Bronchial responsiveness to inhaled histamine and isoprenaline in patients with airway obstruction

In order to examine the hypothesis that bronchial reactivity to non-specific constrictor stimuli is influenced by the resting tone of the bronchial smooth muscle, the airway responses to inhaled histamine solution and inhaled isoprenaline were measured in 19 patients with airway obstruction. There was a significant positive correlation between the size of the constrictor response to histamine and the dilator response to isoprenaline (r = +0.83; p less than 0.01) as measured by changes in specific airway conductance. Patients with asthma showed greater bronchial reactivity to both histamine and isoprenaline than those with chronic bronchitis, although some patients had changes intermediate between the two extremes.     

The effect of inhaled frusemide on airway sensitivity to inhaled 4.5% sodium chloride aerosol in asthmatic subjects.

BACKGROUND: Frusemide inhaled by asthmatic subjects before a variety of indirect bronchial challenges inhibits the airway response to these challenges. Since inhalation of hyperosmolar saline is an indirect bronchial challenge, the effect of inhaled frusemide and its vehicle on airway sensitivity to a 4.5% sodium chloride (NaCl) aerosol challenge was investigated. METHODS: Eleven asthmatic subjects (five females, six males) who had a 20% fall in forced expiratory volume in one second after 4.5% NaCl challenge were enrolled in this double blind controlled crossover trial. Sensitivity was measured as the dose of aerosol required to provoke a 20% fall in FEV1. Frusemide (33.2 mg) or its vehicle was delivered through a Fisoneb ultrasonic nebuliser and inhaled 10 minutes before challenge with 4.5% NaCl. A Mistogen ultrasonic nebuliser was used to generate the 4.5% NaCl aerosol and FEV1 was measured before and one minute after each challenge period of 0.5, one, two, four, eight, eight and eight minutes. The doubling dose difference for PD20 was calculated. RESULTS: Frusemide or vehicle had no effect on baseline lung function. The geometric mean PD20 after vehicle was 1.3 ml with a 95% confidence interval of 0.7-2.3 and after frusemide was 8.2 ml with a 95% confidence interval of 4.7-14.1. This represented a 2.6 doubling dose increase in PD20 after frusemide inhalation. In five of the 11 subjects an increase from baseline FEV1 occurred after exposure to 4.5% NaCl challenge in the presence of frusemide. This transient bronchodilatation may be caused by the release of prostaglandin E2. CONCLUSION: Inhalation of frusemide is very effective in delaying airway narrowing induced by an aerosol of 4.5% NaCl in asthmatic subjects.     

Effect of regular inhaled salbutamol on airway responsiveness and airway inflammation in rhinitic non-asthmatic subjects

BACKGROUND: Regular, inhaled beta 2 agonists may increase airway responsiveness in asthmatic subjects. The mechanism is not known but may be via an increase in airway inflammation. A study was undertaken to examine the effect of regular inhaled salbutamol on airway responsiveness to methacholine and hypertonic saline, on the maximal response plateau to methacholine, and on inflammatory cells in induced sputum in rhinitic non-asthmatic subjects. METHODS: Thirty subjects with a baseline maximal response plateau of > 15% fall in forced expiratory volume in one second (FEV1) entered a randomised, placebo controlled, parallel trial consisting of two weeks run in, four weeks of treatment, and two weeks washout. Methacholine challenges were performed at the beginning of the run in period, before treatment, after treatment, and after washout. Hypertonic saline challenges were performed before and after treatment and induced sputum samples were collected for differential cell counting. RESULTS: There was no change in airway responsiveness, maximal response plateau to methacholine, or in induced sputum eosinophils or mast cells. The maximum fall in FEV1 after hypertonic saline increased in the salbutamol group (median change 6.0%, interquartile range (IQR) 11.0) but did not change in the placebo group (median change 1.3%, IQR 5.5). CONCLUSIONS: Regular inhaled salbutamol for four weeks increases airway responsiveness to hypertonic saline but does not alter airway responsiveness to methacholine or cells in induced sputum in non-asthmatic individuals with rhinitis. The relevance of these findings to asthmatic subjects has not been established.


     

Effect of inhaled frusemide on responses of airways to bradykinin and adenosine 5'-monophosphate in asthma.

BACKGROUND--Inhaled frusemide exerts a protective effect against bronchoconstriction induced by several indirect stimuli in asthma. This effect could be caused by interference with neural pathways. The effect of inhaled frusemide on bronchoconstriction induced by inhaled bradykinin, which is thought to cause bronchoconstriction via neural mechanisms, was studied and compared with the effects of adenosine 5'-monophosphate (AMP) which probably produces its airway effects by augmenting mast cell mediator release and interfering with neural pathways. METHODS--Patients first underwent AMP and bradykinin challenges. They were then studied in a randomised, placebo controlled, double blind fashion. Ten atopic asthmatic subjects, studied on four days, were pretreated with inhaled frusemide (40 mg) or placebo for 10 minutes, five minutes before challenge with increasing concentrations of nebulised AMP or bradykinin. RESULTS--On the open visit days the provocative concentrations required to reduce forced expiratory volume in one second (FEV1) by 20% from baseline (PC20) for AMP and bradykinin were 16.23 (1.42-67.16) and 2.75 (0.81-6.6) mg/ml. There was a significant correlation between baseline AMP and bradykinin PC20 values. For AMP the geometric mean PC20 values following pretreatment with inhaled frusemide and matched placebo were 80.97 (9.97- > 400.0) and 14.86 (2.6-104.6) mg/ml respectively (95% CI 0.49 to 0.98). For bradykinin the geometric mean PC20 values following pretreatment with inhaled frusemide and matched placebo were 13.22 (2.53- > 16.0) and 2.52 (0.45-5.61) mg/ml respectively (95% CI 0.43 to 1.01). Frusemide afforded 5.45 and 5.24 fold protection against AMP and bradykinin-induced bronchoconstriction respectively. Furthermore, there was a significant correlation between protection afforded to the airways against AMP and bradykinin. CONCLUSIONS--These data suggest that inhaled frusemide affords protection against bradykinin-induced bronchoconstriction which is comparable to that against AMP, supporting a common mechanism of action for frusemide.     

Effect of an inhaled neutral endopeptidase inhibitor, phosphoramidon, on baseline airway calibre and bronchial responsiveness to bradykinin in asthma.

BACKGROUND--Bradykinin is a potent vasoactive peptide which has been proposed as an important inflammatory mediator in asthma since it provokes potent bronchoconstriction in asthmatic subjects. Little is known at present about the potential role of lung peptidases in modulating bradykinin-induced airway dysfunction in vivo in man. The change in bronchial reactivity to bradykinin was therefore investigated after treatment with inhaled phosphoramidon, a potent neutral endopeptidase (NEP) inhibitor, in a double blind, placebo controlled, randomised study of 10 asthmatic subjects. METHODS--Subjects attended on six separate occasions at the same time of day during which concentration-response studies with inhaled bradykinin and histamine were carried out, without treatment and after each test drug. Subjects received nebulised phosphoramidon sodium salt (10(-5) M, 3 ml) or matched placebo for 5-7 minutes using an Inspiron Mini-neb nebuliser 5 minutes before the bronchoprovocation test with bradykinin or histamine. Agonists were administered in increasing concentrations as an aerosol generated from a starting volume of 3 ml in a nebuliser driven by compressed air at 8 1/min. Changes in airway calibre were measured as forced expiratory volume in one second (FEV1) and responsiveness as the provocative concentration causing a 20% fall in FEV1 (PC20). RESULTS--Phosphoramidon administration caused a transient fall in FEV1 from baseline, FEV1 values decreasing 6.3% and 5.3% on the bradykinin and histamine study days, respectively. When compared with placebo, phosphoramidon elicited a small enhancement of the airways response to bradykinin, the geometric mean PC20 value (range) decreasing from 0.281 (0.015-5.575) to 0.136 (0.006-2.061) mg/ml. In contrast, NEP blockade failed to alter the airways response to a subsequent inhalation with histamine, the geometric mean (range) PC20 histamine value of 1.65 (0.17-10.52) mg/ml after placebo being no different from that of 1.58 (0.09-15.21) mg/ml obtained after phosphoramidon. CONCLUSIONS--The small increase in bronchial reactivity to bradykinin after phosphoramidon exposure suggests that endogenous airway NEP may play a modulatory role in the airways response to inflammatory peptides in human asthma.     

Effect of inhaled frusemide and oral indomethacin on the airway response to hypertonic saline challenge in asthmatic subjects

BACKGROUND: Inhaled frusemide inhibits airway narrowing and causes a transient increase in forced expiratory volume in one second (FEV1) during hypertonic saline challenge. This inhibitory effect could be secondary to prostaglandin release during challenge. The involvement of prostaglandins in the inhibitory action of frusemide during challenge with 4.5% NaCl was investigated by premedicating with indomethacin, a prostaglandin synthetase inhibitor. METHODS: Fourteen asthmatic subjects (eight women) aged 26.6 (range 18-56) years participated in a double blind, placebo controlled, crossover study. The subjects attended five times and inhaled 4.5% NaCl for 0.5, 0.75, 1, 1.5, 2, 4, 8, 8, and 8 minutes, or part thereof, or until a provocative dose causing a 20% fall in FEV1 (PD20 FEV1) was recorded. Indomethacin (100 mg/day) or placebo were taken three days before all visits, except control day. The FEV1 was measured and frusemide (38.0 (6.4) mg, pH = 9) or vehicle (0.9% NaCl, pH = 9) were inhaled 10 minutes before the challenge. Bronchodilation was calculated as the percentage rise in FEV1 from the prechallenge FEV1 to the highest FEV1 recorded during the challenge. RESULTS: Frusemide caused a fold increase in PD20 FEV1 compared with the vehicle which was similar in the presence of both indomethacin and placebo (3.7 (95% CI 2.0 to 7.3) versus 3.3 (2.0 to 5.4)). Frusemide, but not vehicle, also caused a transient percentage rise in FEV1 during challenge with 4.5% NaCl which was not blocked by indomethacin (3.6% (1.2 to 6.0)) or placebo (3.1% (1.0 to 5.2)). CONCLUSIONS: Inhaled frusemide inhibited airway narrowing and caused a transient increase in FEV1 during challenge with 4.5% NaCl. These effects were not blocked by indomethacin, which suggests that the inhibitory action of frusemide is not secondary to prostaglandin release.


     

Inhaled frusemide and exercise-induced bronchoconstriction in children with asthma.

BACKGROUND--Nebulised frusemide has been shown to be protective against bronchoconstricting stimuli in adult asthmatic subjects and against cold air challenge in children. Animal studies suggest that inhaled frusemide may be more effective in the young. METHODS--A double blind placebo, controlled, crossover study on the effect on exercise of pretreatment with frusemide (20 mg) from a metered dose inhaler via a large volume spacer (Volumatic) was performed in 12 asthmatic children. Exercise testing consisted of eight minutes of running on a treadmill in an environmentally controlled laboratory. RESULTS--Deterioration in lung function was less after frusemide than after the placebo exercise tests. The mean (95% CI) maximum percentage falls in forced expiratory volume in one second (FEV1) were 14.4% (7.7 to 21.0) for placebo and 5.7% (2.3 to 9.0) for frusemide. CONCLUSIONS--Inhaled frusemide via a metered dose inhaler reduces exercise-induced bronchoconstriction in children.     

Contrasting effects of allergen challenge on airway responsiveness to cysteinyl leukotriene D(4) and methacholine in mild asthma

BACKGROUND: Cysteinyl leukotrienes (cysteinyl-LTs) have been implicated in the pathogenesis of allergen induced airway responses. Airway responsiveness (AR) to inhaled cysteinyl-LTs is dramatically increased following allergen challenge in animal studies. The effect in man has not been evaluated. METHODS: Ten mild steroid-na?ve asthmatic subjects with an isolated early asthmatic response (EAR) and 21 with an additional late asthmatic response (LAR) took part in a randomised controlled crossover study to assess AR to inhaled methacholine (MCh) and cysteinyl-LT D(4) (LTD(4)) 22 and 24 hours, respectively, after allergen challenge. Eight subjects had two further LTD(4) challenges separated by a 2 week washout period to assess the reproducibility of inhaled LTD(4) challenge. RESULTS: In subjects with an isolated EAR, non-significant mean (SE) increases in AR of 0.4 (0.4) doubling doses (DD) for MCh and 0.4 (0.5) DD for LTD(4) followed allergen challenge compared with control. A significant correlation between AR to MCh and LTD(4) followed both control (r=0.91, 95% CI 0.67 to 0.98; p=0.0002) and allergen challenge (r=0.79, 95% CI 0.32 to 0.95; p=0.0063). In subjects with an additional LAR there was a significant increase in AR to MCh (1.2 (0.3) DD, p=0.0005) following allergen challenge but no overall effect on AR to LTD(4) (0.69 (0.4) DD, p=0.11). A significant correlation between AR to MCh and LTD(4) was again observed (r=0.70; 95% CI 0.38 to 0.87; p=0.0004) following control, although it was reduced following allergen challenge (r=0.48; 95% CI 0.063 to 0.76; p=0.027). LTD(4) challenge was highly reproducible with a mean difference of 0.2 (0.3) DD between challenges. CONCLUSIONS: Allergen challenge significantly increases AR to inhaled MCh but not to LTD(4) in subjects with LAR. The lack of a comparable increase in AR to LTD(4) is surprising. Endogenous cysteinyl-LTs are produced in abundance following allergen challenge and may enhance AR to MCh or induce a degree of tachyphylaxis to LTD(4).     

Effect of inhaled frusemide on the early response to antigen and subsequent change in airway reactivity in atopic patients.

The purpose of this study was to investigate whether inhaled frusemide was able to inhibit the increase in nonspecific bronchial reactivity that occurs after the early response to allergen exposure in subjects with allergic rhinitis or asthma (or both). Ten symptom free patients initially underwent a challenge with methacholine, to determine the dose of methacholine that caused a 15% fall in FEV1 (PD15 FEV1 meth) and a challenge with a specific allergen, to determine the concentration of allergen that caused a fall in FEV1 of at least 15%. On two further occasions they inhaled allergen concentration that had caused the greater than or equal to 15% fall in FEV1 preceded by inhaled frusemide (40 mg frusemide in 4 ml buffered saline) or placebo (4 ml of diluent solution), according to a randomised, double blind, crossover design. All allergen studies were separated by at least seven days. A methacholine challenge was performed two hours after the allergen challenge, a time when the early response to allergen had completely resolved. Frusemide inhibited the early response to antigen, causing mean (95% confidence interval) protection of 87.6% (96-80%) for the maximum fall in FEV1. The increase in non-specific airway reactivity that occurred after antigen when this was preceded by placebo was reduced by frusemide. The mean (95% CI) difference in PD15 values between the placebo and the frusemide days was 1.73 (2.30-1.16) doubling doses of methacholine. These results confirm that frusemide is highly effective in preventing the early response to allergen, and show that it inhibits the increase in reactivity to methacholine that follows the early response.     

Perception of airway narrowing during reduction of inhaled corticosteroids and asthma exacerbation

BACKGROUND: The perception of airway narrowing is reduced in subjects with severe asthma and may be related to the severity of airway inflammation. A study was undertaken to determine if the perception of airway narrowing changes during the reduction of inhaled corticosteroid (ICS) dose or during an asthma exacerbation. METHODS: Forty two asthmatic subjects with well controlled asthma had their daily ICS dose halved every 2 months until they were weaned off ICS or they developed an exacerbation. Perception was measured at baseline and at monthly intervals during bronchial challenge with mannitol as the slope and intercept of the regression of the Borg score and percentage fall in forced expiratory volume in 1 second (FEV(1)), and as the Borg score at 20% fall in FEV(1) (PS(20)FEV(1)). Sputum was collected for measurement of inflammatory cell numbers. RESULTS: In 33 subjects who successfully halved their ICS dose without exacerbation there were significant reductions in slope (p = 0.01), intercept (p = 0.01), and PS(20)FEV(1) (p = 0.003). Sputum eosinophils and airway hyperresponsiveness increased significantly but, in 14 subjects from whom sputum was obtained, changes in eosinophils were not correlated with changes in perception. Change in airway hyperresponsiveness correlated with change in PS(20)FEV(1) (r = -0.40, p = 0.025). In 27 subjects who developed an exacerbation, slope decreased (p = 0.02) and intercept increased (p = 0.01) compared with the visit before the exacerbation. Changes in intercept correlated with changes in resting FEV(1) (r = -0.57, p = 0.002). CONCLUSIONS: Perception of airway narrowing decreases during ICS dose reduction and decreases further during a mild asthma exacerbation. These changes are related to concurrent changes in airway hyperresponsiveness and resting lung function. The effect of changes in airway inflammation on perception is unclear.     

Relationship between the acid-induced cough response and airway responsiveness and obstruction in children with asthma.

BACKGROUND: In children with asthma little is known about the direct effect of the bronchoconstrictor and bronchodilator response on the cough threshold, or the relationship between bronchial responsiveness and the cough threshold. A study was undertaken to determine the effect of histamine-induced bronchoconstriction and salbutamol-induced bronchodilatation on the cough threshold in response to inhaled acetic acid, and to examine the relationship between the acetic acid cough threshold and bronchial hyperresponsiveness to histamine in children with asthma. METHODS: Nineteen children with asthma (16 boys) of mean (SE) age 10.6 (0.6) years were enrolled in the study. On day 1 each underwent a histamine inhalation challenge to determine the provocative concentration causing a fall in forced expiratory volume in one second (FEV1) of more than 20% (PC20) as an index of individual bronchial hyperresponsiveness. On day 2 the acetic acid cough threshold was determined before and just after the inhalation of the PC20 concentration of histamine, and then salbutamol (1 mg/m2) was inhaled to relieve the bronchoconstriction. Ten of the 19 patients (eight boys) of mean age 12.2 (0.7) years also tried acetic acid inhalation challenge just after salbutamol inhalation. RESULTS: There was no relationship between the bronchial responsiveness to histamine and acetic acid cough threshold in these patients. The acetic acid cough threshold after histamine inhalation was similar to that before histamine, although FEV1 decreased after histamine. In the 10 patients who also tried acetic acid inhalation challenge after salbutamol the cough threshold did not change. CONCLUSIONS: These findings suggest that acid-induced cough sensitivity and bronchomotor tone are independently regulated in children with asthma.     

Bronchodilation by an inhaled VPAC(2) receptor agonist in patients with stable asthma

BACKGROUND: The synthetic vasoactive intestinal peptide (VIP) analogue Ro 25-1553 is a selective VIP-PACAP type 2 (VPAC(2)) receptor agonist that causes a bronchodilatory effect in guinea pigs in vivo. The effect of Ro 25-1553 given by inhalation to patients with asthma was studied and compared with that of a long acting beta(2) adrenoceptor agonist. METHODS: Twenty four patients with moderate stable asthma participated in a double blind, randomised, placebo controlled, crossover study. The primary variable was bronchodilatory effect (increase in forced expiratory volume in 1 second, FEV(1)) after inhalation of Ro 25-1553 (100 microg or 600 microg) and formoterol (4.5 microg), respectively. Putative side effects were characterised by monitoring sitting blood pressure, serum potassium, electrocardiography and echocardiography. RESULTS: Inhalation of 600 microg Ro 25-1553 caused a rapid bronchodilatory effect (geometric mean increase in FEV(1) compared with placebo) within 3 minutes of 6% (95% CI 4 to 9), as did inhalation of formoterol (8% (95% CI 5 to 10)). The corresponding maximum bronchodilatory effect during 24 hours was similar for 600 microg Ro 25-1553 (7% (95% CI 4 to 10)) and the reference bronchodilator formoterol (10% (95% CI 7 to 12)). However, for both doses of Ro 25-1553 the bronchodilatory effect was attenuated 5 hours after inhalation whereas formoterol still had a bronchodilatory effect 12 hours after inhalation. Neither Ro 25-1553 nor formoterol produced any clinically relevant side effects. No drug related difference in adverse events was observed. CONCLUSION: Inhalation of a synthetic selective VPAC(2) receptor agonist constitutes a promising approach for bronchodilation in patients with asthma.     

Non-invasive markers of airway inflammation as predictors of oral steroid responsiveness in asthma

BACKGROUND: Sputum eosinophil counts and exhaled nitric oxide (NO) levels are increased in asthma and both measurements fall in response to corticosteroids. METHODS: Exhaled NO levels and sputum eosinophil counts were assessed as non-invasive markers of the response to an oral steroid in 37 patients (19 women) with stable chronic asthma (mean (SD) age 48.6 (12.2) years, asthma duration 25. 9 (17.3) years, and baseline forced expiratory volume in one second (FEV(1)) 76.3 (21.9)% predicted). Spirometric tests, with reversibility to a beta agonist (2.5 mg nebulised salbutamol), and induced sputum (using nebulised 3% saline) were performed at recruitment and following treatment with 30 mg prednisolone/day for 14 days. RESULTS: Baseline NO levels correlated with the percentage improvement in FEV(1) from baseline to the post-steroid, post-bronchodilator value (r(s) = 0.47, p = 0.003), with an NO level of >10 ppb at baseline having a positive predictive value of 83% for an improvement in FEV(1) of > or =15% (sensitivity 59%, specificity 90%). Sputum eosinophilia (> or =4%) had a positive predictive value of 68% (sensitivity 54%, specificity 76%) for an increase in FEV(1) of > or =15%. A combination of sputum eosinophilia and increased NO levels resulted in a positive predictive value of 72% and a negative predictive value of 79% (sensitivity 76%, specificity 75%). CONCLUSION: Exhaled NO levels and sputum eosinophilia may be useful in predicting the response to a trial of oral steroid in asthma.     

Effect of differing doses of inhaled budesonide on markers of airway inflammation in patients with mild asthma

BACKGROUND: It is desirable to prescribe the minimal effective dose of inhaled steroids to control asthma. To ensure that inflammation is suppressed whilst using the lowest possible dose, a sensitive and specific method for assessing airway inflammation is needed. METHODS: The usefulness of exhaled nitric oxide (NO), sputum eosinophils, and methacholine airway responsiveness (PC20) for monitoring airway inflammatory changes following four weeks of treatment with an inhaled corticosteroid (budesonide via Turbohaler) were compared. Mild stable steroid naive asthmatic subjects were randomised into two double blind, placebo controlled studies. The first was a parallel group study involving three groups receiving either 100 micrograms/day budesonide (n = 8), 400 micrograms/day budesonide (n = 7), or a matched placebo (n = 6). The second was a crossover study involving 10 subjects randomised to receive 1600 micrograms budesonide or placebo. The groups were matched with respect to age, PC20, baseline FEV1 (% predicted), exhaled NO, and sputum eosinophilia. RESULTS: There were significant improvements in FEV1 following 400 micrograms and 1600 micrograms budesonide (11.3% and 6.5%, respectively, p < 0.05). This was accompanied by significant reductions in eosinophil numbers in induced sputum (0.7 and 0.9 fold, p < 0.05). However, levels of exhaled NO were reduced following each budesonide dose while PC20 was improved only with 1600 micrograms budesonide. These results suggest that exhaled NO and PC20 may not reflect the control of airway inflammation as accurately as the number of eosinophils in sputum. There were dose dependent changes in exhaled NO, sputum eosinophils, and PC20 to inhaled budesonide but a plateau response of exhaled NO was found at a dose of 400 micrograms daily. CONCLUSION: Monitoring the number of eosinophils in induced sputum may be the most accurate guide to establish the minimum dose of inhaled steroids needed to control inflammation. This, however, requires further studies involving a larger number of patients.     

Effect of inhaled corticosteroids on bronchial responsiveness in patients with "corticosteroid naive" mild asthma: a meta-analysis

BACKGROUND: Inhaled corticosteroids are the most efficacious anti-inflammatory drugs in asthma. International guidelines also advocate the early introduction of inhaled corticosteroids in corticosteroid naive patients. A study was undertaken to assess the effects of inhaled corticosteroids on bronchial hyperresponsiveness in patients with corticosteroid naive asthma by conventional meta-analysis. METHODS: A Medline search of papers published between January 1966 and June 1998 was performed and 11 papers were selected in which the patients had no history of treatment with inhaled or oral corticosteroids. Bronchial responsiveness to bronchoconstricting agents was considered as the main outcome parameter. Doubling doses (DD) of histamine or methacholine were calculated. RESULTS: The total effect size of inhaled corticosteroids (average daily dose 1000 microg) versus placebo in the 11 studies was +1.16 DD (95% confidence interval (CI) +0.76 to +1.57). When only the eight short term studies (2-8 weeks) were analysed the effect size of the bronchoconstricting agent was +0.91 DD (95% CI +0.65 to +1.16). No relationship was found between the dose of inhaled corticosteroid used and the effect on bronchial responsiveness. CONCLUSION: This meta-analysis in patients with corticosteroid naive asthma indicates that, on average, high doses of inhaled corticosteroids decrease bronchial hyperresponsiveness in 2-8 weeks. It remains unclear whether there is a dose-response relationship between inhaled corticosteroids and effect on bronchial hyperresponsiveness.     

Compliance with inhaled asthma medication in preschool children.

BACKGROUND--Previous studies have shown poor compliance with regular drug therapy in children and adults with asthma. In preschool children the parents supervise and are responsible for drug administration, but little is known of compliance in this group. In addition, there are few data on the patterns of drug use of inhaled prophylactic asthma therapy or of the relation between compliance and symptom control. A study was undertaken to address these issues with the hypothesis that parental supervision would result in good compliance. METHODS--The subjects were 29 asthmatic children aged 15 months to five years already established on inhaled prophylactic medication delivered through a large volume spacer. The prescribed drug regimens varied between subjects. This was an observational study using an electronic inhaler timer device to record the date and time of each actuation of the aerosol canister. Diary cards were used for parallel recording of symptoms and parentally reported compliance with a drug regimen. RESULTS--Variable and generally poor compliance was demonstrated with a median of 50% of study days with full compliance (subject range 0-94%) and an overall median of 77% of prescribed doses of therapy taken during the study period. No relation was found between frequency of prescribed regimen and good compliance. Day care was associated with poorer compliance. No relation between good compliance and low symptom scores was found. CONCLUSION--Compliance with inhaled prophylactic therapy is poor in preschool children with asthma whose medication is administered under parental supervision.     

Effect of frusemide on airway smooth muscle contractility in vitro.

Frusemide, an inhibitor of sodium-potassium-chloride (Na-K-Cl) cotransport, has been shown to inhibit the airway response to several constrictor stimuli in asthmatic subjects. The protection seen with frusemide in these studies could be due to an effect on epithelium, inflammatory cells, neural pathways, or airway smooth muscle. To determine whether frusemide inhibits airway smooth muscle contraction, experiments were performed in bovine and human airways in vitro. Fresh bovine tissue was obtained from the abattoir and human tissue from thoracotomy. The effect of 10(-5)M frusemide on histamine, potassium chloride, and hyperosmolar saline induced contractions was studied in bovine tracheal strips without epithelium. Frusemide, at a concentration that specifically inhibits Na-K-Cl cotransport, did not inhibit contraction caused by any of these agents. Frusemide was also without effect on hypertonic saline induced contractions of bovine and human bronchial rings with epithelium intact. These results suggest that modification of Na-K-Cl cotransport does not alter airway smooth muscle contractility and that the protective effect of frusemide on induced bronchoconstriction in vivo is unlikely to be due to a direct effect on airway smooth muscle.     

Effect of inhaled steroids on airway hyperresponsiveness, sputum eosinophils, and exhaled nitric oxide levels in patients with asthma

BACKGROUND: Airway hyperresponsiveness, induced sputum eosinophils, and exhaled nitric oxide (NO) levels have all been proposed as non-invasive markers for monitoring airway inflammation in patients with asthma. The aim of this study was to compare the changes in each of these markers following treatment with inhaled glucocorticosteroids in a single study. METHODS: In a randomised, double blind, placebo controlled, parallel study 25 patients with mild asthma (19-34 years, forced expiratory volume in one second (FEV1) >75% predicted, concentration of histamine provoking a fall in FEV1 of 20% or more (PC20) <4 mg/ml) inhaled fluticasone propionate (500 microg twice daily) for four weeks. PC20 to histamine, sputum eosinophil numbers, and exhaled NO levels were determined at weeks 0, 2, and 4, and two weeks after completing treatment. Sputum was induced by inhalation of hypertonic (4.5%) saline and eosinophil counts were expressed as percentage non-squamous cells. Exhaled NO levels (ppb) were measured by chemiluminescence. RESULTS: In the steroid treated group there was a significant increase in PC20, decrease in sputum eosinophils, and decrease in exhaled NO levels compared with baseline at weeks 2 and 4 of treatment. Subsequently, each of these variables showed significant worsening during the two week washout period compared with week 4. These changes were significantly different from those in the placebo group, except for the changes in sputum eosinophils and exhaled NO levels during the washout period. There were no significant correlations between the changes in the three markers in either group at any time. CONCLUSIONS: Treatment of asthmatic subjects with inhaled steroids for four weeks leads to improvements in airway hyperresponsiveness to histamine, eosinophil counts in induced sputum, and exhaled nitric oxide levels. The results suggest that these markers may provide different information when monitoring anti-inflammatory treatment in asthma.     

Effect of prednisone and beclomethasone dipropionate on airway responsiveness in asthma: a comparative study.

To examine the effect of corticosteroids on bronchial hyperresponsiveness, a randomised, double dummy, single blind crossover study was performed in 18 subjects with chronic asthma, comparing the effect of three weeks' treatment with inhaled beclomethasone dipropionate, 1200 micrograms daily, and oral prednisone 12.5 mg daily. The 12 week study began with a three week run in period of baseline treatment, which was continued unchanged throughout the study, and the two treatment periods were separated by a three week washout period. Patients kept daily Airflometer readings and attended the laboratory every three weeks for spirometry and a histamine inhalation test for determining the provocative dose of histamine causing a 20% fall in FEV1 (PD20). The mean FEV1 at the start was 1.9 litres (56% predicted). There was no significant change in PD20 with prednisone treatment, the mean PD20 being 0.56 and 0.59 mumol before and after treatment. There was, however, a significant improvement in PD20 with beclomethasone dipropionate treatment, the geometric mean PD20 being 0.38 and 1.01 mumol before and after treatment (p less than 0.001). There was a small but significant improvement in mean FEV1 after beclomethasone dipropionate treatment--from 1.9 to 2.2 litres--but no change after prednisone. Both medications produced significant and similar improvements in morning and evening Airflometer readings, post-bronchodilator improvement, and diurnal variation. Thus at doses that had similar beneficial effects on lung function beclomethasone dipropionate caused a significant improvement in bronchial hyperresponsiveness whereas prednisone caused no change. The superior topical anti-inflammatory effect of beclomethasone dipropionate may account for the different effects on bronchial hyperresponsiveness.     

Effect of allergen challenge on airway responsiveness to histamine and sodium metabisulphite in mild asthma.

BACKGROUND: Airway responsiveness to histamine and methacholine, direct smooth muscle spasmogens, is increased following inhalation of allergen. Although the aetiology of this phenomenon is unclear, increased cellular or neural activity may be involved since allergen also induces increases in airway responsiveness to the mast cell stimulus adenosine-5'-monophosphate (AMP) and the neural stimulus bradykinin. METHODS: To explore this further, the airway responsiveness to sodium metabisulphite (MBS), an indirect neural stimulus with similar characteristics to bradykinin, was compared in 18 mild steroid-naive asthmatic subjects with the airway responsiveness to histamine before and after allergen challenge with extracts of house dust mite, grass pollen, or cat. All subjects inhaled doubling increments of histamine and MBS until the concentration provoking a 20% fall in forced expiratory volume in one second (PC20) was reached before and three hours after allergen challenge. Twelve of the subjects had additional challenges at 24 hours after the allergen. RESULTS: Following allergen challenge all subjects showed an early response and 14 also had a late asthmatic response. For histamine there was a significant increase in airway responsiveness at both three and 24 hours compared with values before the allergen (0.89 (0.25) and 1.53 (0.52) doubling dose changes, respectively). In contrast, airway responsiveness to MBS was unaltered by allergen challenge (0.29 (0.27) and -0.33 (0.28) doubling dose changes compared with pre-allergen values at three and 24 hours, respectively). CONCLUSION: These data suggest that activation of airway sensory nerves is unlikely to contribute to the increase in airway responsiveness following inhalation of allergen. The previously observed allergen induced increase in airway responsiveness to bradykinin and AMP may involve non-neural pathways.