Abstract
Purpose
Although the number of apnea–hypopnea episodes per hour apnea-hypopnea index (AHI) is typically used to evaluate sleep-disordered breathing (SDB) in adults, it does not provide an accurate characterization of SDB in children. We investigated differences in SDB patterns in children and adults to evaluate SDB severity in children.
Materials and methods
Fifteen adults (mean age, 45.3 ± 8.4 years) and 15 children (mean age, 6.7 ± 3.9 years) with adenotonsillar hypertrophy underwent standard polysomnography. The change of oxygen saturation (ΔSpO 2 ) was defined as the difference between baseline SpO 2 during stable nighttime breathing and the lowest SpO 2 accompanied by an apnea–hypopnea event. The number of apnea-hypopnea episodes was determined using two different criteria to define an episode (criterion 1: cessation of airflow for at least 10 s; criterion 2: cessation of airflow for at least two consecutive breaths).
Results
Mean ΔSpO 2 accompanied by obstructive apneas lasting ≤ 10 s was significantly greater in children than in adults, although there was no significant difference in the duration of apnea–hypopnea episodes. The slope of the regression line between ΔSpO 2 and apnea-hypopnea duration in children was greater than in adults (P < 0.005). AHI in children was higher when calculated using criterion 2 compared to criterion 1 (10.9 ± 9.4 vs. 6.5 ± 4.9/h, P = 0.003).
Conclusions
ΔSpO 2 is a good indicator of SDB severity in children, and should therefore be considered in the diagnosis and treatment of pediatric SDB along with AHI.
1
Introduction
Sleep-disordered breathing (SDB) is the most common pediatric sleep disorder, and imposes substantial adverse effects on overall quality of life, cognitive function, academic achievement, behavior, growth and development . Children often desaturate with short sleep apneas, as they have a lower functional residual capacity (FRC) and a faster respiratory rate than adults . Oxygen saturation level could be useful for examining pediatric SDB severity, and should therefore be included in criteria for evaluating SDB severity in children.
Children with SDB consume health care services at a higher rate than those without, primarily to treat respiratory diseases . SDB is associated with high cardiovascular disease morbidity in adults , with systemic hypertension a known complication of adult SDB . In children, not only is elevated diastolic blood pressure associated with SDB as it is in adults, it is also associated with behavior problems . For example, children with SDB show more symptoms of attention-deficit/hyperactivity and excessive daytime sleepiness compared to normal children . These findings suggest potential and partially irreversible cardiovascular, cognitive, and economic effects in children, and highlight the importance of early detection of pediatric sleep disorders.
Pediatric sleep research has long used interpretation of abnormal polysomnography (PSG) to assess SDB in children . Recently, interpretation of abnormal PSG results has led to the development of guidelines for describing SDB severity in adults. The apnea–hypopnea index (AHI) can be used to characterize SDB in adults, but does not provide an accurate characterization of SDB in children. A useful classification of pediatric SDB severity is thus required. Accordingly, this study examined differences in SDB patterns between adults and children to identify which variables most accurately reflect the extent of pediatric SDB.
2
Methods
2.1
Participants
This study was carried out according to the principles stated in the Declaration of Helsinki, and was approved by the Ethical Review Committee of Nagoya University. Participants were 15 adults (13 male and two female; mean age, 45.3 ± 8.4 years) and 15 children (nine boys and six girls; mean age, 6.7 ± 3.9 years) ( Table 1 ). All of the children, but none of the adults, suffered from adenotonsillar hypertrophy, which was diagnosed by flexible fiberoptic nasal endoscopy.
| Variables | Children (n = 15) | Adults (n = 15) |
|---|---|---|
| Age, year | 6.7 ± 3.9 | 45.3 ± 8.4 |
| Male, n (%) | 9(60.1) | 13(86.7) |
| Total sleep duration, min | 457.2 ± 105.0 | 503.3 ± 54.8 |
| Stage N1, % | 6.6 ± 5.2 | 32.9 ± 17.3 |
| Stage N2, % | 36.0 ± 15.6 | 47.7 ± 12.8 |
| Stage N3, % | 37.9 ± 18.6 | 5.3 ± 4.3 |
| Stage R, % | 15.2 ± 10.8 | 15.8 ± 8.3 |
| AHI, episodes/h | 5.6 ± 4.7 | 31.3 ± 15.7 |
| Lowest oxygen saturation, % | 89.6 ± 5.4 | 75.4 ± 8.2 |
| Arousal per hour, episodes/h | 11.6 ± 11.1 | 45.1 ± 20.2 |
2.2
Polysomnography
We performed standard PSG (ALICE 3; Respironics, Murrysville, PA, USA) with pulse oximetry for all participants. Children were studied for up to 12 h in a quiet, darkened room with an ambient temperature of 24 °C in the company of one of their parents. No drugs were used to induce sleep. We recorded the electroencephalogram, electrooculogram, electromyogram, and electrocardiogram continuously, and monitored respiration with an oronasal thermistor, a nasal pressure sensor and thoracoabdominal piezoelectric gauges.
We defined sleep stages and arousal according to published criteria . Obstructive apnea or presence of central sleep apnea was identified if airflow was absent or nearly absent for at least 10 s. Hypopnea was defined as a ≥ 50% reduction in airflow associated with arousal, awakening, or ≥ 3% desaturation, also for at least 10 s. Apnea in children was defined as cessation of airflow through the nose and mouth as measured by the thermistor and nasal pressure sensor, while respiratory effort continues (movements of the rib cage and abdomen) for at least two consecutive breaths. Hypopnea in children was defined as a ≥ 50% reduction in airflow associated with arousal, awakening, or ≥ 3% desaturation, also for at least two consecutive breaths. We determined the AHI as the number of apnea–hypopnea episodes per hour. We also calculated the number of episodes of oxygen desaturation ≥ 3% per hour (desaturation index: DSI), lowest oxygen saturation level (lowest SpO 2 ), and number of arousals per hour (arousal index). Adults with an AHI ≥ 5/h and Epworth sleepiness scale ≥ 11 , and children with an AHI ≥ 1/h, were diagnosed as having obstructive sleep apnea syndrome (OSAS) .
We defined the change in oxygen saturation (ΔSpO 2 ) as the difference between baseline and lowest SpO 2 in an apnea–hypopnea event. Baseline SpO 2 before an apnea–hypopnea event was selected from a period of stable breathing without apnea–hypopnea events. We calculated AHI using two different criteria and compared them. Using criterion 1, apnea or hypopnea was defined as cessation of airflow through the mouth and nose for more than 10 s; using criterion 2, apnea or hypopnea was defined as cessation of airflow through the mouth and nose for at least two consecutive respiratory cycles.
2.3
Statistical analysis
Data are presented as mean ± SD. We compared mean ΔSpO 2 values between children and adults using the unpaired t -test, and AHI values calculated using the two methods with the Student’s paired t -test. The correlation between ΔSpO 2 and apnea–hypopnea duration was assessed by simple regression analysis. The relationship between ΔSpO 2 and apnea-hypopnea duration was analyzed with ANCOVA between children and adults. All analyses were performed with StatView ver. 4.54 (SAS Institute Inc., Cary, NC). P < 0.05 was considered statistically significant.
2
Methods
2.1
Participants
This study was carried out according to the principles stated in the Declaration of Helsinki, and was approved by the Ethical Review Committee of Nagoya University. Participants were 15 adults (13 male and two female; mean age, 45.3 ± 8.4 years) and 15 children (nine boys and six girls; mean age, 6.7 ± 3.9 years) ( Table 1 ). All of the children, but none of the adults, suffered from adenotonsillar hypertrophy, which was diagnosed by flexible fiberoptic nasal endoscopy.
