Biomedical subjects
Publications and source records attributed to P J Bishop.
A partial calvaria, dredged from the sea-bed some years previously, was referred to us for examination. The presence of a well-established mollusc colony on the vault allowed us to establish a minimum elapsed time since death. Such a cross-disciplinary co-operative study is of great advantage in expediting a satisfactory conclusion.
During the breeding season, each tympanic membrane of males of the Old World treefrog Petropedetes parkeri is decorated with a single, prominent, fleshy tympanic papilla. The tympanic papilla, located dorsally on the tympanic membrane, is covered by an epidermal surface and is composed of non-ossified, spongiform tissue containing a number of globular, fluid-filled vesicles found at highest density near the papillar tip. These vesicles appear to have exit pores and are probably simple alveolar exocrine glands. Injecting sound into the pressurized vocal cavity of the male and measuring the vibration velocity response of the tympanic membrane revealed that from 0.3 to 2.0 kHz the tympanic papilla velocity amplitude is on average 20 dB lower than that of a point diametrically opposite on the ventral half of the tympanic membrane. The close agreement between the dominant frequency of the call and the frequency of the maximum spectral peak of the Fast Fourier Transform of the impulse response of the eardrum is consistent with the use of the eardrum in this species both as a call receiver and as a call radiator, similar to the function suggested for the eardrum of the male bullfrog Rana catesbeiana. Unexpectedly, surgically removing the tympanic papilla lowered the frequency of the peak vibrational amplitude, testifying to the importance of membrane tension as a dominant factor in the vibratory behavior of the eardrum. During normal positive-pressure breathing, the tympanic papillae move conspicuously, suggesting a possible rôle as a visual signal.
STUDY DESIGN: Electromyographic profiles from the neck muscles of five young, healthy men were obtained to study the muscular, activation patterns during dynamic external loading. OBJECTIVES: To examine the myoelectric activity of selected cervical muscles during dynamic loading, and to explore the reaction of the cervical muscles to different loading conditions. SUMMARY OF BACKGROUND DATA: The response of cervical muscles throughout dynamic external loading is not well understood. Electromyography provides information, within certain limitations, about the neural drive to various components of the musculature. Such information on activation, combined with geometric parameters of the musculoskeletal tissues, constitutes a tool for helping to understand the mechanism of head and neck impact-related injury. METHODS: Subjects were tested with the head and neck in the neutral and prebent positions. Dynamic loads were applied laterally to each subject by free-falling masses to create peak dynamic loads ranging from about 40 to 100 N. Force and electromyographic data were recorded, and cross-correlations from linear envelope electromyography were calculated. RESULTS: The peak electromyogram showed large differences between the two applied loads and between subjects. There were time delays (75-165 msec) between the peak applied force and the peak electromyogram. The muscles on the contralateral side demonstrated different electromyographic profiles between subjects. Within subjects, the electromyographic profiles from each muscle were consistent for the same trial conditions. CONCLUSIONS: Electromyographic profiles and the cross-correlator coefficients for cervical muscles have shown reproducible intrasubject muscle synergies, which were not sensitive to the magnitude of applied load and the posture of the head. Intersubject muscle activity patterns varied.
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Esophageal atresia with distal tracheoesophageal fistula has been treated at one institution between 1951 and 1983 primarily by prompt transpleural repair without gastrostomy. Two hundred and seventy one patients are assigned to three time periods: (1) 1951 to 1963, prior to modern intensive care; (2) 1964 to 1973, the initial era of mechanical ventilation; and 1974 to 1983, the era of readily available ventilators and TPN. During these time periods mean birthweight decreased from 2,780 g to 2,670 g to 2,500 g, while the incidence of associated anomalies increased from 41% to 44% to 55%. Eleven patients had no operation or gastrostomy only and died. Twenty (predominantly in the early years) had staged repairs with initial gastrostomy and fistula ligation. Primary anastomosis was done in 240 patients regardless of birth weight, 229 of which were by the transpleural approach. Gastrostomy was performed primarily in 28 patients for varied indications. Operative mortality (definitive as well as staged repairs) fell over the three time periods from 44% to 15% to 7%. Anastomotic leaks occurred in 20% of patients who underwent primary repair regardless of the time period. The mortality associated with a leak, however, decreased from 88% to 47% to 0%. Anastomotic strictures requiring more than two dilatations occurred in 15% in all periods. The overall incidence of recurrent fistula was 5%. Of 200 patients surviving the initial hospitalization, follow-up longer than 2 months is available for 156 patients with a median follow-up of 30 months. There were 15 late deaths.(ABSTRACT TRUNCATED AT 250 WORDS)
The effect of a hockey helmet and face shield on the head and neck during inertial loading was studied. A Hybrid III Anthropometric Test Dummy (ATD) was struck from both the front and rear by a spring-loaded, instrumented striker moving at 2.9 ms-1. Data were collected from a triaxial force transducer mounted at the atlanto-occipital (a-o) junction of the ATD, a load cell in the striker, and by cinematography (250 fps). Angular kinematics of the head and moments of force about the a-o junction were determined along with impact force levels. When compared to a bare-head condition, the addition of a helmet and face shield caused an increase in head angular displacement (20-40%) but did not affect head angular acceleration. Axial and shear forces at the a-o junction did not change appreciably with the addition of a helmet and face shield. A triphasic pattern was evident for the neck moments including a small phase which represented a seating of the headform on the nodding blocks of the uppermost ATD neck segment, and two larger phases of opposite polarity which represented the motion of the head relative to the trunk during the first 350 ms after impact. No substantial differences were apparent between the helmeted and non-helmeted trials. The magnitudes of forces and moments found in the present study were well within tolerance levels reported by others (Melvin, 1979; Cheng et al., 1982). It was concluded that the increase in angular displacement of the head, with the addition of a helmet and face shield, does not place the wearer in a position of increased risk of cervical spine trauma.
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Seven brands of bicycle helmets were compared by means of a drop test using an instrumented Hodgson-WSU headform, on the front (F), rear (R) and left side (LS) locations from a height of 1.0m and on the right front boss (RFB) from either 1.0m or 1.75m. Acceleration signals from the headform were computer processed to yield peak acceleration and the Gadd Severity Index (GSI). Significant differences between helmets and within helmets at different locations were found. Helmets with crushable polystyrene liners were much superior to those with soft foam liners. The superiority of the polystyrene liners disappeared however when helmets were subjected to two consecutive drops to the same location (R). The results also indicated that for most cases the GSI was between 800-1200 but there were two helmets that had values in excess of 1500. Clearly not all bicycle helmets provide equivalent levels of protection and some are much superior to others.
A study of the hockey helmet and face shield as potential contributors to cervical spinal cord trauma (burst vertebral fractures and cord injury) was undertaken. The main concern was whether the alteration in the location of the c of m or in the mass moment of inertia (Icm) of a player's head, induced by a helmet and face shield, would predispose him to a hyperflexion neck posture. The c of m and Icm of a bare Hodgson-WSU humanoid headform (H) were first determined and then the same measures were made with a helmet (H + h) and with a helmet and face shield (H+h+f). Of the nine different helmet and face shields evaluated none caused the c of m to move more than 6mm from that of H. Measurements made on minor hockey players aged 8 to 15 years indicated that the proportion of maximum isometric neck strength required to hold the head in the typical skating posture while wearing a helmet and face shield ranged from 8% to 12%. It seems unlikely that this would predispose to the hyperflexion neck posture. The Icm of H+h increased by 68% and of H+h+f by 89% from that of H and when translated to a pivot point on the neck (C7-T1) the change in I was 30% for H+h and 41% for H+h+f. The effect on the neck of such an increase in I could lead to strain on the neck ligaments and musculature but would not account for a burst fracture of a vertebrae. Thus, in and of themselves, the helmet and face shield do not appreciably alter the dynamics of the neck thereby predisposing the wearer to increased neck injury risk.
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A study of contemporary book reviews and other notices enables us to trace the reception of the stethoscope and Laënnec's book between 1816 and 1826. It is quite clear from these that the stethoscope was welcomed with enthusiasm by most people who saw it as the first major diagnostic tool medicine had ever had. Laënnec's book was recognised as being the most important, interesting, accurate, and complete work on diseases of the chest that had ever been published.
A sample of new ice hockey face masks was struck over the nose or eye of a headform by pucks shot at velocities of 11-39 m/s (25-87 m.p.h.). Deformation of the masks was studied from high speed film. Acceleration pulses transmitted to the center of gravity of the headform were recorded. Peak accelerations never exceeded 86 G's and were well below reported concussion thresholds (200 G's). The film showed contact of the mask or puck with the face at puck velocities of 28 m/s (60 m.p.h.) and above. These results indicate a somewhat lower "safe" puck impact velocity (28 m/s) than that stated by the Canadian Standards Association (32 m/s) under the standard which applied to these masks. Some boys 12 years and older can shoot pucks at 28 m/s (60 m.p.h.). We urge that all manufacturers of sports protective equipment incorporate state of the science, quantitative evaluations of their products, beyond minimum CSA standard testing, in their design programs to improve the quality of information transmitted to the public.
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The response of the Gentex DH-151 (contact type) and Gentex 411 (suspension type) aircrew helmets to low-magnitude impacts, such as those sometimes encountered during cockpit buffeting, in ejection, and in parachute landings, was studied to augment the data base on helmet performance. The helmets, mounted on a Hodgson headform, were dropped on the crown and rear at impact velocities up to 4.97 m/s. Acceleration time histories were tape recorded and digitized and Gadd Severity Indices (GSI), among others, were calculated from the resultant acceleration curve. Both helmets kept the GSI below predicted concussion thresholds at 4.97 m/s and were considered to perform well on initial impacts. On second impacts, the GSI rose considerably because the shell and liner of the DH-151 cracked and the suspension of the "141" stretched during the first blow. Improvement of the multiple impact performance of both helmets appears desirable, although the suspension helmet performed slightly better than the contact helmet with respect to the criterion used.
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