Following the first development in its modern form in 1972 by Takuo Aoyagi [1], pulse oximetry has become invaluable for monitoring oxygenation and pulse rate [4]. A constant amount of light (DC) from the pulseoximeter is absorbed by skin, other tissues, and nonpulsatile blood, while a variable amount of light (AC) is absorbed by pulsating arterial inflow. The pulsatile signal indexed against the non-pulsatile signal and expressed as a percentage (AC/DC · 100) is commonly referred to as the perfusion index (PI). Skin colourimetry is related to illness severity in newborns [2] but its utility as a monitoring tool is partially limited by requiring direct caregiver assessment. As local skin vasoconstriction can be associated with skin colour changes, the usefulness of PI for assessing neonatal illness severity was similarly tested.A prospective study was carried out on 101 inborn or outborn Caucasian neonates (52 males, 49 females; gestational age 34.7±4.0 weeks, range 24.7-41.1 weeks; birth weight 2310±950 g, range 410-4170 g) during the first 24 h after admission. Illness severity was determined using the Score for Neonatal Acute Physiology (SNAP) [5] and the infants were categorised as either high or low severity of illness, defined by the presence of severe neonatal morbidity and/or a 24 h SNAP score >10 [2]. PI values were assessed using a Masimo SET Radical pulse-oximeter (Masimo Corp., Irvine, Calif., USA) with the sensor placed randomly on either foot. After the pulse wave was verified to be artifact-free, the PI values were manually captured by an operator, who was unaware of the infant illness severity group, at least every 0.3 min for a duration of 10.6±2.3 min (95% CI 9.9-11.4 min, range: 10-15 min). SpO 2 , pulse rate, body (skin and core) temperature, and blood pressure were also measured. Out of a total of 2,571 measurements, 2,546 (99.02%) artifact-free readings were obtained. The higher severity group showed a significantly higher frequency of severe neonatal morbidity (P=0.025), as determined by the presence of at least one of the following: sepsis or pneumonia; bronchopulmonary dysplasia; intraventricular haemorrhage grade 3 or more; periventricular leukomalacia grade 3 or more; retinopathy of prematurity grade 3 or more; and necrotising enterocolitis [2]. Predictive accuracy for identifying newborns with higher severity for different cut-off values of PI, SpO 2 , and pulse rate was calculated using receiver operating characteristic (ROC) curve [3]. Model calibration was evaluated using v 2 to compare the expected values (according to the classification of infants into two severity categories) with the expected values (according to the SpO 2 , pulse rate and PI values). According to the predefined criteria, 43 neonates (42.6%) were allocated to the high severity group and 58 to the low severity group. Male to female ratio, gestational age, birth weight, body temperature, mean blood pressure, and use of peripheral vasoconstrictors and vasodilators were not significantly different between the two se...

Support of the mechanically complex preterm lung needs to facilitate aeration while avoiding ventilation heterogeneities: whether to achieve this gradually or quickly remains unclear. We compared the effect of gradual vs. constant tidal inflations and a pressure-limited sustained inflation (SI) at birth on gas exchange, lung mechanics, gravity-dependent lung volume distribution, and lung injury in 131-day gestation preterm lambs. Lambs were resuscitated with either 1) a 20-s, 40-cmH2O pressure-limited SI (PressSI), 2) a gradual increase in tidal volume (Vt) over 5-min from 3 ml/kg to 7 ml/kg (IncrVt), or 3) 7 ml/kg Vt from birth. All lambs were subsequently ventilated for 15 min with 7 ml/kg Vt with the same end-expiratory pressure. Lung mechanics, gas exchange and spatial distribution of end-expiratory volume (EEV), and tidal ventilation (electrical impedance tomography) were recorded regularly. At 15 min, early mRNA tissue markers of lung injury were assessed. The IncrVt group resulted in greater tissue hysteresivity at 5 min (P = 0.017; two-way ANOVA), higher alveolar-arterial oxygen difference from 10 min (P < 0.01), and least uniform gravity-dependent distribution of EEV. There were no other differences in lung mechanics between groups, and the PressSI and 7 ml/kg Vt groups behaved similarly throughout. EEV was more uniformly distributed, but Vt least so, in the PressSI group. There were no differences in mRNA markers of lung injury. A gradual increase in Vt from birth resulted in less recruitment of the gravity-dependent lung with worse oxygenation. There was no benefit of a SI at birth over mechanical ventilation with 7 ml/kg Vt.

BackgroundSustained inflations (SI) are advocated for the rapid establishment of FRC after birth in preterm and term infants requiring resuscitation. However, the most appropriate way to deliver a SI is poorly understood. We investigated whether a volume-limited SI improved the establishment of FRC and ventilation homogeneity and reduced lung inflammation/injury compared to a pressure-limited SI.Methods131 d gestation lambs were resuscitated with either: i) pressure-limited SI (PressSI: 0-40 cmH2O over 5 s, maintained until 20 s); or ii) volume-limited SI (VolSI: 0-15 mL/kg over 5 s, maintained until 20 s). Following the SI, all lambs were ventilated using volume-controlled ventilation (7 mL/kg tidal volume) for 15 min. Lung mechanics, regional ventilation distribution (electrical impedance tomography), cerebral tissue oxygenation index (near infrared spectroscopy), arterial pressures and blood gas values were recorded regularly. Pressure-volume curves were performed in-situ post-mortem and early markers of lung injury were assessed.ResultsCompared to a pressure-limited SI, a volume-limited SI had increased pressure variability but reduced volume variability. Each SI strategy achieved similar end-inflation lung volumes and regional ventilation homogeneity. Volume-limited SI increased heart-rate and arterial pressure faster than pressure-limited SI lambs, but no differences were observed after 30 s. Volume-limited SI had increased arterial-alveolar oxygen difference due to higher FiO2 at 15 min (p = 0.01 and p = 0.02 respectively). No other inter-group differences in arterial or cerebral oxygenation, blood pressures or early markers of lung injury were evident.ConclusionWith the exception of inferior oxygenation, a sustained inflation targeting delivery to preterm lambs of 15 mL/kg volume by 5 s did not influence physiological variables or early markers of lung inflammation and injury at 15 min compared to a standard pressure-limited sustained inflation.

The technological strategies implemented in Masimo SET pulse oximetry effectively permit continuous monitoring of SpO2 during challenging clinical conditions of motion and poor tissue perfusion.

Our findings indicate that HCA is a major predictor of morbidity and mortality in VLBW newborns.