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Biomedical subjects

E A Frost

Publications and source records attributed to E A Frost.

At least 19 recordsLinked to original sources
PubMed1991

Extracorporeal shock wave lithotripsy of gall stones: an in vitro comparison between an electrohydraulic and a piezoceramic device.

A comparative study of the effectiveness of two types of lithotripter in fragmenting gall bladder stones is reported. The machines used were a Piezolith 2300, which generates shock waves by the piezoceramic principle, and a Dornier MPL 9000, which produces the shock waves by underwater spark discharge. With each machine, corresponding stones of 45 pairs of weight and volume matched calculi (median volume 0.5 cm3, median diameter 10.5 mm) obtained at cholecystectomy were treated. All stones were successfully disintegrated (fragments smaller than 2 mm) with up to 5400 (median 628) shocks with the Piezolith and 3450 (median 428) shocks with the MPL 9000 lithotripters. With the Piezolith, operating at the highest power setting, a 1.65 fold median higher number of shocks was required for stone fragmentation than with the MPL 9000 at a medium power setting. Stone volume seemed to be the only determinant which affected ease of fragmentation; composition and density of the stones as assessed by computed tomography did not seem to be governing factors.

Cholelithiasis↗
PubMed1989

The lessons from in vitro lithotripsy for the clinical treatment of gallstones.

Fifty-eight gallbladder stones were treated in vitro, using a Wolf Piezolith 2300 lithotripter, to discover whether complete fragmentation (i.e., no particles greater than 2 mm diameter) could be achieved by lithotripsy alone. In 16 stones this was accomplished with up to 6000 shocks being administered. The degree of fragmentation was judged first by eye during the experiment and then by both microscopy and sieving of the debris. Eye judgement proved to be an unreliable indicator with 23 of the 42 stones in the failed lithotripsy group receiving 6000 shocks or less. Cholesterol analysis and high resolution radiography revealed no significant differences between the successfully and unsuccessfully fragmented stones, but X-ray diffractometry did show a higher incidence of inorganic calcium salts in the latter group. This study shows that lithotripsy can successfully fragment gallbladder stones, but that a minimum of 6000 shocks, using the Piezolith 2300, should be given to ensure adequate treatment. Additionally, the presence of radiopaque stones does not necessarily preclude successful treatment by this method.

Cholecystectomy↗
PubMed1979

Pulmonary shunt as a prognostic indicator in head injury.

Severe head injury may cause momentary respiratory arrest. Resultant hypoxia would increase cerebral edema and adversely affect the quality of survival. This study examines the effect of hypoxemia on outcome. Pulmonary shunt was calculated as a convenient measurement of respiratory insufficiency in 86 severely head-injured patients who underwent surgery. All samples were taken shortly after induction into anesthesia when controlled ventilation with high inspired-oxygen concentration had been established. In 39 patients who improved, mean pulmonary shunt was 8.9%. Twelve patients who survived with deficit showed a mean shunt of 13.6%, and in 35 patients who died, the mean initial shunt was 15.6%. No significant correlation was found between abnormal chest x-ray findings or the occurrence of hypertension and shunt percentage. The American Society of Anesthesiologists at-risk classification correlated grossly with the outcome. Early pulmonary shunt is a prognostic indicator in severe head injury and should be used in conjunction with the Glasgow Coma Scale in assessing outcome. Despite an apparently adequate respiratory pattern, all patients with severe head injury must be assumed to be hypoxic until proven otherwise. While hypoxemia may prove to be refractory in overwhelming injury, patients who score low on the Glasgow Coma Scale but who have relatively normal oxygen exchange may still survive with little deficit.

Adolescent↗
PubMed1977

Effects of positive end-expiratory pressure on intracranial pressure and compliance in brain-injured patients.

Hypoxic pulmonary disorders and head injuries associated with increased intracranial pressure (ICP) frequently co-exist. Positive end-expiratory pressure (PEEP) improves hypoxemia but has been reported to impede cerebral venous return, potentially causing a further increase in ICP. This study examined the effects of PEEP on ICP at different levels of brain compliance. continuous ICP recordings were obtained after insertion of Scott cannulas to the lateral ventricles of seven comatose patients. Brain compliance was assessed by calculation of the pressure volume index. Patients were maintained in a 30 degrees head-up position. Maintenance of PEEP to levels of 40 cm H2O pressure for as long as 18 hours did not increase ICP in patients with either normal or low intracranial compliance, and did not increase ICP in the absence of pulmonary disease. Central venous pressure and pulmonary artery wedge pressure increased proportionately as PEEP was increased. No consistent changes were found in blood pressure recordings, nor were there any reductions in cardiac output found during the studies. Abrupt discontinuation of PEEP did not result in increased ICP except for a transient rise on two occasions when respiratory secretions became copious and the patients were inadequately ventilated. Improved oxygenation in two patients as a result of PEEP was concomitant with improved intracranial compliance and neurological status. In patients with brain injuries, PEEP improves arterial oxygenation without increasing ICP as previously supposed. Consequently, PEEP is a valuable form of therapy for the comatose patient with pulmonary disorders such as pneumonia or pulmonary edema.

Adult↗