Use of High-resolution Manometry to Detect Upper Airway Obstruction During Sleep

Obstructive sleep apnea (OSA) is a major public health issue in both children and adults, present in 1-5% of children and 10-30% of adults. It is characterized by repeated episodes of airway obstruction during sleep, leading to brain arousal, sympathetic activation, oxygen desaturation, sleep fragmentation, and non-restorative sleep. Patients report daytime tiredness, insomnia, and morning headaches. Children with OSA experience daytime somnolence, difficulties at school, behavioral problems, enuresis, and reduced quality of life. If left untreated, OSA can lead to numerous complications including hypertension, cardiovascular disease, stroke, and insulin resistance. Sleep partners are also affected, with patients viewing their disorder as a burden and sleeping in separate rooms. Further, disease prevalence is increasing as obesity increases. Continuous positive airway pressure (CPAP) is the current gold standard treatment for OSA. If used effectively and consistently, it can improve patient symptoms. However, adherence is generally poor, with patients experiencing physical discomfort, chest discomfort, and dry mouth. For those patients that cannot tolerate CPAP, surgical intervention is an option. In children, this typically starts with adenotonsillectomy. However, 20-75% of children will have persistent symptoms after adenotonsillectomy. In adults, anatomic factors including tonsil hypertrophy and redundant pharyngeal tissue can contribute to upper airway obstruction and may also necessitate higher pressures for effective CPAP treatment. Even if surgical intervention does not cure the OSA, it may make CPAP more tolerable and improve CPAP adherence. Sleep-related airway obstruction is a complex phenomenon potentially involving multiple anatomic levels. For patients with persistent symptoms despite initial therapy or intolerance to CPAP, further evaluation of the upper airway is clinically valuable. Polysomnography (PSG) is the gold standard for diagnosing OSA, but it does not provide information on the location(s) of upper airway obstruction. Knowledge of the precise sites of obstruction is critical to planning effective sleep surgery. Currently, this is accomplished with drug-induced sleep endoscopy (DISE). DISE was originally proposed in 1991 and involves administering anesthetic to a patient to simulate a sleep state, and then visualizing the upper airway using transnasal flexible endoscopy. Sites of obstruction at key locations including the adenoids, soft palate, lateral oropharynx, tongue base, and epiglottis can be identified. Though DISE offers valuable clinical information, it has notable limitations. First, it cannot evaluate the entire upper airway simultaneously, as any obstruction occurring superiorly precludes visualization of any obstruction occurring more inferiorly. Second, interpretation of DISE is subjective and there is no universally accepted system for analysis. Rating systems are qualitative, using grades such as complete, partial, or no obstruction as opposed to quantitative measurements. The optimal sleep assessment would be quantitative, reliable, and provide information on the entire upper airway simultaneously. A potential alternative to DISE which could meet these criteria is sleep manometry. Measurement of upper airway pressures captures the effects of obstruction along the entire upper airway, from the nasopharynx to larynx. Prior studies have attempted to employ manometry, but have been limited primarily by inadequate equipment and suboptimal methods of data analysis. Woodson et al. used a solid-state manometer with diameter of 2.3 mm and 5 sensors to detect palatal obstruction and tongue base obstruction in patients with OSA. They also used the same approach to detect persistent tongue base obstruction following uvulopalatopharyngoplasty. While these studies help demonstrate that manometry can be a useful adjunct to OSA assessment, they are severely limited both by the type of manometer used as well as the lack of a clear, detailed description of the method of data analysis. High-resolution manometry (HRM) uses pressure censors spaced 1 cm apart to allow for pressure measurement along the entire upper airway. The investigators have previously applied HRM to assessment of swallow physiology. Sophisticated methods of automated data analysis have been developed that have been shown to be reliable for both expert and novice users . Further, pattern recognition techniques have been applied to identify dysphagia and specific swallowing abnormalities. Application of this technology and modification of existing data analysis platforms will allow for a quantitative, reliable, and comprehensive assessment of upper airway obstruction during sleep in both children and adults, with potential for development of algorithms to predict effects of targeted surgical therapy at all levels of the upper airway.