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Biomedical subjects

K R Dunster

Publications and source records attributed to K R Dunster.

16 recordsLinked to original sources
PubMed2002

Fate of abstracts published in the proceedings of the first annual Perinatal Society of Australia and New Zealand Congress in 1997.

OBJECTIVES: To examine the fate of research presented at the first annual Perinatal Society of Australia and New Zealand (PSANZ) Congress in 1997, by determining: the rate of publication in peer-reviewed biomedical journals; publication rate by discipline; journals in which work was published; concordance for aims, conclusions, authors and number of study subjects; and time from presentation to publication. METHODS: A MEDLINE search was conducted for any publication in a peer-reviewed journal resulting from a publishable abstract from the proceedings of the first annual PSANZ Congress in 1997. Searching was completed 42 months post-congress. The concordance of aims, conclusions, authors and number of subjects between abstract and published paper was determined. RESULTS: There were 172 publishable abstracts in the proceedings of the PSANZ Congress in 1997, and 78 (45%) were published as 83 articles. Basic sciences had the highest publication rate (67%) and midwifery the lowest (20%). Articles were published in 41 journals, with one-third of the articles in three paediatric journals. There was a match with aims in 75%, and with conclusions in 65%. There were 47/77 with the same number of subjects, 20/77 with more and 10/77 with fewer. There were 22 articles with one author added, 12 had more than one author added, 11 had one author removed and five had more than one author removed. Median time-to-publication was 18 months (interquartile range 9-26 months). CONCLUSIONS: A publication rate of 45% is comparable to other conferences. Basic science and neonatology had the highest publication rates. There were considerable differences between abstract and published article in terms of aims, conclusions, number of subjects and authors.

Australia↗
PubMed2002

Rebreathing potential of infant mattresses and bedcovers.

OBJECTIVE: To establish the CO2 dispersion and retention properties of some mattresses and bed coverings commercially available in Australia. METHODS: Five mattresses were studied in (i) an in vivo model in which an infant's head was covered by a headbox, rebreathing was allowed to occur, and the final steady state CO2 concentration was measured; and (ii) an in vitro model in which 5% CO2 in a headbox was allowed to disperse, and the time taken for the concentration to reach 1% was measured. Five types of bedcover were studied in (i) an in vivo model in which an infant's head was covered by a bedcover and the final steady state CO2 concentration was measured; and (ii) an in vitro model in which 5% CO2 under a bedcover was allowed to disperse, and the time taken for the concentration to reach 1% was measured. RESULTS: The steady state CO2 concentrations ranged from 0.6% to 3.0% for the mattresses (P < 0.05). The time for CO2 to disperse ranged from 5.5 min to 30.4 min (P < 0.05). Steady state CO2 concentrations ranged from 2.5% to 3.6% for the bedcoverings (P > 0.05). The time for CO2 to disperse ranged from 5.4 min to 7.7 min (P > 0.05). CONCLUSIONS: Some commercial cot mattresses and bedcoverings allow high concentrations of CO2 to accumulate in rebreathing environments. Some mattress types studied were more diffusive to CO2, whereas there was no difference between the bedcovers studied. This may have implications for vulnerable infants at risk of sudden infant death syndrome.

Bedding and Linens↗
PubMed2001

An improved survival model of hypoxia/ischaemia in the piglet suitable for neuroprotection studies.

The purpose of this study was to develop a newborn piglet model of hypoxia/ischaemia which would better emulate the clinical situation in the asphyxiated human neonate and produce a consistent degree of histopathological injury following the insult. One-day-old piglets (n=18) were anaesthetised with a mixture of propofol (10 mg/kg/h) and alfentinal (55.5 microg/kg/h) i.v. The piglets were intubated and ventilated. Physiological variables were monitored continuously. Hypoxia was induced by decreasing the inspired oxygen (FiO(2)) to 3-4% and adjusting FiO(2) to maintain the cerebral function monitor peak amplitude at < or =5 microV. The duration of the mild insult was 20 min while the severe insult was 30 min which included 10 min where the blood pressure was allowed to fall below 70% of baseline. Control piglets (n=4 of 18) were subjected to the same protocol except for the hypoxic/ischaemic insult. The piglets were allowed to recover from anaesthesia then euthanased 72 h after the insult. The brains were perfusion-fixed, removed and embedded in paraffin. Coronal sections were stained by haematoxylin/eosin. A blinded observer examined the frontal and parietal cortex, hippocampus, basal ganglia, thalamus and cerebellum for the degree of damage. The total mean histology score for the five areas of the brain for the severe insult was 15.6+/-4.4 (mean +/-S.D., n=7), whereas no damage was seen in either the mild insult (n=4) or control groups. This 'severe damage' model produces a consistent level of damage and will prove useful for examining potential neuroprotective therapies in the neonatal brain.

Animals↗
PubMed2000

Infant autonomic function is altered by maternal smoking during pregnancy.

Sudden infant death syndrome (SIDS) is more prevalent in infants of smokers and may involve subtle alterations in autonomic control mechanisms. Autonomic function can be assessed using blood pressure responses to a passive head-up tilt and power spectral analysis of heart rate variability. This study aimed to determine if maternal smoking altered infants' responses to head-up tilt. Blood pressure and heart rate responses to a passive 70 degrees head-up tilt were compared in infants of smokers and non-smokers at 2-3 days and 3 months of age. There were no significant differences between groups in power spectral indices. At 2-3 days, the systolic pressure response to tilt was significantly different between groups (P<0.01). In infants of smokers, systolic pressure decreased by a mean (S.E.) of 7.7(1.1) mmHg, whereas in control infants it remained unchanged. At 3 months, systolic pressure in infants of smokers remained unchanged but increased in control infants by 6.2(2.1) mmHg (P<0.05). These results indicate that maternal smoking alters autonomically mediated cardiovascular responses in the infant.

Autonomic Nervous System↗
PubMed2000

Cardiac responses to mild hypoxic hypercapnia in newborn babies: no effect of sleep position.

OBJECTIVE: To evaluate whether cardiac responses to a level of hypoxic hypercapnia that may be observed in rebreathing studies are altered with infant sleep position. METHODOLOGY: Eighteen healthy term infants (< 5-days-old) were studied. Heart rate (HR) and HR variability were monitored during air breathing and during 3 min exposure to a mixture of 15% O2/3% CO2 in both the prone and supine positions. Power spectral analysis of HR was performed. RESULTS: Heart rate was the only measured variable to be significantly changed in response to 15% O2/3% CO2. Hypoxic hypercapnia elicited no significant responses in power spectral HR variables. There was no effect of sleeping position on any of the measured variables. CONCLUSIONS: There are no significant differences in cardiac responses to mild hypoxic hypercapnia between sleep positions and power spectral indices of the autonomic control of HR are not altered by sleep position in newborn babies.

Female↗
PubMed2000

The effect of perfluorocarbon vapour on the measurement of respiratory tidal volume during partial liquid ventilation.

During partial liquid ventilation perfluorocarbon vapour is present in the exhaled gases. The volumes of these gases are measured by pneumotachometers. Error in measuring tidal volumes will give erroneous measurement of lung compliance during partial liquid ventilation. We aim to compare measured tidal volumes with and without perfluorocarbon vapour using tidal volumes suitable for use in neonates. Tidal volumes were produced with a 100 ml calibration syringe from 20 to 100 ml and with a calibrated Harvard rodent ventilator from 2.5 to 20 ml. Control tidal volumes were drawn from a humidifier chamber containing water vapour and the PFC tidal volumes were drawn from a humidifier chamber containing water and perfluorocarbon (FC-77) vapour. Tidal volumes were measured by a fixed orifice, target, differential pressure flowmeter (VenTrak) or a hot-wire anenometer (Bear Cub) placed between the calibration syringe or ventilator and the humidifier chamber. All tidal volumes measured with perfluorocarbon vapour were increased compared with control (ANOVA p < 0.001 and post t-test p < 0.0001). Measured tidal volume increased from 7 to 16% with the fixed orifice type flow-meter, and from 35 to 41% with the hot-wire type. In conclusion, perfluorocarbon vapour flowing through pneumotachometers gives falsely high tidal volume measurements. Calculation of lung compliance must take into account the effect of perfluorocarbon vapour on the measurement of tidal volume.

Animals↗
PubMed1999

Anetoderma of prematurity in association with electrocardiographic electrodes.

Anetoderma in premature infants is an uncommon lesion that may be associated with the use of various types of monitoring leads. In 2 infants multiple papules of anetoderma occurred on the forehead in association with the use of gel electrocardiographic electrodes. It is postulated that the cause of these papules was a local hypoxemia caused by pressure from the electrodes. Growth-restricted infants may be particularly predisposed to iatrogenic anetoderma.

Biopsy, Needle↗
PubMed1999

Physiologic variability in the perinatal period. Origins, measurement, and applications.

Variability is inherent in all physiologic signals. This variability provides valuable clinical information or may confound physiologic measurements and the interpretation of results. Both physiologic and nonphysiologic factors may affect variability. Clinicians and researchers need to be aware of physiologic variability and its implications.

Circadian Rhythm↗
PubMed1998

Fetal oxygen saturation during maternal bearing down efforts in the second stage of labor.

Fetal oxygen saturation (FSpO2) was monitored with the Nellcor Puritan Bennett N400/FS14 system during 16 labors to establish whether FSpO2 was influenced by maternal bearing down efforts in the second stage of labor. Fetal SpO2 is reported for 16 fetuses where neonatal outcome was normal. One hour of continuous data was recorded: 30 min prior to the onset of maternal bearing down efforts and the first 30 min of pushing. The hour was divided into six epochs of 10-min duration. Differences between mean FSpO2 for the two 30 min of monitoring and for each epoch were sought using repeated measures analysis of variance (ANOVA). The mean FSpO2 for the total 30 min prior to the onset of pushing was 49% (95% confidence intervals 46.5-50.6%), compared to a mean of 46% (95% confidence intervals 43.6-48.7%) during the first 30 min of pushing [F (1, 2.25), p = 0.14]. There was no significant decline in mean FSpO2 for each epoch. Apgar scores at 5 min were all > 7 and umbilical arterial pH values were > or = 7.20 (n = 12). We concluded that mean FSpO2 recorded prior to the onset of maternal bearing down efforts was not significantly different to mean FSpO2 during pushing, with normal neonatal outcome.

Adult↗
PubMed1998

Fetal oxygen saturation and uterine contractions during labor.

Oxygen availability to the fetus during uterine contractions has not been widely reported. We examined whether fetal oxygen saturation (FSpO2) values and signal quality (SQ) were affected by uterine contractions. An intrauterine pressure catheter and a Nellcor FS14 fetal oxygen saturation sensor (Nellcor Puritan Bennett Inc., Pleasanton, CA) were placed transvaginally during the first stage of 17 labors. Fetal SPO2 and SQ units were recorded on a beat-to-beat basis and 10 sec averages of the data calculated over 25 contractions per patient. Five epochs were determined: (1) 30 sec prior to a contraction; (2) during a contraction; (3) 50 sec following completion of a contraction; (4) noncontraction periods, excluding epochs 1 or 3; and (5) equivocal, that is, overlap of epochs 1-3. Mean FSpO2 was lowest during epoch 3 (45.0) and highest during epoch 2 (47.3%) (p <0.001). This small difference is unlikely to be of any clinical significance, however. Mean signal quality was lowest in epoch 1 (42.8 units) and highest in epoch 4 (48.0 units) (p <0.05), that is, in noncontraction periods. We conclude that FSpO2 and SQ were unaffected by uterine contractions.

Female↗
PubMed1997

Fetal oxygen saturation monitoring in labour: an analysis of 118 cases.

Fetal oxygen saturation (FSpO2) was recorded during labour to determine the relationship between FSpO2 and indicators of fetal well-being, including umbilical blood gases, xanthine (X), hypoxanthine (Hx) and Apgar scores. This is one of the largest reported series of fetal pulse oximetry, with 118 fetuses monitored for over 329 hours. Mean FSpO2 for all cases was 46.9% (SD = 9.1%). There was no correlation between FSpO2 during the last 10 minutes of monitoring and arterial pH, Hx or X. A mean FSpO2 > or = 30% was associated with a 5 minute Apgar score of > or = 7 in the majority of cases. One fetus had a mean FSpO2 < 30% during the final 10 minutes of monitoring and an umbilical arterial pH < 7.20, while there were 10 fetuses with an umbilical arterial pH < 7.20, and mean FSpO2 > or = 30%. As these numbers are small, a larger series is necessary to further characterize the small number of fetuses who are significantly hypoxic.

Adolescent↗
PubMed1996

Human fetal intrapartum oxygen saturation monitoring: agreement between readings from two sensors on the same fetus.

OBJECTIVE: Our purpose was to assess the level of agreement between oxygen saturation values obtained from two identical sensors used on different sides of the face of the same human fetus during labor. STUDY DESIGN: Two identical fetal pulse oximeter sensors were placed on 12 fetuses during uncomplicated labor at < or = 38 weeks' gestation. Oxygen saturation, fetal heart rate, and uterine activity were recorded. The agreement between synchronous values of oxygen saturation was assessed by calculating the mean difference and SD of the difference. The SD of a single sensor was estimated as the SD of the difference divided by the square root of 2. RESULTS: The mean oxygen saturation value returned from one sensor was 49.2% and from the other 49.9%; the mean difference was -0.7%. The SD of the difference was 7.5%, and the 95% limits (+/- 2 SDs of the difference) were -15.5% to 14.1%. The SD from a single sensor was estimated as 5.3%. CONCLUSIONS: There was no clinically significant difference between the oxygen saturation values returned from two identical sensors on the one fetus. The magnitude of the SD from a single sensor must be taken into account when an arbitrary "cutoff" or "action" oxygen saturation value in a clinical setting or trial is defined.

Delivery, Obstetric↗
PubMed1995

Fluctuations in syringe-pump infusions: association with blood pressure variations in infants.

Flow continuity of two brands of syringe pumps and four brands of syringes was studied as a possible cause of hemodynamic fluctuations observed in neonates. Cyclical fluctuations were observed in the blood pressure of 14 neonates receiving dopamine infusions by syringe pump at flow rates from 0.2 to 1 mL/hr. Atom 235 and IVAC 770 pumps and various sizes of Terumo, Becton Dickinson, Omnifix, and IVAC syringes were evaluated. Flow continuity was assessed by using a gravimetric technique. The force needed to initiate and maintain syringe plunger motion was also measured. Noncontinuous flow was encountered most commonly with Terumo syringes, which delivered boluses at regular intervals at flow rates up to 5 mL/hr. The interval was dependent on flow rate and was similar to the time between the blood pressure fluctuations observed clinically. The syringe plunger force exhibited regular fluctuations indicative of the plunger sticking, and simultaneous measurement of flow established a direct temporal relationship with boluses. The other syringes tested did not exhibit such fluctuations. No differences were found between the two syringe pumps. Syringe plunger sticking, resulting in intermittent boluses and potential blood pressure fluctuations, may occur at low flow rates and with certain syringe brands. This appeared to be the cause of hemodynamic fluctuations in neonates receiving dopamine infusions.

Blood Pressure↗
PubMed1995

Flow continuity of infusion systems at low flow rates.

Infusion of fluids and drugs at very low rates may be necessary in neonatal intensive care. Marked haemodynamic fluctuations occurring during the infusion of inotropes have been shown to be due to the sticking of the plunger in the barrel of syringes used in syringe drivers. The Australian Therapeutic Goods Administration has recommended the use of volumetric or peristaltic pumps in these circumstances. We tested a number of infusion systems and found that 1. some syringes give continuous flow at low rates, and would be suitable for the delivery of inotropes, and 2. some infusion pumps provide non-continuous flow at low rates, and would not be satisfactory for the infusion of inotropes.

Humans↗