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Biomedical subjects

D Hatch

Publications and source records attributed to D Hatch.

At least 19 recordsLinked to original sources
PubMed2005

Nitrogen budgets for three cropping systems fertilised with cattle manure.

A field plot experiment was set up on a sandy loam soil of SW England in order to determine the efficiency of nitrogen use from different cattle manures. The manure treatments were low and high dry matter cattle slurries and one farmyard manure applied at a target rate of 200 kg total N ha(-1)year(-1), and an untreated control. There were three different cropping systems: ryegrass/clover mixture, maize/rye and maize/bare soil, which were evaluated during 1998/99 and 1999/00. Measurements were made of N losses, N uptake and herbage DM yields. Result showed that manure type had a significant effect on N utilisation only for maize. N balances were negative in maize (approximately -247 to -10 kg N) compared to grass (approximately 5-158 kg N). Agronomic management was more important than manure type in influencing N losses, where soil cultivation appeared to be a key factor when comparing maize and grass systems.

Animals↗
PubMed2001

The influence of endotracheal tube leak on the assessment of respiratory function in ventilated children.

OBJECTIVE: The use of respiratory mechanics to optimise ventilator settings has become more common since the integration of pressure and flow transducers into modern ventilators. However, values of respiratory resistance (R(rs)) and compliance (C(rs)) can be overestimated in the presence of tracheal tube leak and clinical decisions based on these figures would be misinformed. This study aimed to assess the influence of tracheal tube leak on measurements of C(rs), R(rs) and expired tidal volume (V(TE)) in ventilated children in order to establish when such measurements were reliable in this population. DESIGN: Respiratory function was monitored for at least five consecutive hours during which normal medical procedures were performed. The magnitude and variability of tracheal tube leak was assessed during these periods. SETTING: The paediatric and cardiac intensive care units at Great Ormond Street Hospital for Children, NHS Trust, London. PATIENTS: Seventy-five paralysed, fully ventilated infants and children. RESULTS: Ten children had a mean leak greater than 20% (range: 22%-65%). Amongst this group there were wide fluctuations with respect to leak magnitude, V(TE), C(rs) and R(rs). Leaks of less than 20% appeared necessary to obtain reliable measurements of C(rs) and R(rs) and to ensure consistent and adequate ventilation. CONCLUSIONS: Leaks larger than 20% result in inconsistent tidal volume delivery and gross overestimation of C(rs) and R(rs) irrespective of ventilation mode. The magnitude of tracheal tube leak needs to be accurately displayed on all ventilatory equipment to verify reliable measures of respiratory function so that appropriate clinical decisions can be made and ventilatory management optimised.

Adolescent↗
PubMed2001

Use of a novel nitrification inhibitor to reduce nitrous oxide emission from (15)N-labelled dairy slurry injected into soil.

Recent recommendations for environmentally sound use of liquid animal manure often include injection of slurry into soil. Two of the most important undesired side effects, ammonia (NH(3)) volatilisation and odour emissions, are usually significantly reduced by slurry injection. On the other hand, because of the higher amount of nitrogen (N) remaining in soil, the risk of nitrate (NO(3)(-)) leaching and nitrous oxide (N(2)O) emissions is increased. Thus, the reduction of local effects caused by NH(3) deposition, e.g. N enrichment and soil acidification, may be at the cost of large-scale effects such as ozone depletion and global warming as a result of emitted N(2)O. In this context, nitrification inhibitors can contribute significantly to a reduction in NO(3)(-) leaching and N(2)O production. A field experiment was carried out at IGER, North Wyke, which aimed to evaluate the effect of the new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP/ENTEC). For this experiment, (15)N enriched dairy slurry was used and the isotopic label in soil N as well as in N(2)O were studied. After slurry injection into the grassland soil in August 2000, the major emissions of N(2)O occurred during the first ten days. As expected, high N(2)O emission rates and (15)N content of the emissions were concentrated on the slurry injection slots, showing a steep decrease towards the untreated centre-point between slurry injection slots. The nitrification inhibitor DMPP proved to be very efficient in reducing N(2)O emissions. At a rate of 2 kg DMPP ha(-1), the total amount of N(2)O emitted was reduced by 32%, when compared with slurry injection without DMPP. The isotopic label of the emitted N(2)O showed that during the 22-day experimental period, emissions from the slurry N pool were strongly reduced by DMPP from 0.93 kg N(2)O-N ha(-1) (-DMPP) to 0.50 kg N(2)O-N ha(-1) (+DMPP), while only a minor effect on emissions from the soil N pool was observed (0.69 to 0.60 kg N(2)O-N ha(-1); -DMPP, +DMPP, respectively).

Algorithms↗
PubMed2001

The General Medical Council's Performance Procedures: peer review of performance in the workplace.

The General Medical Council procedures to assess the performance of doctors who may be seriously deficient include peer review of the doctor's practice at the workplace and tests of competence and skills. Peer reviews are conducted by three trained assessors, two from the same speciality as the doctor being assessed, with one lay assessor. The doctor completes a portfolio to describe his/her training, experience, the circumstances of practice and self rate his/her competence and familiarity in dealing with the common problems of his/her own discipline. The assessment includes a review of the doctor's medical records; discussion of cases selected from these records; observation of consultations for clinicians, or of relevant activities in non-clinicians; a tour of the doctor's workplace; interviews with at least 12 third parties (five nominated by the doctor); and structured interviews with the doctor. The content and structure of the peer review are designed to assess the doctor against the standards defined in Good Medical Practice, as applied to the doctor's speciality. The assessment methods are based on validated instruments and gather 700-1000 judgements on each doctor. Early experience of the peer review visits has confirmed their feasibility and effectiveness.

Clinical Competence↗
PubMed2001

Gap detection for similar and dissimilar gap markers.

Detection thresholds for temporal gaps between markers of dissimilar frequency are usually elevated with respect to thresholds for gaps between markers of similar frequency. Because gaps between markers of dissimilar frequency represent both a spectrally based perceptual discontinuity as well as a temporal discontinuity, it is not clear what factors underlie the threshold elevation. This study sought to examine the effects of perceptual dissimilarities on gap detection. The first experiment measured gap detection for configurations of narrow-band gap markers comprised of pure tones, frequency-modulated tones, and amplitude-modulated tones. The results showed that gap thresholds for frequency-disparate pure-tone markers were elevated with respect to isofrequency tonal markers, but that perceptual discontinuities between markers restricted to the same frequency region did not uniformly elevate threshold. The second experiment measured gap detection for configurations of markers where the leading and trailing markers could differ along the dimensions of bandwidth, duration, and pitch. The results showed that, in most cases, gap detection deteriorated when the bandwidth of the two markers differed, even when the spectral content of the narrower-band marker was completely subsumed by the spectral content of the wider-band marker. This finding suggests that gap detection is sensitive to spectral dissimilarity between markers in addition to spectral discontinuity. The effects of marker duration depended on the marker bandwidth. Pitch differences across spectrally similar markers had no effect.

Adult↗
PubMed2001

The assessment of poorly performing doctors: the development of the assessment programmes for the General Medical Council's Performance Procedures.

BACKGROUND: Modernization of medical regulation has included the introduction of the Professional Performance Procedures by the UK General Medical Council in 1995. The Council now has the power to assess any registered practitioner whose performance may be seriously deficient, thus calling registration (licensure) into question. Problems arising from ill health or conduct are dealt with under separate programmes. METHODS: This paper describes the development of the assessment programmes within the overall policy framework determined by the Council. Peer review of performance in the workplace (Phase 1) is followed by tests of competence (Phase 2) to reflect the relationship between clinical competence and performance. The theoretical and research basis for the approach are presented, and the relationship between the qualitative methods in Phase 1 and the quantitative methods in Phase 2 explored. CONCLUSIONS: The approach is feasible, has been implemented and has stood legal challenge. The assessors judge and report all the evidence they collect and may not select from it. All their judgements are included and the voice of the lay assessor is preserved. Taken together, the output from both phases forms an important basis for remediation and training should it be required.

Clinical Competence↗
PubMed1998

A comparison of the respiratory effects of sevoflurane and halothane in infants and young children.

BACKGROUND: This study compared the respiratory effects of sevoflurane with those of halothane in anesthetized infants and young children. METHODS: Infants were randomized to receive 1 minimum alveolar concentration (MAC) halothane or sevoflurane in a mixture of nitrous oxide and oxygen. Anesthetic management included the use of a laryngeal mask. Flow, airway pressure, and the end-tidal carbon dioxide pressure (PETCO2) were measured during spontaneous ventilation and airway occlusions. Respiratory inductive plethysmography was used to assess chest wall motion. RESULTS: Measurements were obtained in 30 infants and young children (mean (SD) age, 14.5 (5.9) months), 15 of whom received sevoflurane and 15 received halothane. Some respiratory depression, as indicated by a PETCO2 of 45 mmHg (6 kPa), was present in both groups. Minute ventilation and respiratory frequency were significantly lower during sevoflurane than halothane anesthesia (4.5 compared with 5.4 (1/ m2)/min, and 37.5 compared with 46.7 breaths/min, respectively, P < 0.05). There was no difference in respiratory drive, but the shape of the flow waveform differed according to anesthetic agent, with peak inspiratory flow reached later, and peak expiratory flow reached earlier, in the sevoflurane group. There was also significantly less thoracoabdominal asynchrony during sevoflurane anesthesia. CONCLUSIONS: Minute ventilation and respiratory frequency were lower in infants during 1 MAC sevoflurane in nitrous oxide than during halothane anesthesia. However, these differences may not be clinically relevant at these concentrations, given the modest increase in PETCO2. Differences in parameters of breath timing and shape between sevoflurane and halothane suggest different effects of these anesthetic agents on ventilatory control.

Anesthetics, Inhalation↗
PubMed1998

Validation of respiratory inductive plethysmography using the Qualitative Diagnostic Calibration method in anaesthetized infants.

The aim of this study was to compare tidal volume (VT) derived from the Qualitative Diagnostic Calibration (QDC) method (VT,QDC) with measurements from pneumotachography (VT,PN,T) in anaesthetized infants. Measurements were made during spontaneous (SV) and intermittent positive pressure (IPPV) ventilation, sighs and airway occlusions. The VT,DIF was the difference between VT,QDC and VT,PNT (%VT). The contribution of the ribcage (rc) to VT,QDC (%rc) and the thoracoabdominal phase lag were also derived. Twenty-eight infants, mean (SD) age 14.0 (6.2) months were studied. VT,QDC represented VT,PNT most closely when > or = 20 breaths were analysed. There was close agreement during SV immediately after the calibration period (95% limits of agreement (LA; QDC - PNT) -23, 3.0%). The 95% LA increased to -9.6, 10.2% after 10 min. Accuracy diminished during IPPV (95% LA -38, 31%), and sighs. During airway occlusions, when VT,PNT was zero, the 95% LA were -63, 4.1 mL x kg(-1). Mean phase lag was 36 and 2%, respectively, during SV and IPPV (p<0.05). The %rc appeared to be overestimated, being in excess of 50% in infants under 12 months. The Qualitative Diagnostic Calibration method used to estimate tidal volume in anaesthetized infants was limited by the need to analyse > or = 20 breaths and by a loss of within-subject accuracy if measurement conditions or pattern of breathing changed.

Anesthesia, General↗
PubMed1997

Partial nephrectomy for pediatric renal cell carcinoma: an unusual case presentation.

Nine years after successful treatment of Stage IV neuroblastoma, a 10-year-old white girl was demonstrated to have a complex cystic mass in the upper pole of her solitary right kidney. Partial nephrectomy was performed, disclosing a renal cell carcinoma, predominantly clear cell type. No metastases were detected. Renal cell carcinoma is a rare cause of secondary malignancy. Partial nephrectomy can be used successfully to treat renal cell carcinoma in children.

Carcinoma, Renal Cell↗
PubMed1996

Renal computed tomography with 3-dimensional angiography and simultaneous measurement of plasma contrast clearance reduce the invasiveness and cost of evaluating living renal donor candidates.

Renal computed tomography (CT), 3-dimensional CT angiography (3D-CTA), and simultaneous measurement of glomerular filtration rate (GFR) by x-ray fluorescence determination of plasma contrast clearance (PCC) are alternatives to intravenous urography (IVU), renal arteriography (RA), and 24-hr urine creatinine clearance (CrCl) for evaluation of renal structure and function in living renal donor (LRD) candidates. To determine if CT, 3D-CTA, and PCC provide data comparable to IVU, RA, and CrCl, both methods were used to evaluate 23 LRD candidates. Costs were also compared. Conventional RA identified 19 accessory arteries and one case of medial fibroplasia. Each of these anomalous vessels was recognized on 3D-CTA. Venous anatomy was more clearly delineated on 3D-CTA than the venous phase of conventional RA. CT demonstrated 3 benign cysts and a single, small intraparenchymal calcification in 3 renal units. GFRs measured by PCC and CrCl were 91 +/- 4 and 132 +/- 7 ml/min/1.73m2, respectively (r = 0.64, P < 0.05). Total cost for CT/3D-CTA/PCC was 46% less than that of IVU/RA/CrCl and 40% less than RA/CrCl. CT/3D-CTA/PCC provided reliable structural and functional data at substantially less cost, discomfort, and inconvenience to the living renal donor candidate. As such, CT/3D-CTA/PCC is superior to conventional methods for evaluation of the living renal donor candidate.

Adult↗
PubMed1994

Renal cell carcinoma developing in the pediatric recipient of an adult cadaveric donor kidney.

Renal cell carcinoma is an uncommon renal tumor in children, comprising between 1.8% and 6.3% of all malignant renal tumors of childhood (whereas renal cell carcinoma is the commonest renal tumor in adults). We describe a 15-year-old girl with chronic renal failure secondary to renal dysplasia and branchio-oto-renal syndrome, who received a cadaveric renal transplant at 8 years of age from a 25-year-old male donor. She developed severe chronic rejection 4 years after the transplant. A transplant nephrectomy was performed because of persistent gross hematuria. Histopathology of this graft showed chronic severe rejection and papillary necrosis. A fortuitous finding was a 1.5-cm renal cell carcinoma at one of the poles. We suggest that tumors which occur more commonly in adults and less commonly in children must be considered in children receiving adult organ transplants.

Adolescent↗