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Biomedical subjects

P B Colditz

Publications and source records attributed to P B Colditz.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1997

Stability of women's perceptions of fetal intrapartum oximetry.

We have previously reported women's perceptions of their experience with fetal intrapartum oxygen saturation monitoring and participation in a research project, assessed within a few days of delivery when the "halo effect' may have influenced responses. To determine whether women's perceptions had changed over time, we sent a second, identical questionnaire to the 49 women in the original sample who had delivered 3-12 months previously. Thirty-eight questionnaires were returned. Wilcoxon signed rank sum test was used to compare the ratings. Women's responses to the first and second questionnaire were not significantly different. Written comments were provided by 23 (61%) of the women. This stability of women's perceptions over time suggests that the original practice of surveying within a few days of delivery accurately reflects women's evaluation of their experience with the research project.

Attitude to Health↗
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↗
PubMed1996

Women's evaluations of their experience with fetal intrapartum oxygen saturation monitoring and participation in a research project.

OBJECTIVE: To evaluation women's perceptions of their participation in a research project in labour and their experience with fetal oxygen saturation monitoring. DESIGN: Survey using a questionnaire of women's rating of ten aspects of their experience with the project. SETTING: Royal Women's Hospital, Brisbane, Australia. PARTICIPANTS: Women who had participated in clinical observational studies of fetal intrapartum oxygen saturation monitoring. FINDINGS: 78 questionnaires were distributed and 77 returned. Overall, women evaluated their participation in this research project favourably, in terms of both their involvement in the research study and the use of fetal oxygen saturation monitoring. Several women commented that they appreciated the additional support they received form the research midwife. KEY CONCLUSIONS: Responses indicated that the women surveyed appreciated the opportunity to participate in research, were not averse to this new technology, and benefited from the perceived additional human contact and support they received. The high response rate to the questionnaire indicates that childbearing women are willing to be included in assessing the appropriateness of new birth technologies that may affect the well-being of women and babies in the future.

Attitude to Health↗
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↗
PubMed1995

Continuous physiological monitoring: an integrated system for use in neonatal intensive care.

A general purpose, multi-channel digital data acquisition and analysis system (Amlab, Associative Measurements, Sydney) configured to collect and process physiological signals including electroencephalograph and blood pressure is described. Its advantages over analog and single-purpose instrumentation are discussed as is its potential, by the addition of transducers, to replace single-purpose instruments.

Electroencephalography↗
PubMed1993

Electrical impedance plethysmography: its use in studying the cerebral circulation of the rabbit.

Electrical impedance plethysmography (EIP) is a noninvasive method that may be useful for both the continuous and serial measurement of changes in pulsatile cerebral blood volume and perhaps cerebral blood flow (CBF). It has not been well validated by comparison with other methods. To attempt to validate the EIP technique, the relationship between the peak amplitude of the transcranial, cardiac-synchronous impedance waveform (dZp) and cerebral blood flow measured by the radiolabelled microsphere technique (CBFrlm) and laser Doppler spectroscopy (CBFlds) was studied in rabbits. CBF was altered by inducing hypertension using metaraminol, hypotension by controlled haemorrhage or hypocarbia by hyperventilation. Twenty-three comparisons between dZp and CBFlds and 19 comparisons with CBFrlm were made in eight rabbits. The percentage change between each measurement using the three techniques in each animal was calculated. Using pooled data from all the animals, the linear regression equations were dZp = 0.5 CBFrlm + 33 (r = 0.38, p = 0.22, SE = 79) and dZp = 0.84 CBFlds + 19.6 (r = 0.46, p = 0.09, SE = 72). It is concluded that, in the anaesthetised rabbit, when large changes in CBF are induced by the manoeuvres described above, changes in dZp correlate very weakly with changes in either cortical or global CBF, and are influenced by other factors such as pulsatile intracranial blood volume.

Animals↗
PubMed1993

Lack of agreement between two methods of measuring haemoglobin.

Haemoglobin values are reported by the current generation of blood gas analysers used in many intensive care units. A comparison of one such machine against a reference found that there was a mean difference of 1.32 g/dL (95% confidence intervals -2.75-0.9 g/dL) between the values reported. Haemoglobin values reported by blood gas machines may be inaccurate.

Hemoglobins↗
PubMed1992

The variable appearances of fetal gallstones.

Only four cases of fetal gallstones have been reported previously, which implies that this condition is rare. Gallstones in children have been reported more frequently, and it may be that some of these are present in fetal life. Over a 12 month period in this department, seven cases of gallstones or sludge were seen within the fetal gallbladder. The variable appearances of fetal cholelithiasis are described and the possible causes discussed. Fetal gallstones may not be as rare as indicated by the paucity of cases in the literature.

Adult↗
PubMed1990

Continuous cerebral electrical impedance monitoring in sick preterm infants.

Cerebral electrical impedance (dZ) and intra-arterial blood pressure were measured continuously during the first 48 h after birth in 26 sick ventilated preterm infants with a birth weight less than 1500 g. The aim was to establish whether any patterns of dZp or the variability of either blood pressure or dZp would allow identification of those infants who developed intraventricular haemorrhage (IVH), periventricular leucomalacia (PVL) or a poor neurological outcome. IVH and PVL were diagnosed by ultrasound image obtained every 6 h. Cerebral electrical impedance recordings were unsuitable for analysis in three patients and a further three died within 14 h of birth. In the remaining 20 patients, no step changes that may have been related to the onset of IVH or PVL were evident and whilst three patterns of dZp were identified, they were not useful in distinguishing between normal infants or those who developed IVH, PVL or had a poor neurological outcome. Using multiple linear regression, the coefficient of variation of dZp was significantly associated with both IVH and outcome, as was the coefficient of variation of blood pressure. Continuous measurement of cerebral electrical impedance, whilst technically feasible in sick preterm infants, was not found useful as a method of identifying those who developed IVH, PVL or had a poor neurological outcome.

Blood Pressure Determination↗
PubMed1989

Variability of Doppler flow velocity and cerebral perfusion pressure is reduced in the neonate by sedation and neuromuscular blockade.

Doppler flow velocity (DFV) in the anterior cerebral artery was recorded every 12 h and cerebral perfusion pressure (CPP) continuously in 21 sick, ventilated preterm neonates for 48 h from shortly after birth. Ten received a neuromuscular blocker, seven were sedated with morphine infusions and five received neither of these treatments. Variability of DFV and CPP was assessed by the coefficient of variation (CV) and the autocorrelation function (ACF). Variability of both signals was lowest in the group treated by neuromuscular blockade (DFV CV 3, s.d. = 0.8; CPP CV 9, s.d. = 2.2; CPP ACF 37, s.d. = 19.2), intermediate in the group receiving sedation by morphine infusion (DFV CV 3.4, s.d. = 0.7; CPP CV 11, s.d. = 2.2; CPP ACF 31, s.d. = 21.6) and highest in the group receiving neither treatment (DFV CV 5, s.d. = 1.8; CPP CV 14, s.d. = 2.3; CPP ACF 27, s.d. = 16.7). Variability also increased with decreasing gestational age, suggesting that immature cerebrovascular regulatory mechanisms were present in the least mature neonates.

Birth Weight↗