Upper airway dynamic responses in children with the obstructive sleep apnea syndrome

The perioperative implications of obstructive sleep apnea

Patients with obstructive sleep apnea provide significant challenges to the perioperative team. This disorder is often undiagnosed and coexists with other disease processes such as hypertension, congestive heart failure, and cor pulmonale. The prevalence of obesity in American society suggests that an increasing number of patients with sleep apnea will present for surgery. During the perioperative period, life-threatening problems can occur during anesthetic induction and emergence. The pathophysiology of obstructive sleep apnea is reviewed here along with the anesthesia implications of this disease process. Members of the perioperative team need to be aware of the implications of sleep apnea so that surgical outcomes can be optimized.

Pharyngeal critical pressure in children with mild sleep-disordered breathing

There is evidence that narrowing or collapse of the pharynx can contribute to obstructive sleep-disordered breathing (SDB) in adults and children. However, studies in children have focused on those with relatively severe SDB who generally were recruited from sleep clinics. It is unclear whether children with mild SDB who primarily have hypopneas, and not frank apnea, also have more collapsible airways. We estimated airway collapsibility in 10 control subjects (9.4 ± 0.5 yr old; 1.9 ± 0.2 hypopneas/h) and 7 children with mild SDB (10.6 ± 0.5 yr old; 11.5 ± 0.1 hypopneas/h) during stable, non-rapid eye movement sleep. None of the subjects had clinically significant enlargement of the tonsils or adenoids, nor had any undergone previous tonsillectomy or adenoidectomy. Airway collapsibility was measured by brief (2-breath duration) and sudden reductions in pharyngeal pressure by connecting the breathing mask to a negative pressure source. Negative pressure applications ranging from −1 to −20 cmH2O were randomly applied in each subject while respiratory airflow and mask pressure were measured. Flow-pressure curves were constructed for each subject, and the x-intercept gave the pressure at zero flow, the so-called critical pressure of the upper airway (Pcrit). Pcrit was significantly higher in children with SDB than in controls (−10.8 ± 2.8 vs. −15.7 ± 1.2 cmH2O; P < 0.05). There were no significant differences in the slopes of the pressure-flow relations or in baseline airflow resistance. These data support the concept that intrinsic pharyngeal collapsibility contributes to mild SDB in children.

Continuous positive airway pressure for children: A discussion on how to maximize compliance

As pediatric sleep facilities and resources expand, increasing numbers of children with sleep-disordered breathing requiring continuous positive airway pressure (CPAP) treatment are being identified. Despite extensive expertise in treating adults with CPAP, many centres have little experience using CPAP in the pediatric population. The successful initiation and continued effective treatment with CPAP requires a unique and specialized approach to the pediatric patient and their family. Nearly, half of children needing CPAP will be uncooperative upon initial exposure to this unusual treatment. This review aims to outline an approach to the successful initiation of CPAP treatment in children including some trouble-shooting strategies to maximize initial and ongoing compliance with prescribed therapy.

Adherence to and effectiveness of positive airway pressure therapy in children with obstructive sleep apnea

OBJECTIVES

Positive airway pressure therapy (PAP) is frequently used to treat children who have obstructive sleep apnea syndrome and do not respond to adenotonsillectomy. However, no studies have evaluated objectively adherence to PAP in children, and few studies have evaluated objectively the effectiveness of PAP. The objective of this study was to determine adherence and effectiveness of PAP (both continuous [CPAP] and bilevel [BPAP] pressure) in children with obstructive apnea.

METHODS

A prospective, multicenter study was performed of children who were randomly assigned in a double-blind manner to 6 months of CPAP versus BPAP. Adherence was measured objectively using the equipment's computerized output. Effectiveness was evaluated using polysomnography.

RESULTS

Twenty-nine children were studied. Approximately one third of children dropped out before 6 months. Of the 21 children for whom 6-month adherence data could be downloaded, the mean nightly use was 5.3 +/- 2.5 (SD) hours. Parental assessment of PAP use considerably overestimated actual use. PAP was highly effective, with a reduction in the apnea hypopnea index from 27 +/- 32 to 3 +/- 5/hour, and an improvement in arterial oxygen saturation nadir from 77 +/- 17% to 89 +/- 6%. Results were similar for children who received CPAP versus BPAP. Children also had a subjective improvement in daytime sleepiness.

CONCLUSIONS

Both CPAP and BPAP are highly efficacious in pediatric obstructive apnea. However, treatment with PAP is associated with a high dropout rate, and even in the adherent children, nightly use is suboptimal considering the long sleep hours in children.

Oxidant stress and inflammation in the snoring child: confluent pathways to upper airway pathogenesis and end-organ morbidity

Snoring in children is increasingly being recognized as a highly prevalent condition, and indicates the presence of heightened upper airway resistance during sleep. In this paper, we present evidence to support the hypothesis that local inflammatory processes within the upper airway contribute to the pathophysiology of adenotonsillar hypertrophy and altered reflexes potentially leading to increased propensity for upper airway obstruction during sleep. Furthermore, the cumulative evidence supporting multiorgan morbidity for sleep-disordered breathing (SDB) is reviewed, and a unified hypothesis of a triple risk model proposing oxidative-inflammatory mechanisms as mediating the morbid consequences of SDB is presented. This hypothetical working model incorporates both dose-dependent disease severity components, as well as environmental and genetic elements of susceptibility.

Influence of airway pressure on genioglossus activity during sleep in normal children

RATIONALE

Most children with obstructive sleep apnea are able to sustain stable breathing during portions of sleep, despite an anatomic predisposition toward airway collapse. This suggests that additional determinants of airway patency are active, such as neuromuscular compensation.

OBJECTIVES/METHODS

Using a custom intraoral surface electrode to record pharyngeal dilator muscle activity (the genioglossus [EMGgg]), we evaluated the muscle, ventilatory, and arousal responses to negative-pressure challenges during sleep in 19 healthy control children.

MEASUREMENTS AND MAIN RESULTS

In response to these challenges, we observed (1) marked variability in individual EMGgg responsiveness (peak EMGgg [mean+/-SD], 214+/-101% baseline), which was consistent within subjects; (2) a relationship between EMGgg activity and inspiratory flow and airway collapsibility; (3) reflex increases in flow (peak flow increase from challenge breaths 1-5 [mean+/-SD], 49+/-41% baseline) and respiratory rate often sufficient to sustain minute ventilation near baseline levels, without arousal; and (4) arousal threshold to be highest in stage 4, intermediate in stage 2, and lowest in REM sleep.

CONCLUSIONS

Healthy children have wide variation in upper airway neuromuscular compensatory responses and arousal thresholds that could represent intermediate phenotypes affecting the expression of sleep apnea. Children with robust upper airway neuromuscular responsiveness, or a very high arousal threshold, may be able to sustain minute ventilation when challenged with negative airway pressure.

Pediatric obstructive sleep apnea: the year in review

PURPOSE OF REVIEW

In recent years several daytime symptoms resulting from pediatric obstructive sleep apnea have been recognized that affect neurobehavioral and cognitive functioning. It is important to identify patients who will benefit from treatment. Up until now the systematic analysis of obstructive sleep apnea in children has been hindered by both variable diagnostic criteria and patient care protocols. This review examines the effects of obstructive sleep apnea in children as well as treatment outcomes. Recent data suggest that some diagnostic modalities may underestimate the prevalence of sleep-disordered breathing in children.

RECENT FINDINGS

A review of the data from the past year shows a significant correlation between obstructive sleep apnea and daytime symptoms. It also shows mitigation of these symptoms with appropriate treatment. The directed history and physical examination continue to be the most effective means of diagnosis in most affected children. The polysomnogram is considered the gold standard for diagnosis but may underestimate the presence of sleep-disordered breathing in children. Some children with the diagnosis of primary snoring will benefit from treatment.

SUMMARY

In view of the profound effects of obstructive sleep apnea in children, it is vital to develop an accurate and universal system for diagnosing and treating these patients. Adenotonsillar hypertrophy is the major cause of obstructive sleep apnea in children. A directed history and physical examination followed by tonsillectomy and adenoidectomy are effective in improving the physical sequelae and quality of life of affected children.

Obstructive Sleep Apnea Syndrome in Children

Obstructive sleep apnea syndrome is characterized by recurrent episodes of partial or complete obstruction of the upper airway during sleep. This results in the disruption of normal ventilation and sleep patterns. The symptoms, polysomnographic findings, pathophysiology, and treatment of obstructive sleep apnea syndrome are significantly different in children from those seen in adults.