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Biomedical subjects

B J Stenson

Publications and source records attributed to B J Stenson.

13 recordsLinked to original sources
PubMed2006

Non-invasive measurement of reduced ventilation:perfusion ratio and shunt in infants with bronchopulmonary dysplasia: a physiological definition of the disease.

BACKGROUND: An objective definition of bronchopulmonary dysplasia (BPD) is required to interpret trial outcomes and provide a baseline for prognostic studies. Current definitions do not quantify disease severity. The cardinal measures of impaired gas exchange are a reduced ventilation:perfusion ratio (V(A):Q) and increased right to left shunt. These can be determined non-invasively by plotting arterial oxygen saturation (Spo(2)) against inspired oxygen pressure (PIo(2)). AIMS: To describe the reduced V(A):Q and shunt in infants with BPD and evaluate these as graded measures of pulmonary dysfunction. METHODS: 21 preterm infants with BPD were studied. PIo(2) was changed stepwise to vary Spo(2) between 86% and 94%. Pairs of PIo(2) and Spo(2) data points for each infant were plotted and analysed to derive reduced V(A):Q ratio and shunt. RESULTS: In every infant, the Spo(2) versus PIo(2) curve was shifted to the right of the normal because of a reduced V(A):Q. The mean (SD) shift was 16.5 (4.7) kPa (normal 6 kPa). Varying degrees of shunt were also present, but these were less important in determining Spo(2) within the studied range. The degree of shift was strongly predictive of the PIo(2) required to achieve any Spo(2) within the range 86-94% (R(2)>0.9), permitting shift and V(A):Q to be determined from a single pair of PIo(2) and SpO(2) values in this range. CONCLUSIONS: The predominant gas exchange impairment in BPD is a reduced V(A):Q, described by the right shift of the Spo(2) versus PIo(2) relationship. This provides a simpler method for defining BPD, which can grade disease severity.

Bronchopulmonary Dysplasia↗
PubMed2005

Effect of partial liquid ventilation and nebulized perfluorocarbon on CT lung density distribution: randomized controlled study of experimental lung injury.

BACKGROUND: Perfluorocarbon (PFC) liquid can improve gas exchange in acute lung injury. How PFC aerosol is distributed in the lung is unknown. METHODS: We induced lung injury in rabbits with saline lavage, followed by mechanical ventilation in the supine position. The animals were divided into three groups: a control group, a group treated with partial liquid ventilation and a group given nebulized perfluorocarbon (PF 5080). We made CT image slices of the excised lungs. In the apical, middle and caudal slices we defined three regions of interest, from anterior to posterior, and noted the mean attenuation of each area. We also studied two rabbits which had not received lung injury or mechanical ventilation. RESULTS: Group means were different between the normal rabbits and all three study groups. There was a difference between the control and partial liquid ventilation groups, and between the partial liquid ventilation and nebulized groups, but no difference between the nebulized and control groups. Within each treatment group, there was no regional difference in the distribution of density. CONCLUSIONS: PF 5080 is not deposited in large amounts by aerosol. Less PFC was found in the lungs after partial liquid ventilation than expected. Within treatment groups, lung densities indicate less gravitational and regional differences than found in other studies.

Animals↗
PubMed2004

Neonatal research: the parental perspective.

OBJECTIVES: To investigate the recollections of parents consenting for their infants to be research subjects and determine their views about the need for consent. SUBJECTS: Parents of 154 sick newborn infants enrolled in a randomised trial in the early neonatal period. All parents had given written consent and received printed information. METHODS: A questionnaire and accompanying letter was sent to the parental home 18 months later. Non-responders were sent a further questionnaire and letter. RESULTS: Response rate was 64% (99/154). Some respondents (12%) did not remember being asked to consent to their baby joining a study, and a further 6% were unsure. Most of the respondents (79%) were happy, 13% neutral, and 8% unhappy with their decision to give consent. None felt heavy pressure to agree. Entering the trial caused 24% of respondents to feel more anxious, 56% neutral, and 20% less anxious about their baby. Most of the respondents (83%) would be unhappy to forgo the consent process for trials passed by the institutional ethics committee. CONCLUSIONS: A significant proportion of parents who give written consent for a trial in the early neonatal period do not later remember having done so. Parents who have had experience of neonatal research would be unhappy for their baby to be enrolled in a study that had ethics committee approval without their consent being obtained.

Attitude to Health↗
PubMed2004

Preterm meconium staining of the amniotic fluid: associated findings and risk of adverse clinical outcome.

BACKGROUND: The incidence of preterm meconium staining of the amniotic fluid (MSAF) is uncertain. It may be an indicator of possible listeriosis. It is unclear how great this risk is or whether preterm MSAF is a risk factor for adverse neonatal outcome. OBJECTIVE: To investigate the incidence of preterm MSAF, the incidence of associated maternal and neonatal infection, and the outcomes of the infants at discharge. DESIGN: Retrospective case-control study. METHODS: Infants < 33 weeks gestation with preterm MSAF born in the Simpson Memorial Maternity Pavilion, Edinburgh between 1 January 1994 and 2 January 2001 were matched with the next infant of the same sex and gestation with clear liquor. Maternal and infant characteristics, culture results, placental histology, and clinical outcomes were compared. RESULTS: Preterm MSAF was observed in 45/1054 (4.3%) infants below 33 weeks gestation. No maternal or infant listeriosis was identified in cases or controls. There was no significant difference in birth weight, Apgar score, or first pH between cases and controls. Preterm MSAF was associated with prolonged rupture of the membranes (odds ratio (OR) 3.34, 95% confidence interval (CI) 1.07 to 10.49), but not maternal hypertension, sepsis, or chorioamnionitis. Severe (grade 3/4) intraventricular haemorrhage was significantly more common in infants with preterm MSAF (OR 2.03, 95% CI 1.62 to 2.53). There was no significant difference in mortality. Early onset sepsis was observed in two cases and three controls. CONCLUSIONS: Preterm meconium staining of the amniotic fluid may be associated with increased risk of intraventricular haemorrhage. It does not appear to be a useful indicator of listeriosis.

Amniotic Fluid↗
PubMed2002

As time goes by.

The timing of birth-related events may influence neonatal outcome and is often pivotal in medicolegal cases. This prospective observational study determined the variation in displayed time on timepieces in a regional maternity unit which could result in inaccuracies of time documentation. The mean (95% CI) difference between time displayed and true time was sec (+/- 2 min 4 sec) for delivery room clocks and +1 m 8 s (+/- 7 m 12 s) for resuscitation room clocks. The maximum discrepancy between delivery room and resuscitation room clocks was 7 m 52 s. The abilities of staff to estimate the duration of time passed was also assessed. The mean (95% CI) five-minute estimate was 4 m 52 s (+/- 3 m 12 s). These disparities could have considerable medicolegal significance, and should be taken into consideration in risk management studies. Maternity units should move towards synchronising all timepieces. Meanwhile, statements about the precise timing of events should be regarded with suspicion.

Delivery Rooms↗
PubMed2000

Randomised comparison of partial liquid ventilation, nebulised perfluorocarbon, porcine surfactant, artificial surfactant, and combined treatments on oxygenation, lung mechanics, and survival in rabbits after saline lung lavage.

OBJECTIVE: To compare gas exchange, lung mechanics, and survival to 12 h in surfactant-depleted lung-injured rabbits, treated with partial liquid ventilation (PLV) with perfluorocarbon, nebulised perfluorocarbon, and porcine or artificial surfactant. DESIGN: Prospective randomised controlled study. SETTING: Animal laboratory, University of Edinburgh, UK. SUBJECTS: Eighty-two adult female New Zealand white rabbits with surfactant deficiency and acute lung injury induced by repeated saline lavage. INTERVENTIONS: Animals were randomised to one of seven treatments: (a) control (n = 20); (b) PLV with perfluorocarbon PF 5080 (n = 12); (c) nebulised PF 5080 (n = 10); (d) artificial surfactant (n = 10); (e) porcine surfactant (n = 10); (f) artificial surfactant+PLV (n = 10); (g) porcine surfactant+PLV (n = 10). MEASUREMENTS AND MAIN RESULTS: Arterial blood gases and dynamic compliance (Cdyn) were measured hourly until 12 h. Oxygenation was improved by PLV, porcine surfactant, porcine surfactant+PLV and artificial surfactant+PLV. Cdyn improved after treatment with PLV, porcine surfactant and PLV+porcine surfactant. Survival was greater with PLV and artificial surfactant+PLV. Neither nebulised PF 5080 nor artificial surfactant had a detectable effect. CONCLUSIONS: PLV, porcine surfactant and combinations of surfactant with PLV improved oxygenation, Cdyn and survival, but none was clearly superior to the others.

Administration, Inhalation↗
PubMed2000

Measurement of interleukin 10 in bronchoalveolar lavage from preterm ventilated infants.

BACKGROUND: Interleukin 10 (IL-10) is a cytokine that downregulates inflammation, in part by reducing the production of the proinflammatory cytokines IL-1beta and IL-8. It has been suggested that an inability to produce IL-10 might predispose preterm infants to develop chronic lung disease. AIM: To measure IL-10, IL-1beta, and IL-8 in bronchoalveolar lavage fluid from ventilated preterm infants in a prospective cohort study. PATIENTS: 17 consecutive newborn infants < or = 29 weeks' gestational age (median, 25; 9 boys) who were ventilated from birth underwent daily bronchoalveolar lavage sampling. RESULTS: 102 samples were collected, of which 57 contained IL-10 in amounts that were comparable with those found previously in ventilated term infants with respiratory failure. Chronic lung disease developed in 9 of the 11 survivors and all 9 infants had produced IL-10. IL-1beta and IL-8 were detected in nearly all samples and were raised throughout the course of sample collection. CONCLUSION: IL-10 is readily detectable in early bronchoalveolar lavage samples from ventilated preterm infants, although it remains unclear whether this cytokine has any influence on the development of chronic lung disease.

Biomarkers↗
PubMed1998

Randomised controlled trial of respiratory system compliance measurements in mechanically ventilated neonates.

AIM: To determine whether outcomes of neonatal mechanical ventilation could be improved by regular pulmonary function testing. METHODS: Two hundred and forty five neonates, without immediately life threatening congenital malformations, were mechanically ventilated in the newborn period. Infants were randomly allocated to conventional clinical management (control group) or conventional management supplemented by regular measurements of static respiratory system compliance, using the single breath technique, with standardised management advice based on the results. RESULTS: Fifty five (45%) infants in each group experienced one or more adverse outcomes. The median (quartile) durations of ventilation and oxygen supplementation were 5 (2-12) and 6 (2-34) days for the control group, and 4 (2-9) and 6 (3-36) days for the experimental group (not significant). On post-hoc secondary analysis, control group survivors were ventilated for 1269 days with a median (quartile) of 5 (2-13) days, and experimental group survivors were ventilated for 775 days with a median (quartile) duration of 3 (2-8) days (p = 0.03). CONCLUSIONS: Although primary analysis did not show any substantial benefit associated with regular measurement of static respiratory system compliance, this may reflect a type II error, and a moderate benefit has not been excluded. Larger studies are required to establish the value of on-line monitoring techniques now available with neonatal ventilators.

Female↗
PubMed1998

Influence of erythromycin on establishment of feeding in preterm infants: observations from a randomised controlled trial.

AIM: To determine the effect of erythromycin on the establishment of enteral feeding in ventilated infants < 31 weeks gestation. METHODS: Erythromycin was randomly allocated as an antimicrobial treatment for the first 7 days of life in 76 infants: 35 received erythromycin and 41 acted as controls. Feed toleration, time taken to establish full enteral feeding, vomiting, prescription of glycerine suppositories and occurrence of necrotising enterocolitis were recorded. RESULTS: There were no significant differences between the groups for any of the outcomes. The infants treated with erythromycin reached full feeding at a median (quartile) age of 8 (5-12) days compared with 9 (6-14) days for controls. CONCLUSIONS: Intravenous erythromycin in antimicrobial doses is unlikely to benefit the introduction of feeding in preterm infants.

Chi-Square Distribution↗
PubMed1995

Reliability of clinical assessments of respiratory system compliance (Crs) made by junior doctors.

OBJECTIVE: To assess the reliability of estimates of static respiratory system compliance (Crs) made by junior hospital doctors caring for ventilated newborn infants. DESIGN: A prospective comparison of junior doctors' estimates of Crs to the Crs measured immediately afterwards. SETTING: A regional neonatal intensive care nursery in Edinburgh, Scotland. PATIENTS: 46 ventilated newborn infants. MEASUREMENTS AND RESULTS: Crs was estimated by three grades of junior doctor (Senior House Officer, Registrar and Research Fellow) using two different methods, (i) based on visual assessment of tidal volume in relation to inflation pressure (optical Crs) and (ii) directly using a visual analogue scale (analogue Crs). The Crs was then measured immediately afterwards using the single breath passive expiratory flow technique. The differences between the estimates and the measurements were calculated for each grade of observer and plotted against the corresponding measurements. The relationship between estimates and measurements was also expressed in terms of the coefficients of determination r2 calculated by least squares regression. With both methods of estimation observers tended to overestimate the Crs of infants with lower measured Crs and underestimate that of infants with higher measured Crs with many estimates differing from the measurements by more than 50%. Values of r2 ranged from 0.086 to 0.481 indicating a weak relationship between the estimates and the measurements. CONCLUSIONS: Junior doctors' estimates of Crs were unreliable and did not represent a useful method of assessing respiratory function. The clinical use of compliance measurements merits wider evaluation.

Humans↗
PubMed1995

Life-threatening inadvertent positive end-expiratory pressure.

Inadvertent positive end-expiratory pressure (PEEP) is a potential cause of lung overdistension and impaired gas exchange in ventilated infants. It can be extremely difficult to diagnose clinically and if unrecognized can be life-threatening. Measurement of lung function can lead to the recognition of inadvertent PEEP, allowing appropriate ventilator adjustment with immediate substantial improvement in clinical state. Lung function measurements can help to optimize ventilation and may improve clinical outcome.

Humans↗
PubMed1994

Static respiratory compliance in the newborn. III: Early changes after exogenous surfactant treatment.

Static respiratory system compliance (Crs) was measured by a single breath passive expiratory flow technique in 73 newborn infants treated with exogenous surfactant. The first 39 received Curosurf, a natural porcine surfactant. The other 34 received Exosurf Neonatal, a synthetic surfactant. All had a diagnosis of respiratory distress syndrome with an arterial/alveolar oxygen ratio < 0.22. Static Crs and arterial blood gases were measured shortly before, and at three and 12 hours after the first dose of surfactant. In 32 infants treated with Curosurf with initial static Crs < 1.8 ml/cm H2O/m body length, which is consistent with surfactant deficiency, static Crs improved by 18% at three hours and by 39% at 12 hours along with a median reduction in fractional inspired oxygen (FIO2) at three hours by 0.32. In 26 infants treated with Exosurf with initial Crs < 1.8 ml/cm H2O/m, Crs did not improve three and 12 hours after treatment and oxygenation improved less than after Curosurf, with a median reduction in FIO2 at three hours of 0.11. Fifteen of the 73 (21%) infants had initial static Crs of > or = 1.8 ml/cm H2O/m, not consistent with surfactant deficiency. Thirteen of these 15 infants showed a fall in static Crs after surfactant treatment, raising the question whether exogenous surfactant did them more harm than good. Initial static Crs and surfactant type both appear to determine the early response to the first dose of surfactant. Only a considerably larger, randomised study can show which surfactant is more effective in reducing adverse clinical outcome.

Animals↗