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Biomedical subjects

P J Bacon

Publications and source records attributed to P J Bacon.

3 recordsLinked to original sources

Intra-ocular pressure changes using the laryngeal mask airway and tracheal tube.

Intra-ocular pressure was measured before and throughout airway establishment with either the laryngeal mask airway or tracheal tube. Similar measurements were made on removal of either airway and the amount of coughing noted in the first minute after removal. There was a significantly smaller increase in intra-ocular pressure (p less than 0.001) using the laryngeal mask airway, both on placement and removal, than with the tracheal tube. Postoperative coughing was significantly reduced using the laryngeal mask airway (p less than 0.001). There was a significantly greater rise in heart rate using the tracheal tube (p less than 0.01) probably related to an increased cardiovascular response. The laryngeal mask airway is recommended as an alternative to tracheal intubation in routine and emergency intra-ocular surgery.

Aged

Stress distribution in the scapula studied by neutron diffraction.

High intensity neutron beams provide a method of measuring the preferred orientation of apatite crystals in bulk samples of bone. Measurements at seven different sites on the scapula show that the c axes of the crystals lie preferentially along the directions of pull of the attached muscles. The highest orientation is found at positions under the influence of only a single group of muscles, such as M. teres major or M. infraspinatus. In intermediate regions a multiple distribution of crystals is found, able to withstand stresses in more than one direction. The technique provides a method of assessing the distribution of stress in bones.

Animals

Neutron diffraction studies of lumbar vertebrae.

Neutron diffraction measurements of the orientation of the apatite crystals show a significant preference of their c-axes for the vertical direction. This preference increases from bottom to top of each vertebral body and is substantially greater for the second than for the fifth lumbar vertebrae. This is in line with the predominantly vertical forces which the former withstands.

Apatites