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Biomedical subjects

J C Farmer

Publications and source records attributed to J C Farmer.

At least 19 recordsLinked to original sources
PubMed2001

Rural deprivation: reflecting reality.

In the United Kingdom (UK) there is currently an upsurge of interest in rural affairs. This brings the potential to address some of the gaps in rural health care research. The appropriate description and measurement of rural deprivation is one area consistently identified by UK rural practitioners and policymakers as urgently requiring evidence. Appropriate identification and measurement of deprivation within a rural context is important so that primary care resources can be targeted at those with greatest need. It is believed that current measures of deprivation are inappropriate for rural settings, but relationships between life circumstances and health are only beginning to be addressed by empirical research. In this paper we propose an approach to researching rural deprivation. It is important to be clear about definitions of rurality and deprivation and about the purpose of measurement. The requirement to test a range of indicators for their association with health status and health care need in rural areas and to gather more locally relevant data within primary care settings is highlighted. The relevance, for primary care, of exploring rural deprivation is suggested, along with ideas about a way forward in generating knowledge that can help to characterise and measure rural deprivation in a more sensitive manner.

Cultural Deprivation↗
PubMed2000

Laryngeal radionecrosis and hyperbaric oxygen therapy: report of 18 cases and review of the literature.

Laryngeal radionecrosis is a difficult late complication of radiotherapy. It is associated with hoarseness, edema, pain, weight loss, and upper airway obstruction. The medical treatment options are limited, and in severe cases, the patient may require tracheostomy or laryngectomy. We report clinical results in 18 patients treated with adjunctive hyperbaric oxygen (HBO) therapy for severe radionecrosis of the larynx. Of these 18 patients, 2 had grade 3 and 16 had grade 4 radionecrosis. The patients received a mean number of 41 HBO treatments (range, 6 to 80) at 2 atmospheres absolute for 2 hours, twice a day, 6 days a week. Thirteen patients (72.2%) had a major improvement after HBO therapy, and none of them required total laryngectomy. All patients preserved their voice and deglutition in good or normal condition. Five patients (27.8%) failed to have a good response to HBO and underwent total laryngectomy. One of these patients had local recurrence of his cancer 4 months later, and the other 3 had significant concurrent medical problems. The remaining patient received only 6 HBO treatments because of emergency heart surgery. These encouraging results are comparable to those of smaller previous studies suggesting that HBO has a beneficial effect in the management of advanced laryngeal radionecrosis.

Adult↗
PubMed1998

The changing nature of admissions to a spinal cord injury center: violence on the rise.

The purpose of this study was to analyze changing etiologies for admission to a spinal cord injury center. This study was designed to retrospectively analyze the etiology of admissions to a spinal cord injury center during a 15-year period, specifically gunshot versus nongunshot wound injuries. Gunshot wounds are a well-recognized cause of spinal cord injury. In some centers, up to 52% of admissions are due to this, and these trends are believed to be increasing. All patients with spinal cord injury admitted to our center between 1979 and 1993 were analyzed. Frequencies of specific etiologies were determined and then comparisons were made between gunshot wound and nongunshot wound groups. Factors analyzed included age, male/female ratio, ethnic make-up, marital status, employment status, level of injury, and neurologic status. One thousand eight hundred seventeen patients were included. Overall, gunshot wound spinal cord injuries compromised 16.9% of injuries. A clear trend of increasing numbers of admissions was seen between 1984 and 1993 because of this. Gunshot wounds and nongunshot wounds differed dramatically in terms of age, ethnic make-up, marital status, employment status, and neurologic status. Cost attributed to treating gunshot wound injuries at our center for 1993 was 5.4 million dollars. Gunshot wounds as a cause of spinal cord injury are increasing at an alarming rate. The demographics of the gunshot wounds and nongunshot wound spine cord injuries differ significantly.

Accidents, Traffic↗
PubMed1998

Bilateral cochlear implants controlled by a single speech processor.

OBJECTIVE: This study aimed to assess, in one profoundly hearing impaired subject, potential benefits and limitations in placing bilaterally implanted scala tympani electrode arrays under control of a single speech processor. STUDY DESIGN: All available stimulation sites in both ears were compared in studies of pitch discrimination and pitch ranking, identifying three bilateral pairs capable of supporting interaural comparisons with no perceptible difference in pitch. Using those pairs, the subject's ability to lateralize sound was studied as a function of interaural time delay and interaural amplitude difference. Consonant identification scores were obtained for continuous interleaved sampling processors using various unilateral and bilateral combinations of electrodes. RESULTS: For loudness-matched stimuli composed of 50-msec bursts of 80-microsec/phase pulses at 480 pulses/sec, the subject was able to identify the ear receiving the earlier onset for interaural delays at least as brief as 150 microsec for all three matched pairs. For similar simultaneous stimuli, the subject could identify the ear receiving the louder signal for the smallest deviations from loudness-matched amplitudes available from the implanted electronics. The consonant studies found no evidence that bilateral stimulation per se degrades speech processor performance, even for arbitrary divisions of information between the two ears. Additional contralateral as well as ipsilateral channels were observed to improve speech processor performance. CONCLUSIONS: The ability of this subject to lateralize sounds on the basis of interaural delay or loudness difference, combined with the consonant identification results, supports further use of coordinated binaural stimulation to improve cochlear implant users' ability to understand speech, especially in the presence of competing speech noise.

Adult↗
PubMed1997

Vertebral artery occlusion associated with cervical spine trauma. A prospective analysis.

STUDY DESIGN: Radiographs and charts of 61 patients sustaining cervical spine trauma were studied prospectively to determine the incidence of vertebral artery injuries and possible correlative factors. Statistical analysis was conducted using chi-square testing of a two-way classification system. OBJECTIVES: To elucidate the incidence of vertebral artery injuries associated with cervical spine trauma, and to determine the value of various factors in predicting the existence of a vertebral artery injury. SUMMARY OF BACKGROUND DATA: During a 7-month period, 61 patients (41 male patients, 20 female; average age, 40.3 years) with cervical spine trauma were studied. METHODS: All patients admitted to the authors' hospital with cervical spine injuries underwent magnetic resonance imaging and magnetic resonance angiography of their cervical spine. All magnetic resonance angiographies were examined for vertebral artery injury. Data on demographics and the injury were recorded. RESULTS: Complete disruption of blood flow through the vertebral artery was demonstrated by magnetic resonance angiography in 12 of the 61 patients (19.7%). Ten of the 12 patients (83%) had either flexion distraction or flexion compression injuries. Age, sex, mechanism of injury, neurologic impairment, and associated injuries were not statistically significant in predicting the presence of a vertebral vessel occlusion. CONCLUSION: The findings in this study may support the need for vertebral vessel evaluation in selective patients, particularly those with flexion injuries and with neurologic symptoms consistent with vertebral artery insufficiency syndrome that do not correlate with the presenting bone and soft-tissue injuries.

Adolescent↗
PubMed1997

Pressure gradients affecting the labyrinth during hypobaric pressure. Experimental study.

Hypobaric effects on the perilymph pressure were investigated in 18 cats. The perilymph, tympanic cavity, cerebrospinal fluid, and systemic and ambient pressure changes were continuously recorded relative to the atmospheric pressure. The pressure equilibration of the eustachian tube and the cochlear aqueduct was studied, as well as the effects of blocking these channels. During ascent, the physiologic opening of the eustachian tube reduced the pressure gradients across the tympanic membrane. The patent cochlear aqueduct equilibrated perilymph pressure to cerebrospinal fluid compartment levels with a considerable pressure gradient across the oval and round windows. With the aqueduct blocked, the pressure decrease within the labyrinth and tympanic cavities was limited, resulting in large pressure gradients toward the chamber and the cerebrospinal fluid compartments, respectively. We conclude that closed cavities with limited pressure release capacities are the cause of the pressure gradients. The strain exerted by these pressure gradients is potentially harmful to the ear.

Animals↗
PubMed1997

Cochlear implant studies at Research Triangle Institute and Duke University Medical Center.

Examples from several areas of cochlear implant research are presented, with emphasis on the continuous interleaved sampling (CIS) approach to speech processor design. Within-subject comparisons of such processors with the compressed analog (CA) approach of the clinical Ineraid device are reviewed, and ongoing similar comparisons with the clinical Nucleus spectral peak (SPEAK) strategy are outlined. Correlations between chronic performance levels with clinical CA processors and initial performance levels with CIS, data on further improvements in performance with chronic use of CIS, and instances of substantial benefit from custom fitting of CIS parameters are presented as examples of findings with immediate clinical implications. New studies are described, involving the measurement of intracochlear evoked potentials in response to cochlear implant stimulation, and the integration of such work with computer modeling studies.

Cochlear Implants↗
PubMed1996

Respiratory issues in aeromedical patient transport.

Respiratory considerations in aeromedically evacuated patients are the cornerstone of safe, successful transport. Maintenance of the ABCs and ongoing resuscitation including pulmonary/ventilator stabilization and management en route are paramount. All of these goals are predicated on a well-developed understanding of hypobaric pulmonary physiology and hypobaric effects on medical devices, a solid grasp of the inherent limits of an aeromedical environment, and the resolute accomplishment of both initial and follow-up team member training.

Air Ambulances↗
PubMed1994

Cervical spine nerve root compression. An analysis of neuroforaminal pressures with varying head and arm positions.

STUDY DESIGN: Pressure measurements were taken in the neural foramina of C5, C6, and C7 nerve roots at various positions of the head and ipsilateral arm in eight fresh cadavers. OBJECTIVES: The purpose of the study was to correlate clinical signs and symptoms with pressures generated in the neural foramen of patients with cervical radiculopathy. SUMMARY OF BACKGROUND DATA: The reliability of the clinical signs used to diagnose cervical disc herniations has remained controversial. Previous studies have shown the active relationship of the cord and nerve roots to the various movements of the spine. METHODS: A standard anterior approach was made to the cervical spine and the C5-C7 roots identified. A balloon catheter, attached to a pressure transducer and monitor, was inserted in the neural foramen. The head was then taken through varying degrees of flexion and extension in combination with the arm neutral or abducted. RESULTS: Increasing neck extension led to significant pressure changes at each root tested. With the movement of the arm from the neutral to abducted position, the pressure was significantly relieved. The results with neck flexion were variable. CONCLUSIONS: The significance of this study is that it offers an explanation for the clinical observation of increasing radicular symptoms with neck extension and relief of these symptoms with the shoulder abduction relief maneuver in the setting of a cervical radiculopathy.

Adult↗
PubMed1994

Perilymph pressure during hypobaric conditions--cochlear aqueduct obstructed.

Nine cats with the cochlear aqueduct surgically blocked were anaesthetised, put in a pressure chamber, and stepwise exposed to hypobaric pressure, each of the two steps lasting 5 min. The chamber pressure was reduced to -5 and -7 kPa. Concluding the experiment the cats were observed for 5 min after restoration of atmospheric pressure. The perilymph, tympanic cavity, cerebrospinal fluid, central venous, arterial and surrounding chamber pressures were continuously recorded. Reduced chamber pressure caused relative overpressure within the tympanic cavity, thereby inducing pressure gradients between the chamber, the tympanic cavity, the labyrinth and the cerebrospinal fluid and vascular pressures respectively. Our results demonstrate that hypobaric effects on the labyrinth are mediated via pressure changes in the tympanic cavity and not by systemic, vascular or cerebrospinal fluid influence. Substantial perilymph overpressure lasted throughout the hypobaric conditions. The magnitude and the duration of this overpressure were influenced by the patency of the Eustachian tube whereas the rate of the pressure change in the chamber was of little importance. As atmospheric pressure was restored in the chamber the overpressure in the labyrinth was reversed to underpressure--relative to pre-experimental conditions.

Animals↗
PubMed1992

The inositol phosphate pathway as a mediator in the proliferative response of rat calvarial bone cells to cyclical biaxial mechanical strain.

Isolated newborn rat calvarial bone cells grown in monolayer on polyurethane membranes in specially constructed culture chambers and subjected to a cyclical biaxial mechanical strain of 0.17% at a frequency of 1 Hz for 30 min demonstrated a 16% increase in DNA synthesis during the subsequent 24 h. The metabolites of the inositol phosphate pathway, shown to be an important second messenger in many cell types, were shown to be elevated using high-performance liquid chromatography to separate and quantitate the various inositol polyphosphates. Inositol 1,4,5-trisphosphate, inositol 1,4-bisphosphate, and inositol 1,3,4,5-tetrakisphosphate reached peak accumulations after 20 s of mechanical strain. Inositol 1,3,4-trisphosphate reached a peak accumulation after 2 min, and inositol 1,2,3,4,5,6 phosphate reached a peak accumulation after 60 min of mechanical strain. Neomycin, an inhibitor of phospholipase C, a membrane-bound enzyme that hydrolyzes phosphatidyl inositol 4,5-bisphosphate to start the inositol phosphate cascade, completely inhibited accumulation of the above inositol phosphates during mechanical straining of the bone cells. Neomycin also completely abolished the increase in DNA synthesis that was seen after a mechanical strain of 0.17%. It is concluded from this study that the inositol phosphate pathway is activated by mechanical strain in bone cells and that this pathway is an important and primary mediator in the transduction of mechanical strain into cellular proliferation in these cells.

Analysis of Variance↗
PubMed1992

Pressure transfer between the perilymph and the cerebrospinal fluid compartments in cats.

This is a review of our studies of the labyrinthine fluid pressure in cats subjected to pressure changes in the middle ear (implosive routes) and the cerebrospinal fluid compartment (explosive routes) as well as to changes in vascular and ambient pressures. The perilymph, cerebrospinal fluid (CSF), middle ear, venous and arterial pressures were measured with the cochlear aqueduct (CA) patent as well as surgically blocked. Experiments on explosive pressure changes revealed that the perilymph pressure was regulated by the CSF in case of CA patency. The CSF influence was dominant enough to obscure any direct effect on the labyrinth from other sources. With the CA obstructed the CSF influence on the labyrinth was apparently mainly via the endolymphatic sac and duct although limited and much delayed. Systemic arterial pressure changes had a pronounced influence on the perilymph pressure, but this effect was revealed only when the CSF influence was reduced by CA obstruction. Experiments on implosive and ambient pressure changes suggested that there was no fundamental difference in the perilymph response to equivalent levels of implosive versus hypobaric pressure. Three factors determined the effect of implosive and hypobaric pressure: the patency of the CA, the rate of the pressure change, and the eustachian tube function.

Air Pressure↗
PubMed1991

Concentration-dependent regulatory effects of prostaglandin E1 on human neutrophil function in vitro.

Prostaglandin E1 (PGE1) has recently been used clinically as a purported modulator of activated neutrophils in certain forms of the adult respiratory distress syndrome (ARDS). We now report that PGE1 does not have a uniform inhibitory effect upon human neutrophil functions in vitro. Cells were first pretreated with PGE1 followed by incubation with either N-formyl-methionyl-leucyl-phenylalanine (FMLP), phorbol myristate acetate (PMA), or C5a. Lysosomal enzyme release (myeloperoxidase, lysozyme), superoxide anion generation, and chemotaxis were then quantitated. PGE1 alone lacked any appreciable effect on these neutrophil functions. However, neutrophils pretreated with PGE1 (50 to 100 microM) followed by stimulation with FMLP (50 nM) showed as much as 40% inhibition of lysosomal enzyme release compared with control values (p less than 0.0005). In contrast, 0.1 nM to 1 microM PGE1 enhanced FMLP-stimulated enzyme release as much as 50% above baseline control values (p less than 0.05). Preincubation with 0.1 nM PGE1 followed by stimulation with variable doses of FMLP also resulted in enhancement of lysosomal enzyme release by as much as 187 +/- 3% of control values. The enhancing but not inhibitory effects of PGE1 were reversible with serial washing of the neutrophil preparations. Enhancement of enzyme release was not observed when either PMA or C5a was used as a stimulus after PGE1 pretreatment. However, cells pretreated with PGE1 (50 to 100 microM) and subsequently stimulated with C5a showed as much as 40% inhibition of lysosomal enzyme release. Preincubation of neutrophils with PGE1 (1 microM) resulted in a slight (15%) enhancement of chemotaxis to FMLP, but it had no significant effect on C5a-induced chemotaxis.(ABSTRACT TRUNCATED AT 250 WORDS)

Alprostadil↗
PubMed1991

Disaster management. Organizations and academic perspective.

The world has to cope with the results of an increasing number of disasters. If the planning and preparation for these disasters are to be effective, then national and international organizations are necessary to integrate the sources of advice and relief. Studies of disaster management have consistently highlighted coordination of resources as an essential element of effective response. These organizations, both governmental and voluntary, aim to do just that, and awareness of them and their work will add support.

Aircraft↗
PubMed1990

Ultrasound guidance improves the success rate of internal jugular vein cannulation. A prospective, randomized trial.

STUDY OBJECTIVE: To compare conventional versus ultrasound-guided internal jugular vein cannulation techniques. DESIGN: Patients were randomly assigned to receive either conventional or two-dimensional ultrasound-guided internal jugular vein cannulation. Patients who could not be cannulated with five or fewer passes by either technique, were crossed over to the other technique. SETTING: Clinical research unit in a tertiary care center. PATIENTS: All consecutive patients who required urgent or urgent-elective internal jugular vein cannulation during the study period. INTERVENTIONS: The two-dimensional ultrasound transducer imaged all cannulation attempts. For patients randomized to ultrasound guidance, the operator viewed two-dimensional ultrasound images, and received verbal guidance from the ultrasound technician. For patients randomized to the conventional arm, two-dimensional ultrasound images were recorded without visual or verbal feedback. MEASUREMENTS AND MAIN RESULTS: Two-dimensional ultrasound was significantly better than conventional guidance in reducing the number of failed site cannulations from 6/17 (35 percent), to 0/12 (0 percent), p less than 0.05. Two-dimensional ultrasound also reduced the mean number of passes required to cannulate the vein from 3.12 to 1.75 (p less than .05), and was also successful in six/six (100) of patients who failed cannulation by conventional means (p less than 0.05). CONCLUSIONS: Intensivists can increase successful internal jugular vein cannulation using ultrasound guidance. Two-dimensional ultrasound should be considered for patients difficult to cannulate or those at high risk of cannulation complications.

Catheterization, Central Venous↗