Validation of Polyvinylidene Fluoride Impedance Sensor for Respiratory Event Classification during Polysomnography in Children.

STUDY OBJECTIVES: Polysomnography is the gold standard for diagnosis and characterization of severity of sleep-disordered breathing. Accuracy and reliability of the technology used are critical to the integrity of the study's interpretation. Strict criteria for obstructive sleep apnea in children are lacking and diagnosis often requires consideration of frequency of respiratory events in addition to other measures. Current American Academy of Sleep Medicine recommendations for pediatric patients includes use of respiratory inductance plethysmography (RIP) belts, whereas polyvinylidene fluoride (PVDF) belts are currently only acceptable for use in adults. We hypothesized that PVDF belts would be equally effective as RIP belts for detection of respiratory effort and events in children. METHODS: Children ages 2-17 y were recruited from a large pediatric tertiary referral center after obtaining consent for participation. Fifty subjects were recruited (average age, 7.8 y). Clinically relevant limits of agreement were predetermined to be a difference in total count of obstructive or central apneas or hypopneas of ± 5 events. RESULTS: Scoring of respiratory events was not significantly different by belt type based on Bland-Altman plots of total apnea-hypopnea index and obstructive apneas. Obstructive hypopneas scoring ranged beyond our clinical limit of agreement. Findings in obese subjects were consistent with the larger sample with the exception of an increase in outliers. Artifact amount was comparable (RIP 10.9% ± 22.5% and PVDF 10.5% ± 19.5%). CONCLUSIONS: Based on these findings, PVDF belts appear to be as effective as RIP belts in detection of respiratory effort and events in children. COMMENTARY: A commentary on this article appears in this issue on page 159.

Metabolic alterations in adolescents with obstructive sleep apnea.

IMPORTANCE: Obesity is one of the leading health concerns in developed and in developing countries. The risk of obstructive sleep apnea (OSA) is greatly increased by obesity. Obesity is known to be associated with the Metabolic Syndrome and cardiovascular disease in adults. This same association in children is not well defined. Understanding the relationship of obesity, OSA, and metabolic alterations in children would improve understanding of the risks of cardiovascular disease into adulthood. OBJECTIVE: To evaluate the association of OSA and metabolic outcomes, including lipid variables and insulin resistance, in obese adolescents. METHODS: Retrospective, case-control series at a tertiary care children's hospital. Obese adolescents aged 12-18 years who underwent overnight polysomnography (PSG) and routine laboratory testing for lipid levels, fasting glucose, and insulin from January 1, 2006 to December 31, 2012. RESULTS: A total of 42 patients with a mean age of 14.1±1.9 years were analyzed. Nineteen (45.2%) were male. The mean body mass index (BMI) z score was 2.23±0.86, and all patients were obese (BMI z score >95th percentile). Triglyceride, fasting blood glucose, insulin, and homeostasis model assessment-insulin resistance (HOMA-IR) levels were significantly higher in patients with OSA when compared to those with No-OSA (p<0.01). There was incremental worsening of insulin and HOMA-IR with greater severity of OSA. The apnea-hypopnea index (AHI) was positively and significantly correlated with blood glucose and HOMA-IR (p=0.01and p<0.001, respectively). Multiple linear regression analysis showed that the AHI was a predictor of blood glucose (p=0.04) and HOMA-IR (p=0.01) independent of age, gender, total sleep time and BMI z score. Logistic regression analysis showed that elevated levels of blood glucose predicted severe OSA (p=0.02) independent of gender and BMI z score. Elevation in HOMA-IR predicted severe OSA (p=0.004). CONCLUSION: OSA severity is associated with increased fasting insulin, blood glucose and HOMA-IR even after controlling for the age, and BMI z score in adolescents.

An official ATS clinical policy statement: Congenital central hypoventilation syndrome: genetic basis, diagnosis, and management.

BACKGROUND: Congenital central hypoventilation syndrome (CCHS) is characterized by alveolar hypoventilation and autonomic dysregulation. PURPOSE: (1) To demonstrate the importance of PHOX2B testing in diagnosing and treating patients with CCHS, (2) to summarize recent advances in understanding how mutations in the PHOX2B gene lead to the CCHS phenotype, and (3) to provide an update on recommendations for diagnosis and treatment of patients with CCHS. METHODS: Committee members were invited on the basis of their expertise in CCHS and asked to review the current state of the science by independently completing literature searches. Consensus on recommendations was reached by agreement among members of the Committee. RESULTS: A review of pertinent literature allowed for the development of a document that summarizes recent advances in understanding CCHS and expert interpretation of the evidence for management of affected patients. CONCLUSIONS: A PHOX2B mutation is required to confirm the diagnosis of CCHS. Knowledge of the specific PHOX2B mutation aids in anticipating the CCHS phenotype severity. Parents of patients with CCHS should be tested for PHOX2B mutations. Maintaining a high index of suspicion in cases of unexplained alveolar hypoventilation will likely identify a higher incidence of milder cases of CCHS. Recommended management options aimed toward maximizing safety and optimizing neurocognitive outcome include: (1) biannual then annual in-hospital comprehensive evaluation with (i) physiologic studies during awake and asleep states to assess ventilatory needs during varying levels of activity and concentration, in all stages of sleep, with spontaneous breathing, and with artificial ventilation, and to assess ventilatory responsiveness to physiologic challenges while awake and asleep, (ii) 72-hour Holter monitoring, (iii) echocardiogram, (iv) evaluation of ANS dysregulation across all organ systems affected by the ANS, and (v) formal neurocognitive assessment; (2) barium enema or manometry and/or full thickness rectal biopsy for patients with a history of constipation; and (3) imaging for neural crest tumors in individuals at greatest risk based on PHOX2B mutation.

Congenital central hypoventilation syndrome from past to future: model for translational and transitional autonomic medicine.

The modern story of CCHS began in 1970 with the first description by Mellins et al., came most visibly to the public eye with the ATS Statement in 1999, and continues with increasingly fast paced advances in genetics. Affected individuals have diffuse autonomic nervous system dysregulation (ANSD). The paired-like homeobox gene PHOX2B is the disease-defining gene for CCHS; a mutation in the PHOX2B gene is requisite to the diagnosis of CCHS. Approximately 90% of individuals with the CCHS phenotype will be heterozygous for a polyalanine repeat expansion mutation (PARM); the normal allele will have 20 alanines and the affected allele will have 24-33 alanines (genotypes 20/24-20/33). The remaining approximately 10% of individuals with CCHS will have a non-PARM (NPARM), in the PHOX2B gene; these will be missense, nonsense, or frameshift. CCHS and PHOX2B are inherited in an autosomal dominant manner with a stable mutation. Approximately 8% of parents of a CCHS proband will be mosaic for the PHOX2B mutation. A growing number of cases of CCHS are identified after the newborn period, with presentation from infancy into adulthood. An improved understanding of the molecular basis of the PHOX2B mutations and of the PHOX2B genotype/CCHS phenotype relationship will allow physicians to anticipate the clinical phenotype for each affected individual. To best convey the remarkable history of CCHS, and to describe the value of recognizing CCHS as a model for translational and transitional autonomic medicine, we present this review article in the format of a chronological story, from 1970 to the present day.

Sudden infant death syndrome: another year of new hope but no cure.

PURPOSE OF REVIEW: Sudden infant death syndrome has inspired increasingly sophisticated studies at a time when rates are declining because of the Back-to-Sleep campaign, but ethnic disparities are widening. This review evaluates and discusses original, recent research in this area. RECENT FINDINGS: The epidemiology of sudden infant death syndrome was evaluated, corroborating known risk factors and identifying new risk factors such as socioeconomic depression and air pollution. Deficits in our understanding of risk factors for this syndrome persist, suggesting a need for ethnicity-specific education, especially among the underserved. Both autopsy and genetic testing were found to improve diagnostic accuracy or identify other causes of death (e.g. long Q-T syndrome). Debate persists over counseling regarding pacifiers and co-sleeping within the context of breastfeeding. Support was found for a relationship between sudden infant death syndrome and autonomic dysregulation via the serotonergic pathway, but more research is needed. SUMMARY: The cause of sudden infant death syndrome remains elusive. Recent studies, however, suggest that improved culturally sensitive educational programs, increased diagnostic specificity, and further clarification of the link between genetics and developmental stage might further decrease the number of infants lost to this devastating disease and elucidate the mechanism(s) responsible for this syndrome.