Aspect Announces Availability of Key Results of Studies Featuring BIS Monitoring.

Business Editors

NEWTON, Mass.--(BUSINESS WIRE)--July 29, 2003

Awareness and Mortality Research Posted on Anesthesiology Web Site

Aspect Medical Systems, Inc. (NASDAQ: ASPM) today announced that new results from four intraoperative awareness and mortality clinical studies are available on the Anesthesiology web site and will be presented at the American Society of Anesthesiologists (ASA) meeting in San Francisco, October 11-15, 2003. The studies were designed to investigate the incidence of awareness and the impact of utilization of BIS(R) technology on awareness and mortality rates. Aspect provided partial funding to support these studies.

Intraoperative awareness occurs when patients unintentionally regain consciousness during surgery. Studies conducted outside the U.S. have reported that awareness occurs in one to two patient cases per thousand, but until now, the incidence of awareness in the U.S. was unknown. The AIM (Awareness Incidence and Monitoring) trial was designed to determine the incidence of awareness in the U. S. This multi-center study assessed the incidence of awareness in seven U.S. hospitals based on interviews with 19,576 patients conducted immediately after surgery and one week following surgery. Data from the AIM trial will be presented by Dr. Peter S. Sebel from Emory University School of Medicine, in Atlanta, GA on Wednesday, October 15 at the ASA meeting (abstract # 360). A second trial, referred to as the B-Aware study, sought to assess the impact of BIS-guided anesthesia on the incidence of awareness. Data from this prospective, randomized, double-blind, multi-center study of 2,500 patients at high risk for awareness will be presented by Dr. Paul S. Myles from Alfred Hospital and Monash University in Melbourne, Australia, on Monday, October 13 at the ASA meeting (abstract # 320).

The results from these new awareness studies complement earlier research presented at the International Anesthesia Research Society Meeting in March 2003 that prospectively studied more than 5,000 BIS monitored patients at two Swedish hospitals. The incidence of awareness with BIS monitoring at these hospitals was compared to the incidence previously reported in a study of 7,811 patients from the same two hospitals prior to the introduction of BIS technology. This prospective study demonstrated a statistically significant 78% reduction in cases of awareness observed when BIS monitoring was used.

Aspect has filed a 510(k) application with the U.S. Food and Drug Administration to revise product indications for use to reflect results from these awareness trials.

Data have also been posted on the Anesthesiology web site from two studies exploring the relationship between BIS monitoring and postoperative mortality rates. The first study, to be presented by Dr. Claes Lennmarken from University Hospital in Linkoping, Sweden, examined intraoperative BIS levels and postoperative mortality rates for 4,090 patients within one year following surgery. Data from this study will be presented on Tuesday, October 14 at the ASA meeting (abstract # 303). The second study, which Aspect conducted in collaboration with researchers from the University of Florida, examined Medicare inpatient claims and mortality data to determine the relationship between the level of institutional use of BIS monitoring and the rate of risk-adjusted postoperative mortality. Results from this study will be presented by Dr. Terri Monk from the University of Florida in Gainesville, on Wednesday, October 15 at the ASA meeting (abstract # 1361).

To access summary results from the four new studies, please visit the Anesthesiology web site (www.anesthesiology.org), select the link for "ASA abstracts" and conduct a keyword search using the "search abstracts" tool.

"We are optimistic that these studies will provide persuasive additional evidence of the clinical benefits of BIS monitoring. Nonetheless, medical practice remains conservative about responding to such studies until they have been published in major peer-reviewed journals," said Nassib Chamoun, president and CEO of Aspect. "We believe that the presentation of these findings at this year's annual ASA meeting in October and the publication of these studies will further support the value of BIS technology in clinical practice."

About Aspect Medical Systems, Inc.

Aspect Medical Systems, Inc. (NASDAQ: ASPM) is a global market leader in brain monitoring technology. Aspect's BIS technology directly measures the effects of anesthetics and sedatives on the brain and has been used to assess more than 7 million patients. BIS is currently in use in the operating rooms and intensive care units of more than 55 percent of the best-ranked hospitals in the U.S. (based on a U.S. News & World Report ranking) and has been the subject of approximately 1,250 published articles and abstracts. BIS is available in more than 160 countries with a worldwide installed base of monitors and BIS modules of approximately 17,800. Aspect has secured OEM agreements with seven leading manufacturers of patient monitoring systems. Based in Newton, Mass., Aspect employs more than 200 people worldwide. For more information, visit Aspect's web site at www.aspectmedical.com.

Although Aspect has referred you to the Anesthesiology web site in this press release, Aspect does not control or maintain such web site. Therefore, Aspect assumes no responsibility for information or statements on the Anesthesiology web site.

Safe Harbor Statement

Certain statements in this release are forward-looking and may involve risks and uncertainties, including Aspect's expectations with respect to further acceptance of the anesthesia community of BIS technology as a result of these trial results, the ability to grow the market for its products worldwide and build value for its shareholders. There are a number of factors that could cause actual results to differ materially from those indicated by these forward-looking statements. For example, Aspect may not be able to achieve widespread market acceptance of its BIS monitoring technology, receive FDA approval of claims with respect to awareness, or be able to compete with new products or alternative techniques that may be developed by others including third-party anesthesia monitoring products approved by the FDA. Aspect also faces competitive and regulatory risks relating to its ability to successfully develop and introduce enhancements and new products. In addition, the Company has limited sales and marketing experience both in the U.S. and internationally and if it is unable to develop and implement a successful sales and marketing strategy, including with respect to its own sales force, domestic and international distributors, original equipment manufacturers and other direct and indirect sales channels, it will not be able to generate meaningful product revenue. Aspect's ability to become and remain profitable will depend upon its ability to promote frequent use of the BIS system so that sales of its BIS sensors increase. Aspect will not be profitable if hospitals and anesthesia providers do not buy and use its BIS systems in sufficient quantities. Cases of surgical awareness 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 Aspect's actual results to vary from its forward-looking statements, including without limitation those set forth under the heading "Factors Affecting Future Operating Results" in Aspect's -Quarterly Report on Form 10-Q for the quarter ended March 29, 2003, as filed with the Securities and Exchange Commission. In addition, any forward-looking statements represent Aspect's views only as of the date of this press release and should not be relied upon as representing Aspect's views as of any subsequent date. While Aspect may elect to update forward-looking statements in the future, it specifically disclaims any obligation to do so, even if its expectations change. Therefore, you should not rely on these forward-looking statements as representing Aspect's views as of any date subsequent to the date of this press release.

Bispectral Index and BIS are registered trademarks of Aspect Medical Systems, Inc. A-2000 is a trademark of Aspect Medical Systems, Inc. All other trademarks, service marks and company names are the property of their respective owners.