Introduction: Uncontrolled or severe asthma results in symptomatic usage of short-acting ß2-agonist usage (SABA). MicroRNAs (miRNAs) are post-translational regulators that can influence asthma biology. This study aims to identify miRNAs that are associated with increased SABA usage. Methods: Small RNA sequenced from blood serum of 1,132 asthmatic children aged 6 to 14 years in the Genetics of Asthma in Costa Rica Study (GACRS) was used for this analysis. Logistic regression identified miRNAs in patients who required increased SABA usage. These miRNA were validated for association with SABA induced BDR. Gene target pathway analysis was performed on validated miRNAs. Results: 21 miRNAs were significantly associated with increased SABA usage with OR ranging from 0.87 to 1.23. Two miRNAs, miR-378a-3p and miR-144-3p, had odds ratio 1.14 (1 - 1.29, p=0.05) and 1.11 (1.01-1.22, p = 0.035), respectively for increased SABA usage and were also significantly associated with bronchodilator response. Furthermore, a linear regression analysis involving these miRNA and bronchodilator response revealed that increased miR-378a-3p correlated with decreased BDR and increased expression of miR-144-3p correlated with improving pulmonary function with bronchodilators. In gene target KEGG pathway analysis, the erythroblastosis viral oncogene (ErbB) signaling pathway had among one of the highest fold enrichment and p-value. Conclusion: Increased expression miR-378a-3p and miR-144-3p was seen in this patient population who required increased SABA usage. There were different bronchodilatory effects seen in these two miRNAs, suggesting different potential mechanisms underlying increased SABA usage.

Introduction: During NICU hospitalization, children born preterm with bronchopulmonary dysplasia (BPD) are frequently prescribed diuretics for treatment of respiratory symptoms. However, less is known about diuretic use and weaning in the outpatient setting. This study sought to characterize clinical features associated with outpatient diuretic use, and timing of diuretic weaning in children with BPD. Methods: Data was obtained by chart review from registry 1224 participants born < 32 weeks gestation, discharged between 2008-2023 and recruited from outpatient BPD clinics at Johns Hopkins Children’s Center and the Children’s Hospital of Philadelphia (97.4% diagnosed with BPD). Data was analyzed using Chi-square tests, t-tests, and ANOVA tests. Results: Children with BPD prescribed diuretics as outpatients (n=737), were more likely to have lower birth weights, earlier gestational age, and severe BPD compared to those not on diuretics (n=487). Of those prescribed diuretics, most children were on a thiazide alone (46.4%) or a thiazide and a potassium sparing agent (44.8%) with a minority on loop diuretics alone (3.3%) or loop diuretic combinations (4.7%). Most children weaned off diuretics by two years of age. Public insurance, earlier gestational age, technology dependence and loop diuretics were associated with slower diuretic weaning. Conclusion: Outpatient diuretic use is common in BPD with > 75% of children being weaned by two years of age. No difference was found in weaning of home oxygen between children on one versus no diuretic. Thiazides were most commonly prescribed with slower outpatient diuretic weaning associated with public insurance, technology dependence and loop diuretic use.

Background Perfluorooctanoic acid (PFOA) is widely used in daily life, however, research has shown its immune suppression function. Our aim is to investigate the relationship between prenatal exposure to PFOA and allergic diseases in children. Methods A prospective birth cohort study involving 648 pregnant women was conducted. Prenatal information was collected by an interview with the women and from medical records. Fetal umbilical cord blood was collected, and concentration of PFOA and genotype of IL-13 rs20541 were detected. Children were followed at 6, 12 and 24 months and information on the development of allergic diseases was recorded. Multivariate logistic regression analysis was used to examine the association between PFOA and allergic diseases. Stratified analysis was performed based on gender and genotype of IL-13 rs20541. Results In multivariate adjusted models, the highest PFOA quartile is associated with odds of atopic dermatitis (AD) (OR 1.66, 95% CI 1.09-2.55), wheezing (OR 4.06, 95% CI 1.30-12.68), and allergic diseases (OR 1.71, 95% CI 1.15-2.54). Female patients with the highest PFOA quartile have a higher odd of AD (OR 2.25, 95% CI 1.20-4.23) and allergic diseases (OR 1.93, 95% CI 1.07-3.46). Patients with GG genotype of IL-13 rs20541 and the highest PFOA quartile also have a higher odd of AD (OR 2.82, 95% CI 1.41-5.67), wheezing (OR 15.16, 95% CI 1.38-166.59), and allergic diseases (OR 2.42, 95% CI 1.27-4.61). Conclusions Prenatal exposure to PFOA increases the risk of developing allergic diseases in children, especially for the female patients and those with the genotype of IL-13 rs20541 GG.

Background: Musculoskeletal problems are reported in the literature as a common problem for people with cystic fibrosis, with a range of aetiologies including an inflammatory arthritis. However, accurate data on the presentations and prevalence are lacking. The aim of this cohort study was to describe the scale and impact of musculoskeletal symptoms in CF. Methods: A collaboratively designed questionnaire was administered to adults attending two large UK CF centres. Data collected evaluated scale and impact of musculoskeletal symptoms. Results: Results were obtained from 489 patients (response rate 59%). Of these, 49% reported that musculoskeletal symptoms impacted their activities of daily living in the previous year. Back pain was common, occurring in 44% of participants in the preceding week. The knee was the most commonly affected painful peripheral joint, with 26% of participants reporting knee pain within the last week rising to 50% within the last year. Early morning stiffness and joint swelling were markedly less common, suggesting that the majority of musculoskeletal pain in CF is not due to an inflammatory arthritis but is due to other factors. Conclusion: Musculoskeletal problems are common in CF and frequently affect activities of daily living. Symptoms of inflammatory arthritis occurred in only a small minority of individuals. A focused approach to characterising and clarifying the aetiology of musculoskeletal symptoms is needed to inform the management of these disabling symptoms.

The global health emergency of COVID-19 in early 2020 placed much of the population under quarantine. Interstitial Lung Disease in childhood (chILD) was recommended to be a paediatric clinically extremely vulnerable (CEV) group in April 2020 for shielding due to the unknown health consequences of COVID-19 in children with chronic respiratory conditions. This qualitative longitudinal research study explores how chILD parents in the UK experienced COVID-19 lockdown from over two interview time points. Participants ( n = 8) were recruited from chILD patient organisations and online communities. Interview one focused on the period between January 2020 to July 2020, gaining personal insight into respondent’s experience of lockdowns, which included questions on support systems and media coverage of COVID-19. The second interview asked how respondents managed further UK lockdowns between September 2020 and May 2021. The main themes were uncertainty and adaptation. Respondents described how they navigated the UK lockdowns and undertook various risk management strategies for pandemic isolation. Once these were established, routine and positive family bonding was reported, along with a reluctant acceptance of the COVID-19 virus and continued shielding. As new COVID-19 information emerged, risk management strategies changed or remained for some respondents, bringing a feeling of living with COVID-19 as a ‘new’ normal. Understanding the unique insights people with rare diseases such as chILD face during a global pandemic adds to policy and healthcare literature. Recommendations include further study of caregiver traits and resilience, essential facets of positive pandemic adaptation.

not-yet-known not-yet-known not-yet-known unknown Objective: To investigate use of asthma controller medications and their effect on lung function in pediatric patients with SCD. Methods: Retrospective study in pediatric patients of African American ethnicity with SCD treated at PCH between 2014-2021. Associations of asthma controller medications with changes in lung symptoms (cough, wheeze, chest pain, shortness of breath with exercise, sleep disturbance), Acute Chest Syndrome (ACS), and percent predicted spirometry (FEV 1, FVC, FEV 1/FVC, FEF 25%-75%)) were examined (Fisher exact, Wilcoxon rank sum) separately in SCD patients with and without asthma. Results: Of the total 98 SCD patients, 28 (29%) had an asthma diagnosis. Asthma controller medications were prescribed to 20 (71% of 28) with asthma and 37 (53% of 70) without asthma. Patients with vs without asthma were more likely to receive combined medications (55% vs 8.1%), but less ICS alone (35% vs 48 %) or LTRA alone (10% vs 43%) (p<0.0003). Medication use vs non-use improved cough (38% vs 9%, P=0.006) and shortness of breath with exercise (32% vs 12%, P=0.03) in SCD patients without asthma, but these were non-significant in asthmatics. Medications also improved the mean percent change in both non-asthmatics FEV 1 (10.2 vs -3.2; P<0.0001), FVC (8.8 vs -0.7; P=0.002), and FEF 25%-75%, (17.6 vs -9.7; P=0.0005), and asthmatics FEV 1 (16.4 vs -5.2; P=0.001), FVC (13.7 vs -3.8; P=0.0009), and FEF 25%-75%, (26.1 vs -5.0; P=0.02). Conclusion: These findings, demonstrating improved lung function with asthma controller medications in pediatric patients with SCD, irrespective of an asthma diagnosis, holds great promise for this undertreated population.

Background The benefits of Elexecaftor-Tezacaftor-Ivacaftor (ETI) therapy on the health and wellbeing of people with CF (pwCF) are well documented. Since approval, however, a growing number of potential side effects have emerged in reports from clinical practice. With current understanding of ETI tolerability limited to data from clinical trials, the prevalence of side effects and their impact on care decision making remains poorly categorized. Methods A ten-question survey was developed and distributed to patients 18 years or older who were treated at the Massachusetts General Hospital CF centers. Reports of side effects were measured across twelve distinct categories, and dose adjustments and discontinuation due to side effects were collected. If a patient reported no side effects, they did not have to complete the entire survey. Results Among ninety-two respondents initiated on ETI, 51 respondents (55.4%) reported potential side effects and 41 (44.5%) respondents reported no adverse events. The most commonly reported side effects were mental health, changes in appearance, and gastrointestinal complaints, which were reported by 22.8%, 30.4%, and 21.7% of patients, respectively. Eighteen (19.6%) respondents modified their dosing in response to side effects, and six discontinued treatment permanently (6.52%) due to persistent side effects. Conclusions Responses demonstrated marked heterogeneity, with most respondents reporting at least one side effect following initiation. Dose modification was commonly utilized to mitigate adverse effects, however few respondents had to discontinue treatment. These findings demonstrate the importance of monitoring for potential drug-related side effects of ETI in clinical settings.

Background: Spirometry is the gold standard for assessing airway function for clinical studies; however, obtaining high quality data in young children remains challenging. Since the forced oscillation technique (FOT) requires less subject cooperations, there has been increasing interest in FOT, particularly in young children. We evaluated whether spirometry and FOT in young children provides comparable ability to detect a treatment effect. Methods: We recently reported in a randomized controlled trial that vitamin C compared to placebo treatment of mothers who smoked during pregnancy (MSDP) results in the offspring having significantly higher forced expiratory flows at 5-years of age, as well as significantly less wheeze at 4-6 years of age. In these same offspring, we also measured FOT at 8-Hz impedance at 3, 4, and 5 years of age. Results: Although spirometry demonstrated significantly increased forced expiratory flows (FEFs) in the vitamin C compared to placebo treatment group at 5-years of age (p < 0.001), we were not able to detect a similar treatment effect using FOT impedance. Conclusions: It may be challenging to obtain technically successful spirometry in pre-school children; however, forced expiratory flows may provide a better outcome than single frequency FOT impedance to assess improvements in airway function in these young subjects.

Lung ultrasound is increasingly used in neonatal intensive care units. We reviewed the most recent available literature, mainly using PubMed, and summarized the ultrasonographic patterns, features of most neonatal respiratory morbidities, and clinical application in neonates. Lung ultrasound is a non-invasive, radiation-free, and reproducible adjunct tool that can guide the clinical management of neonates presenting with respiratory distress.

OBJECTIVES: High-frequency oscillatory ventilation with volume guarantee (HFOV with VG) can optimize respiratory support in preterm infants. However, its superiority over conventional HFOV remains uncertain. This systematic review aimed to analyze ventilatory and clinical effects of HFOV with VG compared with conventional HFOV in neonates under 44 weeks corrected gestational age. METHODS: We systematically searched Pubmed, EMBASE, Cochrane, and ClinicalTrials.gov from inception until August 4th, 2023, to identify randomized or observational studies comparing HFOV with VG with HFOV without VG in in neonates under 44 weeks corrected gestational age. Outcomes of interest included high-frequency tidal volume (VThf) and amplitude oscillations, carbon dioxide diffusion coefficient (DCO2) and carbon dioxide partial pressure (PaCO2) mean values, and episodes of hypocarbia or hypercarbia, hypoxemia episodes, duration of mechanical ventilation, rates of bronchopulmonary dysplasia and intraventricular hemorrhage, and death. ROB-2 and ROBINS were used for risk of bias assessment. RESULTS: This study included 260 patients from two crossover and four cohort studies. Gestational age at birth ranged from 23 to 29 weeks. The included studies presented a considerable risk of bias. A meta-analysis could not be performed, due to the differences in studies’ design, relevant risk of bias, incomplete reporting, and differences in ventilatory settings and reference values adopted. Report of the findings suggest that HFOV with VG, compared with HFOV, may reduce VThf variability and, consequently, hypo- and hypercarbia episodes. However, no significant differences in terms of BPD, IVH or mortality were observed. CONCLUSION: This systematic review does not provide evidence of the superiority of HFOV with VG over conventional HFOV in the context of ventilation of preterm infants, indicating the need for further studies evaluating the effects of VG on HFOV.

Objective: To assess in vitro nebulized drug delivery during invasive and non-invasive ventilation models, comparing jet and vibrating mesh nebulizers. Aimed to compare differences in absolute inhaled dose, delivery rate and residual volume in various pediatric ventilation models with either face mask, mechanically ventilated, high flow nasal therapy or blow-by methods utilizing approved nebulizer locations. Methods: Compared drug delivery performance of a continuous output jet nebulizer (JN) with a vibrating mesh. The non-invasive model simulated a spontaneously breathing 9-month-old child using an anatomically correct model of upper airways and breathing simulator. The intubated model consisting of a mechanical ventilator with a heated humidifier in a pediatric breathing circuit and endotracheal tube. A JN (Aquineb), driven with 6 L·min -1 or a VMN (Aerogen Solo) driven with 2 L·min -1 supplemental oxygen were assessed by dose, delivery rate and residual volume. Drug dose was quantified using spectrophotometric analysis. Results: During normal spontaneous breathing, VMN dose was almost double that of JN ( P < 0.001), while delivery rate by VMN was also quicker, ( P < 0.001). Residual volume was significantly higher using JN ( P < 0.0001). During mechanical ventilation, VMN had a greater than 3-fold dose ( P < 0.0001), while the rate of delivery by VMN was also quicker ( P < 0.0001). Residual volume was also significantly greater using JN ( P < 0.001) during ventilation. During HFNT, aerosol delivery via nasal cannula was shown to be affected by gas flow rate for both VMN and JN, with again VMN delivering a greater dose over JN . Salbutamol delivery was also significantly greater using VMN for blow-by delivery. Conclusion: This study demonstrates significantly increased dose and rate of delivery, and significantly decreased residual volumes post-nebulization for airway deposition using a VMN compared to JN. Use of VMNs could improve drug delivery in pediatric populations, potentially altering the clinical course.

Objective: To determine if pediatric patients who have laterality defects and meet the diagnostic criteria for Primary Ciliary Dyskinesia (PCD) evaluation are being referred to and evaluated by pediatric pulmonologists. Subjects and methods: A retrospective chart review using the electronic medical record was conducted at Dallas Children’s Health for patients with laterality defects who met two or more of the PCD evaluation criteria: laterality defect, chronic daily cough, and chronic daily nasal congestion starting in infancy, and neonatal respiratory distress of unclear etiology requiring oxygen or positive pressure for 24 hours or longer. The referral rates to pediatric pulmonary, genetics, and whether patients were evaluated for PCD were determined. Results: The electronic medical record search for laterality defects identified 433 patients. Of these, 14 patients were excluded because they were found not to have a laterality defect, and 38 because they did not have enough data (birth history, onset, and or characteristics of cough) for analysis. Neonatal respiratory distress was excluded as a symptom for those patients with a known etiology for their respiratory distress. Of the 381 patients who met the criteria for analysis, 192 (50%) met only one criteria for PCD evaluation (laterality defect), and 50% met 2 or more of the criteria. Of the 84 patients who met the minimum 2 criteria for PCD evaluation, 45% were referred to pulmonary, 14% to genetics, and only 15% were evaluated for PCD. Of the 27 patients who met all 4 PCD criteria for evaluation, 96% were referred to pulmonary, 85% to genetics, and 85% were evaluated for PCD. Among the 381 patients studied, there were no significant differences in the referral rate by the patient’s demographics, including sex, race, ethnicity, and insurance type. The sensitivity of referrals increased with the number of PCD criteria. Conclusions: A substantial number of pediatric patients meeting the criteria for PCD evaluation with 2 PCD referral criteria are not referred to pediatric pulmonologists, and a larger number are not being evaluated for PCD. As expected, patients with 3 or 4 PCD referral criteria have a higher rate of referral to pulmonary than those meeting the required 2 criteria. Nonetheless, a substantial number of patients who meet all 4 criteria for evaluation are not being evaluated for PCD even when referred to pulmonary or genetics. This highlights the importance of PCD education and awareness efforts for Pediatric specialists and subspecialists, including pediatric pulmonologists.

Rationale: Aerosolized medications are crucial for resolving respiratory issues in mechanically ventilated patients. Infants often receive nebulized medications via hand ventilation using an anesthesia bag, but evidence on optimal aerosol delivery with this method is limited. We tested various configurations of the Mapleson breathing circuit to optimize albuterol delivery to simulated intubated pediatric patients. Methods: Using a simulated pediatric lung model (ASL 5000) with the semi-open Mapleson anesthesia circuit, we delivered 2.5 mg albuterol sulfate to a viral/bacterial filter (Respiguard 202). Four models were compared, varying fresh gas flows (FGF), nebulizer placements, and the use of dead space. Five Registered Respiratory Therapists (RRTs) administered the aerosol into the collection filter, following defined ventilation parameters. Each model was tested in random order to avoid fatigue bias. Albuterol concentrations eluted from in-line filters were measured by spectrophotometry (absorbance at 276 nm). Results: No inter-user variability was observed among the RRTs. Significant differences in albuterol delivery efficacy were noted between models (One Way ANOVA, Tukey’s post hoc, N=5). Model 4, with the nebulizer closest to the collecting filter, recovered 21.7±3.87% of albuterol. The standard clinical model was least effective, with only 0.1±0.47% albuterol recovery. Conclusion: Modifying the anesthesia breathing circuit significantly improved aerosol drug delivery efficiency. Our findings suggest that current clinical practices for nebulized drug delivery are inefficient and can be markedly improved with simple adjustments in nebulizer positioning and gas flow within the circuit.

Objective: Although high-flow nasal cannula (HFNC) is a commonly used treatment method to manage respiratory distress in children, it may still result in treatment failure requiring advanced airway support. Such treatment failure can lead to increased morbidity and mortality. In light of this, a cross-sectional observational study was conducted in a pediatric intensive care unit (PICU) to identify predictive factors associated with HFNC failure in children. Materials and methods: A total of 187 patients aged between one month and 18 years with moderate to severe respiratory distress treated with HFNC therapy in the PICU between October 2018 and January 2020 were included in the study. Patients with chronic lung disease and cyanotic congenital heart disease were excluded. Clinical assessments included respiratory scores, relevant laboratory data, and treatment outcomes. In the statistical analysis, data variables were evaluated using the Mann–Whitney U test, χ2 test, receiver operating characteristic, and multivariate logistic regression analysis. Results: Analysis of 114 patients revealed a HFNC treatment failure rate of 31.6%. Multivariate logistic regression revealed that the presence of medical comorbidities (OR: 25.8, 95% CI: 2.61-254.5, p=0.005), an increased mRDAI score at the first hour of HFNC therapy (OR: 2.9, 95% CI: 1.32-6.48, p=0.008), and higher PRISM scores (OR: 2.1, 95% CI: 1.44-3.07, p<0.001) were significant predictors of HFNC failure. Conclusions: This study underscores the importance of early identification of predictive factors for HFNC therapy failure to improve management strategies and patient outcomes in pediatric patients with respiratory distress.

Background: Primary ciliary dyskinesia (PCD) is associated with ventilation defects and heterogeneous impairment of pulmonary function. Spirometry may underestimate PCD severity and complexity. This study aimed to evaluate spirometry, lung clearance index (LCI), and impulse oscillometry (IOS) in children with PCD and healthy controls, and compare them in terms of early detection of lung disease. Methods: In this cross-sectional, prospective study, participants included children aged 6-18 years with PCD and healthy age-matched controls. Lung function tests using LCI, IOS, and spirometry were conducted on the same day for all participants. Results: Thirty-two children with PCD (median age 13.19 years) and 44 age-matched healthy controls (median age 12.32 years) were studied. PCD was associated with lower FEV1, FVC, FEV1/FVC, R5, R10, R15, R20, X5, Fres, and LCI 2.5% mean values (p<0.05). Abnormal LCI 2.5% was found in 46.5% of patients with predicted FEV1 > 80%. Significant inverse correlations were observed between LCI 2.5%, FEV1, FVC, and Fres in PCD patients (p<0.001, r:-0.635; p=0.002, r:-0.517; p=0.006, r:-0.479; respectively. Conclusion: This is the first study to compare LCI, IOS, and spirometry in children with PCD. The study has shown that there are significant differences in spirometry, LCI, and IOS values between children with PCD and healthy controls. LCI can detect airway anomalies earlier than spirometry in PCD patients. IOS and LCI are valuable respiratory function tests that can be used in PCD follow-up.

Background: The estimated prevalence of tracheobronchomalacia (TBM) in children is about 1:2100. Tracheomalacia (TM) prevalence is higher in patients with chronic lung disease such as bronchiectasis and cystic fibrosis (CF) and may contribute to increased morbidity. Objective: To determine the prevalence and assess clinical features of TM, TBM and bronchomalacia (BM) in patients with primary ciliary dyskinesia (PCD). Methods: We performed a retrospective case-note review of all children with a confirmed or highly likely diagnosis of PCD attending Oslo University Hospital between 2000-2021. We selected those who had undergone flexible fiberoptic bronchoscopy (FB) and in whom the presence of TBM was assessed. We retrieved demographic and clinical data, including airway symptoms, PCD-diagnostic criteria, indication for bronchoscopy, the presence of lobar atelectasis, bacteriology and the descriptive and unblinded video-recorded results of FB. Complications occurring during and after bronchoscopy were noted. Results: Of 71 children with PCD, 32 underwent FB and were included in the review. The remaining 39 were included for TBM prevalence calculation only. Median age at FB was 6.0 y (3.1 – 11.9). Twenty-two children (69%) had intrathoracic airway malacia. Four (13%) had isolated TM, seven (22%) had TBM, and 11 (34%) had isolated BM affecting either main (n=4) or lobar bronchi (n=7) (LBM), including four with associated lobar atelectasis. FB related complications, one major, 12 minor, were documented in 13 children (41%). Conclusion: We found a high prevalence of TBM among children with PCD undergoing FB. This may represent a significant comorbidity and have implications for patient management.

Caring for children with asthma continues to be an essential responsibility of the pediatric pulmonologist. In this Pediatric Pulmonology Year in Review, we summarize the significant publications focused on pediatric asthma that have been published over the last year. We will discuss new findings that assist in the diagnosis and evaluation of pediatric asthma, highlight risk factors and social determinants that impact successful care, and discuss new interventions and treatment modalities for acute exacerbations and maintenance control. We hope this review can provide new insights and guidance for implementation into clinical practice within the field of pediatric asthma.

Background & Objectives: Supplemental oxygen and aerosol therapy may be used in combination as a treatment for neonates suffering from hypoxemia caused by respiratory diseases. Due to cost and lack of availability of oxygen cylinders in some countries, oxygen concentrators are a reported substitute. This study was designed to determine whether using an oxygen concentrator and low-flow oxygen therapy impacts aerosol drug delivery in a simulated spontaneously breathing neonate patient. Methods: A vibrating mesh nebuliser (VMN; Aerogen Solo) was used to aerosolise a 500µL dose of salbutamol. The aerosol was delivered via a nasal cannula to a neonate head model in combination with oxygen concentrator at gas flow rates of 0.2, 1.0 and 5.0 LPM and low-flow oxygen therapy at gas flow rates of 1.0, 4.0 and 5.0 LPM. The mass of drug in terms of emitted and tracheal doses were recorded. The impact of VMN operation and refill on circuit pressure in both systems was also measured. Results: The oxygen concentrator delivered a higher emitted dose than the low flow system, the largest emitted dose (%) being 20.58 ± 0.50% and 14.69 ± 0.89% respectively at 1.0 LPM , p = 0.018. The largest tracheal dose (%) was generated with the oxygen concentrator, 11.01 ± 0.29% at 5.0LPM compared to 9.66 ± 1.53% for low-flow oxygen therapy, p = 0.073. Refill and operation of the VMN did not impact the circuit pressure in either system. Conclusions: This study shows that the system used to provide combinational aerosol and supplemental oxygen therapy has a significant impact on the quantity of nebulised therapeutic delivered to the patient.