ORCID Profile
0000-0002-9179-316X
Current Organisations
University of Sydney
,
University of London
,
Westmead Hospital
,
TAFE NSW
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Publisher: Wiley
Date: 16-07-2019
DOI: 10.1111/TRF.15452
Abstract: Red blood cell (RBC) transfusion is a standard treatment for anemia of prematurity. Cerebral tissue oxygenation and blood flow velocities improve when a restrictive transfusion threshold is followed, but little is known about the effect of practicing a liberal transfusion threshold on cerebral tissue oxygenation, cerebral blood flow velocities, and cardiac output measurements. A prospective observational study of preterm infants under 32 weeks' gestation who received RBC transfusion. Monitoring was performed immediately before, immediately after, and 24 hours after transfusion. Data obtained included physiologic parameters, cerebral tissue oxygenation index (TOI), anterior and middle cerebral artery pulsed Doppler ultrasound measurements, and cardiac output measurements. Data were analyzed using analysis of variance for repeated measures. Fifty RBC transfusion episodes in 40 preterm infants were monitored. The mean gestational age was 26.72 weeks (±1.6 weeks), and the mean birth weight was 855.25 g (±190.7 g). We did not observe significant changes in cerebral TOI (pretransfusion mean TOI = 70.5 [11.54], immediately after transfusion = 71.38 [12.51], [p = 0.924 95% confidence interval (CI), -4.64 to 6.39], and 24 hours after transfusion = 75.64 [14.4] [p = 0.07 95% CI, -0.37 to 10.65]), cerebral fractional tissue oxygen extraction (pretransfusion = 0.25 [0.12], immediately after transfusion = 0.24 [0.13], and 24 hours after transfusion = 0.20 [0.15]), cerebral resistive index, cerebral pulsatility index, or right ventricular output. Statistically significant changes were observed immediately after transfusion in peak systolic velocity, end-diastolic velocity and time-averaged maximum velocity in the cerebral arterial circulation. Left ventricular output (pretransfusion = 374.32 mL/kg/min, immediately after transfusion = 346.67 mL/kg/min [p = 0.000 95% CI, -39.61 to -15.68], and 24 hours after transfusion = 361.17 mL/kg/min [p = 0.027 95% CI, -25.11 to -1.18]) and heart rate (pretransfusion = 163.37 [9.49], immediately after transfusion = 157.29 [10.2] [p = 0.000 95% CI, -8.96 to -3.20], and 24 hours after transfusion = 160.40 [10.4] [p = 0.041 95% CI, -5.85 to -0.09]) showed statistically significant changes throughout the monitoring period. Our findings show that practicing liberal transfusion thresholds did not improve cerebral TOI in preterm infants who have mild anemia, but it did improve the compensatory response in cerebral arterial blood flow and cardiac output.
Publisher: Wiley
Date: 12-11-2019
DOI: 10.1111/JPC.14679
Abstract: The use of umbilical arterial catheters (UACs) is a standard of care in monitoring critically unwell infants. Serious vascular complications are rare but when they do occur, they can be associated with significant morbidity, risking limb loss or even death. Near infra-red spectroscopy has the potential to monitor limb perfusion. Our study investigates changes in tissue oxygenation and perfusion in the abdominal and leg circulation following UAC insertion. A prospective observational study performing ultrasound pulsed Doppler measurements in the coeliac, superior mesenteric artery, renal arteries and the femoral arteries as well as near infrared spectroscopy measurements of both thighs at three time points (immediately before = Time 1, 1 h after = Time 2 and 24 h after UAC insertion = Time 3). We monitored 30 infants, the mean gestational age was 30 weeks (24-41) and the mean birthweight was 1720 g (600-4070 g). We observed statistically significant changes (P < 0.05) in pulse Doppler measurements in coeliac (mean peak systolic velocity (PSV): Time 1 = 70.51, Time 2 = 61.75 resistive index (RI): Time 1 = 0.75, Time 2 = 0.67), superior mesenteric (PSV: Time 1 = 41.72, Time 2 = 36.10 RI: Time 1 = 0.92, Time 2 = 0.87), renal (same side end-diastolic velocity: Time 1 = 1.98, Time 2 = 3.80 RI: Time 1 = 0.93, Time 2 = 0.87 opposite side end-diastolic velocity: Time 1 = 2.62, Time 2 = 3.84 RI: Time 1 = 0.92, Time 2 = 0.85) and femoral arteries (same side PSV: Time 1 = 72.75, Time 2 = 62.18 opposite side PSV: Time 1 = 81.89, Time 2 = 62.74). Tissue oxygenation in lower limbs remained unaffected (same side (mean): Time 1 = 68.59, Time 2 = 68.99, Time 3 = 66.40, opposite side: Time 1 = 67.72, Time 2 = 66.92, Time 3 = 65.40). All infants on clinical examination had normal lower limb perfusion, lower limb arterial pulses and normal perfusion to the gluteal region before and after insertion of UAC. While sub-clinical changes in perfusion occur in abdominal and leg circulation, these changes are not consistent across vessels and regional tissue oxygenation remains unaffected.
Publisher: BMJ
Date: 07-06-2011
Abstract: Little is known regarding the variations in effective ventilation during bag and mask resuscitation with standard methods compared with that delivered by ventilator-delivered mask ventilation (VDMV). To measure the variations in delivered airway pressure, tidal volume (TV), minute ventilation (MV) and inspiratory time during a 3-min period of mask ventilation comparing VDMV with three commonly used hand-delivered methods of bag and mask ventilation: Laerdal self-inflating bag (SIB) anaesthetic bag and T-piece Neopuff. A modified resuscitation manikin was used to measure variation in mechanical ventilation during 3-min periods of mask ventilation. Thirty-six experienced practitioners gave positive pressure mask ventilation targeting acceptable chest wall movement with a rate of 60 inflations/min and when pressures could be targeted or set, a peak inspiratory pressure (PIP) of 18 cm water, positive end-expiratory pressure (PEEP) of 5 cm water, for 3 min with each of the four mask ventilation methods. Each mode was randomly sequenced. A total of 21 136 inflations were recorded and analysed. VDMV achieved PIP and PEEP closest to that targeted and significantly lower variation in all measured parameters (p<0.001) other than with PIP. SIB delivered TV and MV over twice that delivered by VDMV and Neopuff. During 3-min periods of mask ventilation on a manikin, VDMV produced the least variation in delivered ventilation. SIB produced wide variation and unacceptably high TV and MV in experienced hands.
Publisher: Public Library of Science (PLoS)
Date: 26-04-2016
Publisher: BMJ
Date: 19-09-2017
DOI: 10.1136/ARCHDISCHILD-2016-311164
Abstract: The T-piece resuscitator (TPR) is in common use worldwide to deliver positive pressure ventilation during resuscitation of infants <10 kg. Ease of use, ability to provide positive end-expiratory pressure (PEEP), availability of devices inbuilt into resuscitaires and cheaper disposable options have increased its popularity as a first-line device for term infant resuscitation. Research into its ventilation performance is limited to preterm infant and animal studies. Efficacy of providing PEEP and the use of TPR during term infant resuscitation are not established. The aim of this study is to determine if delivered ventilation with the Neopuff brand TPR varied with differing (preterm to term) test lung compliances (Crs) and set peak inspiratory pressures (PIP). A single operator experienced in newborn resuscitation provided positive pressure ventilation in a randomised sequence to three different Crs models (0.5, 1 and 3 mL/cmH A total of 1087 inflations were analysed. The delivered mean PEEP was Crs dependent across set PIP range, rising from 4.9 to 8.2 cmH As Crs increases, the Neopuff TPR can produce clinically significant levels of auto-PEEP and thus may not be optimal for the resuscitation of term infants with healthy lungs.
Publisher: Wiley
Date: 04-07-2017
DOI: 10.1111/JPC.13609
Abstract: The aim of this study was to compare mask leak with three different peak inspiratory pressure (PIP) settings during T-piece resuscitator (TPR Neopuff) mask ventilation on a neonatal manikin model. Participants were neonatal unit staff members. They were instructed to provide mask ventilation with a TPR with three PIP settings (20, 30, 40 cm H A total of 12 749 inflations delivered by 40 participants were analysed. There were no statistically significant differences (P > 0.05) in the mask leak with the three PIP settings. No statistically significant differences were seen in respiratory rate and inspiratory time with the three PIP settings. There was a significant rise in PEEP as the PIP increased. Failure to achieve the desired PIP was observed especially at the higher settings. In a neonatal manikin model, the mask leak does not vary as a function of the PIP when the flow rate is constant. With a fixed rate and inspiratory time, there seems to be a rise in PEEP with increasing PIP.
Publisher: IEEE
Date: 08-2011
Publisher: BMJ
Date: 20-10-2020
Publisher: Cold Spring Harbor Laboratory
Date: 13-09-2023
Publisher: Wiley
Date: 12-09-2018
DOI: 10.1002/AJUM.12114
Publisher: MDPI AG
Date: 28-06-2023
Abstract: Background: Newborn resuscitation guidelines recommend positive pressure ventilation (PPV) for newborns who do not establish effective spontaneous breathing after birth. T-piece resuscitator systems are commonly used in high-resource settings and can additionally provide positive end-expiratory pressure (PEEP). Short expiratory time, high resistance, rapid dynamic changes in lung compliance and large tidal volumes increase the possibility of incomplete exhalation. Previous publications indicate that this may occur during newborn resuscitation. Our aim was to study ex les of incomplete exhalations in term newborn resuscitation and discuss these against the theoretical background. Methods: Ex les of flow and pressure data from respiratory function monitors (RFM) were selected from 129 term newborns who received PPV using a T-piece resuscitator. RFM data were not presented to the user during resuscitation. Results: Ex les of incomplete exhalation with higher-than-set PEEP-levels were present in the recordings with visual correlation to factors affecting time needed to complete exhalation. Conclusions: Incomplete exhalation and the relationship to expiratory time constants have been well described theoretically. We documented ex les of incomplete exhalations with increased PEEP-levels during resuscitation of term newborns. We conclude that RFM data from resuscitations can be reviewed for this purpose and that incomplete exhalations should be further explored, as the clinical benefit or risk of harm are not known.
Publisher: Elsevier BV
Date: 04-2021
Publisher: BMJ
Date: 18-10-2019
DOI: 10.1136/ARCHDISCHILD-2018-315391
Abstract: A controlled bench test was undertaken to determine the performance variability among a range of neonatal self-inflating bags (SIB) compliant with current International Standards Organisation (ISO). Use of SIB to provide positive pressure ventilation during newborn resuscitation is a common emergency procedure. The United Nations programmes advocate increasing availability of SIB in low-income and middle-income nations and recommend devices compliant with ISO. No systematic study has evaluated variance in different models of neonatal SIB. 20 models of SIB were incrementally compressed by an automated robotic device simulating the geometry and force of a human hand across a range of precise distances in a newborn lung model. Significance was calculated using analysis of variance repeated measures to determine the relationship between distance of SIB compression and delivered ventilation. A pass/fail was derived from a composite score comprising: minimum tidal volume coefficient of variation (across all compression distances) peak pressures generated and functional compression distance. Ten out of the 20 models of SIB failed our testing methodology. Two models could not provide safe minimum tidal volumes (2.5–5 mL) six models exceeded safety inflation pressure limit cm H 2 O, representing 6% of their inflations five models had excessive coefficient of variation ( % averaged across compression distances) and three models did not deliver inflation volumes .5 mL until approximately 50% of maximum bag compression distance was reached. The study also found significant intrabatch variability and forward leakage. Compliance of SIBs with ISO standards may not guarantee acceptable or safe performance to resuscitate newborn infants.
Publisher: Wiley
Date: 17-08-2010
DOI: 10.1111/J.1651-2227.2010.01816.X
Abstract: The aim of the study is to compare mask leak and delivered ventilation during Neopuff (NP) mask ventilation in two modes: (i) with NP pressure dial hidden and resuscitator watching chest wall (CW) rise with, (ii) CW movement hidden and resuscitator watching NP pressure dial. Thirty-six participants gave mask ventilation to a modified manikin designed to measure mask leak and delivered ventilation for two minutes in each mode randomly assigned. Paired t-tests were used to analyse differences in mean values. Linear regression was used to determine the association of mask leak with delivered ventilation. Of 7277 inflations analysed, 3621 were observing chest wall mode (CWM) and 3656 observing NP mode (NPM). Mask leak was similar between the groups 31.6% for CWM and 31.5% (p = 0.56) for NPM. There were no significant differences in airways pressures and expired tidal volumes (TVe) between modes. Mask leak was strongly associated with TVe (R = -0.86 p < 0.0001) and with peak inspiratory pressure (PIP) (R = -0.51 p < 0.0001). TVe was associated with PIP (R = 0.51 p < 0.0001). This study provides reassurance that NP mask leak is not greater when resuscitators watch the NP pressure dial. Mask leak is related to TVe. Mask ventilation training with manikins should include tidal volume measurements.
Publisher: Wiley
Date: 05-2016
DOI: 10.1111/JPC.13192
Abstract: Neonatal endotracheal intubation is commonly accompanied by significant disturbances in physiological parameters. The procedure is often poorly tolerated, and multiple attempts are commonly required before the airway is secured. Adverse physiological effects include hypoxemia, bradycardia, hypertension, elevation in intracranial pressure and possibly increase in pulmonary vascular resistance. Use of premedications to facilitate intubation has been shown to reduce but not eliminate these effects. Other important preventative factors include adequate training of the operators and guidelines to limit the duration of attempts. Pre-intubation stabilisation with optimal bag and mask ventilation should allow for better neonatal tolerance of the procedure. Recent research has described significant mask leak and airway obstruction compromising efficacy of neonatal mask ventilation. Further research should help in elucidating mask ventilation techniques which minimise mask leak and airway obstruction.
Publisher: BMJ
Date: 04-05-2019
DOI: 10.1136/ARCHDISCHILD-2018-314860
Abstract: The T-piece resuscitator (TPR) has seen increased use as a primary resuscitation device with newborns. Traditional TPR design uses a high resistance expiratory valve to produce positive end expiratory pressure (PEEP) or continuous positive airway pressure (CPAP) at resuscitation. A new TPR device that uses a dual flow ratio valve (fluidic flip) to produce PEEP/CPAP is now available (rPAP). We aimed to compare the measured ventilation performance of different TPR devices in a controlled bench test study. Single operator provided positive pressure ventilation to an incremental testlung compliance (Crs) model (0.5–5 mL/cmH 2 O) with five different brands of TPR device (Atom, Neopuff, rPAP, GE Panda warmer and Draeger Resuscitaire). At recommended peak inflation pressure (PIP) 20 cmH 2 O, PEEP of 5 cmH 2 O and rate of 60 inflations per minute. 1864 inflations were analysed. Four of the five devices tested demonstrated inadvertent elevations in mean PEEP (5.5–10.3 cmH 2 O, p .001) from set value as Crs was increased, while one device (rPAP) remained at the set value. Measured PIP exceeded the set value in two infant warmer devices (GE and Draeger) with inbuilt TPR at Crs of 0.5 (24.5 and 23.5 cmH 2 O, p .001). Significant differences were seen in tidal volumes across devices particularly at higher Crs (p .001). Results show important variation in delivered ventilation from set values due to inherent TPR device design characteristics with a range of lung compliances expected at birth. Device-generated inadvertent PEEP and overdelivery of PIP may be clinically deleterious for term and preterm newborns or infants with larger Crs during resuscitation.
Publisher: BMJ
Date: 23-12-2017
DOI: 10.1136/ARCHDISCHILD-2016-311830
Abstract: Manual resuscitation devices for infants and newborns must be able to provide adequate ventilation in a safe and consistent manner across a wide range of patient sizes (0.5-10 kg) and differing clinical states. There are little comparative data assessing biomechanical performance of common infant manual resuscitation devices across the manufacturers' recommended operating weight ranges. We aimed to compare performance of the Ambu self-inflating bag (SIB) with the Neopuff T-piece resuscitator in three resuscitation models. Five experienced clinicians delivered targeted ventilation to three lung models differing in compliance, delivery pressures and inflation rates Preterm (0.5 mL/cmH 3309 inflations were collected and analysed with analysis of variance for repeated measures. The Neopuff was unable to reach set peak inflation pressures and exhibited seriously elevated positive end expiratory pressure (PEEP) with all inflow gas rates (p<0.001) in this infant model. The Ambu SIB accurately delivered targeted pressures in all three models. The Ambu SIB was able to accurately deliver targeted pressures across all three models from preterm to infant. The Neopuff infant resuscitator was unable to deliver the targeted pressures in the infant model developing clinically significant levels of inadvertent PEEP which may pose risk during infant resuscitation.
Publisher: Springer Science and Business Media LLC
Date: 29-05-2013
DOI: 10.1007/S11517-013-1083-0
Abstract: Very preterm infants are at high risk of death and serious permanent brain damage, as occurs with intraventricular hemorrhage (IVH). Detrended fluctuation analysis (DFA) that quantifies the fractal correlation properties of physiological signals has been proposed as a potential method for clinical risk assessment. This study examined whether DFA of the arterial blood pressure (ABP) signal could derive markers for the identification of preterm infants who developed IVH. ABP data were recorded from a prospective cohort of 30 critically ill preterm infants in the first 1-3 h of life, 10 of which developed IVH. DFA was performed on the beat-to-beat sequences of mean arterial pressure (MAP), systolic blood pressure (SBP) and pulse interval, with short-term exponent (α1, for timescale of 4-15 beats) and long-term exponent (α2, for timescale of 15-50 beats) computed accordingly. The IVH infants were found to have higher short-term scaling exponents of both MAP and SBP (α1 = 1.06 ± 0.18 and 0.98 ± 0.20) compared to the non-IVH infants (α1 = 0.84 ± 0.25 and 0.78 ± 0.25, P = 0.017 and 0.038, respectively). The results have demonstrated that fractal dynamics embedded in the arterial pressure waveform could provide useful information that facilitates early identification of IVH in preterm infants.
Publisher: IOP Publishing
Date: 02-11-2011
DOI: 10.1088/0967-3334/32/12/003
Abstract: Frequency spectrum analysis of circulatory signals has been proposed as a potential method for clinical risk assessment of preterm infants by previous studies. In this study, we examined the relationships between various spectral measures derived from systemic and cerebral cardiovascular variabilities and the clinical risk index for babies (CRIB II). Physiological data collected from 17 early low birth weight infants within 1-3 h after birth were analysed. Spectral and cross-spectral analyses were performed on heart rate variability, blood pressure variability and cerebral near-infrared spectroscopy measures such as oxygenated and deoxygenated haemoglobins (HbO(2) and HHb) and tissue oxygenation index (TOI). In addition, indices related to cardiac baroreflex sensitivity and cerebral autoregulation were derived from the very low, low- and mid-frequency ranges (VLF, LF and MF). Moderate correlations with CRIB II were identified from mean arterial pressure (MAP) normalized MF power (r = 0.61, P = 0.009), LF MAP-HHb coherence (r = 0.64, P = 0.006), TOI VLF percentage power (r = 0.55, P = 0.023) and LF baroreflex gain (r = -0.61, P = 0.01 after logarithmic transformation), with the latter two parameters also highly correlated with gestational age (r = -0.75, P = 0.0005 and r = 0.70, P = 0.002, respectively). The relationships between CRIB II and various spectral measures of arterial baroreflex and cerebral autoregulation functions have provided further justification for these measures as possible markers of clinical risks and predictors of adverse outcome in preterm infants.
Publisher: BMJ
Date: 11-11-2011
Abstract: To compare a new two-person method (four hands) of delivering mask ventilation with a standard one-person method using the Laerdal self-inflating bag (SIB) and the Neopuff (NP) infant resuscitator in a manikin model. Recent studies of simulated neonatal resuscitation using bag and mask ventilation techniques have shown facemask leak levels of 55-57% in expert hands. 48 participants were randomly paired and instructed to give mask ventilation for a 2-min period as single-person resuscitators, then as two-person paired resuscitators at set pressures for NP and set parameters for SIB. Airway pressure, flow, inspiratory tidal volume, expiratory tidal volume and mask leak were recorded. A total of 21 578 inflations were recorded and analysed. For SIB, mask leak was greater (11.5%) with single-person compared to two-person (5.4% mean difference 6.1%, 95% CI 1.5 to 10.7, p<0.01). For NP, mask leak was greater for single-person (22.2%) compared to two-person (9.1% mean difference 13.1% 95% CI 3.6 to 22.6, p<0.01). For single-person mask ventilation, mask leak was greater with NP (22.2%) compared to SIB (11.5% mean difference 10.7%, 95% CI 1.4 to 19.7, p<0.01). For two-person mask ventilation, mask leak was greater for NP (9.1%) compared to SIB (5.4% mean difference 3.7%, 95% CI 0.1 to 6.4, p<0.05). Two-person mask ventilation technique reduces mask leak by approximately 50% compared to the standard one-person mask ventilation method. NP mask ventilation has higher mask leak than Laerdal SIB for both single- and two-person technique mask ventilation.
Publisher: BMJ
Date: 11-08-2018
DOI: 10.1136/ARCHDISCHILD-2017-312766
Abstract: International neonatal resuscitation guidelines recommend the use of laryngeal mask airway (LMA) with newborn infants (≥34 weeks’ gestation or kg weight) when bag-mask ventilation (BMV) or tracheal intubation is unsuccessful. Previous publications do not allow broad LMA device comparison. To compare delivered ventilation of seven brands of size 1 LMA devices with two brands of face mask using self-inflating bag (SIB). 40 experienced neonatal staff provided inflation cycles using SIB with positive end expiratory pressure (PEEP) (5 cmH 2 O) to a specialised newborn/infant training manikin randomised for each LMA and face mask. All subjects received prior education in LMA insertion and BMV. 12 415 recorded inflations for LMAs and face masks were analysed. Leak detected was lowest with i-gel brand, with a mean of 5.7% compared with face mask (triangular 42.7, round 35.7) and other LMAs (45.5–65.4) (p .001). Peak inspiratory pressure was higher with i-gel, with a mean of 28.9 cmH 2 O compared with face mask (triangular 22.8, round 25.8) and other LMAs (14.3–22.0) (p .001). PEEP was higher with i-gel, with a mean of 5.1 cmH 2 O compared with face mask (triangular 3.0, round 3.6) and other LMAs (0.6–2.6) (p .001). In contrast to other LMAs examined, i-gel had no insertion failures and all users found i-gel easy to use. This study has shown dramatic performance differences in delivered ventilation, mask leak and ease of use among seven different brands of LMA tested in a manikin model. This coupled with no partial or complete insertion failures and ease of use suggests i-gel LMA may have an expanded role with newborn resuscitation as a primary resuscitation device.
Publisher: Wiley
Date: 23-05-2019
DOI: 10.1111/APA.14382
Abstract: To evaluate the acute effect of intravenous caffeine on heart rate and blood pressure variability in preterm infants. We extracted and compared linear and nonlinear features of heart rate and blood pressure variability at two time points: prior to and in the two hours following a loading dose of 10 mg/kg caffeine base. We studied 31 preterm infants with arterial blood pressure data and 25 with electrocardiogram data, and compared extracted features prior to and following caffeine administration. We observed a reduction in both scaling exponents (α 1 , α 2 ) of mean arterial pressure from detrended fluctuation analysis and an increase in the ratio of short‐ ( SD 1) and long‐term ( SD 2) variability from Poincare analysis ( SD 1/ SD 2). Heart rate variability analyses showed a reduction in α 1 (mean ( SD ) of 0.92 (0.21) to 0.86 (0.21), p 0.01), consistent with increased vagal tone. Following caffeine, beat‐to‐beat pulse pressure variability ( SD ) also increased (2.1 (0.64) to 2.5 (0.65) mmHg, p 0.01). This study highlights potential elevation in autonomic nervous system responsiveness following caffeine administration reflected in both heart rate and blood pressure systems. The observed increase in pulse pressure variability may have implications for caffeine administration to infants with potentially impaired cerebral autoregulation.
Publisher: American Geophysical Union (AGU)
Date: 10-2012
DOI: 10.1029/2011WR010657
Abstract: The complexity of hydrological systems and the necessary simplification of models describing these systems remain major challenges in hydrological modeling. Kirchner's (2009) approach of inferring rainfall and evaporation from discharge fluctuations by “doing hydrology backward” is based on the assumption that catchment behavior can be conceptualized with a single storage‐discharge relationship. Here we test Kirchner's approach using a densely instrumented hydrologic measurement network spanning 24 geologically erse subbasins of the Alzette catchment in Luxembourg. We show that effective rainfall rates inferred from discharge fluctuations generally correlate well with catchment‐averaged precipitation radar estimates in catchments ranging from less than 10 to more than 1000 km 2 in size. The correlation between predicted and observed effective precipitation was 0.8 or better in 23 of our 24 catchments, and prediction skill did not vary systematically with catchment size or with the complexity of the underlying geology. Model performance improves systematically at higher soil moisture levels, indicating that our study catchments behave more like simple dynamical systems with unambiguous storage‐discharge relationships during wet conditions. The overall mean correlation coefficient for all subbasins for the entire data set increases from 0.80 to 0.95, and the mean bias for all basins decreases from –0.61 to –0.35 mm d −1 . We propose an extension of Kirchner's approach that uses in situ soil moisture measurements to distinguish wet and dry catchment conditions.
Publisher: Wiley
Date: 10-03-2014
DOI: 10.1111/APA.12573
Abstract: To determine changes in respiratory mechanics when chest compressions are added to mask ventilation, as recommended by the International Liaison Committee on Resuscitation (ILCOR) guidelines for newborn infants. Using a Laerdal Advanced Life Support leak-free baby manikin and a 240-mL self-inflating bag, 58 neonatal staff members were randomly paired to provide mask ventilation, followed by mask ventilation with chest compressions with a 1:3 ratio, for two minutes each. A Florian respiratory function monitor was used to measure respiratory mechanics, including mask leak. The addition of chest compressions to mask ventilation led to a significant reduction in inflation rate, from 63.9 to 32.9 breaths per minute (p < 0.0001), mean airway pressure reduced from 7.6 to 4.9 cm H2 O (p < 0.001), minute ventilation reduced from 770 to 451 mL/kg/min (p < 0.0001), and there was a significant increase in paired mask leak of 6.8% (p < 0.0001). Adding chest compressions to mask ventilation, in accordance with the ILCOR guidelines, in a manikin model is associated with a significant reduction in delivered ventilation and increase in mask leak. If similar findings occur in human infants needing an escalation in resuscitation, there is a potential risk of either delay in recovery or inadequate response to resuscitation.
Publisher: Elsevier BV
Date: 08-2021
Publisher: Copernicus GmbH
Date: 05-07-2012
DOI: 10.5194/HESS-16-1863-2012
Abstract: Abstract. Soil-atmosphere feedback is a key for understanding the hydrological cycle and the direction of potential system changes. This paper presents an analytical framework to study the interplay between soil and atmospheric moisture, using as input only the boundary conditions at the upstream end of trajectory, assuming advective moisture transport with average wind speed along this trajectory and vertical moisture exchange with the soil compartment of uniform vertical properties. Precipitation, evaporation from interception and runoff are assumed to depend through simple functional relationships on the soil moisture or the atmospheric moisture. Evaporation from soil moisture (including transpiration) depends on both state variables, which introduces a nonlinear relationship between the two compartments. This nonlinear relationship can explain some apparently paradoxical phenomena such as a local decrease of precipitation accompanied by a runoff increase. The solutions of the resulting water balance equations correspond to two different spatial moisture regimes showing either an increasing or a decreasing atmospheric moisture content along a trajectory starting at the coast, depending on boundary conditions and parameters. The paper discusses how different model parameters (e.g. time scales of precipitation, evaporation or runoff) influence these regimes and how they can create regime switches. Such an analysis has potential to anticipate the range of possible land use and climate changes or to interpret the results of complex land-atmosphere interaction models. Based on derived analytical expressions for the Horton index, the Budyko curve and a precipitation recycling ratio, the analytical framework opens new perspectives for the classification of hydrological systems.
Publisher: Wiley
Date: 10-12-2019
DOI: 10.1111/APA.14636
Abstract: To evaluate cerebral autoregulation changes in preterm infants receiving a loading dose of caffeine base. In a cohort of 30 preterm infants, we extracted measures of cerebral autoregulation using time and frequency domain techniques to determine the correlation between mean arterial pressure (MAP) and tissue oxygenation index (TOI) signals. These measures included the cerebral oximetry index (COx), cross‐correlation and coherence measures, and were extracted prior to caffeine loading and in the 2 hours following administration of 10 mg/kg caffeine base. We observed acute reductions in time domain correlation measures, including the cerebral oximetry index (linear mixed model coefficient −0.093, standard error 0.04 p = 0.028) and the detrended cross‐correlation coefficient (ρ 5 coefficient −0.13, standard error 0.055 p = 0.025). These reductions suggested an acute improvement in cerebral autoregulation. Features from detrended cross‐correlation analysis also showed greater discriminative value than other methods in identifying changes prior to and following caffeine administration. We observed a reduced correlation between MAP and TOI from near‐infrared spectroscopy following caffeine administration. These findings suggest an acute enhanced capacity for cerebral autoregulation following a loading dose of caffeine in preterm infants, contributing to our understanding of the physiological impact of caffeine therapy.
Publisher: BMJ
Date: 19-01-2016
DOI: 10.1136/ARCHDISCHILD-2015-308649
Abstract: The self-inflating bag (SIB) is the most common device used to resuscitate newborn infants worldwide. Delivering positive end-expiratory pressure (PEEP) may be important in infant resuscitation and limited research using one brand (Laerdal) SIB has led to international guidelines stating SIBs 'often deliver inconsistent positive end-expiratory pressure'. To measure delivered PEEP using disposable and reusable Ambu SIBs fitted with Ambu PEEP valve and manometer comparing different rates of 20, 40 and 60 inflations per minute (IPM) and test lung compliance. Three experienced neonatal medical staff provided positive pressure ventilation each using different disposable and reusable Ambu SIBs, targeting peak inflation pressure of 30-35 cm H2O at three different set PEEP levels of 5, 7.5 and 10 cm H2O on test lungs of compliance of 0.5 and 3.0 mL/cm H2O. Inflation data were captured with Florian Monitor and analysed by analysis of variance for repeated measures. A total of 3265 inflations were analysed. The delivered PEEP was rate and lung compliance dependent. At set PEEP of 5 cm H2O, the adjusted measured PEEP was 3.6, 4.4 and 4.8 cm H2O at rates 20, 40 and 60 IPM, respectively, while at set PEEP of 10 cm H2O, the adjusted measured PEEP was 7.0, 8.8 and 9.8 cm H2O. The delivered PEEP was statistically higher with more compliant test lungs. The Ambu SIB with Ambu PEEP valve can deliver consistent mean levels of PEEP close to the operator set PEEP. The performance of SIB with PEEP valves is likely brand specific and requires further evaluation.
Publisher: BMJ
Date: 16-06-2020
DOI: 10.1136/ARCHDISCHILD-2019-318673
Abstract: T-piece resuscitators (TPRs) are used for primary newborn resuscitation in birthing and emergency rooms worldwide. A recent study has shown spikes in peak inflation pressure (PIP) over set values with two brands of TPRs inbuilt into infant warmer/resuscitation platforms. We aimed to compare delivered ventilation between two TPR drivers with inflation pressure spikes to a standard handheld TPR in a low test lung compliance (Crs), leak-free bench test model. A single operator provided positive pressure ventilation to a low compliance test lung model (Crs 0.2–1 mL/cmH 2 O) at set PIP of 15, 25, 35 and 40 cmH 2 O. Two TPR devices with known spikes (Draeger Resuscitaire, GE Panda) were compared with handheld Neopuff (NP). Recommended settings for positive end-expiratory pressure (5 cmH 2 O), inflation rate of 60/min and gas flow rate 10 L/min were used. 2293 inflations were analysed. Draeger and GE TPR drivers delivered higher mean PIP (Panda 18.9–49.5 cmH2O Draeger 21.2–49.2 cmH2O and NP 14.8–39.9 cmH2O) compared with set PIP and tidal volumes (TVs) compared with the NP (Panda 2.9–7.8 mL Draeger 3.8–8.1 mL compared with NP 2.2–6.0 mL), outside the prespecified acceptable range (±10% of set PIP and ±10% TV compared with NP). The observed spike in PIP over set values with Draeger and GE Panda systems resulted in significantly higher delivered volumes compared with the NP with identical settings. Manufacturers need to address these differences. The effect on patient outcomes is unknown.
Publisher: Wiley
Date: 17-08-2000
DOI: 10.1111/J.1651-2227.2010.01828.X
Abstract: The aim of the study is to assess the effects of an intravenous 10 mg/kg loading dose of caffeine base in cerebral oxygenation, cerebral Doppler blood flow velocity and cardiac output in preterm infants. Preterm neonates <34 weeks gestation were investigated at 1 and 4 h following the loading dose of caffeine using Doppler cerebral sonography, cardiac echocardiography and cerebral spatially resolved near-infrared spectroscopy. Forty infants were studied with a mean gestational age (mean ± standard deviation) of 27.7 (±2.5) weeks, birth weight of 1155 (±431) g and a postnatal age of 2.8 (±2.2) days. Mean Anterior Cerebral Artery peak and time average mean blood flow velocity fell significantly by 14% and 17.7%, respectively at 1 h post-caffeine loading dose, which recovered partially by 4 h. Cerebral Tissue Oxygenation Index fell from pre-dose levels by 9.5% at 1 h with partial recovery to 4.9% reduced at 4 h post-dose. There were no significant changes in left or right ventricular output, transcutaneous oxygen saturation, transcutaneous PCO(2) or total vascular resistance. A loading dose of 10 mg/kg caffeine base resulted in significant reduction at 1 h post-dose in cerebral oxygenation and cerebral blood flow velocity with partial recovery at 4 h.
Publisher: Wiley
Date: 18-05-2020
DOI: 10.1111/VOX.12938
Publisher: IEEE
Date: 07-2013
Publisher: American Physiological Society
Date: 05-2002
DOI: 10.1152/JAPPLPHYSIOL.00619.2001
Abstract: To assess effects of anesthesia and opioids, we studied 13 children with obstructive sleep apnea (OSA, age 4.0 ± 2.2 yr, mean ± SD) and 24 age-matched control subjects (5.8 ± 4.0 yr). Apnea indexes of children with OSA were 29.4 ± 18 h −1 , median 30 h −1 . Under inhalational anesthetic, closing pressure at the mask was 2.2 ± 6.9 vs. −14.7 ± 7.8 cmH 2 O, OSA vs. control ( P 0.001). After intubation, spontaneous ventilation was 115.5 ± 56.9 vs. 158.7 ± 81.6 ml · kg −1 · min −1 , OSA vs. control ( P = 0.02), despite elevated Pco 2 (49.3 vs. 42.1 Torr, OSA vs. control, P 0.001). Minute ventilation fell after fentanyl (0.5 μg/kg iv), with central apnea in 6 of 13 OSA cases vs. 1 of 23 control subjects ( P 0.001). Consistent with the finding of reduced spontaneous ventilation, apnea was most likely when end-tidal CO 2 exceeded 50 Torr during spontaneous breathing under anesthetic. Thus children with OSA had depressed spontaneous ventilation under anesthesia, and opioids precipitated apnea in almost 50% of children with OSA who were intubated but breathing spontaneously under inhalational anesthesia.
Publisher: BMJ
Date: 02-2023
DOI: 10.1136/BMJPO-2022-001768
Abstract: Mask leak and airway obstruction are common with mask ventilation in newborn infants, leading to suboptimal ventilation. We aimed to perform a pilot study measuring respiratory mechanics during one-person and two-person mask ventilation in preterm infants at birth. Infants less than 30 weeks’ gestation were eligible for the study. In the two-person method, one person holds the mask in place and the other provides positive pressure ventilation compared with the standard one-person mask hold. A respiratory function monitor was used in line with a T-piece resuscitator to measure mask leak and airway obstruction. Deferred consent was obtained. Twenty-five infants were recruited. The mean (SD) birth weight was 920.4 g (188.3), and mean (SD) gestational age was 27.3 weeks (3.0). Percentage mask leak was higher in the one-person mask method (26.4±18.5) compared with the two-person mask method (17.6±9.3) (p = 0.018). The mean (SD) expired tidal volume (V Te , mL) in breaths with leak was 3.9 (1.57) in the one-person method compared with 3.05 (1.0) the two-person method (p=0.31). A significantly lower mean (SD) end-tidal carbon dioxide (EtCO 2, mm Hg) was measured at 25.3 (9.9) in breaths with mask leak, compared with 30.8 (12.1) in breaths without leak. The breaths with airway obstruction had lower mean EtCO 2 (25.9 vs 30.8, p=0.003) and lower mean V Te (1.71 vs 6.95, p .001). Mask leak and airway obstruction are common in resuscitation of preterm infants at birth. The use of the two-person mask technique is effective and it could be a useful option if mask ventilation with the one-person method is not effective. ACTRN12614000245695.
Publisher: Frontiers Media SA
Date: 07-06-2021
Abstract: Background: Resuscitation of infants using T-piece resuscitators (TPR) allow positive pressure ventilation with positive end-expiratory pressure (PEEP). The adjustable PEEP valve adds resistance to expiration and could contribute to inadvertent PEEP. The study indirectly investigated risk of inadvertent peep by determining expiratory time constants. The aim was to measure system expiratory time constants for a TPR device in a passive mechanical model with infant lung properties. Methods: We used adiabatic bottles to generate four levels of compliance (0.5–3.4 mL/cm H 2 O). Expiratory time constants were recorded for combinations of fresh gas flow (8, 10, 15 L/min), PEEP (5, 8, 10 cm H 2 O), airway resistance (50, 200 cm H 2 O/L/sec and none), endotracheal tube (none, size 2.5, 3.0, 3.5) with a peak inflation pressure of 15 cm H 2 O above PEEP. Results: Low compliances resulted in time constants below 0.17 s contrasting to higher compliances where the expiratory time constants were 0.25–0.81 s. Time constants increased with increased resistance, lower fresh gas flows, higher set PEEP levels and with an added airway resistance or endotracheal tube. Conclusions: The risk of inadvertent PEEP increases with a shorter time for expiration in combination with a higher compliance or resistance. The TPR resistance can be reduced by increasing the fresh gas flow or reducing PEEP. The expiratory time constants indicate that this may be clinically important. The risk of inadvertent PEEP would be highest in intubated term infants with highly compliant lungs. These results are useful for interpreting clinical events and recordings.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2023
Publisher: Elsevier BV
Date: 08-2012
Publisher: IEEE
Date: 10-2016
Publisher: Springer Science and Business Media LLC
Date: 24-04-2017
DOI: 10.1038/SREP46538
Abstract: Despite the decline in mortality rates of extremely preterm infants, intraventricular haemorrhage (IVH) remains common in survivors. The need for resuscitation and cardiorespiratory management, particularly within the first 24 hours of life, are important factors in the incidence and timing of IVH. Variability analyses of heart rate and blood pressure data has demonstrated potential approaches to predictive monitoring. In this study, we investigated the early identification of infants at a high risk of developing IVH, using time series analysis of blood pressure and respiratory data. We also explore approaches to improving model performance, such as the inclusion of multiple variables and signal pre-processing to enhance the results from detrended fluctuation analysis. Of the models we evaluated, the highest area under receiver-operator characteristic curve (5th, 95th percentile) achieved was 0.921 (0.82, 1.00) by mean diastolic blood pressure and the long-term scaling exponent of pulse interval (PI α 2 ), exhibiting a sensitivity of % at a specificity of 75%. Following evaluation in a larger population, our approach may be useful in predictive monitoring to identify infants at high risk of developing IVH, offering caregivers more time to adjust intensive care treatment.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Murray Hinder.