Given that only minimal blood was required to perform this study, a waiver of consent was granted from our review board. When an ABG was deemed to be necessary as part of ICU management, a central venous sample was also obtained within 2 minutes. All of the samples were analyzed using the same Bayer Rapid Point 405 blood gas analyzer as quickly as possible. A maximum of 10 paired ABG-VBG samples were obtained per patient to prevent a single patient from dominating the data set. Additional data collected on a standardized data collection form included primary diagnosis, intubation status, use of inotropic agents, and hypotension (defined as a systolic BP _90 mmHg). Data comparing central and peripheral VBG values were also obtained. Paired central and peripheral venous samples were drawn within 2 minutes of one another in ICU patients with both central venous lines and peripheral
intravenous lines already in place.