Measurement of respiratory resistance in the emergency department: feasibility in young children with acute asthma

Evaluation of Children with Malignancies for Blood and Marrow Transplantation: A Report from the ASTCT Committee on Practice Guidelines

Evaluation of a candidate for hematopoietic cell transplantation (HCT) is a complex process with substantial intercenter variability. Although literature providing guidance for evaluating the eligibility of adults is well established, similar guidance for children is lacking. To address gaps between adult recommendations and the specific needs of children, we convened a panel of pediatric HCT experts from a wide geographic range of American Society of Transplantation and Cellular Therapy (ASTCT) member institutions to offer recommendations for pediatric-focused pre-HCT evaluation. In this report from the ASTCT Committee on Practice Guidelines, we present a practical framework for evaluating children with malignancies who are candidates for HCT. We also highlight key differences from adults and emphasize areas of unmet need that require additional research to delineate best practices.

Reference values for respiratory sinusoidal oscillometry in children aged 3 to 17 years

BACKGROUND

New oscillometry devices allowing quantification of respiratory function using tidal breathing are commercially available, but reference equations are lacking for the multiethnic Canadian pediatric population.

METHODS

We conducted a prospective cross-sectional study of healthy children carefully selected for absence of asthma, atopy, tobacco smoke, obesity, prematurity, and recent respiratory infection. Triplicate measures were obtained of respiratory system resistance (Rrs) and reactance (Xrs), area under the reactance curve (AX) and resonant frequency (Fres) on four signals, whose testing order was randomized: two signals on the Resmon Pro Full (8 Hz and 5-11-19 Hz) and two signals on the tremoflo C-100 (5-37 Hz and 7-41 Hz). Feasibility was defined as the ability to obtain valid reproducible results. Prediction equations and 95% confidence intervals were derived for whole- and within-breath Rrs and Xrs and for AX and Fres, using linear regression or Generalized Additive Models for Location, Scale and Shape.

RESULTS

Of 306 children randomized, valid and reproducible results on ≥1 signal were obtained in 299 (98%) multiethnic (69% Caucasians: 8% Black: 23% Others) children aged 3-17 years, 91-189 cm tall. Standing height was the strongest predictor with no significant effect of sex, age, body mass index or ethnicity. Significant within-patient differences were observed between Resmon Pro and tremoflo C-100 measurements, justifying the derivation of device-specific reference equations.

CONCLUSION

Valid reproducible oscillometry measurements are highly feasible in children aged 3 years and older. Device-specific reference equations, valid for our multiethnic population, are derived.

Comparing lung oscillometry with a novel, portable flow interrupter device to measure lung mechanics

In the community setting, assessing spirometry in school-aged children is often limited by the unavailability of respirology technicians at the point-of-care. We developed a new technique called the Rapid Expiratory Occlusion Method (REOM) that measures respiratory resistance during normal breathing, without specialized training. The aim was to examine the concordance between respiratory resistance measured with the REOM and respiratory resistance measured by oscillometry on the tremoflo. Children aged 6-17 yr, with or without asthma, received respiratory resistance testing on the tremoflo, then on the REOM. Three to five replicates with a coefficient of variation ≤15% were obtained on each instrument; the primary outcome was the concordance between the average respiratory resistance on the REOM and that measured at 5 Hz (R₅) on the tremoflo. Thirty-two children (11 girls; 21 boys) were enrolled with a mean age of 11.2 (range 6-17) yr; after excluding two children not meeting reproducibility criteria, 9 healthy controls, 15 controlled asthmatics, and 6 poorly controlled asthmatics were included. Resistance measured on the REOM showed a strong correlation with R₅ measured on the tremoflo (P < 0.0001) with no significant differences on the Bland-Altman analyses. Children and their parents found the REOM easy to use and would consider for home use if recommended by their doctor. With the high concordance between resistance values measured on the REOM and that on the tremoflo combined with perceived ease of use, the REOM appears as a promising means for measuring lung function, thus supporting further testing of other psychometric properties.NEW & NOTEWORTHY We have developed a novel version of the interrupter technique to measure respiratory resistance. The Rapid Expiratory Occlusion Method (REOM) is a small handheld device that measures respiratory resistance and demonstrates excellent correlation with airway oscillometry. With its ease of use, REOM may be promising for use in community practice, patient's homes, and, if paired with a telemedicine application, could enable the healthcare provider to monitor patients in their homes.

Interdevice agreement in respiratory resistance values by oscillometry in asthmatic children

BACKGROUND

With several commercially available devices measuring respiratory impedance by oscillometry, the agreement between values obtained on different instruments or frequencies remains unclear. Our aim was to examine the agreement between resistance and reactance parameters on two oscillometry instruments using different waveforms.

METHODS

We conducted a prospective cross-sectional study in asthmatic children aged 3-17 years. Reproducible oscillometry measurements were obtained in random order, by blinded operators, at three modes: 5-10-15-20-25 Hz (5-25 Hz) multifrequency mode on the MasterScreen impulse oscillometry system, and both 5-25 Hz multifrequency mode and 7 Hz monofrequency on the tremoFlo C-100 airwave sinusoidal system. Resistance, reactance and within-breath parameters were examined using the intraclass correlation coefficient (ICC), paired t-test, linear regression and Bland-Altman method.

RESULTS

Of 50 participants, 44 and 38 completed between-device and within-frequency measurements, respectively. Between-device measurements at 5-25 Hz showed high (ICC 0.88-0.91) and good (ICC 0.69-0.87) agreement in resistance and reactance, respectively, but with an absolute within-patient difference (≥0.05 kPa·L-1·s-1) and proportional bias (≥30% per kPa·L-1·s-1) in all parameters and oscillatory frequencies, apart from resistance at 5 Hz. A significant proportional bias was documented in most within-breath parameters at 5 versus 7 Hz on tremoFlo.

CONCLUSION

Observed differences in resistance and reactance suggest the need for instrument- and frequency-specific paediatric normative values.

Characteristics of breath sound in infants with risk factors for asthma development

BACKGROUND

Breath sound parameters have been suggested as biomarkers of the airway narrowing in children. Using a commercially available breath sound analyzer, the characteristics of the airway condition were investigated in infants with the risk factors for asthma development.

METHODS

A total of 443 infants (mean age, 9.9 months; range, 3-24 months) were included in the present study. The breath sound parameters of the frequency limiting 99% of the power spectrum (F₉₉), the roll-off from 600 to 1200 Hz (Slope) and spectrum curve indices, the total area under the curve of the dBm data (A₃/A_T) and the ratio of power and frequency at 50% and 75% of the highest frequency of the power spectrum (RPF₇₅ and RPF₅₀), were evaluated. Using an ATS-DLD based original Japanese questionnaire, we examined the characteristics of airway condition of infants.

RESULTS

Finally, 283 infants in good health were included in the present study. The RPF₇₅, RPF₅₀, Slope and F₉₉ in infants with positive results of allergy and atopic dermatitis were significantly increased more than those in the infants with negative result.

CONCLUSIONS

Our data highlight the characteristics of breath sounds in infants with risk factors for asthma. The breath sound analysis may be useful for assessing the airways of infants for asthma development.

Changes in the breath sound spectrum with bronchodilation in children with asthma

BACKGROUND

Breath sound parameters have been suggested to be new biomarkers of airway function in patients with asthma.

METHODS

We investigated the effect of bronchodilation on breath sound parameters in sixty-four children (mean age, 8.9 years; range, 6-16 years) using a breath sound analyzer. The breath sound parameters included frequency limiting 50% and 99% of the power spectrum (F₅₀ and F₉₉), roll-off from 600-1200 Hz (slope), and spectrum curve indices such as the ratios of the third and fourth power area to the total area of the power spectrum (P₃/P_T and P₄/P_T), total area under the curve (A₃/A_T and B₄/A_T), and the ratio of power and frequency at 50% and 75% of the highest frequency of the power spectrum (RPF₇₅ and RPF₅₀). Lung function was assessed using spirometry and the forced oscillation technique (FOT). All variables were assessed before and after inhalation of a β₂-agonist.

RESULTS

The spectrum curve indices, A₃/A_T, B₄/A_T, RPF₇₅, and RPF₅₀, showed statistically significant increase following β₂-agonist inhalation. The increase in RPF₅₀ was correlated with the decrease in the difference between resistance at 5 Hz and 20 Hz, R5-R20, measured by FOT. In the multiple regression analysis adjusted for the effect of ΔRPF₇₅, the changes in A₃/A_T and B₄/A_T were positively correlated with that in the forced expiratory volume in one second.

CONCLUSIONS

The spectrum curve indices indicated bronchodilation, and may be useful for the assessment of bronchial reversibility in children with asthma.

Multicenter Study of Albuterol Use Among Infants Hospitalized with Bronchiolitis

INTRODUCTION

Although bronchiolitis is a common reason for infant hospitalization, significant heterogeneity persists in its management. The American Academy of Pediatrics currently recommends that inhaled albuterol not be used in routine care of children with bronchiolitis. Our objective was to identify factors associated with pre-admission (e.g., emergency department or primary care) use of albuterol among infants hospitalized for bronchiolitis.

METHODS

We analyzed data from a 17-center observational study of 1,016 infants (age <1 year) hospitalized with bronchiolitis between 2011-2014. Pre-admission albuterol use was ascertained by chart review, and data were available for 1,008 (99%) infants. We used multivariable logistic regression to identify infant characteristics independently associated with pre-admission albuterol use.

RESULTS

Half of the infants (n=508) received at least one albuterol treatment before admission. Across the 17 hospitals, pre-admission albuterol use ranged from 23-84%. In adjusted analysis, independent predictors of albuterol use were the following: age ≥2 months (age 2.0-5.9 months [odds ratio (OR) 2.09, 95% confidence interval (CI) {1.45-3.01}] and age 6.0-11.9 months [OR 2.89, 95% CI {1.99-4.19}]); prior use of a bronchodilator (OR 1.89, 95% CI [1.24-2.90]); and presence of wheezing documented in pre-admission chart (OR 3.94, 95% CI [2.61-5.93]). By contrast, albuterol use was less likely among those with ≥7 days since the start of breathing problem (OR 0.66, 95% CI [0.44-1.00]) and parent-reported fever (OR 0.75, 95% CI [0.58-0.96]).

CONCLUSION

Variation in pre-admission albuterol use suggests that local practice had a strong influence on use, but that patient characteristics also influenced the decision. While we agree with current guidelines in recommending against albuterol for all infants with bronchiolitis, our understanding of possible subgroups of responders may improve through investigation of infants with the identified characteristics.

Changes in the breath sound spectrum during methacholine inhalation in children with asthma

BACKGROUND AND OBJECTIVE

An effort-independent breath sound analysis is expected to be a safe and simple method for clinical assessment of changes in airway function. The effects of bronchoconstriction and bronchodilation on novel breath sound parameters in asthmatic children were investigated.

METHODS

The study population included 49 children with atopic asthma (male = 33; mean age: 10.2 years). We evaluated breath sound parameters of the highest frequency of the power spectrum (HFp), frequency limiting 50% and 99% of the power spectrum (F₅₀ and F₉₉ ) and roll-off from 600 Hz to the HFp (Slope). We also assessed new parameters obtained using the ratios of sound spectrum parameters (spectrum curve indices), such as the ratio of the third and fourth power area to the total power area (P₃ /P_T and P₄ /P_T ), the ratio of the third and fourth areas to the total area under the curve (A₃ /A_T and B₄ /A_T ) and the ratio of power and frequency at 75% of HFp and 50% of HFp (RPF₇₅ and RPF₅₀ ). This was measured before and after methacholine inhalation challenge and after β₂ agonist inhalation.

RESULTS

The parameters, F₅₀ and F₉₉ , showed no changes after methacholine inhalation. Conversely, the A₃ /A_T (12.5-10.0%, P < 0.001), B₄ /A_T (7.6-5.5%, P < 0.001), RPF₇₅ (6.7-4.0 dBm/Hz, P < 0.001) and RPF₅₀ (5.8-4.3 dBm/Hz, P < 0.001) were significantly decreased. These values returned to the original level after β₂ agonist inhalation.

CONCLUSION

Spectrum curve indices indicate bronchoconstriction and bronchodilation. These parameters may play a role in the assessment of airway narrowing in asthmatic children.

A clinical method for detecting bronchial reversibility using a breath sound spectrum analysis in infants

BACKGROUND

Using a breath sound analyzer, we investigated clinical parameters for detecting bronchial reversibility in infants.

METHODS

A total of 59 infants (4-39 months, mean age 7.8 months) were included. In Study 1, the intra- and inter-observer variability was measured in 23 of 59 infants. Breath sound parameters, the frequency at 99% of the maximum frequency (F₉₉), frequency at 25%, 50%, and 75% of the power spectrum (Q₂₅, Q₅₀, and Q₇₅), and highest frequency of inspiratory breath sounds (HFI), and parameters obtained using the ratio of parameters, i.e. spectrum curve indices, the ratio of the third and fourth area to total area (A₃/A_T and B₄/A_T, respectively) and ratio of power and frequency at F₇₅ and F₅₀ (RPF₇₅ and RPF₅₀), were calculated. In Study 2, the relationship between parameters of breath sounds and age and stature were studied. In Study 3, breath sounds were studied before and after β₂ agonist inhalation.

RESULTS

In Study 1, the data showed statistical intra- and inter-observer reliability in A₃/A_T (p=0.042 and 0.034, respectively) and RPF₅₀ (p=0.001 and 0.001, respectively). In Study 2, there were no significant relationships between age, height, weight, and BMI. In Study 3, A₃/A_T and RPF₅₀ significantly changed after β₂ agonist inhalation (p=0.001 and p<0.001, respectively).

CONCLUSIONS

Breath sound analysis can be performed in infants, as in older children, and the spectrum curve indices are not significantly affected by age-related factors. These sound parameters may play a role in the assessment of bronchial reversibility in infants.

Tidal changes in respiratory resistance are sensitive indicators of airway obstruction in children

RATIONALE

Individual assessment of airway obstruction in preschool-age children requires sensitive and specific lung function methods with low demand of cooperation. Although the forced oscillation technique (FOT) is feasible in young children, conventional measurements of respiratory impedance (Zrs) have limited diagnostic power in individuals.

OBJECTIVE

To find descriptors of within-breath Zrs that are sensitive indicators of airway obstruction during tidal breathing in children.

METHODS

Zrs was measured with (i) a standard multifrequency FOT (4-26 Hz) to assess the mean values of resistance and reactance for whole breaths and (ii) a 10 Hz signal to track the within-breath changes. Various Zrs measures obtained in healthy children (n=75) and those with acute wheeze (n=31) were investigated with receiver operator characteristic (ROC) analysis. The cut-off values obtained for airway obstruction were then tested in children with recurrent wheeze (n=20) before and after administration of salbutamol.

RESULTS

The largest area under the ROC curve (0.95) was observed for the tidal changes of resistance between the zero-flow values (ΔR). The ΔR cut-off value of 1.42 hPa s/L detected airway obstruction with sensitivity of 92% and specificity of 89% in children with acute wheeze and distinguished children with recurrent wheeze (16/20 above the cut-off value) from healthy children (22/23 below the cut-off value). Furthermore, ΔR significantly decreased after salbutamol in wheezy children but remained unchanged in healthy children.

CONCLUSIONS

New lung function measure ΔR is able to detect airway obstruction with high sensitivity and specificity and is suitable for use in lung function testing in young children.

The Forced Oscillation Technique in Paediatric Respiratory Practice

The Forced Oscillation Technique (FOT) is a lung function modality based on the application of an external oscillatory signal in order to determine the mechanical response of the respiratory system. The method is in principal noninvasive and requires minimal patient cooperation, which makes it suitable for use in young paediatric patients. The FOT has been successfully applied in various paediatric respiratory disorders, such as asthma, cystic fibrosis, and chronic lung disease of prematurity, in order to assess airway obstruction, bronchodilator response, and airway responsiveness after bronchoprovocation challenge. This technique may be more sensitive than spirometry in identifying disturbances of peripheral airways and assessing the level of asthma control or the effectiveness of therapy at the long term. Further research is required to determine the exact role of the FOT in paediatric lung function testing and to incorporate the method in specific diagnostic and management algorithms.

Pulse Oximeter Plethysmograph Estimate of Pulsus Paradoxus as a Measure of Acute Asthma Exacerbation Severity and Response to Treatment

OBJECTIVES

Pulsus paradoxus is one of the few objective bedside measures of acute asthma exacerbation severity but is difficult to measure in tachypneic and tachycardic patients and in noisy clinical environments. Our primary objective was to examine whether pulse oximeter plethysmograph estimate of pulsus paradoxus (PEP) is associated with physiologic and symptom measures of acute exacerbation severity (airway resistance by impulse oscillometry [%IOS] and the Acute Asthma Intensity Research Score [AAIRS]). Secondary objectives were to validate the previous association of PEP with percent predicted forced expiratory volume in 1 second (%FEV1 ) and to examine associations of change of PEP with change of these outcomes after 2 hours of treatment.

METHODS

This was a secondary analysis of data from a prospective observational study of patients aged 5-17 years with acute asthma exacerbations. The predictor variable, PEP, was measured using a dedicated pulse oximeter and waveform analysis program. Outcome measures included the AAIRS, %IOS, and %FEV1 at baseline and after 2 hours of treatment. We examined associations of PEP with %IOS and the AAIRS at baseline using multiple linear regression models adjusted for age, sex, and race. As secondary analyses we similarly examined the association of PEP with %FEV1 at baseline and change of PEP with change of %IOS, the AAIRS, and %FEV1 after 2 hours of treatment using multiple linear regression models adjusted for the baseline value of the outcome measure and the AAIRS.

RESULTS

Among 684 participants (61% males; 61% African American) there were associations of baseline PEP with %IOS, the AAIRS, and %FEV1 (p < 0.001). Change of PEP after 2 hours of treatment was associated with change of %FEV1 (p < 0.001) and change of the AAIRS (p = 0.01) but not with change of %IOS (p = 0.60).

CONCLUSIONS

PEP demonstrates criterion validity in predicting baseline %IOS, the AAIRS, and %FEV1 , and responsiveness to change of the AAIRS and %FEV1 . Data contained in the oximeter plethysmograph waveform might be utilized as a continuous, objective measure of acute asthma exacerbation severity and real-time response to treatment.

A novel method for detecting airway narrowing using breath sound spectrum analysis in children

BACKGROUND

Using a breath sound analyzer, we investigated new clinical parameters that are rarely affected by airflow in young children.

METHODS

A total of 65 children with asthma participated in this study (mean age 9.6 years). In Study 1, the intra- and inter-observer variability was measured. Common breath sound parameters, frequency at 99%, 75%, and 50% of the maximum frequency (F99, F75, and F50) and the highest frequency of inspiratory breath sounds were calculated. In addition, new parameters obtained using the ratio of sound spectra parameters, i.e., the spectrum curve indexes including the ratio of the third and fourth area to the total area and the ratio of power and frequency at F75 and F50, were calculated. In Study 2, 51 children underwent breath sound analyses. In Study 3, breath sounds were studied before and after methacholine inhalation.

RESULTS

In Study 1, the data showed good inter- and intra-observer reliability. In Study 2, there were significant relationships between the airflow rate, age, height, and spirometric and common breath sound parameters. However, there were no significant relationships between the airflow rate and the spectrum curve indexes. Moreover, the spectrum curve indexes showed no relationships with age, height, or spirometric parameters. In Study 3, all parameters significantly changed after methacholine inhalation.

CONCLUSIONS

Some spectrum curve indexes are not significantly affected by the airflow rate at the mouth, although they successfully indicate airway narrowing. These parameters may play a role in the assessment of bronchoconstriction in children.

Impulse oscillometry in acute and stable asthmatic children: a comparison with spirometry

OBJECTIVE

Lung function tests have attracted interest for the diagnosis and follow-up of childhood asthma in recent years. For patients who cannot perform forced expiratory maneuvers, impulse oscillometry (IOS), performed during spontaneous breathing, may be an alternative tool.

METHODS

Thirty-five acute, 107 stable asthmatic and 103 healthy children who presented to our clinic performed IOS followed by spirometry before and after salbutamol inhalation. The mean baseline and reversibility of IOS and spirometry parameters were compared between the groups. Correlation analyses were undertaken within the asthmatics, and the healthy controls separately. To distinguish the three groups, the sensitivity and specificity of baseline and reversibility values of IOS and spirometry were computed. When spirometry was taken as the gold standard, the discriminating performance of IOS to detect the airway obstruction and reversibility was investigated.

RESULTS

The mean absolute values of Zrs, R5, R5-R20, X5, X10, X15, Fres, AX, and all spirometric parameters, and the mean reversibility values of R5, R10, Fres, AX and forced expiratory volume in one second were different between the groups and the highest area under curve values to discriminate the groups was obtained from area of reactance (AX) and ΔAX. Zrs, all resistance (including R5-R20) and reactance parameters, Fres and AX were correlated with at least one spirometric parameter. Spirometric reversibility was detected by ≤-22.34 and ≤-39.05 cut-off values of ΔR5 and ΔAX, respectively.

CONCLUSIONS

IOS has shown a highly significant association with spirometric indices and reversibility testing. It may be a substitute for spirometry in children who fail to perform forced expiratory maneuvers.

Corticosteroids in the treatment of acute asthma

Asthma is a prevalent chronic disease of the respiratory system and acute asthma exacerbations are among the most common causes of presentation to the emergency department (ED) and admission to hospital particularly in children. Bronchial airways inflammation is the most prominent pathological feature of asthma. Inhaled corticosteroids (ICS), through their anti-inflammatory effects have been the mainstay of treatment of asthma for many years. Systemic and ICS are also used in the treatment of acute asthma exacerbations. Several international asthma management guidelines recommend the use of systemic corticosteroids in the management of moderate to severe acute asthma early upon presentation to the ED. On the other hand, ICS use in the management acute asthma has been studied in different contexts with encouraging results in some and negative in others. This review sheds some light on the role of systemic and ICS in the management of acute asthma and discusses the current evidence behind their different ways of application particularly in relation to new developments in the field.

Budesonide nebulization added to systemic prednisolone in the treatment of acute asthma in children: a double-blind, randomized, controlled trial

BACKGROUND

Inhaled corticosteroids, known to be effective as a maintenance medication in chronic asthma, have also been suggested as a therapy for acute asthma when given at high doses.

METHODS

A double-blind, randomized, placebo-controlled trial was conducted in children aged 2 to 12 years with moderate or severe acute asthma, as determined based on a clinical score of 5 to 15 points, where 15 is the most severe. We compared the addition of budesonide 1,500 μg vs placebo to standard acute asthma treatment, which included salbutamol, ipratropium bromide, and a single dose of prednisolone 2 mg/kg given at the beginning of therapy. The primary outcome was hospital admission rate within 4 h.

RESULTS

A total of 906 ED visits by children with moderate or severe acute asthma were evaluated. Seventy-five cases out of 458 (16.4%) in the budesonide group vs 82 of 448 (18.3%) in the placebo group were admitted (OR, 0.84; 95% CI, 0.58-1.23; P=.38). However, among cases with high baseline clinical score (≥13), significantly fewer children were admitted in the budesonide group (27 of 76 [35.5%]) than in the placebo group (39 of 73 [53.4%]; OR, 0.42; 95% CI, 0.19-0.94; P=.03).

CONCLUSIONS

The addition of budesonide nebulization did not decrease the admission rate of children with acute asthma overall. However, it may decrease the admission rate of children with severe acute asthma.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01524198; URL: www.clinicaltrials.gov

Determinants Of Oral corticosteroid Responsiveness in Wheezing Asthmatic Youth (DOORWAY): protocol for a prospective multicentre cohort study of children with acute moderate-to-severe asthma exacerbations

INTRODUCTION

Oral corticosteroids are the cornerstone of acute asthma management in the emergency department. Recent evidence has raised doubts about the efficacy of this treatment in preschool-aged children with viral-induced wheezing and in smoking adults. The aims of the study were to: (1) document the magnitude of response to oral corticosteroids in children presenting to the emergency department with moderate or severe asthma; (2) quantify potential determinants of response to corticosteroids and (3) explore the role of gene polymorphisms associated with the responsiveness to corticosteroids.

METHODS AND ANALYSIS

The design is a prospective cohort study of 1008 children aged 1-17 years meeting a strict definition of asthma and presenting with a clinical score of ≥4 on the validated Pediatric Respiratory Assessment Measure. All children will receive standardised severity-specific treatment with prednisone/prednisolone and cointerventions (salbutamol with/without ipratropium bromide). Determinants, namely viral aetiology, environmental tobacco smoke and single nucleotide polymorphism, will be objectively documented. The primary efficacy endpoint is the failure of emergency department (ED) management within 72 h of the ED visit. Secondary endpoints include other measures of asthma severity and time to recovery within 7 days of the index visit. The study has 80% power for detecting a risk difference of 7.5% associated with each determinant from a baseline risk of 21%, at an α of 0.05.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from all participating institutions. An impaired response to systemic steroids in certain subgroups will challenge the current standard of practice and call for the immediate search for better approaches. A potential host-environment interaction will broaden our understanding of corticosteroid responsiveness in children. Documentation of similar effectiveness of corticosteroids across determinants will provide the needed reassurance regarding current treatment recommendations.

RESULTS

Results will be disseminated at international conferences and manuscripts targeted at emergency physicians, paediatricians, geneticists and respirologists.

TRIAL REGISTRATION NUMBER

This study is registered at Clinicaltrials.gov (NCT02013076).

Systematic review: insufficient validation of clinical scores for the assessment of acute dyspnoea in wheezing children

BACKGROUND

A reliable, valid, and easy-to-use assessment of the degree of wheeze-associated dyspnoea is important to provide individualised treatment for children with acute asthma, wheeze or bronchiolitis.

OBJECTIVE

To assess validity, reliability, and utility of all available paediatric dyspnoea scores.

METHODS

Systematic review. We searched Pubmed, Cochrane library, National Guideline Clearinghouse, Embase and Cinahl for eligible studies. We included studies describing the development or use of a score, assessing two or more clinical symptoms and signs, for the assessment of severity of dyspnoea in an acute episode of acute asthma, wheeze or bronchiolitis in children aged 0-18 years. We assessed validity, reliability and utility of the retrieved dyspnoea scores using 15 quality criteria.

RESULTS

We selected 60 articles describing 36 dyspnoea scores. Fourteen scores were judged unsuitable for clinical use, because of insufficient face validity, use of items unsuitable for children, difficult scoring system or because complex auscultative skills are needed, leaving 22 possibly useful scores. The median number of quality criteria that could be assessed was 7 (range 6-11). The median number of positively rated quality criteria was 3 (range 1-5). Although most scores were easy to use, important deficits were noted in all scores across the three methodological quality domains, in particular relating to reliability and responsiveness.

CONCLUSION

None of the many dyspnoea scores has been sufficiently validated to allow for clinically meaningful use in children with acute dyspnoea or wheeze. Proper validation of existing scores is warranted to allow paediatric professionals to make a well balanced decision on the use of the dyspnoea score most suitable for their specific purpose.

Oscillation mechanics of the respiratory system

The mechanical impedance of the respiratory system defines the pressure profile required to drive a unit of oscillatory flow into the lungs. Impedance is a function of oscillation frequency, and is measured using the forced oscillation technique. Digital signal processing methods, most notably the Fourier transform, are used to calculate impedance from measured oscillatory pressures and flows. Impedance is a complex function of frequency, having both real and imaginary parts that vary with frequency in ways that can be used empirically to distinguish normal lung function from a variety of different pathologies. The most useful diagnostic information is gained when anatomically based mathematical models are fit to measurements of impedance. The simplest such model consists of a single flow-resistive conduit connecting to a single elastic compartment. Models of greater complexity may have two or more compartments, and provide more accurate fits to impedance measurements over a variety of different frequency ranges. The model that currently enjoys the widest application in studies of animal models of lung disease consists of a single airway serving an alveolar compartment comprising tissue with a constant-phase impedance. This model has been shown to fit very accurately to a wide range of impedance data, yet contains only four free parameters, and as such is highly parsimonious. The measurement of impedance in human patients is also now rapidly gaining acceptance, and promises to provide a more comprehensible assessment of lung function than parameters derived from conventional spirometry.

Pulmonary function tests in emergency department pediatric patients with acute wheezing/asthma exacerbation

Background. Pulmonary function tests (PFT) have been developed to analyze tidal breathing in patients who are minimally cooperative due to age and respiratory status. This study used tidal breathing tests in the ED to measure asthma severity. Design/Method. A prospective pilot study in pediatric patients (3 to 18 yrs) with asthma/wheezing was conducted in an ED setting using respiratory inductance plethysmography and pneumotachography. The main outcome measures were testing feasibility, compliance, and predictive value for admission versus discharge. Results. Forty patients were studied, of which, 14 (35%) were admitted. Fifty-five percent of the patients were classified as a mild-intermittent asthmatic, 30% were mild-persistent asthmatics, 12.5% were moderate-persistent asthmatics, and 2.5% were severe-persistent. Heart rate was higher in admitted patients as was labored breathing index, phase angle, and asthma score. Conclusions. Tidal breathing tests provide feasible, objective assessment of patient status in the enrolled age group and may assist in the evaluation of acute asthma exacerbation in the ED. Our results demonstrate that PFT measurements, in addition to asthma scores, may be useful in indicating the severity of wheezing/asthma and the need for admission.

Forced oscillation technique and childhood asthma

Most infants and preschool children are not able to voluntarily perform the physiological maneuvers required to complete the pulmonary function tests that are used in adults and older children. Recently, commercial devices using forced oscillation technique (FOT) suitable for young children have become available. In devices with FOT, an oscillation pressure wave is generated by a loud speaker, is applied to the respiratory system, usually at the mouth, and the resulting pressure-flow relationship is analyzed in terms of impedance (Zrs). Zrs encompasses both resistance (Rrs) and reactance (Xrs). Rrs is calculated from pressure and flow signals, and is a measure of central and peripheral airway caliber. Xrs is derived from the pressure in the phase with volume and is related to compliance (Crs) and inertance (Irs). These parameters individually indicate the condition of the small and large airways in each patient and indirectly suggest the presence of airway inflammation. It is agreed that the clinical diagnostic capacity of FOT is comparable to that of spirometry. One of the advantages of FOT is that minimal cooperation of the patient is needed and no respiratory maneuvers are required. The use of FOT should be considered in patients in whom spirometry or other pulmonary function tests cannot be performed or in cases where the results of other tests appear to be unreliable. In addition, this approach is effective in assessing bronchial hyperresponsiveness. Considering these qualities, FOT is a useful method to study pulmonary function in preschool children with asthma.

Impulse oscillometry in the evaluation of diseases of the airways in children

OBJECTIVE

To provide an overview of impulse oscillometry and its application to the evaluation of children with diseases of the airways.

DATA SOURCES

Medline and PubMed search, limited to English language and human disease, with keywords forced oscillation, impulse oscillometry, and asthma.

STUDY SELECTIONS

The opinions of the authors were used to select studies for inclusion in this review.

RESULTS

Impulse oscillometry is a noninvasive and rapid technique requiring only passive cooperation by the patient. Pressure oscillations are applied at the mouth to measure pulmonary resistance and reactance. It is employed by health care professionals to help diagnose pediatric pulmonary diseases such asthma and cystic fibrosis; assess therapeutic responses; and measure airway resistance during provocation testing.

CONCLUSIONS

Impulse oscillometry provides a rapid, noninvasive measure of airway impedance. It may be easily employed in the diagnosis and management of diseases of the airways in children.

Reference values for respiratory system impedance using impulse oscillometry in healthy preschool children

PURPOSE

The normal values for lung resistance and lung capacity of children, as determined by impulse oscillometry (IOS), are different for children of different ethnicities. However, reference values there is no available reference value for Korean preschool children have yet to be determined. The aim of the present study was to determine the normal ranges of IOS parameters in Korean preschool children.

METHODS

A total of 133 healthy Korean preschool children were selected from 639 children (aged 3 to 6 years) who attended kindergarten in Seongnam, Gyeonggi province, Korea. Healthy children were defined according to the European Respiratory Society (ERS) criteria. All subjects underwent lung function tests using IOS. The relationships between IOS value (respiratory resistance (Rrs) and reactance (Xrs) at 5 and 10 Hz and resonance frequency (RF)) and age, height, and weight were analyzed by simple linear and multiple linear regression analyses.

RESULTS

The IOS success rate was 89.5%, yielding data on 119 children. Linear regression identified height as the best predictor of Rrs and Xrs. Using stepwise multiple linear regressions based on age, height, and weight, we determined regression equations and coefficients of determination (R(2)) for boys (Rrs(5)=1.934-0.009×Height, R(2)=12.1%; Xrs(5)=0.774+0.006×Height-0.002×Age, R(2)=20.2% and for girls (Rrs(5)=2.201-0.012×Height, R(2)=18.2%; Xrs(5)=-0.674+0.004×Height, R(2)=10.5%).

CONCLUSION

This study provides reference values for IOS measurements of normal Korean preschool children. These provide a basis for the diagnosis and monitoring of preschool children with a variety of respiratory diseases.

Lung function testing in preschool-aged children with cystic fibrosis in the clinical setting

In cystic fibrosis (CF) lung function testing is a means of monitoring progression of lung disease. The preschool years have often been referred to as the "silent years" due to the previous lack suitable measures of lung function testing in this age group. This review outlines the various techniques of lung function testing in preschool children with CF in the clinical setting. This includes measures requiring tidal breathing including the forced oscillation technique, the interrupter technique, plethysmography, and multiple breath washout, as well as spirometry that requires respiratory maneuvers. We describe the feasibility and variability of different lung function methods used in preschoolers and report measurements made during tidal breathing have greater feasibility, although greater variability compared to spirometry. We also report associations with lung function and markers of CF lung disease. In the preschool age group measurements made during tidal breathing may be more appropriate in the clinic setting than those that require a higher degree of cooperation and specific respiratory maneuvers.maneuvers.

Respiratory impedance and response to salbutamol in asthmatic Vietnamese children

There is a high incidence of pediatric asthma in Vietnam, but little lung function data are available. The aim of the study was to compare respiratory resistance (Rrs), reactance (Xrs), and responses to salbutamol between asthmatic and healthy primary school children in Hanoi. Because respiratory mechanics vary along the breathing cycle, measurements were assessed separately in inspiration (Rrsi, Xrsi) and expiration (Rrse, Xrse).Inpatients with doctor-diagnosed asthma were measured 2-3 days following admission using the forced oscillation technique (FOT) at a single frequency (8 Hz). Z-scores and responses to salbutamol were compared between 102 asthmatics and 98 controls, and accuracy of group classification by FOT parameters was assessed by Youden index, an indicator to the proportion of subjects correctly classified in each group.In asthmatics versus controls, Rrsi-but not Rrse-was significantly larger and both Xrsi and Xrse were significantly more negative (P < 0.01). Both Rrs and Xrs responses to salbutamol were significantly larger in asthmatics than controls (P < 0.001). Youden indexes indicated response to salbutamol generally had better diagnostic values than Z-scores and was best discriminative first with Rrsi, then with Xrse.It is concluded that different FOT characteristics may be described in asthmatic and healthy Vietnamese children. The diagnostic value of each parameter depends upon the breathing cycle. Most useful in practice probably is the response to salbutamol measured by Rrsi.

[Feasibility of FeNO measurement in asthmatic children in the primary care setting. CANON Study]

AIM

Asses the feasibility of exhaled nitric oxide (FeNO) measurement in asthmatic children using a hand-held device in the primary care setting.

METHODS

Multicentre study performed in the paediatric clinics in seven Spanish primary health care centres. Each centre consecutively included 6-14 year-old children with doctor-diagnosed asthma. Children were asked to obtain two valid measurements of FeNO with the hand-held device NIOX MINO (Aerocrine AB, Solna, Sweden). Feasibility analysis included: (a) percentage of children able to perform the manoeuvre, (b) time required to obtain a successful determination, (c) number of attempts needed, and (d) acceptability of the technical procedure by clinical personnel involved in their guidance.

RESULTS

The Study enrolled 151 children. A total of 149 (98.7%) were able to perform the FeNO manoeuvre. The majority (55%) of children had previous experience of using the hand-held device. The Overall median (and Interquartile Range, IQR) of attempts needed to reach a first valid measurement was 2 (1-3) and median (IQR) of time taken was 4 min (3-5). Nurses considered the overall procedure was very easy or easy in 87.8% (teaching) and 86.5% (performing) of children. Children with previous experience performed the manoeuvre in less attempts, less time and more easily than children without experience.

CONCLUSIONS

Measurement of FeNO using NIOX MINO device is technically feasible and acceptable for children and staff in the clinical context of asthma management in primary health care. Previous experience had a positive, learning effect, in teaching and performing the FeNO manoeuvre.

Predicting an asthma exacerbation in children 2 to 5 years of age

BACKGROUND

Asthma exacerbations in young children are prevalent. Identification of symptoms or other factors that are precursors of asthma exacerbations would be useful for early treatment and prevention.

OBJECTIVES

To determine whether diary symptoms and beta2-agonist use before an exacerbation could predict an asthma exacerbation in children 2 to 5 years of age.

METHODS

Post hoc analyses were conducted on data collected in a study of 689 patients 2 to 5 years of age with asthma symptoms, randomly assigned to montelukast, 4 mg, or placebo daily for 12 weeks. During the study, 196 patients had an exacerbation. Caregiver-reported information (daytime cough, breathing difficulties, limitation of activity, nighttime cough or awakening, daytime and nighttime beta2-agonist use) were analyzed using general estimating equations with an exchangeable within-subject log odds ratio regression structure to identify predictors of an exacerbation.

RESULTS

Average symptom scores and beta2-agonist use increased significantly before exacerbation but at different rates. A combination of daytime cough and wheeze and nighttime beta2-agonist use 1 day before the exacerbation was identified as strongly predictive of an exacerbation. These methods predicted 149 (66.8%) of the exacerbations with a very low false-positive rate of 14.2%.

CONCLUSIONS

No individual symptom was predictive of an imminent asthma exacerbation, but a combination of increased daytime cough, daytime wheeze, and nighttime beta2-agonist use 1 day before an asthma exacerbation was a strong predictor of an exacerbation in children.

Impulse oscillometry versus spirometry in a long-term study of controller therapy for pediatric asthma

BACKGROUND

Determination of the benefits and limitations of specific physiologic tests has not been well studied in long-term clinical pediatric trials.

OBJECTIVE

We sought to determine the utility of impulse oscillometry in a long-term comparison of 3 controller regimens in children with persistent asthma.

METHODS

Children 6 to 14 years of age with mild-to-moderate persistent asthma were characterized with oscillometry and spirometry before entry into a clinical trial and then serially during 48 weeks of therapy with either an inhaled corticosteroid, a combination inhaled corticosteroid with a long-acting beta-agonist, or a leukotriene receptor antagonist.

RESULTS

The FEV(1)/forced vital capacity ratio, as well as the forced expiratory flow from 25% to 75% of forced vital capacity in terms of spirometric parameters and the reactance area (XA) from impulse oscillometry, appeared to complement information provided by FEV(1) when comparing the tests and factors that appeared to predict a response to treatment. XA was unique in that it, as distinct from spirometric variables, reflected ongoing improvement during the latter part of the trial. In general, improvements in XA during the latter part of the study occurred independently of indices of atopy and the level of airway responsiveness.

CONCLUSION

Assessment of respiratory mechanics over time with oscillometry might offer additional insights into the response of asthmatic patients to therapy. In particular, the pattern of improvement seen in XA over the course of therapy suggests this test might detect alterations in airway mechanics not reflected by spirometry. The possibility that changes in XA reflect ongoing improvement in small airway function deserves additional study.

The Pediatric Respiratory Assessment Measure: a valid clinical score for assessing acute asthma severity from toddlers to teenagers

OBJECTIVE

To determine the performance characteristics of the Preschool Respiratory Assessment Measure (PRAM) in preschool and school-aged children with acute asthma.

STUDY DESIGN

In a prospective cohort study, we examined the validity, responsiveness, and reliability of the PRAM in children aged 2 to 17 years with acute asthma. The study involved more than 100 nurses and physicians who recorded the PRAM on triage, after initial bronchodilation, and at disposition. Predictive validity and responsiveness were examined using disposition as outcome.

RESULTS

The PRAM was recorded in 81% (n = 782) of patients at triage. The PRAM at triage and after initial bronchodilation showed a strong association with admission (r = 0.4 and 0.5, respectively; P < .0001), thus supporting its ability to distinguish across severity levels. The responsiveness coefficient of 0.7 indicated good ability to identify change after bronchodilation. The PRAM showed good internal consistency (Cronbach alpha = 0.71) and inter-rater reliability (r = 0.78) for all patients and across all age groups.

CONCLUSIONS

Good performance characteristics were observed in all age groups, making the PRAM an attractive score for assessing asthma severity and response to treatment.

Respiratory function in healthy young children using forced oscillations

BACKGROUND

Monitoring of respiratory function is important in the diagnosis and management of respiratory disease. The forced oscillation technique requires minimal patient cooperation and is ideal for the determination of respiratory function in young children. This study aimed to develop reference ranges and to document the repeatability in healthy young children using commercially available forced oscillation equipment.

METHODS

The forced oscillation technique, which uses a pseudo-random noise forcing signal between 4 and 48 Hz, was used to measure respiratory function in healthy young children. Repeatability over a 15 min period was also assessed. Regression equations and standardised Z scores were determined for respiratory resistance (Rrs) and reactance (Xrs) at 6, 8 and 10 Hz.

RESULTS

Respiratory function was obtained in 158 healthy children aged two to seven years and between 92 and 127 cm in height. Oscillatory respiratory mechanics exhibited linear relationships with height. Within-test variability for resistance ranged between 6% and 9% and between 17% and 20% for reactance. Resistance and reactance did not change significantly over a 15 min period.

CONCLUSIONS

Reference ranges for respiratory impedance variables in healthy children aged two to seven years are presented. The short-term repeatability of forced oscillatory variables in this age group is reported, allowing appropriate cut-off values for therapeutic interventions to be defined.

Impulse Oscillometry

OBJECTIVES

To generate reference equations in North American children to be used for assessing respiratory function through the forced oscillation (Rfo) technique, and to determine the changes in oscillatory resistance, reactance, and resonant frequency (Fres) in relation to age, body height, and weight.

DESIGN/SETTING

A prospective cross-sectional study performed on healthy children selected according to strict criteria of American Thoracic Society and European Respiratory Society recommendations.

MEASUREMENTS

Triplicate measures were obtained of resistance and reactance at 5, 10, 15, 20, 25, and 35 Hz as well as Fres through the impulse oscillometer (MasterScreen IOS; Jaeger/Toennies; Höchberg, Germany). Two hundred twenty-two white children--normally distributed within the 3- to 10-year age range and 100 to 150 cm in height--were recruited in Montreal, Canada. We used regression analysis to generate multiple predictive equations separately per gender and frequency on age, height, and body weight.

RESULTS

Stepwise multiple regression in both natural and logarithmic forms for height, weight, age, and gender showed that standing height was the only significant predictor for all variables. Minimal variability was noted in each subject among the triplicate measurements (p = 0.68 to 0.96). Coherence was > 0.9 at all oscillating frequencies except 5 Hz (< 0.72), with tendencies to lower values in young children.

CONCLUSIONS

Resistance and Fres decrease by height, but also by age; and reactance increases. As opposed to our past experience with spirometry in compatible age groups, the Rfo technique was well accepted by preschool children.

Safety, tolerability, and exploratory efficacy of montelukast in 6- to 24-month-old patients with asthma

OBJECTIVE

The purpose of this study was to determine the safety and tolerability profile of montelukast 4-mg oral granules compared with placebo in children aged 6-24 months with asthma.

METHODS

This was a randomized, double-blind, placebo-controlled, parallel-group study. Children 6-24 months of age at first visit with a history of at least three episodes of physician-diagnosed asthma or 'asthma-like' symptoms and in need of controller therapy were randomized to either montelukast 4-mg oral granules or placebo once daily in the evening for 6 weeks. The primary variables were the frequency of clinical and laboratory adverse experiences. The exploratory efficacy endpoints included days without beta-agonist use, beta-agonist use per day, unscheduled physician or hospital visits for asthma, oral corticosteroid rescues for asthma, asthma attacks, discontinuation due to worsening of asthma, and total blood peripheral eosinophil counts.

RESULTS

The most common clinical adverse experiences were upper respiratory tract infection, asthma, fever, diarrhea, and vomiting occurring with similar frequencies between treatment groups. There were no clinically meaningful differences between the two treatment groups in clinical or laboratory adverse experiences and no significant differences in frequency of patients with elevated serum transaminases. Differences between the montelukast and placebo treatment groups in the exploratory efficacy endpoints of days without beta-agonist use, oral corticosteroid rescues, emergency care, asthma attacks, and discontinuations due to worsening asthma were not significant.

CONCLUSIONS

Montelukast, 4-mg oral granules, was well tolerated over 6 weeks of treatment in children aged 6-24 months with asthma.

Asthma severity scores for preschoolers displayed weaknesses in reliability, validity, and responsiveness

OBJECTIVE

To evaluate the measurement properties of asthma severity scores for use in preschool children.

METHODS

A Medline search was used to identify published asthma severity scores for use in preschool children. The measurement properties of the scores (item development, reliability, validity, responsiveness, and usability) were evaluated using a published framework.

RESULTS

Ten asthma severity scores were identified, with 19 different clinical variables used as items. Interrater agreement was assessed by five scores. Only two scores--Clinical Asthma Score (CAS) and Respiratory Distress Assessment Index (RDAI)--reported good agreement based on weighted kappa-statistics (0.64-0.90). Construct validity was reported by the CAS, Clinical Asthma Evaluation Score (CAES), the Clinical Symptom Grading System (CSGS), and the Preschool Respiratory Assessment Measure (PRAM). Correlation coefficients between asthma severity scores and clinical measures (length of stay, drug dosing interval, O2 saturation, health professional assessment, PaO2, PaCO2) ranged from 0.47 to 0.70. Responsiveness was formally demonstrated for two scales (PRAM, CAS).

CONCLUSIONS

Most asthma severity scales for use in preschool children have been informally developed. Recently developed scores (CAS, PRAM) have more rigorously evaluated their measurement properties. Research is needed to directly compare the asthma severity scores developed for use in preschool children.

Wheeze detection: recordings vs. assessment of physician and parent

BACKGROUND

Parental and professional agreement as to the presence of wheezing in infants and preschool children has been shown to be poor. Agreement on the absence or presence of physical signs on chest examination in these populations is far from perfect, even among experienced physicians.

OBJECTIVES

We sought to compare the assessment of a parent, nurse, and physician with the "gold standard" of acoustic analysis for the presence of wheezing in infants and preschool children attending a hospital clinic.

SETTING AND SUBJECTS

Urban district general hospital in North London, England. Wheezy children under 6 years old attending a "walk-in" emergency pediatric ambulatory care unit.

RESULTS

Comparisions were completed on 31 children (age range 4-62 months). The severity of wheeze was independently evaluated by a parent, nurse, and experienced pediatrician, and these were compared with breath sounds recorded and analyzed by acoustic techniques for the presence and severity of wheezing. In only 10 of 31 (32%) children did the parent and the physician agree on the wheeze severity score. In 13 infants, the parent scored higher than the doctor and in 8 the parent scored lower. In 16 (52%) of the children, there was complete agreement as to the severity of wheezing by the nurse and the physician. In 24 of the 31 children (77%), the acoustic wheeze score agreed with the physician wheeze score; in 6 children the acoustic score was lower and in 1 it was higher.

CONCLUSIONS

The physician was able reliably to judge the severity of wheeze measured objectively, whereas nurses and parents were not. This study has important implications for the interpretation of parental questionnaire studies of asthma prevalence and severity.

Repeatability of airway resistance measurements made using the interrupter technique

BACKGROUND

To be able to interpret any measurement, its repeatability should be known. This study reports the repeatability of airway resistance measurements using the interrupter technique (Rint) in children with and without respiratory symptoms.

METHODS

Children aged 2-10 years who were healthy, had persistent isolated cough, or who had previous wheeze were studied. On the same occasion, three Rint measurements were made 15 minutes apart, before and after placebo and salbutamol given in random order. Results from those given placebo first were analysed for within-occasion repeatability. Between-occasion repeatability measurements were made 2-20 weeks apart (median 3 weeks).

RESULTS

For 85 pairs of measurements before and after placebo the limits of agreement were 20% expected resistance and were unaffected by age or health status. The change in resistance following bronchodilator in one of 18 healthy children, 12 of 28 with cough, and 22 of 39 with wheeze exceeded this threshold. For between-occasion measurements the limits of agreement were 32% in 72 healthy subjects, 49% in 57 with cough, and 53% in 95 with previous wheeze.

CONCLUSION

The measurement of airways resistance by the interrupter technique is clinically meaningful when change following an intervention such as the administration of bronchodilator is greater than its within-occasion repeatability. Between-occasion repeatability is too poor to judge change confidently.

Safety profile of frequent short courses of oral glucocorticoids in acute pediatric asthma: impact on bone metabolism, bone density, and adrenal function

OBJECTIVE

Our study was designed to establish in children with asthma the safety profile of repeated short courses of oral glucocorticoids on bone mineralization and metabolism and adrenal function.

METHODS

This cross-sectional study compared the bone density, bone metabolism, and adrenal function of children who were and were not exposed to bursts of oral glucocorticoids. Children were considered exposed when, in the preceding year, they received >or=2 courses of oral glucocorticoids and were prescribed the same therapy for the index exacerbation. Children were considered unexposed when they had no exposure to oral glucocorticoids and were not prescribed any for the index exacerbation. Indices of bone metabolism were measured during the subsequent month. Cortisol responses to adrenocorticotrophic hormone stimulation and bone density were assessed 30 days after the index exacerbation.

RESULTS

Eighty-three children (48 exposed, 35 unexposed) aged 2 to 17 years were enrolled. The median exposure level was 4 courses (range: 3-11) in the preceding year. Among exposed children, a transient decrease in serum osteocalcin was observed at the end of the 5-day course with a return to baseline by 30 days; no change was observed in urine pyridinoline cross-links. Mean bone density z score was similar in the exposed (-0.61 +/- 1.0 [standard deviation]) and unexposed (-0.67 +/- 0.9) groups. No cases of abnormal response to adrenocorticotrophic hormone suggestive of adrenal insufficiency were documented in the exposed (95% confidence interval: 0%-7%) or unexposed (0%-10%) groups.

CONCLUSIONS

Repeated short courses of oral glucocorticoids in the treatment of asthma seem to be reasonably safe; this practice was not associated with any lasting perturbation in bone metabolism, bone mineralization, or adrenal function.

Clinical application of forced oscillation

This review summarizes current clinical use of the forced oscillation technique (FOT) for analysis of lung function. It presents an intuitive approach to FOT pattern recognition for interpretation of results in human subjects, and the view that FOT is now well established and, clinically, eminently useful in patients with airflow obstruction. The focus of this review is on findings that relate directly to clinical utility, with less emphasis on theoretical mechanisms. The major thrust for clinical application of FOT derives from a number of European clinical research centers. Farre and Navajas and their colleagues in Barcelona, Harf and the Lorinos and their coworkers in Paris, Peslin and Duvivier and their coworkers in Vandoeuvre-les-Nancy, Pride and coworkers in London, and Van de Woestijne, Clement, Demedts, Landser, Van Noord, and their colleagues in Leuven have essentially been responsible for clinical development of FOT over the past 25 years. Publishing space does not permit an exhaustive listing of the many contributions of these investigators, but it is intended that the present review will provide a useful infrastructure from which the reader may progress to other research citations as desired.

Comparison of the forced oscillation technique and the interrupter technique for assessing airway obstruction and its reversibility in children

The forced oscillation technique (FOT) and interrupter technique are particularly attractive for pediatric use as they require only passive cooperation from the patient. We compared the sensitivity and specificity of these methods for detecting airway obstruction and its reversibility in 118 children (3-16 yr) with asthma or chronic nocturnal cough. FOT (R(0) and R(16)) and interruption (Rint) parameters were measured at baseline and after bronchodilator inhalation (n = 94). Rint was significantly lower than R(0), especially in children with high baseline values. Baseline parameters were normalized for height and weight [R(SD)]. In children able to perform forced expiratory maneuvers (n = 93), the best discrimination between those with baseline FEV(1) < 80% or > or = 80% of predicted values was obtained with R(0)(SD). At a specificity of 80%, R(0)(SD) yielded 66% sensitivity, whereas Rint(SD) yielded only 33% sensitivity. Similarly, postbronchodilator changes in R(0)(SD) [DeltaR(0)(SD)] yielded the best discrimination between children with and without significant reversibility in FEV(1). At a specificity of 80%, DeltaR(0)(SD) yielded 67% sensitivity and DeltaRint(SD) yielded 58% sensitivity. In children unable to perform forced expiratory maneuvers (n = 25), FOT, contrary to the interrupter technique, clearly identified a subgroup of young children with high resistance values at baseline, which returned to normal after bronchodilation. We conclude that, in asthmatic children over 3 yr old, FOT measurements provide a more reliable evaluation of bronchial obstruction and its reversibility compared with the interrupter technique, especially in young children with high baseline values.

Montelukast, a leukotriene receptor antagonist, for the treatment of persistent asthma in children aged 2 to 5 years

BACKGROUND

The greatest prevalence of asthma is in preschool children; however, the clinical utility of asthma therapy for this age group is limited by a narrow therapeutic index, long-term tolerability, and frequency and/or difficulty of administration. Inhaled corticosteroids and inhaled cromolyn are the most commonly prescribed controller therapies for young children with persistent asthma, although very young patients may have difficulty using inhalers, and dose delivery can be variable. Moreover, reduced compliance with inhaled therapy relative to orally administered therapy has been reported. One potential advantage of montelukast is the ease of administering a once-daily chewable tablet; additionally, no tachyphylaxis or change in the safety profile has been evidenced after up to 140 and 80 weeks of montelukast therapy in adults and pediatric patients aged 6 to 14 years, respectively. To our knowledge, this represents the first large, multicenter study to address the effects of a leukotriene receptor antagonist in children younger than 5 years of age with persistent asthma, as well as one of the few asthma studies that incorporated end points validated for use in preschool children.

OBJECTIVE

Our primary objective was to determine the safety profile of montelukast, an oral leukotriene receptor antagonist, in preschool children with persistent asthma. Secondarily, the effect of montelukast on exploratory measures of asthma control was also studied. DESIGN AND STATISTICAL ANALYSIS: We conducted a double-blind, multicenter, multinational study at 93 centers worldwide: including 56 in the United States, and 21 in countries in Africa, Australia, Europe, North America, and South America. In this study, we randomly assigned 689 patients (aged 2-5 years) to 12 weeks of treatment with placebo (228 patients) or 4 mg of montelukast as a chewable tablet (461 patients) after a 2-week placebo baseline period. Patients had a history of physician-diagnosed asthma requiring use of beta-agonist and a predefined level of daytime asthma symptoms. Caregivers answered questions twice daily on a validated, asthma-specific diary card and, at specified times during the study, completed a validated asthma-specific quality-of-life questionnaire. Physicians and caregivers completed a global evaluation of asthma control at the end of the study. Efficacy end points included: daytime and overnight asthma symptoms, daily use of beta-agonist, days without asthma, frequency of asthma attacks, number of patients discontinued because of asthma, need for rescue medication, physician and caregiver global evaluations of change, asthma-specific caregiver quality of life, and peripheral blood eosinophil counts. Although exploratory, the efficacy end points were predefined and their analyses were written in a data analysis plan before study unblinding. At screening and at study completion, a complete physical examination was performed. Routine laboratory tests were drawn at screening and weeks 6 and 12, and submitted to a central laboratory for analysis. Adverse effects were collected from caregivers at each clinic visit. An intention-to-treat approach, including all patients with a baseline measurement and at least 1 postrandomization measurement, was performed for all efficacy end points. An analysis-of-variance model with terms for treatment, study center and stratum (inhaled/nebulized corticosteroid use, cromolyn use, or none) was used to estimate treatment group means and between-group differences and to construct 95% confidence intervals. Treatment-by-age, -sex, -race, -radioallergosorbent test, -stratum, and -study center interactions were evaluated by including each term separately. Fisher's exact test was used for between-group comparisons of the frequency of asthma attacks, discontinuations from the study because of worsening asthma, need for rescue medication, and the frequencies of adverse effects. Because of an imbalance in baseline values for eosinophil counts for the 2 treatment groups, an analysis of covariance was performed on the eosinophil change from baseline with the patient's baseline as covariate.

STUDY PARTICIPANTS

Of the 689 patients enrolled, approximately 60% were boys and 60% were white. Patients were relatively evenly divided by age: 21%, 24%, 30%, and 23% were aged 2, 3, 4, and 5 years, respectively. For 77% of the patients, asthma symptoms first developed during the first 3 years of life. During the placebo baseline period, patients had asthma symptoms on 6.1 days/week and used beta-agonist on 6.0 days/week.

RESULTS

In over 12 weeks of treatment of patients aged 2 to 5 years, montelukast administered as a 4-mg chewable tablet produced significant improvements compared with placebo in multiple parameters of asthma control including: daytime asthma symptoms (cough, wheeze, trouble breathing, and activity limitation); overnight asthma symptoms (cough); the percentage of days with asthma symptoms; the percentage of days without asthma; the need for beta-agonist or oral corticosteroids; physician global evaluations; and peripheral blood eosinophils. The clinical benefit of montelukast was evident within 1 day of starting therapy. Improvements in asthma control were consistent across age, sex, race, and study center, and whether or not patients had a positive radioallergosorbent test. Montelukast demonstrated a consistent effect regardless of concomitant use of inhaled/nebulized corticosteroid or cromolyn therapy. Caregiver global evaluations, the percentage of patients experiencing asthma attacks, and improvements in quality-of-life scores favored montelukast, but were not significantly different from placebo. There were no clinically meaningful differences between treatment groups in overall frequency of adverse effects or of individual adverse effects, with the exception of asthma, which occurred significantly more frequently in the placebo group. There were no significant differences between treatment groups in the frequency of laboratory adverse effects or in the frequency of elevated serum transaminase levels. Approximately 90% of the patients completed the study.

CONCLUSIONS

Oral montelukast (4-mg chewable tablet) administered once daily is effective therapy for asthma in children aged 2 to 5 years and is generally well tolerated without clinically important adverse effects. Similarly, in adults and children aged 6 to 14 years, montelukast improves multiple parameters of asthma control. Thus, this study confirms and extends the benefit of montelukast to younger children with persistent asthma.

Forced oscillation technique to evaluate tracheostenosis in patients with neurologic injury

STUDY OBJECTIVES

To determine the utility of forced oscillation technique (FOT) for measuring pulmonary resistance and reactance in patients with central nervous system injuries, for detection and follow-up of posttracheostomy tracheal stenosis.

DESIGN

Case series.

SETTING

A rehabilitation hospital, Brasilia, Distrito Federal, Brazil.

PATIENTS

Ten consecutive neurologically impaired patients, who had previously undergone tracheostomies, with tracheostenosis without current tracheostomy or other tracheal lesion.

INTERVENTIONS AND MEASUREMENTS

FOT evaluations were compared to tracheal diameter before and after bronchoscopic tracheostenosis dilatation procedures. Forced spirometry examinations were also obtained and compared.

RESULTS

Tracheal stenotic lesions were characterized by marked increase in resistance and reduction in reactance at low frequency and a marked increase in resonance frequency (Rf). Consistent reversal of this pattern with large reductions in total impedance of the respiratory system (Zresp) Rf and resistance at 5 Hz (R 5 Hz) were noted in all patients after each successful dilatation. Diameter of the stenosis was strongly correlated with Rf, Zresp, and R 5 Hz. The change in diameter before and after dilatation was similarly correlated with the changes in FOT values of Rf and Zresp. Spirometry values did not correlate well with the diameter of the tracheal stenosis.

CONCLUSION

The strong correlation of Rf, Zresp, and R 5 Hz to diameter of tracheostenosis suggests a previously unappreciated role for FOT in the noninvasive detection and follow-up of airway stenosis. This may be especially useful for patients with concomitant neurologic disabilities who are at risk of airway stenosis.

Clinical applications of forced oscillation techniques (FOT) in patients with bronchial asthma

BACKGROUND

Forced oscillation technique (FOT) is a method to characterize the mechanical properties of the respiratory system over a wide range of frequencies. Its most important advantage is to require minimal cooperation from the subject. This study was performed to evaluate the usefulness of the FOT applications in patients with bronchial asthma by estimating the associations between asthma severity and FOT parameters, and the relationships between FOT and spirometry parameters.

METHODS

216 patients with asthma were enrolled in this study. Patients were classified into 3 different groups according to their symptoms and pulmonary functions. Respiratory impedance, resistance (at 5 Hz, 20 Hz, 35 Hz) and resonant frequency were measured by FOT. FEV1, FVC and MMEF were measured with conventional spirometry.

RESULTS

There were significant differences of resonant frequency, resistance at 5 Hz and 20 Hz, resistance difference at 5 Hz and 20 Hz according to asthma severity (p < 0.05, respectively). Resonant frequency, resistance at 5 Hz, and impedance were significantly correlated with FEV1 (r = -0.55, -0.48, -0.49, p < 0.05, respectively), and with MMEF in patients with normal pulmonary function (r = -0.37, -0.35, -0.34, p < 0.05, respectively). Resistance at 5 Hz had similar reproducibility compared to FEV1 (resistance at 5 Hz, r = 0.78 vs FEV1, r = 0.79).

CONCLUSION

FOT is a useful and alternative method to evaluate the clinical status of bronchial asthma. Further studies will be needed to clarify its value for a wide range of clinical applications.

The Preschool Respiratory Assessment Measure (PRAM): a responsive index of acute asthma severity

OBJECTIVE

To elaborate and validate a Preschool Respiratory Assessment Measure (PRAM) that would accurately reflect the severity of airway obstruction and the response to treatment in young patients with asthma.

STUDY DESIGN

A prospective cohort study was performed in 217 children aged 3 to 6 years who presented to a pediatric emergency department with acute asthma. Respiratory resistance measured by forced oscillation served as a gold standard. Children were randomized to either the test group, in which multivariate analyses were performed to elaborate the PRAM, or the validation group, in which the characteristics of the PRAM were tested.

RESULTS

For the test group (N = 145), the best multivariate model contained 5 variables: wheezing, air entry, contraction of scalenes, suprasternal retraction, and oxygen saturation. In the validation group (N = 72), the PRAM correlated substantially with the change in resistance (r = 0.58) but modestly with the % predicted resistance measured before (r = 0.22) and after bronchodilation (r = 0.36). A change of 3 (95% CI: 2.2, 3.0) indicated a clinically important change.

CONCLUSIONS

PRAM appears to be a responsive but moderately discriminative tool for assessing acute asthma severity. This measure, designed for preschool-aged children, has been validated against a concurrent measure of lung function.

Validation of a pediatric asthma caregiver diary

BACKGROUND

Young children are generally not able to consistently and reliably perform tests of airway function, and normative values are not available. Reliable and valid measures of parental reporting of asthma symptoms and functioning are needed to determine the efficacy of asthma interventions.

OBJECTIVE

A pediatric asthma caregiver diary was developed and validated for use in interventional asthma studies.

METHODS

A 3-week prospective study of 125 caregiver parents and their children, aged 2 to 5 years, with persistent asthma was conducted. At baseline, children were classified as either stable (no change to anti-inflammatory therapy) or unstable (anti-inflammatory therapy added or increased).

RESULTS

A symptom scale and day without asthma symptoms (DWAS) were defined from pediatric asthma caregiver diary questions. The scale and DWAS statistically differentiated between the stable and unstable groups at week 1 and detected change between the 2 groups (P <.01). On average, caregivers reported low symptom scores. However, the frequency of DWAS was only 43% of days in the stable group and 22% in the unstable group.

CONCLUSION

The pediatric asthma caregiver diary scale and DWAS have acceptable measurement characteristics for use in clinical trials of children with asthma symptoms. The DWAS indicates an opportunity for improvement in asthma control in this population.

Avaliação de mecânica ventilatória por oscilações forçadas: fundamentos e aplicações clínicas

Requerendo apenas cooperação passiva e fornecendo novos parâmetros para análise da mecânica ventilatória, a técnica de oscilações forçadas (TOF) apresenta características complementares aos métodos clássicos de avaliação pulmonar. Neste trabalho, inicialmente é apresentada uma revisão dos princípios da técnica juntamente com uma discussão sobre suas vantagens e atuais limitações. A performance da técnica é comparada com a dos métodos clássicos na detecção de afecções respiratórias. As principais aplicações clínicas reportadas anteriormente na literatura, incluindo a avaliação da mecânica ventilatória infantil, estudos em neonatos, monitorização de pacientes sob ventilação mecânica, medicina ocupacional e avaliação de distúrbios no sono, são revisadas e discutidas. Com base na revisão efetuada e nos resultados obtidos em estudos efetuados em laboratório, os autores concluem que a TOF pode contribuir para um exame mais detalhado, assim como para facilitar a realização de testes de função pulmonar em condições nas quais as técnicas tradicionais não são adequadas.

Use of the forced oscillation technique to assess airway obstruction and reversibility in children

The forced oscillation technique (FOT) is particularly attractive in a pediatric setting as it requires only passive cooperation from the child. We assessed the sensitivity and specificity of this method for detecting airway obstruction and its reversibility in 313 children (3 to 16 yr of age) with asthma or chronic nocturnal cough. Baseline and post-bronchodilator (n = 251) resistance were measured (R(0)) with the FOT. Baseline R(0) was normalized for height and weight [R(0)(SD)]. In children able to perform forced expiratory maneuvers (n = 181), R(0)(SD) was independently correlated with FEV(1) (p < 0.02) and maximal expiratory flow at 50% (MEF(50)) (p < 0.004). The optimal R(0)(SD) cutoff value given by receiver operating characteristic (ROC) curves to discriminate between children with baseline FEV(1) < 80% or >/= 80% of predicted values yielded 84% sensitivity and 73% specificity. Post-bronchodilator changes in R(0)(SD) [DeltaR(0)(SD)] were mostly correlated to changes in MEF(50). The optimal DeltaR(0)(SD) cutoff value to discriminate between children with the presence or absence of significant reversibility in FEV(1) yielded 69% sensitivity and 78% specificity. In children unable to perform forced expiratory maneuvers (n = 132), this DeltaR(0)(SD) cutoff clearly identified a subgroup of young children with high R(0) values at baseline, that returned to normal after bronchodilation. We conclude that FOT measurements allow reliable evaluation of bronchial obstruction and its reversibility in asthmatic children over 3 yr old.

Advances in pulmonary laboratory testing

This review examines emerging technologies that are of potential use in the routine clinical pulmonary laboratory. These technologies include the following: the measurement of exercise tidal flow-volume (FV) loops plotted within the maximal FV envelope for assessment of ventilatory constraint during exercise; the use of negative expiratory pressures to asses expiratory flow limitation in various populations and under various conditions; the potential use of expired nitric oxide for assessing airway inflammation; and the use of forced oscillation for assessment of airway resistance. These methodologies have been used extensively in the research setting and are gaining increasing popularity and clinical application due to the availability of commercially available, simplified, and automated systems. An overview of each technique, its potential advantages and limitations will be discussed, along with suggestions for further investigation that is considered necessary prior to extensive clinical use.