February 2011

Winter Bulletin Online Now
The Winter edition of our Section Bulletin is online now, with great articles on a CPAP/Bi-Level desensitization clinic, substance abuse and sleep disorders, and the value of a good mattress. Section Chair Tony Stigall provides an update on section activities as well, and we have a profile of our 2010 Specialty Practitioner of the Year.

Measure AHI, Not Compliance
Swedish researchers who used mathematical function formulas to gauge the effect of various OSA treatment modalities on the apnea hypopnea index (AHI) find arbitrary compliance rates often cited as harbingers of success with CPAP may hide insufficient reductions in AHI with the therapy. Specifically, patients with moderate OSA who use CPAP for four hours a night reduce their AHI by 33.3% to 48.3% (AHI 0-5, respectively). However, when the AHI target is reduced to <5, CPAP must be used 66.67% to 83.33% per night (AHI of 0 while using the therapy). “Using a mean AHI in CPAP therapy is more realistic than using arbitrary compliance rates,” conclude the authors. The study appeared in the Jan. 1 issue of Sleep. READ ABSTRACT

CPAP Reduces Arterial Stiffness
A new study out of Germany is clearing up some of the debate surrounding the relationship between OSA and atherosclerosis. Researchers followed 172 patients with suspected OSA who were treated with CPAP, measuring vascular function to see how OSA affected the condition and whether CPAP would improve it. Forty-five pairs of patients with and without OSA were matched for gender, age, and hypertension and served as controls. Results showed:

• OSA was associated with increased augmentation index (Aix) and pulse wave velocity (PWV) in patients when compared with controls without OSA.
• Multivariable analysis and results from the nested case-control cohort showed that OSA was associated with increased Aix and PWV independently from hypertension, age, gender, body mass index, and antihypertensive medications.
• In 49 effectively-treated OSA patients, Aix and PWV improved from baseline, while ineffectively-treated OSA patients showed no change in Aix or PWV.

The authors conclude, “These findings extend our understanding of the recently shown cardiovascular burden in OSA and help to explain why CPAP treatment proved to ameliorate cardiovascular outcome even in patients without preexisting cardiovascular disease.” The research was published in the Jan. 7 Epub edition of Sleep & Breathing. READ ABSTRACT

EERS Improves Outcomes for CPAP-Refractory Patients
Could at least some CPAP failures be reclaimed with the addition of low volumes of dead space (enhanced expiratory rebreathing space, or EERS) to minimize sleep hypocapnia? Yes, report researchers from Beth Israel Deaconess Medical Center who reviewed the charts of 204 patients diagnosed with CPAP-refractory sleep apnea over a two year period. The addition of 100-150 mL EERS via a non-vented mask significantly improved polysomnographic control of sleep apnea without inducing tachypnea or tachycardia. Improved clinical tolerance and compliance, and sustained clinical improvement, were noted on follow up as well, although leak and sleep fragmentation modified clinical outcomes. The study was published in the December issue of the Journal of Clinical Sleep Medicine. READ ABSTRACT

Identifying OSA in Commercial Drivers
Using objectively measurable risk factors might be better than inquiring about symptoms when assessing truck drivers for OSA, report New York and Tennessee researchers publishing in the Jan. 25 Epub edition of the Journal of Occupational and Environmental Medicine. They used Joint Task Force guidelines to screen 1890 commercial motor vehicle drivers, finding 51 cases of polysomnography-confirmed OSA. That translated to estimated positive predictive values of 78.5% for the screening criteria. Multivariable logistic regression, however, independently associated body mass index ≥30, hypertension, and diabetes with OSA. “Medical examiners’ use of objectively measurable risk factors, such as obesity, history of hypertension, and/or diabetes, rather than symptoms, may be more effective in identifying undiagnosed OSA in commercial drivers during the commercial driver medical examinations,” conclude the investigators. READ ABSTRACT