Maida Lynn Chen

Diaphragm pacers as a treatment for congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome is a rare syndrome present from birth, and is defined as the failure of automatic control of breathing. All patients with congenital central hypoventilation syndrome require life-long ventilatory support during sleep, although approximately a third of patients require ventilatory support 24 h per day. Diaphragm pacers offer a modality of ventilatory support that affords congenital central hypoventilation syndrome patients with maximal mobility for full-time ventilatory patients, and they may allow for a more normal lifestyle in the appropriate patient. They may permit tracheostomy decannulation in those requiring only support during sleep. Diaphragm pacing entails surgical placement of an electrode onto the phrenic nerve, connected to a subcutaneous receiver. There is an external battery-operated transmitter and antenna placed on the skin over the receiver. The transmitter emits energy, similar to radio transmission, which is converted into an electrical current by the receiver. This stimulates the phrenic nerve resulting in a diaphragmatic contraction. Settings on the transmitter include respiratory rate and electrical voltage, and are adjusted to give enough tidal volume to allow for adequate oxygenation and ventilation. Therefore, diaphragm pacing is an attractive alternative mode of mechanically assisted ventilation for many patients with congenital central hypoventilation syndrome.

Sleep problems in children with fetal alcohol spectrum disorders.

STUDY OBJECTIVES Sleep problems in children with fetal alcohol spectrum disorders (FASD) are reportedly common but not well characterized. Objectives were to: (1) assess sleep concerns in children with FASD using a caregiver-report survey, the Childrens Sleep Habits Questionnaire (CSHQ); (2) compare CSHQ results with those of previously reported community sample; and (3) describe pilot polysomnography findings in children with FASD. METHODS Children with FASD were recruited from a behavioral intervention study, and participating caregivers completed the CSHQ. CSHQ results were compared with the original data from a previously published community sample of similar age. Participants with FASD and elevated CSHQ scores were offered overnight polysomnography. RESULTS Thirty-three children with FASD (4.1-12.1 years) were enrolled; 85% of children with FASD scored above the clinical cutoff Total Score of 41, reflecting marked sleep disturbance. Elevated subdomain scores occurred primarily in areas concerning for pediatric insomnia. Those with comorbid ADHD had elevated CSHQ on additional subdomains with no difference in Total Scores. Compared with the community sample, children with FASD had higher Total Scores on the CSHQ (52 vs. 39, p < 0.001). Polysomnography, completed in 5 subjects, revealed mild sleep disordered breathing and fragmented sleep with elevated non-respiratory arousal indices. CONCLUSIONS Clinically significant sleep problems are present in children with FASD on both subjective and objective measures. Further investigation is needed to better describe these sleep disturbances and their impact on overall health and daytime neurobehavioral problems in this clinical population.

Sleep‐disordered breathing in children with thoracic insufficiency syndrome

Thoracic insufficiency syndrome (TIS) is a collection of chest and spine malformations that results in progressively restrictive pulmonary mechanics and an inability of the thorax to adequately support lung growth. Many children with TIS are too young to perform standard pulmonary function tests, yet need functional assessments of their restrictive thoracic disease. We report on the sleep architecture and frequency of sleep‐related breathing abnormalities in 11 children with TIS who underwent overnight polysomnography from retrospective chart review. Ten of 11 (92%) had sleep disordered breathing as defined by currently accepted criteria of apnea–hypopnea index (AHI) >2 events/hr. The median AHI was 4.3 events/hr, with obstructive hypopneas (median 3.7 events/hr) accounting for 75% of abnormalities. Respiratory events occurred most frequently during REM sleep (median REM‐AHI 17.3 events/hr), and were associated with oxyhemoglobin desaturation, and rarely carbon dioxide retention. Sleep disordered breathing with hypoxemia appears to be a common but under recognized problem among children with TIS. Polysomnogram may have a role as a non‐invasive screening tool used in conjunction with other functional respiratory assessments in children with TIS, and warrants further study in a prospective manner. Pediatr Pulmonol. 2010; 45:469–474.

Midfacial and Dental Changes Associated with Nasal Positive Airway Pressure in Children with Obstructive Sleep Apnea and Craniofacial Conditions.

STUDY OBJECTIVES Nasal positive airway pressure (nPAP) for treatment of pediatric obstructive sleep apnea (OSA) is a widespread therapy that currently lacks longitudinal data describing how mask pressure impacts the developing facial skeleton. This retrospective cohort study compared midfacial growth in pediatric patients with underlying craniofacial conditions diagnosed with OSA who were compliant vs. noncompliant with nPAP therapy, and explored correlations between demographic, medical, and sleep variables with annual rate of facial change. METHODS Records from Seattle Childrens Hospitals Craniofacial Center and Sleep Disorders Center were reviewed to identify patients prescribed nPAP for OSA with serial cephalographic images obtained during routine clinical care for concomitant craniofacial diagnosis. Lateral cephalometric analysis was used to determine mean annual change in midfacial structures from T1 (pre-nPAP) to T2 (post-nPAP) in compliant vs. noncompliant subjects. Compliance was indicated by nPAP usage of > 20 h/week for > 6 months. RESULTS 50 subjects were compliant with nPAP therapy (mean age 10.42 years) for an average of 2.57 years, and 50 subjects were noncompliant (mean age 8.53 years). Compliant subjects experienced negative mean annual change (retrusion) of the midface compared to forward growth seen in noncompliant subjects (SNA: -0.57° vs. 0.56°), counterclockwise rotation of palatal plane (SN-PP: -1.15° vs. 0.09°), and upper incisor flaring (U1-SN: 2.41° vs. -0.51°). CONCLUSIONS Pressure to the midface from compliant nPAP use may alter normal facial growth. Cephalometric findings indicate a greater need for collaboration between sleep medicine physicians and orthodontists to monitor midfacial growth during nPAP treatment.

Noninvasive Assessment of Cardiovascular Autonomic Control in Pediatric Obstructive Sleep Apnea Syndrome

Studies suggest that obstructive sleep apnea syndrome (OSAS) is causally related to abnormal cardiovascular autonomic control in adults, but this has not been established in pediatric OSAS. The goal of this study was to quantify autonomic system dysfunction, as manifested by cardiovascular response abnormalities, in children with OSAS. During wakefulness, we continuously measured the ECG, arterial blood pressure and airflow in each subject. These measurements were made during the following conditions: spontaneous breathing in the supine posture (baseline), spontaneous breathing in the standing posture (orthostatic stress); tracking of the subjects own prior spontaneous breathing pattern while supine (mental stress), and during a cold face challenge. Using spectral analysis and modeling techniques, we sought to computationally delineate the physiological mechanisms that mediate these abnormalities. Our preliminary results suggest that the autonomic effects of pediatric OSAS differ from those in adult in that parasympathetic activity remains relatively normal despite the elevated peripheral sympathetic drive

Noninvasive Assessment of Cardiovascular Autonomic Control in Congenital Central Hypoventilation Syndrome

The goal of this study was to quantify autonomic system dysfunction, as manifested by cardiovascular and respiratory response abnormalities, in patients with congenital central hypoventilation syndrome (CCHS). During wakefulness, we continuously measured the ECG, arterial blood pressure (ABP), airflow, end-tidal CO2partial pressure (PETCO2), and arterial oxygen saturation (SatO2) in each subject. These measurements were made during spontaneous breathing in supine, sitting and standing postures, and also when each subject tracked his/her prior spontaneous breathing pattern while supine. We also performed the cold face test, hyperoxic hypercapnic rebreathing and the isocapnic hypoxic rebreathing challenges. Using spectral analysis and modeling techniques, we sought to computationally delineate the physiological mechanisms that mediate these abnormalities, as well as to determine the extent to which these abnormalities are related to peripheral or central chemoreflex dysfunction. Our preliminary results support the notion that sympathetic tone is markedly elevated in CCHS, and that differences in autonomic control from normal controls can be delineated by observing the responses to different stressors.

Understanding and Managing Sleep Disruption in Children with FASD

Accumulating evidence has revealed high rates of sleep disruption among children with fetal alcohol spectrum disorder (FASD). Multiple animal and clinical studies have found a clear association between sleep problems and prenatal alcohol exposure, and recent research is beginning to characterize the types and extent of sleep disruption in FASD. Nevertheless, sleep disruption in children with FASD often goes unrecognized or is treated without referring to an evidence base. Childrens disrupted sleep interferes with parental sleep and increases caregiver burden, which is of particular importance for families raising children with FASD, a group with very high levels of caregiving stress. The literature supporting an association between sleep problems and deficits in emotional, behavioral, and cognitive function in children is compelling, but needs further investigation in children with FASD. This paper will review the current state of knowledge on sleep in FASD and recommend a rational approach to sleep interventions for affected children and their families.

Cardio-respiratory Uncoupling in Congenital Central Hypoventilation Syndrome

Congenital central hypoventilation syndrome (CCHS) is a rare disorder with failure of automatic control of breathing, defined by lack of an appropriate ventilatory response to hypercarbia and hypoxia. However, more detailed evaluation of cardiorespiratory coupling has not been previously performed in those with CCHS. We postulate that those with CCHS have disjointed cardiorespiratory responses to ventilatory challenges due to their alterations in sympathetic modulation. Therefore, we performed ventilatory rebreathing challenges with hypercarbia and hypoxia on 5 subjects with CCHS (age 21.2 plusmn 5.3 years; 3 females) and 7 controls (age 20.0 plusmn 4.0 years; 4 females). We measured breath-to-breath respiratory parameters (airflow, PETCO2, SaO2), ECG, and continuous non-invasive blood pressure. As previously shown, when compared to controls CCHS subjects lacked ventilatory responses to isocapnic hypoxia (p=0.004) and hyperoxic hypercarbia (p=0.002). During hypercapnia, both control and CCHS subjects had similar rates of decrease in R-R intervals (RRI; slope -1.3plusmn2.5 vs. -1.4plusmn1.1, n.s.) and increase in beat-to-beat averaged blood pressure (MBP; slope 1.2plusmn0.3 vs. 0.4plusmn0.1, n.s.) as PETCO2 increased. During hypoxia, both control and CCHS groups had similar rates of decrease in RRI (slope 14.2plusmn3.0 vs. 7.5plusmn3.9, n.s.) and increase in MBP (slope -1.11plusmn1.12 vs. -0.9plusmn0.8, n.s.) as SaO2 decreased. We conclude that despite having a markedly diminished ventilatory response to hypercarbia and hypoxia, subjects with CCHS have normal cardiovascular responses to these challenges. We speculate that this indicates that chemoreceptors are functional. Therefore the abnormality in ventilatory responses is located in the ventilatory controller