TY  - CHAP
M1  - Book, Section
TI  - Chapter 39. Anesthesia Delivery System
A1  - Eisenkraft, James B.
A2  - Longnecker, David E.
A2  - Brown, David L.
A2  - Newman, Mark F.
A2  - Zapol, Warren M.
PY  - 2012
T2  - Anesthesiology, 2e
AB  - A  basic  understanding  of  the  anesthesia  delivery  system  and  its  components  is  important  to  the  provision  of  safe  patient  care.The  current  voluntary  consensus  standard  describing  the  features  of  a  contemporary  anesthesia  workstation  is  the  American  Society  for  Testing  and  Materials  (ASTM)  F1850–00,  published  in  2000  and  reapproved  in  2005.The  ASTM  F1850–00  standard  calls  for  an  integrated  and  prioritized  alarm  system,  breathing  pressure  monitoring,  and  exhaled  volume  or  ventilatory  CO2  monitoring.Pin-index  and  DISS  ensure  that  the  correct  medical  gas  enters  the  correct  part  of  the  anesthesia  machine.  The  "fail-safe"  valve  (pressure  sensor  shut-off  valve,  O2  failure  protection  device)  prevents  the  flow  of  nitrous  oxide  (N2O)  or  other  gases  if  the  O2  supply  pressure  is  not  adequate,  but  it  does  not  ensure  O2  flow.  An  O2  analyzer  in  the  patient  circuit  is  essential  to  detect  a  hypoxic  mixture.  It  should  be  automatically  enabled  and  the  low  O2  alarm  set  whenever  the  machine  is  capable  of  delivering  an  anesthetic  gas  mixture.The  O2  and  N2O  flow  controls  are  interlinked  so  that  a  gas  mixture  containing  25%  or  greater  of  O2  is  created  at  the  flowmeters  when  N2O  and  O2  are  in  use.  Use  of  a  third  or  fourth  gas  (eg,  helium)  may  "defeat"  this  feature.A  variable  bypass  anesthesia  vaporizer  creates  a  saturated  vapor  concentration  of  the  anesthetic  and  then  dilutes  it  to  clinically  desirable  concentrations.  Contemporary  vaporizers  for  halothane,  isoflurane,  enflurane,  and  sevoflurane  are  variable-bypass,  concentration-calibrated,  and  temperature-compensated  types.Vaporizers  are  agent  specific.  Erroneous  filling  must  be  avoided;  agent-specific  filling  devices  should  be  used.The  anesthesia  workstation  should  be  checked  each  day  before  anesthetizing  the  first  patient  and  whenever  any  change  has  been  made  to  the  system.  A  shortened  checkout  should  precede  each  administration  of  anesthesia.  The  checkout  procedure  should  follow  the  directions  given  in  the  machine's  operation  and  maintenance  manual.  Because  of  the  diversity  of  the  newer  workstations,  in  2007,  the  American  Society  of  Anesthesiologists  published  guidelines  to  act  as  a  template  for  developing  preanesthesia  checkout  procedures.Use  of  free-standing  vaporizers  downstream  from  the  common  gas  outlet  can  be  hazardous  and  should  be  avoided.  Such  vaporizers  are  often  used  on  pump  oxygenators  for  cardiopulmonary  bypass  procedures.Anesthesia  ventilators  are  traditionally  pneumatic  and  of  "bag-in-a-bottle"  or  "double-circuit"  design.  In  traditional  ventilators,  a  standing  bellows  design,  in  which  the  bellows  descend  on  inspiration  and  ascend  on  expiration,  is  preferred  because  it  makes  a  leak  in  the  breathing  system  more  obvious  (ie,  the  bellows  do  not  refill).  In  Dräger  workstations,  an  electronically  driven  piston  in  a  cylinder  replaces  the  traditional  bellows.In  a  traditional  ventilators,  the  delivered  tidal  volume  (VT)  may  differ  from  the  VT  setting  because  delivered  VT  is  influenced  also  by  the  fresh  gas  flow,  the  inspiratory-to-expiratory  ratio,  the  breathing  circuit  compliance,  and  the  peak  inspiratory  pressure.  Newer  designs  (eg,  GE-Datex  Anesthesia  Delivery  Unit  [ADU],  Aisys,  Smart  Vent,  Dräger  Apollo,  Fabius  GS,  Narkomed  6400)  use  various  approaches  to  ensure  that  VT  is  delivered  as  set  on  the  ventilator  controls.Free-standing  positive  end-expiratory  pressure  (PEEP)  valves  may  be  hazardous  if  added  to  the  circuit  incorrectly.  PEEP  valves  are  safer  when  designed  as  an  ...
SN  - 
PB  - The McGraw-Hill Companies
CY  - New York, NY
Y2  - 2024/04/24
UR  - accessanesthesiology.mhmedical.com/content.aspx?aid=56634957
ER  -