A method for screening groundwater vulnerability from subsurface hydrocarbon extraction practices.

This paper describes a new screening method for assessing groundwater vulnerability to pollution from hydrocarbon exploitation in the subsurface. The method can be used for various hydrocarbon energy sources, including conventional oil and gas, shale gas and oil, coal bed methane and underground coal gasification. Intrinsic vulnerability of potential receptors is assessed at any particular location by identifying possible geological pathways for contaminant transport. This is followed by an assessment of specific vulnerability which takes into account the nature of the subsurface hydrocarbon activity and driving heads. A confidence rating is attached to each parameter in the assessment to provide an indication of the confidence in the screening. Risk categories and associated confidence ratings are designed to aid in environmental decision making, regulation and management, highlighting where additional information is required. The method is demonstrated for conventional gas and proposed shale gas operations in northern England but can be adapted for use in any geological or hydrogeological setting and for other subsurface activities.

Relationship of ventilatory capacity to hyperbaric exposure in divers.

The results of divers' annual medical examinations were used to assess the effects of diving exposure independent of age, stature, and smoking on forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1). Cross-sectional analysis of records for 858 men showed a significant positive association between the maximal depth that subjects had experienced and FVC but not FEV1. There was a significant negative association for FEV1/FVC%, and this index was also positively correlated with years of diving exposure. Among a subsample of 81 men the forced expiratory flow rate at low lung volume was reduced relative to that of control subjects similarly assessed; the extent of the reduction from the reference value was significantly correlated with the diving exposure. Longitudinal analysis of results for 255 men over a minimum of 5 yr showed that the change in FVC per annum (positive or negative) was correlated with the change in maximal depth; there were no similar associations for FEV1 or FEV1/FVC%. Thus diving exposure affects the vital capacity and the forced expiratory flow rate at small lung volumes. The latter is evidence for narrowing of airways that might be secondary to diving-induced loss of lung elastic tissue; this hypothesis merits further investigation.

The acute orbit: differentiation of orbital cellulitis from subperiosteal abscess by computerized tomography.

A series of 65 patients suffering from acute inflammatory disease of the orbit was studied by CT. Ethmoiditis was the cause in the vast majority; trauma and dental extraction played a lesser role in causation. Orbital cellulitis was diagnosed in 17 and subperiosteal abscess in the remaining 48. It was not possible to differentiate 33 pus-containing abscesses from the six with inflammatory masses (phlegmons). The satisfactory response to aggressive medical treatment in those patients with inflammatory masses that were not drained justifies a more conservative approach; surgical drainage being reserved for those with a deterioration in proptosis, ocular movements or vision. Six abscesses arose de novo, of which some were in the orbital fat rather than the subperiosteal space.

Cerebrovascular disease risk factors: neuroradiologic findings in patients with activated protein C resistance.

PURPOSE: To assess the patterns of abnormal neuroradiologic findings in patients with a hypercoagulable state related to activated protein C (APC) resistance. MATERIALS AND METHODS: Records in 23 patients with a hypercoagulable state related to APC resistance (18 women, five men; average age, 44.5 years) were reviewed for cerebrovascular disease risk factors and other causes of a hypercoagulable state. Computed tomographic scans, magnetic resonance (MR) images, angiograms, and transesophageal echocardiograms were also reviewed. RESULTS: Stroke risk factors or other causes of a hypercoagulable state were found in 12 patients. Arterial infarcts were seen in 18 patients. Hyperintense white matter foci were seen on MR images in six patients. Dural sinus thrombosis was found in four patients. Angiograms of intracranial circulation in six patients showed major artery occlusions in four. MR angiograms in four patients showed internal carotid artery occlusion in one. No major abnormalities were seen in extracranial cerebral vasculature in 15 patients. Transesophageal echocardiograms in 11 patients showed a patent foramen ovale in one patient but no systemic source of embolism. Seven patients had non-central nervous system thrombotic events. CONCLUSION: Patients with APC resistance and stroke appear to differ from the general stroke population in terms of age and frequency of extracranial sources of cerebrovascular disease.

Respiratory effects of a single saturation dive to 300 m.

Lung function and the response to exercise were monitored in seven diver/welders who took part in a test saturation dive to 300 m for an average duration of 12 days; decompression took an average of nine days. Immediately after the dive the forced vital capacity was increased above base line by on average 0.51, the forced expiratory volume by 0.281 and peak expiratory flow rate by 0.71 s-1. There was no change in flow rate at small lung volumes (FEF 75% FVC). Recovery was complete and appeared to have a half time of 28 days. Transfer factor of the lungs for carbon monoxide (TlCO) was reduced by on average 9.6% after the dive but while partial recovery occurred, the values at one year were on average lower than those observed initially. The reason is unclear. One subject developed transient oxygen toxicity with stiff lungs and increased ventilation and cardiac frequency during submaximal exercise; a second subject developed similar changes but without accompanying symptoms. There is need for detailed physiological surveillance of people undertaking deep dives; this should be undertaken in circumstances that permit accurate measurements and full subject cooperation.

Deep vein thrombosis in elderly Hong Kong Chinese with hip fractures detected with compression ultrasound and Doppler imaging: incidence and effect of low molecular weight heparin.

Seventy-eight patients of average age 78 years suffering from an unilateral non-pathological hip fracture underwent compression ultrasound and pulsed and colour Doppler examination of both legs. Twenty-three patients were randomly placed on low molecular weight heparin (LMWH). Twenty-nine (37%) suffered deep venous thrombosis (DVT). There was no statistically significant difference in the incidence of DVT between the control and LMWH groups, and the incidence of DVT in elderly Chinese patients after hip replacement for a hip fracture is similar to that in other studies in Caucasians. There were, however, some differences, namely the contiguous nature of the thrombi rather than focal segmental clots, and the absence of propagation or tail formation. Although the numbers are small, this could possibly represent a population difference. There was a significantly increased occurrence of DVTs on the operated side in both groups. Serial ultrasound examination supports evidence that DVTs occur in the 1st week postoperatively, but there were also a number of patients who developed DVTs in the 2nd week. There was no statistically significant difference in overall incidence of DVT between patients on prophylactic heparin and the control group. Patients on prophylactic heparin had no thigh DVTs in comparison to the control group. LMWH may thus be effective in preventing thigh DVTs and pulmonary emboli.

A randomized study comparing laparoscopic versus open repair of perforated peptic ulcer using suture or sutureless technique.

OBJECTIVE: This study compares laparoscopic versus open repair and suture versus sutureless repair of perforated duodenal and juxtapyloric ulcers. BACKGROUND DATA: The place of laparoscopic repair of perforated peptic ulcer followed by peritoneal toilet of the peritoneal cavity has been established. Whether repair of the perforated peptic ulcer by the laparoscopic approach is better than conventional open repair and whether sutured repair is better than sutureless repair are both undetermined. METHODS: One hundred three patients were randomly allocated to laparoscopic suture repair, laparoscopic sutureless repair, open suture repair, and open sutureless repair. RESULTS: Laparoscopic repair of perforated peptic ulcer (groups 1 and 2) took significantly longer than open repair (groups 3 and 4; 94.3 +/ 40.3 vs. 53.7 +/ 42.6 minutes: Student's test, p < 0.001), but the amount of analgesic required after laparoscopic repair was significantly less than in open surgery (median 1 dose vs. 3 doses) (Mann-Whitney U test, p = 0.03). There was no significant difference in the four groups of patients in terms of duration of nasogastric aspiration, duration of intravenous drip, total hospital stay, time to resume normal diet, visual analogue scale score for pain in the first 24 hours after surgery, morbidity, reoperation, and mortality rates. CONCLUSIONS: Laparoscopic repair of perforated peptic ulcer is a viable option. Sutureless repair is as safe as suture repair and it takes less time to perform.