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Biomedical subjects

K R Dunster

Publications and source records attributed to K R Dunster.

10 recordsLinked to original sources
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↗