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anesthesiamachinereview - The Anesthesia Machine 1/16...

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The Anesthesia Machine 1/16 The Anesthesia Machine The Anesthesia Machine I. Physical Properties of Volatile Anesthetic Agents Anesthetic Nitrous Oxide Isoflurane Sevoflurane Desflurane First used clinically 1844 Wells 1969 Stevens et al (1980's) 1981 Holiday (2000's) 1990 Jones et al (mid-1990's) Chemical formula N 2 0 CF 3 CHClOCF 2 H (CF 3 ) 2 CHOCFH 2 CF 3 CFHOCF 2 H Boiling point (ºC) -89.5 48.5 58.5 23.5 Saturated vapor pressure at 20ºC (mmHg) N-50 239.5 157 669.2 Stabilizer None None None None Stability with soda lime Stable Stable Unstable Stable MAC 105% 1.15% 2% 6% B/G partition coefficient (37ºC) 0.47 1.4 0.6 0.42 O/G partition coefficient 1.4 99 50 18.7 II. Compressed Gases A. Medical gases are the most frequently administered drugs in the U.S. (O 2 ) B. Compression of gas is economical and practical for storage C. Gases are expected to be of high purity and administered without flaw D. The medical gases include: oxygen, nitrous oxide, air, CO 2 and nitrogen E. Definition: molecules in a gaseous state that are placed in a cylinder at a high concentration F. *PSIA: pound per square inch absolute i. pressure difference between the measured pressure (in the container) and that at absolute zero G. *PSIG: pounds per square inch gauge i. difference between the measured pressure and atmospheric pressure (at zero) a) 0 psig=14.7 psia (according to gauge) III. Sources A. gas cylinders – attached via the hanger yoke assembly i. The hanger yoke assembly functions to: a) orient and support the cylinder b) provide a gas tight seal c) ensure unidirectional flow of gas B. hospital piping systems C. anesthesia machines contain E-size cylinders IV. Regulating agencies
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The Anesthesia Machine 2/16 A. U.S. Department of Transportation B. Compressed Gas Association C. National Fire Protection Agency D. American Society of Mechanical Engineers E. Contents are classified as a drug and are regulated by the FDA. V. Construction A. Thick steel B. specific to the pressure the tank must withstand C. able to contain 2x their usual working pressure (and not explode) VI. Cylinder size A. Alphabetical, A is smallest, etc. B. E is used on anesthesia machines Cylinder dimensions Nitrous oxide Oxygen E (4.25” o.d. X 26”) 1,590 liters 659 liters H (9.25” o.d. X 51”) 15,899 liters 5,570-7,500 liters VII. Color Coding A. Medical Gases Color Code Gas Formula United States 70º Servive pressure in psig (kPa x100) State in cylinder Oxygen O 2 Green 1900-2200 Gas Carbon dioxide CO 2 Gray - Liquid Nitrous oxide N 2 0 Blue 745 (< 745, < ¼ volume, Δ cylinder) Liquid Cyclopropane C 3 H 6 Orange - Liquid Helium He Brown - Gas Nitrogen N 2 Black - Gas Air - Yellow - Gas VIII. Contents and Pressure A. Non-liquified gas: pressure in cylinder declines proportionately as the contents are withdraw (e.g., oxygen) B. Liquified gas: pressure in the cylinder depends on the vapor pressure of the liquified gas, and is not an indication of the contents if part is in the liquid phase i. The pressure remains constant until all of the liquid has evaporated (e.g. N
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This note was uploaded on 12/03/2009 for the course PSL 431 taught by Professor Stephenson during the Spring '07 term at Michigan State University.

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anesthesiamachinereview - The Anesthesia Machine 1/16...

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