humid air (HH). Room temperature was kept constant (22 +/- 1 degree C) at all visits. Forced expiratory volume in one second (FEV1) was measured before and every 5 min for 25 min after exercise. Ventilation (VE) was not significantly different whether the exercise was done under dry or humid air. There was a residual bronchodilatation at the end of exercises performed in humid air, while at this time FEV1 was already lower than baseline when exercise was done in dry air conditions. The maximal fall in FEV1(%) following exercise was significantly greater after those performed in dry air: DD (29 +/- 5.6%) and DH (30 +/- 5.8%) than in humid air: HD (12 +/- 4.9%) and HH (20 +/- 4.9%) (p less than 0.05). The time-course of recovery from bronchoconstriction was significantly improved when inhaling dry air after exercise. However, the difference found in the maximal % fall in FEV1 after exercise when recovery was in dry compared to humid air did not achieve statistical significance. In conclusion, EIB is influenced by the changes in water content during and after exercise. Bronchoconstriction following exercise is minimal if exercise is done in humid air and recovery in dry air, and maximal if the exercise is performed in dry air and recovery in humid air.

Adolescent↗
PubMed1991

Hyperosmolarity-induced increases in airway responsiveness and late asthmatic responses.

Airway responsiveness to inhaled methacholine was assessed before and after bronchial challenge with ultrasonically nebulized hyperosmolar saline (UNHS), and these changes were correlated with the development of late asthmatic responses (LAR). Sixteen subjects with mild to moderate asthma had two consecutive methacholine challenges before and one after a cumulative-dose challenge with UNHS. Twelve of these subjects also had a single-dose hyperosmolar challenge to document the occurrence of LAR and determine if UNHS had a significant cumulative-dose effect. If a LAR was observed, a control day without challenge completed the study. Responsiveness to methacholine was similar on the 2 baseline methacholine challenges with a provocative concentration producing a 20% fall in forced expiratory volume in one second (PC20) (mean +/- SEM) of 1.11 +/- 0.94 and 1.16 +/- 0.94 mg.ml.1 (r: 0.98). However, it was significantly increased after the inhalation of UNHS with a PC20 (mean +/- SEM) of 0.57 +/- 1.00 mg.ml.1 (p less than 0.001). Two subjects developed a late fall in forced expiratory volume in one second (FEV1) of 19 and 46% after hyperosmolar challenge. In this last subject, the LAR, not reproduced on the control day, was associated with a marked post-UNHS change in PC20, going from a baseline of 4.4 to 0.7 mg.ml.1 after UNHS. The % fall in FEV1 following the dose-response hyperosmolar challenge and the single-dose hyperosmolar challenge were not different, with mean values +/- SEM of 34.9 +/- 2.2 and 35.8 +/- 4.1, respectively, (p greater than 0.5). In conclusion, airway responsiveness to methacholine may increase following hyperosmolar saline inhalation, often unrelated to LAR.

Adult↗
PubMed1990

Influence of natural antigenic exposure on bronchoalveolar lavage in subjects with pollen-induced rhinitis.

To determine if atopic subjects without asthma naturally exposed to antigens to which they are sensitized demonstrate evidence of lower airway inflammation, we studied 10 subjects with recurrent seasonal allergic rhinitis to pollens. Each subject had a monthly methacholine challenge and two bronchoalveolar lavages (BAL), one during symptoms of allergic rhinitis and one out of season. The percentage of macrophages, lymphocytes, neutrophils, eosinophils, and mast cells in the lavage fluid were determined on Diff-Quik, nonspecific esterase, or toluidine blue-stained cytocentrifuge preparations. The total number of cells recovered on BAL was 23.2 +/- 3.5 X 10(6) (mean +/- SEM) (13.3 +/- 2.3 X 10(4) cells per milliliter) in season, during symptoms of allergic rhinitis, and 33.8 +/- 7.4 X 10(6) (15.2 +/- 3.1 X 10(4) cells per milliliter) out of season (p greater than 0.05). BAL cell-differential counts (percent) in/out season were similar for macrophages (89.0/84.6), lymphocytes (9.1/12.8), neutrophils (1.3/2.1), eosinophils (0.5/0.5), epithelial cells (0.37/0.46), and mast cells (0.0008/0.0013). Blood eosinophil counts, taken, respectively, in and out of season, were 135.5 +/- 26.8 X 10(6)/L and 102.8 +/- 20.6 X 10(6)/L (p greater than 0.05). Although overall airway responsiveness increased slightly during the pollen season, it did not reach statistical significance (geometric mean of provocative concentration causing a 20% fall in FEV1 [milligrams per milliliter], 98.8 during antigenic exposure compared to 121.4 out of season) (p greater than 0.05. These observations suggest that in subjects without asthma, no changes in cell differential are detected on BAL at the time of maximal symptoms of allergic rhinitis.

Adult↗
PubMed1990

Perception of breathlessness during bronchoconstriction induced by antigen, exercise, and histamine challenges.

Perception of breathlessness was studied in eight patients with mild, stable asthma after a histamine and exercise challenge performed before and 24 and 48 hours respectively after an antigen challenge. FEV1 and perception of breathlessness, evaluated by Borg's 10 point category scale, were measured after each administration of doubling antigen or histamine concentrations to achieve a greater than 20% fall in FEV1, and after six minutes of steady state exercise at 80% of maximal oxygen consumption (VO2max). The geometric mean provocative concentration of histamine causing a 20% fall in FEV1 (PC20) fell from 1.67 mg/ml before antigen challenge to 0.52 mg/ml 24 hours after the challenge. The median maximal % fall in FEV1 with exercise was 24.9% (range 10.5-40.5%) before and 30.6% (range 13.8-52.3%) 48 hours after antigen challenge. The median maximum % fall in FEV1 after antigen inhalation was 20.1% (range 13.3-35.2%) within the first hour; only two subjects had a late fall in FEV1 (23% and 58%). The median (range) of Borg scores obtained when FEV1 was reduced by 20% did not differ significantly for the three types of acute challenges: 1.25 (0.5-2.5) and 1.0 (0.5-3.0) after histamine tests, 1.0 (0.5-4.1) and 1.55 (0.5-2.0) after exercise, and 1.5 (0-3.0) after antigen challenge. In the two subjects who had a late response to antigen the Borg score was reduced for the same % fall in FEV1 as with the early response. It is concluded that the perception of breathlessness does not differ appreciably during the early response to histamine, antigen exposure, or exercise, but that it is reduced during the late asthmatic response. It was not influenced by previous antigen exposure, despite an increase in airway responsiveness.

Adolescent↗
PubMed1990

Variations of airway responsiveness to methacholine and exercise in asthmatic and normal subjects over a 12-month period.

This study looked at seasonal fluctuations of airway responsiveness (AR) to methacholine and exercise in ten mild asthmatic and seven normal subjects. Each subject had a monthly methacholine inhalation test. An exercise challenge with measurement of expiratory flows was performed initially in the fall (F), then in winter (W), and in summer (S). Throughout the study, the subjects were asked to record on a diary card twice daily peak flow rates and respiratory symptoms, one week a month. Airway responsiveness to exercise and methacholine remained generally stable throughout the year, although an increase in respiratory symptoms occurred during fall and winter. The overall AR to methacholine was not significantly different during the different seasons (F, W, S and Spring) with the methacholine concentration producing a 20% fall in FEV1, PC20 (mg/ml) values, respectively, of 1.7 +/- 1.2 mg/ml, 1.8 +/- 1.1, 2.1 +/- 1.2, and 2.0 +/- 1.9 for asthmatics and 79.0 +/- 1.2 mg/ml, 66.8 +/- 1.0, 87.3 +/- 1.0, and 73.1 +/- 1.0 for normals. However, short term variations in AR were associated to exposure to antigens and cold weather. Mean daily peak expiratory flows remained generally stable through the seasons. On the three exercise tests, the VO2 max and the mean % fall in FEV1 after maximal exercise showed large variations; these, however, were not significantly different (mean fall: 16.2% (F), 16.6% (W), and 14.7% (S) in asthmatics). In conclusion, although it may increase transiently, overall airway responsiveness to methacholine and exercise remains generally stable in asthmatic and normal subjects throughout the year.

Adult↗
PubMed1989

Comparative efficacy of salbutamol, ipratropium, and cromoglycate in the prevention of bronchospasm induced by exercise and hyperosmolar challenges.

We compared the inhibitory effects of inhaled salbutamol (S), ipratropium (I), and cromoglycate (C) on bronchospasm induced by exercise (EX) or hyperosmolar (HY) saline aerosol in a group of 11 subjects with stable asthma. Each subject had eight tests in a randomized order, four EX and four HY challenges, each preceded by the double-blind inhalation of either a placebo, 200 micrograms of S, 80 micrograms of I, or 4 mg of C. This study demonstrated that the three drugs protected against the two types of challenges in almost all subjects. Although we observed a large interindividual variability in the airway response to the challenges, there was no statistically significant difference in the mean percent protection after HY or EX challenges when these challenges were preceded by S, I, or C (p greater than 0.05). Moreover, for EX- and HY-induced bronchospasm, the mean percent protection afforded by the three medications was in the same order (S greater than I greater than C), although the protective effect against EX-induced was weaker than against HY-induced bronchospasm. This suggests that hyperosmolarity, although it may not be the sole factor involved, plays a role in EX-induced bronchospasm.

Adult↗
PubMed1989

Bronchial responsiveness increases after seasonal antigen exposure in non-asthmatic subjects with pollen-induced rhinitis.

This study looked at the effects of natural antigenic exposure on non-specific airway responsiveness (NSAR) in pollen-sensitized non-asthmatic subjects with seasonal rhinitis. Eight subjects had daily recordings of their respiratory symptoms and peak flow rates during and out of the pollen season. Airway response to methacholine was measured at 1-week to 2-week intervals. Pre-season spirometry and NSAR were normal in all subjects. Their PC20 methacholine ranged from 64 to greater than 256 mg/mL. During natural pollen exposure, all subjects had symptoms of rhinoconjunctivitis. The only chest symptom observed was coughing. No significant change in peak flow rates was observed throughout the study. A significant increase in bronchial responsiveness to methacholine occurred in five subjects although it did not reach the asthmatic range (less than 16 mg/mL). This change in NSAR was reproduced after antigen (tree pollen) challenge in the laboratory in one of the subjects. A significant increase in blood eosinophils was observed during seasonal pollen exposure. This study shows that following natural antigenic exposure, NSAR can increase in non-asthmatic subjects with allergic rhinitis, although it may not reach the "hyperresponsive range," and is associated with the development of a cough. These data suggest that natural exposure in non-asthmatic atopics may induce an inflammatory reaction in the airways to a degree that may increase NSAR.

Adult↗
PubMed1987

Prevalence and characteristics of late asthmatic responses to exercise.

The prevalence and characteristics of late asthmatic responses to exercise were studied in an adult asthmatic population. Twenty-four subjects (eight male and 16 female), aged 17 to 39 years (mean, 23.7 years), performed a 6-minute exercise on a bicycle ergometer at 75% of their maximum oxygen intake. FEV1 was measured at regular time intervals up to 8 hours after exercise. Seven subjects demonstrated a late asthmatic reaction defined as a fall in FEV1 greater than 10% between 2 to 8 hours. Bronchial reactivity to histamine was unchanged 24 hours after the exercise, compared to baseline. On a control day, a fall in FEV1 similar to the one observed after exercise was induced by methacholine inhalation. Measurements of FEV1 were done at the same time intervals as on exercise day. Neutrophil chemotactic activity was measured in the serum of 15 subjects, on exercise day for early responders, and on the 3 test days for subjects with a dual response. There was no difference between subjects with an isolated early or late response for age, sex, or atopic status. Baseline expiratory flows and nonspecific bronchial reactivity to histamine were similar in both groups. These results demonstrate the occurrence of a late asthmatic response in 30.4% of the population studied. There was no significant change of nonspecific bronchial responsiveness after the late asthmatic response to exercise. No significant increase in neutrophil chemotactic activity could be observed.

Adolescent↗
PubMed1987

Comparative bronchial responses to hyperosmolar saline and methacholine in asthma.

Airway responsiveness to inhaled methacholine and to ultrasonically nebulised hyperosmolar saline was compared in 20 asthmatic subjects. Each subject had two hyperosmolar inhalation tests and a methacholine challenge in random order at least 48 hours apart over a period of two weeks. Hyperosmolar challenge, carried out with doubling concentrations of saline from 0.9% to 14.4% to obtain a dose-response curve, was well tolerated by all subjects. The response to hyperosmolar saline--expressed as the PO20, the osmolarity inducing a 20% fall in forced expiratory volume in one second (FEV1) was obtained in 16 of the 20 subjects and in each was repeatable to within one doubling concentration of saline. The peak bronchoconstrictor effect of hyperosmolar saline inhalation occurred at 3 minutes and its mean total duration (FEV1 less than 90% of baseline) was 50 minutes. There was no significant correlation between the PO20 and the PC20 methacholine (the concentration inducing a 20% fall in FEV1). Thus by using a new method to obtain a quantitative airway response to inhaled hyperosmolar saline we found that the airway response to hyperosmolar inhalation differs from the airway response to methacholine.

Administration, Inhalation↗
PubMed1987

Bronchial responsiveness to histamine after repeated exercise-induced bronchospasm.

The effects of repeated exercise-induced bronchospasm on nonspecific (nonallergenic) bronchial responsiveness (NSBR) to histamine were studied in 12 asthmatic patients (6 F, 6 M). Baseline NSBR, determined by the provocative concentration of histamine giving a 20% fall in FEV1 (PC20), ranged from 0.41 to 10.2 mg/ml (geometric mean +/- SD: 2.6 +/- 2.5). Each subject performed three consecutive exercises on the ergometer for 6 min at 70% of their VO2 max. Each test was preceded and followed by a histamine inhalation test (HIT). On a control day, 4 HIT were done at 1 h interval, without intercurrent exercise. A significant reduction in histamine responsiveness was observed on control day from the first to the fourth HIT. On exercise day, a mean percent fall in FEV1 of 19.4 +/- 12.9, 16.2 +/- 12.2 and 15.8 +/- 12.7 was observed after the three consecutive exercises but no significant difference could be found between the four PC20 measurements. Four subjects showed refractoriness to the second exercise and no change in the bronchial response to histamine was observed during the refractory period. In conclusion, (1) repeated exercises do not change NSBR; (2) the refractory period after exercise is not due to a change in NSBR, and (3) a tachyphylaxis to histamine occurs in some subjects after repeated inhalations of histamine.

Adult↗