Weaning strategies for children on home invasive mechanical ventilation

Children who require home mechanical ventilation (HMV) with an artificial airway or invasive mechanical ventilation (HMV) have a possibility of successful weaning due to the potential of compensatory lung growth. Internationally accepted guidelines on how to wean from HMV in children is not available, we summarize the weaning strategies from the literature reviews combined with our 27-year experience in the Pediatric Home Respiratory Care program at the tertiary care center in Thailand. The readiness to wean is considered in patients with hemodynamic stability, having effective cough measured by maximal inspiratory pressure, requiring a fraction of inspired oxygen (FiO2) < 40%, positive end expiratory pressure <5 cmH2O, and acceptable arterial blood gases. The strategies of weaning is start weaning during the daytime while the child is awake and close monitoring is feasible. Disconnect time is gradually increased through naps and sleeping hours. Weaning from the conventional mechanical ventilator to Bilevel PAP or CPAP are optional. Factors affected the successful weaning are mainly the underlying diseases, complications, growth and development, caregivers, and resources. Weaning should be stopped during acute illness or increased work of breathing. The readiness for decannulation could be determined by using the speaking devices, tracheostomy capping, and measurement of end-expiratory pressure. Polysomnography and airway evaluation by bronchoscopy are recommended before decannulation. Weaning when the child is ready is crucial because living with HMV can be challenging and stressful. Failure to remove a tracheostomy when indicated can result in delayed speech, social problems as well as risk for infection.

Nasal Suctioning Therapy Among Infants With Bronchiolitis Discharged Home From the Emergency Department: A Randomized Clinical Trial

Importance

Although nasal suctioning is the most frequently used supportive management for bronchiolitis, its benefit remains unknown.

Objective

To evaluate the effectiveness of enhanced vs minimal nasal suctioning in treating infants with bronchiolitis after discharge from the emergency department (ED).

Design, Setting, and Participants

This single-blind, parallel-group, randomized clinical trial was conducted from March 6, 2020, to December 15, 2022, at 4 tertiary-care Canadian pediatric EDs. Participants included otherwise healthy infants aged 1 to 11 months with a diagnosis of bronchiolitis who were discharged home from the ED.

Interventions

Participants were randomized to minimal suctioning via bulb or enhanced suctioning via a battery-operated device before feeding for 72 hours.

Main Outcomes and Measures

The primary outcome was additional resource use, a composite of unscheduled revisits for bronchiolitis or use of additional suctioning devices for feeding and/or breathing concerns. Secondary outcomes included health care utilization, feeding and sleeping adequacy, and satisfaction.

Results

Of 884 screened patients, 352 were excluded for criteria, 79 declined participation, 81 were otherwise excluded, 372 were randomized (185 to the minimal suction group and 187 to the enhanced suction group), and 367 (median [IQR] age, 4 [2-6] months; 221 boys [60.2%]) completed the trial (184 in the minimal suction and 183 in the enhanced suction group). Additional resource use occurred for 68 of 184 minimal suction participants (37.0%) vs 48 of 183 enhanced suction participants (26.2%) (absolute risk difference, 0.11; 95% CI, 0.01 to 0.20; P = .03). Unscheduled revisits occurred for 47 of 184 minimal suction participants (25.5%) vs 40 of 183 enhanced suction participants (21.9%) (absolute risk difference, 0.04; 95% CI, -0.05 to 0.12; P = .46). A total of 33 of 184 parents in the minimal suction group (17.9%) used additional suctioning devices vs 11 of 183 parents in the enhanced suction group (6.0%) (absolute risk difference, 0.12; 95% CI, 0.05 to 0.19; P < .001). No significant between-group differences were observed for all bronchiolitis revisits (absolute risk difference, 0.07; 95% CI, -0.02 to 0.16; P = .15), ED revisits (absolute risk difference, 0.04; 95% CI, -0.03 to 0.12; P = .30), parental care satisfaction (absolute risk difference, -0.02; 95% CI, -0.10 to 0.06; P = .70), and changes from baseline to 72 hours in normal feeding (difference in differences, 0.03; 95% CI, -0.10 to 0.17; P = .62), normal sleeping (difference in differences, 0.05; 95% CI, -0.08 to 0.18; P = .47), or normal parental sleeping (difference in differences, 0.10; 95% CI, -0.02 to 0.23; P = .09). Parents in the minimal suction group were less satisfied with the assigned device (62 of 184 [33.7%]) than parents in the enhanced suction group (145 of 183 [79.2%]) (risk difference, 0.45; 95% CI, 0.36 to 0.54; P < .001).

Conclusions and Relevance

Compared with minimal suctioning, enhanced suctioning after ED discharge with bronchiolitis did not alter the disease course because there were no group differences in revisits or feeding and sleeping adequacy. Minimal suctioning resulted in higher use of nonassigned suctioning devices and lower parental satisfaction with the assigned device.

Trial Registration

ClinicalTrials.gov Identifier: NCT03361371.

European Respiratory Society/American Thoracic Society technical statement: standardisation of the measurement of lung volumes, 2023 update

This document updates the 2005 European Respiratory Society (ERS) and American Thoracic Society (ATS) technical standard for the measurement of lung volumes. The 2005 document integrated the recommendations of an ATS/ERS task force with those from an earlier National Heart, Lung, and Blood Institute workshop that led to the publication of background papers between 1995 and 1999 and a consensus workshop report with more in-depth descriptions and discussion. Advancements in hardware and software, new research and emerging approaches have necessitated an update to the 2005 technical standard to guide laboratory directors, physiologists, operators, pulmonologists and manufacturers. Key updates include standardisation of linked spirometry, new equipment quality control and validation recommendations, generalisation of the multiple breath washout concept beyond nitrogen, a new acceptability and grading system with addition of example tracings, and a brief review of imaging and other new techniques to measure lung volumes. Future directions and key research questions are also noted.

International consensus on lung function testing during COVID-19 pandemic and beyond

COVID-19 has negatively affected the delivery of respiratory diagnostic services across the world due to the potential risk of disease transmission during lung function testing. Community prevalence, reoccurrence of COVID-19 surges, and the emergence of different variants of the SARS-CoV-2 virus have impeded attempts to restore services. Finding consensus on how to deliver safe lung function services for both patients attending and for staff performing the tests are of paramount importance.

This international statement presents the consensus opinion of 23 experts in the field of lung function and respiratory physiology balanced with evidence from the reviewed literature. It describes a robust roadmap for restoration and continuity of lung function testing services during the COVID-19 pandemic and beyond.

Important strategies presented in this consensus statement relate to the patient journey when attending for lung function tests. We discuss appointment preparation, operational and environmental issues, testing room requirements including mitigation strategies for transmission risk, requirement for improved ventilation, maintaining physical distance, and use of personal protection equipment. We also provide consensus opinion on precautions relating to specific tests, filters, management of special patient groups, and alternative options to testing in hospitals.

The pandemic has highlighted how vulnerable lung function services are and forces us to re-think how long term mitigation strategies can protect our services during this and any possible future pandemic. This statement aspires to address the safety concerns that exist and provide strategies to make lung function tests and the testing environment safer when tests are required.

Association Between Intravenous Magnesium Therapy in the Emergency Department and Subsequent Hospitalization Among Pediatric Patients With Refractory Acute Asthma: Secondary Analysis of a Randomized Clinical Trial

IMPORTANCE

Despite guidelines recommending administration of intravenous (IV) magnesium sulfate for refractory pediatric asthma, the number of asthma-related hospitalizations has remained stable, and IV magnesium therapy is independently associated with hospitalization.

OBJECTIVE

To examine the association between IV magnesium therapy administered in the emergency department (ED) and subsequent hospitalization among pediatric patients with refractory acute asthma after adjustment for patient-level variables.

DESIGN, SETTING, AND PARTICIPANTS

This post hoc secondary analysis of a double-blind randomized clinical trial of children with acute asthma treated from September 26, 2011, to November 19, 2019, at 7 Canadian tertiary care pediatric EDs was conducted between September and November 2020. In the randomized clinical trial, 816 otherwise healthy children aged 2 to 17 years with Pediatric Respiratory Assessment Measure (PRAM) scores of 5 points or higher after initial therapy with systemic corticosteroids and inhaled albuterol with ipratropium bromide were randomly assigned to 3 nebulized treatments of albuterol plus either magnesium sulfate or 5.5% saline placebo.

EXPOSURES

Intravenous magnesium sulfate therapy (40-75 mg/kg).

MAIN OUTCOMES AND MEASURES

The association between IV magnesium therapy in the ED and subsequent hospitalization for asthma was assessed using multivariable logistic regression analysis. Analyses were adjusted for year epoch at enrollment, receipt of IV magnesium, PRAM score after initial therapy and at ED disposition, age, sex, duration of respiratory distress, previous intensive care unit admission for asthma, hospitalizations for asthma within the past year, atopy, and receipt of oral corticosteroids within 48 hours before arrival in the ED, nebulized magnesium, and additional albuterol after inhaled magnesium or placebo, with site as a random effect.

RESULTS

Among the 816 participants, the median age was 5 years (interquartile range, 3-7 years), 517 (63.4%) were boys, and 364 (44.6%) were hospitalized. A total of 215 children (26.3%) received IV magnesium, and 190 (88.4%) of these children were hospitalized compared with 174 of 601 children (29.0%) who did not receive IV magnesium. Multivariable factors associated with hospitalization were IV magnesium receipt from 2011 to 2016 (odds ratio [OR], 22.67; 95% CI, 6.26-82.06; P < .001) and from 2017 to 2019 (OR, 4.19; 95% CI, 1.99-8.86; P < .001), use of additional albuterol (OR, 5.94; 95% CI, 3.52-10.01; P < .001), and increase in PRAM score at disposition (per 1-U increase: OR, 2.24; 95% CI, 1.89-2.65; P < .001). In children with a disposition PRAM score of 3 or lower, receipt of IV magnesium therapy was associated with hospitalization (OR, 8.52; 95% CI, 2.96-24.41; P < .001).

CONCLUSIONS AND RELEVANCE

After adjustment for patient-level characteristics, receipt of IV magnesium therapy after initial asthma treatment in the ED was associated with subsequent hospitalization. This association also existed among children with mild asthma at ED disposition. Evidence of a benefit of IV magnesium regarding hospitalization may clarify its use in the treatment of refractory pediatric asthma.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01429415.

Humidified and Heated Cascade Impactor for Aerosol Sizing

Aerosol sizing is generally measured at ambient air but human airways have different temperature (37°C) and relative humidity (100%) which can affect particle size in airways and consequently deposition prediction. This work aimed to develop and evaluate a new method using cascade impactor to measure particle size at human physiological temperature and humidity (HPTH) taking into account ambient air conditions. A heated and humidified trachea was built and a cascade impactor was heated to 37°C and humidified inside. Four medical aerosols [jet nebulizer, mesh nebulizer, Presurized Metered Dose Inhaler (pMDI), and Dry Powder Inhaler (DPI)] under ambient conditions and at HPTH were tested. MMAD was lower at HPTH for the two nebulizers; it was similar at ambient conditions and HPTH for pMDI, and the mass of particles smaller than 5 μm decreased for DPI at HPTH (51.9 vs. 82.8 μg/puff). In conclusion, we developed a new method to measure particle size at HPTH affecting deposition prediction with relevance. In vivo studies are required to evaluate the interest of this new model to improve the precision of deposition prediction.

Effect of Nebulized Magnesium vs Placebo Added to Albuterol on Hospitalization Among Children With Refractory Acute Asthma Treated in the Emergency Department: A Randomized Clinical Trial

IMPORTANCE

While intravenous magnesium decreases hospitalizations in refractory pediatric acute asthma, it is variably used because of invasiveness and safety concerns. The benefit of nebulized magnesium to prevent hospitalization is unknown.

OBJECTIVE

To evaluate the effectiveness of nebulized magnesium in children with acute asthma remaining in moderate or severe respiratory distress after initial therapy.

DESIGN, SETTING, AND PARTICIPANTS

A randomized double-blind parallel-group clinical trial from September 26, 2011, to November 19, 2019, in 7 tertiary-care pediatric emergency departments in Canada. The participants were otherwise healthy children aged 2 to 17 years with moderate to severe asthma defined by a Pediatric Respiratory Assessment Measure (PRAM) score of 5 or greater (on a 12-point scale) after a 1-hour treatment with an oral corticosteroid and 3 inhaled albuterol and ipratropium treatments. Of 5846 screened patients, 4332 were excluded for criteria, 273 declined participation, 423 otherwise excluded, 818 randomized, and 816 analyzed.

INTERVENTIONS

Participants were randomized to 3 nebulized albuterol treatments with either magnesium sulfate (n = 410) or 5.5% saline placebo (n = 408).

MAIN OUTCOMES AND MEASURES

The primary outcome was hospitalization for asthma within 24 hours. Secondary outcomes included PRAM score; respiratory rate; oxygen saturation at 60, 120, 180, and 240 minutes; blood pressure at 20, 40, 60, 120, 180, and 240 minutes; and albuterol treatments within 240 minutes.

RESULTS

Among 818 randomized patients (median age, 5 years; 63% males), 816 completed the trial (409 received magnesium; 407, placebo). A total of 178 of the 409 children who received magnesium (43.5%) were hospitalized vs 194 of the 407 who received placebo (47.7%) (difference, -4.2%; absolute risk difference 95% [exact] CI, -11% to 2.8%]; P = .26). There were no significant between-group differences in changes from baseline to 240 minutes in PRAM score (difference of changes, 0.14 points [95% CI, -0.23 to 0.50]; P = .46); respiratory rate (0.17 breaths/min [95% CI, -1.32 to 1.67]; P = .82); oxygen saturation (-0.04% [95% CI, -0.53% to 0.46%]; P = .88); systolic blood pressure (0.78 mm Hg [95% CI, -1.48 to 3.03]; P = .50); or mean number of additional albuterol treatments (magnesium: 1.49, placebo: 1.59; risk ratio, 0.94 [95% CI, 0.79 to 1.11]; P = .47). Nausea/vomiting or sore throat/nose occurred in 17 of the 409 children who received magnesium (4%) and 5 of the 407 who received placebo (1%).

CONCLUSIONS AND RELEVANCE

Among children with refractory acute asthma in the emergency department, nebulized magnesium with albuterol, compared with placebo with albuterol, did not significantly decrease the hospitalization rate for asthma within 24 hours. The findings do not support use of nebulized magnesium with albuterol among children with refractory acute asthma.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01429415.

ERS technical standard on bronchial challenge testing: pathophysiology and methodology of indirect airway challenge testing

Recently, this international task force reported the general considerations for bronchial challenge testing and the performance of the methacholine challenge test, a "direct" airway challenge test. Here, the task force provides an updated description of the pathophysiology and the methods to conduct indirect challenge tests. Because indirect challenge tests trigger airway narrowing through the activation of endogenous pathways that are involved in asthma, indirect challenge tests tend to be specific for asthma and reveal much about the biology of asthma, but may be less sensitive than direct tests for the detection of airway hyperresponsiveness. We provide recommendations for the conduct and interpretation of hyperpnoea challenge tests such as dry air exercise challenge and eucapnic voluntary hyperpnoea that provide a single strong stimulus for airway narrowing. This technical standard expands the recommendations to additional indirect tests such as hypertonic saline, mannitol and adenosine challenge that are incremental tests, but still retain characteristics of other indirect challenges. Assessment of airway hyperresponsiveness, with direct and indirect tests, are valuable tools to understand and to monitor airway function and to characterise the underlying asthma phenotype to guide therapy. The tests should be interpreted within the context of the clinical features of asthma.

Does Size Matter When Calculating the "Correct" Tidal Volume for Pediatric Mechanical Ventilation?: A Hypothesis Based on FVC

BACKGROUND

Tidal volumes standardized to predicted body weight are recommended for adult mechanical ventilation, but children are frequently ventilated by using measured body weight. The goal of this study was to examine the difference in FVC (in milliliters per kilogram [mL/kg]) by using measured body weight compared with predicted body weight in children.

METHODS

This retrospective analysis included outpatient pulmonary function tests (PFTs) from two datasets. Dataset one included 6- to 19-year-old patients undergoing PFTs from the nationally representative Canadian Health Measures Survey. Dataset two included 6- to 20-year-old patients undergoing PFTs at a freestanding children's hospital. FVC mL/kg values were analyzed against BMI z scores to show changes in FVC vs BMI between measured and predicted weight.

RESULTS

Dataset one included 5,394 PFTs from the Canadian survey. FVC from measured weight decreased as the BMI z score group increased. The median FVC from measured weight was 81.4 mL/kg in the lowest BMI z score group and 51.7 mL/kg in the highest BMI z score group. FVC from predicted weight increased slightly with increasing BMI z score group. Dataset two included 8,472 patient PFTs from clinical measurement. A decline in median FVC from measured weight (from 69.4 to 37.6 mL/kg) as BMI z score group increased was also seen.

CONCLUSIONS

FVC differs significantly when standardizing to measured weight vs predicted weight. Obese children have lung volumes reflecting their predicted body weight from height. Children with low or normal BMI have lung volumes reflecting measured body weight. These findings suggest that targeting tidal volume by using the lower of measured and predicted body weights would be the most lung-protective strategy.

Recommendations for a Standardized Pulmonary Function Report. An Official American Thoracic Society Technical Statement

BACKGROUND

The American Thoracic Society committee on Proficiency Standards for Pulmonary Function Laboratories has recognized the need for a standardized reporting format for pulmonary function tests. Although prior documents have offered guidance on the reporting of test data, there is considerable variability in how these results are presented to end users, leading to potential confusion and miscommunication.

METHODS

A project task force, consisting of the committee as a whole, was approved to develop a new Technical Standard on reporting pulmonary function test results. Three working groups addressed the presentation format, the reference data supporting interpretation of results, and a system for grading quality of test efforts. Each group reviewed relevant literature and wrote drafts that were merged into the final document.

RESULTS

This document presents a reporting format in test-specific units for spirometry, lung volumes, and diffusing capacity that can be assembled into a report appropriate for a laboratory's practice. Recommended reference sources are updated with data for spirometry and diffusing capacity published since prior documents. A grading system is presented to encourage uniformity in the important function of test quality assessment.

CONCLUSIONS

The committee believes that wide adoption of these formats and their underlying principles by equipment manufacturers and pulmonary function laboratories can improve the interpretation, communication, and understanding of test results.

ERS technical standard on bronchial challenge testing: general considerations and performance of methacholine challenge tests

This international task force report updates general considerations for bronchial challenge testing and the performance of the methacholine challenge test. There are notable changes from prior recommendations in order to accommodate newer delivery devices. Rather than basing the test result upon a methacholine concentration (provocative concentration (PC20) causing a 20% fall in forced expiratory volume in 1 s (FEV1)), the new recommendations base the result upon the delivered dose of methacholine causing a 20% fall in FEV1 (provocative dose (PD20)). This end-point allows comparable results from different devices or protocols, thus any suitable nebuliser or dosimeter may be used, so long as the delivery characteristics are known. Inhalation may be by tidal breathing using a breath-actuated or continuous nebuliser for 1 min (or more), or by a dosimeter with a suitable breath count. Tests requiring maximal inhalations to total lung capacity are not recommended because the bronchoprotective effect of a deep breath reduces the sensitivity of the test.

Effect of Oxygen Desaturations on Subsequent Medical Visits in Infants Discharged From the Emergency Department With Bronchiolitis

IMPORTANCE

Reliance on pulse oximetry has been associated with increased hospitalizations, prolonged hospital stay, and escalation of care.

OBJECTIVE

To examine whether there is a difference in the proportion of unscheduled medical visits within 72 hours of emergency department discharge in infants with bronchiolitis who have oxygen desaturations to lower than 90% for at least 1 minute during home oximetry monitoring vs those without desaturations.

DESIGN, SETTING, AND PARTICIPANTS

Prospective cohort study conducted from February 6, 2008, to April 30, 2013, at a tertiary care pediatric emergency department in Toronto, Ontario, Canada, among 118 otherwise healthy infants aged 6 weeks to 12 months discharged home from the emergency department with a diagnosis of acute bronchiolitis.

MAIN OUTCOMES AND MEASURES

The primary outcome was unscheduled medical visits for bronchiolitis, including a visit to any health care professional due to concerns about respiratory symptoms, within 72 hours of discharge in infants with and without desaturations. Secondary outcomes included examination of the severity and duration of the desaturations, delayed hospitalizations within 72 hours of discharge, and the effect of activity on desaturations.

RESULTS

A total of 118 infants were included (mean [SD] age, 4.5 [2.1] months; 69 male [58%]). During a mean (SD) monitoring period of 19 hours 57 minutes (10 hours 37 minutes), 75 of 118 infants (64%) had at least 1 desaturation event (median continuous duration, 3 minutes 22 seconds; interquartile range, 1 minute 54 seconds to 8 minutes 50 seconds). Among the 118 infants, 59 (50%) had at least 3 desaturations, 12 (10%) had desaturation for more than 10% of the monitored time, and 51 (43%) had desaturations lasting 3 or more minutes continuously. Of the 75 infants who had desaturations, 59 (79%) had desaturation to 80% or less for at least 1 minute and 29 (39%) had desaturation to 70% or less for at least 1 minute. Of the 75 infants with desaturations, 18 (24%) had an unscheduled visit for bronchiolitis as compared with 11 of the 43 infants without desaturation (26%) (difference, -1.6%; 95% CI, -0.15 to ∞; P = .66). One of the 75 infants with desaturations (1%) and 2 of the 43 infants without desaturations (5%) were hospitalized within 72 hours (difference, -3.3%; 95% CI, -0.04 to 0.10; P = .27). Among the 62 infants with desaturations who had diary information, 48 (77%) experienced them during sleep or while feeding.

CONCLUSIONS AND RELEVANCE

The majority of infants with mild bronchiolitis experienced recurrent or sustained desaturations after discharge home. Children with and without desaturations had comparable rates of return for care, with no difference in unscheduled return medical visits and delayed hospitalizations.

Magnesium nebulization utilization in management of pediatric asthma (MagNUM PA) trial: study protocol for a randomized controlled trial

BACKGROUND

Up to 30 % of children with acute asthma are refractory to initial therapy, and 84 % of this subpopulation needs hospitalization. Finding safe, noninvasive, and effective strategies to treat this high-risk group would substantially decrease hospitalizations, healthcare costs, and the psycho-social burden of the disease. Whereas intravenous magnesium (Mg) is effective in severe refractory asthma, its use is sporadic due to safety concerns, with the main treatment goal being to prevent intensive care unit admission. In contrast, nebulized Mg is noninvasive, allows higher pulmonary drug concentrations, and has a much higher safety potential due to the lower rate of systemic delivery. Previous studies of inhaled Mg show disparate results due to the use of unknown/inefficient delivery methods and other methodological flaws.

METHODS/DESIGN

The study is a randomized double-blind controlled trial in seven Canadian pediatric Emergency Departments (two-center pilot 2011 to 2014, Canada-wide November 2014 to December 2017). The trial will include 816 otherwise healthy children who are 2 to 17 years old, having had at least one previous wheezing episode, have received systemic corticosteroids, and have a Pediatric Respiratory Assessment Measure (PRAM) ≥ 5 points after three salbutamol and ipratropium treatments for a current acute asthma exacerbation. Eligible consenting children will receive three experimental treatments of nebulized salbutamol with either 600 mg of Mg sulfate or placebo 20 min apart, using an Aeroneb Go nebulizer, which has been shown to maximize pulmonary delivery while maintaining safety. The primary outcome is hospitalization within 24 h of the start of the experimental therapy for persistent respiratory distress or supplemental oxygen. Secondary outcomes include all-cause hospitalization within 24 h, PRAM, vital signs, number of bronchodilator treatments by 240 min, and the association between the difference in the primary outcome between the groups, age, gender, baseline PRAM, atopy, and "viral induced wheeze" phenotype (Fig. 1).

DISCUSSION

If effective, inhaled Mg may represent an effective strategy to minimize morbidity in pediatric refractory acute asthma. Unlike previous works, this trial targets nonresponders to optimized initial therapy who are the most likely to benefit from inhaled Mg. Future dissemination of results will include knowledge translation, incorporation into a Cochrane Review, presentation at scientific meetings, and a peer-reviewed publication.

TRIAL REGISTRATION

NCTO1429415 , registered 2 September 2011.

Exposure to industrial air pollutant emissions and lung function in children: Canadian Health Measures Survey, 2007 to 2011

BACKGROUND

Long-term exposure to ambient air pollution has been associated with adverse effects on children's lung function. Few studies have examined lung function in relation to industrial emissions of air pollutants.

DATA AND METHODS

This cross-sectional study was based on 2,833 respondents aged 6 to 18 for whom spirometry data were collected by the Canadian Health Measures Survey, 2007 to 2011. The weighted sum of industrial air emissions of nitrogen oxides (NOₓ) and fine particulate matter (PM2.5) within 25 km of the respondent's residence was derived using National Pollutant Release Inventory data. Multivariate linear regression was used to examine the relationship between NOₓ and PM2.5 emissions and forced vital capacity (FVC), the forced expiratory volume in 1 sec (FEV₁), and the ratio of the two (FEV₁/FVC).

RESULTS

Industrial air emissions of NOₓ were not significantly associated with lung function among males or females. Emissions of PM2.5 were negatively associated with FEV₁ and FEV₁/FVC, but not FVC, among males. PM2.5 was not significantly related to lung function among females.

INTERPRETATION

The associations that emerged between lung function and industrial emissions of PM2.5 among males were consistent with airway obstruction. Further research is warranted to investigate the gender differences observed in this study.

Does the FEF25-75 or the FEF75 have any value in assessing lung disease in children with cystic fibrosis or asthma?

While the FEV1 had been recognized as an excellent indicator of disability, it is not very sensitive to early and mild disease. In cystic fibrosis (CF) small airway disease is believed to be one of the early hallmarks and indices such as the FEF25-75 and FEF75 have been proposed as sensitive markers of early disease. The site of early disease in asthma is not as well worked out. Recently a study of more than 20,000 spirometries found that neither of these indices added anything to the FEV1 /FVC but that study was not disease specific and contained both adults and children and the adults were the most numerous. To see if this would be true in children, 1,175 spirograms from children 6 to 18 years of age with CF or asthma whose FEV1 and FVC were above the lower limit of normal were taken from sequential studies. The data expressed in z scores was plotted with either the FEF25-75 or FEF75 plotted against FEV1 /FVC. In both diseases, but particularly in asthma, the FEV1 /FVC was more likely to be abnormal than either of the other two indices for suggesting that for children, early, or mild disease will be more apparent using the FEV1 /FVC than any other index.

Physiological correlates of pulmonary function in children with cystic fibrosis

RATIONALE

Although peak aerobic capacity (VO(2peak)) has been linked to outcome in patients with cystic fibrosis (CF), measuring is time consuming, and requires expensive equipment and expertise that is not readily available in all centers. Other fitness parameters such as peak anaerobic power, measures of power and strength may be simpler to deliver in the clinic. The relationship between these measures and established outcomes such as forced expiratory volume in one second (FEV(1)) and peak aerobic power (VO(2peak)) in CF remains unclear. Therefore we evaluated (a) aerobic fitness, (b) anaerobic fitness, and (c) upper and lower body muscle strength to determine their relationship to FEV(1) and VO(2peak) in children with CF.

METHODS

Eighty-two patients (7-18 years) with CF (40 female) from the CF clinic at The Hospital for Sick Children in Toronto performed a maximal incremental cycling test to exhaustion. Anaerobic power (W) for 10 and 30 sec cycling trials as well as vertical jump (VJ) and hand grip strength (HG) were compared to FEV(1) and VO(2peak).

RESULTS

Absolute VO(2peak) (R(2)  = 0.16, P < 0.001), anaerobic power (R(2)  = 0.21, P < 0.001), and hand grip strength (R(2)  = 0.10, P = 0.003) were significantly correlated to lung function whereas measures of explosive lower body strength (VJ) were not. Anaerobic power (R(2)  = 0.16, P = 0.001) and hand grip strength (R(2)  = 0.08, P = 0.01) were related to VO(2peak). Vertical jump was correlated with VO(2peak) (R(2)  = 0.29, P < 0.001) but not FEV(1).

CONCLUSIONS

Simple fitness tests such as hand grip strength and anaerobic cycle tests may be useful indicators of lung health and fitness.

Aerosolized liposomal Amphotericin B: a potential prophylaxis of invasive pulmonary aspergillosis in immunocompromised patients

BACKGROUND

Aerosolized liposomal Amphotericin B may reduce the incidence of invasive pulmonary Aspergillosis in adults with chemotherapy-induced prolonged neutropenia with less nephrotoxicity. The breath-actuated AeroEclipse® BAN nebulizer is very efficient and minimizes environmental drug contamination since no aerosol is produced, unless the patient is inspiring through the device. Our aim is to develop an appropriate delivery system suitable for children that does not disrupt the liposomes due to the shear forces in nebulization.

METHODS

This is an in vitro experimental study in vitro. Six ml of 4 mg/ml liposomal Amphotericin B solution (AmBisome®; Astellas Pharma Inc., Markham, Ontario, CA) was nebulized with the breath-actuated nebulizer (AeroEclipse®; Trudell Medical International, Canada) and captured by the glass liquid impinger. Sodium dodecyl sulfate was used as detergent to disrupt the liposomes in control samples. Gel filtration, electron microscopy, and high performance liquid chromatography (HPLC) were used to compare the size and shape of the liposomes, and amount of the drug before and after nebulization. The aerosol particle size was obtained by the laser diffraction.

RESULTS

After nebulization, 97.5% of amphotericin B was captured by the liquid impinger and detected by HPLC. Gel filtration and electron microscopy demonstrated that the drug remained in its liposomal configuration after nebulization. The mass median diameter (MMD) was 3.7 μm and 66% of aerosol particles were less than 5 μm in diameter.

CONCLUSIONS

We demonstrated that liposomal Amphotericin B can be nebulized successfully without disrupting the liposomes and minimize drug loss by using the breath-actuated nebulizer.

Efficient gene delivery to pig airway epithelia and submucosal glands using helper-dependent adenoviral vectors

Airway gene delivery is a promising strategy to treat patients with life-threatening lung diseases such as cystic fibrosis (CF). However, this strategy has to be evaluated in large animal preclinical studies in order to translate it to human applications. Because of anatomic and physiological similarities between the human and pig lungs, we utilized pig as a large animal model to examine the safety and efficiency of airway gene delivery with helper-dependent adenoviral vectors. Helper-dependent vectors carrying human CFTR or reporter gene LacZ were aerosolized intratracheally into pigs under bronchoscopic guidance. We found that the LacZ reporter and hCFTR transgene products were efficiently expressed in lung airway epithelial cells. The transgene vectors with this delivery can also reach to submucosal glands. Moreover, the hCFTR transgene protein localized to the apical membrane of both ciliated and nonciliated epithelial cells, mirroring the location of wild-type CF transmembrane conductance regulator (CFTR). Aerosol delivery procedure was well tolerated by pigs without showing systemic toxicity based on the limited number of pigs tested. These results provide important insights into developing clinical strategies for human CF lung gene therapy.Molecular Therapy-Nucleic Acids (2013) 2, e127; doi:10.1038/mtna.2013.55; published online 8 October 2013.

Respiratory system deposition with a novel aerosol delivery system in spontaneously breathing healthy adults

BACKGROUND

Intravenous magnesium sulfate (MgSO(4)) in children and adults with refractory acute asthma is effective, but therapy may be limited by systemic hypotension that might be avoided with the aerosol route. Inhaled MgSO(4) has a relatively high dose (volume) requirement. This, plus the use of inefficient delivery systems, may explain the lack of efficacy of inhaled MgSO(4) in some studies. An in vitro study suggested that the AeroNeb Go with the Idehaler Pocket and a face mask would deliver 16 mg/min of MgSO(4) to the respiratory system in older children, and approximately a fifth for toddlers, but no in vivo data exist.

METHODS

Saline mixed with a radiolabel was used as a proxy for the 100 mg/mL MgSO(4) solution. In 5 adult males the rate of deposition was measured using nuclear medicine techniques. The radiolabel deposition below the vocal cords was converted to the rate of deposition of MgSO(4) and compared to the results from an in vitro model using adult respiratory patterns.

RESULTS

The mean ± SD rate of deposition was 12.6 ± 1.9 mg/min. The reasons for this lower deposition, compared to the in vitro estimate, was most likely the exhalation of anatomical dead space aerosol, which would have been captured on the inspiratory filter in vitro.

CONCLUSIONS

These in vivo data confirm the deposition data predicted in the in vitro study, although caution should be used in extrapolating the results to children. This device appears suitable for the clinical trial of inhaled MgSO(4) in children and adults with refractory asthma.

Modeling breath-enhanced jet nebulizers to estimate pulmonary drug deposition

BACKGROUND

Predictable delivery of aerosol medication for a given patient and drug-device combination is crucial, both for therapeutic effect and to avoid toxicity. The gold standard for measuring pulmonary drug deposition (PDD) is gamma scintigraphy. However, these techniques expose patients to radiation, are complicated, and are relevant for only one patient and drug-device combination, making them less available. Alternatively, in vitro experiments have been used as a surrogate to estimate in vivo performance, but this is time-consuming and has few "in vitro to in vivo" correlations for therapeutics delivered by inhalation. An alternative method for determining inhaled mass and PDD is proposed by deriving and validating a mathematical model, for the individual breathing patterns of normal subjects and drug-device operating parameters. This model was evaluated for patients with cystic fibrosis (CF).

METHODS

This study is comprised of three stages: mathematical model derivation, in vitro testing, and in vivo validation. The model was derived from an idealized patient's respiration cycle and the steady-state operating characteristics of a drug-device combination. The model was tested under in vitro dynamic conditions that varied tidal volume, inspiration-to-expiration time, and breaths per minute. This approach was then extended to incorporate additional physiological parameters (dead space, aerodynamic particle size distribution) and validated against in vivo nuclear medicine data in predicting PDD in both normal subjects and those with CF.

RESULTS

The model shows strong agreement with in vitro testing. In vivo testing with normal subjects yielded good agreement, but less agreement for patients with chronic obstructive lung disease and bronchiectasis from CF.

CONCLUSIONS

The mathematical model was successful in accommodating a wide range of breathing patterns and drug-device combinations. Furthermore, the model has demonstrated its effectiveness in predicting the amount of aerosol delivered to "normal" subjects. However, challenges remain in predicting deposition in obstructive lung disease.

Higher tobramycin concentration and vibrating mesh technology can shorten antibiotic treatment time in cystic fibrosis

Poor adherence to recommended therapy in cystic fibrosis (CF) is often because of the time demands of therapy. Tobramycin (TOBI®, 300 mg at 60 mg/ml) inhaled from the PARI LC PLUS® nebulizer requires about 20 min. This study determined if equivalent levels of pulmonary deposition could be achieved in shorter time using 1.5 ml of 100 mg/ml tobramycin solution delivered by an investigational eFlow® nebulizer. Sixteen males with stable CF, 8 children and 8 adults, and an FEV(1)  > 45% predicted inhaled both preparations on two occasions with (99m) Tc-DTPA added to the tobramycin. Blood samples were taken for quantification of tobramycin in the serum. The PARI LC PLUS® delivered 45.4 (39.3-51.6), mean and 95% CI, mg to the lungs in 17.0 ± 2.5 min (mean ± SD) with serum levels of 1,089 ± 388 µg/L. The investigational eFlow® delivered 46.3(40.3-51.7) mg in 4.0 ± 1.0 min with blood levels of 909 ± 458 µg/L. Only the time of delivery was significantly different with P < 0.0001 (paired t-test). Tolerability of the treatment was comparable for both inhalation regimes, but the shorter treatment was preferred by all patients. These results demonstrate the possibility of delivering equivalent levels of tobramycin much faster into the lungs of CF patients when using eFlow®, a very efficient electronic nebulizer.

A comparison of amount and speed of deposition between the PARI LC STAR® jet nebulizer and an investigational eFlow® nebulizer

BACKGROUND

The potency and physical properties of many of the drugs used in the treatment of cystic fibrosis necessitates the use of nebulization, a relatively time-consuming pulmonary delivery method. Newer, faster, and more efficient delivery systems are being proposed. The purposes of this study was to compare the length of time it took to deliver the equivalent of normal saline nebulized for 10 min in a PARI LC STAR(®) nebulizer to that of an investigational PARI eFlow(®).

METHODS

Six normal adults inhaled a 4-mL (36-mg) charge volume of saline from the LC STAR(®) or a 2.5-mL (22.5-mg) charge volume from the investigational eFlow(®). The saline was mixed with (99m)Tc-DTPA to allow two-dimensional imaging. The inhalation was preceded by a xenon equilibration scan to allow more accurate separation of deposition into central and peripheral lung regions.

RESULTS

The investigational eFlow(®) delivered 8.6 ± 1.0 mg, approximately 90% of the lung dose compared to the LC STAR(®), 9.6 ± 1.0 mg, but did in less than half the time (p < 0.02 for both). There were no differences in central versus peripheral distribution for either device.

CONCLUSIONS

In conclusion the investigational eFlow(®) was both faster and more efficient than the LC STAR(®).

Skeletal muscle metabolism in cystic fibrosis and primary ciliary dyskinesia

Previous studies have reported differences in muscle function and metabolism between patients with cystic fibrosis (CF) and healthy controls (HC), but it is currently unknown whether these abnormalities are specific to CF or also seen in other airway diseases. In this study, we used magnetic resonance spectroscopy (MRS) during exercise to assess muscle metabolism in CF patients. Twenty patients with CF and 20 age, gender, and habitual activity-matched HCs and a respiratory disease comparison group with primary ciliary dyskinesia (PCD; n = 10) were studied. Phosphorus MRS (P-MRS) was used to characterize muscle bioenergetic metabolism at rest and after high-, moderate-, and low-intensity exercise. CF patients exhibited lower resting ATP/phosphocreatine (PCr) ratio and significantly higher end-exercise pH values compared with both HC and PCD patients. Both CF and PCD patients demonstrated significantly slower PCr recovery time constants after high-intensity exercise. Our results suggest that not only there are specific abnormalities of muscle metabolism in CF patients but also there is a nonspecific impact of respiratory disease on muscle function.

Testing of nebulizers for delivering magnesium sulfate to pediatric asthma patients in the emergency department

BACKGROUND

As the use of intravenous magnesium sulfate (MgSO(4)) for the treatment of refractory asthma is becoming more common, the incidence of MgSO(4)-related systemic hypotension is also rising. One option is to deliver MgSO(4) via aerosol, but compared to most inhaled medications, which are active in the microgram dose range, the MgSO(4) dose requirement is in the milligram range. This, along with inefficient aerosol delivery systems, may be the reason that some studies have found lack of efficacy with aerosol MgSO(4). In preparation for a multicenter study of inhaled MgSO(4) in asthmatic children 2-17 years old, we conducted an in vitro study to choose the best MgSO(4) nebulizer system that would be effective over the entire age range.

METHODS

We tested the Pari LC Star jet nebulizer, Omron MicroAir vibrating-mesh nebulizer, and the Aeroneb Go vibrating-mesh nebulizer with the Idehaler valve-less holding chamber. Aerosol delivery was via face mask.

RESULTS

The Pari LC Star had an appropriate particle size distribution but a very slow aerosol output rate. The Omron MicroAir had an even slower output rate and a larger particle size distribution, which would be inappropriate for smaller children. In vitro lung deposition with the Aeroneb Go with Idehaler was 16.0 ± 0.4 mg/min in older children and approximately a fifth of that in toddlers.

CONCLUSIONS

The Aeroneb Go with Idehaler was chosen for the multicenter clinical study.

Exercise capacity of children with pediatric lung disease

BACKGROUND

Pulmonary function of children with cystic fibrosis (CF) and bronchopulmonary dysplasia (BPD) is similar at rest even though the mechanisms of injury differ. We sought to compare the peak exercise responses in children with BPD versus CF while controlling for pulmonary impairment, nutritional status, gender, age, height, and predicted forced expired volume in 1 second (approximately 73% of predicted).

METHODS

Nine BPD children and 9 CF children underwent spirometry and a progressive exercise test to maximum on a cycle ergometer.

RESULTS

There was no difference between groups in body mass percentile (CF:97 +/- 13%, BPD: 98 +/- 11%), peak power output (Wpeak) (CF:67 +/- 19 W, BPD:73 +/- 28 W), % predicted Wpeak (CF:83 +/- 28%, BPD:88 +/- 15%), peak oxygen uptake (VO2peak, CF: 38 +/- 7 ml/kg/min, BPD: 39 +/-6 ml/kg/min), or % predicted VO2peak (CF:99 +/- 16 %, BPD:96 +/- 27%).

CONCLUSIONS

Children with mild pulmonary impairments are able to achieve a near normal peak power output and a normal VO2peak. Neither the aetiology nor the developmental onset of the process appears to be important influences on VO2peak or Wpeak.

Transmission of influenza virus via aerosols and fomites in the guinea pig model

Limited data on the relative contributions of different routes of transmission for influenza virus are available. Person-to-person transmission is central to seasonal and pandemic spread; nevertheless, the modes of spread are a matter of ongoing debate. Resolution of this discussion is paramount to the development of effective control measures in health care and community settings. Using the guinea pig model, we demonstrated that transmission of influenza A/Panama/2007/1999 (H3N2) virus through the air is efficient, compared with spread through contaminated environmental surfaces (fomites). We also examined the aerosol transmission efficiencies of 2 human influenza virus A strains and found that A/Panama/2007/1999 influenza virus transmitted more efficiently than A/Texas/36/1991 (H1N1) virus in our model. The data provide new and much-needed insights into the modes of influenza virus spread and strain-specific differences in the efficiency of transmission

Age- and size-related reference ranges: a case study of spirometry through childhood and adulthood

Age-related reference ranges are useful for assessing growth in children. The LMS method is a popular technique for constructing growth charts that model the age-changing distribution of the measurement in terms of the median, coefficient of variation and skewness. Here the methodology is extended to references that depend on body size as well as age, by exploiting the flexibility of the generalised additive models for location, scale and shape (GAMLSS) technique. GAMLSS offers general linear predictors for each moment parameter and a choice of error distributions, which can handle kurtosis as well as skewness. A key question with such references is the nature of the age-size adjustment, additive or multiplicative, which is explored by comparing the identity link and log link for the median predictor.There are several measurements whose reference ranges depend on both body size and age. As an example, models are developed here for the first four moments of the lung function variables forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC) and FEV(1)/FVC in terms of height and age, in a data set of 3598 children and adults aged 4 to 80 years. The results show a strong multiplicative association between spirometry, height and age, with a large and nonlinear age effect across the age range. Variability also depends nonlinearly on age and to a lesser extent on height. FEV(1) and FVC are close to normally distributed, while FEV(1)/FVC is appreciably skew to the left. GAMLSS is a powerful technique for the construction of such references, which should be useful in clinical medicine.

Assessment of body composition in pediatric patients with cystic fibrosis

RATIONALE

Cystic fibrosis (CF) leads to pathological changes in organs that express the cystic fibrosis transmembrane conductance regulator (CFTR), including secretory cells of the digestive tract and the pancreas. Maintaining nutritional sufficiency is challenging for CF patients and therefore accurate monitoring is important for their clinical management.

PURPOSE

The objectives of this study were to evaluate the effectiveness of skinfold measurements as an accurate method for determining body composition (fat mass (FM) and lean body mass (LBM)) of this population, using dual-energy X-ray absorptiometry (DEXA) as a gold standard comparison and to determine the most accurate equation for this calculation in children with CF.

METHODS

Fifty-five pediatric patients with CF participated in the study. FM and LBM calculated via four methods: Slaughter, Durnin, Durenberg (2-site and 4-site). The relationship between the methods and DEXA results were estimated by intraclass-correlation coefficient (ICC) and Bland and Altman analyses.

RESULTS

The Slaughter method was the most accurate (ICC of 0.92 for FM and 0.99 for LBM) and displayed the least bias over the range of FM and LBM in CF patients. In addition, the results of Bland Altman analyses comparing each skinfold method to DEXA, revealed that the results were evenly distributed along the range of values for the Slaughter calculation, whereas the other three methods under and over estimated % fat results at the upper and lower ends of the range respectively.

CONCLUSION

We therefore conclude that the Slaughter method may be used for body composition assessment of pediatric CF patients. This provides clinical teams with a simple, accurate and non-invasive method that can be used to monitor nutritional status in pediatric patients with CF.

A single versus multiple doses of dexamethasone in infants wheezing for the first time

RATIONALE

Corticosteroid therapy is not routinely recommended in true bronchiolitis. However, since bronchiolitis and the first asthma attack are impossible to distinguish, some infants with the first wheezing episode receive corticosteroids. Optimal duration of corticosteroid therapy in this scenario is unknown. This study compared efficacy of multiple administrations and a single dose of dexamethasone in bronchiolitis.

METHODS

In this randomized double blind trial, previously healthy outpatients 2-23 months of age with bronchiolitis and Respiratory Disease Assessment Instrument (RDAI) score 6 or more received 1 mg/kg of oral dexamethasone in the Emergency Department. Prior to discharge at 4 hr they were randomized to either 4 daily doses of dexamethasone 0.15 mg/kg or placebo equivalent. Primary outcome was the proportion of subsequent hospitalizations or prescribed trials of bronchodilator/corticosteroid therapy for dyspnea by day 6 in the groups. Secondary outcomes were changes in the RDAI to day 6, and proportions with unscheduled visits by days 6 and 28.

RESULTS

The rate of primary outcome in the single dose group (SDG, N = 64) was 9/64 or 14.1% versus 7/61 or 11.5% in the multiple dose group (MDG, N = 61) [95% CI 0.09; 0.14]. Twelve (18.8%) children in the SDG had unscheduled medical visits by day 6 versus 11 (18.0%) children in the MDG [95% CI 0.13; 0.14]. On day 6 the RDAI decreased from 9.5 +/- 2.1 to 2.1 +/- 2.4 in the SDG and from 9.8 +/- 2.2 to 1.6 +/- 2.3 in the MDG [95% CI 0.36; 2.06]. Between days 7-28, 24/64 (37.5%) SDG infants returned for care versus 20/61 (32.8%) of the MDG [95% CI 0.12; 0.21].

CONCLUSIONS

Our study suggests that, in outpatients with bronchiolitis who receive dexamethasone, continuation of this agent beyond the initial dose does not provide significant benefit.

Rapid pulmonary delivery of inhaled tobramycin for Pseudomonas infection in cystic fibrosis: a pilot project

BACKGROUND

Patients with cystic fibrosis spend as much 30 min a day inhaling tobramycin. Could a new rapid system deposit the equivalent amount of tobramycin faster?

METHODS

Six healthy adult males inhaled 5 ml (300 mg) of tobramycin from a breath enhanced nebulizer and either 125 mg (n = 3) or 150 mg (n = 3) from a vibrating membrane system with a large or small aerosol mixing chamber respectively. A radiolabel was added to the solution and shown to "track" with the tobramycin. Imaging was done with a dual headed gamma camera. Because the radiolabel will be cleared by mucociliary action during administration, algorithms were developed to allow the comparison of a slower system to a faster one.

RESULTS

Both formulations were well tolerated. The lung deposition was 16.6 +/- 3.2% (mean +/- SD) of the charge dose delivered in 10.9 +/- 1.0 min for the breath enhanced nebulizer versus 32.0 +/- 5.1% delivered in 2.5 +/- 0.4 min from the vibrating membrane system. The absolute pulmonary delivery of tobramycin was 49.9 +/- 9.6 versus 43.9 +/- 4.8 mg for the two systems respectively, differences that were statistically significant (pair t-test) but unlikely to be clinically significant. There was a similar deposition of tobramycin for the 125 and 150 mg dose.

CONCLUSIONS

It is possible to deliver an equivalent amount of tobramycin in a shorter period of time with the new vibrating membrane system and a more concentrated formulation. These data will allow the design of a comparison in patients with CF.

Reliability and validity of the habitual activity estimation scale (HAES) in patients with cystic fibrosis

PURPOSE

To understand potential benefits of exercise in the cystic fibrosis (CF) population, there needs to be accurate methods to quantify it. The Habitual Activity Estimation Scale (HAES) questionnaire has been shown to be a feasible tool to measure physical activity however the reliability and validity have yet to be determined in the CF population.

METHODS

Fourteen (seven male, seven female) patients aged 16.2 +/- 4.2 years with CF participated in this study. Participants were clinically stable at the time of the study and participating in their habitual physical activity. To assess reliability, patients completed the HAES and a validated 3-day activity diary, and wore an ActiGraph Accelerometer for two consecutive weeks. Validity was assessed by comparing the activity results of each of the three instruments over a single week time period.

RESULTS

ICC estimates of reliability for the HAES, diary, and accelerometer were 0.72 (P < 0.0001), 0.76 (P < 0.0001), 0.63 (P < 0.0001), respectively. Validity analysis indicated that there were significant relationships between the participants' activity results as estimated by the HAES, diary and accelerometer. Further, significant relationships were detected between activity measures when broken into morning, afternoon, or evening periods, and between measures from weekday or weekend days. There were also significant relationships among the three instruments when recording different activity levels (somewhat inactive, somewhat active, and very active).

CONCLUSION

The findings of this study suggest that the HAES questionnaire is a reliable and valid instrument that can be used to assess activities of varying intensity in patients with CF.

Reference ranges for spirometry across all ages: a new approach

RATIONALE

The Third National Health and Nutrition Examination Survey (NHANES III) reference is currently recommended for interpreting spirometry results, but it is limited by the lack of subjects younger than 8 years and does not continuously model spirometry across all ages.

OBJECTIVES

By collating pediatric data from other large-population surveys, we have investigated ways of developing reference ranges that more accurately describe the relationship between spirometric lung function and height and age within the pediatric age range, and allow a seamless transition to adulthood.

METHODS

Data were obtained from four surveys and included 3,598 subjects aged 4-80 years. The original analyses were sex specific and limited to non-Hispanic white subjects. An extension of the LMS (lambda, mu, sigma) method, widely used to construct growth reference charts, was applied.

MEASUREMENTS AND MAIN RESULTS

The extended models have four important advantages over the original NHANES III analysis as follows: (1) they extend the reference data down to 4 years of age, (2) they incorporate the relationship between height and age in a way that is biologically plausible, (3) they provide smoothly changing curves to describe the transition between childhood and adulthood, and (4) they highlight the fact that the range of normal values is highly dependent on age.

CONCLUSIONS

The modeling technique provides an elegant solution to a complex and longstanding problem. Furthermore, it provides a biologically plausible and statistically robust means of developing continuous reference ranges from early childhood to old age. These dynamic models provide a platform from which future studies can be developed to continue to improve the accuracy of reference data for pulmonary function tests.

The Challenges of Quantitative Measurement of Lung Deposition Using 99mTc-DTPA from Delivery Systems with Very Different Delivery Times

In quantifying aerosol delivery, the drug is often mixed with a radiolabel such as (99m)Tc-DTPA whose deposition is used as a proxy for the drug. (99m)Tc-DTPA deposited in the lung is cleared by a combination of absorption into the pulmonary circulation and mucociliary clearance. If administration is not instantaneous, the image will not include that clearance during administration, a problem raised if comparing devices with different administration times. However, if rates of clearance are measured, it will be possible to "correct" the initial image for the clearance that occurred during administration and before counting. Five adult males inhaled a 5-mL solution containing (99m)Tc-DTPA from a breath enhanced jet nebulizer (LC Plus)over the course of 10 min and a 1.25-mL solution from a vibrating membrane device (eFlow), which was delivered in 2.5 min. Quality assurance was the radioactivity count balance (RCB) defined as the difference in the total radioactivity pre-nebulization less post, divided by pre, and expressed as a percentage. Attenuation calculations used a (57)Co flood source (Macey and Marshall). The "correction" for the clearance of (99m)Tc-DTPA was 0.91 +/- 0.04 (mean +/- SD) for the LC Plus) and 0.96 +/- 0.02 for the eFlow). RCB was -0.6 +/- 3.5% for the LC Plus and -4.7 +/- 6.4% for the eFlow, implying acceptable accuracy. For the LC Plus, lung deposition was 15.9(13.4, 18.4)% (mean and 95% CI) of the charge dose, and for the eFlow it was 32.0(29.0, 35.0)%. This technique gave an acceptable level of accuracy for quantitative planar imaging and allowed the comparison of delivery from devices with very different rates of delivery.

Calculating expected lung deposition of aerosolized administration of AAV vector in human clinical studies

BACKGROUND

Cystic fibrosis is an autosomal recessive disease affecting approximately 1 in 2500 live births. Introducing the cDNA that codes for normal cystic fibrosis transmembrane conductance regulator (CFTR) to the small airways of the lung could result in restoring the CFTR function. A number of vectors for lung gene therapy have been tried and adeno-associated virus (AAV) vectors offer promise. The vector is delivered to the lung using a breath-actuated jet nebulizer. The purpose of this project was to determine the aerosolized AAV (tgAAVCF) particle size distribution (PSD) in order to calculate target doses for lung delivery.

METHODS

A tgAAVCF solution was nebulized using the Pari LC Plus (n = 3), and the PSD was determined by coupling laser diffraction and inertial impaction (NGI) techniques. The NGI allowed for quantification of the tgAAVCF at each stage of impaction, ensuring that rAAV-CFTR vector is present and not empty particles. Applying the results to mathematical algorithms allowed for the calculation of expected pulmonary deposition.

RESULTS

The mass median diameter (MMD) for the tgAAVCF was 2.78 +/- 0.43 microm. If the system works ideally and the patient only receives aerosol on inspiration, the patient would receive 47 +/- 0% of the initial dose placed in the nebulizer, with 72 +/- 0.73% of this being deposited beyond the vocal cords.

CONCLUSIONS

This technology for categorizing the pulmonary delivery system for lung gene therapy vectors can be adapted for advanced aerosol delivery systems or other vectors.

High-dose inhaled fluticasone does not replace oral prednisolone in children with mild to moderate acute asthma

BACKGROUND

Inhaled corticosteroids are not as effective as oral corticosteroids in school-aged children with severe acute asthma. It is uncertain how inhaled corticosteroids compare with oral corticosteroids in mild to moderate exacerbations.

PRIMARY OBJECTIVE

The purpose of this work was to determine whether there is a significant difference in the percentage of predicted forced expiratory volume in 1 second in children with mild to moderate acute asthma treated with either inhaled fluticasone or oral prednisolone.

METHODS

This was a randomized, double-blind controlled trial conducted between 2001 and 2004 in a tertiary care pediatric emergency department. We studied a convenience sample of 69 previously healthy children 5 to 17 years of age with acute asthma and forced expiratory volume in 1 second at 50% to 79% predicted value; 41 families refused participation. Albuterol was given in the emergency department and salmeterol was given after discharge to all patients, as well as either 2 mg of fluticasone via metered dose inhaler and valved holding chamber in the emergency department plus 500 microg twice daily via Diskus for 10 doses after discharge (fluticasone group, N = 35) or 2 mg/kg of oral prednisolone in the emergency department plus 5 daily doses of 1 mg/kg of prednisolone after discharge (prednisolone group, N = 34). We measured a priori defined absolute change in percent predicted forced expiratory volume in 1 second from baseline to 4 and 48 hours in the 2 groups. RESULTS. At 240 minutes, the forced expiratory volume in 1 second increased by 19.1% +/- 12.7% in the fluticasone group and 29.8% +/- 15.5% in the prednisolone group. At 48 hours, this difference was no longer significant (estimated difference: 4.0 +/- 3.4; P = .14). The relapse rates by 48 hours were 12.5% and 0% in the fluticasone group and prednisolone group, respectively.

CONCLUSION

Airway obstruction in children with mild to moderate acute asthma in the emergency department improves faster on oral than inhaled corticosteroids.

Nebulized therapies for childhood pulmonary hypertension: an in vitro model

OBJECTIVES

Sildenafil, tezosentan, and prostacyclin reduce pulmonary vascular pressures in pulmonary hypertension, but have potential to vasodilate the systemic circulation. Nebulized vasodilators allow targeted drug delivery, high local drug concentrations, less systemic hypotension, and better matching of the lung's ventilation and perfusion. We aimed to estimate pulmonary deposition of these drugs from commonly employed nebulizers using in vitro techniques and to create a mathematical model to predict inspired mass of aerosol.

DESIGN

Lung deposition was estimated by characterization of drug output and particle size distribution (PSD) of nebulizers using helium-neon laser diffraction techniques. A mathematical model for each device was created to estimate pulmonary deposition using patients' breathing patterns and was verified with a mechanical-breathing model.

RESULTS

Total output and PSD were similar for the Hudson Updraft II and Whisperjet nebulizers, consisting of half the nebulizer's charge, with (1/4) of particles < or = 5 microm, in the respirable fraction (RF). Drug output increased with inspiratory flow for the Pari LC Star. Differences were noted in device performance, depending on the drug tested. Estimated pulmonary deposition (mean, 95% CI) was 8.1 (7.2, 9.0)% of the initial drug charge for the Hudson Updraft II, 6.4 (5.8, 7.0)% for the Whisperjet, and 33.0 (28.3, 37.9)% for the Pari LC Star. A mechanical model was consistent with our mathematical model.

CONCLUSIONS

All drugs could be nebulized, but expected pulmonary deposition varied depending on the nebulizer and drug.

Resting and exercise cardiorespiratory function in survivors of congenital diaphragmatic hernia

Our objective was to study exercise capacity and cardiorespiratory response to exertion in survivors of congenital diaphragmatic hernia (CDH). This was a cross-sectional cohort study of 23 CDH survivors, aged 10-16 years, and 23 gender- and age-matched controls. Exercise testing was performed on a cycle ergometer, with cardiac output measurements made using exponential CO2 rebreathing. Pretest cardiorespiratory assessment was done by echocardiography and pulmonary function testing. Statistical analysis was performed using Student's t-test, regression analysis, and longitudinal model computing with spatial covariance structure. No echocardiographic evidence for pulmonary hypertension was found at rest (right ventricular systolic pressures, 27 +/- 6 mmHg). Mean pulmonary artery diameter on the side of the CDH was significantly smaller than contralaterally, but was within normal range (z-score, 0 +/- 1.1 vs. 1.2 +/- 1.6, P < 0.01). Exercise capacity was mildly reduced in CDH compared to controls and predictive data (maximum workload, 77% +/- 12% vs. 91% +/- 16% of predicted, P < 0.01). Cardiorespiratory response to exertion was not significantly different between groups. In conclusion, most adolescent CDH survivors have nearly normal exercise capacity and cardiorespiratory response to exertion. This study may prove useful in comparisons with future cohorts comprising more severely affected individuals now surviving due to improved neonatal care.

Comparison of Three Valved Holding Chambers for the Delivery of Fluticasone Propionate–HFA to an Infant Face Model

The purpose of this study was to compare three valved holding chambers (VHC) with facemasks attached. One VHC (AeroChamber Max[TM] with medium mask) was made with materials that dissipate surface electrostatic charge, and the others (OptiChamber Advantage and ProChamber[TM] with pediatric facemask) were made from non-conducting materials. The OptiChamber Advantage and ProChamber VHCs were each washed with an ionic detergent and drip dried before testing to minimize surface electrostatic charge. The AeroChamber Max VHCs were tested "out of the package" and also after wash, rinse, and drying. An infant face model incorporating an electrostatic filter in the oral cavity was connected to a breath simulator using a standard waveform for a small child. The fit of each VHC with facemask was demonstrated by agreement of inspiratory flow measurements between a pneumotachograph connected to the system with those set on the simulator. An HFA-fluticasone propionate metered dose inhaler (MDI; 125 microg/dose) was inserted into the VHC, two actuations were delivered, and the filters were subsequently assayed using high-pressure liquid chromatography (HPLC). Testing and sample assay order was randomized, and HPLC assays were undertaken blinded. Drug delivery efficiency expressed as a percentage of the total dose of fluticasone propionate (250 microg) for the AeroChamber Max VHC "out-of-the-package" was 22.0(0.7)% (mean [99% CI]) and 21.2(1.5)% when pre-washed/rinsed. Results for the pre-washed ProChamber and OptiChamber Advantage VHCs were 10.2(0.55)% and 8.8(1.9)%, respectively. The more efficient delivery of medication via VHCs made from electrostatic charge dissipative materials should be considered when choosing doses for small children.

The price of success in the management of congenital diaphragmatic hernia: is improved survival accompanied by an increase in long-term morbidity?

BACKGROUND

The impact of "gentle ventilation" (GV) strategies on morbidity and mortality of patients with congenital diaphragmatic hernia (CDH) in our institution has not been determined. This study reviews the primary and secondary outcomes of our patients with CDH treated with the GV approach.

METHOD

We performed a retrospective chart review of respiratory, neurologic, nutritional, and musculoskeletal morbidities in patients with CDH treated at a single institution between 1985 and 1989 with conventional ventilation (CV) compared with those treated from 1996 to 2000 with GV.

RESULTS

There were 77 CV-treated and 66 GV-treated patients with CDH, with 51% survival in the CV cohort compared with 80% in the GV group (chi(2), P < .05). At 3-year follow-up, we found no statistically significant differences in the frequency of respiratory (38% of CV patients, 50% of GV patients), neurologic (29% of CV patients, 34% of GV patients), or musculoskeletal morbidity (46% of CV vs 29% of GV-treated patients). There was a difference in nutritional morbidity as indicated by the increased frequency of gastrostomy tube use in the GV-treated patients (34%) compared with the CV patients (8%; chi2, P < .05).

CONCLUSION

The implementation of GV techniques has significantly decreased mortality in infants with CDH. This has been associated with a documented increase in nutritional morbidity among survivors.

Controlled delivery of high vs low humidity vs mist therapy for croup in emergency departments: a randomized controlled trial

CONTEXT

Children with croup are often treated with humidity even though this is not scientifically based, consumes time, and can be harmful. Although humidity using the traditional blow-by technique is similar to room air and no water droplets reach the nasopharynx, particles sized for laryngeal deposition (5-10 microm) could be beneficial.

OBJECTIVE

To determine whether a significant difference in the clinical Westley croup score exists in children with moderate to severe croup who were admitted to the emergency department and who received either 100% humidity or 40% humidity via nebulizer or blow-by humidity.

DESIGN AND SETTING

A randomized, single-blind, controlled trial conducted between 2001 and 2004 in a tertiary care pediatric emergency department.

PARTICIPANTS

A convenience sample of 140 previously healthy children 3 months to 10 years of age with Westley croup score of more than 1 or 2 or higher (scoring system range, 0-17); 21 families refused participation.

INTERVENTION

Thirty-minute administration of humidity using traditional blow-by technique (commonly used placebo, n = 48), controlled delivery of 40% humidity (optimally delivered placebo, n = 46), or 100% humidity (n = 46) with water particles of mass median diameter 6.21 microm.

MAIN OUTCOME MEASURE

A priori defined change in the Westley croup score from baseline to 30 and 60 minutes in the 3 groups.

RESULTS

Groups were comparable before treatment. At 30 minutes the difference in the improvement in the croup score between the blow-by and low-humidity groups was 0.03 (95% confidence interval [CI], -0.72 to 0.66), between low- and high-humidity groups, 0.16 (95% CI, -0.86 to 0.53), and between blow-by and high-humidity groups, 0.19 (95% CI, -0.87 to 0.49). Results were similar at 60 minutes. Differences between groups in pulse and respiratory rates and oxygen saturation changes were insignificant, as were proportions of excellent responders; proportions with croup score of 0 at study conclusion; and proportions receiving dexamethasone, epinephrine, or requiring additional medical care or hospitalization.

CONCLUSIONS

One hundred percent humidity with particles specifically sized to deposit in the larynx failed to result in greater improvement than 40% humidity or humidity by blow-by technique. This study does not support the use of humidity for moderate croup for patients treated in the emergency department.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00230841.

How many infective viral particles are necessary for successful mass measles immunization by aerosol?

OBJECTIVES

This study characterized the performance of the "Classical Mexican Device", which immunized 4 million children against measles, demonstrating the efficacy of aerosol vaccination.

METHODS

Using plaque-forming units to quantify virus, the particle size distribution (Next Generation Pharmaceutical Impactor) and rate of output coupled with age specific patterns of breathing allowed the calculation of expected pulmonary deposition.

RESULTS

The estimated immunization dose for infants was 30 pfu's, for small children 50, and for older children and adolescents it was 130 and 225, respectively.

CONCLUSIONS

These performance characteristics can be used to develop newer battery operable devices that are licensable.