Prolonged exposure to hyperoxia has been associated with progressive injury to the alveolar-capillary membrane, leading to increased alveolar and pulmonary vascular permeability, pulmonary edema, atelectasis, and eventual death from hypoxemia,
hypercapnia and/or metabolic acidemia. Several constitutional and environmental factors may also influence tolerance to hyperoxia. Among factors best explored experimentally are metabolic, diet, medications and chemicals, and prior exposure to
hyperoxia
or hypoxia.
Many animal models of increased oxygen tolerance have been investigated, but to date no clinically useful means of reducing oxygen-induced lung injury in human exists. To this point, this study was designed to study the effect of previous
exposure
to
100% oxygen on the pulmonary oxygen toxicity during the following exposure to 100% oxygen.
Eighty female Wistar rats were partitioned into five groups(n=16 for each group) : Gr.Ⅰis control exposed to room air ; Gr.Ⅱbreathed 100% O2 for 2 days and room air for 1 day ; Gr.Ⅲ,Ⅳand Ⅴbreathed 100% O2 for 2 days, room air for 1 day, and
then
each group was exposed to 100% O2 for 1,3 and 5 days respectively.
All groups were partitioned into 2 sub-groups (n=8 for each subgroup) : One sub-group for studing 125Ⅰ-albumin flux ratio, superoxide dismutase(SOD) activity in blood, and lung and body weight ; the other sub-group for studing lung-thorax
compliance,
and analyzing bonchoalveolar lavage(BAL) fluid Only two rats in Gr.Ⅴwere dead. Body weight was significantly lower(p<0.05) in Gr.Ⅴcompared to the other groups. Percent lung weight of total body weight for wet and dry lungs in Gr. ⅣandⅤwere
higher
(p<0.05) than those in Gr.Ⅰ,ⅡandⅢ. In contrast, mean wet lung/dry lung ratio were not changed in each group. Inflation lung-thorax compliances were lower(p<0.05) in Gr.Ⅱ,Ⅲ,ⅣandⅤ, but deflation lung-thorax compliances were not changed.
125Ⅰ-albumin flux ratio was greater(p<0.05) in Gr. ⅣandⅤthan those in Gr.Ⅰ,ⅡandⅢ, Albumin concentrations in BAL was increased in Gr. Ⅱ, Ⅲ, ⅣandⅤand albumin ratio of BAL/plasma was increased in GrⅡ,Ⅲ,ⅣandⅤ. Lactic dehydrogenase(LDH)
was
greater (p<0.05) in Gr. ⅣandⅤ. Alkaline phosphatase was increased (p<0.05) only in group Ⅳ. Dry lung and wet lung weights were increased and body weight were decreased proportionally to the increase in 125Ⅰ-albumin flux ratio.
This study suggested that pre-treatment with 100% oxygen for 2 days and exposure to room air for 1 day increase survival rate and tolerance to pulmonary oxygen toxicity in the following exposure to high concentration of oxygen. The mechanisms of
increased tolerance should be searched in the further biochemical studies, including anti-oxidant enzyme systems.(Korean J Anesthesiol 1995; 29: 633∼647)
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