A sustained first inflation (SI) at birth may aid lung liquid clearance and aeration, but the impact of SI duration relative to the volume-response of the lung is poorly understood. We compared three SI strategies: 1) variable duration defined by attaining volume equilibrium using real-time electrical impedance tomography (EIT; SI plat); 2) 30 s beyond equilibrium (SI long); 3) short 30-s SI (SI30); and 4) positive pressure ventilation without SI (no-SI) on spatiotemporal aeration and ventilation (EIT), gas exchange, lung mechanics, and regional early markers of injury in preterm lambs. Fifty-nine fetal-instrumented lambs were ventilated for 60 min after applying the allocated first inflation strategy. At study completion molecular and histological markers of lung injury were analyzed. The time to SI volume equilibrium, and resultant volume, were highly variable; mean (SD) 55 (34) s, coefficient of variability 59%. SI plat and SIlong resulted in better lung mechanics, gas exchange and lower ventilator settings than both no-SI and SI30. At 60 min, alveolar-arterial difference in oxygen was a mean (95% confidence interval) 130 (13, 249) higher in SI30 vs. SIlong group (two-way ANOVA). These differences were due to better spatiotemporal aeration and tidal ventilation, although all groups showed redistribution of aeration towards the nondependent lung by 60 min. Histological lung injury scores mirrored spatiotemporal change in aeration and were greatest in SI 30 group (P Ͻ 0.01, Kruskal-Wallis test). An individualized volume-response approach to SI was effective in optimizing aeration, homogeneous tidal ventilation, and respiratory outcomes, while an inadequate SI duration had no benefit over positive pressure ventilation alone. sustained inflation; neonatal resuscitation; lung mechanics; lung volume; variability; electrical impedance tomography; lung injury THE MAJORITY OF EXTREMELY preterm infants require respiratory assistance in the delivery room (41). In part this is because many of these infants do not have the ability to generate the initial prolonged high transpulmonary pressures required to drive lung fluid from the main airways, allow alveolar aeration, establish functional residual capacity (FRC), and then maintain it during tidal ventilation, essential processes for efficient gas exchange and lung protection (19,31). Recently, applying an initial sustained inflation (SI) at birth, consisting of an elevated pressure applied for longer than needed for usual tidal inflation, followed by sufficient positive end-expiratory pressure (PEEP), has been proposed as a method of generating the initial transpulmonary pressure needed at birth (10,18,20). SI has been extensively investigated in preterm animals (15,26,29,32,33,(35)(36)(37)(38) and humans (10, 18, 34) with conflicting results. Some studies suggested SI improved aeration, FRC, and cerebral oxygen delivery (29,32,33), while others failed to demonstrate any benefit over standard respiratory support with sufficient PEEP (26,(35)(36)(37). SI was associated wi...

Background: In translational animal studies both a sustained inflation (SI) and PEEP have been associated with better lung aeration at birth, but the role of each on lung injury is inconclusive. We aimed to determine the effect of different PEEP and SI strategies at birth on early development of lung injury pathways. Method: 70 antenatal-steroid exposed lambs (125d AE 1d) were instrumented during caesarean section. Lambs were randomly assigned to either 1) Positive Pressure Ventilation (PPV; n = 20) using volume targeted ventilation at PEEP 8 cmH 2 O (maximum PIP 35 cmH 2 O, V T 7 ml/kg), 2) Volumetric Sustained Inflation 1 at 35 cmH 2 O until full aeration was visualised using electrical impedance tomography (SI; n = 23), or 3) 3-min Dynamic PEEP strategy 1 guided by breath-to-breath compliance (n = 27). All lambs were treated at 10 min with surfactant 200 mg/kg, and then received PPV for 90 min, with measurement of mechanics and gas exchange throughout. Standardised samples from the gravity-dependent and non-dependent lung were analysed for early injury mRNA markers (EGR1, CYR61, CTGF, IL-6,-8,-1B) and histology. Results: All groups expressed injury in the non-dependent lung compared to unventilated fetal controls across all injury parameters (p < 0.0001 ANOVA). In the dependent lung, only SI resulted in higher EGR1, CYR61, CTGF, IL-6,-1B expression compared to PPV and dynamic PEEP (p < 0.0001 ANOVA), and both were not different from fetal controls. Dynamic PEEP had better oxygenation throughout (p < 0.0001, two-way ANOVA) Conclusions: This large preterm lamb study is the first to show significant injury differences between SI and PEEP starte-gies. Early lung injury was heterogeneous and greater in the dependent lung following a SI. This suggests that achieving aeration slowly using tidal inflations maybe more beneficial than a SI. Reference: 1. Tingay DG et al. Background: Volume targeted ventilation (VTV) is widely used and may reduce lung injury, but this assumes the clinically set V T (V Tset) is accurately delivered. The aims of this prospective observational study were to determine the relationship between V Tset , expiratory V T (V Te) and endotracheal tube leak in a modern neonatal VTV ventilator, and the resultant PaCO 2 relationship with and without VTV. Method: Continuous inflations were recorded for 24 hours in 100 infants receiving synchronised mechanical ventilation (SLE5000, SLE Ltd, UK) with VTV (n = 77 infants) or without, and either the manufacturer's V4 (n = 50) or newer V5 (n = 50) VTV algorithm. For every inflation the set V Tset , V Te and leak were determined (maximum 90000 inflations/infant). If PaCO 2 was sampled (maximum 2/infant), this was compared with the average V T data from the preceeding 15 minutes. Results: A total of 7,917,020 inflations were analysed. Using VTV the V Tset-V Te bias (95% CI) was 0.3 (−0.12, 0.19) mL/kg. Leak influenced V Tset-V Te bias with V4 algorithm (r 2 = −0.64, p < 0.0001; linear regression) but not V5 (r 2 = 0.04, p = 0.21). Overall 80% of V Te were AE...

High strain rate is a risk factor for ventilator-induced pulmonary edema, possibly because it amplifies lung viscoelastic behavior.

BackgroundCurrent sustained lung inflation (SI) approaches use uniform pressures and durations. We hypothesized that gestational-age-related mechanical and developmental differences would affect the time required to achieve optimal lung aeration, and resultant lung volumes, during SI delivery at birth in lambs.Methods49 lambs, in five cohorts between 118 and 139 days of gestation (term 142 d), received a standardized 40 cmHO SI, which was delivered until 10 s after lung volume stability (optimal aeration) was visualized on real-time electrical impedance tomography (EIT), or to a maximum duration of 180 s. Time to stable lung aeration (T) within the whole lung, gravity-dependent, and non-gravity-dependent regions, was determined from EIT recordings.ResultsT was inversely related to gestation (P<0.0001, Kruskal-Wallis test), with the median (range) being 229 (85,306) s and 72 (50,162) s in the 118-d and 139-d cohorts, respectively. Lung volume at T increased with gestation from a mean (SD) of 20 (17) ml/kg at 118 d to 56 (13) ml/kg at 139 d (P=0.002, one-way ANOVA). There were no gravity-dependent regional differences in T or aeration.ConclusionsThe trajectory of aeration during an SI at birth is influenced by gestational age in lambs. An understanding of this may assist in developing SI protocols that optimize lung aeration for all infants.

Despite differing mechanisms for generating positive airway pressure, when compared at the same Prp, NCPAP and HHHFNC provide similar effects on all the outcomes explored.

These results suggest that FOT and the measurement of C (X5) could be a useful tool for the non-invasive measurement of lung volume recruitment/derecruitment.

ABSTRACT:The study of respiratory mechanics in infants requires a noninvasive accurate measurement of the lung volume changes (⌬V L ). Optoelectronic plethysmography (OEP) allows the assessment of ⌬V L through the measurement of the chest wall surface motion and it has been proved to be accurate in adults. The aim of this study was to apply OEP to newborns and to validate it by comparison to pneumotachography. Twenty term and preterm newborns (GA ϭ 34 Ϯ 5 wk) in stable condition were studied during 1 to 2 min periods of quiet breathing in supine position. Airway opening flow was measured by applying a facemask connected to a pneumotachograph (PNT) and integrated to provide the ⌬V L . Chest wall volume changes were simultaneously measured by OEP. The tidal volume values measured by pneumotachography and by OEP were compared for each breath. A total of 771 breaths from all patients were considered. Bland-Altmann analysis showed a mean difference of Ϫ0.08 mL and a limit of agreement ranging from Ϫ2.98 to 2.83 mL. Linear regression analysis demonstrated good correlation between the two techniques (r 2 ϭ 0.95, q ϭ 1.00 mL, m ϭ 0.96). OEP provides accurate measurements of ⌬V L in newborns and may be useful to study respiratory mechanics and breathing patterns during spontaneous breathing and mechanical ventilation. T he study of respiratory mechanics and control of breathing ideally requires an accurate and noninvasive measurement of lung volume changes (⌬V L ) not interfering with patients' spontaneous activity. Unfortunately, the currently available methods for the measurement of ⌬V L in infants present several intrinsic and unresolved limitations.Most of the techniques require either connections to the airway opening or critical patient-and posture-dependent calibration procedures. Connecting to the airway opening may introduce leaks, annoy the infant, and affect the breathing pattern (1,2), while the use of patient-dependent calibration procedures can lead to inaccurate measurements when a patient's condition or posture changes with respect to the baseline state (3). Moreover, none of the existing techniques have proved to be reliable in tracking long-term changes in endexpiratory lung volume (EELV) due to integration drift or problems in the measurements stability (4,5).Optoelectronic plethysmography (OEP) is a noninvasive technique, which estimates chest wall volume (V CW ) by measuring the three-dimensional position of several reflective markers placed on the patient's thorax (6 -8). This technique has proved to be reliable in adults in different postures and conditions (7,8).OEP does not require a connection to the airway opening or subject-specific calibration procedures. It provides an accurate measurement of the V CW and it allows, through the use of subsets of the markers placed on the thorax, the measurement of separate compartments, such as the rib cage, abdomen, or smaller components (9). Being based on the direct measurement of chest wall volumes, OEP is not affected by integration drift and can be use...

The assessment of C(X5) allowed the definition of PEEP(ol) to be in agreement with CT data. Thus, FOT measurements of C(X5) may provide a non-invasive bedside tool for PEEP titration.