Portuguese Version

Year:  2004  Vol. 70   Ed. 2 - (13º)

Artigo de Revisão

Pages: 232 to 237

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Obstructive Sleep Apnea Syndrome (OSAS) in children

Author(s): Fabiana C. P. Valera 1,
Ricardo C. Demarco 1,
Wilma T. Anselmo-Lima 2

Keywords: obstructive sleep apnea syndrome (OSAS), apnea, children, childhood

Abstract:
Obstructive Sleep Apnea Syndrome (OSAS) in childhood is becoming more important and its incidence is increasing. This increase mainly reflects as an improve in diagnosis, both because of better understanding and recognition of the symptoms the Syndrome causes in children, and because of better diagnostic complementary exams. In this article, the symptoms and the characteristics of OSAS related to childhood are reviewed. In addition, the causes and the consequences of OSAS on childhood development are discussed, as well as the current treatment strategies and their prognoses.

INTRODUCTION

OSAS (Obstructive Sleep Apnea Syndrome) was first described by Sir William Osler, in 18921: "Chronic increase of lymphoid tissue is a disease of major importance and may affect children's mental and body development. during the night, sleep is extremely disturbed, with noisy and difficult breathing, sometimes followed by long pauses and stridor. Children may wake up due to short of breath episodes". Only in 1976, Guilleminault et al.2 reported the first series of eight children with confirmed diagnosis of OSAS through polysomnography.

OSAS is a sleep disorder characterized by transient and prolonged partial or total obstruction of the upper airways interrupting ventilation during sleep and changing its patterns because of increased respiratory effort. It is differentiated from central apnea because the latter is not associated with respiratory effort, indicative of CNS-mediated disorder. Primary snoring is not associated with obstructive apnea, frequent awakenings during sleep or abnormalities in gas exchange and typically has benign and favorable outcomes.

It is estimated that 8 to 27% of children snore during sleep, and 2% have OSAS. OSAS occurs in childhood from neonatal to teenager years; however it is commonly found in preschool children, particularly those aged 2 to 6 years, and has the same prevalence in both genders4. This incidence has been increasing over the past years probably because of two factors: more accurate and early diagnosis and decrease in adenotonsillectomy procedures.

Sleeping characteristics of children

During non-REM (rapid eye movement) sleeping phase, ventilation is decreased but it is normal, and there is the occurrence of decreased respiratory volume and frequency, and residual functional capacity, in addition to increase in upper airways resistance. In REM sleeping phase, however, respiratory pattern is more erratic, with variable respiratory frequency and volume and common central apnea events. Intercostal muscle and upper airways hypotonia during REM phase are likely to drop functional residual capacity causing obstructive apnea.

Pediatric patients have increased ability to modulate airflow through respiratory center-mediated response. This modulation occurs both at rest due to increased basal neuromotor tonus and during response to stimuli such as sub-atmospheric pressure, hypercapnia or hypoxia. Muscular activity is important to preserve children's upper airways patency during sleep as an attempt to compensate those anatomically smaller airways. Such response decreases the tendency upper airways have to collapse, which is inversely proportional to age. Therefore, children typically snore less than healthy adults and rarely present obstructive apnea.

Younger children have their longest sleeping time during the day, and increased ratio of REM phase during sleep. Growth hormone is released in REM sleeping phase, therefore this sleeping phase is crucial to enable children to grow and thrive. In order to preserve this sleeping phase, children develop increased awakening treshold5.

Pathophysiology of OSAS in children

Sleep modifies functioning and control of respiratory system by decreasing respiratory stimuli. These modifications significantly change upper airways and gas exchange in healthy children and in children with respiratory or nervous system diseases6. Whereas muscle tonus is generally decreased during sleeping, particularly during REM phase, it is not uncommon to have highly symptomatic children during the night that would be asymptomatic during the day5. A minority of those children that have severe upper airways obstruction has loud breathing with marked respiratory effort even if they are awake. 6

Abnormalities in the EEG pattern during sleeping phase in children are rarely found, suggesting that if there are central effects to respond to hypoxia or hypercapnia, they are very mild.

In OSAS, upper airways of children present increased pharyngeal neuromotor tonus, especially in genioglossal muscle, basically resulting in partial and consistent obstruction of upper airways, including hypercapnia and hypoxia (known as obstructive hypoventilation). This pattern tends to extend itself along time if awakening does not occur5. Consequently, children are less subject to cyclic apneas with total occlusion of airflow and subsequent awakening, which are more common in adults4,5. Waking up is not common in children, and rare in younger children5. Prolonged and uninterrupted obstructive hypoventilation in children occurs also as a result from increased waking up threshold in response to OSAS.

Significant drop in saturation was reported in mild apneas (less intense and shorter) and during obstructive hypoventilation, due to its reduced residual functional capacity against adult population. A proper response pattern of upper airways occurs in response to stimuli such as hypoxia and hypercapnia, partially balancing airways' resistance increase and protecting them from total collapse4,5.

Causes

OSAS has multifactor etiology in children and occurs due to a combination of structural obstructive factor such as hypertrophy of tonsils, laryngomalacia, or craniofacial malformations, and neuromotor factors such as hypotonic pharyngeal muscle and neurological syndromes4. In some children, neuromotor factors are predominant in OSAS pathophysiology, while structural factors are predominant in others5.

The most common cause of OSAS is pharyngeal tonsils and/or palate hyperthrophy3,8,9. Generally those cases are also associated with neuronal factors, which can be evidenced with worsening of symptoms during the night, if the tonus of upper airways muscles is decreased. It is worth mentioning that OSAS intensity is not proportional to tonsil's size and those cases associated with tonsil hypertrophy could be totally cured with adenotonsillectomy. 6,8,9.

Obesity is also a common cause of OSAS in children: there is increased respiratory effort due to fat deposition around the pharynx and increased abdominal and chest volume. Similarly to other structural causes, neuromotor disorders should be present to generate OSAS; an evidence of this fact is the low incidence of OSAS in children that are only obese3,6,9.

Genetic syndromes are the most common causes of OSAS in breastfed infants, especially those related to hypoplasia of the mid-third of the face (Apert Syndrome), micrognathia (Pierre-Robin Syndrome), and skull base abnormalities (Arnold-Chiari Syndrome) or nose obstruction (CHARGE Syndrome).

Neuromuscular diseases may cause OSAS due to lack of coordination of the upper airways muscles that could be related to hypotonia or hypertonia of pharyngeal muscles. In these children, OSAS might also occur during daytime, and could be associated with deglutition and hypersalivation disorders. Some examples include cerebral palsy7, West Syndrome and muscle dystrophy.

Other less common factors that should be mentioned include laryngomalacia (primary cause of newborn stridor that might cause OSAS in some infants), structural brain malformations, metabolic diseases (mucopolysaccharidosis) and sickle cell anemia6. Viral respiratory infections and allergic rhinitis are not risk factors, but might exacerbate symptoms in OSAS pediatric patients6.

Diagnosis

Major OSAS symptom is snoring, which occurs in practically all OSAS patients, but its intensity is not related to severity of the disease8. Other common effects and symptoms are forced mouth breathing with costal retractions, which sometimes may be paradoxical retractions, agitation, coughing and choking during sleep, somnambulism, night enuresis and sudoresis. These children also move a lot during the night trying to sleep in positions that facilitate airflow, sometimes seated or with hyperextended neck8. Cyanosis is rarely found, but may occur in nursing babies4. Very young infants may present severe OSAS with mild or even absent snoring6.

Behavioral symptoms such as hyperactivity, behavioral problems (anxiety, irritability and aggressiveness), disorientation, morning confusion, retrograde amnesia and attention deficit might occur. Sleep fragmentation and day excessive sleepiness may occur in older children, but are rare in young infants3,5.

Snoring is hardly noticeable in infants, and particularly in breastfed babies, and symptoms may only include feeding difficulties (that require proper and effortless respiration), with cough and movement during the process. Other symptoms of this age group are related to behavioral and learning disorders and occasionally associated with night snoring. Clinical suspicion is harder in such cases, since symptoms are hardly ever simultaneously questioned 4,5,7.

Findings are generally poor and unspecific in clinical examination, including mouth breathing, nose obstruction, hyponasal voice and Elongated Face Syndrome (chronic mouth breathing resulting in increase of anterior height of the face - primarily on the inferior third, narrowing of nostrils, mandible and maxilla retraction and increased mandible inclination, related to lip and orofacial musculature hypotonia) (Figure 1).

Findings of the clinical history associated with physical examination are valid only as screening process, evaluating the patients that need further investigation8. Brouillette et al.10 evaluated the importance of having a score with clinical records and physical examination for detection of OSAS and reported sensitivity in 35% and specificity in 39% of the patients, which would, therefore, not be predictive of OSAS. Additional confirmation of diagnosis requires additional tests.

Polysomnography is considered the best diagnostic method 2,8,9,11, and can be performed at any age. It is particularly recommended in differentiating OSAS from primary snoring, central apnea, night seizure and narcolepsy4. It is also important to evaluate OSAS severity and immediate postoperative complication risks, as well as post-treatment follow up. Conversely, its high cost and complexity make it difficult to be used on a routine basis. It is required in cases with severe symptoms (mainly with absence of an apparent obstructing factor) and in cases with related pathologies that result in worsening of OSAS effects (syndrome diseases)9.

Polysomnography findings, however, are not related to clinical history nor to physical findings (e.g. level of adenoid/tonsillar obstruction) 4,7,8,11.

Other exams such as daytime polysomnography, video and audio recording during sleep and pulse oxymetry have high sensitivity, but low specificity 8. Therefore, negative exams do not exclude OSAS, and can even underestimate its severity, reducing their diagnostic importance.

Consequences

The major effects of OSAS in children are as follows:

 Cardiovascular: pulmonary hypertension (resulting from recurrent hypoxia and hypercapnia), which may lead to congestive heart failure and cor pulmonale. These conditions are currently rare, and are reversible after OSAS management. Arrhythmia, bradycardia and systemic artery hypertension were reported in children, but are less common than in adult patients9. Their presence is an indication of severity of OSAS. It is believed that OSAS pediatric patients are more likely to present hypertension in adult life than the population in general3,9.

 Low weight-height index: well known complication, it is believed that it may occur due to the four following factors: 1) decrease in calorie intake; 2) increased caloric expenditure due to increased respiratory effort; 3) decreased growth hormone release resulting from drop in REM sleep; 4) decreased response of end organs to growth factors. Although, the incidence has been currently decreasing3,9, some cases still occur, particularly in OSAS severe events, with onset before 3 years of age and in children with 21 trissomy, craniofacial anomalies and neuromuscular diseases 9. Growth recovery (also known as "catch-up grown") typically occurs after OSAS management.

 Neurocognitive: behavioral problems (e.g hyperactivity, aggressiveness and agitation), decreased concentration, day excessive sleepiness (in older children) and poor learning performance at school. Improvement of such disorders has been reported when OSAS was diagnosed and treated early3. If left untreated, particularly in critical development and cerebral growth periods, neurocognitive abnormalities may not be completely regressed, and children may experience sustained decreased learning12. In a recent study, Gozal (1998)12 demonstrated that in children with school learning problems the incidence of OSAS is 6 to 9-fold higher than in the pediatric population in general.

Treatment

Adenotonsillectomy is the treatment of choice for OSAS pediatric patients with tonsil hypertrophy4,8,11, even for the group of patients with related pathologies (e.g, obesity and neuromuscular diseases). In these cases, surgery is the initial treatment and other associated treatments are eventually required. The treatment of OSAS after adenotonsillectomy is successful in 80% 3,8of the children, however, adenoidectomy alone has not proved to be so effective 4,11.

Other surgeries (e.g. tracheostomy, uvulapalatopharyngoplasty, glossoplasty, septoplasty and mandible advancement and tongue reduction) could be indicated in specific cases, such as genetic syndromes, cerebral palsy and multiple craniofacial disorders.

Immediate postoperative complications of adenotonsillectomy in OSAS pediatric patients include pulmonary edema and respiratory failure secondary to obstruction of upper airways, demanding intensive postoperative care3,5,9. These complications are the most common ones if surgery is associated with the following risk factors: patient below 2 years of age, Respiratory Disorder Index (RDI) higher than 10/hour, minimum O2 saturations below 70%, moderate difficulty to improve weight-height index; related diseases (neuromotor, craniofacial syndromes, chromosome anomalies), hypotonia, cor pulmonale, pre-term history, uvulapalatopharyngoplasty. In cases of acute postoperative respiratory failure, CPAP (continuous positive airway pressure) or BiPAP (bilevel positive airway pressure) could be useful to avoid reintubation during immediate postoperative care3.

CPAP is indicated 3,4,8 in those cases in which adenotonsillectomy is not indicated (presence of small adenoid/tonsillar tissue), and in which surgery was not able to improve symptoms, or in other special conditions of OSAS associated with cranial malformation. Generally CPAP is well tolerated by most of the pediatric patients (approximately 80 to 86%) after a training period for the patient and family members 3,13. Over the last decade, CPAP has been increasingly used in children as a safe alternative to upper airways surgery or tracheostomy. Tracheostomy, however, may be required if other measures prove to be ineffective.

Drug therapy with topical steroids seems to be the only treatment that apparently decreases OSAS symptoms and polysomnography of patients with tonsilar hypertrophy if applied for a long-term basis (minimum of 6 weeks) 14. However, the percentage of patients that actually benefits from middle and long-term use of steroid drugs without recurrent events and, consequently, not requiring surgery remains unknown14.

Prognosis

Pediatric patients with mild to moderate apnea with complete improvement of symptoms do not need to undergo polysomnography after treatment. This examination is indicated for the patients with moderate to severe OSAS before treatment, obese or that have not experienced clinical improvement.

OSAS long-term prognosis and outcome in children are still unknown. The scientific literature has only one study that addressed such aspects and demonstrated that OSAS pediatric patients that had undergone adenotonsillectomy in childhood might have recurrence of the disease in adolescence.

CLOSING REMARKS

OSAS in childhood results in significant physical and neuropsychomotor impairment. Therefore, it should be early diagnosed and treated as an attempt to mitigate its quite deleterious effects to the proper development of the child.

Table 1. Main differences of OSAS between children and adults.




Figure 1. Chronic mouth breathing child with signs of Elongated Face Syndrome.

REFERENCES

1. Osler W. Chronic tonsillitis. In: The principles and practice of medicine. New York; Appletown and Co., 1892: 335-9.
2. Guilleminault C, Eldridge FL, Simmons FB, Dement WC. Sleep apnea in eight children. Pediatrics 1976; 58: 28-32.
3. Lipton AJ, Gozal D. Treatment of obstruction sleep apnea in children. Do we really know how? Sleep Med Rev 2003; 7: 61-80.
4. Ward SL, Marcus CL. Obstructive sleep apnea in infants and young children. J Clin Neurophysiol 1996; 13: 198-207.
5. Marcus CL. Pathophysiology of childhood obstructive sleep apnea: current concepts. Resp Physiol 2000; 119: 143-54.
6. American Thoracic Society. Standards and Indications for Cardiopulmonary Sleep Studies in Children. Am J Respir Crit Care Med 1996; 153: 866-78.
7. Sanchez-Armengol A, Capote-Gil F, Cano-Gomez S, Ayerbe-Garcia R, Delgado-Moreno F, Castillo-Gomez J. Polysomnographic studies in children with adenotonsillar hypertrophy and suspected obstructive sleep apnea. Pediatr Pulmonol 1996; 22: 101-5.
8. American Academy of Pediatrics. Clinical practice guideline diagnosis and management of childhood obstructive sleep apnea syndrome. Pediatrics 2002; 109: 704-12.
9. American Thoracic Society. Cardiorespiratory sleep studies in children. Am J Respir Crit Care Med 1999; 160: 1381-7.
10. Brouillette RT, Morielle A, Leimanis A, Waters KA, Luciano R, Ducharme FM. Nocturnal pulse oxymetry as an abbreviated testing modality for pediatric obstructive sleep apnea. Pediatrics 2000; 105: 405-12.
11. Nieminen P, Tolonen U, Löppönen H. Snoring and obstructive sleep apnea in children - a 6-month follow-up study. Arch Otolaryngol Head Neck Surg 2000; 126: 481-6.
12. Gozal D. Sleep-disordered breathing and school performance in children. Pediatrics 1998; 102: 616-20.
13. Marcus CL, Carroll JL, Bamford O, Pykiz P, Loughlin GM. Supplemental oxygen during sleep in children with sleep-disordered breathing. Am J Resp Crit Care Med 1995; 152: 1297-301.
14. Brouillette RT, Manoukian JJ, Ducharme FM, Oudiane K, Earle LG, Ladan S. Morielli A. Efficacy of fluticasone nasal spray for pediatric obstructive sleep apnea. J Pediatr 2001; 138: 838-44.
15. Guilleminault C. Treatments in obstructive sleep apnea. In: Guilleminault C, Partinen M, Eds. Obstructive sleep apnea syndrome. New York: Raven Press; 1990. p. 99-118.

1 Assistant Physician of Otorhinolaryngology , Hospital das Clínicas, Medical School, Ribeirão Preto - University of Sao Paulo.
2 Full Professor of Otorhinolaryngology, Medical School, Ribeirão Preto - University of Sao Paulo.
Affiliation: Otorhinolaryngology, Medical School, Ribeirão Preto - University of Sao Paulo (FMRP-USP).
Address Correspondence to: Fabiana C. P. Valera - Av. Bandeirantes, 3900 Monte Alegre Ribeirão Preto SP 14040-030.
Tel (55 16) 602-2863 - 602-2862 - Fax (55 16) 602-2860 - E-mail: facpvalera@uol.com.br

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