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Biomedical subjects

R R Harrison

Publications and source records attributed to R R Harrison.

9 recordsLinked to original sources
PubMed2000

A silicon implementation of the fly's optomotor control system.

Flies are capable of stabilizing their body during free flight by using visual motion information to estimate self-rotation. We have built a hardware model of this optomotor control system in a standard CMOS VLSI process. The result is a small, low-power chip that receives input directly from the real world through on-board photoreceptors and generates motor commands in real time. The chip was tested under closed-loop conditions typically used for insect studies. The silicon system exhibited stable control sufficiently analogous to the biological system to allow for quantitative comparisons.

Animals↗
PubMed1999

An analog VLSI implementation of a visual interneuron: enhanced sensory processing through biophysical modeling.

Flies are capable of rapid, coordinated flight through unstructured environments. This flight is guided by visual motion information that is extracted from photoreceptors in a robust manner. One feature of the fly's visual processing that adds to this robustness is the saturation of wide-field motion-sensitive neuron responses with increasing pattern size. This makes the cell's responses less dependent on the sparseness of the optical flow field while retaining motion information. By implementing a compartmental neuronal model in silicon, we add this "gain control" to an existing analog VLSI model of fly vision. This results in enhanced performance in a compact, low-power CMOS motion sensor. Our silicon system also demonstrates that modern, biophysically-detailed models of neural sensory processing systems can be instantiated in VLSI hardware.

Algorithms↗
PubMed1985

Bag-valve-mask ventilation; two rescuers are better than one: preliminary report.

This study suggests that the bag-valve-mask (BVM) used by a single rescuer with minimal training fails to deliver adequate tidal volumes for resuscitation. When two rescuers use the BVM, tidal volumes are more than recommended and are comparable to those seen with endotracheal intubation. Two-person BVM ventilation should be considered for initial resuscitation in cardiopulmonary arrest.

Humans↗
PubMed1982

Mouth-to-mask ventilation: a superior method of rescue breathing.

Tidal volumes achieved using endotracheal intubation with a self-inflating bag were compared to those achieved with the esophageal obturator airway, a bag-valve mask system, and mouth-to-mask ventilation in an experimental model employing 18 unskilled and 4 partially skilled rescuers. When compared to mean tidal volumes achieved with endotracheal intubation (1,193 ml with unskilled, 942 ml with semi-skilled rescuers), ventilation with the bag-valve-mask system was significantly less (509 and 495 ml tidal volumes) and was, in fact, well below the value of 800 ml recommended for rescue breathing. Mouth-to-mask ventilation produced tidal volumes (1,093 ml and 1,200 ml) not significantly different from those seen with endotracheal intubation. If clinical findings confirm these experimental results, mouth-to-mask ventilation should replace the bag-valve-mask system in the initial management of respiratory arrest.

Humans↗
PubMed1979

Emergency medical technician (EMT-A) instruction of medical students.

In 1977 the Department of Anesthesiology of the Medical College of Virginia coordinated a compulsory 72-hour course for first-year medical students fulfilling all requirements of the Department of Transportation and leading to eligibility for certification of the medical student as an Emergency Medical Technician (EMT-A). We describe the methodology and content of this course, as well as problems encountered and lessons learned. This sound foundation in emergency care concepts will enable the medical student to develop greater competence in critical skills during the clinical years.

Allied Health Personnel↗
PubMedDate not supplied

Nonlinear analysis of biological systems using short M-sequences and sparse-stimulation techniques.

The m-sequence pseudorandom signal has been shown to be a more effective probing signal than traditional Gaussian white noise for studying nonlinear biological systems using cross-correlation techniques. The effectiveness is evidenced by the high signal-to-noise (S/N) ratio and speed of data acquisition. However, the "anomalies" that occur in the estimations of the cross-correlations represent an obstacle that prevents m-sequences from being more widely used for studying nonlinear systems. The sparse-stimulation method for measuring system kernels can help alleviate estimation errors caused by anomalies. In this paper, a "padded sparse-stimulation" method is evaluated, a modification of the "inserted sparse-stimulation" technique introduced by Sutter, along with a short m-sequence as a probing signal. Computer simulations show that both the "padded" and "inserted" methods can effectively eliminate the anomalies in the calculation of the second-order kernel, even when short m-sequences were used (length of 1023 for a binary m-sequence, and 728 for a ternary m-sequence). Preliminary experimental data from neuromagnetic studies of the human visual system are also presented, demonstrating that the system kernels can be measured with high signal-to-noise (S/N) ratios using short m-sequences.

Computer Simulation↗