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Biomedical subjects

A E Churches

Publications and source records attributed to A E Churches.

10 recordsLinked to original sources
PubMed1988

A new device to aid knee surgery. A leg-positioning mechanism.

A novel leg-positioning and holding mechanism has been developed to facilitate knee surgery. The normal thigh tourniquet is used as the point of attachment of the mechanism. The knee may be placed in any of the positions desired for knee surgery by means of a single control lever. To facilitate alignment during arthroplasty a pointer has been incorporated to indicate the midline of the limb. The leg positioner has proved useful during knee arthroplasty, high tibial osteotomy, arthroscopic procedures, and ligament reconstruction. Its use has reduced fatigue, freed the assistant for other tasks, and held the limb more firmly than was possible hitherto.

Humans↗
PubMed1982

Functional adaptation of bone in response to sinusoidally varying controlled compressive loading of the ovine metacarpus.

To obtain carried load, quantitative data relating functional adaptation of bone to controlled, sinusoidally-varying, compressive loading of constant amplitude was applied to the right metacarpal bones via Steinmann's pins inserted through the metaphyses in 13 sheep. Loading was applied for two 1-hr periods/day at 24 cycle/minute, through-out a test period of 28 days. The amplitude of the applied loading was varied from test to test, giving peak stresses on the mid-diaphyseal cross-section that ranged from 2.2-8.3 N/mm2. In the mid-diaphyseal region, the bone responded by periosteal apposition, with maximum proliferation usually occurring on the medio- and laterovolar borders and relatively little new bone on the dorsal and volar aspects. The cross-sectional areas of new bone was roughly proportional to the applied stress, with a maximum increase of approximately 8% in the most highly stressed bones. There was also evidence that periosteal resorption had occurred, presumably as the first step in the apposition process. A significantly increased level of intracortical activity was found in the right metacarpus as compared with the contralateral bone.

Adaptation, Physiological↗
PubMed1977

Measurement errors in pneumotachography due to pressure transducer design.

When pneumotachography is used during intermittent positive pressure ventilation (IPPV), the design of some differential pressure transducers can cause measurement errors. These errors may be avoided by using differential pressure transducers which have small, equal chambers free from temperature sensitive electrical elements. Few of the transducers which are sensitive enough for clinical use fulfil these requirements.

Diagnostic Errors↗
PubMed1975

Errors in pneumotachography with intermittent positive pressure ventilation.

Instrument errors that can occur when pneumotachography is used during Intermittedt Positive Pressure Ventilation (IPPV) have been described previously (Kafer 1973). Our efforts to eliminate these errors led to the discovery of further inaccuracies, which appear to be due to the design of the differential pressure transducers used with pneumotachograph head. A system was used in which a sine-wave pump delivered a constant tidal volume to a dummy lung, the tidal volume being measured by means of a pneumotachograph. Using Grass, Statham and Devices differential pressure transducers, the volume recorded as leaving the dummy lung was consistently greater than that recorded as entering, and changing the pneumatic polarity of the differential pressure transducer produced large differences in the recorded volume. In some cases the error was greater than the volume being measured. There would seem to be several causes of such errors. The Sanborn 270 differential pressure transducer and the Greer micromanometer appeared to be free of these artifacts. The results of this study throw into doubt much previously published work using pneumotachography during IPPV.

Equipment and Supplies↗