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Biomedical subjects

David J Field

Publications and source records attributed to David J Field.

11 recordsLinked to original sources
PubMed2006

United Kingdom collaborative randomized trial of neonatal extracorporeal membrane oxygenation: follow-up to age 7 years.

OBJECTIVE: The UK Collaborative ECMO trial provided an opportunity to describe mortality and morbidity associated with a neonatal ECMO policy compared with conventional management. The improved survival in the ECMO group was not offset by an increase in disability at 4 years, but the children were too young to assess educational and other longer-term impacts. The objective of this study was to assess the longer-term impact of these policies at age 7 years. METHODS: A psychologist assessed 90 of the 100 children available for follow-up without prior knowledge of treatment allocation. The assessments took place at the children's schools within 3 months of their 7th birthdays. RESULTS: Sixty-eight of 89 (76%) children recorded a cognitive level within the normal range. Learning problems were similar in the 2 groups, and there were notable difficulties with spatial and processing tasks. A higher respiratory morbidity and increased risk of behavioral problems among children treated conventionally persisted. Progressive sensorineural hearing loss was found in both groups. CONCLUSIONS: The underlying disease processes appear to be the major influence on morbidity at 7 years. The beneficial influence of an ECMO policy is still present at 7 years.

Child↗
PubMed2006

What image properties regulate eye growth?

The growth of the eye, unlike other parts of the body, is not ballistic. It is guided by visual feedback with the eventual aim being optimal focus of the retinal image or emmetropization . It has been shown in animal models that interference with the quality of the retinal image leads to a disruption to the normal growth pattern, resulting in the development of refractive errors and defocused retinal images . While it is clear that retinal images rich in pattern information are needed to control eye growth, it is unclear what particular aspect of image structure is relevant. Retinal images comprise a range of spatial frequencies at different absolute and relative contrasts and in different degrees of spatial alignment. Here we show, by using synthetic images, that it is not the local edge structure produced by relative spatial frequency alignments within an image but rather the spatial frequency composition per se that is used to regulate the growth of the eye. Furthermore, it is the absolute energy at high spatial frequencies regardless of the spectral slope that is most effective. Neither result would be expected from currently accepted ideas of how human observers judge the degree of image "blur" in a scene where both phase alignments and the relative energy distribution across spatial frequency (i.e., spectral slope) are important.

Animals↗
PubMed2005

Cytokine imbalance in infants receiving extracorporeal membrane oxygenation for respiratory failure.

BACKGROUND: It is likely that the imbalance between the pro- and anti-inflammatory cytokines will determine the outcome in infants with severe respiratory failure receiving extracorporeal membrane oxygenation (ECMO). AIMS: We determined if there was an imbalance between pro- and anti-inflammatory cytokines in serial bronchoalveolar lavage (BAL) fluid obtained from survivors and non-survivors of ECMO. METHODS: We therefore measured the cellular changes and the molar ratios of pro-inflammatory and anti-inflammatory cytokines in serial BAL fluid obtained from survivors and non-survivors of ECMO. Fifteen infants surviving ECMO (median age 1 day, range 1-120) and 7 who did not (28 days, range 1-402) were studied. RESULTS: In the lungs of survivors, the increased proportion of airway neutrophils at presentation decreased with time and was matched by a parallel increase in percent alveolar macrophages as the infants' condition improved. The pro- and anti-inflammatory pulmonary cytokine ratios were static in the survivors. In the non-survivors, the ratio of tumour necrosis factor-alpha (TNF-alpha) against soluble TNF-receptor 1 (sTNF-R1) and soluble TNF receptor 2 (sTNF-R2) was increased at days 2-3 when compared to the survivors, but the molar ratio interleukin-1beta (IL-1beta)/soluble IL-1 receptor antagonist (sIL-1RA) was largely undetectable due to undetectable IL-1beta. CONCLUSIONS: These data suggest that the infants who survive ECMO resolve their pulmonary inflammation and that in non-survivors the ratio of TNF-alpha against its receptor antagonists is increased and is associated with a poor outcome. Furthermore, this group of infants were unable to produce significant concentrations of IL-1beta.

Bronchoalveolar Lavage Fluid↗
PubMed2005

Relationship between antenatal inflammation and antenatal infection identified by detection of microbial genes by polymerase chain reaction.

Although antenatal infection is thought to play an important role in the pathogenesis of preterm labor and neonatal diseases, the exact mechanisms are largely unknown. We sought to clarify the relationship between antenatal infection and intrauterine and neonatal inflammation. Samples were obtained from 41 preterm infants of <33 wk gestation delivered to 36 mothers and analyzed for the presence of 16s ribosomal RNA (16s rRNA) genes using PCR and for the proinflammatory cytokines IL-6 and IL-8. In 16 (44%) mother-baby pairings, at least one sample was found to be positive for the presence of 16s rRNA genes. All but one of the positive samples were from mothers presenting with preterm prelabor rupture of membranes (pPROM) or in spontaneous idiopathic preterm labor. A strong association was found between the presence of 16s rRNA genes and chorioamnionitis and with funisitis. A marked increase in IL-6 and IL-8 was noted in all tissues positive for 16s rRNA genes, including placenta, fetal membranes, cord blood serum, and, where samples were available, in bronchoalveolar lavage fluid (BAL) and in amniotic fluid. Interestingly, gastric fluid was always positive for 16s rRNA genes if any other intrauterine or BAL sample was positive, suggesting that this sample may provide an alternative to amniotic fluid to identify antenatal infection. In conclusion, we have found that microbial genes are particularly prevalent in pPROM and spontaneous preterm labor groups and that their presence is strongly associated with a marked intrauterine inflammatory response.

Amniotic Fluid↗
PubMed2005

How close are we to understanding v1?

A wide variety of papers have reviewed what is known about the function of primary visual cortex. In this review, rather than stating what is known, we attempt to estimate how much is still unknown about V1 function. In particular, we identify five problems with the current view of V1 that stem largely from experimental and theoretical biases, in addition to the contributions of nonlinearities in the cortex that are not well understood. Our purpose is to open the door to new theories, a number of which we describe, along with some proposals for testing them.

Animals↗
PubMed2004

Nitric oxide-still no consensus.

When NO became available for clinical use, it seemed to hold enormous promise for newborn infants with lung disease. With regard to the term and near-term infant, the role of NO seems satisfactorily defined: Near-term and term infants with hypoxic respiratory failure unresponsive to current therapy, excluding infants with diaphragmatic hernia, should have a trial of inhaled nitric oxide. In the preterm infant, the situation is less clear with, as yet, no specific indication identified.

Humans↗
PubMed2004

Sparse coding of sensory inputs.

Several theoretical, computational, and experimental studies suggest that neurons encode sensory information using a small number of active neurons at any given point in time. This strategy, referred to as 'sparse coding', could possibly confer several advantages. First, it allows for increased storage capacity in associative memories; second, it makes the structure in natural signals explicit; third, it represents complex data in a way that is easier to read out at subsequent levels of processing; and fourth, it saves energy. Recent physiological recordings from sensory neurons have indicated that sparse coding could be a ubiquitous strategy employed in several different modalities across different organisms.

Action Potentials↗
PubMed2003

Chronic lung disease of prematurity and intrauterine growth retardation: a population-based study.

OBJECTIVE: To determine the risk of chronic lung disease (CLD) in small for gestational age (SGA) preterm infants in comparison to appropriately grown and large for gestational age (LGA) infants. METHODS: Observational study derived from a geographically defined population (Trent Health Region, United Kingdom). All preterm infants of or=90th centile). Both mortality and CLD rates (using both 28 days' and 36 weeks' postmenstrual age [PMA] definitions) were determined for these groups of infants. RESULTS: Four thousand fifty-one preterm infants <or=32 weeks' gestation were identified. SGA infants showed higher mortality before 28 days' postnatal age and 36 weeks' PMA as compared with reference group infants (odds ratio [OR]: 2.01, 95% confidence interval [CI]: 1.49-2.72; and OR: 2.00, 95% CI: 1.49-2.69), respectively. SGA infants showed a significantly greater risk of developing CLD, both at 28 days' and 36 weeks' PMA as compared with the reference group infants (OR: 1.34, 95% CI: 1.03-1.74; and OR: 1.87, 95% CI: 1.39-2.51), respectively. LGA infants showed a trend toward a reduced incidence of CLD in comparison to the reference group, which was statistically significant for the 36 weeks' definition (OR: 0.76-28 weeks, 95% CI: 0.57-1.01; and OR: 0.55-36 weeks, 95% CI: 0.37-0.81). CONCLUSIONS: Fetal growth seems to influence mortality in general and morbidity, attributable to CLD, in particular in preterm infants. SGA preterm infants are at higher risk of death before 28 days' and 36 weeks' PMA and CLD by both definitions. LGA infants show reduced risk of CLD.

Birth Weight↗
PubMed2002

Maternal morbidity and pregnancy outcome in a cohort of mothers transferred out of perinatal centres during a national census.

OBJECTIVE: To record the maternal morbidity and pregnancy outcome in this cohort. DESIGN: Retrospective data collection from a prospectively defined cohort. SETTING: The 37 largest perinatal centres in the UK. POPULATION: 258 in utero transfers recorded during a three-month census (1/4/99-30/6/99). METHODS: A questionnaire regarding the outcome of each mother was sent to the perinatal centre and receiving hospital. RESULTS: Data were returned on 242/258 (94%) mothers. Fifty-eight percent were transferred out of their perinatal centre in preterm labour and 38% had coexisting disease necessitating early delivery. The median gestational age at transfer was 32 weeks (range 23-41). Sixty-one percent delivered at the receiving hospital; 12% were transferred on to a third hospital and 29% ultimately returned to deliver at the original perinatal centre. Fifty-two percent of mothers received postnatal care in hospitals other than those defined as a major perinatal centre. One mother delivered during transfer and a further nine within one hour of arrival. One mother received intensive care after delivery and later died, a further 7% required high dependency care postnatally. Data were available on 273/333 (82%) babies. The median gestational age at delivery was 34 weeks (range 24-41). Six infants were stillborn and 187/264 (71%) infants were admitted to a neonatal unit. CONCLUSIONS: This study has documented the maternal morbidity, potential risks and pregnancy outcome of a cohort of mothers transferred out of the largest perinatal centres in the UK because of a shortage of neonatal cots. A national standard for the delivery of high risk perinatal services is needed to uphold good clinical practice guidelines in the care of high risk mothers and their infants.

Bed Occupancy↗
PubMed2002

A comparison of clinical variables that predict adverse outcome in term infants with severe respiratory failure randomised to a policy of extracorporeal membrane oxygenation or to conventional neonatal intensive care.

OBJECTIVE: To identify clinical variables predicting adverse outcome in a group of infants with severe respiratory failure who were randomized either to referral for extra-corporeal membrane oxygenation (ECMO) or to conventional neonatal intensive care within the United Kingdom. METHODS: Adverse outcome was defined by death or disability by four years of age. Receiver operator characteristic (ROC) plots were constructed for variables with continuous data and relative risk (RR) with 95% confidence intervals (CI) calculated for binominal data. RESULTS: Of variables measurable at trial entry, congenital diaphragmatic hernia and lower birthweight was also associated with increased mortality and morbidity. Seizures or supplementary oxygen at discharge were markers of disease course, which predicted a poorer outcome amongst survivors. These variables behaved similarly in the two trial groups. Those infants in the ECMO group with an episode of sepsis, established full sucking feeds after 14 days of age or a hospital stay over 30 days were at increased risk of disability. CONCLUSIONS: This study has identified clinical variables that predict adverse outcome for term infants with severe respiratory failure. The results may assist clinicians caring for these babies, when counseling their families and in the development of guidelines for neonatal ECMO.

Children with Disabilities↗