PURPOSE: Obstructive sleep apnea (OSA) is comprised of dynamic airway events that occur during natural sleep. Current airway measures are static (cephalometry) or involve invasive techniques which interfere with natural sleep (sleep endoscopy). We propose that real-time magnetic resonance imaging (RT-MRI) with simultaneous non-invasive physiologic measures of sleep can elucidate site of obstruction.
METHODS: A prospective series of 7 OSA subjects diagnosed by attended polysomnography, Fujita classification, Functional Outcomes of Sleep Questionnaire (FOSQ) and Epworth Sleepiness Score (ESS) underwent continuous RT-MRI during a 90 minute nap without sedation utilizing actigraphy. The upper airway at the mid-saggittal plane was visualized in real time (33 frames per second) using a sliding window algorithm (RTHawk system). Respiratory events, pulse arterial tone amplitude (zzzPAT algorithm), oxygen saturation, and pulse rate were simultaneously monitored (Watch-PAT, Itamar Inc, Israel).
RESULTS: OSA subjects displayed a mean BMI of 27 and the apnea-hypopnea index was 48.3 events per hour with a Fujita class that varied from palate only (type I) to palate and tongue obstruction (type II). The mean FOSQ and ESS scores were 3.18 and 9.1, respectively. Airway obstructions visualized on the RT-MRI during sleep included palate only, tongue only, combined upper airway narrowing and obstruction, and epiglottis obstruction and were predictive of the Fujita class. Respiratory events during sleep (mean rate of 27.1/hr/subject) and desaturations (mean rate of 14.7/hr/subject) coincided with the obstructive events observed during the RT-MRI. Respiratory events were associated with PAT signal attenuation, PAT amplitude reduction, pulse rate acceleration, and desaturation events. The specific location of airway obstruction was characterized with a high degree of precision.
CONCLUSION: Our study shows a novel approach to simultaneously evaluate airway obstructions with respiratory and desaturation events in real time during natural sleep.
CLINICAL IMPLICATIONS: By simultaneously observing site of obstruction dynamically as detailed by RT-MRI and quantifying respiratory events, this approach can target the actual site of obstruction preoperatively and has the potential of improving predictions of successful surgical outcome in patients with OSA.
DISCLOSURE: Jose Barrera, No Financial Disclosure Information; No Product/Research Disclosure Information