Transcutaneous oxygen (TcPO(2)) measurements provide a noninvasive, objective determination of the oxygen level at the skin surface. This offers a means of estimating the underlying circulation and tissue oxygenation. The purpose of the pilot study was to measure the TcPO(2) value of the lower extremity of healthy men and women and of patients with peripheral arterial disease (PAD) in 4 different body and leg positions 24 hours after peripheral vascular surgery reconstruction. The specific aim was to determine if lower-extremity TcPO(2) measurements were affected by changes in extremity position in these subject populations. A convenience sample of 4 healthy health care professionals and 4 patients who had peripheral vascular reconstruction surgery 24 hours before the measurements were studied. Subjects were studied in 4 different leg and body positions: supine with legs extended, sitting with legs dependent, a 5 degrees head-up reverse Trendelenburg, and supine with legs elevated 10 in. The Radiometer TCM30 TcPO(2) monitor was used to carry out these measures. Findings revealed a statistically significant difference in TcPO(2) measurements between the 2 groups, with the healthy subjects having a significantly higher TcPO(2) measurement in all extremity positions compared with the revascularized subjects with PAD (P =.02-.05). Significant changes were noted in both the foot temperature (P =.03) and TcPO(2) measurements with extremity positions within the healthy subject group (P =.001). The foot and leg TcPO(2) measurements affect from leg and body position did not reach significance (P =.09) in the subjects with PAD. No change in foot temperature with extremity positioning (P =.42) was noted in the subjects with PAD. This pilot study provides a base in which additional research will be performed with TcPO(2) measurements in both the healthy and revascularized person.

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Oxidation of fugitive methane in ground water linked to bacterial sulfate reduction.

When fugitive methane migrates upward along boreholes of oil and gas wells, it may migrate into shallow ground water or pass through overlying soil to the atmosphere. Prior to this study, there was little information on the fate of fugitive methane that migrates into ground water. In a field study near Lloydminster, Alberta, Canada, we found hydrogeochemical evidence that fugitive methane from an oil well migrated into a shallow aquifer but has been attenuated by dissimilatory bacterial sulfate reduction at low temperature ( approximately 5 degrees C) under anaerobic conditions. Evidence includes spatial and temporal trends in concentrations of methane and sulfate in ground water and associated trends in concentrations of bicarbonate and sulfide. Within 10 m of the oil well, sulfate concentrations were low, and sulfate was enriched in both 34S and 18O. Sulfate concentrations had a strong positive correlation with delta13C values of bicarbonate, and sulfide was depleted in 34S compared to sulfate. These data indicate that bacterial sulfate reduction occurred near the production well. Near the oil well, elevated concentrations of bicarbonate were observed, and the bicarbonate was depleted in 13C. Modeling indicates that the main source of this excess 13C-depleted bicarbonate is oxidized methane. In concert with the sulfate concentration and isotope data, these results support an interpretation that in situ bacterial oxidation of methane has occurred, linked to bacterial sulfate reduction. Bacterial sulfate reduction may play a major role in bioattenuation of fugitive natural gas in ground water in western Canada.

Fossil Fuels↗