Aspect Medical Systems Provides Commentary and Information on New England Journal of Medicine Study on Anesthesia Awareness and the Bispectral Index.

-Information for patients, medical professionals posted at www.aspectmedical.com-

NORWOOD, Mass. -- Aspect Medical Systems (NASDAQ: ASPM), the global market leader in brain monitoring technology, commented today on the results from a prospective study of the potential of the Bispectral Index[TM] (BIS[TM]) to reduce the risk of anesthesia awareness. The study, published in the March 13 issue of the New England Journal of Medicine (NEJM), evaluated a patient population considered to be at high risk for anesthesia awareness, or inadvertent waking during surgery. Researchers compared BIS-guided anesthesia care with a protocol based on end-tidal anesthetic gas (ETAG) guided care and found a similar occurrence of awareness in the two groups. The authors concluded that no benefit of BIS monitoring was demonstrated. The results of the BIS-guided care group in the study were consistent with findings from the BIS-guided care group from the B-Aware study published in The Lancet in May 2004. The low incidence measured in the NEJM study represents an 80 percent reduction from the expected rate of awareness in these patients as documented in numerous studies.

"We are pleased that BIS-guided care in the NEJM study again confirms the ability of BIS monitoring to help clinicians achieve a low incidence of awareness in high-risk patient populations," said Scott Kelley, M.D., anesthesiologist and vice president and medical director of Aspect Medical Systems. "Nonetheless, the authors of the NEJM study did not feel that their results support the routine use of BIS monitoring, however, we believe that clinicians need to consider and balance several factors as they interpret the study results."

The most notable difference between the earlier B-Aware study and the NEJM study is the composition of the control groups. While the B-Aware trial investigators compared BIS-guided care with routine standard clinical practice, the authors of the NEJM study compared BIS-guided care with a protocol-based approach to anesthetic administration. In addition, the NEJM study does not include data regarding recovery end-points.

"The ETAG-guided protocol used in the NEJM study instructed the anesthesia professionals to use a certain amount of inhaled anesthetics and audible alarms set at the minimum level. This is not how anesthesia professionals routinely practice," said Dr. Kelley. "We would expect that a protocol which provides significant amounts of volatile anesthesia would produce a low incidence of awareness in these patients."

In practice, anesthesia professionals use clinical judgment, monitoring methods and preferences to select and dose a variety of anesthetic mediations to ensure that their patients are unconscious and free of pain during surgical procedures. A growing number of anesthesia clinicians also use brain monitoring information to help adjust the amount of anesthetic medication during surgery to personalize anesthetic care based on each patient's unique responses.

"We believe that a protocol-based approach providing a certain amount of anesthetic to every patient would reduce the control and flexibility that anesthesia professionals depend upon to provide the best care," said Dr. Kelley. "Anesthesia professionals are responsible for a quick recovery and mitigating post-operative pain as well as managing anesthesia care during surgery. An individualized approach to patient care helps optimize these post-operative outcomes."

The NEJM study adds to the large body of evidence investigating the BIS monitor. A rigorous evidence-based review conducted by the Cochrane Collaboration demonstrates the broad clinical benefits of BIS monitoring. The Cochrane review analyzed 20 randomized controlled trials in which BIS-guided care was compared with standard practice and documented the positive impact of BIS monitoring in reducing anesthetic drug consumption, improving recovery and helping clinicians reduce the risk of awareness. In another meta-analysis of 12 studies, the author estimated that the reduction in drug use and improved recovery reduced the net cost of BIS monitoring to approximately $5.50 per case. "When considering the overall costs for a surgical procedure, this small additional cost to utilize BIS monitoring delivers significant value when considering the safety impact for reducing awareness as well as the choice, flexibility, and information it provides to the anesthesia professional delivering high quality patient care," said Dr. Kelley.

More information about the NEJM trial, including a more detailed comparison with the B-Aware trial can be found at Aspect's Web site at www.aspectmedical.com.

Aspect includes in this press release links to its Web site. Aspect cautions you that the information on its Web site is not incorporated by reference into this press release and should not be considered to be a part of this press release.

About Aspect Medical Systems, Inc.

Aspect Medical Systems, Inc. (NASDAQ: ASPM) is a global market leader in brain monitoring technology. To date, the Company's Bispectral Index (BIS) technology has been used to assess approximately 25 million patients and has been the subject of more than 3,100 published articles and abstracts. BIS technology is installed in approximately 80 percent of hospitals listed in the July 2007 U.S. News and World Report ranking of America's Best Hospitals and in approximately 60 percent of all U.S. operating rooms. In the last twelve months BIS technology was used in approximately 17 percent of all U.S. surgical procedures requiring general anesthesia or deep sedation. BIS technology is available in more than 160 countries. Aspect Medical Systems has OEM agreements with eight leading manufacturers of patient monitoring systems. For more information, please visit the Aspect Medical Systems Web site www.aspectmedical.com.

Safe Harbor Statement

Certain statements in this press release are forward-looking within the meaning of the Private Securities Litigation Reform Act of 1995 and may involve risks and uncertainties, including statements about the potential benefits of the Company's brain monitoring technologies in helping anesthesia providers deliver anesthesia and in reducing the incidence of awareness and statements regarding the use and adoption of BIS monitoring technologies. There are a number of important factors that could cause actual results to differ materially from those indicated by these forward-looking statements. For example, future clinical trials could demonstrate different and/or unfavorable results regarding the potential benefits of the Company's brain monitoring product. The Company may also not be able to achieve widespread market acceptance of its BIS monitoring technology, or to compete with new products or alternative techniques that may be developed by others, including third-party anesthesia monitoring products approved by the FDA. The Company also faces competitive and regulatory risks relating to its ability to successfully develop and introduce enhancements and new products including the BIS VISTA monitor and products based upon its neuroscience technology. Cases of awareness with recall during monitoring with the BIS system and significant product liability claims are among the factors that could limit market acceptance. There are other factors that could cause the Company's actual results to vary from its forward-looking statements, including without limitation those factors described under the heading "Risk Factors" in the Company's Quarterly Report on Form 10-Q for the quarter ended September 29, 2007, which is on file with the SEC.

In addition, the statements in this press release represent the Company's expectations and beliefs as of the date of this press release. The Company anticipates that subsequent events and developments may cause these expectations and beliefs to change. However, while the Company may elect to update these forward-looking statements at some point in the future, it specifically disclaims any obligation to do so. These forward-looking statements should not be relied upon as representing the Company's expectations or beliefs as of any date subsequent to the date of this press release.

Aspect, Bispectral Index and BIS are registered trademarks of Aspect Medical Systems, Inc. All other trademarks, service marks and company names are the property of their respective owners.