Murray Hinder

Does caffeine impair cerebral oxygenation and blood flow velocity in preterm infants

Aim:u2002 The aim of the study is to assess the effects of an intravenous 10u2003mg/kg loading dose of caffeine base in cerebral oxygenation, cerebral Doppler blood flow velocity and cardiac output in preterm infants.

Spectral analysis of systemic and cerebral cardiovascular variabilities in preterm infants: relationship with clinical risk index for babies (CRIB).

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.

Neopuff T-piece mask resuscitator: is mask leak related to watching the pressure dial?

Abstract Aim:u2002 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.

Detrended fluctuation analysis of blood pressure in preterm infants with intraventricular hemorrhage

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 1–3xa0h 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 4–15xa0beats) and long-term exponent (α2, for timescale of 15–50xa0beats) computed accordingly. The IVH infants were found to have higher short-term scaling exponents of both MAP and SBP (α1xa0=xa01.06xa0±xa00.18 and 0.98xa0±xa00.20) compared to the non-IVH infants (α1xa0=xa00.84xa0±xa00.25 and 0.78xa0±xa00.25, Pxa0=xa00.017 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.

Cerebral near-infrared spectroscopy analysis in preterm infants with intraventricular hemorrhage

Near-infrared spectroscopy (NIRS) for cerebral circulation monitoring has gained popularity in the neonatal intensive care setting, with studies showing the possibility of identifying preterm infants with intraventricular hemorrhage (IVH) by transfer function analysis of arterial blood pressure (BP) and NIRS measures. In this study, we examined a number of NIRS-derived measures in a cohort of preterm infants with IVH (n = 5) and without IVH (n = 12) within 1–3 hours after birth. The IVH infants were found to have significantly higher tissue oxygenation index (TOI), lower fractional tissue oxygen extraction (FTOE) and lower coherence between arterial BP and deoxygenated hemoglobin (HHb) in the very low frequency range (VLF, 0.02–0.04 Hz). Further studies with larger sample size are warranted for a more complete understanding of the clinical utility of these NIRS measures for early identification of IVH infants.

Prediction of intraventricular haemorrhage in preterm infants using time series analysis of blood pressure and respiratory signals

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 24u2009hours 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 α2), exhibiting a sensitivity of >90% 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.

Neopuff T-piece resuscitator: does device design affect delivered ventilation?

Background The T-piece resuscitator (TPR) is in common use worldwide to deliver positive pressure ventilation during resuscitation of infants <10u2005kg. 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. Aim 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). Design A single operator experienced in newborn resuscitation provided positive pressure ventilation in a randomised sequence to three different Crs models (0.5, 1 and 3u2005mL/cmH2O) at three different set PIP (20, 30 and 40u2005cmH2O). Set PEEP (5u2005cmH2O), gas flow rate and inflation rate were the same for each sequence. Results A total of 1087 inflations were analysed. The delivered mean PEEP was Crs dependent across set PIP range, rising from 4.9 to 8.2u2005cmH2O. At set PIP 40u2005cmH2O and Crs 3u2005mL/cmH2O, the delivered mean PIP was significantly lower at 35.3u2005cmH2O. Conclusions 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.

The effectiveness of Ambu neonatal self-inflating bag to provide consistent positive end-expiratory pressure.

Background 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’. Aim 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. Design Three experienced neonatal medical staff provided positive pressure ventilation each using different disposable and reusable Ambu SIBs, targeting peak inflation pressure of 30–35u2005cmu2005H2O at three different set PEEP levels of 5, 7.5 and 10u2005cmu2005H2O on test lungs of compliance of 0.5 and 3.0u2005mL/cmu2005H2O. Inflation data were captured with Florian Monitor and analysed by analysis of variance for repeated measures. Results A total of 3265 inflations were analysed. The delivered PEEP was rate and lung compliance dependent. At set PEEP of 5u2005cmu2005H2O, the adjusted measured PEEP was 3.6, 4.4 and 4.8u2005cmu2005H2O at rates 20, 40 and 60 IPM, respectively, while at set PEEP of 10u2005cmu2005H2O, the adjusted measured PEEP was 7.0, 8.8 and 9.8u2005cmu2005H2O. The delivered PEEP was statistically higher with more compliant test lungs. Conclusions 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.

Can Ambu self-inflating bag and Neopuff infant resuscitator provide adequate and safe manual inflations for infants up to 10 kg weight?

Background 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 (0.5–10u2005kg) 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. Methods Five experienced clinicians delivered targeted ventilation to three lung models differing in compliance, delivery pressures and inflation rates; Preterm (0.5u2005mL/cmH2O, 25/5 cmH2O, 60 per minute), Term (3u2005mL/cmH2O, 30/5 cmH2O, 40 per minute) and Infant (9u2005mL/cmH2O, 35/5 cmH2O, 30 per minute). The Neopuff was examined with three gas inflow rates (5 litres per minute (LPM), 10 LPM and 15 LPM) and the Ambu with no gas inflow. Results 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. Conclusions 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.

Neonatal endotracheal intubation: How to make it more baby friendly.

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.