Use of Sleep Endoscopy to Predict Outcomes of Pediatric Adenotonsillectomy
Condition: Obstructive Sleep Apnea
MeSH terms: Sleep Apnea Syndromes; Sleep Apnea, Obstructive
Study type: Observational

Summary: 
      Pediatric obstructive sleep apnea (OSA) is associated with heavy snoring and brief pauses in
      breathing during sleep. It affects at least 1-3% of the general pediatric population with
      greater prevalence among certain high risk groups such as children with obesity, Down
      syndrome, craniofacial anomalies, or neuromuscular disorders. Several studies have shown
      that, even after having adenotonsillectomy (AT), approximately 30% of children continue to
      struggle with OSA. They further found that older children (age > 7 yrs), obesity, and high
      pre-operative OSA severity were all risk factors contributing to residual OSA. Despite these
      known risk factors, the ability to predict each individual patient's risk of residual OSA
      after tonsil surgery is difficult. Determining what tool will best predict residual OSA is an
      important step towards more effective post-surgery OSA management.

      The purpose of this study is to determine whether sleep endoscopy can predict whether their
      AT will be successful as a treatment for OSA. Our hypothesis is that subjects with multiple
      areas of obstruction in addition to large tonsils will be more likely to have residual OSA
      after AT. Sleep endoscopy is a procedure performed during drug-induced sleep that involves
      passing a flexible endoscope through the subject's nose into the back of the throat to look
      for sources of obstruction while breathing spontaneously.

      This will be a prospective cohort study examining subjects between the ages of 2 and 18 who
      are having AT for treatment of obstructive sleep apnea (OSA) and are considered high risk for
      residual OSA after surgery. High risk will be defined based on the following criteria:
      obesity, Down syndrome, African American race, severe baseline OSA, and age > 7 yrs. Eligible
      subjects will be recruited from the pediatric otolaryngology clinic at the time of initial
      evaluation for AT. Subjects will undergo a sleep endoscopy under moderate sedation at the
      time of AT. All patients will be asked to complete a preoperative sleep study to confirm the
      diagnosis of OSA and a postoperative sleep study to determine the impact of AT and the
      presence of residual OSA. Secondary outcome measures will include several questionnaires
      assessing generic and OSA-specific quality of life as well as subjective measures of
      cognitive/executive functioning and daytime sleepiness.
    

Detailed description: 
      The purpose of this study is to determine whether sleep endoscopy performed in high-risk
      pediatric patients with obstructive sleep apnea (OSA) at the time of adenotonsillectomy (AT)
      can predict whether the AT will be successful as an initial treatment for OSA. We hypothesize
      that patients with multiple sites of obstruction in addition to adenotonsillar hypertrophy
      (e.g. the nasal airway, velum, base of tongue, supraglottis) will be more likely to have
      residual sleep apnea on postoperative sleep testing.

      Obstructive sleep apnea syndrome OSAS is defined as the symptomatic repetitive obstruction of
      the upper airway during sleep and has been estimated to affect 1-6% of the general pediatric
      population. Untreated OSAS in children has been associated with childhood hypertension,
      autonomic dysfunction, attention deficit/hyperactivity disorder, neurobehavioral impairment,
      and poor quality of life. These sequelae contribute to a 226% increase in health care
      utilization among children with OSAS compared to controls, primarily in the form of increased
      hospitalizations, emergency department visits, and medication use. Adenotonsillar hypertrophy
      is considered the most common risk factor for OSAS in children, therefore unlike in adult
      OSAS, adenotonsillectomy (AT) is the recommended first line treatment. In large part due to
      the increasing awareness and diagnosis of pediatric OSAS, the incidence of AT increased
      dramatically from 1980 to 2005. With more than 500,000 procedures performed per year, AT is
      now the second-most common procedure performed in children in the US, and 77% of these have
      OSAS as the primary indication.

      Current guidelines recommend AT as a first line treatment for pediatric OSAS even for those
      patients who may have significant risk of post-AT OSAS. Estimates of the prevalence of
      persistent OSAS after AT vary widely due to use of different polysomnographic criteria for
      diagnosis. Studies that assessed the risk of post-AT OSAS using a conservative adult
      threshold for diagnosis demonstrated that even with this high threshold at least 13-29% of
      children undergoing AT for pediatric OSAS will have significant residual disease and
      approximately 75% of children will fail to achieve normalization on polysomnography. Specific
      populations of patients that have been recognized to be particularly at risk for post-AT OSAS
      include those with severe baseline OSAS, Down syndrome, obesity, and age > 7 years. In obese
      patients, the prevalence of post-AT OSAS has been reported as high as 73-88%. Since obesity
      has tripled over the last three decades and now affects approximately 8% of children aged 2-5
      years, 18% of children aged 6-11 and 21% of adolescents aged 12-19 years, the problem of
      persistent OSAS after AT is likely to continue to grow.

      Even within populations at risk for AT failure, there is a wide variation in treatment
      response. One study of morbidly obese children undergoing AT demonstrated only a 37% cure
      rate while 53% had sufficient residual OSAS to require further treatment with continuous
      positive airway pressure (CPAP). However, no significant baseline differences were identified
      between surgical responders and non-responders. The mechanism for failure in this population
      is unclear, but it is presumed that increased generalized adiposity leads to multilevel
      obstruction similar to obese adults, thus decreasing the likelihood of success with AT.
      Similarly a poor but still variable response to AT was observed in children with Down
      syndrome with post-AT success varying between 18% and 55% depending on the specific criteria
      used. There are no studies that have clearly identified predictors of AT outcome within the
      Down syndrome population, however, some studies of Down syndrome patients who failed AT have
      suggested that multilevel obstruction is common. Thus, although specific populations of
      patients are known to have greater risk of post-AT OSAS on average, the individual
      characteristics causing persistent disease remain unclear. Accurate prognostication of the
      risk of residual OSA after AT for any individual patient remains a challenge. Studies of
      patients with persistent post-AT OSAS have suggested that multilevel obstruction at locations
      besides the tonsils or adenoids are likely contributors, but this has not been clearly
      demonstrated. In this study, we present a novel concept for building a composite model to
      predict the outcome of AT in children with OSAS. This model will include not just baseline
      features of history and physical exam but also the findings of dynamic sleep-related collapse
      at specific anatomic sites in the pharynx observed during sleep endoscopy. This model will
      give further insight into the mechanisms of airway obstruction as well as the possible
      reasons for persistent OSAS after AT.

      A rating scale for DISE has previously been described in an attempt to standardize the
      reporting of endoscopic findings in adults with OSAS. This rating scale evaluates the degree
      and pattern of obstruction at four levels of the pharynx: the Velum (soft palate), Oropharynx
      (including the tonsils), Tongue base, and Epiglottis (VOTE). The VOTE rating scale has been
      demonstrated to have moderate to substantial inter-rater reliability with kappa values
      ranging from 0.4-0.8 depending on the specific structures being compared. Other investigators
      have utilized modified versions of the VOTE rating scale in children, including other levels
      of the airway such as the nasal airway, nasopharynx, and supraglottis. One recent study
      demonstrated that sleep endoscopy findings in children were more reliable than during awake
      endoscopy and noted a strong correlation between polysomnography results and the overall
      impression of OSA severity during endoscopy.

      Dexmedetomidine, which will be used in this study, is a highly selective α2-adrenoceptor
      agonist that has been demonstrated to result in a sedated sleep similar to natural sleep
      without causing respiratory depression. Though there have been some reports of transient
      bradycardia and blood pressure changes in response to dexmedetomidine infusion (usually
      transient hypotension of 10% with slow infusion) these cardiovascular effects are mitigated
      by co-administration of a bolus of ketamine. These patients would already have been using
      dexmedetomidine or a different anesthesia for their tonsil surgery. The dexmedetomidine is
      not an intervention or part of this study.

      In a preliminary retrospective review of our patient population and surgical volume, we
      examined the electronic medical record of all patients who underwent AT over a 12 month
      period. 498 patients were identified, operated on by the four pediatric otolaryngologists in
      the group. Approximately 200 (40%) of these were performed for OSAS in patients that could be
      considered high risk for residual post-AT OSAS and would meet inclusion/exclusion criteria
      described below.

      Untreated OSA in children has been associated with childhood hypertension, autonomic
      dysfunction, attention-deficit/hyperactivity disorder, poor school performance, and poor
      quality of life. These sequelae contribute to a 226% increase in health care utilization
      among children with OSA compared to controls. Residual OSA after AT in the pediatric
      population remains a serious concern; as the patient grows and changes, their airway
      physiology also changes. Although there is a growing body of research suggesting demographic
      and comorbidity risk factors for post-AT residual OSA, the ability to accurately predict the
      likelihood or severity of residual OSA for any given individual remains elusive. Possible
      tools for the evaluation of post-AT OSA in pediatric populations include radiologic
      examinations, cine MRI scanning, and endoscopic evaluation, along with polysomnography,
      validated questionnaires, and physical examinations. Determining what instruments best
      predict residual OSA after surgical intervention is an important step towards more effective
      OSA management.
    

Intervention name(s): Sleep Endoscopy
Intervention type(s): Procedure
Intervention description(s): Sleep endoscopy will be performed prior to the adenotonsillectomy, under the same general anesthetic. The endoscopy will be performed using a flexible fiber optic endoscope which will be advanced trans nasally into the pharynx down to the level of the hypopharynx. We will take note of any obvious septal deviation or nasal obstruction as well as adenoid hypertrophy, and dynamic collapse at the level of the velum, oropharynx/lateral walls, tongue base, epiglottis, and supraglottis. Relatively fixed structures such as the nasal airway and adenoids should require 1 minute to fully assess. The endoscope will then be held for 2 minutes of observation above each subsequent site of potential dynamic airway collapse (the velum, oropharynx/lateral walls, tongue base, epiglottis/supraglottis).
Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Two recruitment scenarios are anticipated: 1) OHSU Patients who have previously been
        diagnosed with OSAS by polysomnography and are referred to Pediatric Otolaryngology for
        consideration of AT; 2) OHSU Patients referred to Pediatric Otolaryngology for
        consideration of AT for symptoms of sleep disordered breathing without a polysomnographic
        diagnosis of OSAS.
      
Keywords: OSA; sleep apnea; AT; adenotonsillectomy; pediatric