Sarah A. Immanuel

Respiratory timing and variability during sleep in children with sleep-disordered breathing

Sleep-disordered breathing (SDB) in children is assessed by quantification of hypopnea and apnea events. Little is known, however, about respiratory timing and breath-to-breath variability during sleep. The aim of this study was to investigate respiratory parameters across sleep stages in children with SDB before and after treatment compared with healthy children. Overnight polysomnography (PSG) was conducted in 40 children with SDB prior to and 6 mo following adenotonsillectomy. For comparison, a control group of 40 healthy sex- and age-matched children underwent two PSGs at equivalent time points but without intervention. The following variables were measured breath by breath during obstruction-free periods in stage 2 nonrapid eye movement (NREM), stage 4 NREM, and REM sleep: inspiratory time (Ti), expiratory time (Te), total time (Ttotal), inspiratory duty cycle (DC; =Ti/Ttotal), respiratory frequency (fR), and SD of the parameters Ti, Te, fR, and DC. Variability in waveform morphology was also computed using the residue of respiratory patterns. The severity of SDB was relatively mild in the study cohort (obstructive apnea hypopnea index: baseline, 5.1 ± 9.4 vs. 0.1 ± 0.2, P < 0.001; follow-up, 0.3 ± 0.3 vs. 0.8 ± 1.0, P < 0.01). Compared with healthy controls, children with SDB showed significantly longer Ti and Te and a lower fR at the baseline study. These differences were not significant after adenotonsillectomy. Sleep stages were associated with significant differences in all of the respiratory measures in both groups of children. In conclusion, children with relatively mild SDB showed prolonged inspiration and expiration indicative of chronic narrowing of the upper airway. Treatment of SDB normalizes respiratory timing. Documentation of these parameters may aid in both understanding and management of children with SDB.

Heartbeat Evoked Potentials during Sleep and Daytime Behavior in Children with Sleep-disordered Breathing

RATIONALE Event-related brain potentials allow probing of cortical information processing, but when evoked with externally induced stimuli may disrupt sleep homeostasis and do not provide insight into intrinsic cortical information processing. To investigate if cortical processing of intrinsic information in children with sleep-disordered breathing (SDB) is different from healthy children and, if so, whether it resolves with treatment, we used heartbeat as a source of interoceptive event-related brain potentials. OBJECTIVES To investigate heartbeat evoked potentials (HEP) during sleep in healthy children and in children with SDB before and after treatment and to explore if there are any associations between HEP and daytime behavioral deficits in children with SDB. METHODS Heartbeat-aligned EEG was assessed for presence of HEP within stage 2, slow-wave sleep, and REM sleep in 40 children with primarily mild to moderate SDB before and after adenotonsillectomy and in 40 matched control subjects at similar time points. MEASUREMENTS AND MAIN RESULTS In both groups, nonrandom HEP were present in all sleep stages analyzed; however, amplitude of HEP were significantly lower in children with SDB during non-REM sleep (stage 2: P = 0.03; slow-wave sleep: P = 0.001). This between-group difference was not significant post adenotonsillectomy. Significant negative associations between HEP and daytime behavioral scores were observed at baseline. CONCLUSIONS Children with SDB displayed reduced HEP amplitude during sleep, which might be indicative of changes in afferent sensory inputs to the brain and/or signify differences in sensory gating of cardiac-related information in the insular cortex. Adenotonsillectomy appears to reverse this effect.

Respiratory Cycle-Related Electroencephalographic Changes during Sleep in Healthy Children and in Children with Sleep Disordered Breathing

STUDY OBJECTIVE To investigate respiratory cycle-related electroencephalographic changes (RCREC) in healthy children and in children with sleep disordered breathing (SDB) during scored event-free (SEF) breathing periods of sleep. DESIGN Interventional case-control repeated measurements design. SETTING Paediatric sleep laboratory in a hospital setting. PARTICIPANTS Forty children with SDB and 40 healthy, age- and sex-matched children. INTERVENTIONS Adenotonsillectomy in children with SDB and no intervention in controls. MEASUREMENTS AND RESULTS Overnight polysomnography; electroencephalography (EEG) power variations within SEF respiratory cycles in the overall and frequency band-specific EEG within stage 2 nonrapid eye movement (NREM) sleep, slow wave sleep (SWS), and rapid eye movement (REM) sleep. Within both groups there was a decrease in EEG power during inspiration compared to expiration across all sleep stages. Compared to controls, RCREC in children with SDB in the overall EEG were significantly higher during REM and frequency band specific RCRECs were higher in the theta band of stage 2 and REM sleep, alpha band of SWS and REM sleep, and sigma band of REM sleep. This between-group difference was not significant postadenotonsillectomy. CONCLUSION The presence of nonrandom respiratory cycle-related electroencephalographic changes (RCREC) in both healthy children and in children with sleep disordered breathing (SDB) during NREM and REM sleep has been demonstrated. The RCREC values were higher in children with SDB, predominantly in REM sleep and this difference reduced after adenotonsillectomy. CITATION Immanuel SA, Pamula Y, Kohler M, Martin J, Kennedy D, Saint DA, Baumert M. Respiratory cycle-related electroencephalographic changes during sleep in healthy children and in children with sleep disordered breathing.

Increased thoracoabdominal asynchrony during breathing periods free of discretely scored obstructive events in children with upper airway obstruction

ObjectiveThis study aims to investigate the impact of upper airway obstruction (UAO) in children by measuring thoracoabdominal asynchrony (TAA) during periods of sleep apnea/hypopnea and during scored-event-free (SEF) breathing periods.MethodsRespiratory inductive plethysmographic signals were extracted from polysomnographic data, recorded before and after adenotonsillectomy in 40 children with UAO and 40 healthy, matched children at equivalent time points. Thoracoabdominal asynchrony was computed using a Hilbert transform-based phase difference estimation method in SEF periods during stage 2, stage 4 non-rapid eye movement (NREM), and rapid eye movement (REM) sleep and compared between the groups.ResultsAt baseline, in the UAO group, TAA during obstructions were significantly higher than TAA during SEF periods in both stage 2 and REM sleep. Compared to controls, children with UAO had a significantly higher TAA during SEF periods in stage 2, stage 4 sleep, and REM sleep. This between-group difference was not significant post adenotonsillectomy. UAO group showed a significant decrease in TAA compared to their baseline during SEF stage 2 and 4 NREM, but not in REM.ConclusionUpper airway obstruction in children is associated with increased TAA during SEF periods, indicative of continuous partial obstruction of the upper airway. Adenotonsillectomy decreased this effect significantly in non-REM sleep as evidenced by reduced asynchrony levels post-surgery. TAA assessment during sleep may therefore provide additional diagnostic information.

Effect of respiration on heartbeat-evoked potentials during sleep in children with sleep-disordered breathing

OBJECTIVE Heartbeat-evoked potentials (HEPs) in electroencephalogram (EEG) provide a quantitative measure of cardiac interoception during sleep. We previously reported reduced HEPs in children with sleep-disordered breathing (SDB), indicative of attenuated cardiac information processing. The objective of this study was to investigate the link between HEP and respiration. PATIENTS/METHODS From the overnight polysomnograms of 40 healthy children and 40 children with SDB, we measured HEPs during epochs of stage 2, slow-wave and rapid eye movement (REM) sleep free of abnormal respiratory events. HEPs were analysed with respect to respiratory phase. RESULTS We observed a marked association between respiratory phase and HEP in children with SDB during REM sleep, but not in normal children. In children with SDB, HEP waveforms were attenuated during expiration compared to inspiration. Following adenotonsillectomy, expiratory HEP peak amplitude increased in the SDB children and was no longer different from those of normal children. CONCLUSIONS The expiratory phase of respiration is primarily associated with attenuated cardiac information processing in children with SDB, establishing a pathophysiological link between breathing and HEP attenuation.

Thoraco-abdominal asynchrony in children during quiet sleep using Hilbert transform

We present a technique based on the Hilbert transform to quantify the thoraco-abdominal asynchrony (TAA) based on the phase shift between ribcage (RC) and abdomenal (AB) breathing signals acquired using respiratory inductive plethysmography (RIP). We employed this method to investigate RIP during overnight polysomnography (PSG) in 40 healthy children for analysis of their breathing patterns in various stages of sleep (ss 2, 3, 4 and REM) and in two common sleeping positions (supine and lateral). RIP signals free of respiratory or movement artifacts were segmented into 30 second epochs. Those epochs with maximum power in the quiet breathing frequency range and positional invariance throughout were included for further processing. TAA was calculated from corresponding RC and AB excursions. We found a statistically significant influence of sleep position on the level of TAA in all stages of non-REM sleep. In conclusion, the Hilbert transform provides a simple tool for the quantification of thoraco-abdominal asynchrony.

Adenotonsillectomy for childhood obstructive sleep apnoea reduces thoraco-abdominal asynchrony but spontaneous apnoea-hypopnoea index normalisation does not.

The efficacy of adenotonsillectomy for treating obstructive sleep apnoea syndrome (OSAS) in children has been established, but its precise effects on inspiratory effort are not well documented. In 353 children enrolled in the Childhood Adenotonsillectomy Trial, randomised to undergo either early adenotonsillectomy (n=182) or a strategy of watchful waiting with supportive care (WWSC) (n=171), thoraco-abdominal asynchrony (TAA) was analysed during quiet, non-apnoeic and non-hypopnoeic breathing during sleep at baseline and at 7 months using overnight polysomnography. Children who underwent early adenotonsillectomy demonstrated a reduction in TAA post-surgery while the WWSC arm showed no change. On assessing TAA with regard to normalisation of clinical polysomnography findings at follow-up, TAA was reduced in children who had surgical resolution of OSAS (based on apnoea–hypopnoea index), but not in children who displayed spontaneous normalisation of apnoea–hypopnoea index. In the latter group, TAA was inversely correlated with quality of life. We conclude that adenotonsillectomy reduces TAA during quiet sleep. Monitoring of instantaneous TAA may yield additional insight in the dynamic changes of inspiratory effort. In combination with traditional indices of obstruction, TAA may more accurately characterise the degree of sleep-disordered breathing in children. Adenotonsillectomy for childhood obstructive sleep apnoea reduces respiratory effort during sleep http://ow.ly/TJcx304lKdm

The effect of adenotonsillectomy for childhood sleep apnoea on cardiorespiratory control

The efficacy of adenotonsillectomy for relieving obstructive sleep apnoea symptoms in children has been firmly established, but its precise effects on cardiorespiratory control are poorly understood. In 375 children enrolled in the Childhood Adenotonsillectomy Trial, randomised to undergo either adenotonsillectomy (n=194) or a strategy of watching waiting (n=181), respiratory rate, respiratory sinus arrhythmia and heart rate were analysed during quiet, non-apnoeic and non-hypopnoeic breathing throughout sleep at baseline and at 7 months using overnight polysomnography. Children who underwent early adenotonsillectomy demonstrated an increase in respiratory rate post-surgery while the watchful waiting group showed no change. Heart rate and respiratory sinus arrhythmia were comparable between both arms. On assessing cardiorespiratory variables with regard to normalisation of clinical polysomnography findings during follow-up, heart rate was reduced in children who had resolution of obstructive sleep apnoea syndrome, while no differences in their respiratory rate or respiratory sinus arrhythmia were observed. Adenotonsillectomy for obstructive sleep apnoea increases baseline respiratory rate during sleep. Normalisation of apnoea–hypopnoea index, spontaneously or via surgery, lowers heart rate. Considering the small average effect size, the clinical significance is uncertain. Adenotonsillectomy for childhood obstructive sleep apnoea increases respiratory rate during sleep http://ow.ly/Dptd300w9Pp

Altered Nocturnal Cardiovascular Control in Children With Sleep-Disordered Breathing

Study objectives To assess cardiovascular control during sleep in children with sleep-disordered breathing (SDB) and the effect of adenotonsillectomy in comparison to healthy nonsnoring children. Methods Cardiorespiratory signals obtained from overnight polysomnographic recordings of 28 children with SDB and 34 healthy nonsnoring children were analyzed. We employed an autoregressive closed-loop model with heart period (RR) and pulse transit time (PTT) as outputs and respiration as an external input to obtain estimates of respiratory gain and baroreflex gain. Results Mean and variability of PTT were increased in children with SDB across all stages of sleep. Low frequency power of RR and PTT were attenuated during non-rapid eye movement (REM) sleep. Baroreflex sensitivity was reduced in children with SDB in stage 2 sleep, while respiratory gain was increased in slow wave sleep. After adenotonsillectomy, these indices normalized in the SDB group attaining values comparable to those of healthy children. Conclusions In children with mild-to-moderate SDB, vasomotor activity is increased and baroreflex sensitivity decreased during quiet, event-free non-REM sleep. Adenotonsillectomy appears to reverse this effect.

Increased variability in respiratory parameters heralds obstructive events in children with sleep disordered breathing

Sleep disordered breathing (SDB) is characterized by repeated episodes of central or obstructive apneas, disturbing respiratory patterns. The purpose of this study is to quantify respiratory variability associated with apneic/hypopneic events by computing respiratory parameters and thoraco-abdominal asynchrony (TAA) over sleep periods preceding the occurrence of obstructive events in children with SDB. One minute artifact-free epochs of ribcage (RC) and abdominal (AB) signals were extracted from the respiratory inductive plethysmograph (RIP) channel of the PSG prior to the onset of each obstruction. Breath-by-breath values of TAA were computed using a Hilbert transform based technique that measures the phase shift between the RC and AB signals. In addition, the following parameters were computed breath-by-breath from the RC signal: inspiratory time (Ti), expiratory time (Te), total time (Ttot), and the inspiratory duty cycle (DC=Ti/Ttot). Standard deviation of the parameters (SD_TAA, SD_Ti, SD_Te, SD_Ttot, SD_DC) over each 1 min epoch were calculated and averaged over each subject with respect to sleep stage. For comparison, similar measures were computed from within quiet breathing periods of each subject. We found that breaths immediately before apnea/hypopneas were associated with a high degree of variability in respiratory timing and TAA. The proposed variability analysis of RIP signals may be useful for detecting acute epochs of respiratory instability in children with SDB.