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A Journal on Anesthesiology, Resuscitation, Analgesia and Intensive Care

Official Journal of the Italian Society of Anesthesiology, Analgesia, Resuscitation and Intensive Care
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SUPPORT VENTILATION  SMART 2002 Milan, May 29-31, 2002

Minerva Anestesiologica 2002 May;68(5):332-6

language: English

Airway closure, atelectasis and gas exchange during anaesthesia

Hedenstierna G.

From the Department of Clinical Physiology University Hospital, Uppsala, Sweden


Pul­mo­nary gas ­exchange is reg­u­lar­ly ­impaired dur­ing gen­er­al anaesthe­sia ­with mechan­i­cal ven­ti­la­tion. ­This ­results in ­decreased oxy­gen­a­tion of ­blood. ­Major caus­es are col­lapse of ­lung tis­sue (ate­lec­ta­sis) and air­way clo­sure. Col­lapsed ­lung tis­sue is ­present in 90% of all sub­jects, ­both dur­ing spon­ta­ne­ous breath­ing and ­after mus­cle par­al­y­sis, and wheth­er intra­ve­nous or inha­la­tion­al anaesthet­ics are ­used. Air­way clo­sure is ­also com­mon and increas­es in mag­ni­tude ­with increas­ing age of the ­patient. ­There are cor­re­la­tion ­between the ­amount of ate­lec­ta­sis and pul­mo­nary ­shunt and ­between air­way clo­sure and per­fu­sion of poor­ly ven­ti­lat­ed ­lung ­regions (low VA/Q). Ate­lec­ta­sis and air­way clo­sure ­explain as ­much as 74% of gas ­exchange impair­ment in rou­tine anaesthe­sia. A ­major ­cause of ate­lec­ta­sis is the pre-oxy­gen­a­tion dur­ing induc­tion of anaesthe­sia. Low­er­ing the ­inspired O2 con­cen­tra­tion to 80% suf­fic­es to ­avoid ­almost all ate­lec­ta­sis. Air­way clo­sure and low VA/Q can ­only be pre­vent­ed by rais­ing the FRC lev­el by ­PEEP or by oth­er ­means.

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