Transfusion of packed red blood cells reduces selenium levels and increases lipid peroxidation in an in vivo ovine model.

BACKGROUND: Oxidative stress from surgery or critically illness has been shown to adversely contribute to morbidity and mortality. Recent studies record that oxidative stress is heightened following packed red blood cell (PRBC) transfusions and that products of oxidative stress accumulate as the PRBC ages. However, there are no studies that investigate if transfusion of aged PRBC actually increases the recipient's oxidative stress profile more than fresh PRBC. OBJECTIVE: To compare the effect of fresh vs aged PRBC transfusions on the recipient's oxidative stress using an ovine model. MATERIALS AND METHODS: Male sheep were transfused with either fresh (n = 6) or aged (n = 6) ovine PRBC, and serial blood samples taken. Plasma samples were analysed for lipid peroxidation using the thiobarbituric acid reactive substances (TBARS) assay. This served as an indicator of oxidative injury. Antioxidant function and trace element levels were also measured. RESULTS: Like human PRBC, the ovine PRBC had negligible selenium levels. Irrespective of age, PRBC transfusion was associated with reduced selenium levels and antioxidant function, which correlated with increased markers of lipid peroxidation. CONCLUSION: Transfusion of selenium poor PRBC can dilute selenium levels and compromise glutathione peroxidase antioxidant activity and thereby allow lipid peroxidation. As there was no evidence that aged PRBC induced more severe oxidative injury this suggests that selenium dilution is a key underlying mechanism. Further studies are needed to assess the impact of transfusion-related oxidative stress in massive transfusions.

A comprehensive ovine model of blood transfusion.

BACKGROUND: The growing awareness of transfusion-associated morbidity and mortality necessitates investigations into the underlying mechanisms. Small animals have been the dominant transfusion model but have associated limitations. This study aimed to develop a comprehensive large animal (ovine) model of transfusion encompassing: blood collection, processing and storage, compatibility testing right through to post-transfusion outcomes. MATERIALS AND METHODS: Two units of blood were collected from each of 12 adult male Merino sheep and processed into 24 ovine-packed red blood cell (PRBC) units. Baseline haematological parameters of ovine blood and PRBC cells were analysed. Biochemical changes in ovine PRBCs were characterized during the 42-day storage period. Immunological compatibility of the blood was confirmed with sera from potential recipient sheep, using a saline and albumin agglutination cross-match. Following confirmation of compatibility, each recipient sheep (n = 12) was transfused with two units of ovine PRBC. RESULTS: Procedures for collecting, processing, cross-matching and transfusing ovine blood were established. Although ovine red blood cells are smaller and higher in number, their mean cell haemoglobin concentration is similar to human red blood cells. Ovine PRBC showed improved storage properties in saline-adenine-glucose-mannitol (SAG-M) compared with previous human PRBC studies. Seventy-six compatibility tests were performed and 17·1% were incompatible. Only cross-match compatible ovine PRBC were transfused and no adverse reactions were observed. CONCLUSION: These findings demonstrate the utility of the ovine model for future blood transfusion studies and highlight the importance of compatibility testing in animal models involving homologous transfusions.

Stored blood transfusion induces transient pulmonary arterial hypertension without impairing coagulation in an ovine model of nontraumatic haemorrhage.

BACKGROUND AND OBJECTIVES: Transfusion of blood products in particular older products is associated with patient morbidity. Previously, we demonstrated a higher incidence of acute lung injury in lipopolysaccharide-treated sheep transfused with stored blood products. As transfusion following haemorrhage is more common, we aimed to determine whether a 'first hit' of isolated haemorrhage would precipitate similar detrimental effects following transfusion and also disrupt haemostasis. MATERIALS AND METHODS: Anaesthetized sheep had 33% of their total blood volume collected into Leukotrap bags (Pall Medical), which were processed into packed red blood cells and cross-matched for transfusion into other sheep. After 30 mins, the sheep were resuscitated with either: fresh (<5 days old) or stored (35-42 days old) ovine blood followed by 4% albumin to replacement volume, albumin alone or normal saline alone and monitored for 4 h. RESULTS: The first hit of haemorrhage precipitated substantial decreases in mean arterial pressure however haemostasis was preserved. Transfusion of stored ovine blood induced (1) transient pulmonary arterial hypertension but no oedema and (2) reduced fibrinogen levels more than fresh blood, but neither induced coagulopathy. Thus, transfusion of stored blood affected pulmonary function even in the absence of overt organ injury. CONCLUSION: The fact that stored blood transfusions: (1) did not induce acute lung injury in contrast to previous lipopolysaccharide-primed animal models identifies the 'first hit' as an important determinant of the severity of transfusion-mediated injury; (2) impaired pulmonary dynamics verifies the sensitivity and vulnerability of the pulmonary system to injury.

Cyanoacrylate tissue adhesives - effective securement technique for intravascular catheters: in vitro testing of safety and feasibility.

Partial or complete dislodgement of intravascular catheters remains a significant problem in hospitals despite current securement methods. Cyanoacrylate tissue adhesives (TA) are used to close skin wounds as an alternative to sutures. These adhesives have high mechanical strength and can remain in situ for several days. This study investigated in vitro use of TAs in securing intravascular catheters (IVC). We compared two adhesives for interaction with IVC material, comparing skin glues with current securement methods in terms of their ability to prevent IVC dislodgement and inhibit microbial growth. Two TAs (Dermabond, Ethicon Inc. and Histoacryl, B. Braun) and three removal agents (Remove™, paraffin and acetone) were tested for interaction with IVC material by use of tensile testing. TAs were also compared against two polyurethane (standard and bordered) dressings (Tegaderm™ 1624 and 1633, 3M Australia Pty Ltd) and an external stabilisation device (Statlock, Bard Medical, Covington) against control (unsecured IVCs) for ability to prevent pull-out of 16 G peripheral IVCs from newborn fresh porcine skin. Agar media containing pH-sensitive dye was used to assess antimicrobial properties of TAs and polyurethane dressings to inhibit growth of Staphylococcus aureus and Staphylococcus epidermidis. Neither TA weakened the IVCs (P >0.05). Of removal agents, only acetone was associated with a significant decrease in IVC strength (P <0.05). Both TAs and Statlock significantly increased the pull-out force (P <0.01). TA was quick and easy to apply to IVCs, with no irritation or skin damage noted on removal and no bacterial colony growth under either TA.

Reduced intubation rates for infants after introduction of high-flow nasal prong oxygen delivery.

PURPOSE: To describe the change in ventilatory practice in a tertiary paediatric intensive care unit (PICU) in the 5-year period after the introduction of high-flow nasal prong (HFNP) therapy in infants <24 months of age. Additionally, to identify the patient subgroups on HFNP requiring escalation of therapy to either other non-invasive or invasive ventilation, and to identify any adverse events associated with HFNP therapy. METHODS: The study was a retrospective chart review of infants <24 months of age admitted to our PICU for HFNP therapy. Data was also extracted from both the local database and the Australian New Zealand paediatric intensive care (ANZPIC) registry for all infants admitted with bronchiolitis. RESULTS: Between January 2005 and December 2009, a total of 298 infants <24 months of age received HFNP therapy. Overall, 36 infants (12%) required escalation to invasive ventilation. In the subgroup with a primary diagnosis of viral bronchiolitis (n = 167, 56%), only 6 (4%) required escalation to invasive ventilation. The rate of intubation in infants with viral bronchiolitis reduced from 37% to 7% over the observation period corresponding with an increase in the use of HFNP therapy. No adverse events were identified with the use of HFNP therapy. CONCLUSION: HFNP therapy has dramatically changed ventilatory practice in infants <24 months of age in our institution, and appears to reduce the need for intubation in infants with viral bronchiolitis.

The effect of endotracheal suction on regional tidal ventilation and end-expiratory lung volume.

PURPOSE: To examine the impact of different endotracheal tube (ETT) suction techniques on regional end-expiratory lung volume (EELV) and tidal volume (V(T)) in an animal model of surfactant-deficient lung injury. METHODS: Six 2-week old piglets were intubated (4.0 mm ETT), muscle-relaxed and ventilated, and lung injury was induced with repeated saline lavage. In each animal, open suction (OS) and two methods of closed suction (CS) were performed in random order using both 5 and 8 French gauge (FG) catheters. The pre-suction volume state of the lung was standardised on the inflation limb of the pressure-volume relationship. Regional EELV and V(T) expressed as a proportion of the impedance change at vital capacity (%Z (VCroi)) within the anterior and posterior halves of the chest were measured during and for 60 s after suction using electrical impedance tomography. RESULTS: During suction, 5 FG CS resulted in preservation of EELV in the anterior (non-dependent) and posterior (dependent) lung compared to the other permutations, but these only reached significance in the anterior regions (p < 0.001 repeated-measures ANOVA). V(T) within the anterior, but not posterior lung was significantly greater during 5FG CS compared to 8 FG CS; the mean difference was 15.1 [95% CI 5.1, 25.1]%Z (VCroi). Neither catheter size nor suction technique influenced post-suction regional EELV or V(T) compared to pre-suction values (repeated-measures ANOVA). CONCLUSIONS: ETT suction causes transient loss of EELV and V(T) throughout the lung. Catheter size exerts a greater influence than suction method, with CS only protecting against derecruitment when a small catheter is used, especially in the non-dependent lung.

Prediction of outcome following hypoxia/ischaemia in the human infant using cerebral impedance.

OBJECTIVE: Changes in cerebral impedance in the newborn piglet are able to discriminate, within 1-2 h of acute hypoxia, between animals which will have a good neurological outcome, and those who have suffered more severe hypoxia resulting in poor outcome. The aim of this study was to determine if cerebral impedance could be used to identify those human infants with an encephalopathy following acute hypoxia who subsequently have a poor neurological outcome. It is these infants who may benefit most from neural rescue treatment. METHODS: Twenty-four newborn term infants with evidence of severe acute intrapartum hypoxia and encephalopathy were studied. Bioimpedance spectroscopy was commenced as soon as possible after birth and repeated every 30 min until the infant was 12 h old. Neurodevelopmental outcome was assessed at 12 months of age. RESULTS: Although cerebral impedance was different to control values, there was no significant difference in cerebral impedance between hypoxic babies with normal and those with abnormal development. CONCLUSION: Cerebral impedance was increased in hypoxic babies, as predicted from animal data, but the method was not suitable for discrimination of outcome. SIGNIFICANCE: Cerebral impedance is not useful for early identification of infants who subsequently have a poor outcome after acute intrapartum hypoxia and who may benefit from neural rescue treatment.

Gas exchange during perfluorocarbon liquid immersion: life-support for the ex utero fetus.

BACKGROUND: Respiratory mortality and morbidity remain major consequences of extreme prematurity. Percutaneous transfer of oxygen and carbon dioxide is possible in the newborn human. Perfluorocarbon (PFC) liquids have excellent oxygen and carbon dioxide carrying capacity. Animals can breath immersed in perfluorocarbon liquids and maintain adequate gas exchange. Our hypothesis is that the combination of spontaneous tidal perfluorocarbon breathing and respiration through the skin immersed in perfluorocarbon will allow adequate gas exchange in the preterm newborn. In this pilot study we aimed to observe the effects of immersion in FC-77 perfluorocarbon liquid on the preterm lamb. PILOT DATA: Four preterm lambs at 100-115 days gestation were delivered using a modified EXIT procedure. Immediately after complete delivery, the catheterised lamb was immersed in warm, oxygenated FC-77 perfluorocarbon liquid. Physiological monitoring was done for up to 60 min. All lambs were warmed adequately and seemed to have centrally intact circulation initially. All had little or no respiratory effort and there was no appreciable lung expansion. All had severe respiratory acidosis. DISCUSSION: For the provision of immediate ex utero care to the 'fetus' there are three requirements: adequate gas exchange surfaces and sufficient oxygen and carbon dioxide gradients, a functioning circulation, and an environment capable of keeping the lamb warm (thus minimising metabolic demand, oxygen consumption and carbon dioxide production). In this pilot study the greatest initial problem was the severe and rapidly worsening respiratory acidosis. The major problem was a lack of respiratory drive. No lung expansion from the outset would yield zero contribution to gas exchange from the lungs. An intact central circulation does not necessarily mean that the pulmonary circulation, respiratory drive and/or the skin circulation are adequate. For adequate gas exchange to occur it will require a 'breathing' animal with expanded alveoli. If the transition from the normal in utero state to immersion in PFC was immediate, and lung expansion was achieved, it could still be possible to achieve adequate gas exchange through the skin and lungs of the extremely preterm newborn. HYPOTHESIS: Given the potential for gas exchange across the skin of the extremely preterm infant we hypothesise that the immersion of extremely preterm infants in PFC liquid will allow optimal percutaneous gas exchange to occur. Given some lung gas exchange with less injurious liquid ventilation (spontaneous or mechanical) we hypothesise that the combination of skin and lung gas exchange will provide sufficient gas exchange to support life.

Insertion distance of neonatal intercostal catheters using a 10 French Argyle trocar thoracic catheter.

OBJECTIVE: We believed that intercostal catheters were often inserted too far into the thoracic cavity in neonatal patients. The aim of this study was to determine the average distance from the catheter tip to the midline, of intercostal catheters inserted in our neonatal unit and the incidence of catheters that were inserted too far into the thoracic cavity. METHODS: During a two year period we examined the chest X-rays of all infants who had an intercostal catheter inserted using an Argyle 10 French trocar thoracic catheter for drainage of a pneumothorax. For each initial chest X-ray following the insertion of the intercostal catheter we measured the horizontal distance in mm from catheter tip to the midline. The tip to midline distance was zero if the tip was at the midline and negative if it crossed the midline. To standardise the tip to midline distance for different size infants we measured the distance in 'inter-vertebral' units. RESULTS: During the two year period, 13 of 24 intercostal catheters (54%) crossed the midline (i.e. were inserted too far). The mean (+/- SD) tip to midline distance was -1.29 (+/- 13.9) mm with a range varying between -40 to 34 mm with a calculated 'inter-vertebral' units mean (+/- SD) tip to midline distance of -0.32 (+/- 1.9) range -4.6 to 4.0. CONCLUSIONS: Fifty four percent of the intercostal catheters inserted in our unit were inserted too far. As the distance markings on the Argyle intercostal catheters are marked from the last side-hole rather than from the tip of the catheter, Argyle intercostal catheters may be inadvertently inserted two centimetres further than they should be.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.