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D O'Hare

Publications and source records attributed to D O'Hare.

At least 37 records · Page 2Linked to original sources
PubMed1998

Cognitive task analyses for decision centred design and training.

This paper presents three case studies of Cognitive Task Analysis (CTA) for defining systems design and training requirements. The approach taken involves a modification of the critical decision method of Klein et al. The authors utilized the revised CDM to obtain information from expert white-water rafting guides, general aviation pilots, and emergency ambulance dispatchers. The information obtained was used to develop multi-media tools for training rafting guides and general aviation pilots, and to redesign the VDU display requirements for the ambulance dispatchers. The examples demonstrate the utility of an approach to CTA that is closely based on relevant theory, and provides guidance to practitioners wishing to apply CTA techniques.

Adolescent↗
PubMed1997

Quantitative spatially resolved measurements of mass transfer through laryngeal cartilage.

The scanning electrochemical microscope (SECM) is a scanned probe microscope that uses the response of a mobile ultramicroelectrode (UME) tip to determine the reactivity, topography, and mass transport characteristics of interfaces with high spatial resolution. SECM strategies for measuring the rates of solute diffusion and convection through samples of cartilage, using amperometric UMEs, are outlined. The methods are used to determine the diffusion coefficients of oxygen and ruthenium(III) hexamine [Ru(NH3)6(3+)] in laryngeal cartilage. The diffusion coefficient of oxygen in cartilage is found to be approximately 50% of that in aqueous electrolyte solution, assuming a partition coefficient of unity for oxygen between cartilage and aqueous solution. In contrast, diffusion of Ru(NH3)6(3+) within the cartilage sample cannot be detected on the SECM timescale, suggesting a diffusion coefficient at least two orders of magnitude lower than that in solution, given a measured partition coefficient for Ru(NH3)6(3+) between cartilage and aqueous solution, Kp = [Ru(NH3)6(3+)]cartilage/[RU(NH3)6(3+)]solution = 3.4 +/- 0.1. Rates of Ru(NH3)6(3+) osmotically driven convective transport across cartilage samples are imaged at high spatial resolution by monitoring the current response of a scanning UME, with an osmotic pressure of approximately 0.75 atm across the slice. A model is outlined that enables the current response to be related to the local flux. By determining the topography of the sample from the current response with no applied osmotic pressure, local transport rates can be correlated with topographical features of the sample surface, at much higher spatial resolution than has previously been achieved.

Animals↗
PubMed1997

Measurements of oxygenation and perfusion in skeletal muscle using multiple microelectrodes.

This paper describes an apparatus to measure tissue oxygenation and perfusion (as measured by the wash-in rate of gaseous hydrogen) simultaneously at multiple points in muscle using needle microelectrodes. The development of suitable electrodes and apparatus is described, as well as the development of the method and its validation. In particular, the potential for tissue damage secondary to electrode insertion, the need for in vivo voltammetric determination of the operating potential and the extent of any electrode-tissue and of electrode-electrode interactions are explored, and are shown to be insufficient in magnitude to affect the technique. Its subsequent use to characterise oxygenation and perfusion in rabbit skeletal muscle at rest is also described. In resting tibialis anterior muscle of the rabbit the mean pO2 was 18 +/- 13.3 mm Hg and the mean perfusion was 4.4 +/- 1.3 ml s-1 100 g-1. There was a heterogeneity in simultaneously-measured values of pO2 and perfusion at different points within muscle, and also a temporal variation at the same site. The spans between the highest and lowest simultaneously-measured values of pO2 in muscle ranged from 14 to 80 mm Hg, and for perfusion, from 1 to 12 mls-1 100 g-1. No significant correlation was evident from histological examination between either pO2 or perfusion and surrounding fibre type or capillary density.

Animals↗
PubMed1997

Cognitive ability determinants of elite pilot performance.

The role of the modern pilot requires a high degree of situational awareness. This involves the ability to search for relevant information, assess opportunities and priorities, and maintain performance under stress. The PC-based WOMBAT test has been designed to measure individual aptitude to cope with such demands. In the first experiment performance on the WOMBAT test was compared with performance on a battery of tests of specific underlying abilities. In the second experiment the performance of elite soaring pilots was compared with that of matched pilot and control groups. The results support the theory that the WOMBAT test measures individual ability to maintain situational awareness and that this ability is found in high levels in elite pilots.

Adult↗
PubMed1996

An audit of aneurysmal subarachnoid haemorrhage: earlier resuscitation and surgery reduces inpatient stay and deaths from rebleeding.

OBJECTIVE: To audit the outcome in patients with subarachnoid haemorrhage (SAH) after a change in management strategy. METHODS: A retrospective analysis of patients with aneurysmal subarachnoid haemorrhage over a 20 month period (phase 1) was followed by a prospective analysis of patients presenting during the next 20 months (phase 2) in which a protocol driven management regime of immediate intravenous fluid resuscitation and earlier surgery was pursued. Patients in this phase were grouped into those receiving early (within four days of subarachnoid haemorrhage) and late (after four days of subarachnoid haemorrhage) surgery. In phase 1, 75 out of a total of 92 patients underwent surgery on (median) day 12. From phase 2, 109 patients out of a total of 129 underwent surgery on (median) day 4, 58 of which had their surgery within 4 days of the subarachnoid haemorrhage. Patients in each phase/group were well matched for demographic features, site of aneurysm, and severity of subarachnoid haemorrhage. RESULTS: The surgical morbidity and mortality were no different in the two phases (P < 0.92; chi2 test). The management outcomes in the two phases of the study were also no different (P < 0.52). However, there was a significant reduction in the rebleed rate in patients undergoing surgery within four days of the subarachnoid haemorrhage in phase 2 (P < 0.0001) with an associated trend towards reduced incidence of postoperative ischaemia (P = 0.06) and mortality (P = 0.11). Operating earlier in phase 2 of the trial resulted in a lower total hospital inpatient stay of 15.8 (95% CI 13.1-18.5) days for survivors compared with 25.7 (95% CI 21.6-29.8) days in the late group (P < 0.00001; t test). CONCLUSIONS: surgical morbidity and mortality seemed independent of the timing of aneurysm surgery. Early surgery within four days was associated with a highly significant reduction in rebleed rate, and in the duration of total hospital inpatient stay.

Adult↗
PubMed1996

Myocardial tissue perfusion determined by particulate and diffusible tracers during ischaemia: what is measured?

OBJECTIVE: Myocardial perfusion can be determined by many techniques which can be broadly divided into those employing particulate tracers and those employing diffusible tracers. The most commonly used particulate tracer is radioactive microspheres. However, as with other particulate tracers, they only determine convective transport from pre-capillary arterioles. If convective transport is the limiting factor in solute exchange, then particulate tracers will give comparable measurements to diffusible tracer techniques. However, if solute transport becomes diffusion-limited or alternative pathways of convective transport become more important, which may occur during regional ischaemia, perfusion visualised with clearance techniques using diffusible tracers may be greater than that determined with particulate tracers. This study set out to investigate this possibility in the rabbit myocardium under normal and ischaemic conditions. METHODS: A pentobarbitone-anaesthetised rabbit model of regional ischaemia was used. Ischaemia of the apical region was induced by ligation of the large left ventricular branch of the circumflex artery. Tissue perfusion was determined by radioactive microspheres (n = 5) and the clearance of hydrogen, which was detected voltammetrically by platinum microelectrodes (n = 5). Measurements were made prior to and following coronary ligation and the ischaemic region was demarcated using the particulate tracer monastral blue. The exchange of diffusible solutes was visualised using digital fluorescence microscopy on histological sections of tissue following systemic administration of the fluorophore Evans blue labelled albumin (n = 4). RESULTS: Coronary ligation produced an ischaemic zone occupying 50 +/- 13% of the left ventricle. In ischaemic tissue, flow determined by microspheres fell to 3.9 +/- 4.1% of its pre-ligation value, but solute exchange fell only to 22 +/- 10% (adjusted for changes in the partition coefficient of H2 during ischaemia, P < 0.05). Perfusion measured by microspheres and hydrogen clearance was unchanged in the non-ischaemic area during coronary ligation. There was preferential uptake of Evans blue albumin towards the endocardial surface in the ischaemic region and areas of local uptake through the ventricular wall, which were possibly associated with vessels. CONCLUSION: This work demonstrates that under normal physiological conditions nutrient supply is determined by pre-capillary delivery. However, during ischaemia diffusive transport plays an increasingly important role. The alternative pathways for solute exchange are likely to have an important influence on the rate and extent of myocardial necrosis during coronary occlusion.

Animals↗
PubMed1995

Dye laser treatment of port-wine stains: comparison of the continuous-wave dye laser with a robotized scanning device and the pulsed dye laser.

BACKGROUND: Despite good results in the treatment of most port-wine stains (PWS) with continuous-wave visible-light lasers, light PWS and those in certain locations respond less favorably and have a higher risk of scarring. Robotized scanning devices such as the Hexascan device have been developed for continuous-wave laser sources to produce greater target specificity, to increase reproducibility of results, and to decrease the incidence of adverse effects. OBJECTIVE: The purpose of this study was to compare the effects of the same wavelength of light (585 nm) on test sites within PWS with the flashlamp-pumped pulsed dye laser and a continuous-wave tunable dye laser scanned through a Hexascan robotized scanning device. METHODS: Two adjacent, noncontiguous sites within PWS were treated in 29 patients, one site with the flashlamp-pumped pulsed dye laser and the other with an argon-pumped continuous-wave tunable dye laser affixed to a Hexascan device. RESULTS: Twenty-eight patients completed the study. The pulsed dye laser was found to be superior to the continuous-wave dye laser with the Hexascan device in 45% of patients, whereas the continuous-wave tunable dye laser with the Hexascan device was considered superior in 15%. There was no difference in the remaining 40%. Undesirable side effects were infrequent with both treatments. There was no significant difference in hypopigmentation or atrophic and hypertrophic scarring, but hyperpigmentation was more frequent with the continuous-wave dye laser with the Hexascan device. CONCLUSION: Both the pulsed dye laser and continuous tunable-wave dye laser with the Hexascan device produce slight lightening after one treatment. The pulsed dye laser produces slightly greater lightening than the continuous-wave tunable dye laser with the Hexascan device 6 weeks after treatment of test areas within PWS in 40% of those treated. It also produced slightly less hypopigmentation and hyperpigmentation.

Adolescent↗
PubMed1995

Cardiac hypertrophy impairs recovery from ischaemia because there is a reduced reactive hyperaemic response.

OBJECTIVE: The aim was to investigate whether impaired coronary flow reserve associated with cardiac hypertrophy could significantly limit the flow debt repayment following short periods of coronary occlusion and exacerbate or prolong episodes of myocardial ischaemia. METHODS: Left ventricular hypertrophy was induced in guinea pigs by aortic constriction and the hearts were isolated six weeks later for Langendorff perfusion. Sham operated animals served as controls. The reactive hyperaemic response was studied following various lengths of occlusion of flow and the extent of aerobic and anaerobic metabolism was assessed in each group. RESULTS: Heart weight/body weight ratio was increased by approximately 25% (P < 0.001) with aortic constriction. The reactive hyperaemic flow response in isolated hearts was impaired by hypertrophy in both magnitude (P < 0.05) and duration. The repayment of flow debt was also significantly reduced, suggesting an inadequate recovery of the myocardium following the occlusion. The total amount of O2 consumed by the heart throughout the duration of hyperaemia was less in hypertrophy than in sham operated controls, suggesting a decrease in aerobic metabolism. Total lactate discharge expressed as a ratio of O2 consumed, which provides an estimation of the degree of anaerobic in relation to aerobic metabolism, was greater in hypertrophy than in sham operated controls. CONCLUSIONS: The hypertrophied heart is more vulnerable to brief periods of ischaemia because of an impaired reactive hyperaemic response which results in delayed metabolic recovery. These abnormalities may contribute to the increased morbidity associated with cardiac hypertrophy.

Animals↗
PubMed1993

Simplified treatment of vascular lesions using the argon laser.

Treatment of mucosal lesions and abnormalities using the carbon dioxide laser is well documented in the dental literature; however, use of the argon laser for the ablation of intraoral vascular malformations is not. This article discusses the argon laser-soft tissue interaction and illustrates by case reports its application in the treatment of vascular lesions.

Adult↗
PubMed1993

Compliance with New York State's do-not-resuscitate law at Memorial Sloan-Kettering Cancer Center. A review of patient deaths.

We reviewed the case records of 141 patients (134 with cancer and seven with acquired immunodeficiency syndrome) who died at Memorial Sloan-Kettering Cancer Center between July 11 and September 19, 1991. Do-not-resuscitate orders had been written on 115 (85.8%) of the patients with cancer and all of the patients with acquired immunodeficiency syndrome. The do-not-resuscitate orders appeared to be valid, in that evidence of informed consent was documented in all but two of the cases. Six additional patients who died had family consent not to resuscitate, although no do-not-resuscitate orders were written. Two other patients died unexpectedly. The remaining 11 patients all received aggressive attempts at resuscitation, which were felt to be medically appropriate in all but two cases. The interval between the do-not-resuscitate order and death was between zero and 60 days, with an average of 8.4 days and a median of 6 days; it exceeded 20 days in 14 cases. We attribute the high degree of compliance with the New York State do-not-resuscitate law observed in this study to an intensive program of consultation and education begun in 1987 by the Ethics Committee of Memorial Sloan-Kettering Cancer Center.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Electrochemical method for direct measurement of oxygen concentration and diffusivity in the intervertebral disc: electrochemical characterization and tissue-sensor interactions.

A method was developed for the in vivo measurement of oxygen concentration and diffusivity in the intervertebral disc using a bare gold cathode. The effects of surface adsorption were quantified using electrochemical methods and it was demonstrated that valid data can be obtained despite interactions between the electrode and the macromolecules of the intervertebral disc. The technique is used to show the dependence of the oxygen transport properties on tissue water content.

Adsorption↗
PubMed1991

Tuberculosis in children 10 years of age and younger: three decades of experience during the chemotherapeutic era.

The 863 patients, aged 10 years and younger, treated at the Children's Chest Clinic of Bellevue Hospital during three decades (1953 through 1981) clearly indicated the success of antituberculosis therapy. There were no deaths from tuberculosis. Early treatment is associated with a reduction in the serious forms of disease, eg, meningitis, miliary disease, and bone infections, and with preventing death. Medication was well tolerated: only 1.1% of the patients had adverse reactions, all of which were reversible. Consistent compliance with medication of only 62% of patients is a challenge to the medical profession. Only 22.5% of mycobacterial cultures were positive. Long-term follow-up of patients was rewarding: seven pregnancies with healthy mothers and babies, and no reactivation of tuberculosis by later infections, even those such as measles or pneumonia. The severity of disease was related largely to patient's age (3 years and younger) and intimacy of contact, the highest rate being when the mother was the contact. The long-term experiences emphasizes the value of early identification, therapeutic compliance, and comprehensive contact, tracing in the future elimination of tuberculosis. Prophylactic therapy and close observation should be considered for contacts, especially those exposed to human immunodeficiency virus infections and addicted to drugs.

Antitubercular Agents↗
PubMed1991

A survey of community (out-of-hospital) sites used in pediatric training.

A survey was completed of US pediatric residency programs about the use of community sites in training. A total of 85% of program directors responded and reported a wide use of the 21 identified survey sites. Further study is needed to determine the appropriate contribution that community sites can make to pediatric training.

Internship and Residency↗
PubMed1990

Pilots' perception of risks and hazards in general aviation.

A sample of licensed pilots completed the Aeronautical Risk Judgment Questionnaire (ARJQ) which was developed to obtain data on pilots' perceptions of their abilities, willingness to take risks, hazard awareness, and judgments of the risks of general aviation. A subset of these subjects was tested on a computerised test of flight decision-making involving a proposed VFR flight in marginal weather conditions. Results from the ARJQ indicate relatively low levels of risk and hazard awareness combined with a generally optimistic self-appraisal of abilities by this sample of general aviation pilots. Younger subjects (under 30) were found to rate the likelihood of being involved in an accident more highly than did older pilots. Experienced pilots obtained higher scores on a measure of "personal invulnerability" from factors commonly associated with accidents. This does not appear to be due simply to overconfidence in their abilities, since it was the younger and less experienced pilots who held the most unrealistically optimistic appraisals of their ability. Pilots who proceeded with the computerised flight rate themselves as having a greater willingness to take risks, and were likely to be younger and have higher total hours than those who rejected the flight. They were also found to have significantly higher scores on the measure of "personal invulnerability." The results are discussed in relation to previous epidemiological findings and possible safety prevention strategies.

Accidents, Aviation↗
PubMed1985

Congenital tuberculosis. Review and diagnostic guidelines.

A review of congenital tuberculosis was prompted by the successful treatment of this disease in a unique patient. She was followed up for 27 years, and gave birth to two normal, uninfected newborns despite calcifications throughout her abdomen and elsewhere. Tuberculosis of the newborn, whether acquired congenitally or postnatally, is preventable. Recommendations for diagnosis of congenital tuberculosis are given. Determination of the mother's tuberculin status or suitable testing should be done early in pregnancy. Endometritis is cited as an unrecognized source of fetal infection.

Abdomen↗