Genioglossus response to airway occlusion in apneic versus nonapneic infants

The ability to maintain pharyngeal patency is compromised in infants who have apneic episodes associated with airway obstruction. Since the genioglossus (GG) muscle is thought to be important in maintaining pharyngeal patency, we measured the GG EMG with sublingual surface electrodes during unobstructed breathing and in response to end-expiratory airway occlusion. Studies were performed in nine premature infants with mixed and obstructive apnea and in eight nonapneic control infants. Phasic GG EMG was usually absent during normal tidal breathing in both groups of infants, however, GG activity typically appeared during airway occlusion. The response of the GG muscle during airway occlusion differed between control and apneic infants. During the first three occluded inspiratory efforts, control infants had 42 +/- 5, 74 +/- 5, and 80 +/- 5% (mean +/- SEM) of their occlusions associated with a GG EMG response, respectively. In contrast, apneic infants had significantly fewer (13 +/- 4, 38 +/- 9, and 52 +/- 9%) occlusions associated with a GG EMG response. There was a delay in onset of the GG EMG when compared to the onset of the diaphragm EMG and initial negative esophageal pressure swing, but this delay decreased with each subsequent appearance of the GG EMG in both infant groups. Infants with mixed and obstructive apnea thus have decreased activation of their GG in response to occlusion which may reflect their inability to recruit dilating muscles of the upper airway during spontaneous airway obstruction.     

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

Normal children have a smaller upper airway than adults, but, nevertheless, snore less and have less apnea. We have previously shown that normal children have an upper airway that is resistant to collapse during sleep. We hypothesized that this resistance to collapse is due to preservation of upper airway neuromotor responses during sleep. Furthermore, we hypothesized that upper airway responses would be diminished in children with the obstructive sleep apnea syndrome (OSAS). We therefore compared the upper airway pressure-flow relationship during sleep between children with OSAS and controls. Measurements were made by correlating maximal inspiratory airflow with the level of nasal pressure applied via a mask. Neuromotor upper airway activation was assessed by evaluating the upper airway response to 1) hypercapnia and 2) intermittent, acute negative pressure. We found that children with OSAS had no significant response to either hypercapnia or negative pressure during sleep, compared with the normal children. After treatment of OSAS by tonsillectomy and adenoidectomy, there was a trend for normalization of upper airway responses. We conclude that upper airway dynamic responses are decreased in children with OSAS but recover after treatment. We speculate that the pharyngeal airway neuromotor responses present in normal children are a compensatory response for a relatively narrow upper airway. Further, we speculate that this compensatory response is lacking in children with OSAS, most likely due to either habituation to chronic respiratory abnormalities during sleep or to mechanical damage to the upper airway.     

Upper airway measurements during inspiration and expiration in infants

Accurate measurements of the upper airway of the infant are important but are difficult to obtain reliably because of the normal variation that occurs during respiration. X-ray films of the lateral upper airway were obtained during inspiration and expiration in healthy infants, by using as a timing device a respiration monitor which was wired to the x-ray machine and was attached to the abdominal wall of the infant. Cephalometric measurements were made of 44 "normal" full-term neonates and 29 infants at 6 weeks of age. Despite significant differences in head circumference between the sexes, only the nasion to sella length was significantly longer in the boys (P less than .01). The lateral upper airway measurements were independent of weight, head circumference, and sex in the neonates and infants at 6 weeks of age but were significantly smaller during inspiration than expiration (P less than .01). The measurements progressively increased from the middle to the posterior airway space at both ages. The middle airway space behind the caudal end of the hard palate was smaller during inspiration at 6 weeks of age compared to the neonate (P less than .01). During expiration, the posterior airway space was larger at 6 weeks compared to the neonate (P less than .01). The method described in this report enables reliable roentgenographic measurements to be made of the upper airway of the infant; normal values for the changes during inspiration and expiration are provided. This may assist in the evaluation of infants with suspected upper airway obstruction.     

Diaphragmatic and genioglossus electromyographic activity at the onset and at the end of obstructive apnea in children with obstructive sleep apnea syndrome

We studied the activity of the diaphragm and of the genioglossus at the onset and at the end of obstructive sleep apnea in children. Seven children (mean age 46 months, range 15-87) with obstructive sleep apneas mainly due to enlarged tonsils were tested during natural sleep. We recorded sleep stages (neurophysiological criteria), nasal and buccal air flow (thermistors), thoracoabdominal motion (magnetometers), genioglossus and diaphragm electromyographic activity (EMG) (surface electrodes), and transcutaneous partial pressure of oxygen (Radiometer 44 degrees C). A total of 153 obstructive apneas for the whole group of patients was studied. Compared to the preceding unoccluded breaths, genioglossus and diaphragm EMG data showed that 1) at the onset of obstructive apnea there was no significant decrease in genioglossus and/or diaphragm EMG, contrasting with published data for obese adults, and 2) at the end of obstructive apnea, significant preferential increase in genioglossus EMG, not related to the decrease in transcutaneous partial pressure of oxygen, was found as in obese adults. This study showed that different mechanisms may control the onset of obstructive apnea in children as compared to adults, whereas children and obese adults share the same preferential increase in genioglossus EMG at the end of obstructive apnea.     

Gastroesophageal reflux and apnea in prematurely born infants during wakefulness and sleep

The hypothesis that acid gastroesophageal reflux may be responsible for the persistence of apnea was tested on 20 prematurely born infants, at a median conceptional age of 38.7 weeks. Gastroesophageal reflux was identified using distal esophageal pH monitoring. Apneas of durations greater than 10 seconds were identified and classified as either central or obstructive and mixed, using recordings of respiration. Wakefulness, active sleep, and quiet sleep were identified using electroencephalography and by assessing eye movements. Of 134 episodes of acid gastroesophageal reflux in the 20 subjects, more occurred during wakefulness and during active sleep than during quiet sleep. A total of 139 apneas, predominantly of the obstructive and mixed type, occurred. No relationship could, however, be demonstrated, in this rather small number of patients, between the occurrence of gastroesophageal reflux and that of apneas.     

Effect of sleep state and position on the incidence of obstructive and central apnea in infants

Sixty-four infants with a history of apnea were studied to determine the effects of sleeping position and sleep state (rapid eye movement [REM]) v (non-rapid eye movement [NREM]) on the occurrence of central and obstructive apneas. All-night polysomnographic studies were conducted on each infant, and the spontaneous occurrence of central and obstructive apneic events was determined in the prone, supine, and side positions. Sleeping position did not significantly affect the rate or duration of central or obstructive apneas. Furthermore, neither central nor obstructive apneic episodes were significantly altered by sleep state. These data suggest that, in spite of an ostensible predisposition to upper airway obstruction in the supine position and during rapid eye movement sleep, neither sleeping position nor sleep state appears to affect the rate of duration of apneic events.     

Cardiorespiratory patterns during alarms in infants using apnea/bradycardia monitors

Evaluating the significance of alarms at home in infants monitored for apnea/bradycardia depends on subjective parental observations. Retrospective analysis of 165 event recordings made during alarms in 90 monitored infants indicated that alarms were due to prolonged (greater than 15 s) apnea (6%), bradycardia (14%), shallow breathing (19%), mechanical malfunction (55%), or other causes (6%). Also, 68 infants had pneumograms. Of the 37 infants with an abnormal pneumogram, 14% had an abnormal event recording. Of the 31 infants with a normal pneumogram, 16% had an abnormal event recording. All monitors were discontinued without complication after a negative event recording. It may be concluded that (1) event recordings can document cardiorespiratory patterns during alarms, (2) the majority of alarms occurring at home are not significant, and (3) pneumograms do not appear to indicate which infants are at risk for a future significant alarm.     

Nasal continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea in Hallermann-Streiff syndrome

An 8-year-old girl with Hallermann-Streiff syndrome (oculomandibulofacial syndrome) was examined. She had a history of severe snoring, reported nocturnal apnea, excessive daytime hypersomnolence, nocturnal enuresis, and failure to thrive. Overnight polysomnography confirmed severe obstructive sleep apnea. Long-term nasal continuous positive airway pressure (CPAP) therapy completely relieved the obstructive sleep apnea and was associated with improved weight gain and growth.     

Obesity and obstructive sleep apnea in children

The prevalence and severity of obesity in children and adolescent is dramatically increasing worldwide with a corresponding increase in the prevalence of obesity-associated morbidities particularly those involving OSAS and metabolic and cardiovascular sequelae. Obstructive sleep apnea and obesity hypoventilation syndrome are important and serious consequences of obesity, and may in fact mediate components of the association between obesity and metabolic and cardiovascular morbidities, most likely via potentiation of inflammatory cascades. It is anticipated that the increased prevalence of obesity in children and adolescents in our society will be accompanied by a steady increase in the incidence of OSAS. In this review, we will examine our current understanding of sleep-disordered breathing and associated morbidities in obese children, and summarize the range of therapeutic modalities currently available for this high-risk population.     

Eventration of the diaphragm in infants and children

The study reviews 18 infants and children with eventration of the diaphragm who were treated over a period of eight years. The affected diaphragm and pulmonary tissue were examined by light and electron microscopy. The 18 patients, ranging in age from 10 days to 6 years, were divided according to Thomas' classification into a group with the congenital (10 patients) and a group with the acquired type (8 patients). Fifteen of these patients underwent surgery with diaphragmatic plication. On microscopic examination, biopsies of the lung showed atelectasis and pneumonia. These pathological changes became increasingly diffuse and severe with age. The diaphragm in patients with the congenital type of eventration was occupied by diffuse fibroelastic tissue. In patients with the acquired type, the cross-striated muscles of the diaphragm showed degenerative changes such as fragmentation, and interstitial fibrosis of the diaphragm became prominent with age. The results of this clinical study suggest that, in order to reduce the pathological changes in the lung, early surgical plication should be performed even in patients with the acquired type, if respiratory and digestive symptoms are noted.     

鼻塞持续气道正压通气预防极低出生体重儿原发性呼吸暂停临床研究

目的 探讨鼻塞持续气道正压通气(nasal continuous positive airway pressure,NCPAP)预防极低出生体重儿(very low birth weight,VLBW)原发性呼吸暂停的有效性及临床价值.方法 以山东齐河县赵官中心医院新生儿科2005-2007年收治的27例极低出生体重儿为实验组,应用NCPAP辅助呼吸,并与27例未使用NCPAP的板低出生体重儿进行回顾性临床对照研究.结果 实验组应用NCPAP后,呼吸暂停次数明显减少,临床症状及血气指标明显改善,平均氧疗时间、每日体重增长克数、住院时间及存活率分别为9.4d,20.15g/d,76.7d,92.6%;而对照组相应指标分别为12.4d,18.9g/d,80.8d,88.9%.两组指标比较差异有统计学意义(P<0.05).结论 NCPAP可有效预防极低出生体重儿的原发性呼吸暂停,改善其临床症状和血气指标,缩短氧疗时间和住院天数,增加每日体重增长克数,降低呼吸衰竭、肺出血及其他临床并发症的发生率.