Pulmonary Vascular Dysfunctions in Cystic Fibrosis

Cystic Fibrosis (CF) is an inherited disorder caused by a deleterious mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Given that the CFTR protein is a chloride channel expressed on a variety of cells throughout the human body, mutations in this gene impact several organs, particularly the lungs. For this very reason, research regarding CF disease and CFTR function has historically focused on the lung airway epithelium. Nevertheless, it has been discovered more than two decades ago that CFTR is also expressed and functional on endothelial cells. Despite the great strides that have been made in understanding the role of CFTR in the airway epithelium, the role of CFTR in the endothelium remains unclear. Considering that the airway epithelium and endothelium work in tandem to allow gas exchange, it becomes very crucial to understand how a defective CFTR protein can impact the pulmonary vasculature and overall lung function. Fortunately, more recent research has been dedicated to elucidating the role of CFTR in the endothelium. As a result, several vascular dysfunctions associated with CF disease have come to light. Here, we summarize the current knowledge on pulmonary vascular dysfunctions in CF and discuss applicable therapies.

Circadian blood pressure dysregulation in children with obstructive sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) adversely affects normal blood pressure (BP) and may disrupt circadian BP patterns. We sought to examine 24-hour circadian BP rhythms in children with OSA and healthy controls.

METHODS

Children 5-14 years with OSA and healthy controls underwent 24-hour BP monitoring and actigraphy to quantify sleep. Shape invariant statistical models compared circadian BP patterns (e.g. times of BP peaks, time arrived at peak BP velocity [TAPV]) in the OSA and control groups.

RESULTS

The analytic sample included 219 children (mild OSA: n = 52; moderate-to-severe OSA (MS-OSA): n = 50; controls: n = 117). In the morning, the MS-OSA group had earlier TAPV for DBP than controls (51 minutes, p < 0.001). TAPV in the evening was earlier for the MS-OSA group than controls (SBP: 95 minutes, p < 0.001; DBP: 28 minutes, p = 0.028). At mid-day, SBP and DBP velocity nadirs were earlier for the MS-OSA group than controls (SBP: 57 minutes, p < 0.001; DBP: 38 minutes, p < 0.01). The MS-OSA group reached most BP values significantly earlier than controls; the largest differences were 118 minutes (SBP) and 43 minutes (DBP) (p < 0.001). SBP and DBP were elevated in the MS-OSA group (hours 18-21 and 7--12, respectively, p < 0.01) compared to controls. The MS-OSA group was prone to "non-dipping" compared to controls (SBP: odds ratio [OR] = 2.16, 95% CI: 1.09, 4.29; DBP: OR = 3.45, 95% CI: 1.21, 10.23).

CONCLUSIONS

Children with MS-OSA had changes in circadian BP patterns, namely earlier TAPV and BP peaks and nadirs than controls. Circadian disturbances in BP rhythms may be key to mapping the natural history of BP dysregulation in children with OSA.

Insights on hexavalent chromium(VI) remediation strategies in abiotic and biotic dual chamber microbial fuel cells: electrochemical, physical, and metagenomics characterizations

Hexavalent chromium [Cr(VI)] is one of the most carcinogenic and mutagenic toxins, and is commonly released into the environemt from different industries, including leather tanning, pulp and paper manufacturing, and metal finishing. This study aimed to investigate the performance of dual chamber microbial fuel cells (DMFCs) equipped with a biocathode as alternative promising remediation approaches for the biological reduction of hexavalent chromium [Cr(VI)] with instantaneous power generation. A succession batch under preliminary diverse concentrations of Cr(VI) (from 5 to 60 mg L-1) was conducted to investigate the reduction mechanism of DMFCs. Compared to abiotic-cathode DMFC, biotic-cathode DMFC exhibited a much higher power density, Cr(VI) reduction, and coulombic efficiency over a wide range of Cr(VI) concentrations (i.e., 5-60 mg L-1). Furthermore, the X-ray photoelectron spectroscopy (XPS) revealed that the chemical functional groups on the surface of biotic cathode DMFC were mainly trivalent chromium (Cr(III)). Additionally, high throughput sequencing showed that the predominant anodic bacterial phyla were Firmicutes, Proteobacteria, and Deinococcota with the dominance of Clostridiumsensu strict 1, Enterobacter, Pseudomonas, Clostridiumsensu strict 11 and Lysinibacillus in the cathodic microbial community. Collectively, our results showed that the Cr(VI) removal occurred through two different mechanisms: biosorption and bioelectrochemical reduction. These findings confirmed that the DMFC could be used as a bioremediation approach for the removal of Cr(VI) commonly found in different industrial wastewater, such as tannery effluents. with simultaneous bioenergy production.

Defining and Promoting Pediatric Pulmonary Health: Understanding Sleep and Ventilatory Health

Healthy sleep and optimal ventilatory control begin in early development and are crucial for positive child outcomes. This paper summarizes information presented at the Sleep and Ventilatory Control sessions of the National Heart, Lung, and Blood-sponsored 2021 Defining and Promoting Pediatric Pulmonary Health workshop. These sessions focused on pediatric sleep health, screening for sleep health and sleep disorders in primary care using the electronic health record, infant sleep and ventilatory control, and home sleep testing. Throughout this summary, we discuss key gaps in and barriers to promoting sleep and ventilatory health that were identified during the workshop sessions. We conclude with strategies to address these gaps and barriers and directions for future multidisciplinary research, patient care, and training.

The Cystic Fibrosis Learning Network: A mixed methods evaluation of program goals, attributes, and impact

Introduction

The Cystic Fibrosis (CF) Foundation sponsored the design, pilot testing, and implementation of the CF Learning Network (CFLN) to explore how the Foundation's Care Center Network (CCN) could become a learning health system. Six years after the design, the Foundation commissioned a formative mixed methods evaluation of the CFLN to assess: CFLN participants' understanding of program goals, attributes, and perceptions of current and future impact.

Methods

We performed semi-structured interviews with CFLN participants to identify perceived goals, attributes, and impact of the network. Following thematic analyses, we developed and distributed a survey to CFLN members and a matched sample of CCN programs to understand whether the themes were unique to the CFLN.

Results

Interviews with 24 CFLN participants were conducted. Interviewees identified the primary CFLN goal as improving outcomes for people living with CF, with secondary goals of providing training in quality improvement (QI), creating a learning community, engaging all stakeholders in improvement, and spreading best practices to the CCN. Project management, use of data, common QI methods, and the learning community were seen as critical to success. Survey responses were collected from 103 CFLN members and 25 CCN members. The data revealed that CFLN respondents were more likely than CCN respondents to connect with other CF programs, routinely use data for QI, and engage patient and family partners in QI.

Conclusions

Our study suggests that the CFLN provides value beyond that achieved by the CCN. Key questions remain about whether spread of the CFLN could improve outcomes for more people living with CF.

Establishing a Cystic Fibrosis Learning Network: Interventions to promote collaboration and data-driven improvement at scale

Introduction

A learning health network is a type of learning health system in which stakeholders use network organization to improve health and health care. Building on existing resources in the cystic fibrosis (CF) community, the Cystic Fibrosis Learning Network (CFLN) was designed to improve medical outcomes and quality of life through an intentional focus on achieving reliable evidence-based chronic care delivery and creating a system for data-driven collaborative learning.

Methods

We describe the development and growth of the CFLN considering six domains of a Network Maturity Grid: system leadership; governance and policy management; quality improvement (QI); engagement and community building; data and analytics; and research. We illustrate the impact of the CFLN experience on chronic care processes and indicators of collaborative infrastructure.

Results

The CFLN represents 36 accredited care centers in the CF Foundation Care Center Network caring for over 6300 patients. Of 6779 patient clinical care visits/quarter, 77% are entered into the CF Foundation Patient Registry within 30 days, providing timely means to track outcomes. Collaborative visit planning is occurring in 93% of clinical care visits to share agenda setting with patients and families. Almost all CFLN teams (94%, n = 34) have a patient/family partner (PFP), and 74% of PFPs indicate they are actively participating, taking ownership of, or leading QI initiatives with the interdisciplinary care team. In 2022, 97% of centers reported completing 1-13 improvement cycles per month, and 82% contributed to monthly QI progress reports to share learning.

Conclusion

The CFLN is a maturing, collaborative infrastructure. CFLN centers practice at an advanced level of coproduction. The CFLN fosters interdisciplinary and PFP leadership and the performance of consistent data-driven improvement cycles. CFLN centers are positioned to respond to rapid changes in evidence-based care and advance the practice of QI and implementation science on a broader scale.

Selenium-transition metal supported on a mixture of reduced graphene oxide and silica template for water splitting

Exploration of economical, highly efficient, and environment friendly non-noble-metal-based electrocatalysts is necessary for hydrogen and oxygen evolution reactions (HER and OER) but challenging for cost-effective water splitting. Herein, metal selenium nanoparticles (M = Ni, Co & Fe) are anchored on the surface of reduced graphene oxide and a silica template (rGO-ST) through a simple one-pot solvothermal method. The resulting electrocatalyst composite can enhance mass/charge transfer and promote interaction between water molecules and electrocatalyst reactive sites. NiSe₂/rGO-ST shows a remarkable overpotential (52.5 mV) at 10 mA cm^-2 for the HER compared to the benchmark Pt/C E-TEK (29 mV), while the overpotential values of CoSeO₃/rGO-ST and FeSe₂/rGO-ST are 246 and 347 mV, respectively. The FeSe₂/rGO-ST/NF shows a low overpotential (297 mV) at 50 mA cm^-2 for the OER compared to RuO₂/NF (325 mV), while the overpotentials of CoSeO₃-rGO-ST/NF and NiSe₂-rGO-ST/NF are 400 and 475 mV, respectively. Furthermore, all catalysts indicate negligible deterioration, indicating better stability during the process of HER and OER after a stability test of 60 h. The water splitting system composed of NiSe₂-rGO-ST/NF||FeSe₂-rGO-ST/NF electrodes requires only ∼1.75 V at 10 mA cm^-2. Its performance is nearly close to that of a noble metal-based Pt/C/NF||RuO₂/NF water splitting system.

Comparison of Caregiver- and Child-Reported Quality of Life in Children With Sleep-Disordered Breathing

OBJECTIVE

Caregivers frequently report poor quality of life (QOL) in children with sleep-disordered breathing (SDB). Our objective is to assess the correlation between caregiver- and child-reported QOL in children with mild SDB and identify factors associated with differences between caregiver and child report.

STUDY DESIGN

Analysis of baseline data from a multi-institutional randomized trial SETTING: Pediatric Adenotonsillectomy Trial for Snoring, where children with mild SDB (obstructive apnea-hypopnea index <3) were randomized to observation or adenotonsillectomy.

METHODS

The Pediatric Quality of Life Inventory (PedsQL) assessed baseline global QOL in participating children 5 to 12 years old and their caregivers. Caregiver and child scores were compared. Multivariable regression assessed whether clinical factors were associated with differences between caregiver and child report.

RESULTS

PedsQL scores were available for 309 families (mean child age, 7.0 years). The mean caregiver-reported PedsQL score was higher at 75.2 (indicating better QOL) than the mean child-reported score of 67.9 (P < .001). The agreement between caregiver and child total PedsQL scores was poor, with intraclass correlation coefficients of 0.03 (95% CI, -0.09 to 0.15) for children 5 to 7 years old and 0.21 (95% CI, 0.03-0.38) for children 8 to 12 years old. Higher child age and health literacy were associated with closer agreement between caregiver and child report.

CONCLUSION

Caregiver- and child-reported global QOL in children with SDB was weakly correlated, more so for young children. In pediatric SDB, child-perceived QOL may be poorer than that reported by caregivers. Further research is needed to assess whether similar trends exist for disease-specific QOL metrics.

Improving Home Ventilator Alarm Use Among Children Requiring Chronic Mechanical Ventilation

BACKGROUND AND OBJECTIVES

Children requiring long-term mechanical ventilation are at high risk of mortality. Setting ventilator alarms may improve safety, but best practices for setting ventilator alarms have not been established. Our objective was to increase the mean proportion of critical ventilator alarms set for those children requiring chronic mechanical ventilation followed in our pulmonary clinic from 63% to >90%.

METHODS

Using the Institute for Healthcare Improvement Model for Improvement, we developed, tested, and implemented a series of interventions using Plan-Do-Study-Act cycles. We followed our progress using statistical process control methods. Our primary interventions were: (1) standardization of the clinic workflow, (2) development of an algorithm to guide physicians in selecting and setting ventilator alarms, (3) updating that algorithm based on review of failures and inpatient testing, and (4) enhancing staff engagement to change the culture surrounding ventilator alarms.

RESULTS

We collected baseline data from May 1 to July 13, 2017 on 130 consecutive patients seen in the pulmonary medicine clinic. We found that 63% of critical ventilator alarms were set. Observation of the process, standardization of workflow, and adaptation of an alarm algorithm led to an increase to 85.7% of critical alarms set. Through revising our algorithm to include an apnea alarm, and maximizing provider engagement, more than 95% of critical ventilator alarms were set, exceeding our goal. We sustained this improvement through January 2021.

CONCLUSIONS

Our stepwise approach, including process standardization, staff engagement, and integration of an alarm algorithm, improved the use of ventilator alarms in chronically ventilated pediatric patients.

Cystic fibrosis learning network telehealth innovation lab during the COVID-19 pandemic: a success QI story for interdisciplinary care and agenda setting

INTRODUCTION

The Cystic Fibrosis Foundation chronic care guidelines recommend monitoring clinical status of a patient with cystic fibrosis (CF) through quarterly interdisciplinary visits. At the beginning of the COVID-19 pandemic, the Cystic Fibrosis Learning Network (CFLN) designed and initiated a telehealth (TH) innovation lab (TH ILab) to support transition from the classic CF care model of quarterly in-person office visits to a care model that included TH.

AIM

The specific aims of the TH ILab were to increase the percentage of virtual visits with interdisciplinary care (IDC) from 60% to 85% and increase the percentage of virtual visits in which patients and families participated in shared agenda setting (AS) from 52% to 85% by 31 December 2020.

METHODS

The model for improvement methodology was used to determine the ILab aims, theory, interventions and measures. In the testing phase of the ILab, data related to process and outcome measures as well as learnings from plan-do-study-act cycles were collected, analysed and shared weekly with the TH ILab teams. Participating centres created processes for IDC and AS for TH visits and developed and shared quality improvement tools specific to their local context with other centres during the ILab weekly meetings and via a secure CFLN-maintained platform.

RESULTS

Both specific aims were achieved ahead of the expected target date. By August 2020, 85% of the TH ILab visits provided IDC and 92% of patients were seen for CF care by teams from the TH ILab that participated in AS.

CONCLUSION

Shared learning through a collaborative, data-driven process in the CFLN TH ILab rapidly led to standardised TH IDC and AS, which achieved reliable and sustainable processes which could be reproduced by other networks.

Neurobehavioral morbidity of pediatric mild sleep-disordered breathing and obstructive sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea is associated with neurobehavioral dysfunction, but the relationship between disease severity as measured by the apnea-hypopnea index and neurobehavioral morbidity is unclear. The objective of our study is to compare the neurobehavioral morbidity of mild sleep-disordered breathing versus obstructive sleep apnea.

METHODS

Children 3-12 years old recruited for mild sleep-disordered breathing (snoring with obstructive apnea-hypopnea index < 3) into the Pediatric Adenotonsillectomy Trial for Snoring were compared to children 5-9 years old recruited for obstructive sleep apnea (obstructive apnea-hypopnea 2-30) into the Childhood Adenotonsillectomy Trial. Baseline demographic, polysomnographic, and neurobehavioral outcomes were compared using univariable and multivariable analysis.

RESULTS

The sample included 453 participants with obstructive sleep apnea (median obstructive apnea-hypopnea index 5.7) and 459 participants with mild sleep-disordered breathing (median obstructive apnea-hypopnea index 0.5). By polysomnography, participants with obstructive sleep apnea had poorer sleep efficiency and more arousals. Children with mild sleep-disordered breathing had more abnormal executive function scores (adjusted odds ratio 1.96, 95% CI 1.30-2.94) compared to children with obstructive sleep apnea. There were also elevated Conners scores for inattention (adjusted odds ratio 3.16, CI 1.98-5.02) and hyperactivity (adjusted odds ratio 2.82, CI 1.83-4.34) in children recruited for mild sleep-disordered breathing.

CONCLUSIONS

Abnormal executive function, inattention, and hyperactivity were more common in symptomatic children recruited into a trial for mild sleep-disordered breathing compared to children recruited into a trial for obstructive sleep apnea. Young, snoring children with only minimally elevated apnea-hypopnea levels may still be at risk for deficits in executive function and attention.

TRIAL REGISTRATION

Pediatric Adenotonsillectomy for Snoring (PATS), NCT02562040; Childhood Adenotonsillectomy Trial (CHAT), NCT00560859.

Evaluation of mixed transition metal (Co, Mn, and Cu) oxide electrocatalysts anchored on different carbon supports for robust oxygen reduction reaction in neutral media

Oxygen reduction reaction (ORR) remains a pivotal factor in assessing the overall efficiency of energy conversion and storage technologies. A promising family of ORR electrocatalysts is mixed transition-metal oxides (MTMOs), which have recently gained a growing research interest. In this study, we developed MTMOs with different compositions (designated as A_xB_3−xO₄; A = Cu, B = Co or Mn) anchored on two different carbon supports (activated carbon Vulcan XC-72 (AC) and graphene (G)) for catalyzing ORR in neutral media. Four different MTMO electrocatalysts (i.e., MnO₂–CuO/AC, CoO–CuO/AC, CoO–CuO/G, and MnO₂–CuO/G) were synthesized by a simple and scalable co-precipitation method. We documented the morphology and electrocatalytic properties of MTMO electrocatalysts using transmission and scanning electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectrometer (XPS), energy dispersive X-ray (EDX), and electrochemical techniques. Generally, MTMOs exhibited remarkably high ORR electrocatalytic activity with MTMOs anchored on an activated carbon support outperforming their respective MTMOs anchored on a graphene support, highlighting the importance of the catalyst support in determining the overall ORR activity of electrocatalysts. MnO₂–CuO/AC has the highest diffusion limiting current density (j) value of 4.2 mA cm⁻² at −600 mV (vs. SHE), which is ∼1.1–1.7-fold higher than other tested electrocatalysts (i.e., 3.9, 3.5, and 2.7 mA cm⁻² for CoO–CuO/AC, CoO–CuO/G, and MnO₂–CuO/G, respectively), and slightly lower than Pt/C (5.1 mA cm⁻²) at the same potential value. Moreover, all electrocatalysts exhibited good linearity and parallelism of the Koutechy–Levich (K–L) plots, suggesting that ORR followed first-order reaction kinetics with the number of electrons involved being close to four. Benefiting from their remarkable ORR electrochemical activities and low cost, our results reveal that non-precious MTMOs are efficient enough to replace expensive Pt for broad applications in energy conversion and electrocatalysis in neutral media, such as microbial fuel cells.

Mixed transition metal (Co, Mn, and Cu) oxide electrocatalysts anchored on different carbon supports for oxygen reduction reaction.

Human upper-airway respiratory airflow: In vivo comparison of computational fluid dynamics simulations and hyperpolarized 129Xe phase contrast MRI velocimetry

Computational fluid dynamics (CFD) simulations of respiratory airflow have the potential to change the clinical assessment of regional airway function in health and disease, in pulmonary medicine and otolaryngology. For example, in diseases where multiple sites of airway obstruction occur, such as obstructive sleep apnea (OSA), CFD simulations can identify which sites of obstruction contribute most to airway resistance and may therefore be candidate sites for airway surgery. The main barrier to clinical uptake of respiratory CFD to date has been the difficulty in validating CFD results against a clinical gold standard. Invasive instrumentation of the upper airway to measure respiratory airflow velocity or pressure can disrupt the airflow and alter the subject's natural breathing patterns. Therefore, in this study, we instead propose phase contrast (PC) velocimetry magnetic resonance imaging (MRI) of inhaled hyperpolarized 129Xe gas as a non-invasive reference to which airflow velocities calculated via CFD can be compared. To that end, we performed subject-specific CFD simulations in airway models derived from 1H MRI, and using respiratory flowrate measurements acquired synchronously with MRI. Airflow velocity vectors calculated by CFD simulations were then qualitatively and quantitatively compared to velocity maps derived from PC velocimetry MRI of inhaled hyperpolarized 129Xe gas. The results show both techniques produce similar spatial distributions of high velocity regions in the anterior-posterior and foot-head directions, indicating good qualitative agreement. Statistically significant correlations and low Bland-Altman bias between the local velocity values produced by the two techniques indicates quantitative agreement. This preliminary in vivo comparison of respiratory airway CFD and PC MRI of hyperpolarized 129Xe gas demonstrates the feasibility of PC MRI as a technique to validate respiratory CFD and forms the basis for further comprehensive validation studies. This study is therefore a first step in the pathway towards clinical adoption of respiratory CFD.

Quantitative Evaluation of Subglottic Stenosis Using Ultrashort Echo Time MRI in a Rabbit Model

OBJECTIVE/HYPOTHESIS

To assess the ability of ultra-short echo time (UTE)-MRI to detect subglottic stenosis (SGS) and evaluate response to balloon dilation. To correlate measurements from UTE-MRI with endotracheal-tube (ETT)-sizing and to investigate whether SGS causes change in airway dynamics.

STUDY DESIGN

Animal research study.

METHODS

Eight adult New-Zealand white rabbits were used as they approximate neonatal airway-size. The airways were measured using ETT-sizing and 3D UTE-MRI at baseline, 2 weeks post-cauterization induced SGS injury, and post-balloon dilation treatment. UTE-MR images were acquired to determine airway anatomy and motion. Airways were segmented from MR images. Cross-sectional area (CSA), major and minor diameters (D_major and D_minor ), and eccentricity were measured.

RESULTS

Post-injury CSA at SGS was significantly reduced (mean 38%) compared to baseline (P = .003) using UTE-MRI. ETT-sizing correlated significantly with MRI-measured CSA at the SGS location (r = 0.6; P < .01), particularly at the post-injury timepoint (r = 0.93; P < .01). Outer diameter from ETT-sizing (OD) correlated significantly with D_major (r = 0.63; P < .01) from UTE-MRI at the SGS location, especially for the post-injury timepoint (r = 0.91; P < .01). Mean CSA of upper trachea did not change significantly between end-expiration and end-inspiration at any timepoint (all P > .05). Eccentricity of the upper trachea increased significantly post-balloon dilation (P < .05).

CONCLUSIONS

UTE-MRI successfully detected SGS and treatment response in the rabbit model, with good correlation to ETT-sizing. Balloon dilation increased CSA at SGS, but not to baseline values. SGS did not alter dynamic motion for the trachea in this rabbit model; however, tracheas were significantly eccentric post-balloon dilation. UTE-MRI can detect SGS without sedation or ionizing radiation and may be a non-invasive alternative to ETT-sizing.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:E1971-E1979, 2021.

Effects on the Upper Airway Morphology with Intravenous Addition of Ketamine after Dexmedetomidine Administration in Normal Children

General anesthesia decreases the tone of upper airway muscles in a dose-dependent fashion, potentially narrowing the pharyngeal airway. We examined the effects of adding ketamine on the airway configuration after dexmedetomidine administration in spontaneously breathing children with normal airways. 25 children presenting for Magnetic Resonance Imaging (MRI) of the brain/spine under general anesthesia were prospectively recruited in the study. Patients were anesthetized with dexmedetomidine bolus (2 mcg over 10 min) followed by dexmedetomidine infusion (2 mcg·kg−1·h) and ketamine and permitted to breathe spontaneously via the native airway. MR-CINE images of the upper airway were obtained with dexmedetomidine infusion alone (baseline) and 5, 10, and 15 min after administering ketamine bolus (2 mg·kg−1) in two anatomical axial planes at the nasopharynx and the retroglossal upper airway. Airway lumen is segmented with a semi-automatic image processing approach using a region-growing algorithm. Outcome measures of cross-sectional area, transverse and anterior-posterior diameters of the airway in axial planes at the level of the epiglottis in the retroglossal airway, and in the superior nasopharynx were evaluated for changes in airway size with sedation. Airway dimensions corresponding to the maximum, mean, and minimum sizes during a respiratory cycle were obtained to compare the temporal changes in the airway size. The dose-response of adding ketamine to dexmedetomidine alone condition on airway dimensions were examined using mixed-effects of covariance models. 22/25 patients based on inclusion/exclusion criteria were included in the final analysis. The changes in airway measures with the addition of ketamine, when compared to the baseline of dexmedetomidine alone, were statistically insignificant. The modest changes in airway dimensions are clinically less impactful and within the accuracy of the semi-automatic airway segmentation approach. The effect sizes were small for most airway measures. The duration of ketamine seems to not affect the airway size. In conclusion, adding ketamine to dexmedetomidine did not significantly reduce upper airway configuration when compared to dexmedetomidine alone.

Subglottic Stenosis Position Affects Work of Breathing

OBJECTIVES

Subglottic stenosis (SGS) is the most common type of laryngeal stenosis in neonates. SGS severity is currently graded based on percent area of obstruction (%AO) via the Myer-Cotton grading scale. However, patients with similar %AO can have widely different clinical courses. Computational fluid dynamics (CFD) based on patient-specific imaging can quantify the relationship between airway geometry and flow dynamics. We investigated the effect of %AO and axial position of SGS on work of breathing (WOB) in neonates using magnetic resonance imaging.

METHODS

High-resolution ultrashort echo-time MRI of the chest and airway was obtained in three neonatal patients with no suspected airway abnormalities; images were segmented to construct three-dimensional (3D) models of the neonatal airways. These models were then modified with virtual SGSs of varying %AO and axial positioning. CFD simulations of peak inspiratory flow were used to calculate patient-specific WOB in nonstenotic and artificially stenosed airway models.

RESULTS

CFD simulations demonstrated a relationship between stenosis geometry and WOB increase. WOB rapidly increased with %AO greater than about 70%. Changes in axial position could also increase WOB by approximately the same amount as a 10% increase in %AO. Increased WOB was particularly pronounced when the SGS lumen was misaligned with the glottic jet.

CONCLUSION

The results indicate a strong, predictable relationship between WOB and axial position of the stenotic lumen relative to the glottis, which has not been previously reported. These findings may lead to precision diagnosis and treatment prediction tools in individual patients.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E1220-E1226, 2021.

Assessing ventilatory instability using the response to spontaneous sighs during sleep in preterm infants

Study Objectives

Periodic breathing (PB) is common in newborns and is an obvious manifestation of ventilatory control instability. However, many infants without PB may still have important underlying ventilatory control instabilities that go unnoticed using standard clinical monitoring. Methods to detect infants with "subclinical" ventilatory control instability are therefore required. The current study aimed to assess the degree of ventilatory control instability using simple bedside recordings in preterm infants.

Methods

Respiratory inductance plethysmography (RIP) recordings were analyzed from ~20 minutes of quiet sleep in 20 preterm infants at 36 weeks post-menstrual age (median [range]: 36 [34-40]). The percentage time spent in PB was also calculated for each infant (%PB). Spontaneous sighs were identified and breath-by-breath measurements of (uncalibrated) ventilation were derived from RIP traces. Loop gain (LG, a measure of ventilatory control instability) was calculated by fitting a simple ventilatory control model (gain, time-constant, delay) to the post-sigh ventilatory pattern. For comparison, periodic inter-breath variability was also quantified using power spectral analysis (ventilatory oscillation magnitude index [VOMI]).

Results

%PB was strongly associated with LG (r2 = 0.77, p < 0.001) and moderately with the VOMI (r2 = 0.21, p = 0.047). LG (0.52 ± 0.05 vs. 0.30 ± 0.03; p = 0.0025) and the VOMI (-8.2 ± 1.1 dB vs. -11.8 ± 0.9 dB; p = 0.026) were both significantly higher in infants that displayed PB vs. those without.

Conclusions

LG and VOMI determined from the ventilatory responses to spontaneous sighs can provide a practical approach to assessing ventilatory control instability in preterm infants. Such simple techniques may help identify infants at particular risk for ventilatory instabilities with concomitant hypoxemia and its associated consequences.

Assessing the relationship between movement and airflow in the upper airway using computational fluid dynamics with motion determined from magnetic resonance imaging

BACKGROUND

Computational fluid dynamics simulations of respiratory airflow in the upper airway reveal clinically relevant information, including sites of local resistance, inhaled particle deposition, and the effect of pathological constrictions. Unlike previous simulations, which have been performed on rigid anatomical models from static medical imaging, this work utilises ciné imaging during respiration to create dynamic models and more closely represent airway physiology.

METHODS

Airway movement maps were obtained from non-rigid image registration of fast-cine MRI and applied to high-spatial-resolution airway surface models. Breathing flowrates were recorded simultaneously with imaging. These data formed the boundary conditions for large eddy simulation computations of the airflow from exterior mask to bronchi. Simulations with rigid geometries were performed to demonstrate the resulting airflow differences between airflow simulations in rigid and dynamic airways.

FINDINGS

In the analysed rapid breathing manoeuvre, incorporating airway movement significantly changed the findings of the CFD simulations. Peak resistance increased by 19.8% and occurred earlier in the breath. Overall pressure loss decreased by 19.2%, and the proportion of flow in the mouth increased by 13.0%. Airway wall motion was out-of-phase with the air pressure force, demonstrating the presence of neuromuscular motion. In total, the anatomy did 25.2% more work on the air than vice versa.

INTERPRETATIONS

Realistic movement of the airway is incorporated into CFD simulations of airflow in the upper airway for the first time. This motion is vital to producing clinically relevant computational models of respiratory airflow and will allow novel analysis of dynamic conditions, such as sleep apnoea.

OSA and Cardiovascular Risk in Pediatrics

OSA occurs in approximately 1% to 5% of children in the United States. Long-term cardiovascular risks associated with OSA in the adult population are well documented. Although changes in BP regulation occur in children with OSA, the pathways leading to chronic cardiovascular risks of OSA in children are less clear. Risk factors associated with cardiovascular disease in adult populations could carry the same future risk for children. It is imperative to determine whether known mechanisms of cardiovascular diseases in adults are like those that lead to pediatric disease. Early pathophysiologic changes may lead to a lifetime burden of cardiovascular disease and early mortality. With this perspective in mind, our review discusses pathways leading to cardiovascular pathology in children with OSA and provides a comprehensive overview of recent research findings related to cardiovascular sequelae in the pediatric population.

A novel method to generate dynamic boundary conditions for airway CFD by mapping upper airway movement with non-rigid registration of dynamic and static MRI

Computational fluid dynamics (CFD) simulations of airflow in the human airways have the potential to provide a great deal of information that can aid clinicians in case management and surgical decision making, such as airway resistance, energy expenditure, airflow distribution, heat and moisture transfer, and particle deposition, as well as the change in each of these due to surgical interventions. However, the clinical relevance of CFD simulations has been limited to date, as previous models either did not incorporate neuromuscular motion or any motion at all. Many common airway pathologies, such as obstructive sleep apnea (OSA) and tracheomalacia, involve large movements of the structures surrounding the airway, such as the tongue and soft palate. Airway wall motion may be due to many factors including neuromuscular motion, internal aerodynamic forces, and external forces such as gravity. Therefore, to realistically model these airway diseases, a method is required to derive the airway wall motion, whatever the cause, and apply it as a boundary condition to CFD simulations. This paper presents and validates a novel method of capturing in vivo motion of airway walls from magnetic resonance images with high spatiotemporal resolution, through a novel combination of non-rigid image, surface, and surface-normal-vector registration. Coupled with image-synchronous pneumotachography, this technique provides the necessary boundary conditions for dynamic CFD simulations of breathing, allowing the effect of the airway's complex motion to be calculated for the first time, in both normal subjects and those with conditions such as OSA.

Circadian Dysregulation: The Next Frontier in Obstructive Sleep Apnea Research

OBJECTIVE

To review the effects of the circadian clock on homeostasis, the functional interaction between the circadian clock and hypoxia-inducible factors, and the role of circadian dysregulation in the progression of cardiopulmonary disease in obstructive sleep apnea (OSA).

DATA SOURCES

The MEDLINE database was accessed through PubMed.

REVIEW METHODS

A general review is presented on molecular pathways disrupted in OSA, circadian rhythms and the role of the circadian clock, hypoxia signaling, crosstalk between the circadian and hypoxia systems, the role of the circadian clock in cardiovascular disease, and implications for practice. Studies included in this State of the Art Review demonstrate the potential contribution of the circadian clock and hypoxia in animal models or human disease.

CONCLUSIONS

Molecular crosstalk between the circadian clock and hypoxia-inducible factors has not been evaluated in disease models of OSA.

IMPLICATIONS FOR PRACTICE

Pediatric OSA is highly prevalent and, if left untreated, may lead to cardiopulmonary sequelae. Changes in inflammatory markers that normally demonstrate circadian rhythmicity are also seen among patients with OSA. Hypoxia-inducible transcription factors interact with core circadian clock transcription factors; however, the interplay between these pathways has not been elucidated in the cardiopulmonary system. This gap in knowledge hinders our ability to identify potential biomarkers of OSA and develop alternative therapeutic strategies. A deeper understanding of the mechanisms by which OSA impinges on clock function and the impact of clock dysregulation on the cardiopulmonary system may lead to future advancements for the care of patients with OSA. The aim of this review is to shed light on this important clinical topic.

Magnetic resonance imaging of obstructive sleep apnea in children

Sleep-disordered breathing has a spectrum of severity that spans from snoring and partial airway collapse with increased upper airway resistance, to complete upper airway obstruction with obstructive sleep apnea during sleeping. While snoring occurs in up to 20% of children, obstructive sleep apnea affects approximately 1-5% of children. The obstruction that occurs in obstructive sleep apnea is the result of the airway collapsing during sleep, which causes arousal and impairs restful sleep. Adenotonsillectomy is the first-line treatment of obstructive sleep apnea and is usually effective in otherwise healthy nonsyndromic children. However, there are subgroups in which this surgery is less effective. These subgroups include children with obesity, severe obstructive sleep apnea preoperatively, Down syndrome, craniofacial anomalies and polycystic ovarian disease. Continuous positive airway pressure (CPAP) is the first-line therapy for persistent obstructive sleep apnea despite previous adenotonsillectomy, but it is often poorly tolerated by children. When CPAP is not tolerated or preferred by the family, surgical options beyond adenotonsillectomy are discussed with the parent and child. Dynamic MRI of the airway provides a means to identify and localize the site or sites of obstruction for these children. In this review the authors address clinical indications for imaging, ideal team members to involve in an effective multidisciplinary program, basic anesthesia requirements, MRI protocol techniques and interpretation of the findings on MRI that help guide surgery.

Cardioventilatory Control in Preterm-born Children and the Risk of Obstructive Sleep Apnea

RATIONALE

The contribution of ventilatory control to the pathogenesis of obstructive sleep apnea (OSA) in preterm-born children is unknown.

OBJECTIVES

To characterize phenotypes of ventilatory control that are associated with the presence of OSA in preterm-born children during early childhood.

METHODS

Preterm- and term-born children without comorbid conditions were enrolled. They were categorized into an OSA group and a non-OSA group on the basis of polysomnography.

MEASUREMENTS AND MAIN RESULTS

Loop gain, controller gain, and plant gain, reflecting ventilatory instability, chemoreceptor sensitivity, and blood gas response to a change in ventilation, respectively, were estimated from spontaneous sighs identified during polysomnography. Cardiorespiratory coupling, a measure of brainstem maturation, was estimated by measuring the interval between inspiration and the preceding electrocardiogram R-wave. Cluster analysis was performed to develop phenotypes based on controller gain, plant gain, cardiorespiratory coupling, and gestational age. The study included 92 children, 63 of whom were born preterm (41% OSA) and 29 of whom were born at term (48% OSA). Three phenotypes of ventilatory control were derived with risks for OSA being 8%, 47%, and 77% in clusters 1, 2, and 3, respectively. There was a stepwise decrease in controller gain and an increase in plant gain from clusters 1 to 3. Children in cluster 1 had significantly higher cardiorespiratory coupling and gestational age than clusters 2 and 3. No difference in loop gain was found between clusters.

CONCLUSIONS

The risk for OSA could be stratified according to controller gain, plant gain, cardiorespiratory coupling, and gestational age. These findings could guide personalized care for children at risk for OSA.

Inflammatory Milieu and Cardiovascular Homeostasis in Children With Obstructive Sleep Apnea

Introduction

Biomarkers of atherosclerosis (pro-inflammatory cytokines and acute phase reactants) are elevated in children with obstructive sleep apnea (OSA). However, their association with cardiovascular endpoints in children are not understood. We hypothesized that biomarkers of atherosclerosis in children with OSA correlate with pulse transit time (PTT), a surrogate measure of vascular stiffness, with some positively influencing and others negatively influencing PTT.

Methods

Children with OSA and matched controls were recruited to the study. Pro-inflammatory cytokines and acute phase reactants were measured at 6:00 pm and 6:00 am. Polysomnography with beat-to-beat blood pressure was performed. PTT during wakefulness and stage 2 sleep was calculated. Diurnal variation of biomarkers and their associations with PTT was estimated. Factor analysis was used to determine the effect of groups of cytokines on PTT.

Results

One hundred fifty-five children participated in the study; 90 were healthy controls and 65 had OSA. Children with OSA exhibited a different diurnal variation of biomarkers than healthy controls, with pro-inflammatory cytokines peaking in the morning and acute phase reactants peaking in the afternoon. Structural equation modeling demonstrated that interleukins 6 and 8, tumor necrosis factor-α, and sCD40L had a shortening effect, while serum amyloid A, C-reactive protein, and adiponectin had a prolonging effect on PTT. As a result, there was no difference in PTT between the two groups.

Conclusion

The differential relationships of acute phase reactants and pro-inflammatory cytokines with PTT suggest that in children with OSA, these mediators may have opposing actions to maintain cardiovascular homeostasis.

Adherence and barriers to hyperinsufflation in children with congenital muscular dystrophy

BACKGROUND

Congenital muscular dystrophy (CMD) is a rare, inherited neuromuscular disease characterized by progressive muscle weakness, thoracic insufficiency, and ultimately respiratory failure. Adherence to respiratory therapies in children with neuromuscular disorders is unknown. This study examined the multimodal assessment of adherence and barriers to 15 min, twice daily hyperinsufflation in children with CMD. Adherence was hypothesized to be greater than 50% and discomfort, embarrassment, and difficulty finding time were hypothesized to be barriers.

METHODS

Participants included 18 children with CMD. Personalized hyperinsufflation settings were determined based on pressure-volume measurements at each study visit. Adherence was measured by a daily phone diary (DPD) and by electronic data download from the hyperinsufflation device. The DPD was conducted twice over a 48-hr period to capture a weekend and weekday, with the goal being 60 min of hyperinsufflation over the 48 hr (100% adherence). The hyperinsufflation objective electronic data reflected daily use of hyperinsufflation for the same 48-hr period. Data from DPD and the corresponding hyperinsufflation device data were used for analyses.

RESULTS

Adherence to hyperinsufflation was 40% via DPD and 44% for electronic data, with strong convergence between methods (r = 0.75, P < 0.001). Surprisingly, 53% of participants reported no barriers despite low adherence. Social distractions and family obligations were identified as barriers. There were no differences in adherence between those who did and did not endorse barriers to hyperinsufflation (DPD: t(13) = 0.44, P = n.s.; hyperinsufflation device: t(13) = -0.23, P = n.s.).

CONCLUSION

Adherence to hyperinsufflation is a significant problem in children with CMD and families have difficulty identifying adherence barriers. An important next step is to encourage open dialog around adherence barriers and promote adherence behaviors via intervention. Pediatr Pulmonol. 2017; 52:939-945. © 2016 Wiley Periodicals, Inc.

Longitudinal Cardiovascular Outcomes of Sleep Disordered Breathing in Children: A Meta-Analysis and Systematic Review

Objectives

The presence of sleep disordered breathing (SDB) is known to impact long-term cardiovascular morbidity in adults; however, the long-term effects in children are poorly understood. We aimed to systematically review and synthesize studies published to date on the long-term effects of SDB in children.

Study Design

Meta-analysis and systematic review using PubMed, CINAHL, Embase, and Scopus (all indexed years).

Methods

We searched for English-language articles containing original human data from prospective studies, with ≥7 participants, in children ≤18 years of age. Data regarding study design, demographics, clinical characteristics, outcomes, level of evidence, and risk of bias were obtained. Articles were independently reviewed by three investigators. Retrospective and cross-sectional studies were excluded.

Results

Of 1701 identified abstracts, 25 articles (combined n = 1418) were ultimately included. All studies reported longitudinal outcomes following treatment of SDB, 21 studies exclusively reporting outcomes after adenotonsillectomy. Therefore, studies were combined to objectively assess the effect of SDB treatment on cardiovascular outcomes. Although all cardiovascular parameters were within the normal range at baseline, at follow-up there was a significant decrease in mean pulmonary artery pressure, right ventricular end diastolic diameter, heart rate, mitral Em/Am ratio, and C-reactive protein. There was no significant change in interventricular septum thickness, left ventricular parameters (shortening fraction, systolic and end diastolic diameters, ejection fraction, posterior wall thickness, isovolumetric relaxation time), left atrial diameter, and aortic and pulmonary valve peak velocities.

Conclusions

Studies assessing the long-term cardiovascular effects of SDB in children are limited. The available literature indicates effects on autonomic function, right, and left heart function following treatment for SDB. However, well-designed, large-scale, prospective cohort studies (using standardized outcomes) are needed to better understand the relationship of cardiovascular morbidity in the context of pediatric SDB.

Upper Airway Reflexes are Preserved During Dexmedetomidine Sedation in Children With Down Syndrome and Obstructive Sleep Apnea

STUDY OBJECTIVES

The assessment of pharyngeal collapsibility is difficult to perform in children under normal sleep. An alternative is to perform the assessment under an anesthetic, such as dexmedetomidine (DEX), that induces non-rapid eye movement (NREM) sleep. The objectives of this study were to compare critical closing airway pressure (Pcrit) obtained during natural sleep to that obtained under DEX in patients with Down syndrome (DS) and persistent obstructive sleep apnea (OSA) and determine whether Pcrit measured under sedation predicts the severity of OSA.

METHODS

The passive and active Pcrit, which represent airway passive mechanical properties and active dynamic responses to airway obstruction, respectively, were measured. Upper airway reflex activity was estimated by calculating the difference between active and passive Pcrit. Subjects underwent overnight polysomnography during which Pcrit was measured during normal sleep. Pcrit was also measured during DEX sedation at a dose of 2 μg/kg/h.

RESULTS

The study included 50 patients with median age of 11.4 years (interquartile range: 7.0-13.9) and median body mass index of 23.0 kg/m² (interquartile range: 18.4-29.1), 66% male and 80% Caucasian. Passive Pcrit was significantly higher than active Pcrit when measured during normal sleep and DEX-induced sleep. There was a positive association between apnea-hypopnea index and passive Pcrit (Spearman r = 0.53, P = .0001) and active Pcrit (r = 0.55, P = .0002) under DEX-induced sleep. There were no significant differences between the Pcrit measurements during natural sleep and during DEX sedation.

CONCLUSION

Patients with OSA can compensate for airway obstruction under DEX-induced sleep. The close association between Pcrit and apnea-hypopnea index suggests that airway responses with DEX sedation parallel those seen during natural sleep.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01902407.

Dynamic Volume Computed Tomography Imaging of the Upper Airway in Obstructive Sleep Apnea

STUDY OBJECTIVES

To describe a dynamic three-dimensional (3D) computed tomography (CT) technique for the upper airway and compare the required radiation dose to that used for common clinical studies of a similar anatomical area, such as for subjects undergoing routine clinical facial CT.

METHODS

Dynamic upper-airway CT was performed on eight subjects with persistent obstructive sleep apnea, four of whom were undergoing magnetic resonance imaging and an additional four subjects who had a contraindication to magnetic resonance imaging. This Health Insurance Portability and Accountability Act-compliant study was approved by our institutional review board, and informed consent was obtained. The control subjects (n = 41) for comparison of radiation dose were obtained from a retrospective review of the clinical picture-archiving computer system to identify 10 age-matched patients per age-based control group undergoing facial CT.

RESULTS

Dynamic 3D CT can be performed with an effective radiation dose of less than 0.38 mSv, a dose that is less than or comparable to that used for clinical facial CT. The resulting data- set is a uniquely complete, dynamic 3D volume of the upper airway through a full respiratory cycle that can be processed for clinical and modeling analyses.

CONCLUSIONS

A dynamic 3D CT technique of the upper airway is described that can be performed with a clinically reasonable radiation dose and sets a benchmark for future use.

Computational Modeling of Airway Obstruction in Sleep Apnea in Down Syndrome: A Feasibility Study

Current treatment options are successful in 40% to 60% of children with persistent obstructive sleep apnea after adenotonsillectomy. Residual obstruction assessments are largely subjective and do not clearly define multilevel obstruction. We endeavor to use computational fluid dynamics to perform virtual surgery and assess airflow changes in patients with Down syndrome and persistent obstructive sleep apnea. Three-dimensional airway models were reconstructed from respiratory-gated computed tomography and magnetic resonance imaging. Virtual surgeries were performed on 10 patients, mirroring actual surgeries. They demonstrated how surgical changes affect airflow resistance. Airflow and upper airway resistance was calculated from computational fluid dynamics. Virtual and actual surgery outcomes were compared with obstructive apnea-hypopnea index values. Actual surgery successfully treated 6 of 10 patients (postoperative obstructive apnea-hypopnea index <5). In 8 of 10 subjects, both apnea-hypopnea index and the calculated upper airway resistance after virtual surgery decreased as compared with baseline values. This is a feasibility and proof-of-concept study. Further studies are needed before using these techniques in surgical planning.

Influence of Metal Oxides on Platinum Activity towards Methanol Oxidation in H2SO4 solution

Pt-CeO2 /C, Pt-TiO2 /C, and Pt-ZrO2 /C electrocatalysts were prepared by using a modified microwave-assisted polyol process. Physical characterization was performed by using XRD, TEM, and EDX analyses. The incorporation of different metal oxides increased the dispersion degree of Pt nanoparticles and reduced their diameter to 2.50 and 2.33 nm when TiO2 and ZrO2 were introduced to Pt/C, respectively. The electrocatalytic activity of various electrocatalysts was examined towards methanol oxidation in H2 SO4 solution by using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Among the studied composites, Pt-ZrO2 /C was selected to be a candidate electrocatalyst for better electrochemical performance in direct methanol fuel cells.

Semiparametric Mixed Models for Nested Repeated Measures Applied to Ambulatory Blood Pressure Monitoring Data

Semiparametric mixed models are increasingly popular for statistical analysis of medical device studies in which long sequences of repeated measurements are recorded. Monitoring these sequences at different periods over time on the same individual, such as before and after an intervention, results in nested repeated measures (NRM). Covariance models to account for NRM and simultaneously address mean profile estimation with penalized splines via semiparametric regression are considered with application to a prospective study of 24-hour ambulatory blood pressure and the impact of surgical intervention on obstructive sleep apnea.

Decision Making for Children with Obstructive Sleep Apnea without Tonsillar Hypertrophy

Objective

Evidence-based medicine is the gold standard practice model for patient management. Our aim was to determine whether decisions made by pediatric subspecialists regarding management of obstructive sleep apnea in children without tonsillar hypertrophy adhered to this model or were based on clinical experiences.

Study Design

Single-institution prospective study.

Setting

Multidisciplinary upper airway center in an academic pediatric hospital.

Subjects and Methods

Twelve pediatric subspecialists representing 8 specialties participating in upper airway clinics and management conferences. Real-time decisions made in treatment conferences and upper airway clinics were collected. Physicians were queried regarding the basis of their decisions, and these decisions were then classified into 10 categories.

Results

Over 13 days (10 case conferences, 3 half-day clinics), 324 decisions were made for 58 patients (mean age = 8.9 ± 7.4 years, mean body mass index percentile = 75 ± 29); 34% (n = 108) of decisions were evidence based; 59% (n = 193) were nonevidence based; and 7% (n = 23) were based on parental preference. Providers were able to cite specific studies for <20% of these decisions. There was no significant increase in the proportion of evidence-based decisions made over time.

Conclusions

We deemed 34% of decisions regarding the management of obstructive sleep apnea in children without tonsillar hypertrophy to be evidence based and found that sharing the basis for decisions did not improve the percentage of evidence-based decisions over time. These findings reflect significant evidence gaps and highlight the need for a systematic literature evaluation to identify best practice in managing this population. We recommend that these evidence gaps be further characterized and incorporated into an agenda for future research.

Airway Disease and Management in Bronchopulmonary Dysplasia

This article presents an overview of the diagnosis and management of airway problems encountered in infants with severe bronchopulmonary dysplasia (BPD). Respiratory failure in premature infants develops as a result of parenchymal and airway diseases. The survival of increasingly premature infants and the ventilatory support required by premature lungs may result in airway disease. The management of respiratory failure depends on whether it is primarily caused by parenchymal versus airway diseases. Continuous airway pressure early in the neonatal period has favorably changed the incidence of BPD. This article discusses the indications, timing, and guidelines for care of tracheotomy.

Quantitative Magnetic Resonance Imaging of Bronchopulmonary Dysplasia in the Neonatal Intensive Care Unit Environment

RATIONALE

Bronchopulmonary dysplasia (BPD) is a prevalent yet poorly characterized pulmonary complication of premature birth; the current definition is based solely on oxygen dependence at 36 weeks postmenstrual age without objective measurements of structural abnormalities across disease severity.

OBJECTIVES

We hypothesize that magnetic resonance imaging (MRI) can spatially resolve and quantify the structural abnormalities of the neonatal lung parenchyma associated with premature birth.

METHODS

Using a unique, small-footprint, 1.5-T MRI scanner within our neonatal intensive care unit (NICU), diagnostic-quality MRIs using commercially available sequences (gradient echo and spin echo) were acquired during quiet breathing in six patients with BPD, six premature patients without diagnosed BPD, and six full-term NICU patients (gestational ages, 23-39 wk) at near term-equivalent age, without administration of sedation or intravenous contrast. Images were scored by a radiologist using a modified Ochiai score, and volumes of high- and low-signal intensity lung parenchyma were quantified by segmentation and threshold analysis.

MEASUREMENTS AND MAIN RESULTS

Signal increases, putatively combinations of fibrosis, edema, and atelectasis, were present in all premature infants. Infants with diagnosed BPD had significantly greater volume of high-signal lung (mean ± SD, 26.1 ± 13.8%) compared with full-term infants (7.3 ± 8.2%; P = 0.020) and premature infants without BPD (8.2 ± 6.4%; P = 0.026). Signal decreases, presumably alveolar simplification, only appeared in the most severe BPD cases, although cystic appearance did increase with severity.

CONCLUSIONS

Pulmonary MRI reveals quantifiable, significant differences between patients with BPD, premature patients without BPD, and full-term control subjects. These methods could be implemented to individually phenotype disease, which may impact clinical care and predict future outcomes.

Upper Airway Elasticity Estimation in Pediatric Down Syndrome Sleep Apnea Patients Using Collapsible Tube Theory

Elasticity of the soft tissues surrounding the upper airway lumen is one of the important factors contributing to upper airway disorders such as snoring and obstructive sleep apnea. The objective of this study is to calculate patient specific elasticity of the pharynx from magnetic resonance (MR) images using a 'tube law', i.e., the relationship between airway cross-sectional area and transmural pressure difference. MR imaging was performed under anesthesia in children with Down syndrome (DS) and obstructive sleep apnea (OSA). An airway segmentation algorithm was employed to evaluate changes in airway cross-sectional area dilated by continuous positive airway pressure (CPAP). A pressure-area relation was used to make localized estimates of airway wall stiffness for each patient. Optimized values of patient specific Young's modulus for tissue in the velopharynx and oropharynx, were estimated from finite element simulations of airway collapse. Patient specific deformation of the airway wall under CPAP was found to exhibit either a non-linear 'hardening' or 'softening' behavior. The localized airway and tissue elasticity were found to increase with increasing severity of OSA. Elasticity based patient phenotyping can potentially assist clinicians in decision making on CPAP and airway or tissue elasticity can supplement well-known clinical measures of OSA severity.

Systematic review of site of obstruction identification and non-CPAP treatment options for children with persistent pediatric obstructive sleep apnea

OBJECTIVES/HYPOTHESIS

Although adenotonsillectomy is accepted as a first-line therapy for pediatric obstructive sleep apnea (OSA), there is currently no consensus regarding optimal methods for identifying the sites of obstruction or treatment of children with persistent disease after surgery. With this in mind, our aim was to systematically review the English-language literature pertaining to these issues.

STUDY DESIGN

Systematic review.

METHODS

We searched all indexed years of Pubmed, Cochrane CENTRAL, DynaMed, UpToDate, CINAHL, and Scopus for English-language articles containing original human data, with ≥ 7 participants, all < 18 years old. Data regarding study design, demographics, clinical characteristics/outcomes, level of evidence, and risk of bias were obtained. Articles were independently reviewed by two investigators.

RESULTS

Of 758 identified abstracts, 24 articles (combined population = 960) were ultimately included. Seventeen (71%) described methods to identify site(s) of obstruction: drug-induced sleep endoscopy (11/24), cine magnetic resonance imaging (MRI) (3/24), and alternative imaging (3/24). Treatment options included lingual tonsillectomy (n = 6), with success rates of 57% to 88% (Cohen's effect size d = 1.38), as well as supraglottoplasty (n = 4), with success rates of 58% to 72% (d = 0.64). Additional treatments included medications and surgery (e.g., partial midline glossectomy and tongue suspension).

CONCLUSIONS

Drug-induced sleep endoscopy and cine MRI are the most commonly reported tools to identify sites of obstruction for children with persistent OSA; however, these techniques have not yet been clearly linked to outcomes. Evidence for treatment is extremely limited and focuses primarily on lingual tonsillectomy and supraglottoplasty. Also, reports regarding appropriate patient selection and outcomes in obese or otherwise healthy children are scant.

The impact of transforming healthcare delivery on cystic fibrosis outcomes: a decade of quality improvement at Cincinnati Children's Hospital

BACKGROUND

In 2001, Cincinnati Children's Hospital embarked on a journey to improve healthcare delivery to patients with cystic fibrosis (CF). Data from the Cystic Fibrosis Foundation National Patient Registry revealed our below-average clinical outcomes, prompting us to initiate improvement interventions.

OBJECTIVE

To improve clinical outcomes for patients with CF through a comprehensive quality-improvement approach directed at increasing patient centredness and improving healthcare delivery.

INTERVENTIONS

In 2001, we shared our below-average outcomes with patients, families and care providers. We instituted a quality-improvement steering committee with parental and hospital leadership, and our data-management support was restructured to provide real-time clinical data to monitor our progress. In 2002, our weekly chart conference changed to a prospective planning session and individualised daily schedules were created for inpatients. In 2003, an influenza vaccination campaign was initiated and our infection-control practices were redesigned. In 2005, best-practice guidelines were developed for airway-clearance therapy. In 2007, evidence-based clinical algorithms were designed and implemented and key care-team members were added.

MEASUREMENTS

Primary outcome measures were median forced expiratory volume in 1 s per cent predicted (age range 6-17 years) and median body mass index percentile (age range 2-20 years).

RESULTS

From 2000 to 2010, median forced expiratory volume in 1 s increased from 81.7% to 100.1% predicted and median body mass index increased from the 35th to the 55th centile.

DISCUSSION

By focusing on specific outcomes, empowering families and patients, effectively using data, and standardising care processes, we transformed the culture and delivery of care for our patients with CF and learned valuable lessons potentially translatable to other chronic-care providers.

Obstructive Sleep Apnea in Patients with Congenital Long QT Syndrome: Implications for Increased Risk of Sudden Cardiac Death

BACKGROUND

Congenital long QT syndrome (LQTS) is a familial arrhythmogenic cardiac channelopathy characterized by prolonged ventricular repolarization and increased risk of torsades de pointes-mediated syncope, seizures, and sudden cardiac death (SCD). QT prolongation corrected for heart rate (QTc) is an important diagnostic and prognostic feature in LQTS. Obstructive sleep apnea (OSA) has been increasingly implicated in the pathogenesis of cardiovascular disease, including arrhythmias and SCD. We tested the hypothesis that the presence of concomitant OSA in patients with LQTS is associated with increased QT intervals, both during sleep and while awake.

METHODS AND RESULTS

Polysomnography with simultaneous overnight 12-lead electrocardiography (ECG) was recorded in 54 patients with congenital LQTS and 67 control subjects. OSA was diagnosed as apnea-hypopnea index (AHI) ≥ 5 events/h for adults and AHI > 1 event/h for children. RR and QT intervals were measured from the 12-lead surface ECG. QTc was determined by the Bazett formula. Respiratory disturbance index, AHI, and arousal index were significantly increased in patients with LQTS and with OSA compared to those without OSA and control subjects. QTc during different sleep stages and while awake was also significantly increased in patients with LQTS and OSA compared to those without OSA. Severity of OSA in patients with LQTS was directly associated with the degree of QTc.

CONCLUSIONS

The presence and severity of obstructive sleep apnea (OSA) in patients with congenital long QT syndrome (LQTS) is associated with increased QT prolongation corrected for heart rate, which is an important biomarker of sudden cardiac death (SCD). Treatment of OSA in LQTS patients may reduce QT prolongation, thus reducing the risk of LQT-triggered SCD.

Daytime cardiac repolarization in patients with obstructive sleep apnea

PURPOSE

Obstructive sleep apnea (OSA) has been implicated in complications of cardiovascular disease, including arrhythmias and sudden cardiac death (SCD). Prolonged QT interval is associated with arrhythmias and SCD in patients with cardiovascular disease and apparently healthy humans. Apneic episodes during sleep in OSA patients are associated with QT prolongation due to increased vagal activity, but it is not understood whether chronic QT prolongation persists during normoxic daytime wakefulness.

METHODS

To determine whether daytime QT intervals in OSA patients are prolonged compared to control subjects, we recruited 97 (76 male, 21 female) newly diagnosed patients with OSA [apnea-hypopnea index (AHI) ≥5 events/h] and 168 (100 male, 68 female) healthy volunteers (AHI <5 events/h) and measured daytime resting QT and RR intervals from the electrocardiograms to determine QT prolongation corrected for heart rate (QTc).

RESULTS

All subjects with OSA were older and heavier, with increased heart rate, significantly increased AHI and arousal index, and reduced oxygen saturation (SpO2) during sleep, and spent less time in sleep with >90 % SpO2 compared to respective controls. QTc in patients with OSA (410 ± 3.3 for male and 433 ± 5.6 for female) was significantly increased compared to respective control groups (399 ± 2.9 for male and 417 ± 2.9 for female), after adjustment for age and body mass index.

CONCLUSIONS

Our data show that OSA in either men or women is associated with a significant increase in resting daytime QTc. The propensity for ventricular arrhythmias in patients with OSA may be a result of abnormalities in resting cardiac repolarization.

MRI sleep studies: use of positive airway pressure support in patients with severe obstructive sleep apnea

Maintaining the patency of the upper airway during MRI sleep studies, without an artificial airway placement in sedated or anesthetized patients with severe obstructive sleep apnea (OSA) is a major challenge. We report two cases in which a continuous positive airway pressure (CPAP) was used instead of artificial airway to allow interpretation of the dynamic component of the study.

Glucose, insulin, and insulin resistance in normal-weight, overweight and obese children with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is associated with components of metabolic syndrome. Both body weight and OSA independently influence metabolic measurements. The goal of this study was to determine whether OSA in normal-weight, overweight or obese children, compared to matched control groups, was associated with increased levels of glucose, insulin and insulin resistance (IR).

METHODS

Age- and gender-specific body mass index (BMI) percentiles were determined and used to categorize subjects into normal-weight (BMI<85%) and overweight-obese (BMI≥85%) groups. In addition, subjects were divided into normal-weight (BMI<85%), overweight (BMI≥85% and <95%) and obese (BMI≥95%) groups. Polysomnography was conducted and morning levels of glucose and insulin were measured and IR was determined from the blood samples collected early in the morning after overnight fast. Results were compared between the subject groups. Effects of severity of OSA defined by apnea hypopnea index (AHI) and oxygen desaturation index (ODI) on glucose, insulin, and HOMA-IR were analyzed.

RESULTS

Glucose, insulin, and HOMA-IR in OSA and matched control groups were not significantly different for normal-weight, overweight and obese subjects. The ODI was significantly associated with elevated levels of glucose and HOMA-IR after adjustment for age, gender, race, and BMI Z-score.

CONCLUSIONS

IR levels between OSA and control for both normal-weight, overweight and obese subjects were not significantly different. The ODI was associated with increased IR in children with OSA. OSA-induced hypoxic events during sleep may be a potential mechanism of increased IR in children with OSA, independent of body weight.

An adverse effect of positive airway pressure on the upper airway documented with magnetic resonance imaging

IMPORTANCE

Positive pressure air is used during basic life support to provide respirations and applied as continuous positive airway pressure to maintain a patent airway during sleep or anesthesia. These functions are more critical in children with obstructive sleep apnea, who often have smaller airway dimensions and increased airway collapsibility.

OBSERVATIONS

We report 2 cases of boys with Down syndrome and a history of obstructive sleep apnea in whom adverse narrowing of the retroglossal airway is caused by continuous positive airway pressure applied via face mask as documented with magnetic resonance imaging.

CONCLUSIONS AND RELEVANCE

Administration of continuous positive airway pressure by means of face mask to patients can result in adverse effects on the airway patency by pushing the tongue posteriorly. Awareness of this effect on patients with open mouths and large tongues, as present in Down syndrome, is important for sleep apnea treatment, anesthesia, and emergency respiratory support. Generalization of our observation is not possible at this time. Additional prospective studies of the effects of continuous positive airway pressure on airway patency in sedated and/or anesthetized children are required to confirm our anecdotal observations.

Baroreflex sensitivity after adenotonsillectomy in children with obstructive sleep apnea during wakefulness and sleep

STUDY OBJECTIVES

Children with obstructive sleep apnea have blunted baroreflex sensitivity and increased blood pressure variability. The aim of the study was to test the hypothesis that treatment of sleep apnea by adenotonsillectomy results in significant improvement of baroreflex sensitivity, lowering of blood pressure and blood pressure variability and increase vagal heart rate modulation.

STUDY DESIGN

One hundred ninety-four children aged 9.6 ± 2.3 years were enrolled; 133 had obstructive sleep apnea and 61 were healthy controls. For children with sleep apnea, polysomnography with 3-lead electrocardiography and continuous blood pressure was performed before adenotonsillectomy, then 6 weeks and 6 months postoperatively. Controls underwent the same assessment at study entry and 6 months later. Spontaneous baroreflex sensitivity was measured in the time and frequency domains. Data analyses were performed for available and complete cases.

RESULTS

Children with sleep apnea experienced postoperatively an increase in baroreflex sensitivity and decrease in blood pressure variability during wakefulness and sleep. A decrease in blood pressure during sleep and in heart rate during wakefulness was also measured. The improvement in baroreflex sensitivity was predicted by the change in the apnea-hypopnea and arousal indices. A normal pattern of rising baroreflex sensitivity during the night was restored in children with severe apnea after surgery. However, baroreceptor sensitivity did not completely normalize after treatment.

CONCLUSION

Treatment of obstructive sleep apnea in children by adenotonsillectomy is associated with gradual improvement in known risk factors for cardiovascular disease. Complete normalization of baroreceptor sensitivity was not achieved 6 months postoperatively.