Virtual Surgery in the Upper Airways – New Solutions to Obstructive Sleep Apnea Treatment

Sleep apnea is caused by the soft parts of the upper airways collapsing and preventing the air from flowing freely during sleep. Obstructive sleep apnea (OSA), affects up to 20 percent of the population. The disease is recognized by heavy snoring, frequent breathing stops, gasping for breath, and repeated awakenings. OSA is the cause for low quality sleep and reduced oxygen uptake and is considered a major cause for reduced life quality, cardiovascular disease, diabetes, and increased mortality in the modern society. There is a variety of available treatment options for OSA. One effective aid is obtained by use of a mask during sleep that provides air with an overpressure (CPAP). Many people have difficulties to comply with this mask due to discomfort, and stop using it. There are several surgical procedures than can be used, but experience shows that the results rarely gets better, and often is unchanged or even worse. Today there are no available methods for predicting the outcome of the treatment. Medical imaging can be used to produce pictures of the patients' airways. These lay a good foundation for studying and describing the shape and size of the airways, but they tell little about the way the airflow will distribute in the airway or how the soft tissue in e.g. the soft palate, tongue or pharynx will be affected by the airflow. In this project patient specific CT-images of upper airways were utilized to build computer models. These models were used to compute how the airflow and soft tissue behave. By virtual surgery, we modified the patient-specific computer model according to the surgical technique followed by computations to find out how treatment may affect the patient in real life. The simulations clearly showed which procedures that were more effective than others. This can be used as a part of the medical doctor's basis for selection of treatment options combined with experience and interpretation of available information about the patient. This project is conducted through the collaboration between medical experts from St. Olavs hospital, the university hospital of Trondheim, and the Faculty of medicine at NTNU and experts in computational biomechanics at the Faculty of engineering at NTNU and SINTEF. The results from the project provides a good basis to develop a commercial "design tool" that can be used in treatment planning. Such a tool has the potential to help reduce the waiting lists and costs in the health sector as well as reducing risk and inconvenience for patients.

En hovedambisjon i prosjektet var å vise hvordan man kan bruke numeriske simuleringer av pasientspesifikke anatomier til å virtuelt studere virkningen av kirurgiske teknikker som skal redusere obstruktivt søvnapne problemet. Dette har prosjektet vist ved bruk at flere eksempler hvor pasienters anatomi i øvre luftveier er bestemt ved ct bilder. Disse er overført til datamodeller som egner seg for biomekaniske simuleringer. Pasientene har en oppgitt OSA diagnose med tilhørende alvorlighetsgrad (AHI indeks). Vi har simulert hvordan øvre luftveier deformeres uten noen kirugiske intervensjoner, og simulering med flere forskjellige alternative intervensjoner. Her er undersøkt fjerning av ganevev, implantering av stivere i myke gane og/eller bakre del av tunge, og fremflytting av underkjeven som det mest drastiske grepet. Forskjellig grad av forbedring av åpning av øvre luftveier er påvist avhengig av hvilken kirurgi som benyttes. Noen teknikker gir moderat forbedring av OSA, og fremflytting av nedre kjeve gir den desidert største forbedringen. Som proof-of concept er dette et solid grunnlag for å vurdere kombinasjonen av medisinsk avbildning, datamodellering, simulering av virtuell kirurgi i klinisk praksis.

Obstructive sleep apnea (OSA) is a sleep related breathing disorder caused by repetitive collapses of the upper airways during sleep, resulting in reduced breathing, oxygen desaturation and sleep disturbances. It is well documented that OSA has a massive impact on global health [1-4], with approximately 20% of the adult population affected. OSA endpoints are cardiovascular diseases including hypertension, stroke and ischemic heart disease. OSA is also linked to insulin resistance and the development of diabetes and metabolic syndrome. Surgical treatment is frequently been performed, but long-term outcomes are still uncertain. The current project will combine research from engineering science and medicine for patient-specific diagnostics and treatment of Obstructive Sleep Apnea (OSA). When evaluating treatment options, clinicians are currently relying on general guidelines and personal experience, but they are lacking objective and predictive decision support tools. This project will provide required insight and software tools for computer-aided diagnostics and treatment of OSA through the promotion of virtual surgery. Thereby, OSA patients can be treated more targeted, with reduced risk for the patient and reduced cost for society.