Medical Gas Monitors or physiologic graphical recorders designed to simultaneously collect and record several physiologic parameters (e.g., invasive and/or noninvasive blood pressure, heart rate) during surgical procedures when general anesthesia is used. These recorders typically consist of an electronic unit, amplifiers, and sensors appropriate for the parameters to be assessed. Anesthesia physiologic graphical recorders are used for retrospective analysis and/or as evidence of the values and variations of the physiologic parameters during surgical procedures.