Power equation for all-or-none effects of oxygen toxicity and cumulative oxygen toxicity.

Abstract

Quantification of the level of O2 toxicity may provide a means of setting limits on various hyperoxic exposures. A previously suggested expression for quantitative oxygen toxicity, DMG = a x t2 x PO2c (t-time, DMG-measured level of O2 toxicity), has been adapted for the all-or-none phenomenon: K = t2 x PO2c. A symptom may appear when K reaches a threshold value Kc. Non-linear regression was successfully applied to all-or-none symptoms from the literature: survival, convulsions, substernal distress, reduction in short circuit current and nerve conduction blockade. The generality of these expressions enabled calculation of cumulative oxygen toxicity and a search for the mechanism of oxygen toxicity. Cumulative oxygen toxicity is calculated in three-step calculation loops in three suggested exposure profiles. For a possible recovery period between exposures the expressions took the form: DMGt = DMGc x e-rt, and Kt = Kc x e-rt, where r is the recovery constant. A possibly bimodal distribution of c close to the values of 1 and 4 could be attributed to systemic effects.