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Biomedical subjects

D R Bacon

Publications and source records attributed to D R Bacon.

At least 73 records · Page 4Linked to original sources
PubMed1988

Controlled vascular corrosion casting of the rabbit eye.

We have refined the technique of vascular corrosion casting with methacrylate to permit the reproduction of physiological states of vascular tone and to produce sturdy castings of ocular microvasculature. The method entails careful maintenance of homeostasis up to the moment of plastic perfusion, avoidance of vascular rinsing or fixation with the attendant anoxia, reduction of the viscosity of the casting resin without impairing the properties of the resultant polymer, addition of a cross-linking agent to increase the strength of the plastic, and injection at physiological temperature and pressure. This casting regimen reproduces the normal anatomical conditions of blood vessels and can be used to demonstrate altered conditions of vascular tone. In all instances, the second, untouched eye serves as a control for unilateral manipulations. Special problems of replicating the ocular vasculature are related to the intraocular pressure, which opposes the vascular perfusion pressure and constitutes an impediment to perfusion.

Animals↗
PubMed1987

Pressure waveforms generated by a Dornier extra-corporeal shock-wave lithotripter.

Pressure waveforms in the acoustic field generated by a Dornier (HM3) shock-wave lithotripter have been measured using a bilaminar shielded PVDF membrane hydrophone in water. Using these waveforms, values of the peak-positive (p+) and peak-negative pressure (p-) at various positions in the field have been estimated. At the focus, p+ is 38.6 MPa (standard deviation = 9.0 MPa) and p- is 10.1 MPa (standard deviation = 1.0 MPa) at 20 kV discharge potential and an electrode separation in the range 1.3 to 2.4 mm. The peak-positive pressure is found to fall to 50% (-6 dB level) at about 60 mm either side of the focus on the major axis of the reflector and on a 10 mm radius circle around the focus in the focal plane. A shot-to-shot variation of +/- 25% in p+ is attributed to the inherent variability of the electrical discharge which may result in changes in the exact position and strength of the acoustic field. The results reported are considered to be more accurate than those of previous measurements due to the relatively flat frequency response of this type of hydrophone.

Acoustics↗
PubMed1986

Rapidly progressive myelomonocytic leukemia (juvenile CML).

A rare type of rapidly fatal childhood leukemia, generally called juvenile chronic myelogenous leukemia, is characterized by absence of the Philadelphia chromosome and a predominantly monocytic proliferation, among other features. Unlike Philadelphia chromosome positive chronic myelogenous leukemia, this disease is neither chronic nor principally a disorder of granulocytic cell lines. A case is presented, with several clinical and laboratory parameters useful in establishing the correct diagnosis, and a change in terminology to "rapidly progressive juvenile myelomonocytic leukemia" is proposed.

Child↗
PubMed1980

A pvdf membrane hydrophone for operation in the range 0.5 Mhz to 15 Mhz.

A new form of hydrophone for measuring the spatial and temporal distributions of pressure within the fields from medical ultrasonic equipment is described. The device comprises an acoustically transparent plastic membrane with a small, central region activated to provide a freely-suspended piezoelectric element. This form of detector offers several advantages over conventional hydrophone probes employing ceramic elements, in particular a flat frequency response. The performance characteristics of a prototype membrane hydrophone and some possible developments and applications are described.

Calibration↗
PubMedDate not supplied

Finite amplitude distortion of the pulsed fields used in diagnostic ultrasound.

A simple theoretical model of the non-linear propagation of pulsed focused acoustic beams is described. It enables the distortion of the peak cycle of the pulse to be calculated from a few experimentally measured parameters. The model is discussed, and justified for application to the fields from medical ultrasonic diagnostic equipment. It is particularly relevant for specifying the degree of distortion present, as might be required by future written standards for diagnostic equipment performance. Preliminary experimental verification of the model is reported.

Acoustics↗
PubMedDate not supplied

To define a specialty: a brief history of the American Board of Anesthesiology's first written examination.

The initial written examination of the American Board of Anesthesiology, a division of the American Board of Surgery, was given on March 28, 1939. For all anesthesiologists, this date has double significance. First, what was meant by anesthesiology as a medical specialty was defined through the questions posed on the first examination. Second, the physicians being tested that day were among the first physician-anesthetists to exploit the newly created path to recognition as specialists in the science and art of anesthesia by the American medical hierarchy. Gaining the support of organized medicine was an involved and arduous struggle that consumed most of the 1930s. A triumvirate of visionaries, Paul Wood, John Lundy, and Ralph Waters, was necessary to crystalize the goal of specialty recognition of physician-anesthetists. The first written examination was the consummation of this dream of equal status for anesthesia. The examination would not become repetitious, and within the first decade of testing, the style would change from an essay format to multiple-choice questions similar to the current form.

Anesthesiology↗
PubMedDate not supplied

For all the world to see: anesthesia at the 1939 New York World's Fair.

The 1939 New York World's Fair presented a unique opportunity for the newly recognized specialty of anesthesiology to be presented to the general public. With funding supplied by the Winthrop Chemical Company of New York City and careful planning, a committee of physician-anesthetists was able to design a display that illustrated all aspects of the physician-anesthetist's role in health care: general "gas" anesthesia, regional techniques, pain management, resuscitation, and oxygen therapy. Further information was offered concerning training of physicians in the specialty, and speculation involving the future mission of anesthesiology was presented. Surprisingly, issues and discussions concerning the fashion in which anesthesia was to be presented at this exhibit remain germane to current presentations of the specialty to the general public. Although no record remains of the public's response to the exhibit, the World's Fair was an international showcase and an important opportunity for public recognition of anesthesiology.

Anesthesia↗
PubMedDate not supplied

Bilateral pneumothoraces from a malfunctioning resuscitation valve.

Disposable resuscitation valves appear as relatively simple devices used to ventilate patients during both emergent situations and transport from the operating room to the intensive care unit. We report a case of a nonfunctional disposable resuscitation valve that resulted in barotrauma and bilateral pneumothoraces. A routine check for proper function of these valves before use in critically ill patients may help to eliminate such cases.

Aged↗
PubMedDate not supplied

Emery A. Rovenstine and regional anesthesia.

BACKGROUND AND OBJECTIVES: Emery Andrew Rovenstine was a dominant figure in anesthesiology in the United States between 1935 and 1960. Among his many contributions to the specialty, his regional anesthesia practice remains less well known. This paper explores Rovenstine's career and his contributions to regional anesthesia. METHODS: Original documents studied and classified for this investigation included all of Rovenstine's published papers and the extant documents of the original American Society of Regional Anesthesia. Interviews with several physicians who knew Rovenstine were conducted. Secondary source materials, including biographies of Rovenstine, were perused. RESULTS: Rovenstine made a major contribution to regional anesthesia through patient care, teaching, and political action. Many of his students went on to become leaders in anesthesiology and emphasized regional anesthesia in the second half of the twentieth century. CONCLUSIONS: Emery A. Rovenstine did much to popularize regional anesthesia and ensure a rightful place for its techniques within the armamentarium of the anesthesiologist. Keeping alive the traditions of Gaston Labat at Bellevue, Rovenstine's contributions to regional anesthesia on all levels were considerable. Most importantly, he ensured an enduring role for regional anesthesia through the recurring contributions of his pupils.

Anesthesia, Conduction↗