Original article
Oxygen toxicity: simultaneous measure of pentane and malondialdehyde in humans exposed to hyperoxia

https://doi.org/10.1016/S0753-3322(01)00042-7Get rights and content

Abstract

In order to estimate cell damage caused by free radicals during oxygenotherapy, we investigated the time course of two markers of lipoperoxidation: pentane in breath and malondialdehyde (MDA) in blood during brief normobaric hyperoxia. Nine healthy subjects inhaled hydrocarbon-free air (HCFA) for 30 minutes, hydrocarbon-free 100% O2 (HCFO2) for 125 minutes and then HCFA for 70 minutes.

After 15 minutes of washout with HCFA, ambient pentane was eliminated. After HCFO2, at T175 versus T30 (i.e., 145 min from the start of 100% HCFO2), pentane production increased (P < 0.05). MDA rose significantly at T155 min (i.e., 125 min from the start of HCFO2), versus T30 (P < 0.01).

These results suggest that acute hyperoxia causes a moderate increase in lipid peroxidation in healthy subjects. The increase of pentane and MDA confirms that acute hyperoxia induces lipid peroxidation in healthy subjects.

Section snippets

Subjects

Nine healthy, nonsmoking volunteers were included: seven women and two men, with an age range from 48 to 65 years (mean 52.6 ± 6), and body weight range from 50 to 77 kg (mean 60.1 ± 7.3). They fasted for at least 8 hours before the experiment, which was performed between 8 A.M. and 12 A.M. Their consent was obtained and the protocol was approved by the local ethics committee.

Material

The experimental system was as follows: the subject was connected to a pneumotachograph (Godart-Statham, Holland) and a

Assessment of measurement quality

It is known that under some experimental conditions, isoprene and isopentane coelute with pentane 13, 17. With the Al2O3/KCl plot column, pentane appeared clearly separated from isopentane and isoprene with retention times of 28, 26,5 and 41 minutes respectively (figure 1A, B). Intra- and interassay coefficients of variation of standard pentane were 5% and 8% respectively. We obtained 90% recovery when a concentration of pentane standard was added to a known concentation of sample expired gas.

Discussion

Several markers have been proposed for detecting lipid peroxidation. MDA is known to have low specificity and produce artefacts when applied to body fluid. The thiobarbituric test reacts with other components such as glucose, bilirubin and hemoglobin; but none of our subjects had an abnormal concentration of these. One criticism has been that MDA can be further metabolized in vivo and some of its reaction products may interfere with the MDA-TBA reaction. However, in their hyperoxic rats,

Conclusion

The reliability of the pentane data depends chiefly on the quality of the washout, the method of expired gas concentration and the choice of column. Measurement of n-pentane in vivo could underestimate lipid peroxidation due perhaps to a rapid metabolism (or storage in the body), in contrast to MDA, which is metabolized more slowly. In this study, the analysis of pentane and MDA in healthy humans exposed to high oxygen concentration confirms a transient lipoperoxidation despite protection by

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