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Volume-targeted ventilation (VTV) has been increasingly used in neonatology. In systematic reviews, VTV has been shown to reduce the risk of neonatal morbidities and improve long-term outcomes. It is adaptive ventilation using complex computer algorithms to deliver ventilator inflations with expired tidal volumes close to a target set by clinicians. Significant endotracheal tube leak and patient-ventilator interactions may complicate VTV and make ventilator parameters and waveforms difficult to interpret. In this article, we review the rationale for using VTV and the evidence supporting its use and provide practical advice for clinicians ventilating newborn infants., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Modern neonatal ventilators allow the downloading of their data with a high sampling rate. We wanted to develop an algorithm that automatically recognises and characterises ventilator inflations from ventilator pressure and flow data., Methods: We downloaded airway pressure and flow data with 100 Hz sampling rate from Dräger Babylog VN500 ventilators ventilating critically ill infants. We developed an open source Python package, Ventiliser, that includes a rule-based algorithm to automatically discretise ventilator data into a sequence of flow and pressure states and to recognise ventilator inflations and an information gain approach to identify inflation phases (inspiration, expiration) and sub-phases (pressure rise, pressure plateau, inspiratory hold etc.)., Results: Ventiliser runs on a personal computer and analyses 24 h of ventilation in 2 min. With longer recordings, the processing time increases linearly. It generates a table reporting indices of each breath and its sub-phases. Ventiliser also allows visualisation of individual inflations as waveforms or loops. Ventiliser identified >97% of ventilator inflations and their sub-phases in an out-of-sample validation of manually annotated data. We also present detailed quantitative analysis and comparison of two 1-hour-long ventilation periods., Conclusions: Ventiliser can analyse ventilation patterns and ventilator-patient interactions over long periods of mechanical ventilation., Impact: We have developed a computational method to recognize and analyse ventilator inflations from raw data downloaded from ventilators of preterm and critically ill infants. There have been no previous reports on the computational analysis of neonatal ventilator data. We have made our program, Ventiliser, freely available. Clinicians and researchers can use Ventiliser to analyse ventilator inflations, waveforms and loops over long periods. Ventiliser can also be used to study ventilator-patient interactions.

Objectives: To report how peak inflating pressure (PIP), tidal volume (VT) and low-tidal volume alarms are affected by maximum allowed inflating pressure (P max ) during volume guarantee (VG) ventilation., Study Design: Ventilation data were analysed with 1 Hz sampling rate from 25 neonates receiving synchronised intermittent positive pressure ventilation with VG for >12 h., Results: The difference between P max and PIP (P diff ) ranged between 5 and 20 mbar (median = 11 mbar) despite a protocol to keep P max 5 mbar above the "working PIP". P max was reached in 5.2% of inflations. Computational modelling demonstrated that had P diff been kept at 5 mbar more consistently, >10% of inflations would have reached P max . The frequency of low-tidal volume alarms showed inverse correlation with P diff ., Conclusions: It is difficult to implement a simple P max strategy due to variability of PIP. Setting P max close to the "working PIP" limits VT delivery and triggers frequent alarms.

Face mask ventilation provides respiratory support to newly born or sick infants. It is a challenging technique and difficult to ensure that an appropriate tidal volume is delivered because large and variable leaks occur between the mask and face; airway obstruction may also occur. Technique is more important than the mask shape although the size must appropriately fit the face. The essence of the technique is to roll the mask on to the face from the chin while avoiding the eyes, with a finger and thumb apply a strong even downward pressure to the top of the mask, away from the stem and sloped sides or skirt of the mask, place the other fingers under the jaw and apply a similar upward pressure. Preterm infants require continuous end-expiratory pressure to facilitate lung aeration and maintain lung volume. This is best done with a T-piece device, not a self-inflating or flow-inflating bag., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background: A spontaneous breathing trial (SBT) has been used to guide suitability of extubation in VLBW infants. Respiratory variability (RV) has been used to assess extubation readiness in adults but was never investigated in preterms. The combination of a SBT and RV may further improve prediction of successful extubation., Study Design: Using data previously collected during the SBT, the following respiratory variables were analysed: inspiratory time (T(I)), expiratory time (T(E)), T(I)/total breath time, tidal volume (V(T)) and mean inspiratory flow (V(T)/T(I)). RV was quantified using time-domain analysis for each respiratory variable and expressed as a variability index (VI). The sensitivity, specificity, positive and negative predictive values (PPV and NPV) of the SBT, each VI and combined SBT+VI were calculated. Extubation failure was defined as need of re-intubation within 72 h., Results: A total of 44 infants were included. Successfully (n=36) and unsuccessfully (n=8) extubated infants had similar baseline characteristics and number of breaths analysed. VI for V(T)/T(I)was significantly decreased in the failure group. The combination of the SBT and VI of either T(I)or V(T)were the most accurate predictors of successful extubation with a sensitivity of 100% and specificity of 75% and a PPV and NPV for extubation success of 95% and 100%, respectively., Conclusions: A significant decrease in V(T)/T(I)variability occurred in infants requiring re-intubation. The combination of a SBT failure and decreased variability in T(I)or V(T)was highly predictive of failure. This combination is promising but requires prospective evaluation in a larger population.

This article shows that volume-targeted ventilation is physiologically more logical than pressure-limited ventilation, and is associated with a reduced risk of pneumothorax, hypocarbia, duration of ventilation, death or bronchopulmonary dysplasia, and severe intraventricular hemorrhage. Therefore, it should now be adopted as the main mode for mechanical ventilation of preterm neonates., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Objective: The objective of this study is to compare the effects of back-up ventilation rates (BURs) on triggered inflations and patient cardiorespiratory stability during assist-control/volume guarantee ventilation (AC/VG)., Study Design: This study is a randomized crossover trial conducted in a neonatal unit in an Australian tertiary NICU. In all, 26 stable preterm infants on AC/VG ventilation were studied at BUR settings of 30, 40 and 50 min(-1). Inflation rate, triggering and cardiorespiratory measures of patient stability were compared during 20 min epochs with 10 min washout periods., Result: The 26 infants studied were median (inter-quartile range) gestational age 27 (26, 30) weeks, birth weight 0.84 (0.75, 1.14) kg and FiO(2) 0.24 (0.21, 0.31) and age 6 (4, 19) days. At BURs of 30, 40 and 50, the proportions of inflations, which were triggered, were mean (s.d.) 85% (11), 75% (19) and 61% (25); P<0.01 for all comparisons. Total delivered inflation rates were 56 (8), 58 (9) and 62 (8) min(-1), respectively. Cardiorespiratory parameters did not vary between the settings., Conclusion: Using a lower BUR allows greater triggering of ventilator inflations. Cardiorespiratory parameters including CO(2) levels were stable at all rates.

A recent systematic review and meta-analysis shows that volume-targeted ventilation (VTV) compared with pressure-limited ventilation (PLV) reduce death and bronchopulmonary dysplasia, pneumothorax, hypocarbia and severe cranial ultrasound abnormalities. In this paper, we present published research and our experience with volume guarantee (VG) ventilation, a VTV mode available on the Dräger Babylog 8000plus and VN500 ventilators. The VG algorithm measures the expired tidal volume (V(T)) for each inflation and adjusts the peak inflating pressure for the next inflation to deliver a V(T) set by the clinician. The advantage of controlling expired V(T) is that this is less influenced by endotracheal tube leak than inspired V(T). VG ventilation can be used with an endotracheal tube leak up to ∼50%. Initial set V(T) for infants with respiratory distress syndrome should be 4.0 to 5.0 ml kg(-1). The set V(T) should be adjusted to maintain normocapnoea. Setting the peak inflating pressure limit well above the working pressure is important to enable the ventilator to deliver the set V(T), and to avoid frequent alarms. This paper provides a practical guide on how to use VG ventilation.

A sustained inflation (SI) facilitates lung aeration after birth but may impair the neonatal cardiovascular transition. We aimed to determine the effect of an initial SI on pulmonary arterial and carotid blood flow (PBF and CBF) after preterm birth. Fetal sheep were instrumented at ∼ 122 d of gestation (d). Lambs were delivered at ∼ 127 d and received either an initial SI (40 cm H2O for 1 min or until a volume of 20 mL/kg was administered) followed by ventilation for 30 min (SI; n = 7) or ventilation for 30 min (non-SI; n = 6). At 10 min after ventilation onset, inspired O2 content increased from 21 to 100% for 10 min. PBF, CBF, pulmonary arterial and carotid pressures, tidal volume, and inspiratory pressures were recorded. PBF was greater during the SI (p < 0.05) but thereafter was similar between groups. Non-SI lambs were hypoxemic and had higher CBF than SI lambs (p < 0.05). Cerebral oxygen delivery was constant in SI lambs but increased ∼ 4-fold in non-SI lambs during ventilation with 100% O2 (p < 0.05). Lung compliance and respiratory status were better in SI than non-SI lambs (p < 0.05). A SI improved lung function without adverse circulatory effects, seemed to stabilize neonatal cerebral O2 delivery, and may protect against cerebral hyperoxia.

Background: Neonatal resuscitation guidelines do not specify the gas flow rate during mask ventilation., Aim: Investigating the effect of gas flow rates on pressures, volumes delivered and mask leak., Methods: Flow 5 and 10 liters/min were tested. In study part 1, pressure ranges were measured when ventilating an intubated manikin with a Neopuff®. In study part 2, pediatric staff mask-ventilated a manikin (peak inflation pressure (PIP) 30 cm H(2)O, positive end expiratory pressure (PEEP) 5 cm H(2)O). We measured pressures, expired tidal volume (V(Te)) and mask leak., Results: Study part 1:an intubated manikin was ventilated with flow 5 versus 10 liters/min: range in PEEP was 0.4-3.6 and 2-14 cm H(2)O, respectively, maximum PIP was 73 cm H(2)O with both flow rates. Study part 2: when mask ventilation was given with flow 5 versus 10 liters/min: leak decreased (24% (8-85) vs. 80% (34- 94); p < 0.0001), V(Te) increased (6.7 (5.1-7.8) vs. 4.7 (2.4-7.0) ml; p < 0.001), PEEP decreased (3.1 (0.8) vs. 3.7 (0.7) cm H(2)O; p < 0.001), PIP was similar (28.1 (2.7) vs. 28.0 (2.3) cm H(2)O; NS). Large leaks decreased V(Te) and PEEP during both flow rates, PIP only with flow 5 liters/min., Conclusion: A low flow rate during neonatal mask ventilation may be a good alternative approach in reducing mask leak, provided that inflation time and flow rate warrants set pressures. Only large leaks seem to influence delivered pressures and volumes. Before resuscitation guidelines are advised, more studies on gas flow rates are needed., (Copyright © 2010 S. Karger AG, Basel.)

Background: Some national resuscitation guidelines advocate using sustained initial inflations (2-3 s) for babies requiring resuscitation. Inflation times ≥10 s have been used for preterm infants., Objectives: This study examines the ability of operators of varying experience to provide a sustained inflation using three different manual ventilation devices., Methods: We compared a self-inflating bag, a flow-inflating bag and a pressure-limited T-piece device. Fifty clinical staff members from five professional groups gave a sustained inflation with a target peak pressure of 30 cm H2O and target duration of 10 s to an internal leak-free manikin. We measured peak inflating pressure (PIP) and mean inflating pressure (MIP) during the sustained inflation, and the duration of inflating pressure (IP) >20 and 25 cm H2O., Results: Median (IQR) duration of IP >25 cm H2O was: self-inflating bag 2.5 s (0.8-5.7), flow-inflating bag 10.6 s (8.4-12.9) and the T-piece 10.7 s (8.9-11.9). There was a weak correlation between experience using a self-inflating bag and longer inflation times (R = 0.290, p = 0.041). When compared with the T-piece, the flow-inflating bag had lower mean MIP (27.0 ± 1.8 vs. 28.8 ± 2.0 cm H2O) and higher mean PIP (32.3 ± 3.7 vs. 29.8 ± 1.8 cm H2O). There were no differences in performance between operator groups., Conclusion: The T-piece provided consistent PIP during a single 10 s sustained inflation with less variation in pressure compared with the flow-inflating bag. Sustained inflations >3 s were difficult to achieve with a self-inflating bag., (Copyright © 2011 S. Karger AG, Basel.)

Background: The onset of ventilation at birth decreases pulmonary vascular resistance (PVR) resulting in a large increase in pulmonary blood flow (PBF). As the large cross sectional area of the pulmonary vascular bed develops late in gestation, we have investigated whether the ventilation-induced increase in PBF is reduced in immature lungs., Methods: Surgery was performed in fetal sheep at 105 d GA (n = 7; term ~147 d) to insert an endotracheal tube, which was connected to a neonatal ventilation circuit, and a transonic flow probe was placed around the left pulmonary artery. At 110 d GA, fetuses (n = 7) were ventilated in utero (IUV) for 12 hrs while continuous measurements of PBF were made, fetuses were allowed to develop in utero for a further 7 days following ventilation., Results: PBF changes were highly variable between animals, increasing from 12.2 ± 6.6 mL/min to a maximum of 78.1 ± 23.1 mL/min in four fetuses after 10 minutes of ventilation. In the remaining three fetuses, little change in PBF was measured in response to IUV. The increases in PBF measured in responding fetuses were not sustained throughout the ventilation period and by 2 hrs of IUV had returned to pre-IUV control values., Discussion and Conclusion: Ventilation of very immature fetal sheep in utero increased PBF in 57% of fetuses but this increase was not sustained for more than 2 hrs, despite continuing ventilation. Immature lungs can increase PBF during ventilation, however, the present studies show these changes are transient and highly variable.

The effect of inflation length on lung aeration pattern, tidal volumes, and functional residual capacity (FRC) immediately after birth was investigated. Preterm rabbits (28 d), randomized into four groups, received a 1-, 5-, 10-, or 20-s inflation (SI) followed by ventilation with 5 cm H2O end-expiratory pressure. Gas volumes were measured by plethysmography and uniformity of lung aeration by phase contrast x-ray imaging for 7 min. The first inspiratory volume significantly (p < 0.001) increased with inflation duration from a median (IQR) of 0.2 (0.1-3.1) mL/kg for 1-s inflation to 23.4 (19.3-30.4) mL/kg for 20-s SI. The lung was uniformly aerated, and the FRC and tidal volume fully recruited after 20-s SI. A 10-s SI caused a higher FRC (p < 0.05) at 7 min, and a 20-s SI caused a higher FRC (p < 0.05) at 20 s and 7 min than a 1- or 5-s SI. The mean (SD) time for 90% of the lung to aerate was 14.0 (4.1) s using 35 cm H2O peak inflation pressure. In these rabbits, 10- and 20-s SI increased the inspiratory volume and produced a greater FRC, and a 20-s SI uniformly aerated the lung before ventilation started.

The effect of a 20 s sustained inflation (SI) and positive end-expiratory pressure (PEEP) on functional residual capacity (FRC) formation at birth were investigated. Preterm rabbit pups (28 d) were randomized at birth into four groups (n = 6 for each): 1) SI, PEEP 5 cm H2O, 2) no SI, PEEP 5 cm H2O, 3) no SI + no PEEP, 4) SI + no PEEP. FRC and tidal volume (Vt) were measured by plethysmography and uniformity of lung aeration by phase contrast x-ray imaging. Ventilation with a SI and PEEP uniformly aerated the lung and Vt and FRC were recruited by the first tidal inflation. Ventilation without a SI, with PEEP, gradually recruited Vt and FRC with each inflation but aeration was not uniform. Ventilation without a SI or PEEP, gradually recruited Vt, but no FRC. Ventilation with a SI, without PEEP, uniformly aerated the lung and recruited Vt but no FRC. FRC was greater with SI (p = 0.006) during the first minute, but was larger with PEEP than without PEEP throughout the first 7 min (p < 0.0005). Effects of PEEP and SI were additive. In ventilated preterm rabbits at birth, combining a SI and PEEP improved FRC formation and uniformity of lung aeration, but PEEP had the greatest influence.

Background: Bronchopulmonary dysplasia (BPD) is closely associated with ventilator-induced lung injury (VILI) in very preterm infants. The greatest risk of VILI may be in the immediate period after birth, when the lungs are surfactant deficient, still partially filled with liquid and not uniformly aerated. However, there have been very few studies that have examined this immediate post-birth period and identified the initial injury-related pathways that are activated. We aimed to determine if the early response genes; connective tissue growth factor (CTGF), cysteine rich-61 (CYR61) and early growth response 1 (EGR1), were rapidly induced by VILI in preterm lambs and whether ventilation with different tidal volumes caused different inflammatory cytokine and early response gene expression., Methods: To identify early markers of VILI, preterm lambs (132 d gestational age; GA, term approximately 147 d) were resuscitated with an injurious ventilation strategy (V(T) 20 mL/kg for 15 min) then gently ventilated (5 mL/kg) for 15, 30, 60 or 120 min (n = 4 in each). To determine if early response genes and inflammatory cytokines were differentially regulated by different ventilation strategies, separate groups of preterm lambs (125 d GA; n = 5 in each) were ventilated from birth with a V(T) of 5 (VG5) or 10 mL/kg (VG10) for 135 minutes. Lung gene expression levels were compared to levels prior to ventilation in age-matched control fetuses., Results: CTGF, CYR61 and EGR1 lung mRNA levels were increased approximately 25, 50 and 120-fold respectively (p < 0.05), within 30 minutes of injurious ventilation. VG5 and VG10 caused significant increases in CTGF, CYR61, EGR1, IL1- , IL-6 and IL-8 mRNA levels compared to control levels. CTGF, CYR61, IL-6 and IL-8 expression levels were higher in VG10 than VG5 lambs; although only the IL-6 and CYR61 mRNA levels reached significance., Conclusion: CTGF, CYR61 and EGR1 may be novel early markers of lung injury and mechanical ventilation from birth using relatively low tidal volumes may be less injurious than using higher tidal volumes.

Objective: To describe the interaction of spontaneous breaths, manual ventilation, and tidal volumes (V(T)) during stabilization of infants with congenital diaphragmatic hernia (CDH) in the delivery room., Study Design: We studied infants with CDH receiving respiratory support at birth. Airway pressure, flow, and volume were measured, and each breath or inflation was analyzed. Each V(T) was classified as a manual inflation, a spontaneous breath, or a spontaneous breath coinciding with manual inflation on the basis of the timing of the pressure and flow waves., Results: Twelve infants had 2957 breaths suitable for analysis, with spontaneous breathing in 11 infants (92%). The mean (+/-SD) proportion of manual inflations was 41% (+/-24%), spontaneous breaths 43% (+/-25%), spontaneous but coinciding with manual inflation 16% (+/-12%). V(T) was significantly different for spontaneous breaths (3.8 +/- 1.9 mL/kg), spontaneous breaths coinciding with manual inflation (4.7 +/- 2.5 mL/kg), and manual inflations alone (2.6 +/- 1.6 mL/kg)., Conclusions: Most infants with CDH breathed spontaneously, and manual ventilation was mostly asynchronous. We observed large differences in tidal volumes between spontaneous breaths, manual inflations, or where these coincided, with manual inflations having the lowest V(T). Monitoring the respiratory pattern of these infants could improve respiratory support.

Objectives: To compare change in lung volume (DeltaV(L)), using respiratory inductive plethysmography, time to recover pre-suction lung volume (t(rec)) and the cardiorespiratory disturbances associated with open suction (OS) and closed suction (CS) in ventilated infants., Design: Randomised blinded crossover trial., Setting: Neonatal intensive care unit., Patients: Thirty neonates, 20 receiving synchronised intermittent mandatory ventilation (SIMV) and 10 high-frequency oscillatory ventilation (HFOV, four receiving muscle relaxant)., Interventions: OS and CS were performed, in random order, on each infant using a 6FG catheter at -19 kPa for 6 seconds and repeated after 1 minute., Outcome Measures: DeltaV(L), oxygen saturation (Spo(2)) and heart rate were continuously recorded from 2 minutes before until 5 minutes after suction. Lowest values were identified during the 60 seconds after suction., Results: Variations in all measures were seen during CS and OS. During SIMV no differences were found between OS and CS for maximum DeltaV(L) or t(rec); mean (95% CI) difference of 3.5 ml/kg (-2.8 to 9.7) and 4 seconds (-5 to 13), respectively. During HFOV t(rec) was longer during OS by 13 seconds (0 to 27) but there was no difference in the maximum DeltaV(L) of 0.1 mV (-0.02 to 0.22). A small reduction in SpO(2) with CS in the SIMV group mean difference 6% (2.1 to 9.8) was the only significant difference in physiological measurements., Conclusions: Both OS and CS produced transient variable reductions in heart rate and Spo(2). During SIMV there was no difference between OS and CS in DeltaV(L) or t(rec). During HFOV there was no difference in DeltaV(L) but a slightly longer t(rec) after OS.

Endotracheal tube (ETT) suction is the most frequently performed invasive procedure in ventilated newborn infants and is associated with adverse effects related to negative tracheal pressure. We aimed to measure suction catheter gas flow and intratracheal pressure during ETT suction of a test lung and develop a mathematical model to predict tracheal pressure from catheter and ETT dimensions and applied pressure. Tracheal pressure and catheter flow were recorded during suction of ETT sizes 2.5-4.0 mm connected to a test lung with catheters 5-8 French Gauge and applied pressures of 80-200 mm Hg. The fraction of applied pressure transmitted to the trachea was calculated for each combination, and data fitted to three nonlinear models for analysis. Tracheal pressure was directly proportional to applied pressure (r = 0.82-0.99), and catheter flow fitted a turbulent flow model (R = 0.85-0.96). With each ETT, increasing catheter size resulted in greater catheter flow (p < 0.0001) and thus lower intratracheal pressure (p < 0.0001). The fraction of applied pressure transmitted to the trachea was accurately modeled using ETT and catheter dimensions (R = 0.98-0.99). Negative tracheal pressure during in vitro ETT suction is directly proportional to applied pressure. This relationship is determined by ETT and catheter dimensions.

Background: Techniques of positioning and holding neonatal face masks vary. Studies have shown that leak at the face mask is common and often substantial irrespective of operator experience., Aims: (1) To identify a technique for face mask placement and hold which will minimise mask leak. (2) To investigate the effect of written instruction and demonstration of the identified technique on mask leak for two round face masks., Method: Three experienced neonatologists compared methods of placing and holding face masks to minimise the leak for Fisher & Paykel 60 mm and Laerdal size 0/1 masks. 50 clinical staff gave positive pressure ventilation to a modified manikin designed to measure leak at the face mask. They were provided with written instructions on how to position and hold each mask and then received a demonstration. Face mask leak was measured after each teaching intervention., Results: A technique of positioning and holding the face masks was identified which minimised leak. The mean (SD) mask leaks before instruction, after instruction and after demonstration were 55% (31), 49% (30), 33% (26) for the Laerdal mask and 57% (25), 47% (28), 32% (30) for the Fisher & Paykel mask. There was no significant difference in mask leak between the two masks. Written instruction alone reduced leak by 8.8% (CI 1.4% to 16.2%) for either mask; when combined with a demonstration mask leak was reduced by 24.1% (CI 16.4% to 31.8%)., Conclusion: Written instruction and demonstration of the identified optimal technique resulted in significantly reduced face mask leak.

Background: Positive pressure ventilation (PPV) via a face mask is an important skill taught using manikins. There have been few attempts to assess the effectiveness of different face mask designs., Aim: To determine whether leak at the face mask during simulated neonatal resuscitation differed between a new round mask design and the current most widely used model., Method: 50 participants gave PPV to a modified manikin designed to measure leak at the face mask. Leak was calculated from the difference between the inspired and expired tidal volumes., Results: Mask leak varied widely with no significant difference between devices; mean (SD) percentage leak for the Laerdal round mask was 55% (31) and with the Fisher & Paykel mask it was 57% (25)., Conclusion: We compared a new neonatal face mask with an established design and found no difference in leak. On average the mask leak was >50% irrespective of operator experience or technique.

Background: During volume guarantee (VG) ventilation the peak inflating pressure (PIP) for each ventilator inflation is adjusted to ensure the expired tidal volume (V(Te)) is close to the set V(Te). Differences in the PIP between inflations triggered by the infant's inspirations and untriggered inflations are seen., Aim: To investigate the effects of triggered and untriggered inflations on PIP and V(Te)., Methods: Neonates were ventilated with the Dräger Babylog 8000 using assist control (synchronous intermittent positive pressure ventilation) and VG modes. Continuous recordings of ventilator pressures and tidal volumes were made at 200 Hz for 10 minutes., Results: In 10 infants, 6540 inflations were analysed, of which 4052 (62%) were triggered. Triggered inflations had a significantly lower mean (SD) PIP than untriggered inflations: 12.9 (4.9) vs 17.0 (3.3) cm H2O, (p<0.001). Despite this, there was no significant difference in the V(Te) of each type of inflation (103% and 101% of the set V(Te), respectively). When a triggered inflation was immediately preceded or followed by an untriggered inflation the PIP changed by about 5 cm H2O. Between adjacent inflations of the same type, the change in PIP was less than 3 cm H2O: for triggered inflations it was 0.11 (1.50) cm H2O and for untriggered inflations 0.06 (1.53) cm H2O., Conclusion: During VG ventilation with the Dräger Babylog 8000 the PIP was 4 cm H2O lower during triggered inflations than untriggered inflations, although the expired tidal volumes were similar.

Aims: To determine whether using a respiratory function monitor alters clinicians' choice of ventilator settings, tidal volumes or blood gases in the first 48 h of ventilation., Methods: Clinicians were trained to use a respiratory function monitor to optimize neonatal ventilation. Thirty-five infants, weighing < 2 kg, treated with the Infant Star ventilator were randomized to have a respiratory function monitor display visible or concealed. All reasons for altering ventilator settings were noted. Data on ventilator parameters and clinical care were collected hourly. The primary outcome was the mean peak pressure used during the first 48 h., Results: There were no statistically significant differences in peak pressures, tidal volumes or arterial carbon dioxide levels between the two groups., Conclusions: Using the Florian respiratory function monitor in the first 48 h of ventilation with the Infant Star ventilator did not alter the choice of ventilator settings, tidal or minute volumes or arterial blood gases. Possible explanations for this result include lack of power due to the small numbers recruited and bias due to the unblinded nature of the trial.

Objective: Postnatal corticosteroid therapy is controversial. The aim of this study was to determine the short-term effects of low-dose dexamethasone treatment among chronically ventilator-dependent neonates., Methods: Very preterm (gestational age: <28 weeks) or extremely low birth weight (birth weight: <1000 g) infants who were ventilator dependent after the first 1 week of life were eligible and were assigned randomly to receive masked dexamethasone (0.89 mg/kg over 10 days) or saline placebo. Data on ventilator and oxygen requirements and deaths were recorded., Results: Seventy infants were recruited from 11 centers, at a median age of 23 days. More infants were extubated successfully by 10 days of treatment in the dexamethasone group (60%, 21 of 35 patients) than in the control group (12%, 4 of 34 patients) (odds ratio [OR]: 11.2; 95% confidence interval [CI]: 3.2-39.0). Ventilator and oxygen requirements improved substantially, and the duration of intubation was shorter. There was little evidence for a reduction in either the mortality rate (dexamethasone group: 11%; control group: 20%; OR: 0.52; 95% CI: 0.14-1.95) or the rate of oxygen dependence at 36 weeks (dexamethasone group: 85%; control group: 91%; OR: 0.58; 95% CI: 0.13-2.66). There were no obvious effects of low-dose dexamethasone on blood glucose concentrations, blood pressure, or other complications. No infant experienced intestinal perforation., Conclusions: Low-dose dexamethasone treatment after the first 1 week of life clearly facilitates extubation and shortens the duration of intubation among ventilator-dependent, very preterm/extremely low birth weight infants, without any obvious short-term complications. Combined with recent evidence that infants at very high risk of bronchopulmonary dysplasia may benefit in the long term, our study reopens debate regarding the role of low-dose, late postnatal, corticosteroid therapy.

In mature lungs, elevated positive end-expiratory pressure (PEEP) reduces pulmonary blood flow (PBF) and increases pulmonary vascular resistance (PVR). However, the effect of PEEP on PBF in preterm infants with immature lungs and a patent ductus arteriosus is unknown. Fetal sheep were catheterized at 124 days of gestation (term approximately 147 days), and a flow probe was placed around the left pulmonary artery to measure PBF. At 127 days, lambs were delivered and ventilated from birth with a tidal volume of 5 ml/kg and 4-cmH(2)O PEEP; PEEP was changed to 0, 8, and 12 cmH(2)O in random order, returning to 4 cmH(2)O between each change. Increasing PEEP from 4 to 8 cmH(2)O and from 4 to 12 cmH(2)O decreased PBF by 20.5 and 41.0%, respectively, and caused corresponding changes in PVR; reducing PEEP from 4 to 0 cmH(2)O did not affect PBF. Despite decreasing PBF, increasing PEEP from 4 to 8 cmH(2)O and 12 cmH(2)O improved oxygenation of lambs. Increasing and decreasing PEEP from 4 cmH(2)O significantly changed the contour of the PBF waveform; at a PEEP of 12 cmH(2)O, end-diastolic flow was reduced by 82.8% and retrograde flow was reestablished. Although increasing PEEP improves oxygenation, it adversely affects PBF and PVR shortly after birth, alters the PBF waveform, and reestablishes retrograde flow during diastole.

Background: In volume guarantee ventilation with the Dräger Babylog 8000 ventilator, inspiratory and expiratory flows are monitored and the expiratory tidal volume calculated following each inflation. The pressure for the next inflation is modified to ensure the expired tidal volume is close to the set value., Aim: To investigate interrupted expiration observed during volume guarantee ventilation of spontaneously breathing, ventilated infants., Methods: Spontaneously breathing infants, ventilated with volume guarantee, had recordings of gas flow, ventilator pressures, tidal volume waveforms, oximetry, heart rate, and transcutaneous oxygen and carbon dioxide during 10 minute recordings., Results: A total of 6540 inflations were analysed from 10 infants; 62% were triggered. Two different patterns were found: (1) Normal volume guarantee pattern with 97% of triggered and 91% untriggered inflations. It had a normal expiratory curve and a mean expired tidal volume within 3% of the set volume, but a large variation due to the babies' breathing. (2) A pattern of interrupted expiratory flow after approximately 3% of inflations due to a small inspiration (approximately 1.3 ml/kg) during expiration. This led the ventilator to calculate an inappropriate total expired tidal volume for that inflation and an increase in the pressure for the next inflation., Conclusions: After about 3% of inflations, with volume guarantee ventilation, interruption of the expiration causes an increased pressure for the next inflation of approximately 4.9 cm H2O, compared with normal volume guarantee inflation. The interrupted expiration is most likely to be due to diaphragmatic braking.

Unlabelled: Lindner's study of respiratory management of extremely preterm infants, while not providing a definitive answer, demonstrates that many of the smallest infants can be managed in and beyond the delivery room without intubation and without apparent increased early mortality., Conclusion: These novel techniques deserve further evaluation.

This study reports for the first time the use of a respiratory function monitor in a prospective observational cohort of ventilated babies during transport. All 17 babies achieved target transcutaneous carbon dioxide tension within 15 minutes. Fifteen babies had improved ventilation with changes guided by the respiratory function monitor. The monitor was easy to use and useful.

A total of 450 undiluted and unprocessed tracheal aspirates from 120 intubated infants were examined microscopically for evidence of bronchopulmonary dysplasia and other changes. In 19 infants desquamated sheets of dysplastic epithelium in the fresh aspirate provided an early indication of developing bronchopulmonary dysplasia. Examination of unstained tracheal aspirates can provide, within minutes, information not only about the onset and development of bronchopulmonary dysplasia, but also provide evidence for milk or formula aspiration and for gastro-oesophageal reflux.

Cerebral blood flow velocity was measured using Doppler ultrasonography in 20 babies who weighed less than 2500 g at birth and who were receiving assisted ventilation; their patterns of spontaneous respiration were recorded simultaneously. The babies were induced to breathe synchronously or asynchronously with the ventilator by manipulating the inspiratory and expiratory time settings. The variability of cerebral blood flow velocity (coefficient of variation) was calculated from the area of the maximum Doppler frequency shift envelope for 10 cardiac cycles from 211 recordings made on 42 occasions, and was greatest within 12 hours of birth after which it fell progressively over the next 48 hours. Variability of cerebral blood flow velocity was significantly greater when the infants were breathing out of synchrony with the ventilator (median 11%, interquartile range 8-14%) than when they were either apnoeic (median 5%, 3-7%), or breathing synchronously with the ventilator (median 5%, 3-6%).

40 preterm, ventilated infants (gestational ages 24-33 weeks) were entered into a double-blind randomised trial to assess the effect of oral theophylline on lung function and ventilator dependence. Theophylline administration was associated with a significant improvement in compliance (P less than 0.05) and hastened weaning from ventilation (P less than 0.01).

We investigated the effect of increased ventilator rates on the respiratory activity of 17 infants, all actively expiring against the ventilator at conventional rates. Fast rate ventilation was rarely associated with apnoea (3 babies only) and the infant's respiratory efforts even at rates of 120/min had an important effect on tidal exchange. Seven infants altered their respiratory response to breathe in synchrony with the ventilator at 60 breaths/min and 5 maintained this at 120 breaths/min. Nine of the 17 infants continued to actively expire against positive pressure inflation at 60 breaths/min and in two this persisted at 120/min, the remaining 7 infants showed incoordinated breathing at that rate. We conclude that fast rate ventilation appears to have only limited success in suppressing respiratory activity in infants actively expiring against the ventilator.

The stimulating and moderating factors of augmented inspirations provoked by artificial ventilation have been studied in 40 preterm babies on 182 different occasions. Provoked augmented inspirations were demonstrated by recording spontaneous respiratory activity during artificial ventilation by means of an oesophageal balloon and a pneumotachograph. Augmented inspirations were only seen during 18% of the study occasions. The frequency of this reflex was inversely related to the lung compliance as was the ventilator pressure necessary to provoke the augmented inspiration. The inflating volume which stimulated the reflex, when related to body weight, was similar in all the babies. Augmented inspirations were always provoked during the rapid rise in ventilator pressure at the onset of each inflation. Neonates who were recovering from paralysis by pancuronium and others being treated with theophylline both showed an increased frequency of augmented inspirations. It is possible that theophylline could be used to harness this advantageous reflex for the benefit of the ventilated preterm neonate.

Preterm infants who were making expiratory efforts against ventilator inflation were randomised to be paralysed with pancuronium or to receive no paralysing agent during ventilation. Pneumothoraces developed in all 11 unparalysed babies but in only 1 of 11 (p less than 0.0004) of those managed with pancuronium, which had no serious side-effects. In 34 infants excluded from the trial because they were not breathing against the ventilator, no pneumothoraces developed.

Oesophageal pressure measured with an air-filled, thin latex balloon on a 6 French gauge catheter can accurately measure intraoesophageal pressures in ventilated preterm babies. Intraoesophageal pressures and intrapleural pressures are equivalent. Less than 10% of the applied positive ventilator pressure is transmitted to the oesophageal balloon and the intrapleural catheter (intercostal drain). The oesophageal traces show that ventilated babies breath independently of the ventilator. The largest deflections recorded from the oesophageal trace are from spontaneous inspiratory activity. During paralysis with pancuronium spontaneous respiration is inhibited, peristaltic waves are still recorded, and there is little transmitted pressure from the ventilator to the oesophagus or intercostal drain.

The respiratory response to therapeutic lung inflation by artificial ventilation in premature babies has been studied. Both the Hering-Breuer and an augmented inspiratory reflex could be provoked by ventilator inflation in neonates as premature as 25 weeks gestational age. No chemo-receptor control was demonstrated on the presence of these reflexes. Augmented inspirations were only seen in the first five postnatal days regardless of gestational age, but the Hering-Breuer reflex persisted throughout the period of study of 11 days. The frequency of elicitation of augmented inspirations was shown to be inversely related to the dynamic compliance. The relative stimulation of these two respiratory reflexes may explain why some infants are easy to ventilate and others difficult.

We describe a simple technique of neonatal ventilation that induces the neonate to breathe in synchrony with the ventilator. This preserves the beneficial effects of spontaneous respiration (unlike therapeutic paralysis) and reduces potentially harmful interactions between baby and ventilator. The technique uses measurements of the neonate's own respiratory timing.

A technique for monitoring the ventilated neonate's own respiratory efforts using a pneumatic capsule apnoea alarm is described.