Disparities in Telemedicine Use Among Children Seen in Surgical Clinics During the COVID-19 Pandemic: Experience of One Tertiary Care Freestanding Children's Hospital

Background: Telemedicine use dramatically increased during the COVID-19 pandemic. However, the effects of telemedicine on pre-existing disparities in pediatric surgical access have not been well described. We describe our center's early experience with telemedicine and disparities in patients' access to outpatient surgical care. Methods: A retrospective study of outpatient visits within all surgical divisions from May to December 2020 was conducted. We assessed the rates of scheduled telemedicine visits during that period, as well as the rate of completing a visit after it has been scheduled. Descriptive and logistic regression analyses were used to test for associations between these rates and patient characteristics. Results: Over the study period, 109,601 visits were scheduled. Telemedicine accounted for 6.1% of all visits with lower cancellation rates than in-person visits (26.9% vs. 34.7%). More scheduled telemedicine encounters were observed for older patients, White, English speakers, those with private insurance, and those living in rural areas. Lower odds of telemedicine visit completion were observed among patients with public insurance (odds ratio [OR] 0.7, 95% confidence interval [CI] 0.64-0.77), Spanish language preference (OR 0.84, 95% CI 0.72-0.97), and those living in rural areas (OR 0.73, 95% CI 0.64-0.84). In contrast, higher odds of telemedicine visit completion were associated with a higher Social Deprivation Index score (OR 1.41, 95% CI 1.27-1.58). Telemedicine visit completion was also associated with increasing community-level income and distance from the hospital. Conclusions: Telemedicine use for outpatient surgical care was generally low during the peak of the pandemic, and certain populations were less likely to utilize it. These findings call for further action to bridge gaps in telemedicine use.

Sepsis Prediction in Hospitalized Children: Clinical Decision Support Design and Deployment

BACKGROUND

Following development and validation of a sepsis prediction model described in a companion article, we aimed to use quality improvement and safety methodology to guide the design and deployment of clinical decision support (CDS) tools and clinician workflows to improve pediatric sepsis recognition in the inpatient setting.

METHODS

CDS tools and sepsis huddle workflows were created to implement an electronic health record-based sepsis prediction model. These were proactively analyzed and refined using simulation and safety science principles before implementation and were introduced across inpatient units during 2020-2021. Huddle compliance, alerts per non-ICU patient days, and days between sepsis-attributable emergent transfers were monitored. Rapid Plan-Do-Study-Act (PDSA) cycles based on user feedback and weekly metric data informed improvement throughout implementation.

RESULTS

There were 264 sepsis alerts on 173 patients with an 89% bedside huddle completion rate and 10 alerts per 1000 non-ICU patient days per month. There was no special cause variation in the metric days between sepsis-attributable emergent transfers.

CONCLUSIONS

An automated electronic health record-based sepsis prediction model, CDS tools, and sepsis huddle workflows were implemented on inpatient units with a relatively low rate of interruptive alerts and high compliance with bedside huddles. Use of CDS best practices, simulation, safety tools, and quality improvement principles led to high utilization of the sepsis screening process.

Perceptions of Artificial Intelligence-Assisted Care for Children With a Respiratory Complaint

OBJECTIVES

To evaluate caregiver opinions on the use of artificial intelligence (AI)-assisted medical decision-making for children with a respiratory complaint in the emergency department (ED).

METHODS

We surveyed a sample of caregivers of children presenting to a pediatric ED with a respiratory complaint. We assessed caregiver opinions with respect to AI, defined as "specialized computer programs" that "help make decisions about the best way to care for children." We performed multivariable logistic regression to identify factors associated with discomfort with AI-assisted decision-making.

RESULTS

Of 279 caregivers who were approached, 254 (91.0%) participated. Most indicated they would want to know if AI was being used for their child's health care (93.5%) and were extremely or somewhat comfortable with the use of AI in deciding the need for blood (87.9%) and viral testing (87.6%), interpreting chest radiography (84.6%), and determining need for hospitalization (78.9%). In multivariable analysis, caregiver age of 30 to 37 years (adjusted odds ratio [aOR] 3.67, 95% confidence interval [CI] 1.43-9.38; relative to 18-29 years) and a diagnosis of bronchospasm (aOR 5.77, 95% CI 1.24-30.28 relative to asthma) were associated with greater discomfort with AI. Caregivers with children being admitted to the hospital (aOR 0.23, 95% CI 0.09-0.50) had less discomfort with AI.

CONCLUSIONS

Caregivers were receptive toward the use of AI-assisted decision-making. Some subgroups (caregivers aged 30-37 years with children discharged from the ED) demonstrated greater discomfort with AI. Engaging with these subgroups should be considered when developing AI applications for acute care.

Sepsis Prediction in Hospitalized Children: Model Development and Validation

BACKGROUND AND OBJECTIVES

Early recognition and treatment of pediatric sepsis remain mainstay approaches to improve outcomes. Although most children with sepsis are diagnosed in the emergency department, some are admitted with unrecognized sepsis or develop sepsis while hospitalized. Our objective was to develop and validate a prediction model of pediatric sepsis to improve recognition in the inpatient setting.

METHODS

Patients with sepsis were identified using intention-to-treat criteria. Encounters from 2012 to 2018 were used as a derivation to train a prediction model using variables from an existing model. A 2-tier threshold was determined using a precision-recall curve: an "Alert" tier with high positive predictive value to prompt bedside evaluation and an "Aware" tier with high sensitivity to increase situational awareness. The model was prospectively validated in the electronic health record in silent mode during 2019.

RESULTS

A total of 55 980 encounters and 793 (1.4%) episodes of sepsis were used for derivation and prospective validation. The final model consisted of 13 variables with an area under the curve of 0.96 (95% confidence interval 0.95-0.97) in the validation set. The Aware tier had 100% sensitivity and the Alert tier had a positive predictive value of 14% (number needed to alert of 7) in the validation set.

CONCLUSIONS

We derived and prospectively validated a 2-tiered prediction model of inpatient pediatric sepsis designed to have a high sensitivity Aware threshold to enable situational awareness and a low number needed to Alert threshold to minimize false alerts. Our model was embedded in our electronic health record and implemented as clinical decision support, which is presented in a companion article.

Ventilatory and Orthostatic Challenges Reveal Biomarkers for Neurocognition in Children and Young Adults With Congenital Central Hypoventilation Syndrome

BACKGROUND

Children and young adults with congenital central hypoventilation syndrome (CCHS) are at risk of cognitive deficits. They experience autonomic dysfunction and chemoreceptor insensitivity measured during ventilatory and orthostatic challenges, but relationships between these features are undefined.

RESEARCH QUESTION

Can a biomarker be identified from physiologic responses to ventilatory and orthostatic challenges that is related to neurocognitive outcomes in CCHS?

STUDY DESIGN AND METHODS

This retrospective study included 25 children and young adults with CCHS tested over an inpatient stay. Relationships between physiologic measurements during hypercarbic and hypoxic ventilatory challenges, hypoxic ventilatory challenges, and orthostatic challenges and neurocognitive outcomes (by Wechsler intelligence indexes) were examined. Independent variable inclusion was determined by significant associations in Pearson's analyses. Multivariate linear regressions were used to assess relationships between measured physiologic responses to challenges and neurocognitive scores.

RESULTS

Significant relationships were identified between areas of fluid intelligence and measures of oxygen saturation (SpO2) and heart rate (HR) during challenges. Specifically, perceptual reasoning was related to HR (adjusted regression [β] coefficient, -0.68; 95% CI, 1.24 to -0.12; P = .02) during orthostasis. Working memory was related to change in HR (β, -1.33; 95% CI, -2.61 to -0.05; P = .042) during the hypoxic ventilatory challenge. Processing speed was related to HR (β, -1.19; 95% CI, -1.93 to -0.46; P = .003) during orthostasis, to baseline SpO2 (hypercarbic and hypoxic β, 8.57 [95% CI, 1.63-15.51]; hypoxic β, 8.37 [95% CI, 3.65-13.11]; P = .002 for both) during the ventilatory challenges, and to intrachallenge SpO2 (β, 5.89; 95% CI, 0.71-11.07; P = .028) during the hypoxic ventilatory challenge.

INTERPRETATION

In children and young adults with CCHS, SpO2 and HR-or change in HR-at rest and as a response to hypoxia and orthostasis are related to cognitive outcomes in domains of known risk, particularly fluid reasoning. These findings can guide additional research on the usefulness of these as biomarkers in understanding the impact of daily physical stressors on neurodevelopment in this high-risk group.

A narrative review of the mechanisms and consequences of intermittent hypoxia and the role of advanced analytic techniques in pediatric autonomic disorders

Disorders of autonomic functions are typically characterized by disturbances in multiple organ systems. These disturbances are often comorbidities of common and rare diseases, such as epilepsy, sleep apnea, Rett syndrome, congenital heart disease or mitochondrial diseases. Characteristic of many autonomic disorders is the association with intermittent hypoxia and oxidative stress, which can cause or exaggerate a variety of other autonomic dysfunctions, making the treatment and management of these syndromes very complex. In this review we discuss the cellular mechanisms by which intermittent hypoxia can trigger a cascade of molecular, cellular and network events that result in the dysregulation of multiple organ systems. We also describe the importance of computational approaches, artificial intelligence and the analysis of big data to better characterize and recognize the interconnectedness of the various autonomic and non-autonomic symptoms. These techniques can lead to a better understanding of the progression of autonomic disorders, ultimately resulting in better care and management.

Novel approaches to capturing and using continuous cardiorespiratory physiological data in hospitalized children

Continuous cardiorespiratory physiological monitoring is a cornerstone of care in hospitalized children. The data generated by monitoring devices coupled with machine learning could transform the way we provide care. This scoping review summarizes existing evidence on novel approaches to continuous cardiorespiratory monitoring in hospitalized children. We aimed to identify opportunities for the development of monitoring technology and the use of machine learning to analyze continuous physiological data to improve the outcomes of hospitalized children. We included original research articles published on or after January 1, 2001, involving novel approaches to collect and use continuous cardiorespiratory physiological data in hospitalized children. OVID Medline, PubMed, and Embase databases were searched. We screened 2909 articles and performed full-text extraction of 105 articles. We identified 58 articles describing novel devices or approaches, which were generally small and single-center. In addition, we identified 47 articles that described the use of continuous physiological data in prediction models, but only 7 integrated multidimensional data (e.g., demographics, laboratory results). We identified three areas for development: (1) further validation of promising novel devices; (2) more studies of models integrating multidimensional data with continuous cardiorespiratory data; and (3) further dissemination, implementation, and validation of prediction models using continuous cardiorespiratory data. IMPACT: We performed a comprehensive scoping review of novel approaches to capture and use continuous cardiorespiratory physiological data for monitoring, diagnosis, providing care, and predicting events in hospitalized infants and children, from novel devices to machine learning-based prediction models. We identified three key areas for future development: (1) further validation of promising novel devices; (2) more studies of models integrating multidimensional data with continuous cardiorespiratory data; and (3) further dissemination, implementation, and validation of prediction models using cardiorespiratory data.

Artificial intelligence-based clinical decision support in pediatrics

Machine learning models may be integrated into clinical decision support (CDS) systems to identify children at risk of specific diagnoses or clinical deterioration to provide evidence-based recommendations. This use of artificial intelligence models in clinical decision support (AI-CDS) may have several advantages over traditional "rule-based" CDS models in pediatric care through increased model accuracy, with fewer false alerts and missed patients. AI-CDS tools must be appropriately developed, provide insight into the rationale behind decisions, be seamlessly integrated into care pathways, be intuitive to use, answer clinically relevant questions, respect the content expertise of the healthcare provider, and be scientifically sound. While numerous machine learning models have been reported in pediatric care, their integration into AI-CDS remains incompletely realized to date. Important challenges in the application of AI models in pediatric care include the relatively lower rates of clinically significant outcomes compared to adults, and the lack of sufficiently large datasets available necessary for the development of machine learning models. In this review article, we summarize key concepts related to AI-CDS, its current application to pediatric care, and its potential benefits and risks. IMPACT: The performance of clinical decision support may be enhanced by the utilization of machine learning-based algorithms to improve the predictive performance of underlying models. Artificial intelligence-based clinical decision support (AI-CDS) uses models that are experientially improved through training and are particularly well suited toward high-dimensional data. The application of AI-CDS toward pediatric care remains limited currently but represents an important area of future research.

Parental Perceptions on Use of Artificial Intelligence in Pediatric Acute Care

BACKGROUND

Family engagement is critical in the implementation of artificial intelligence (AI)-based clinical decision support tools, which will play an increasing role in health care in the future. We sought to understand parental perceptions of computer-assisted health care of children in the emergency department (ED).

METHODS

We conducted a population-weighted household panel survey of parents with minor children in their home in a large US city to evaluate perceptions of the use of computer programs for the care of children with respiratory illness. We identified demographics associated with discomfort with AI using survey-weighted logistic regression.

RESULTS

Surveys were completed by 1620 parents (panel response rate = 49.7%). Most respondents were comfortable with the use of computer programs to determine the need for antibiotics (77.6%) or bloodwork (76.5%), and to interpret radiographs (77.5%). In multivariable analysis, Black non-Hispanic parents reported greater discomfort with AI relative to White non-Hispanic parents (odds ratio [OR] 1.67, 95% confidence interval [CI] 1.03-2.70) as did younger parents (18-25 years) relative to parents ≥46 years (OR 2.48, 95% CI 1.31-4.67). The greatest perceived benefits of computer programs were finding something a human would miss (64.2%, 95% CI 60.9%-67.4%) and obtaining a more rapid diagnosis (59.6%; 56.2%-62.9%). Areas of greatest concern were diagnostic errors (63.0%, 95% CI 59.6%-66.4%), and recommending incorrect treatment (58.9%, 95% CI 55.5%-62.3%).

CONCLUSIONS

Parents were generally receptive to computer-assisted management of children with respiratory illnesses in the ED, though reservations emerged. Black non-Hispanic and younger parents were more likely to express discomfort about AI.

Association of Youth Suicides and County-Level Mental Health Professional Shortage Areas in the US

Importance

Suicide is the second leading cause of death among US adolescents. Workforce shortages of mental health professionals in the US are widespread, but the association between mental health workforce shortages and youth suicides is not well understood.

Objective

To assess the association between youth suicide rates and mental health professional workforce shortages at the county level, adjusting for county demographic and socioeconomic characteristics.

Design, Setting, and Participants

This retrospective cross-sectional study included all US counties and used data of all US youlth suicides from January 2015, through December 31, 2016. Data were analyzed from July 1, 2021, through December 20, 2021.

Exposures

County health-professional shortage area designation for mental health, assigned by the US Health Resources and Services Administration based on mental health professionals relative to the population, level of need for mental health services, and service availability in contiguous areas. Designated shortage areas receive a score from 0 to 25, with higher scores indicating greater workforce shortages.

Main Outcomes and Measures

Suicides by youth aged 5 to 19 years from 2015 to 2016 were identified from the US Centers for Disease Control and Prevention's Compressed Mortality File. A multivariable negative binomial regression model was used to analyze the association between youth suicide rates and mental health workforce shortage designation, adjusting for the presence of a children's mental health hospital and county-level markers of health insurance coverage, education, unemployment, income, poverty, urbanicity, racial and ethnic composition, and year. Similar models were performed for the subgroups of (1) firearm suicides and (2) counties assigned a numeric shortage score.

Results

During the study period, there were 5034 youth suicides (72.8% male and 68.2% non-Hispanic White) with an annual suicide rate of 3.99 per 100 000 youths. Of 3133 US counties, 2117 (67.6%) were designated as mental health workforce shortage areas. After adjusting for county characteristics, mental health workforce shortage designation was associated with an increased youth suicide rate (adjusted incidence rate ratio [aIRR], 1.16; 95% CI, 1.07-1.26) and an increased youth firearm suicide rate (aIRR, 1.27; 95% CI, 1.13-1.42). For counties with an assigned numeric workforce shortage score, the adjusted youth suicide rate increased 4% for every 1-point increase in the score (aIRR, 1.04; 95% CI, 1.02-1.06).

Conclusions and Relevance

In this cross-sectional study, US county mental health professional workforce shortages were associated with increased youth suicide rates. These findings may inform suicide prevention efforts.

Development and Validation of an Integrated Suite of Prediction Models for All-Cause 30-Day Readmissions of Children and Adolescents Aged 0 to 18 Years

IMPORTANCE

Readmission is often considered a hospital quality measure, yet no validated risk prediction models exist for children.

OBJECTIVE

To develop and validate a tool identifying patients before hospital discharge who are at risk for subsequent readmission, applicable to all ages.

DESIGN, SETTING, AND PARTICIPANTS

This population-based prognostic analysis used electronic health record-derived data from a freestanding children's hospital from January 1, 2016, to December 31, 2019. All-cause 30-day readmission was modeled using 3 years of discharge data. Data were analyzed from June 1 to November 30, 2021.

MAIN OUTCOMES AND MEASURES

Three models were derived as a complementary suite to include (1) children 6 months or older with 1 or more prior hospitalizations within the last 6 months (recent admission model [RAM]), (2) children 6 months or older with no prior hospitalizations in the last 6 months (new admission model [NAM]), and (3) children younger than 6 months (young infant model [YIM]). Generalized mixed linear models were used for all analyses. Models were validated using an additional year of discharges.

RESULTS

The derivation set contained 29 988 patients with 48 019 hospitalizations; 50.1% of these admissions were for children younger than 5 years and 54.7% were boys. In the derivation set, 4878 of 13 490 admissions (36.2%) in the RAM cohort, 2044 of 27 531 (7.4%) in the NAM cohort, and 855 of 6998 (12.2%) in the YIM cohort were followed within 30 days by a readmission. In the RAM cohort, prior utilization, current or prior procedures indicative of severity of illness (transfusion, ventilation, or central venous catheter), commercial insurance, and prolonged length of stay (LOS) were associated with readmission. In the NAM cohort, procedures, prolonged LOS, and emergency department visit in the past 6 months were associated with readmission. In the YIM cohort, LOS, prior visits, and critical procedures were associated with readmission. The area under the receiver operating characteristics curve was 83.1 (95% CI, 82.4-83.8) for the RAM cohort, 76.1 (95% CI, 75.0-77.2) for the NAM cohort, and 80.3 (95% CI, 78.8-81.9) for the YIM cohort.

CONCLUSIONS AND RELEVANCE

In this prognostic study, the suite of 3 prediction models had acceptable to excellent discrimination for children. These models may allow future improvements in tailored discharge preparedness to prevent high-risk readmissions.

Association Between Heart Rate Variability and Inflammatory Biomarkers in Critically Ill Children

OBJECTIVES

The autonomic nervous system (ANS) can both modulate and be modulated by the inflammatory response during critical illness. We aimed to determine whether heart rate variability (HRV), a measure of ANS function, is associated with proinflammatory biomarker levels in critically ill children.

DESIGN

Two cohorts were analyzed. The first was a prospective observational cohort from August 2018 to August 2020 who had plasma proinflammatory cytokine measurements within 72 hours of admission, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-8. The second was a retrospective cohort from June 2012 to August 2020 who had at least one C-reactive protein (CRP) measurement within 72 hours of admission.

SETTING

Forty-six-bed PICU.

PATIENTS

Critically ill children in either cohort who had continuous heart rate data available from the bedside monitors.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Sixty-two patients were included in the prospective cohort and 599 patients in the retrospective cohort. HRV was measured using the age-adjusted integer heart rate variability (HRVi), which is the sd of the heart rate sampled every 1 second over 5 consecutive minutes. The median HRVi was measured in the 12-hour period ending 30 minutes prior to inflammatory biomarker collection. HRVi was inversely correlated with IL-6, IL-8, and CRP levels (p ≤ 0.02); correlation with IL-8 and CRP persisted after adjusting for Pediatric Risk of Mortality III and age, and median HR and age (p < 0.001).

CONCLUSIONS

HRVi is inversely correlated with IL-6, IL-8, and CRP. Further studies are needed to validate this measure as a proxy for a proinflammatory state.

Cerebral Autoregulation During Orthostatic Challenge in Congenital Central Hypoventilation Syndrome

RATIONALE

Congenital Central Hypoventilation Syndrome (CCHS) is a rare autonomic disorder with altered regulation of breathing, heart rate (HR), and blood pressure (BP). Aberrant cerebral oxygenation in response to hypercapnia/hypoxia in CCHS raises concern that altered cerebral autoregulation may contribute to CCHS-related, variably impaired neurodevelopment.

OBJECTIVES

Evaluate cerebral autoregulation in response to orthostatic challenge in CCHS cases vs. controls.

METHODS

CCHS and age- and sex-matched control subjects were studied with head-up tilt (HUT) testing to induce orthostatic stress. 50 CCHS and 100 control HUT recordings were included. HR, BP, and cerebral oxygen saturation (rSO2) were continuously monitored. Cerebral oximetry index (COx), a real-time measure of cerebral autoregulation based on these measures, was calculated.

MAIN RESULTS

HUT resulted in greater mean BP decrease from baseline in CCHS vs. controls (11% vs. 6%; p<0.05) and a diminished increase in HR in CCHS vs. controls (11% vs. 18%; p<0.01) in the 5 minutes after tilt-up. Despite a similar COx at baseline, orthostatic provocation within 5 minutes of tilt-up caused a 50% greater increase in COx (p<0.01) and a 29% increase in minutes of impaired autoregulation (p<0.02) in CCHS vs. controls (4.0 vs. 3.1 min).

CONCLUSIONS

Cerebral autoregulatory mechanisms appear intact in CCHS, but the greater hypotension observed in CCHS consequent to orthostatic provocation is associated with greater values of COx/impaired autoregulation when BP is below lower limits of autoregulation. Effects of repeated orthostatic challenges in everyday living in CCHS necessitate further study to determine their influence on neurodevelopmental disease burden.

Development of a Heart Rate Variability Risk Score to Predict Organ Dysfunction and Death in Critically Ill Children

OBJECTIVES

Determine whether the Heart Rate Variability Dysfunction score, a novel age-normalized measure of autonomic nervous system dysregulation, is associated with the development of new or progressive multiple organ dysfunction syndrome or death in critically ill children.

DESIGN, SETTING, AND PATIENTS

This was a retrospective, observational cohort study from 2012 to 2018. Patients admitted to the PICU with at least 12 hours of continuous heart rate data available from bedside monitors during the first 24 hours of admission were included in the analysis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Heart rate variability was measured using the integer heart rate variability, which is the sd of the heart rate sampled every 1 second over 5 consecutive minutes. The Heart Rate Variability Dysfunction score was derived from age-normalized values of integer heart rate variability and transformed, so that higher scores were indicative of lower integer heart rate variability and a proxy for worsening autonomic nervous system dysregulation. Heart Rate Variability Dysfunction score performance as a predictor of new or progressive multiple organ dysfunction syndrome and 28-day mortality were determined using the area under the receiver operating characteristic curve. Of the 7,223 patients who met inclusion criteria, 346 patients (4.8%) developed new or progressive multiple organ dysfunction syndrome, and 103 (1.4%) died by day 28. For every one-point increase in the median Heart Rate Variability Dysfunction score in the first 24 hours of admission, there was a 25% increase in the odds of new or progressive multiple organ dysfunction syndrome and a 51% increase in the odds of mortality. The median Heart Rate Variability Dysfunction score in the first 24 hours had an area under the receiver operating characteristic curve to discriminate new or progressive multiple organ dysfunction syndrome of 0.67 and to discriminate mortality of 0.80. These results were reproducible in a temporal validation cohort.

CONCLUSIONS

The Heart Rate Variability Dysfunction score, an age-adjusted proxy for autonomic nervous system dysregulation derived from bedside monitor data is independently associated with new or progressive multiple organ dysfunction syndrome and mortality in PICU patients. The Heart Rate Variability Dysfunction score could potentially be used as a single continuous physiologic biomarker or as part of a multivariable prediction model to increase awareness of at-risk patients and augment clinical decision-making.

Autonomic Nervous System Dysfunction Is Associated With Re-hospitalization in Pediatric Septic Shock Survivors

Objective: Re-hospitalization after sepsis can lead to impaired quality of life. Predictors of re-hospitalization could help identify sepsis survivors who may benefit from targeted interventions. Our goal was to determine whether low heart rate variability (HRV), a measure of autonomic nervous system dysfunction, is associated with re-hospitalization in pediatric septic shock survivors. Materials and Methods: This was a retrospective, observational cohort study of patients admitted between 6/2012 and 10/2020 at a single institution. Patients admitted to the pediatric intensive care unit with septic shock who had continuous heart rate data available from the bedside monitors and survived their hospitalization were included. HRV was measured using age-normalized z-scores of the integer HRV (HRVi), which is the standard deviation of the heart rate sampled every 1 s over 5 consecutive minutes. The 24-h median HRVi was assessed on two different days: the last 24 h of PICU admission ("last HRVi") and the 24-h period with the lowest median HRVi ("lowest HRVi"). The change between the lowest and last HRVi was termed "delta HRVi." The primary outcome was re-hospitalization within 1 year of discharge, including both emergency department encounters and hospital readmission, with sensitivity analyses at 30 and 90 days. Kruskal-Wallis, logistic regression, and Poisson regression evaluated the association between HRVi and re-hospitalizations and adjusted for potential confounders. Results: Of the 463 patients who met inclusion criteria, 306 (66%) were re-hospitalized, including 270 readmissions (58%). The last HRVi was significantly lower among re-hospitalized patients compared to those who were not (p = 0.02). There was no difference in the lowest HRVi, but patients who were re-hospitalized showed a smaller recovery in their delta HRVi compared to those who were not re-hospitalized (p = 0.02). This association remained significant after adjusting for potential confounders. In the sensitivity analysis, a smaller recovery in delta HRVi was consistently associated with a higher likelihood of re-hospitalization. Conclusion: In pediatric septic shock survivors, a smaller recovery in HRV during the index admission is significantly associated with re-hospitalization. This continuous physiologic measure could potentially be used as a predictor of patients at risk for re-hospitalization and lower health-related quality of life.

The Pathophysiology of Rett Syndrome With a Focus on Breathing Dysfunctions

Rett syndrome (RTT), an X-chromosome-linked neurological disorder, is characterized by serious pathophysiology, including breathing and feeding dysfunctions, and alteration of cardiorespiratory coupling, a consequence of multiple interrelated disturbances in the genetic and homeostatic regulation of central and peripheral neuronal networks, redox state, and control of inflammation. Characteristic breath-holds, obstructive sleep apnea, and aerophagia result in intermittent hypoxia, which, combined with mitochondrial dysfunction, causes oxidative stress-an important driver of the clinical presentation of RTT.

Long-term drift of Si-MOS quantum dots with intentional donor implants

Charge noise can be detrimental to the operation of quantum dot (QD) based semiconductor qubits. We study the low-frequency charge noise by charge offset drift measurements for Si-MOS devices with intentionally implanted donors near the QDs. We show that the MOS system exhibits non-equilibrium drift characteristics, in the form of transients and discrete jumps, that are not dependent on the properties of the donor implants. The equilibrium charge noise indicates a 1/f noise dependence, and a noise strength as low as [Formula: see text], comparable to that reported in more model GaAs and Si/SiGe systems (which have also not been implanted). We demonstrate that implanted qubits, therefore, can be fabricated without detrimental effects on long-term drift or 1/f noise for devices with less than 50 implanted donors near the qubit.

Heart rate variability as a marker of recovery from critical illness in children

Objectives

The purpose of this study was to Identify whether changes in heart rate variability (HRV) could be detected as critical illness resolves by comparing HRV from the time of pediatric intensive care unit (PICU) admission with HRV immediately prior to discharge. We also sought to demonstrate that HRV derived from electrocardiogram (ECG) data from bedside monitors can be calculated in critically-ill children using a real-time, streaming analytics platform.

Methods

This was a retrospective, observational pilot study of 17 children aged 0 to 18 years admitted to the PICU of a free-standing, academic children’s hospital. Three time-domain measures of HRV were calculated in real-time from bedside monitor ECG data and stored for analysis. Measures included: root mean square of successive differences between NN intervals (RMSSD), percent of successive NN interval differences above 50 ms (pNN50), and the standard deviation of NN intervals (SDNN).

Results

HRV values calculated from the first and last 24 hours of PICU stay were analyzed. Mixed effects models demonstrated that all three measures of HRV were significantly lower during the first 24 hours compared to the last 24 hours of PICU admission (p<0.001 for all three measures). In models exploring the relationship between time from admission and log HRV values, the predicted average HRV remained consistently higher in the last 24 hours of PICU stay compared to the first 24 hours.

Conclusion

HRV was significantly lower in the first 24 hours compared to the 24 hours preceding PICU discharge, after resolution of critical illness. This demonstrates that it is feasible to detect changes in HRV using an automated, streaming analytics platform. Continuous tracking of HRV may serve as a marker of recovery in critically ill children.

Novel methods of imaging and analysis for the thermoregulatory sweat test

The thermoregulatory sweat test (TST) can be central to the identification and management of disorders affecting sudomotor function and small sensory and autonomic nerve fibers, but the cumbersome nature of the standard testing protocol has prevented its widespread adoption. A high-resolution, quantitative, clean and simple assay of sweating could significantly improve identification and management of these disorders. Images from 89 clinical TSTs were analyzed retrospectively using two novel techniques. First, using the standard indicator powder, skin surface sweat distributions were determined algorithmically for each patient. Second, a fundamentally novel method using thermal imaging of forced evaporative cooling was evaluated through comparison with the standard technique. Correlation and receiver operating characteristic analyses were used to determine the degree of match between these methods, and the potential limits of thermal imaging were examined through cumulative analysis of all studied patients. Algorithmic encoding of sweating and nonsweating regions produces a more objective analysis for clinical decision-making. Additionally, results from the forced cooling method correspond well with those from indicator powder imaging, with a correlation across spatial regions of -0.78 (confidence interval: -0.84 to -0.71). The method works similarly across body regions, and frame-by-frame analysis suggests the ability to identify sweating regions within ~1 s of imaging. Although algorithmic encoding can enhance the standard sweat testing protocol, thermal imaging with forced evaporative cooling can dramatically improve the TST by making it less time consuming and more patient friendly than the current approach. NEW & NOTEWORTHY The thermoregulatory sweat test (TST) can be central to the identification and management of several common neurological disorders, but the cumbersome nature of the standard testing protocol has prevented its widespread adoption. In this study, images from 89 clinical TSTs were analyzed retrospectively using two novel techniques. Our results suggest that these improved methods could make sweat testing more reliable and acceptable for screening and management of a range of neurological disorders.

Ion implantation for deterministic single atom devices

We demonstrate a capability of deterministic doping at the single atom level using a combination of direct write focused ion beam and solid-state ion detectors. The focused ion beam system can position a single ion to within 35 nm of a targeted location and the detection system is sensitive to single low energy heavy ions. This platform can be used to deterministically fabricate single atom devices in materials where the nanostructure and ion detectors can be integrated, including donor-based qubits in Si and color centers in diamond.

Congenital central hypoventilation syndrome (CCHS): Circadian temperature variation

BACKGROUND

Congenital central hypoventilation syndrome (CCHS) is a rare neurocristopathy, which includes a control of breathing deficit and features of autonomic nervous system (ANS) dysregulation. In recognition of the fundamental role of the ANS in temperature regulation and rhythm and the lack of any prior characterization of circadian temperature rhythms in CCHS, we sought to explore peripheral and core temperatures and circadian patterning. We hypothesized that CCHS patients would exhibit lower peripheral skin temperatures (PST), variability, and circadian rhythmicity (vs. controls), as well as a disrupted relationship between core body temperature (CBT) and PST.

METHODS

PST was sampled every 3 min over four 24-hr periods in CCHS cases and similarly aged controls. CBT was sampled in a subset of these recordings.

RESULTS

PST was recorded from 25 CCHS cases (110,664 measures/230 days) and 39 controls (78,772 measures/164 days). Simultaneous CBT measurements were made from 23 CCHS patients. In CCHS, mean PST was lower overall (P = 0.03) and at night (P = 0.02), and PST variability (interquartile range) was higher at night (P = 0.05) (vs. controls). PST circadian rhythm remained intact but the phase relationship of PST to CBT rhythm was extremely variable in CCHS.

CONCLUSIONS

PST alterations in CCHS likely reflect altered autonomic control of peripheral vascular tone. These alterations represent a previously unreported manifestation of CCHS and may provide an opportunity for therapeutic intervention. The relationship between temperature dysregulation and CCHS may also offer insight into basic mechanisms underlying thermoregulation.

Rapid-onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation (ROHHAD): Response to ventilatory challenges

Hypoventilation is a defining feature of Rapid-onset Obesity with Hypothalamic dysfunction, Hypoventilation and Autonomic Dysregulation (ROHHAD), a rare respiratory and autonomic disorder. This chronic hypoventilation has been explained as the result of dysfunctional chemosensory control circuits, possibly affecting peripheral afferent input, central integration, or efferent motor control. However, chemosensory function has never been quantified in a cohort of ROHHAD patients. Therefore, the purpose of this study was to assess the response to awake ventilatory challenge testing in children and adolescents with ROHHAD. The ventilatory, cardiovascular and cerebrovascular responses in 25 distinct comprehensive physiological recordings from seven unique ROHHAD patients to three different gas mixtures were analyzed at breath-to-breath and beat-to-beat resolution as absolute measures, as change from baseline, or with derived metrics. Physiologic measures were recorded during a 3-min baseline period of room air, a 3-min gas exposure (of 100% O2; 95% O2, 5% CO2; or 14% O2, 7% CO2 balanced with N2), and a 3-min recovery period. An additional hypoxic challenge was conducted which consisted of either five or seven tidal breaths of 100% N2. While ROHHAD cases showed a diminished VT and inspiratory drive response to hypoxic hypercapnia and absent behavioral awareness of the physiologic compromise, most ventilatory, cardiovascular, and cerebrovascular measures were similar to those of previously published controls using an identical protocol, suggesting a mild chemosensory deficit. Nonetheless, the high mortality rate, comorbidity and physiological fragility of patients with ROHHAD demand continued clinical vigilance.

Transport spectroscopy of low disorder silicon tunnel barriers with and without Sb implants

We present transport measurements of silicon MOS split gate structures with and without Sb implants. We observe classical point contact (PC) behavior that is free of any pronounced unintentional resonances at liquid He temperatures. The implanted device has resonances superposed on the PC transport indicative of transport through the Sb donors. We fit the differential conductance to a rectangular tunnel barrier model with a linear barrier height dependence on source-drain voltage and non-linear dependence on gate bias. Effects such as Fowler-Nordheim (FN) tunneling and image charge barrier lowering (ICBL) are considered. Barrier heights and widths are estimated for the entire range of relevant biases. The barrier heights at the locations of some of the resonances for the implanted tunnel barrier are between 15-20 meV, which are consistent with transport through shallow partially hybridized Sb donors. The dependence of width and barrier height on gate voltage is found to be linear over a wide range of gate bias in the split gate geometry but deviates considerably when the barrier becomes large and is not described completely by standard 1D models such as FN or ICBL effects.

Scanning capacitance microscopy registration of buried atomic-precision donor devices

We show that a scanning capacitance microscope (SCM) can image buried delta-doped donor nanostructures fabricated in Si via a recently developed atomic-precision scanning tunneling microscopy (STM) lithography technique. A critical challenge in completing atomic-precision nanoelectronic devices is to accurately align mesoscopic metal contacts to the STM defined nanostructures. Utilizing the SCMs ability to image buried dopant nanostructures, we have developed a technique by which we are able to position metal electrodes on the surface to form contacts to underlying STM fabricated donor nanostructures with a measured accuracy of 300 nm. Low temperature (T = 4 K) transport measurements confirm successful placement of the contacts to the donor nanostructures.

Lithography and doping in strained Si towards atomically precise device fabrication

We investigate the ability to introduce strain into atomic-scale silicon device fabrication by performing hydrogen lithography and creating electrically active phosphorus δ-doped silicon on strained silicon-on-insulator (sSOI) substrates. Lithographic patterns were obtained by selectively desorbing hydrogen atoms from a H resist layer adsorbed on a clean, atomically flat sSOI(001) surface with a scanning tunnelling microscope tip operating in ultra-high vacuum. The influence of the tip-to-sample bias on the lithographic process was investigated allowing us to pattern feature-sizes from several microns down to 1.3 nm. In parallel we have investigated the impact of strain on the electrical properties of P:Si δ-doped layers. Despite the presence of strain inducing surface variations in the silicon substrate we still achieve high carrier densities (>1.0 × 10(14) cm(-2)) with mobilities of ∼100 cm(2) V(-1) s(-1). These results open up the possibility of a scanning-probe lithography approach to the fabrication of strained atomic-scale devices in silicon.

Residual chemosensitivity to ventilatory challenges in genotyped congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) is a neurodevelopmental disorder characterized by life-threatening hypoventilation, possibly resulting from disruption of central chemosensory integration. However, animal models suggest the possibility of residual chemosensory function in the human disease. Cardioventilatory function in a large cohort with CCHS and verified paired-like homeobox 2B (PHOX2B) mutations was assessed to determine the extent and genotype dependence of any residual chemosensory function in these patients. As part of inpatient clinical care and evaluation, 64 distinct studies from 32 infants, children, and young adults with the disorder were evaluated for physiological response to three different inspired steady-state gas exposures of 3 min each: hyperoxia [100% oxygen (O2)]; hyperoxic hypercapnia [95% O2 and 5% carbon dioxide (CO2)]; and hypoxic hypercapnia [14% O2 and 7% CO2 balanced with nitrogen (N2)]. These were followed by a hypoxia challenge consisting of five or seven breaths of N2 (100% N2). In addition, a control group of 15 young adults was exposed to all but the hypoxic challenge. Comprehensive monitoring was used to derive breath-to-breath and beat-to-beat measures of ventilatory, cardiovascular, and cerebrovascular function. On average, patients showed a residual awake ventilatory response to chemosensory challenge, independent of the specific patient PHOX2B genotype. Graded dysfunction in cardiovascular regulation was found to associate with genotype, suggesting differential effects on different autonomic subsystems. In addition, differences between cases and controls in the cerebrovascular response to chemosensory challenge may indicate alterations in cerebral autoregulation. Thus residual cardiorespiratory responses suggest partial preservation of central nervous system networks that could provide a fulcrum for potential pharmacological interventions.

Congenital central hypoventilation syndrome and sudden infant death syndrome: disorders of autonomic regulation

Long considered a rare and unique disorder of respiratory control, congenital central hypoventilation syndrome has recently been further distinguished as a disorder of autonomic regulation. Similarly, more recent evidence suggests that sudden infant death syndrome is also a disorder of autonomic regulation. Congenital central hypoventilation syndrome typically presents in the newborn period with alveolar hypoventilation, symptoms of autonomic dysregulation and, in a subset of cases, Hirschsprung disease or tumors of neural crest origin or both. Genetic investigation identified PHOX2B, a crucial gene during early autonomic development, as disease defining for congenital central hypoventilation syndrome. Although sudden infant death syndrome is most likely defined by complex multifactorial genetic and environmental interactions, it is also thought to result from central deficits in the control of breathing and autonomic regulation. The purpose of this article is to review the current understanding of these autonomic disorders and discuss the influence of this information on clinical practice and future research directions.

Patterns of inspiratory phase-dependent activity in the in vitro respiratory network

Mechanistic descriptions of rhythmogenic neural networks have often relied on ball-and-stick diagrams, which define interactions between functional classes of cells assumed to be reasonably homogenous. Application of this formalism to networks underlying respiratory rhythm generation in mammals has produced increasingly intricate models that have generated significant insight, but the underlying assumption that individual cells within these network fall into distinct functional classes has not been rigorously tested. In the present study we used multiunit extracellular recording in the in vitro pre-Bötzinger complex to identify and characterize the rhythmic activity of 951 cells. Inspiratory phase-dependent activity was estimated for all cells, and the data set as a whole was analyzed with principal component analysis, nonlinear dimensionality reduction, and hierarchical clustering techniques. None of these techniques revealed categorically distinct functional cell classes, indicating instead that the behavior of these cells within the network falls along several continua of spiking behavior.

Cycle-by-cycle assembly of respiratory network activity is dynamic and stochastic

Rhythmically active networks are typically composed of neurons that can be classified as silent, tonic spiking, or rhythmic bursting based on their intrinsic activity patterns. Within these networks, neurons are thought to discharge in distinct phase relationships with their overall network output, and it has been hypothesized that bursting pacemaker neurons may lead and potentially trigger cycle onsets. We used multielectrode recording from 72 experiments to test these ideas in rhythmically active slices containing the pre-Bötzinger complex, a region critical for breathing. Following synaptic blockade, respiratory neurons exhibited a gradient of intrinsic spiking to rhythmic bursting activities and thus defied an easy classification into bursting pacemaker and nonbursting categories. Features of their firing activity within the functional network were analyzed for correlation with subsequent rhythmic bursting in synaptic isolation. Higher firing rates through all phases of fictive respiration statistically predicted bursting pacemaker behavior. However, a cycle-by-cycle analysis indicated that respiratory neurons were stochastically activated with each burst. Intrinsically bursting pacemakers led some population bursts and followed others. This variability was not reproduced in traditional fully interconnected computational models, while sparsely connected network models reproduced these results both qualitatively and quantitatively. We hypothesize that pacemaker neurons do not act as clock-like drivers of the respiratory rhythm but rather play a flexible and dynamic role in the initiation and stabilization of each burst. Thus, at the behavioral level, each breath can be thought of as de novo assembly of a stochastic collaboration of network topology and intrinsic properties.

Respiratory and cardiovascular indicators of autonomic nervous system dysregulation in familial dysautonomia

Familial dysautonomia (FD) is a profound sensory and autonomic nervous system disorder associated with an increased risk for sudden death. While bradycardia resulting from loss of sympathetic tone has been hypothesized to play a role in this mortality, extended in-home monitoring has failed to find evidence of low heart rates in children with FD. In order to better characterize the specific cardio-respiratory pathophysiology and autonomic dysregulation in patients with FD, 25 affected children and matched controls were studied with in-home technology, during day and night. Respiratory and heart rate timing and variability metrics were derived from inductance plethysmography and electrocardiogram signals. Selective shortening of inspiratory time produced an overall increase in respiratory frequency in children with FD, with higher daytime respiratory variability (vs. controls), suggesting alterations in central rhythm generating circuits that may contribute to the heightened risk for sudden death. Overall heart rate was increased and variability reduced in FD cases, with elevated heart rates during 20% of study time. Time and frequency domain measures of autonomic tone indicated lower parasympathetic drive in FD patients (vs. controls). These results suggest withdrawal of vagal, rather than sympathetic tone, as a cause for the sustained increase and dramatic lability in respiration and heart rates that characterize this disorder.

Efficient clocked electron transfer on superfluid helium

Unprecedented transport efficiency is demonstrated for electrons on the surface of micron-scale superfluid helium-filled channels by co-opting silicon processing technology to construct the equivalent of a charge-coupled device. Strong fringing fields lead to undetectably rare transfer failures after over a billion cycles in two dimensions. This extremely efficient transport is measured in 120 channels simultaneously with packets of up to 20 electrons, and down to singly occupied pixels. These results point the way towards the large scale transport of either computational qubits or electron spin qubits used for communications in a hybrid qubit system.

Policies to promote the community use of schools: a review of state recreational user statutes

CONTEXT

Concern over liability is a barrier to allowing community use of school property for the purpose of engaging in active sport and recreational activities. Recreational user statutes have the potential to limit liability for public schools when use occurs outside of regular school hours, reduce the fear of liability among school administrators, and increase opportunities for access to school facilities for recreation and physical activity by community members. The purpose of this study was to examine the applicability of recreational user statutes to public schools when the use of school facilities for recreational purposes would occur outside of regular school hours.

EVIDENCE ACQUISITION

A review of recreational user statutes from all 50 states was conducted in 2007 and 2009. Characteristics of those statutes from states with laws potentially applicable to public school recreation and sport facilities were described in detail.

EVIDENCE SYNTHESIS

Forty-two states had recreational user statutes that would potentially offer protection from liability for public schools. Protected activities listed in state statutes were summer sports (n=2); winter sports (n=22); athletic competition (n=1); sporting events and activities (n=1); exercise (n=4); and any other outdoor sport, game, or recreational activity (n=2). Specific protected physical activities listed were playing on playground equipment (n=1); running/jogging (n=2); roller-skating and rollerblading (n=4); skateboarding (n=2); disc golf (n=1); and bicycling (n=16).

CONCLUSIONS

This study suggests the need for further statutory liability protections for public schools, and immunity provisions that target activities conducive to physical activity, common on school grounds, and popular among community residents. It further suggests that empirical studies be conducted to examine school administrator's perceptions relevant to liability as a potential barrier to opening school sport and recreational facilities to members of the community outside of regular school hours.

Congenital central hypoventilation syndrome and the PHOX2B gene: a model of respiratory and autonomic dysregulation

The paired-like homeobox 2B gene (PHOX2B) is the disease-defining gene for congenital central hypoventilation syndrome (CCHS). Individuals with CCHS typically present in the newborn period with alveolar hypoventilation during sleep and often during wakefulness, altered respiratory control including reduced or absent ventilatory responses to hypercarbia and hypoxemia, and autonomic nervous system (ANS) dysregulation; however, a subset of individuals present well into adulthood. Thermoregulation is altered and perception of shortness of breath is absent, but voluntary breathing is retained. Structural and functional magnetic resonance imaging (MRI) and limited post-mortem studies in subjects with CCHS reveal abnormalities in both forebrain and brainstem. MRI changes appear in the hypothalamus (responsible for thermal drive to breathing), posterior thalamus and midbrain (mediating O(2) and oscillatory motor patterns), caudal raphé and locus coeruleus (regulating serotonergic and noradrenergic systems), the lateral medulla, parabrachial pons, and cerebellum (coordinating chemoreceptor and somatic afferent activity with breathing), and insular and cingulate cortices (mediating shortness of breath perception). Structural and functional alterations in these sites may result from PHOX2B mutations or be secondary to hypoxia/perfusion alterations from suboptimal management/compliance. The study of CCHS, with collaboration between physician-scientists and basic scientists, offers a rare opportunity to investigate control of breathing within the complex physiological network of the ANS.

Single ion implantation for single donor devices using Geiger mode detectors

Electronic devices that are designed to use the properties of single atoms such as donors or defects have become a reality with recent demonstrations of donor spectroscopy, single photon emission sources, and magnetic imaging using defect centers in diamond. Ion implantation, an industry standard for atom placement in materials, requires augmentation for single ion capability including a method for detecting a single ion arrival. Integrating single ion detection techniques with the single donor device construction region allows single ion arrival to be assured. Improving detector sensitivity is linked to improving control over the straggle of the ion as well as providing more flexibility in lay-out integration with the active region of the single donor device construction zone by allowing ion sensing at potentially greater distances. Using a remotely located passively gated single ion Geiger mode avalanche diode (SIGMA) detector we have demonstrated 100% detection efficiency at a distance of >75 microm from the center of the collecting junction. This detection efficiency is achieved with sensitivity to approximately 600 or fewer electron-hole pairs produced by the implanted ion. Ion detectors with this sensitivity and integrated with a thin dielectric, for example a 5 nm gate oxide, using low energy Sb implantation would have an end of range straggle of <2.5 nm. Significant reduction in false count probability is, furthermore, achieved by modifying the ion beam set-up to allow for cryogenic operation of the SIGMA detector. Using a detection window of 230 ns at 1 Hz, the probability of a false count was measured as approximately 10(-1) and 10(-4) for operation temperatures of approximately 300 K and approximately 77 K, respectively. Low temperature operation and reduced false, 'dark', counts are critical to achieving high confidence in single ion arrival. For the device performance in this work, the confidence is calculated as a probability of >98% for counting one and only one ion for a false count probability of 10(-4) at an average ion number per gated window of 0.015.

Carbon dioxide chemoreception and hypoventilation syndromes with autonomic dysregulation

Respiratory and autonomic disorders of infancy, childhood, and adulthood are a group of disorders that have varying presentation, combined with a range of severity of respiratory control and autonomic nervous system dysfunction. Within this group, congenital central hypoventilation syndrome and rapid onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation, exhibit the greatest respiratory control deficits, requiring supported ventilation as a mainstay of care. The discovery of the key role of the paired-like homeobox 2B gene in autonomic nervous system development, along with the identification of paired-like homeobox 2B gene mutations causing congenital central hypoventilation syndrome, has led to a fruitful dialog between basic scientists and physician-scientists, producing an explosion of knowledge regarding genotype-phenotype correlations in this disorder, as well as important animal models of chemosensory regulation deficit. Though the etiology of rapid onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation is still to be determined, recent studies have begun to carefully delineate the phenotype, suggesting that it too may provide fertile ground for research that both advances our knowledge and improves patient care.

Interaction between cellular voltage-sensitive conductance and network parameters in a model of neocortex can generate epileptiform bursting

We examined the effects of both intrinsic neuronal membrane properties and network parameters on oscillatory activity in a model of neocortex. A scalable network model with six different cell types was built with the pGENESIS neural simulator. The neocortical network consisted of two types of pyramidal cells and four types of inhibitory interneurons. All cell types contained both fast sodium and delayed rectifier potassium channels for generation of action potentials. A subset of the pyramidal neurons contained an additional slow inactivating (persistent) sodium current (NaP). The neurons with the NaP current showed spontaneous bursting activity in the absence of external stimulation. The model also included a routine to calculate a simulated electroencephalogram (EEG) trace from the population activity. This revealed emergent network behavior which ranged from desynchronized activity to different types of seizure-like bursting patterns. At settings with weaker excitatory network effects, the propensity to generate seizure-like behavior increased. Strong excitatory network connectivity destroyed oscillatory behavior, whereas weak connectivity enhanced the relative importance of the spontaneously bursting cells. Our findings are in contradiction with the general opinion that strong excitatory synaptic and/or insufficient inhibition effects are associated with seizure initiation, but are in agreement with previously reported behavior in neocortex.

Electrophysiologic activity and antiarrhythmic efficacy of CK-3579, a new class III antiarrhythmic agent with beta-adrenergic blocking properties

CK-3579 (N-[4-[2-hydroxy-3-[[2-[4-(1H-inidazol-1- yl)phenoxy]ethyl]amino]propoxy]phenyl]methanesulfonamide, HCL-[RS]), is a new class III antiarrhythmic agent with beta-adrenoceptor blocking properties shown to be effective in preventing ventricular arrhythmias in experimental animals. We examined the beta 1- and beta 2-adrenoceptor binding properties, cellular electrophysiology, and antiarrhythmic efficacy of CK-3579 and the two enantiomers CK-4000 (S) and CK-4001 (R). Both CK-3579 and CK-4000 were equipotent in displacing [3H]dihydroalprenolol from cardiac membranes (IC50 = 2.4 +/- 0.3 and 1.7 +/- 0.4 microM, respectively) and were approximately 23-59 times more selective for the heart receptor than the lung receptor. The IC50 for CK-4001 at the beta 1-adrenoceptor was 38.1 +/- 8 microM and > 100 microM at the beta 2-adrenoceptor. In isolated canine Purkinje fibers and ventricular muscle preparations, all three compounds increased action potential duration at 95% repolarization (APD95) with equal potency, having an average EC20 of approximately 1 microM in Purkinje fiber and 2 microM in ventricular muscle. No significant effects were observed on any other action potential (AP) parameters. In Purkinje fibers with APs shortened by isoproterenol, the class III activity of CK-4000 was significantly greater than that of CK-4001. CK-4000 inhibits the potassium delayed rectifier current Ik in a concentration-dependent manner in isolated feline ventricular myocytes. The IC50 for inhibition of fully activated current was 0.4 +/- 0.2 microM. Steady-state currents negative to -20 mV were unchanged by CK-4000, but the "hump" in the outward current between -20 and +30 mV was flattened.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellular electrophysiological effects of the class III antiarrhythmic agents sematilide and clofilium on rabbit atrial tissues

Sematilide (N-[2-(diethylamino)ethyl]-4- [(methylsulfonyl)amino]benzamide HCl) is a new class III antiarrhythmic agent that has been shown to be effective in preventing reentrant ventricular arrhythmias in experimental animals and humans. In this study, we examined the in vitro effects of sematilide (1-100 microM) on isolated sinoatrial (SA) node, atrioventricular (AV) node, and atrial muscle. These results were then compared to another class III agent, clofilium (1-30 microM). In SA nodal tissue, sematilide increased the action potential duration (APD) and spontaneous cycle length (SCL) in a concentration-dependent manner (EC20% = 15 +/- 3 and 54 +/- 13 microM, respectively). In addition, there was a slight reduction in maximum diastolic potential at 100 microM. Clofilium had similar class III effects, but was approximately 3 to 18 times more potent (EC20% = 6 +/- 2 and 3 +/- 1 microM for the APD and SCL, respectively). Neither agent had a significant effect on the slope of phase 4 nor on other action potential parameters. Results in AV nodal preparations were similar. Both sematilide and clofilium increased the APD and SCL in a concentration-dependent manner, with clofilium being approximately four to six times more potent than sematilide (EC20% for the APD and SCL for sematilide = 12 +/- 4 and 12 +/- 8 microM, respectively, and for clofilium = 2 +/- 1 and 3 +/- 2 microM, respectively). No significant effects were observed on other action potential parameters. Sematilide and clofilium increased the APD and effective refractory period (ERP) in atrial trabeculae in a concentration-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of ketotifen in the prophylaxis of seasonal allergic asthma

This double-blind parallel group study evaluated ketotifen 1 mg bid versus placebo in the treatment of 30 adult seasonally allergic asthmatics during the course of the spring pollen season. Those individuals on placebo had a fall in FEV1 through the pollen season, those on Ketotifen generally did not, and some individuals, in fact, showed improvement. Those patients receiving ketotifen had fewer allergic symptoms, better exercise tolerance, and in general had a better spring. This study demonstrated that ketotifen may have some benefit in the treatment of adult allergic asthma.

Use of Seralyzer system for theophylline level determination in an office setting

Theophylline levels were measured on 63 plasma samples by both high pressure liquid chromatography and Seralyzer methods with excellent correlation. Seralyzer results were obtained quickly and easily in an office setting and offered the additional advantage of allowing accurate measurements on finger-stick samples.

Comparison of nebulized terbutaline (TERB) and subcutaneous epinephrine (EPI) in the treatment of acute asthma

The purpose of this study was to compare nebulized terbutaline 5 mg vs. subcutaneous epinephrine (1/1000, 0.3 cc) in the treatment of acute exacerbations of asthma in adult patients. Patients with a known diagnosis of asthma, who presented to the investigators in acute respiratory distress, without any previous adrenergic agents for six hours, were the subjects for this study. There were 33 patients enrolled in the study between 16 and 64 years of age. The results indicate both treatment groups gave significant increases in pulmonary function at all times when compared to baseline (p less than 0.001). Nebulized terbutaline and subcutaneous epinephrine appeared equally effective in the treatment of acute exacerbations of asthma, without significant differences in bronchodilator effectiveness or side effects.

Private health insurance plans in 1978 and 1979: a review of coverage, enrollment, and financial experience

The private health insurance industry collected $55.9 billion in premiums in 1979 and returned $50.2 billion in benefits to its subscribers. Premiums rose 12.4 percent, slightly faster than in 1978 when premiums rose 11.4 percent, to $49.7 billion. Benefits rose 11.4 percent in 1979, down from the 12.6 rate in 1978. After operating expenses were deducted, the industry showed underwriting losses of $1.4 billion in 1979 and $1.5 billion in 1978. About 78 percent of the population was insured for hospital care, 76 percent for x-ray and laboratory examinations, and about 76 percent for surgical services in 1979. Smaller percentages had coverage for other types of care. An estimated 64 percent of the aged bought private hospital insurance, and about 43 percent bought surgical insurance, mostly to supplement Medicare benefits. An estimated 12 percent of persons under age 65 had no protection against the cost of hospital care either through private insurance or a public program such as Medicare or Medicaid.

Bioavailability and multiple dose characteristics of a new sustained release theophylline tablet

Bioavailability and theophylline level variability were compared between a standard theophylline elixir and a new sustained release theophylline tablet. The results demonstrate a good bioavailability and a reduced dosage interval with less theophylline level variability for the sustained release tablet, administered every 12 hours, than with the immediate release product, every six hours.

Terbutaline in the treatment of chronic urticaria

Eighteen patients with chronic urticaria were evaluated concerning the benefit of oral sympathomimetic therapy. No significant differences could be found between the sympathomimetic agent (terbutaline) and a placebo in the various clinical parameters evaluated. The authors conclude that the efficacy of this drug is doubtful in the treatment of chronic urticaria.