Bronchodilator responsiveness testing using raised volume forced expiration in recurrently wheezing infants

Bronchodilator response in wheezing infants assessed by the raised volume rapid thoracic compression technique

BACKGROUND

Bronchodilator response (BDR) analyzed by the raised volume rapid thoracic compression (RVRTC) in wheezing infants is not yet well described, although bronchodilators (BD) are routine in the treatment of this population.

OBJECTIVE

To evaluate BDR by RVRTC technique in infants with recurrent wheezing and compare to control group.

METHOD

Cross sectional study, 45 infants, age 56 weeks (38-67 weeks). Two groups: wheezing group (WG: history of recurrent wheezing) and control group (CG). RVRTC was evaluated, FVC, FEV_0.5, FEF₅₀, FEF₇₅, FEF_85, FEF_25-75 were measured. Salbutamol was delivered to infants and RVRTC evaluated again. BDR was determined by the increase greater than two standard deviation from the mean change in the CG.

RESULTS

In WG (n = 32) lung function was worse than in CG (n = 13): FEV_0.5: 0.0(-0.9-0.9z score) vs 0.8(0.2-1.4z score); FEF₅₀: 0.2(-0.3-1.1z score) vs 0.9(0.5-1.4z score); and FEF_25-75: 0.2(-0.5-1.1z score) vs 1.1(0.6-1.6z score), respectively, p < 0.05. Both groups had similar increase after BD. In WG 11 patients (34%) were responder and these had worse lung function compared to nonresponder (n = 21) (p < 0.05). The increase in lung function after BD in responder was higher than in nonresponder: FEV_0.5: 6.5(2.1-7.1%) vs -0.5(-2.5-0.7%), FEF₅₀: 5.1(2.7-11.7%) vs 0.4(-1.1-2.8%), FEF₇₅: 20.7(4.7-23.6%) vs -1.3(-6.4-3.9%), FEF_25-75: 9.9(3.8-16.4%) vs 0.0(-1.5-1.0%), respectively, p < 0.05.

CONCLUSION

34% WG showed BDR measured by the RVRTC. The best variables to detect BDR were FEF₇₅, FEF_25-75 and FEV_0.5. Patients with worse lung function showed better response to BD.

Bronchodilator responsiveness in wheezy infants predicts continued early childhood respiratory morbidity

OBJECTIVE

Spirometry including bronchodilator responsiveness is considered routine in the workup of asthma in older children. However, in wheezy infants the existence of bronchodilator responsiveness and its prognostic significance remain unclear.

METHODS

Infants (< 2 years) with chronic or recurrent wheezing or coughing were evaluated by infant pulmonary function testing (PFT). Maximal expiratory flow at the point of functional residual capacity (V̇maxFRC) was measured before and 20 minutes after salbutamol administration. Only infants with an obstructive profile (V̇maxFRC < 80% predicted) were included. The infants were divided into two groups with regard to whether or not a response to salbutamol was observed on PFT. A response was defined as a mean V̇maxFRC after salbutamol administration exceeding the upper confidence interval limit of individual pre-bronchodilator V̇maxFRC measurements. Follow-up data was gathered after a mean of 2 years.

MEASUREMENTS AND MAIN RESULTS

Sixty infants were included in the study of which 32 (53%) demonstrated responsiveness to bronchodilators. The infants in the responsive group had a significantly higher frequency of physician visits for wheezing than the non-responders (3.0 mean visits/yr vs. 1.5 respectively, P = 0.03), and had a higher likelihood of having received asthma medication in the last year of the follow-up period (84% vs. 50% respectively, RR: 1.68[1.10-2.56]). At the end of the follow-up period, more parents in the responsive group reported continued respiratory disease (71% vs. 22%, RR:3.21[1.30-7.95]).

CONCLUSIONS

Bronchodilator responsiveness can be demonstrated by infant PFT in infants with recurrent wheezing and can predict increased respiratory morbidity until 3 years of age.

Pharmacological approach to wheezing in preschool children

INTRODUCTION

Wheezing disorders are very common during childhood (particularly among preschool children), and represent a significant burden for patients, their families, the healthcare system, and society as a whole. Identifying wheezing phenotypes, and recognizing the risk factors associated with each, may help to predict long-term outcomes, distinguish high-risk children who may benefit from secondary prevention measures, and ensure that the most effective therapy is prescribed for each case.

AREAS COVERED

The main aim of this review is to analyze the characteristics of the drugs currently used to treat wheezing in preschool children, and discuss the results obtained in children with different wheezing phenotypes.

EXPERT OPINION

The continuous or intermittent administration of various oral or inhaled drugs could theoretically be effective in preventing or controlling wheezing in preschool children. However, the optimal management of acute preschool wheezing episodes has not yet been determined mainly because of their phenotypical heterogeneity.

An official American Thoracic Society workshop report: optimal lung function tests for monitoring cystic fibrosis, bronchopulmonary dysplasia, and recurrent wheezing in children less than 6 years of age

Although pulmonary function testing plays a key role in the diagnosis and management of chronic pulmonary conditions in children under 6 years of age, objective physiologic assessment is limited in the clinical care of infants and children less than 6 years old, due to the challenges of measuring lung function in this age range. Ongoing research in lung function testing in infants, toddlers, and preschoolers has resulted in techniques that show promise as safe, feasible, and potentially clinically useful tests. Official American Thoracic Society workshops were convened in 2009 and 2010 to review six lung function tests based on a comprehensive review of the literature (infant raised-volume rapid thoracic compression and plethysmography, preschool spirometry, specific airway resistance, forced oscillation, the interrupter technique, and multiple-breath washout). In these proceedings, the current state of the art for each of these tests is reviewed as it applies to the clinical management of infants and children under 6 years of age with cystic fibrosis, bronchopulmonary dysplasia, and recurrent wheeze, using a standardized format that allows easy comparison between the measures. Although insufficient evidence exists to recommend incorporation of these tests into the routine diagnostic evaluation and clinical monitoring of infants and young children with cystic fibrosis, bronchopulmonary dysplasia, or recurrent wheeze, they may be valuable tools with which to address specific concerns, such as ongoing symptoms or monitoring response to treatment, and as outcome measures in clinical research studies.

Nasal versus oronasal raised volume forced expirations in infants--a real physiologic challenge

Raised volume rapid thoracoabdominal compression (RTC) generates forced expiration (FE) in infants typically from an airway opening pressure of 30 cm H(2)O (V(30)). We hypothesized that the higher nasal than pulmonary airway resistance limits forced expiratory flows (FEF(%)) during (nasal) FE(n), which an opened mouth, (oronasal) FE(o), would resolve. Measurements were performed during a brief post-hyperventilation apnea on 12 healthy infants aged 6.9-104 weeks. In two infants, forced expiratory (FEFV) flow volume (FV) curves were generated using a facemask that covered the nose and a closed mouth, then again with a larger mask with the mouth opened. In other infants (n = 10), the mouth closed spontaneously during FE. Oronasal passive expiration from V(30) generated either the inspiratory capacity (IC) or by activating RTC before end-expiration, the slow vital capacity ((j) SVC). Peak flow (PF), FEF(25), FEF(50), FEF(25-75), FEV(0.4), and FEV(0.5) were lower via FE(n) than FE(o) (P < 0.05), but the ratio of expired volume at PF and forced vital capacity (FVC) as percent was higher (P < 0.05). FEF(75), FEF(85), FEF(90), FVC as well as the applied jacket pressures were not different (P > 0.05). FEFV curves generated via FE(o) exhibited higher PF than FV curves of IC (P < 0.05); PF of those produced via FE(n) were not different from FV curves of IC (P > 0.05) but lower than those of (j) SVC (P < 0.05). In conclusion, the higher nasal than pulmonary airways resistance unequivocally affects the FEFV curves by consistently reducing PF and decreases mid-expiratory flows. A monitored slightly opened mouth and a gentle anterior jaw thrust are physiologically integral for raised volume RTC in order to maximize the oral and minimize nasal airways contribution to FE so that flow limitation would be in the pulmonary not nasal airways.

Bronchodilator responsiveness in wheezy infants and toddlers is not associated with asthma risk factors

BACKGROUND

There are limited data assessing bronchodilator responsiveness (BDR) in infants and toddlers with recurrent wheezing, and factors associated with a positive response.

OBJECTIVES

In a multicenter study of children ≤ 36 months old, we assessed the prevalence of and factors associated with BDR among infants/toddlers with recurrent episodes of wheezing.

METHODS

Forced expiratory flows and volumes using the raised-volume rapid thoracic compression method were measured in 76 infants/toddlers [mean (SD) age 16.8 (7.6) months] with recurrent wheezing before and after administration of albuterol. Prior history of hospitalization or emergency department treatment for wheezing, use of inhaled or systemic corticosteroids, physician treatment of eczema, environmental tobacco smoke exposure, and family history of asthma or allergic rhinitis were ascertained.

RESULTS

Using the published upper limit of normal for post bronchodilator change (FEV(0.5)  ≥ 13% and/or FEF(25-75)  ≥ 24%) in healthy infants, 24% (n = 18) of children in our study exhibited BDR. The BDR response was not associated with any clinical factor other than body size. Dichotomizing subjects into responders (defined by published limits of normal) or by quartile to identify children with the greatest change from baseline (4th quartile vs. other) did not identify any other factor associated with BDR.

CONCLUSIONS

Approximately one quarter of infants/toddlers with recurrent wheezing exhibited BDR at their clinical baseline. However, BDR in wheezy infants/toddlers was not associated with established clinical asthma risk factors.

[Recurrent wheezing in three year-olds: facts and opportunities]

The 3 year-old group of children has an increased incidence and prevalence of recurrent wheezing episodes. There are different subgroups, who give different inflammatory responses to different triggering agents, and subgroups that differ in aetiopathology and immunopathology. Current diagnostic methods (exhaled nitric oxide in multiple breaths, nitric oxide in exhaled air condensate, induced sputum, broncho-alveolar lavage and endo-bronchial biopsy), enable the inflammatory pattern to be identified and to give the most effective and safe treatment. The various therapeutic options for treatment are reviewed, such as inhaled glucocorticoids when the inflammatory phenotype is eosinophilic, and leukotriene receptor antagonists, when the inflammatory phenotype is predominantly neutrophilic. In accordance with the current recommendations, for the diagnosis as well as for the therapy initiated in children of this age, they must be regularly reviewed, so that if the benefit is not clear, the treatment must be stopped and an alternative diagnosis and treatment considered. The start of treatment should be determined depending on the intensity and frequency of the symptoms, with the aim of decreasing morbidity and increasing the quality of life of the patient.

Beta2-agonists for asthma: the pediatric perspective

Inhaled beta-agonists are commonly prescribed for the treatment of wheezing disorders in infants and children. Despite this, there are concerns that these medications have potentially detrimental effects on lung health and symptoms. We will review the ontogeny of beta-agonist receptor and smooth muscle development from fetal life through infancy and childhood as well as the evidence supporting the clinical utility of beta-agonists in wheezing infants and asthmatic children. Finally, the potential detrimental effects of long- and short-acting beta-agonists in infants and children are discussed.

Physiologic, bronchoscopic, and bronchoalveolar lavage fluid findings in young children with recurrent wheeze and cough

Assessing airway disease in young children with wheeze and/or cough is challenging. We conducted a prospective, descriptive study of lung function in children <3 years old with recurrent wheeze and/or cough, who had failed empiric antiasthma and/or antireflux therapy and subsequently underwent flexible bronchoscopy. Our goals were to describe radiographic, anatomical, microbiological, and physiological findings in these children, and generate hypotheses about their respiratory physiology. Plethysmography and raised-volume rapid thoracoabdominal compression (RVRTC) techniques were performed prior to bronchoscopy. Mean Z-scores (n = 19) were -1.34 for forced expiratory volume at 0.5 sec (FEV(0.5)), -2.28 for forced expiratory flows at 75% of forced vital capacity (FVC) (FEF(75)), -2.25 for forced expiratory flows between 25-75% of FVC (FEF(25-75)), 2.53 for functional residual capacity (FRC), and 2.23 for residual volume divided by total lung capacity (RV/TLC). Younger, shorter children had markedly depressed FEF(75) and FEF(25-75) Z-scores (P = 0.002 and P = <0.001, respectively). As expected, lower airway anatomical abnormalities, infection, and inflammation were common. Elevated FRC was associated with anatomical lower airway abnormalities (P = 0.03). FVC was higher in subjects with neutrophilic inflammation (P = 0.03). There was no association between other physiologic variables and bronchoscopic/bronchoalveolar lavage fluid findings. Half of those with elevated RV/TLC ratios (Z-score >2) had no evidence of chest radiograph hyperinflation. We conclude that in this population, plethysmography and RVRTC techniques are useful in identifying severity of hyperinflation and airflow obstruction, and we hypothesize that younger children may have relatively small airways caliber, significantly limiting airflow, and thus impairing secretion clearance and predisposing to lower airway infection.

Asthma therapy for children under 5 years of age

PURPOSE OF REVIEW

The evidence for effectiveness of currently used asthma medication for wheeze in young children is reviewed.

RECENT FINDINGS

The management of the infant and preschool child with wheezing is complicated by the uncertainty with respect to the aetiology. Difficulties in defining phenotypes and objective outcome parameters combined with the transient nature of symptoms which often resolve spontaneously have confounded many therapeutic studies. Recent studies on the effect of pharmacotherapy in wheezing infants have tried to define a more homogeneous phenotype as well as make a selection of patients that are likely to respond to the studied drug. In addition, these studies have used lung function parameters and nitric oxide as one of the outcome measurements. Studies on the nature of inflammation and the development of airway remodelling in infants and young children are done to further define phenotypes.

SUMMARY

Currently, there are no evidence-based guidelines and not even consensus statements on the right approach in pharmacological treatment of wheezing in infants and preschool children. The main issue still is the difficulty in coming to a correct diagnosis. Further studies are needed on the nature and the diagnostics of phenotypes and on the effect of early intervention.

Lung function tests in neonates and infants with chronic lung disease: forced expiratory maneuvers

This fourth paper in a review series on the role of lung function testing in infants and young children with acute neonatal disorders and chronic lung disease of infancy (CLDI) addresses measurements of forced expiration using rapid thoraco-abdominal compression (RTC) techniques and the forced deflation technique. Following orientation of the reader to the subject area, we focus our comments on the areas of inquiry proposed in the introductory paper to this series. The quality of the published literature is reviewed critically, and recommendations are provided to guide future investigation in this field. All studies on infants and young children with CLDI using forced expiratory or deflation maneuvers demonstrated that forced flows at low lung volume remain persistently low through the first 3 years of life. Measurement of maximal flow at functional residual capacity (V'maxFRC) is the most commonly used method for assessing airway function in infants, but is highly dependent on lung volume and airway tone. Recent studies suggested that the raised volume RTC technique, which assesses lung function over an extended volume range as in older children, may be a more sensitive means of discriminating changes in airway function in infants with respiratory disease. The forced deflation technique allows investigation of pulmonary function during the early development of CLDI in intubated subjects, but its invasive nature precludes its use in the routine setting. For all techniques, there is an urgent need to establish suitable reference data and evaluate within- and between-occasion repeatability, prior to establishing the clinical usefulness of these techniques in assessing baseline airway function and/or response to interventions in subjects with CLDI.

The response to β-agonists in wheezy infants: three methods compared

BACKGROUND

Studies into the effects of salbutamol in the treatment of wheeze in infancy have been conflicting, possibly due to differences in outcome variables. We aimed to assess the response to salbutamol using indices derived from passive and forced expiration.

METHODS

We recruited 39 infants who had a history of wheezing (mean age 43 weeks) and measured maximum flow at functional residual capacity (V'(max FRC)) by rapid thoracoabdominal compression (RTC), and forced expired volume at 0.4s (FEV0.4) using the raised-volume RTC technique (RV-RTC). We calculated passive compliance (C(rs)), resistance (R(rs)) and time constant (tau) from relaxed expirations that followed the augmented inspirations delivered during RV-RTC. Measurements were repeated after aerosol salbutamol (800 mcg).

RESULTS

Data were obtained in 32 infants for V'(max FRC), 22 for FEV0.4 and 19 for passive mechanics. There were no mean changes in any index of forced expiration after salbutamol. Some individuals showed significant changes (improvement or worsening) in one or other index. Overall, there was a small increase in C(rs) after salbutamol but no change in R(rs) or tau.

CONCLUSIONS

We found no consistent pattern of response in either index of forced expiration. Validated clinical scores or alternative physiological techniques may be preferable to respiratory mechanics in assessing bronchodilator response.

Is bronchodilator response in 2-yr-old children associated with asthma risk factors?

Factors that might influence lung function bronchodilator response by 2 yr of age is largely unknown, thus we aimed to assess this in the 'Environment and Childhood asthma' (ECA) study in Oslo. A clinical investigation at mean age 26 months was attended by 516 (84%) children included in a nested case-control study [children with recurrent bronchial obstruction (rBO)] (n = 265) and controls without a history of lower respiratory disease (n = 251). Tidal lung function measures before and after inhaled nebulized salbutamol (bronchodilator response) (when clinically without BO) were obtained in 46%. Clinical characteristics and personal and family history of allergic/respiratory diseases (asthma risk factors) were ascertained by structured interview and clinical examination. Allergic sensitization was assessed by skin prick test/specific IgE antibody analyses to common allergens. Mean (95% CI) per cent change in time to reach peak flow/total expiratory time (t(PTEF)/t(E)) from before to after salbutamol was significantly larger in children with rBO [17.3 (9.4-25.3) than controls (-2.2 (-7.7 to 3.0)]. The bronchodilator response increased significantly (p = 0.001) with increasing number of asthma risk factors, but was not significantly associated with allergic sensitization, parental 'atopy', or maternal smoking alone. Children treated with inhaled corticosteroids had greater bronchodilator response than those treated with bronchodilators alone. Bronchodilator response in asymptomatic 2-yr-old children was most closely associated with the presence of rBO, but increasing number of asthma risk factors and treatment with inhaled corticosteroids were associated with increased bronchodilator response.

Sensitivity of spirometric measurements to detect airway obstruction in infants

We evaluated the ability of forced expiratory flow volume curves from raised lung volumes to assess airway function among infants with differing severities of respiratory symptoms. Group 1 (n = 33) had previous respiratory symptoms but were currently asymptomatic; group 2 (n = 36) was symptomatic at the time of evaluation. As a control group, we used our previously published sample of 155 healthy infants. Flow volume curves were quantified by FVC, FEF50, FEF75, FEF25-75, FEV0.5, and FEV0.5/FVC, which were expressed as Z scores. All variables except FVC had Z scores that were significantly less than zero and distinguished groups 1 and 2 with progressively lower Z scores. The mean Z scores of the flow variables (FEF50%, FEF75%, and FEF25-75%) were more negative than the Z scores for the timed expired volumes (FEV0.5 or FEV0.5/FVC) for both groups. In general, measures of flow identified a greater number of infants with abnormal lung function than measures of timed volume; FEF50 had the highest performance in detecting abnormal lung function. In summary, forced expiratory maneuvers obtained by the raised volume rapid compression technique can discriminate among groups of infants with differing severity of respiratory symptoms, and measures of forced expiratory flows were better than timed expiratory volume in detecting abnormal airway function.

Bronchodilation in infants with malacia or recurrent wheeze

BACKGROUND

Controversy remains regarding the effectiveness of bronchodilators in wheezy infants.

AIMS

To assess the effect of inhaled beta(2) agonists on lung function in infants with malacia or recurrent wheeze, and to determine whether a negative effect of beta(2) agonists on forced expiratory flow (V'(maxFRC)) is more pronounced in infants with airway malacia, compared to infants with wheeze.

METHODS

We retrospectively analysed lung function data of 27 infants: eight with malacia, 19 with recurrent wheeze. Mean (SD) age was 51 (18) weeks. Mean V'(maxFRC) (in Z score) was assessed before and after inhalation of beta(2) agonists.

RESULTS

Baseline V'(maxFRC) was below reference values for both groups. Following inhalation of beta(2) agonists the mean (95% CI) change in mean V'(maxFRC) in Z scores was -0.10 (-0.26 to 0.05) and -0.33 (-0.55 to -0.11) for the malacia and wheeze group, respectively.

CONCLUSIONS

In infants with wheeze, inhaled beta(2) agonists caused a significant reduction in mean V'(maxFRC). Infants with malacia were not more likely to worsen after beta(2) agonists than were infants with recurrent wheeze.

Exploring the relationship between forced maximal flow at functional residual capacity and parameters of forced expiration from raised lung volume in healthy infants

The raised volume rapid thoraco-abdominal compression technique (RVRTC) is being increasingly used to assess airway function in infants, but as yet no consensus exists regarding the equipment, methods, or analysis of recorded data. The aim of this study was to explore the relationship between maximal flow at functional residual capacity (V'(maxFRC)) and parameters derived from raised lung volumes, and to address analytical aspects of the latter technique in an attempt to assist with future standardization initiatives. Forced vital capacity (FVC) from lung volume raised to 3 kPa, timed forced expiratory volumes (FEV(t)), and forced expiratory flow parameters at different percentages of expired FVC (FEF(%)) were measured in 98 healthy infants (1-69 weeks of age). V'(maxFRC) using the tidal rapid thoraco-abdominal compression (RTC) technique was also measured. The within-subject relationships and within-subject variability of the various parameters were assessed. Duration of forced expiration was < 0.5 sec in 5 infants, meaning that FEV(0.3) and FEV(0.4) were the only timed volume parameters that could be calculated in all infants during the first months of life, and even when it could be calculated, FEV(0.5) approached FVC in many of these infants. It is recommended that FEV(0.4) be routinely reported in infants less than 3 months of age. Contrary to previous reports, within subject variability of V'(maxFRC) was less than that of FEF(75) (mean CV = 6.3% and 8.9%, respectively).A more standardized protocol when analyzing data from the RVRTC would facilitate comparisons of results between centers in the future.

Effect of airway inflation pressure on forced expiratory maneuvers from raised lung volume in infants

The raised lung volume technique is increasingly used to measure forced expiratory maneuvers in infants. However, there is no consensus regarding the optimal airway inflation pressure (P(inf)) required for such maneuvers, or the influence of small changes in P(inf) within and between infants. The aim of this study was to assess the effect of small differences (0.2-0.3 kPa) in P(inf) on forced vital capacity (FVC), forced expired volume in 0.5 sec (FEV(0.5)), and forced expired flow at 75% of vital capacity (FEF(75)), all derived from the raised volume rapid thoraco-abdominal compression (RVRTC) technique. Randomized paired forced expiratory maneuvers were obtained in 32 healthy infants ( 3.9-39.3 weeks old, 3.8-9.9 kg) with the safety pressure relief valve for P(inf) set to 2.7 kPa or 3.0 kPa (27 or 30 cm H(2)0). When mean (SD) P(inf) was increased by 8.4 (2.8)%, there was a significant (P < 0.01) increase in mean (SD) FVC, FEV(0.5), and FEF(75) by 5.8 (5.7)%, 6.1 (6)%, and 8.3 (16.2)%, respectively. In conclusion, relatively small differences in P(inf) will result in significant differences in FVC, FEV(0.5), and FEF(75) by RVRTC technique. Precision in setting and reporting the applied P(inf) is therefore essential, particularly if data are to be compared between centers.

Short acting beta agonists for recurrent wheeze in children under 2 years of age

BACKGROUND

Wheeze is a common symptom in infancy and is a common cause for both primary care consultations and hospital admission. Beta2-adrenoceptor agonists (b2-agonists) are the most frequently used as bronchodilator but their efficacy is questionable.

OBJECTIVES

To determine the effectiveness of b2-agonist for the treatment of infants with recurrent and persistent wheeze.

SEARCH STRATEGY

Relevant trials were identified using the Cochrane Airways Group database (CENTRAL), Medline and Pubmed. The database search used the following terms: Wheeze or asthma and Infant or Child and Short acting beta-agonist or Salbutamol (variants), Albuterol, Terbutaline (variants), Orciprenaline, Fenoterol

SELECTION CRITERIA

Randomised controlled trials comparing the effect of b2-agonist against placebo in children under 2 years of age who had had two or more previous episodes of wheeze, not related to another form of chronic lung disease.

DATA COLLECTION AND ANALYSIS

Eight studies met the criteria for inclusion in this meta-analysis. The studies investigated patients in three settings: at home (3 studies), in hospital (2 studies) and in the pulmonary function laboratory (3 studies). The main outcome measure was change in respiratory rate except for community based studies where symptom scores were used.

MAIN RESULTS

The studies were markedly heterogeneous and between study comparisons were limited. Improvement in respiratory rate, symptom score and oxygen saturation were noted in one study in the emergency department following two salbutamol nebulisers but this had no impact on hospital admission. There was a reduction in bronchial reactivity following salbutamol. There was no significant benefit from taking regular inhaled salbutamol on symptom scores recorded at home.

REVIEWER'S CONCLUSIONS

There is no clear benefit of using b2-agonists in the management of recurrent wheeze in the first two years of life although there is conflicting evidence. At present, further studies should only be performed if the patient group can be clearly defined and there is a suitable outcome parameter capable of measuring a response.

Clinical applications of infant lung function testing: does it contribute to clinical decision making?

Infant lung function testing is important in clinical research and recent standardisation efforts have enabled measurements to be made in infants in different laboratories throughout the world. Thus, the theoretical conditions are now fulfilled for use of these techniques in clinical practice. This review discusses the usefulness of various infant lung function techniques in a clinical setting and their potential present or future clinical application. It will focus on the role of infant lung function in the clinical management of infants with respiratory disease.

Effect of budesonide and salbutamol on surfactant properties

The objective of this study was to evaluate the in vitro effect of budesonide and salbutamol on the surfactant biophysical properties. The surface-tension properties of two bovine lipid extracts [bovine lipid extract surfactant (BLES) and Survanta] and a rat lung lavage natural surfactant were evaluated in vitro by the captive bubble surfactometer. Measurements were obtained before and after the addition of a low and high concentration of budesonide and salbutamol. Whereas salbutamol had no significant effect, budesonide markedly reduced the surface-tension-lowering properties of all surfactant preparations. Surfactant adsorption (decrease in surface tension vs. time) was significantly reduced (P < 0.01) at a high budesonide concentration with BLES, both concentrations with Survanta, and a low concentration with natural surfactant. At both concentrations, budesonide reduced (P < 0.01) Survanta film stability (minimal surface vs. time at minimum bubble volume), whereas no changes were seen with BLES. The minimal surface tension obtained for all surfactant preparations was significantly higher (P < 0.01), and the percentage of film area compression required to reach minimum surface tension was significantly lower after the addition of budesonide. In conclusion, budesonide, at concentrations used therapeutically, adversely affects the surface-tension-lowering properties of surfactant. We speculate that it may have the same adverse effect on the human surfactant.

Assessment of bronchodilator responsiveness in infants with bronchiolitis. A comparison of the tidal and the raised volume rapid thoracoabdominal compression technique

Whether bronchodilators should be used for the treatment of infants with bronchiolitis is subject to debate, partly because of the low sensitivity of the methods for assessing lung function changes in infants. In the present study, we compared the recently introduced raised volume (RVRTC) with the conventional end-tidal rapid thoracoabdominal compression (ETRTC) technique in infants with acute viral bronchiolitis. In 17 infants lung function was assessed by both methods, at baseline values and after salbutamol inhalation. Forced expiratory volumes (FEV(0.5), FEV(0.75), FEV(1.0)) were used for the quantification of RVRTC measurement, and maximal expiratory flow at functional residual capacity (Vmax (FRC)) for ETRTC measurements. A significant individual change was defined by a mean postbronchodilator value that differed from baseline value by more than twice the within-subject coefficient of variation (CV). Group mean intrasubject CVs ranged from 4.7% to 5.3% for FEV parameters; it was 14.0% for Vmax (FRC). For the group, post-bronchodilator measurements did not differ significantly from baseline measurements. For the majority of infants, however, the within-subject comparison of responses revealed substantial differences between both techniques; while no infant demonstrated a significant increase in Vmax (FRC), eight (47%) infants responded with significantly improved timed volumes. The RVRTC technique provides the investigator with a more sensitive diagnostic tool for documenting the effectiveness of therapeutic interventions on an individual basis. Furthermore, the findings of the present study provide a rationale for the application of bronchodilators in a subgroup of infants with acute bronchiolitis.