Sex-dependent regulation of mucin gene transcription and airway secretion and mechanics following intra-airway IL-13 in mice with conditional loss of club cell Creb1.

Introduction: Interleukin 13 (IL-13) is an important effector molecule in allergic asthma. IL-13-mediated mucin hypersecretion requires conversion of secretoglobin-positive club cells into goblet cells through suppression of forkhead box A2 (FOXA2) and induction of SAM pointed domain containing ETS transcription factor (SPDEF). IL-13-mediated mucin hypersecretion may also include modulation of purinergic and muscarinic receptors that control basal and stimulated mucin secretion. We recently found that the transcription factor cAMP response element-binding protein (Creb1) inhibits FOXA2 and modulates mucus secretion in mice. Methods: We tested the hypothesis that loss of club cell Creb1 mitigates the pro-mucin effects of IL-13. We challenged male and female mice with conditional loss of club cell Creb1 and wild type littermates with intra-airway IL-13 or vehicle. We also studied human "club cell-like" NCI-H322 cells. Results: Loss of club cell Creb1 augmented IL-13-mediated increases in mRNA for the gel-forming mucins Muc5ac and Muc5b and prevented IL-13-mediated decreases in muscarinic 3 receptor (M3R) mRNA in male airways. In female airways, loss of club cell Creb1 reduced M3R mRNA and significantly blunted IL-13-mediated increases in purinergic receptor P2Y2 (P2ry2) mRNA but did not impact Muc5ac and Muc5b mRNA. Despite changes in mucins and secretion machinery, goblet cell density following cholinergic stimulation was not impacted by loss of club cell Creb1 in either sex. IL-13 treatment decreased basal airway resistance across sexes in mice with loss of club cell Creb1, whereas loss of club cell Creb1 augmented IL-13-mediated increases in airway elastance in response to methacholine. NCI-H322 cells displayed IL-13 signaling components, including IL-13Rα1 and IL-4Rα. Pharmacologic inhibition of CREB reduced IL-13Rα1 mRNA, whereas recombinant CREB decreased IL-4Rα mRNA. Application of IL-13 to NCI-H322 cells increased concentrations of cAMP in a delayed manner, thus linking IL-13 signaling to CREB signaling. Conclusion: These data highlight sex-specific regulation of club cell Creb1 on IL-13-mediated mucin hypersecretion and airway mechanics.

Determining Adherence to Inhaled Corticosteroids From the Epic Electronic Medical Record.

OBJECTIVE: Often we call the patient's pharmacy to obtain a refill history to assess inhaled corticosteroid (ICS) adherence. The purpose of this project was to determine the accuracy of refill histories for ICS (with or without long-acting beta agonist) listed in Epic's Medication Dispense History. METHODS: We evaluated 61 patients and used data from 38 who met the following criteria: 1) under the care of the UF Pediatric Severe Asthma Clinic; 2) taking the same dose of the same ICS product for 6 months before the patient's last clinic visit; and 3) having data available from the pharmacy where the last ICS prescription was electronically sent. We called the pharmacies to obtain a verbal report of their refill record. Then, we compared the number of refills reported to the number listed in Epic's records using a Wilcoxon matched-pairs signed-ranks test. RESULTS: Of the 293 refill dates listed in Epic, 157 were duplicates, giving a 54% error. After deleting duplicates, the mean (SD) number of refills listed in Epic was 3.6 (2.0) compared with 3.3 (2.0) in pharmacies over a period of 6 months (p < 0.0001). After removing duplicates Epic correctly reported the total number of refills for 30 of the 38 patients (78.9%). Seven of the remaining patients had more refills listed in Epic while 1 patient had more refills dispensed. CONCLUSION: This study indicates that our version of Epic over-reports refills thus limiting assessment of adherence. In contrast, absence of refills in Epic is a clear indication of poor adherence.

Exploring Caregiver Interest in and Preferences for Interventions for Children With Risk of Asthma Exacerbation: Web-Based Survey.

BACKGROUND: Maintaining control of asthma symptoms is the cornerstone of asthma treatment guidelines in the United States. However, suboptimal asthma control and asthma exacerbations among young people are common and are associated with many negative outcomes. Interventions to improve asthma control are needed. For such interventions to be successful, it is necessary to understand the types of interventions that are appealing to caregivers of children with different levels of risk of exacerbation. OBJECTIVE: This study aimed to evaluate whether caregivers of children with high (vs low) risk of asthma exacerbation show different levels of interest in and preferences for potential intervention programs and delivery methods. METHODS: We contracted with Ipsos to administer a web-based survey to caregivers of children with asthma who were residing in the United States. Caregivers (N=394) reported their interest (1=not at all; 3=a lot) in 9 possible intervention programs and 8 possible intervention delivery methods. Caregivers also indicated their preferences by selecting the 3 intervention programs and 3 delivery methods that "most" interested them. Finally, caregivers completed 2 open-ended questions asking what other resources might be useful for managing their children's asthma. We classified children as having a high risk of exacerbation if they had an exacerbation in the past 3 months (n=116) and a low risk of exacerbation if otherwise (n=278). RESULTS: Caregivers reported higher levels of interest in all intervention programs and delivery methods if they cared for a child with a high risk rather than a low risk of exacerbation. However, regardless of the child's risk status, caregivers expressed the highest levels of interest in programs to increase their child's self-management skills, to help pay for asthma care, and to work with the school to manage asthma. Caregivers expressed the highest levels of interest in delivery methods that maintained personal control over accessing information (websites, videos, printed materials, and smartphone apps). Caregivers' preferences were consistent with their interests; programs and delivery methods that were rated as high in interest were also selected as one of the 3 that "most" interested them. Although most caregivers did not provide additional suggestions for the open-ended questions, a few caregivers suggested intervention programs and delivery methods that we had not included (eg, education about avoiding triggers and medication reminders). CONCLUSIONS: Similar interests and preferences among caregivers of children with high and low risk of exacerbation suggest a broad need for support in managing childhood asthma. Providers could help caregivers by directing them toward resources that make asthma care more affordable and by helping their children with asthma self-management. Interventions that accommodate caregivers' concerns about having personal control over access to asthma information are likely to be more successful than interventions that do not.

Psychometric properties and predictive validity of the PP-ACT.

OBJECTIVE: The Parent Proxy Asthma Control Test (PP-ACT) is a self-report measure of asthma control completed by caregivers on behalf of a child. We examined the psychometric properties and the reliability and predictive validity of the PP-ACT. METHODS: We conducted two studies (one cross-sectional, one longitudinal over three months) that surveyed caregivers (N = 1622) of children with asthma. Caregivers completed the PP-ACT and a variety of other measures, including child health outcomes. RESULTS: We found clear evidence that the five-item PP-ACT assesses two distinct constructs: Items 1-4 (which we call the PP-ACT4) assess symptoms, impairment, and use of a short acting beta-2 blocker (albuterol); Item 5 assesses caregivers' global subjective assessment of their child's asthma control. In addition, the two constructs function as unique predictors of asthma outcomes. Both the PP-ACT4 and Item 5 predicted unique variance in ED visits, the number of symptom-free days, and child quality of life. Only the PP-ACT4 predicted frequency of ICS use and only at Time 1 in Study 1. Conversely, Item 5 predicted exacerbation frequency whereas the PP-ACT4 did not. CONCLUSION: Our findings suggest that researchers and clinicians should treat the PP-ACT4 and Item 5 as distinct indicators of asthma control because they differentially predict asthma outcomes and likely have distinct meanings to caregivers.Supplemental data for this article is available online at https://doi.org/10.1080/02770903.2022.2036755 .

Caregiver Perceptions of Change in Pediatric Asthma Control During the COVID-19 Pandemic.

Purpose: Although several indicators suggest that pediatric asthma control in the United States improved early in the pandemic, other indicators suggest not. Missing are reports from caregivers of the experiences of their children with asthma early in the pandemic. Methods: Using the PP-ACT and other measures that we specifically constructed for our research, we conducted a cross-sectional national survey of US caregivers of children with asthma (N=595) to examine perceived change in their child's asthma control and changes in reports of ED visits and use of emergency relief medicine and controller medicine pre-pandemic (January to March 2020) versus early-pandemic (June to September 2020). Results: Caregivers fell into three groups: most caregivers perceived that their child's asthma control was improved (50.3%) or unchanged (41.2%), and few reported worse control (8.5%). Surprisingly, all three groups of caregivers reported similar frequencies of early-pandemic and pre-pandemic ED visits and use of emergency relief medicine. Also surprising, caregivers who perceived their child's asthma as more controlled (compared with the other two groups) reported more frequent ED visits and use of emergency relief medicine, yet also more use of controller medicine at both early-pandemic and pre-pandemic. Conclusion: The mismatch between caregivers' perceptions of their child's early-pandemic asthma control and their reports of ED visits and use of emergency relief medicine suggests that caregivers may rely on a gist (a global evaluation that can include nonbiomedical evidence) when estimating their child's asthma control. Caregivers and their families could benefit from help from clinicians in understanding the discrepancy between subjective asthma control and asthma control indicators and in understanding what well-controlled asthma looks and feels like.

AIM2ACT: Randomized controlled trial protocol for a mobile health intervention for early adolescents with asthma.

Early adolescents diagnosed with asthma have difficulties consistently performing disease self-management behaviors, placing them at-risk for poor asthma control, morbidity, and reduced quality of life. Helpful caregiver support is pivotal in determining whether early adolescents develop and master asthma self-management behaviors. We developed Applying Interactive Mobile health to Asthma Care in Teens (AIM2ACT), a mobile health intervention to facilitate helpful caregiver support in early adolescents (12-15 year-olds) with poorly controlled asthma. AIM2ACT is a dyadic smartphone intervention that contains three components: 1) ecological momentary assessment to identify personalized strengths and weaknesses in asthma self-management behaviors; 2) collaborative identification and tracking of goals that help early adolescents to become increasingly independent in managing their asthma; and 3) a suite of skills training videos. This paper describes our plans to test the efficacy of AIM2ACT and evaluate long-term maintenance of treatment effects in a fully powered randomized controlled trial with 160 early adolescents with poorly controlled persistent asthma, ages 12-15 years, and a caregiver. Families will be randomly assigned to receive AIM2ACT (n = 80) or a mHealth attention control condition (n = 80) that accounts for attention and novelty of a technology-based intervention for 6 months. Assessments will occur at baseline, post-intervention, and 3-, 6-, and 12-month follow-up time points. We will collect patient-reported and objectively monitored (e.g., spirometry, adherence) outcomes. Given the timing of the trial, a secondary exploratory goal is to evaluate the perceived impact of COVID-19 on family functioning and parental control of their adolescent's asthma in the context of our intervention.

Interpersonal comparison among caregivers of children with asthma.

Objective: We examined the extent to which caregivers of children with asthma used interpersonal comparisons-a novel comparison process that parallels social comparison and temporal comparison-to form judgments about their child. Methods & Measures: Using semi-structured interviews adapted from the McGill Illness Narrative Interview, we examined the interpersonal comparisons that caregivers of a child with asthma (n = 41) made regarding their child. Results: Interpersonal comparisons influenced caregiver thoughts, feelings, and behavior. They helped caregivers distinguish asthma from other breathing problems, evaluate the severity of the asthma, and understand their child's experience. However, they also created uncertainty by highlighting the complex, unpredictable nature of asthma. Interpersonal comparisons were a source of gratitude and hope, but also worry and frustration. Finally, interpersonal comparisons influenced caregivers' decisions and actions, resulting in decisions that aligned with and, at times, ran counter to biomedical models of asthma care. In some instances, caregivers used interpersonal comparisons to motivate their child's behavior. Conclusion: The interpersonal comparisons served as a source of information for caregivers trying to understand and manage their child's asthma. Investigating these comparisons also expands how we think about other comparison theories.

How do embodied experiences of asthma influence caregiver conceptual models?

RATIONALE: Many studies propose that patients', caregivers', and children's asthma management practices may diverge from biomedical recommendations because their understandings of asthma (i.e., conceptual models) are different from biomedical perspectives. However, little research in this area has examined conceptual models of asthma using embodiment theory, which suggests that caregivers' and children's experiences of the physical body shape their perspectives and consequent management strategies. OBJECTIVE: We investigated how two embodied processes of symptom perception-detection and interpretation-may influence caregiver or patient conceptions of asthma. METHODS: We interviewed 41 caregivers of children with asthma in Gainesville, Florida, and St. Louis, Missouri, and conducted ethnographic visits or virtual interviews with 19 children with asthma aged 6-16. RESULTS: Four aspects of asthma's embodied experience shaped conceptual models via processes of detection and interpretation: 1) symptoms are experienced in the context of other bodily processes; 2) acute symptoms and exacerbations are more salient than their absence; 3) the embodied experience of asthma is one of integrated physiological and emotional processes; and 4) caregivers and children acquire embodied practices of perceiving symptoms that produce embodied knowledge. CONCLUSION: Participant narratives suggest that embodied experiences of asthma shape caregivers' and children's understandings of asthma in ways that differ from the biomedical model. We argue that a focus on embodied experiences may provide important ground for mutual understanding and communication between providers and caregivers and/or patients.

Daily adherence variability and psychosocial differences in adolescents with asthma: a pilot study.

Adolescents with asthma endorse psychosocial difficulties as barriers to inhaled corticosteroid adherence. This study examined patterns of variability in adherence and within-person associations of psychosocial variables with adherence across days. Participants included twenty-five adolescents (Mage = 14.7, SD = 1.68; 48% male) with persistent asthma. We measured adherence via electronic monitoring. Adolescents completed daily surveys measuring asthma symptoms, stress, mood, and affect. We examined within-person differences in the effect of symptoms and psychosocial variables on adherence. Adherence decreased over time. The addition of a random slope improved model fit (- 2ΔLL(1) = 9.36, p < .01). Greater asthma symptoms were significantly associated with higher adherence at the within-person level and with lower adherence between persons. We observed evidence of individual differences in the associations of stress and affect with adherence. Within-person, day-level fluctuations in adherence occur. Symptoms and psychosocial variables may influence adherence. Individually tailored interventions may effectively address nonadherence.

Situating household management of children's asthma in the context of social, economic, and environmental injustice.

BACKGROUND: Structural determinants of health are social, economic, and environmental forces that generate unequal opportunities for resources and unequally distribute exposure to risk. For example, economic constraint, racial discrimination and segregation, and environmental injustice shape population-level asthma prevalence and severity. Structural determinants are especially relevant to consider in clinical settings because they affect everyday household asthma management. OBJECTIVE: To examine how structural determinants shape everyday household management of pediatric asthma and offer a framework for providers to understand asthma management in social context. DESIGN: Qualitative interviews of caregivers for children with asthma. PARTICIPANTS: Participants included 41 caregivers in two U.S. cities: St. Louis, Missouri (n = 25) and Gainesville, Florida (n = 16). Most caregivers were women (83%), Black (73%) and/or had low socioeconomic status (SES; 78%). Caregivers cared for children with asthma aged 0-4 (32%), 5-11 (68%) and 12-17 (54%). APPROACH: We carried out narrative interviews with caregivers using an adapted McGill Illness Narrative Interview and using qualitative analysis techniques (e.g. inductive and deductive coding, constant comparison). KEY RESULTS: Caregivers highlighted three ways that structural determinants complicated asthma management at home: 1) housing situations, 2) competing household illnesses and issues, and 3) multi-household care. CONCLUSIONS: By connecting social, economic, and environmental injustices to the everyday circumstances of asthma management, our study can help providers understand how social contexts challenge asthma management and can open conversations about barriers to adherence and strategies for supporting asthma management at home. We offer recommendations for medical system reform, clinical interactions, and policy advocacy.

Examining commonsense epidemiology: The case of asthma.

Commonsense epidemiology-how lay people think about diseases and their causes and consequences-can influence how people respond. We examined three lay epidemiological beliefs about 20 triggers and 19 symptoms among 349 caregivers of children with asthma. Our findings contradicted the prevalence-seriousness hypothesis (perceived prevalence and seriousness correlate negatively). The data partially supported the prevalence-control hypothesis (perceived prevalence and asthma control correlate negatively). We found weak support for the seriousness-control hypothesis (perceived seriousness and asthma control correlate negatively). These findings suggest boundary conditions on the application of commonsense epidemiological beliefs.

Adaptive Mobile Health Intervention for Adolescents with Asthma: Iterative User-Centered Development.

BACKGROUND: Adolescents diagnosed with persistent asthma commonly take less than 50% of their prescribed inhaled corticosteroids (ICS), placing them at risk for asthma-related morbidity. Adolescents' difficulties with adherence occur in the context of normative developmental changes (eg, increased responsibility for disease management) and rely upon still developing self-regulation and problem-solving skills that are integral for asthma self-management. We developed an adaptive mobile health system, Responsive Asthma Care for Teens (ReACT), that facilitates self-regulation and problem-solving skills during times when adolescents' objectively measured ICS adherence data indicate suboptimal rates of medication use. OBJECTIVE: The current paper describes our user-centered and evidence-based design process in developing ReACT. We explain how we leveraged a combination of individual interviews, national crowdsourced feedback, and an advisory board comprised of target users to develop the intervention content. METHODS: We developed ReACT over a 15-month period using one-on-one interviews with target ReACT users (n=20), national crowdsourcing (n=257), and an advisory board (n=4) to refine content. Participants included 13-17-year-olds with asthma and their caregivers. A total of 280 adolescents and their caregivers participated in at least one stage of ReACT development. RESULTS: Consistent with self-regulation theory, adolescents identified a variety of salient intrapersonal (eg, forgetfulness, mood) and external (eg, changes in routine) barriers to ICS use during individual interviews. Adolescents viewed the majority of ReACT intervention content (514/555 messages, 93%) favorably during the crowdsourcing phase, and the advisory board helped to refine the content that did not receive favorable feedback during crowdsourcing. Additionally, the advisory board provided suggestions for improving additional components of ReACT (eg, videos, message flow). CONCLUSIONS: ReACT involved stakeholders via qualitative approaches and crowdsourcing throughout the creation and refinement of intervention content. The feedback we received from participants largely supported ReACT's emphasis on providing adaptive and personalized intervention content to facilitate self-regulation and problem-solving skills, and the research team successfully completed the recommended refinements to the intervention content during the iterative development process.

Continuous Albuterol With Benzalkonium in Children Hospitalized With Severe Asthma.

BACKGROUND AND OBJECTIVES: The albuterol dropper bottle used to prepare solutions for continuous nebulization contains the preservative benzalkonium chloride (BAC). BAC, by itself, has been shown to cause bronchospasm. We hypothesized that BAC would decrease the therapeutic efficacy of albuterol in patients with acute asthma exacerbations. METHODS: We performed a retrospective cohort study comparing the clinical outcomes of patients <18 years of age receiving continuous nebulized albuterol with and without BAC. For the primary end point (duration of continuous albuterol nebulization), we compared the 2 groups with Kaplan-Meier estimate of survival curves, conducted a log-rank test of difference, and adjusted for baseline characteristics using multivariable Cox regression. A P value <.05 was considered significant. RESULTS: A total of 477 patients were included in the analysis (236 exposed to BAC and 241 controls). The duration of continuous nebulization was significantly longer in the BAC group than in the control group (median of 9 vs 6 hours; 15.7% required continuous nebulization compared to 5.8% of controls at 24 hours). The control group was 79% more likely to stop continuous nebulization at any particular point in time (hazard ratio 1.79; 95% confidence interval: 1.45 to 2.22; P < .001) and 43% more likely to stop additional respiratory support (hazard ratio 1.43; 95% confidence interval: 1.16 to 1.75; P < .001). CONCLUSIONS: BAC is a functional albuterol antagonist associated with a longer duration of continuous albuterol nebulization treatment and additional respiratory support, suggesting that preservative-free albuterol formulations are safer for use in continuous nebulization.

Nationwide Shortage of Albuterol Inhalers and Off-Label Use in COVID-19 Patients.

The surge in COVID-19 cases during the 2020 Spring led to a nationwide shortage of albuterol inhalers. As a new surge has begun, shortages may make it difficult for patients with obstructive lung disease, including children with asthma, to obtain refills. Since there is no evidence that albuterol relieves symptoms in COVID-19 patients with respiratory symptoms not caused by bronchospasm, it is reasonable for clinicians to not prescribe it for COVID-19 patients unless they also have asthma or chronic obstructive pulmonary disease.

Responsive Asthma Care for Teens (ReACT): development protocol for an adaptive mobile health intervention for adolescents with asthma.

INTRODUCTION: Asthma is a leading cause of youth morbidity in the USA, affecting >8% of youth. Adherence to inhaled corticosteroids (ICS) can prevent asthma-related morbidity; however, the typical adolescent with asthma takes fewer than 50% of their prescribed doses. Adolescents are uniquely vulnerable to suboptimal asthma self-management due to still-developing executive functioning capabilities that may impede consistent self-regulation and weaken attempts to use problem solving to overcome barriers to ICS adherence. METHODS AND ANALYSIS: The aims of this project are to improve adherence to ICS as an important step towards better self-management among adolescents aged 13-17 years diagnosed with asthma by merging the efficacious behaviour change strategies found in behavioural health interventions with scalable, adaptive mobile health (mHealth) technologies to create the Responsive Asthma Care for Teens programme (ReACT). ReACT intervention content will be developed through an iterative user-centred design process that includes conducting (1) one-on-one interviews with 20 teens with asthma; (2) crowdsourced feedback from a nationally representative panel of 100 adolescents with asthma and (3) an advisory board of youth with asthma, a paediatric pulmonologist and a behavioural health expert. In tandem, we will work with an existing technology vendor to programme ReACT algorithms to allow for tailored intervention delivery. We will conduct usability testing of an alpha version of ReACT with a sample of 20 target users to assess acceptability and usability of our mHealth intervention. Participants will complete a 4-week run-in period to monitor their adherence with all ReACT features turned off. Subsequently, participants will complete a 4-week intervention period with all ReACT features activated. The study started in October 2018 and is scheduled to conclude in late 2019. ETHICS AND DISSEMINATION: Institutional review board approval was obtained at the University of Kansas and the University of Florida. We will submit study findings for presentation at national research conferences that are well attended by a mix of psychologists, allied health professionals and physicians. We will publish study findings in peer-reviewed journals read by members of the psychology, nursing and pulmonary communities.

Direct Observed Therapy of Inhaled Corticosteroids for Asthma at School or Daycare.

Background: Poor adherence with inhaled corticosteroid (ICS) medication is common in the pediatric population and can result in poor asthma control with increased frequency of asthma-related complications. The purpose of this study was to determine whether or not the initiation of ICS administration twice per day at school/daycare in patients with poor medication adherence at home improves asthma health care outcomes. Methods: We retrospectively selected patients followed by our Pediatric Pulmonology Clinic who had poorly controlled asthma and had been assigned to receive ICS twice daily at school/daycare due to poor adherence with ICS therapy. We analyzed the number of short courses of oral corticosteroids, hospital admissions, emergency department visits, and intramuscular methylprednisolone administrations for asthma exacerbations for the year before and after the intervention. The Wilcoxon signed rank test with continuity correction was used in the primary analysis. Results: Forty-nine patients who met the inclusion criteria were identified, but only 40 actually started the intervention. The number of oral corticosteroid courses per year decreased from 1.35 ± 1.1 before the intervention to 0.68 ± 1.2 (P = 0.008) postintervention, hospital admissions per year decreased from 0.45 ± 0.7 to 0.10 ± 0.3 (P = 0.006), emergency department visits per year decreased from 0.55 ± 0.8 to 0.28 ± 0.6 (P = 0.084), and intramuscular repository methylprednisolone injections per year for asthma exacerbations decreased from 0.20 ± 0.4 to 0.10 ± 0.3 (P = 0.23). Conclusion: These results indicate that school/daycare administration of ICS may be an effective option to improve indicators of asthma exacerbations in children with poor adherence to ICS at home.

Benzalkonium Chloride: A Bronchoconstricting Preservative in Continuous Albuterol Nebulizer Solutions.

For convenience, many pediatric hospitals are preparing solutions for continuous nebulized albuterol using the 0.5% 20-ml multidose albuterol dropper bottle. This product contains benzalkonium chloride (BAC) that, by itself, produces bronchospasm that is dose dependent and cumulative. The bronchoconstrictive effects of BAC are greater in patients with more severe airway obstruction and increased airway responsiveness. Use of BAC-containing albuterol during severe acute asthma exacerbations may antagonize the bronchodilator response to albuterol, prolong treatment, and increase the risk of albuterol-related systemic adverse effects. Such a deleterious effect of BAC is difficult to detect because some patients improve slowly or may even worsen during treatment. We recommend that only preservative-free albuterol products be used.

Bioassay of salmeterol in children using methacholine challenge with impulse oscillometry.

BACKGROUND: Bronchoprovocation with methacholine (MC) is the most sensitive method of determining bioequivalence of inhaled bronchodilators. FEV1 is used to determine the endpoint, but many children cannot perform spirometry reproducibly. The purpose of this study was to determine whether MC, using impulse oscillometry (IOS) as the endpoint, can differentiate between two doses of salmeterol (SM). METHODS: This was a single-blind, randomized study of 10 subjects with mild stable asthma, ages 4-11 years. None were taking a long-acting ß-agonist but most were on low-dose inhaled corticosteroid. On one study day, MC was performed 1 hr after one inhalation from each of two separate Advair 100/50 Diskus (100 µg salmeterol treatment). On a second day, MC was performed after one inhalation from Advair Diskus and one inhalation from Flovent Diskus 100 (50 µg salmeterol treatment). The provocative concentration of methacholine causing a 40% increase in total airway resistance (PC40 R5 ) was calculated. RESULTS: The reduction in R5 (bronchodilator effect) was 15.5% and 18.4% for 50 and 100 µg, respectively (NS). After MC (bronchoprotective effect), the geometric mean (95%CI) PC40 R5 (mg/ml) was 2.4 (1.3-4.4) during screening, 22.9 (8.5-61.6) after 50 µg SM and 47.0 (25.2-87.8) after 100 µg SM (P = 0.051 for 50 vs. 100 using a linear mixed effects model). No adverse effects were observed. CONCLUSIONS: MC with IOS endpoint will be a useful method for determining bioequivalence of a generic inhaler in children. Seventy-two subjects will be required to achieve 80% power to assess bioequivalence of SM. Pediatr Pulmonol. 2016;51:570-575. © 2015 Wiley Periodicals, Inc.