Aspect Medical Systems Announces the Issuance of a Joint Commission 'JCAHO' Sentinel Event Alert Targeted at Preventing and Managing the Impact of Anesthesia Awareness.

NEWTON, Mass. -- Aspect Medical Systems (NASDAQ: ASPM) today announced that the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) has issued a new Sentinel Event Alert (issue no. 32) aimed at preventing and managing the impact of anesthesia awareness. Anesthesia awareness, or intraoperative awareness, occurs when patients do not receive sufficient anesthesia to remain unconscious. Studies show that this experience can be traumatic for patients and result in the development of psychological problems. The JCAHO alert identifies the incidence of awareness, describes common underlying causes and suggests steps for healthcare professionals and institutions to take in order to manage and prevent future occurrences. The alert also recommends that healthcare organizations that perform general anesthesia develop and implement a policy that addresses anesthesia awareness.

The JCAHO alert states that the frequency of awareness ranges between 0.1 percent and 0.2 percent of all patients undergoing general anesthesia, or 20,000 to 40,000 patients per year in the United States. The alert also discusses the emerging role of level-of-consciousness monitoring systems in the prevention of anesthesia awareness, and specifically cites the FDA's determination that "Use of BIS(TM) monitoring to help guide anesthetic administration may be associated with the reduction of the incidence of awareness with recall in adults during general anesthesia and sedation." Citations in the alert include two studies published earlier this year in The Lancet and Acta Anaesthesiologica Scandinavica that demonstrated that consciousness monitoring with Aspect's BIS monitoring system reduced the risk of awareness by approximately 80 percent when compared to standard practice. BIS is the only technology proven to assist clinicians in reducing the incidence of this problem.

"The JCAHO Sentinel Event Alert identifies anesthesia awareness as an important adverse outcome for patients undergoing surgery and recommends that healthcare facilities take action to address this specific concern," said Scott Kelley, M.D., Aspect's medical director and a practicing anesthesiologist. "The published scientific evidence demonstrates that use of BIS technology can help clinicians avoid this complication. Aspect is committed to working in collaboration with our patient monitoring partners to provide healthcare organizations and anesthesia professionals with BIS solutions designed to help address this patient safety issue."

The Joint Commission is the nation's predominant standards-setting and accrediting body in health care and evaluates more than 15,000 health care organizations and programs in the United States. For more information, visit the Joint Commission's Web site at www.jcaho.org.

More information about these studies is available under the following references:

1.  Ekman A, Lindholm ML, Lennmarken C, Sandin R. Reduction in the
        Incidence of Awareness Using BIS Monitoring. Acta
        Anaesthesiologica Scandinavica 2004; 48 (1): 20-6.

    2.  Myles PS, Leslie K, McNeil J, Forbes A, Chan MTV. Bispectral
        Index Monitoring to Prevent Awareness During Anaesthesia: The
        B-Aware Randomised Controlled Trial. The Lancet 2004; 363:
        1757-63.

    3.  Lennmarken C, Sandin R. Neuromonitoring for Awareness During
        Surgery. The Lancet 2004; 363: 1747-8.

    4.  Sneyd JR. Remembering Awareness. British Journal of
        Anaesthesia 2004; 93 (3): 596-7.

About BIS Monitoring

Using a sensor placed on the patient's forehead, Aspect's BIS monitoring system translates information from the electroencephalogram (EEG) into a single number that represents each patient's level of consciousness. This number - the BIS value - ranges from 100 (indicating an awake patient) to zero (indicating the absence of brain activity). Using the BIS value to guide administration of anesthetic medication, in conjunction with other vital signs, allows clinicians to make better informed decisions to achieve optimal anesthesia.

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. The technology has been used to assess more than 9 million patients and has been the subject of approximately 1,500 published articles and abstracts. BIS technology is installed in approximately 33 percent of all domestic operating rooms and is available in more than 160 countries. Aspect Medical Systems has OEM agreements with seven leading manufacturers of patient monitoring systems. For more information, visit Aspect's Web site at http://www.aspectmedical.com.

Safe Harbor Statement

Certain statements in this release are forward-looking and may involve risks and uncertainties. There are a number of important factors that could cause actual results to differ materially from those indicated by these forward-looking statements. These factors include a number of risks facing the Company's business. For example, the Company 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, and also faces competitive and regulatory risks relating to its ability to successfully develop and introduce enhancements and new products. In addition, the Company may not successfully monitor the risk of awareness with BIS monitoring in all cases. 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 additional 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 fiscal quarter ended July 3, 2004, 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.

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.