Patient Outcomes Can Measure Success of Obstructive Sleep Apnea Surgery

Change in AHI is one measurement that is commonly used to evaluate the success of OSA surgery. The accepted definition of a positive outcome cites a 50 percent reduction in AHI versus pre-operative AHI, achieving an AHI of 20 or less or both, but these criteria do not capture the full burden of OSA (Sleep Med Rev. 2010;14:283-285). According to Edward Weaver, MD, MPH, associate professor in the department of otolaryngology/head and neck surgery at the University of Washington in Seattle, “The commonly used AHI success criteria are arbitrary, and they were not defined by associated improvements in clinical outcomes, including survival, cardiovascular disease, quality of life or symptoms.”

In other words, they do not reflect useful information in the real world of clinical practice. Dr. Weaver explained, “There is no radical difference between a 51 percent and a 49 percent reduction in AHI; yet, according to convention, the first denotes a successful surgery and the second a failure. Similarly, a reduction in AHI from 50 to 25 probably delivers more health benefits than lowering AHI from 6 to 3, but the guidelines equate both of these as successful 50 percent reductions.”

Increased cardiovascular morbidity and mortality is seen more in patients experiencing oxygen desaturation than in those suffering from arousals. The latter group is affected by significant quality of life issues, including fatigue, increased risk of poor job performance and compromised ability to operate a motor vehicle, but the data concerning cardiovascular risk is more robust in the oxygen desaturation population.

Jonathan Hobson, MD, a consultant ENT in Cheshire, England and author of a recent study published in The Laryngoscope, is a strong proponent of using polysomnographic data as a critical part of evaluating surgical success, because the change in AHI represents the improvement in mortality risk (2012;122:1878-1881). “We are fairly certain that mild OSA has few serious long-term health consequences. But we are also fairly certain that moderate to severe OSA is what makes a patient more at risk for hypertension, myocardial infarction and stroke.” When it comes to reducing mortality risk, any reduction in AHI is probably beneficial, because most cardiovascular morbidities are associated with severe OSA. Moving a severe case into the mild or moderate column may reduce the patient’s overall disease burden, said Dr. Hobson.

Therefore, the impact of AHI reduction would be more completly evaluated by taking the starting point into account. A patient with an AHI of 100 who undergoes surgery and has a post-procedure AHI of 51 will most likely enjoy a greater improvement in mortality risk despite failing to achieve generally accepted surgical success. The patient is still at an increased risk for dying, but not as much as before surgery. Conversely, a patient with an AHI of 20 that is reduced by surgery to 10 can claim a successful procedure, even though his actual mortality risk will probably not be measurably improved. Although the change is statistically significant, it is not clinically significant.