Multimodality measurements of small airways disease.
Explore the source record for details and available documents.
Acetates↗
Biomedical subjects
C M Salome
Publications and source records attributed to C M Salome.
Repeatability of peak nasal inspiratory flow measurements and utility for assessing the severity of rhinitis.
BACKGROUND: The measurement of peak nasal inspiratory flow (PNIF) provides a simple, cheap, fast and readily available tool for determining the extent of nasal airway patency. However, there are questions regarding its repeatability when used to assess the degree of nasal obstruction in large populations. Therefore, this study aimed to evaluate the repeatability of PNIF measurements and to assess their association with the signs and symptoms of rhinitis. METHODS: The PNIF, rhinitis symptoms, judged by Meltzer questionnaire and rhinitis signs, as determined by anterior rhinoscopy, were assessed in 283 adults representative of the general population. One training and two test PNIF measurements were recorded during the same session. RESULTS: The PNIF was highly reproducible (ICC = 0.92; 95% limits of agreement: +/-36 l/min). The PNIF was strongly correlated with rhinitis signs, measured by anterior rhinoscopy (rs= -0.38, P < 0.0001) but was not correlated with rhinitis symptoms, measured by questionnaire (rs= -0.11, P = 0.057). Differences in PNIF for subjects categorized as asymptomatic, mild or moderate/severe on the basis of rhinitis signs, were highly significant (P < 0.0001), but less significant on the basis of rhinitis symptoms (P = 0.04). A PNIF cut-off of 115 l/min had moderately high specificity (72%) and sensitivity (65%) and a high negative predictive value (90%) for moderate/severe signs of rhinitis. CONCLUSION: In a large general population-based sample of young adults, PNIF was highly reproducible and closely related to the signs of rhinitis, as determined by clinical examination. The PNIF provides information that is qualitatively different to that provided by symptom scores and may be useful to measure the extent of nasal obstruction.
Adult↗
The effects of body weight on airway calibre.
Increased wheeze and asthma diagnosis in obesity may be due to reduced lung volume with subsequent airway narrowing. Asthma (wheeze and airway hyperresponsiveness), functional residual capacity (FRC) and airway conductance (Gaw) were measured in 276 randomly selected subjects aged 28-30 yrs. Data were initially adjusted for smoking and asthma before examining relationships between weight and FRC (after adjustment for height), and between body mass index (BMI = weight.height(-2)) and Gaw (after adjustment for FRC) by multiple linear regression, separately for females and males. For males and females, BMI (+/-95% confidence interval) was 27.0+/-4.6 kg.m(-2) and 25.6+/-6.0 kg.m(-2) respectively, Gaw was 0.64+/-0.04 L.s(-1).cmH2O(-1) and 0.57+/-0.03 L.s(-1).cmH2O(-1), and FRC was 85.3+/-3.4 and 84.0+/-2.9% of predicted. Weight correlated independently with FRC in males and females. BMI correlated independently and inversely with Gaw in males, but only weakly in females. In conclusion, obesity is associated with reduced lung volume, which is linked with airway narrowing. However, in males, airway narrowing is greater than that due to reduced lung volume alone. The mechanisms causing airway narrowing and sex differences in obesity are unknown.
Adult↗
Association between nasal and bronchial symptoms in subjects with persistent allergic rhinitis.
BACKGROUND: The association between nasal and bronchial symptoms, and the course of bronchial responsiveness and airway inflammation in house dust mite sensitive persistent rhinitis over a prolonged time period has not been thoroughly explored. OBJECTIVE: To determine if nasal symptoms were associated with bronchial symptoms in persistent rhinitic subjects, and to assess their bronchial responsiveness and airway inflammation in comparison to nonrhinitic, nonatopic controls. The additional impact of pollen sensitivity on the lower airways in rhinitic subjects was also addressed. METHODS: Rhinitics and controls answered telephone symptom questionnaires once every 2 weeks for 1 year. Every 3 months, exhaled nitric oxide (eNO) and bronchial responsiveness to histamine were measured. RESULTS: Thirty-seven rhinitics and 19 controls completed the study. High nasal symptom scores in rhinitic subjects were associated with bronchial symptoms (OR = 1.7, 95% CI 1.2-2.5). Bronchial hyper-responsiveness was present in 32.4% of rhinitic subjects on at least one clinical visit during the year. Pollen allergy caused seasonal variation in eNO (P = 0.03). CONCLUSION: In persistent rhinitic subjects, high nasal symptom scores were associated with bronchial symptoms, and many subjects experienced bronchial hyper-responsiveness during the year. Persistent rhinitic subjects were more at risk than healthy adults of bronchial symptoms and airway inflammation, which are likely risk factors for asthma.
Adolescent↗
Symptoms of persistent allergic rhinitis during a full calendar year in house dust mite-sensitive subjects.
BACKGROUND: Little is known about the natural course of persistent rhinitis symptoms over a prolonged period. OBJECTIVE: To describe the frequency and severity of nasal symptoms and quality of life (QoL) in house dust mite-sensitive persistent rhinitic subjects and to determine if medication use was related to symptoms. METHODS: Rhinitics and controls were telephoned fortnightly for 1 year to monitor symptoms. QoL was measured every 3 months. RESULTS: Thirty-seven rhinitics and 19 controls completed the study. Total nasal symptom scores (TNSS) were 'high' for 65% (95% CI +/- 6%) of the year in rhinitic subjects. When TNSS increased by 1, the likelihood of nasal medication use increased by 25% (95% CI: 7-46%). General and specific QoL were worse in rhinitic subjects than controls (P < 0.04 and <0.0001). Rhinitics with pollen allergy (n = 21) had seasonal variation in the frequency of high nasal symptom scores (P = 0.02). CONCLUSION: Nasal symptom scores were consistently high in rhinitics, and their QoL was worse than controls, even in general QoL. An increase in nasal symptom score increased the likelihood of nasal medication use. These findings help to characterize the course of persistent rhinitis over a previously unstudied period of 1 year.
Animals↗
Asthma and atopy in overweight children.
BACKGROUND: Obesity may be associated with an increase in asthma and atopy in children. If so, the effect could be due to an effect of obesity on lung volume and thus airway hyperresponsiveness. METHODS: Data from 5993 caucasian children aged 7-12 years from seven epidemiological studies performed in NSW were analysed. Subjects were included if data were available for height, weight, age, skin prick test results to a common panel of aeroallergens, and a measure of airway responsiveness. History of doctor diagnosed asthma, wheeze, cough, and medication use was obtained by questionnaire. Recent asthma was defined as a doctor diagnosis of asthma ever and wheeze in the last 12 months. Body mass index (BMI) percentiles, divided into quintiles per year age, were used as a measure of standardised weight. Dose response ratio (DRR) was used as a measure of airway responsiveness. Airway hyperresponsiveness was defined as a DRR of >/=8.1. Adjusted odds ratios were obtained by logistic regression. RESULTS: After adjusting for atopy, sex, age, smoking and family history, BMI was a significant risk factor for wheeze ever (OR = 1.06, p = 0.007) and cough (OR = 1.08, p = 0.001), but not for recent asthma (OR = 1.02, p = 0.43) or airway hyperresponsiveness (OR = 0.97 p = 0.17). In girls a higher BMI was significantly associated with higher prevalence of atopy (chi(2) trend 7.9, p = 0.005), wheeze ever (chi(2) trend 10.4, p = 0.001), and cough (chi(2) trend 12.3, p<0.001). These were not significant in boys. CONCLUSIONS: Higher BMI is a risk factor for atopy, wheeze ever, and cough in girls only. Higher BMI is not a risk factor for asthma or airway hyperresponsiveness in either boys or girls.
Analysis of Variance↗
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.
Administration, Inhalation↗
Airway re-narrowing following deep inspiration in asthmatic and nonasthmatic subjects.
After bronchoconstriction, deep inspiration (DI) causes dilatation followed by airway re-narrowing. Re-narrowing may be faster in asthmatic than nonasthmatic subjects. This study investigated the relationship between re-narrowing and the magnitude of both DI-induced dilatation and the volume-dependence of respiratory system resistance (Rrs) during tidal breathing. In 25 asthmatic and 18 nonasthmatic subjects the forced oscillation technique was used to measure Rrs at baseline and after methacholine challenge, during 1 min of tidal breathing, followed by DI to total lung capacity (TLC) and passive return to functional residual capacity (FRC). Dilatation was measured as the decrease in Rrs between end tidal inspiration and TLC, re-narrowing as Rrs at FRC immediately after DI, as per cent Rrs at end-tidal expiration, and volume dependent tidal fluctuation as the difference between mean Rrs at end-expiration and end-inspiration. Asthmatic subjects had greater re-narrowing, less dilatation, and greater tidal fluctuations both at baseline and after challenge. Re-narrowing correlated with baseline tidal fluctuation and inversely with dilatation. Both baseline tidal fluctuation and dilatation were significant independent predictors of re-narrowing. Following deep inspiration-induced dilatation, faster airway re-narrowing in asthmatic than nonasthmatic subjects is associated not only with reduced deep inspiration-induced dilatation but also with some property of the airways that is detectable prior to challenge as an increased volume dependence of resistance.
Adult↗
Sahaja yoga in the management of moderate to severe asthma: a randomised controlled trial.
BACKGROUND: Sahaja Yoga is a traditional system of meditation based on yogic principles which may be used for therapeutic purposes. A study was undertaken to assess the effectiveness of this therapy as an adjunctive tool in the management of asthma in adult patients who remained symptomatic on moderate to high doses of inhaled steroids. METHODS: A parallel group, double blind, randomised controlled trial was conducted. Subjects were randomly allocated to Sahaja yoga and control intervention groups. Both the yoga and the control interventions required the subjects to attend a 2 hour session once a week for 4 months. Asthma related quality of life (AQLQ, range 0-4), Profile of Mood States (POMS), level of airway hyperresponsiveness to methacholine (AHR), and a diary card based combined asthma score (CAS, range 0-12) reflecting symptoms, bronchodilator usage, and peak expiratory flow rates were measured at the end of the treatment period and again 2 months later. RESULTS: Twenty one of 30 subjects randomised to the yoga intervention and 26 of 29 subjects randomised to the control group were available for assessment at the end of treatment. The improvement in AHR at the end of treatment was 1.5 doubling doses (95% confidence interval (CI) 0.0 to 2.9, p=0.047) greater in the yoga intervention group than in the control group. Differences in AQLQ score (0.41, 95% CI -0.04 to 0.86) and CAS (0.9, 95% CI -0.9 to 2.7) were not significant (p>0.05). The AQLQ mood subscale did improve more in the yoga group than in the control group (difference 0.63, 95% CI 0.06 to 1.20), as did the summary POMS score (difference 18.4, 95% CI 0.2 to 36.5, p=0.05). There were no significant differences between the two groups at the 2 month follow up assessment. CONCLUSIONS: This randomised controlled trial has shown that the practice of Sahaja yoga does have limited beneficial effects on some objective and subjective measures of the impact of asthma. Further work is required to understand the mechanism underlying the observed effects and to establish whether elements of this intervention may be clinically valuable in patients with severe asthma.
Adolescent↗
Exhaled nitric oxide levels in atopic children: relation to specific allergic sensitisation, AHR, and respiratory symptoms.
BACKGROUND: Exhaled nitric oxide (eNO), which has been proposed as a measure of airway inflammation, is increased in atopic subjects. This raises the question of whether eNO provides any additional information about airway inflammation in asthmatic subjects, other than as a marker for atopy. A study was undertaken to determine whether eNO levels in a population of atopic children are associated with sensitisation or natural exposure to specific allergens, and to examine the relationship between eNO, airway responsiveness, and current respiratory symptoms. METHODS: Exhaled NO and airway responsiveness to histamine were measured in winter and in summer in 235 children aged 8-14 years who had been classified as atopic by skin prick testing. Current respiratory symptoms, defined as wheeze or cough during the month preceding the test, were measured by a parent completed questionnaire. Airway hyperresponsiveness (AHR) was defined as a dose response ratio (DRR) of >8.1 (% fall in forced expiratory volume in 1 second (FEV(1))/micromol + 3). RESULTS: Sensitisation to house dust mite was associated with raised eNO levels in winter while sensitisation to Cladosporium was associated with raised eNO levels in both winter and summer. Grass pollen sensitisation was not associated with raised eNO levels in either season. Exhaled NO correlated significantly with DRR histamine (r=0.43, p<0.001) independently of whether the children had current symptoms or not. In children with current wheeze, those with AHR had eNO levels 1.53 (95% CI 1.41 to 1.66) times higher than those without AHR (p=0.006). Neither DRR (p=1.0) nor eNO levels (p=0.92) differed significantly between children with or without persistent dry cough in the absence of wheeze. CONCLUSIONS: In atopic children, raised eNO levels are associated with sensitisation to perennial allergens, but not to seasonal allergens such as grass pollen. In this population, an increase in eNO is associated with AHR and current wheezing, suggesting that eNO is more than just a marker for atopy.
Adolescent↗
Inhaled corticosteroid dosage in asthma.
Explore the source record for details and available documents.
Administration, Topical↗
Eosinophilia, interleukin-5, and tumour necrosis factor-alpha in asthmatic children.
BACKGROUND: There are few paediatric studies of the interrelationships between inflammatory markers and asthma severity. We therefore assessed the relationships between eosinophil-associated markers, cytokines, and asthma severity in asthmatic children aged 8-12 years. METHODS: Forty-five children were tested twice, 2 weeks apart. Asthma severity was measured in terms of symptoms, lung function, medication needs, and histamine responsiveness. Peripheral inflammatory markers measured included eosinophil numbers, serum ECP, IL-5, and TNF-alpha and mononuclear cell IL-5, and TNF-alpha production. RESULTS: Histamine responsiveness was correlated with circulating eosinophils (r = 0.56, P = 0.0001) and serum ECP (r = 0.54, P = 0.003). Eosinophilia was increased in children with severe as opposed to mild airway hyperresponsiveness (P = 0.02) and those who lost days at school as opposed to those who did not (P = 0.01). There were no other associations between markers of asthma severity and inflammation. Children taking inhaled corticosteroids had lower serum IL-5 levels than those on beta-agonists +/- cromolyn (mean and 95% CI: 20.5 [11.7-35.7] pg/ml vs 64.3 [26.6-155.4] pg/ml; P = 0.04). Cellular IL-5 production correlated with serum TNF-alpha (r = 0.63, P = 0.0062) and IL-5 (r = -0.59, P = 0.005). CONCLUSION: Serum levels of TNF-alpha and IL-5 were not related to peripheral eosinophilia and asthma severity in these children but were related to their own cellular production ex vivo. This study confirms that eosinophilia is the index of inflammation that is most closely related to the clinical severity of childhood asthma.
Absenteeism↗
Obesity is a risk for asthma and wheeze but not airway hyperresponsiveness.
BACKGROUND: A study was undertaken to assess whether the recent increases in prevalence of both asthma and obesity are linked and to determine if obesity is a risk factor for diagnosed asthma, symptoms, use of asthma medication, or airway hyperresponsiveness. METHODS: Data from 1971 white adults aged 17-73 years from three large epidemiological studies performed in NSW were pooled. Doctor diagnosis of asthma ever, history of wheeze, and medication use in the previous 12 months were obtained by questionnaire. Body mass index (BMI) in kg/m(2) was used as a measure of obesity. Airway hyperresponsiveness (AHR) was defined as dose of <3.9 micromol histamine required to provoke a fall in forced expiratory volume in one second (FEV(1)) of 20% or more (PD(20)FEV(1)). Adjusted odds ratios (OR) were obtained by logistic regression. RESULTS: After adjusting for atopy, age, sex, smoking history, and family history, severe obesity was a significant risk factor for recent asthma (OR 2. 04, p=0.048), wheeze in the previous 12 months (OR 2.6, p=0.001), and medication use in the previous 12 months (OR 2.83, p=0.005), but not for AHR (OR 0.87, p=0.78). FEV(1) and forced vital capacity (FVC) were significantly reduced in the group with severe obesity, but FEV(1)/FVC ratio, peak expiratory flow (PEF), and mid forced expiratory flow (FEF(25-75)) were not different from the group with normal BMI. The underweight group (BMI <18.5 kg/m(2)) had increased symptoms of shortness of breath, increased airway responsiveness, and reduced FEV(1), FVC, PEF, and FEF(25-75) with similar use of asthma medication as subjects in the normal weight range. CONCLUSIONS: Although subjects with severe obesity reported more wheeze and shortness of breath which may suggest a diagnosis of asthma, their levels of atopy, airway hyperresponsiveness, and airway obstruction did not support the suggestion of a higher prevalence of asthma in this group. The underweight group appears to have more significant respiratory problems with a higher prevalence of symptoms, reduced lung function, and increased airway responsiveness without an increase in medication usage. This group needs further investigation.
Adolescent↗
Predictive markers of asthma exacerbation during stepwise dose reduction of inhaled corticosteroids.
To determine predictors for failed reduction of inhaled corticosteroids (ICS), in 50 subjects with well-controlled asthma (age 43.7 [18-69]; 22 males) taking a median dose of 1,000 microg ICS/d (100-3,600 microg/d), ICS were halved every 8 wk. Airway hyperresponsiveness (AHR) to a bronchial provocation test (BPT) with histamine was measured at baseline. AHR to BPT with mannitol, spirometry, exhaled nitric oxide (eNO), and, in 31 subjects, sputum inflammatory cells were measured at baseline and at monthly intervals. Thirty-nine subjects suffered an asthma exacerbation. Seven subjects were successfully weaned off ICS. Using a Kaplan- Meier survival analysis, the significant predictors of a failure of ICS reduction were being hyperresponsive to both histamine and mannitol at baseline (p = 0.039), and being hyperresponsive to mannitol during the dose-reduction phase of the study (p = 0.02). Subjects older than 40 yr of age tended to be at greater risk of ICS reduction failure (p = 0.059). Response to mannitol and percentage sputum eosinophils were significantly greater before a failed ICS reduction than before the last successful ICS reduction, whereas there were no significant differences in symptoms, spirometry, or eNO. These findings suggest that documentation of patient's AHR or sputum eosinophils may be useful in guiding the reduction of ICS doses.
Adolescent↗
Markers of airway inflammation and airway hyperresponsiveness in patients with well-controlled asthma.
In steroid-naive asthmatics, airway hyperresponsiveness correlates with noninvasive markers of airway inflammation. Whether this is also true in steroid-treated asthmatics, is unknown. In 31 stable asthmatics (mean age 45.4 yrs, range 22-69; 17 females) taking a median dose of 1,000 microg inhaled corticosteroids (ICS) per day (range 100-3,600 microg x day(-1)), airway responsiveness to the "direct" agent histamine and to the "indirect" agent mannitol, lung function (forced expiratory volume in one second (FEV1), forced vital capacity (FVC), peak expiratory flow (PEF)), exhaled nitric oxide (eNO), and number of inflammatory cells in induced sputum as a percentage of total cell count were measured. Of the 31 subjects, 16 were hyperresponsive to mannitol and 11 to histamine. The dose-response ratio (DRR: % fall in FEV1/cumulative dose) to both challenge tests was correlated (r=0.59, p=0.0004). However, DRR for histamine and DRR for mannitol were not related to basic lung function, eNO, per cent sputum eosinophils and ICS dose. In addition, NO was not related to basic lung function and per cent sputum eosinophils. In clinically well-controlled asthmatics taking inhaled corticosteroids, there is no relationship between markers of airway inflammation (such as exhaled nitric oxide and sputum eosinophils) and airway responsiveness to either direct (histamine) or indirect (mannitol) challenge. Airway hyperresponsiveness in clinically well-controlled asthmatics appears to be independent of eosinophilic airway inflammation.
Adult↗
The effect of insecticide aerosols on lung function, airway responsiveness and symptoms in asthmatic subjects.
The object of this study was to compare the effect of standard and "low irritant" insecticide aerosols on lung function, airway hyperresponsiveness (AHR) and symptoms in asthmatic subjects. A double blind randomized, crossover study was conducted in 25 asthmatic subjects who reported sensitivity to insecticide aerosols. All subjects were exposed for 30 min, on separate occasions, to two standard insecticide formulations (A and B), one low irritant formulation (C) and a negative control aerosol. Spirometric function and chest, nose and eye symptoms were recorded during, and for 90 min after, the exposure. AHR to methacholine was measured 90 min after the exposure. Compared to the negative control, the maximum fall in forced expiratory volume in one second (FEV1) was slightly greater after standard insecticides (mean differences from control +/-95% confidence interval: aerosol A, 3.3+/-3.6%, p=0.08; aerosol B, 5.1+/-4.7%, p=0.04), AHR was significantly more severe (mean difference from control: aerosol A, 0.35+/-0.29 doubling doses, p=0.028; aerosol B, 0.52+/-0.43 doubling doses, p=0.028), and symptoms were more severe. The low irritant test aerosol (C) did not differ significantly from the negative control with respect to FEV1, AHR or symptoms. It is concluded that some insecticide aerosols trigger symptoms and falls in lung function in some people with asthma. Furthermore, these aerosols may also increase airway hyperresponsiveness, although the mechanism of this effect has not been determined. The low irritant formulation did not appear to have the same effects.
Adult↗
Optimal asthma control, starting with high doses of inhaled budesonide.
The aim of this study was to determine whether outcomes in poorly controlled asthma can be further improved with a starting dose of inhaled budesonide higher than that recommended in international guidelines. The study had a parallel-group design and included 61 subjects with poorly controlled asthma, randomized to receive 3,200 microg or 1,600 microg budesonide daily by Turbuhaler for 8 weeks (double-blind), then 1,600 microg x day(-1) for 8 weeks (single-blind), followed by 14 months of open-label budesonide dose down-titration using a novel algorithm, with a written asthma crisis plan based on electronic peak expiratory flow monitoring. The primary outcome variable for weeks 1-16 was change in airway hyperresponsiveness (AHR), and, for the open-label phase, mean daily budesonide dose. By week 16, there were large changes from baseline in all outcomes, with no significant differences between the 3,200- and 1,600-microg x day(-1) starting dose groups (AHR increased by 3.2 versus 3.0 doubling doses, p=0.7; morning peak flow increased by 134 versus 127 L x min(-1), p=0.8). Subjects starting with 3,200 microg x day(-1) were 3.8 times more likely to achieve AHR within the normal range, as defined by a provocative dose of histamine causing a 20% fall in forced expiratory volume in one second (PD20) of > or = 3.92 micromol by week 16 (p=0.03) [corrected]. During dose titration, there was no significant difference in mean budesonide dose (1,327 versus 1,325 microg x day(-1), p>0.3). Optimal asthma control was achieved in the majority of subjects (at completion/withdrawal: median symptoms 0.0 days x week(-1), beta2-agonist use 0.2 occasions x day(-1), and PD20 2.4 micromol). In subjects with poorly controlled asthma, a starting dose of 1,600 microg x day(-1) budesonide was sufficient to lead to optimal control in most subjects. The high degree of control achieved, compared with previous studies, warrants further investigation.
Administration, Inhalation↗
Perception of bronchodilation in subjects with asthma and smokers with airflow limitation.
Perception of the efficacy of bronchodilators in relieving airflow obstruction is a likely determinant of compliance with treatment in patients prescribed these drugs on an 'as needed' basis. This study aimed to determine whether bronchodilator-induced improvements in lung function are associated with improvements in breathing difficulty in subjects with asthma or smokers with airflow limitation. Twenty smokers with airflow limitation and 16 subjects with previously physician-diagnosed asthma received salbutamol (200 micrograms) and ipratropium bromide (80 micrograms). Spirometry and lung volumes were measured before and 40 min after bronchodilator. Subjects recorded changes in 'difficult breathing' on a visual analogue scale (VAS). After bronchodilator, forced expiratory volume in 1 s (FEV1) increased by 23.0 +/- 6.4% of baseline (mean +/- 95% CI) in smokers, and by 25.2 +/- 8.5% in the asthmatics, while VAS improved by 31 +/- 23% in smokers and 45 +/- 25% in asthmatics. However, these changes were not significantly correlated in either smokers (r = -0.04) or asthmatics (r = 0.15). In the asthmatic subjects, good perceivers (> 25% improvement in VAS) had greater improvements in lung volumes, as percentage predicted, than did poor perceivers. In the smokers, changes in lung function did not differ significantly between good and poor perceivers. Improvement in FEV1, as percentage predicted, was significantly correlated with improvement in VAS in good perceivers (asthma: r = 0.78, P < 0.01; smokers: r = 0.68, P < 0.05), but not in poor perceivers. Asthmatic subjects had good perception of improvements in lung function. However, in smokers with airflow limitation there is little correlation between improvement in lung function and sensation of breathing difficulty. In these subjects symptoms appear to be an unreliable guide for 'as needed' use of bronchodilators.
Aged↗