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Minerva Anestesiologica 1999 June;65(6):388-92

Copyright © 2000 EDIZIONI MINERVA MEDICA

language: English

Oxygen toxicity and tolerance

Capellier G. ¹, Maupoil V. ², Boussat S. ¹, Laurent E. ¹, Neidhardt A. ¹

¹ Faculté de Médecine et de Pharmacie - Besançon, Réanimation Médicale; ² Faculté de Médecine et de Pharmacie - Besançon, Physiologie, Pharmacologie et Nutrition Préventive Expérimentale

Normobaric oxy­gen tox­ic­ity is ­well ­described in all ani­mal spe­cies. However sus­cep­ti­bil­ity to oxy­gen expo­sure is high­ly var­i­able accord­ing to age, spe­cies and ­strains. Similarly in ­humans, pro­longed ­high oxy­gen expo­sure is report­ed to ­induce ­cough, short­ness of ­breath, ­decrease ­vital capac­ity and ­increase alveo­lo-cap­il­lary perme­abil­ity. The tox­ic FIO2 thresh­old (­length of expo­sure and lev­el) is ­still debat­ed. In ­patients ­with pre­vi­ous ­lung inju­ry, ­this thresh­old is ­even ­more dif­fi­cult to delin­eate as path­o­log­ic pul­mo­nary ­lesions ­might ­result ­from hyper­ox­ia or pri­mary ­lung ­insult. Oxygen ­free-rad­i­cals ­play a key ­role in the pathoph­y­sio­lo­gy of oxy­gen tox­ic­ity.
Oxygen resis­tance or tol­er­ance is ­obtained ­with intra­per­it­o­neal, intra­ve­nous and intra­tra­cheal endo­tox­in or cyto­kines admin­is­tra­tion. Pre-­vious expo­sure to ­high oxy­gen con­cen­tra­tion is ­also report­ed to ­increase sur­vi­val ­rate and ­decrease pul­mo­nary ­lesions in ani­mal mod­els. Protection may ­rely on anti­ox­i­dant ­enzymes syn­the­sis, ­nitric ­oxide pro­duc­tion, neu­troph­ils recruit­ment and mod­ula­tion of alveo­lar mac­ro­phag­es activ­ity.
In ­humans, oxy­gen tol­er­ance ­might be sus­pect­ed ­through sev­er­al clin­i­cal stud­ies report­ing favor­able out­come ­after ­long ­term-oxy­gen expo­sure. Better knowl­edge of the ­risks of pro­longed ­high oxy­gen expo­sure is impor­tant to re-eval­u­ate the ­goals of mechan­i­cal ven­ti­la­tion (FIO2, SaO2, ­PEEP) and/or to devel­op treat­ments to pre­vent oxy­gen tox­ic­ity (sur­fac­tant, anti­ox­i­dant ­enzymes).