by John E. Remmers, M.D.
Even though they are preferred by patients with obstructive sleep apnea (OSA) and such patients use them faithfully, mandibular protruding dental appliances (MPDA) are prescribed for OSA only in a small minority of cases. Only 5% of all treated OSA patients receive oral appliance therapy (OAT). That’s right, the rest are treated with continuous positive airway pressure (CPAP).
“Ahah!” you say, “that’s proof that MDs are getting some sort of financial kickback, otherwise why would they consistently prescribe a therapy that patients hate and only rarely use?” Sorry, only a minority of sleep physicians have a financial incentive to prescribe CPAP. This is not a sufficient explanation.
“Obviously”, you say, “this strong bias toward CPAP reflects the physician’s comfort with a treatment that uses air pressure and airflow, most sleep physicians being pulmonologists. Look, CPAP was invented by a pulmonologist!”. Closer to the truth, perhaps; certainly most MDs, whatever their speciality, do not cater to having their hands in the gooey, slimy oral cavity, even with gloves on. But, a gut-level preference for one genre of treatment over another cannot account for the vast disparity in treatment of OSA.
OK, let’s have the truth. I believe the reason sleep physicians shun OAT is clearly stated in the recent consensus review commissioned by the ORANGE- registry. A group of international experts reviewed the evidence regarding efficacy of OAT in treating OSA and concluded that “complete response occurs in around 48% of patients”. Now, here’s a reason not to prescribe OAT, particularly when you realize that CPAP produces a complete response in around 100% of patients. Why would a sleep physician choose a therapy that has marginal efficacy when a completely efficacious option, CPAP, is available? She/he wouldn’t.
Make no mistake about it; this is where the rubber meets the road. The prescribing physician will not be persuaded by counter-arguments, such as, “your patient prefers using an oral appliance” or “your patient will not consistently use CPAP.” No, the physician wants first and foremost to prescribe an efficacious therapy. She/he will worry later, if at all, about adherence to the prescribed therapy.
This is not an unreasonable stance; you cannot change the intrinsic efficacy of a drug or a medical device. The physician might be able to influence CPAP compliance somewhat by interacting with the patient or selecting a more suitable interface, but she/he cannot make a MPDA more efficacious. In other words, if the device leaves the patient with an apnea-hypopnea index (AHI) that is elevated, no amount of interacting with the patient will bring it into a normal range.
But all is not lost. We can increase the overall efficacy rate for OAT since half of all OSA patients experience a completely adequate therapeutic response. Perhaps, we could treat only those who respond fully to OAT if we could identify them in advance, i.e., we could achieve a very high efficacy rate if we could select for OAT those patients who will experience a therapeutically satisfactory response. This approach has been taken by a number of investigators, and the search for methods for patient selection for OAT has become a search for the Holy Grail of our field.
The Holy Grail has proved elusive, however. Clinical features such as AHI and BMI have not been found to accurately predict whether or not an individual patient will experience a satisfactory therapeutic response. Similarly, imaging the pharyngeal airway or quantitative evaluation of bony features or soft tissue of the head and neck have not been shown to be predictive of therapeutic outcome. While much research remains to be carried out with these methods, the results to date have been disappointing.
Over the past decade we have taken a more direct approach. Rather than searching for some feature or characteristic of a patient that would predict therapeutic outcome, we have moved closer to the phenomena we are trying to predict. Specifically, we have developed a polysmnographic test that examines a patient’s breathing while using an adjustable MPDA. This allows us to evaluate the response of the patient’s sleep apnea to precisely the therapeutic intervention of interest, mandibular protrusion. The test uses a temporary appliance so that if mandibular protrusion is found to eliminate sleep apnea, a custom-fitted MPDA can be fabricated and set to a target mandibular position found to be efficacious.
We have carried out three prospective clinical trials using such a test, and all have shown that the approach has promise. The most recent was performed on 67 patients using the commercially available system, MATRx (Zephyr Sleep Technologies). The results revealed that the test has high predictive accuracy for identifying favorable candidates for OAT. Specifically, all patients predicted to experience therapeutic success with a custom-fitted MPDA (Somnodent) had an AHI value less than 10 hr. Thus, we now have a highly accurate method for selecting apneics for OAT, and for these individuals the efficaciousness rate approaches 100%. And what about the target protrusive position, was it efficacious? Yes, in 87% of cases the mandibular protrusion that was efficacious in the MTRx titration study was sufficient to yield a successful therapeutic response.
What are the implications for managing sleep apnea? For the first time, we now have an alternative to CPAP, a therapy with similar efficacy and, likely, higher compliance. For patients who prefer OAT, we have a therapeutic option that is certainly as good as CPAP, probably better. And, this appears to open a new chapter in dental sleep medicine, one where use of OAT for OSA will increase from 5% to a much higher value.
But, rest assured that this will happen ONLY if OAT is 100% efficacious; sleep physicians will continue to ignore OAT until they adopt the MATRx system.