Studies Evaluating Use of BIS Monitoring During GI Procedures Presented at Digestive Disease Week.

NEWTON, Mass. -- Researchers are presenting results from studies evaluating the use of BIS(TM) monitoring during routine endoscopy and colonoscopy procedures at the Digestive Disease Week (DDW) meeting taking place this week in Chicago. BIS monitoring, developed by Aspect Medical Systems, Inc. (NASDAQ: ASPM), is the leading level-of-consciousness monitoring technology for measuring the effects of anesthetics and sedatives on the brain.

BIS technology is most commonly used to guide administration of general anesthesia during surgical procedures. The studies being presented at the DDW meeting sought to determine if BIS monitoring would effectively measure consciousness at the lighter levels of sedation frequently administered during gastro-intestinal (GI) procedures such as endoscopies and colonoscopies. Study results indicated that BIS monitoring effectively measured levels of sedation and correlated well with commonly used sedation scales. Clinicians participating in the studies also indicated that BIS monitoring added value to dosing decisions in the majority of cases. Compared to standard clinical practice, however, BIS-guided sedative dosing to an average BIS value of 72 resulted in only a small reduction in patient recovery time and the average administered dose of propofol, a commonly used sedative drug. Independent studies published recently in peer reviewed literature have demonstrated more significant improvements in patient recovery rates when sedatives were administered to maintain a higher BIS target value.

"These study results reflect the overall effectiveness of moderate propofol sedation during GI procedures when administered by experienced practitioners," said Paul Manberg, PhD, vice president of clinical, regulatory and quality assurance for Aspect. "The studies have enabled us to improve our understanding of appropriate BIS ranges for these procedures and will provide clinicians with guidance on how to use our technology to fine-tune dosing of sedatives. Additional studies are necessary to help us better understand the potential role of BIS in addressing other important priorities for healthcare facilities, such as increasing patient comfort, safety and satisfaction in these less-invasive settings."

About BIS Monitoring

Using a sensor placed on the patient's forehead, BIS monitoring 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. To date, the Company's BIS technology has been used to assess more than 11.3 million patients and has been the subject of approximately 1,800 published articles and abstracts. BIS technology is installed in approximately 38 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, including statements concerning the use of BIS monitoring to achieve optimal anesthesia during less invasive procedures and the extent to which additional studies will be useful to establish the value of BIS monitoring in these procedures. 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 may not be able to demonstrate that BIS monitoring can be used effectively during less invasive procedures and the Company may not successfully commercialize its product for this use. There are additional factors that could cause the Company'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 the Company's Quarterly Report on Form 10-Q for the Fiscal Quarter ended April 2, 2005, as filed with the Securities and Exchange Commission. In addition, any forward-looking statements represent the Company's views only as of the date of this press release and should not be relied upon as representing the Company's views as of any subsequent date. While the Company 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 the Company'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.