Peak Inflation Pressure Research Articles

Performance and safety of volume guarantee ventilation in neonates using the fabian ventilator, a multicenter study.

To evaluate the performance (i.e., agreement between set and measured parameters) and safety (adverse events, device malfunctions, and ventilator alarms) of the fabian HFOi neonatal ventilator in volume guaranteed (VG) mode during conventional ventilation. To analyze the impact of leakage around the endotracheal tube and the set maximum allowed inflating pressure (Pmax). Prospective multicenter observational study. Clinical and ventilator data were collected from 71 infants receiving VG ventilation for ≥12 h in four neonatal intensive care units (NICUs). Ventilator settings, parameters, and alarms were downloaded with 0.5 Hz sampling rate. Data from 4,341 h of ventilation were analyzed. The median (interquartile range, IQR) of the absolute difference between the target and measured expired tidal volume was 0.76 (0.51-1.16) mL/kg. It was less when leak was <50% (median 0.36, IQR: 0.25-0.64 mL/kg, p < .001) and even less when the required peak inflating pressure (PIP) was also below Pmax (median: 0.09 mL/kg, IQR: 0.00-0.16 mL/kg, p < .001). On NICUs setting Pmax higher, tidal volume was maintained significantly closer to target. In 56 patients VG was continued until extubation. Two ventilator malfunctions were reported, none of them resulting in patient harm. "Tidal volume not reached" alarm occurred 32 times hourly, usually lasting for <10 s. The fabian HFOi ventilator maintains tidal volume close to its target, particularly when leak is <50% and when PIP is below Pmax. In most patients VG can be continued until extubation. Despite frequent ventilator alarms, ventilator malfunctions occur very rarely.

An in vitro technique to measure resistance to compression and kinking of endotracheal tubes.

During intraoperative care, ventilatory parameters including peak inflating pressure (PIP) and exhaled tidal volumes are continuously monitored to assess changes in respiratory resistance and compliance. Changes in these parameters, such as an increase in PIP or a decrease in the exhaled tidal volume, may indicate various pathologic processes that may require immediate attention to prevent inadequate ventilation resulting in hypoxemia or hypercarbia. A kinked endotracheal tube (ETT) may mimic other pathologic processes including bronchospasm, mainstem intubation, or ventilator malfunction. As newer ETTs are developed, a key factor in their design should be resistance to kinking or occlusion due to patient positioning. The current project developed and describes the process for using a repeatable in vitro mechanical test to determine resistance to kinking by an ETT. The mechanical testing procedure can be used to determine the compression force and distance required to kink an ETT under different conditions including temperature. The force required to induce devastating kink failure was lower during heated testing conditions. The addition of airflow through the ETTs during compression testing confirms the occurrence of airway obstruction at approximately the same time a mechanical kink is observed on the force-versus-distance curves. These procedures may be used to characterize and evaluate ETT designs under in vitro conditions mimicking those in the clinical practice.

Comparison of positive pressure ventilation devices during compliance changes in a neonatal ovine model.

To compare tidal volume (VT) delivery with compliance at 0.5 and 1.5 mL/cmH2O using four different ventilation (PPV) devices (i.e., self-inflating bag (SIB), T-Piece resuscitator, Next Step (a novel Neonatal Resuscitator), and Fabian ventilator (conventional neonatal ventilator) using a neonatal piglet model. Randomized experimental animal study using 10 mixed-breed neonatal piglets (1-3 days; 1.8-2.4 kg). Piglets were anesthetized, intubated, instrumented, and randomized to receive positive pressure ventilation (PPV) for one minute with a SIB with or without a respiratory function monitor (RFM), T-Piece resuscitator with or without an RFM, Next Step, and Fabian Ventilator with both compliance levels. Compliance changes were achieved by placing a wrap around the piglets' chest and tightened it. Our primary outcome was targeted VT delivery of 5 mL/kg at 0.5 and 1.5 mL/cmH2O lung compliance. At 0.5 mL/cmH2O compliance, the mean(SD) expired VT with the Next Step was 5.1(0.2) mL/kg compared to the Fabian 4.8(0.5) mL/kg, SIB 8.9(3.6) mL/kg, SIB + RFM 4.5(1.8) mL/kg, T-Piece 7.4(4.3) mL/kg, and T-Piece+RFM 6.4(3.1) mL/kg. At 1.5 mL/cmH2O compliance, the mean(SD) expired VT with the Next Step was 5.2(0.6) mL/kg compared to the Fabian 4.4(0.7) mL/kg, SIB 12.1(5.3) mL/kg, SIB + RFM 9.4(3.9) mL/kg, T-Piece 8.6(1.5) mL/kg, and T-Piece+RFM 6.5 (1.6) mL/kg. The Next Step provides consistent VT during PPV, which is comparable to a mechanical ventilator. Current guidelines recommend fixed peak inflation pressure in resuscitation, linked to lung and brain injury. The Next Step Neonatal Resuscitator, a cost-effective device, offers volume-targeted positive pressure ventilation with consistent tidal volumes. With two different compliances, the Next Step Neonatal Resuscitator delivered a consistent tidal volume which was similar to a mechanical ventilator. The Next Step Neonatal Resuscitator outperformed self-inflating bags and T-Pieces in delivering targeted tidal volumes. The Next Step Neonatal Resuscitator could be an alternative ventilation device for neonatal resuscitation.

Sustained pharyngeal inflation in infant airway-Flexible bronchoscopy measurements.

Sustained pharyngeal inflation (SPI) with pharyngeal oxygen flow and nasal closure (PhO2-NC) technique create positive inflation pressure in the airway. This study measured the peak inflation pressure (PIP) levels and image changes with SPI-assisted flexible bronchoscopy (SPI-FB) and compared the effects in the pharyngeal space and mid-tracheal lumen. This prospective study enrolled 20 participants aged 6 months to 3 years. Each participant underwent sequential SPI-FB of four different durations (0, 1s, 3s, and 5s) for three cycles. We used a 3.8 mm OD flexible bronchoscope to measure and analyze PIP levels, images, and lumen dimension scores. A total of 480 data were collected. The mean (SD) age and body weight were 12.0 (11.5) months and 7.8 (7.5) kg, respectively. The mean (IQR) PIPs were 4.2 (2.0), 18.5 (6.1), 30.6 (13.5), and 46.1 (25.0) cmH2O in the pharynx and 5.0 (1.6), 17.5 (6.5), 28.0 (12.3), 46.0 (28.5) cmH2O in the mid-trachea at SPI durations of 0, 1s, 3s, and 5s, respectively. The PIP levels had a positive correlation (p <0.001) with different SPI durations in both pharynx and trachea, and were nearly identical (p = 0.695, 0.787, and 0.725 at 1s, 3s, and 5s, respectively) at the same duration except the 0 s (p = 0.015). Lumen dimension scores also significantly increased with increasing SPI durations (p <0.05) in both locations. The identified lesions significantly increased as PIP levels increased (p <0.001). Conclusion: SPI-FB using PhO2-NC with durations up to 3s is safe and informative technique that provides controllable PIP, dilates airway lumens, and benefits lesion detection in the pharyngeal space and mid-tracheal lumen.

A neonatal in-vitro study on the effect of the inflation pressure on end-tidal carbon dioxide levels.

Describing the association of the peak inflation pressure (PIP) with end-tidal carbon dioxide (ETCO2) is a prerequisite for the development of closed loop ventilation in neonatal intensive care. We aimed to develop an in-vitro system to study this relationship. A ventilator was connected to a test lung, supplied with a stable CO2 concentration from a cylinder. The PIP was altered and the change in ETCO2 per unit of PIP was calculated in three models mimicking respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD) and viral bronchiolitis. The median (IQR) change in ETCO2 per unit of PIP was 0.23(0.13-0.38) kPa/cmH2O, using 138 paired measurements of PIP and ETCO2. The median (IQR) change in ETCO2 per unit of PIP, was higher when starting at an ETCO2>6kPa [0.43(0.33-0.58) kPa/cmH2O] compared to starting at an ETCO2<6kPa [0.14(0.08-0.20) kPa/cmH2O, p<0.001]. The median (IQR) change in ETCO2 per unit of PIP, was larger in the model of RDS [0.33(0.13-0.51) kPa/cmH2O] compared to the BPD [0.23(0.13-0.33) kPa/cmH2O, p=0.043] and the bronchiolitis models [0.15(0.10-0.31) kPa/cmH2O, p=0.017]. The change in ETCO2 in response to increasing PIP was larger for higher ETCO2 values and in a model simulating neonatal RDS, compared to BPD and bronchiolitis.

Volume-targeted mask ventilation during simulated neonatal resuscitation

ObjectiveMask positive pressure ventilation (PPV) in the delivery room is routinely delivered with set peak inflation pressures. To aid mask PPV, stand-alone respiratory function monitors (RFMs) have been used in...

Pressure versus volume-controlled ventilation with BASKA mask airway in laparoscopic cholecystectomy: A randomized clinical study

ABSTRACT Background The best ventilation mode that suits with LMAs is still unclear. In this study, we investigated the ventilatory performance of Baska masks in patients who underwent elective laparoscopic cholecystectomy under general anaesthesia and pneumoperitoneum with either volume-controlled ventilation (VCV) or pressure-controlled ventilation (PCV) mode. Methods Fifty-Six patients with ASA I – II, who underwent laparoscopic cholecystectomy, were randomly classified into VCV (n = 28) and PCV (n = 28) groups. The lung was ventilated with a tidal volume of 8 ml/kg in the VCV group. It was ventilated initially using an inflating pressure that delivered a tidal volume of 8 ml/kg with a maximum of 35 cmH2O in the PCV group. The primary outcome was the intraoperative oropharyngeal leak pressure (OLP) of the Baska mask. Secondary outcomes were intraoperative lung mechanics, arterial carbon dioxide levels, and perioperative adverse effects. Results After pneumoperitoneum inflation, the OLP, peak inflation pressure (PIP), mean pressure (Pmean), PaCO2, and end-tidal CO2 significantly increased, and the calculated dynamic compliance significantly decreased in both ventilation modes. All variables partially returned to baseline after pneumoperitoneum deflation. Patients ventilated with PCV mode demonstrated significantly lower PIP and PaCO2 levels but higher dynamic compliance with statistically comparable OLP-PIP difference and higher leak fraction. Conclusion In this study, Patients ventilated with PCV mode showed lower PIP and PaCO2 but higher dynamic compliance, and higher leak fraction. However, both modes investigated provided effective Baska mask ventilation and maintained the OLP throughout the procedure with a statistically comparable OLP-PIP difference.

Novel Neonatal Simulator Provides High-Fidelity Ventilation Training Comparable to Real-Life Newborn Ventilation.

Face mask ventilation of apnoeic neonates is an essential skill. However, many non-paediatric healthcare personnel (HCP) in high-resource childbirth facilities receive little hands-on real-life practice. Simulation training aims to bridge this gap by enabling skill acquisition and maintenance. Success may rely on how closely a simulator mimics the clinical conditions faced by HCPs during neonatal resuscitation. Using a novel, low-cost, high-fidelity simulator designed to train newborn ventilation skills, we compared objective measures of ventilation derived from the new manikin and from real newborns, both ventilated by the same group of experienced paediatricians. Simulated and clinical ventilation sequences were paired according to similar duration of ventilation required to achieve success. We found consistencies between manikin and neonatal positive pressure ventilation (PPV) in generated peak inflating pressure (PIP), mask leak and comparable expired tidal volume (eVT), but positive end-expiratory pressure (PEEP) was lower in manikin ventilation. Correlations between PIP, eVT and leak followed a consistent pattern for manikin and neonatal PPV, with a negative relationship between eVT and leak being the only significant correlation. Airway obstruction occurred with the same frequency in the manikin and newborns. These findings support the fidelity of the manikin in simulating clinical conditions encountered during real newborn ventilation. Two limitations of the simulator provide focus for further improvements.

Sustained pharyngeal inflation on upper airway effects in children-Flexible bronchoscopy measurement.

Sustained pharyngeal inflation (SPI) with pharyngeal oxygen and nose-closure (PhO2 -NC) can create positive peak inflation pressure (PIP) inside the pharyngolaryngeal space (PLS). This study measured and compared the effects of four different SPI durations in the PLS. A prospective study, 20 consecutive children aged between 6 months and 3 years old, scheduled for elective flexible bronchoscopy (FB) suspected positive PLS findings were enrolled. SPI was performed twice in four different durations (0, 1, 3, and 5 s) sequentially in each infant. PIP was measured for each SPI in the pharynx, while simultaneously record images at two locations of the oropharynx and supra-larynx. Patient demographic details, PIP levels, lumen expansion scores, and images of PLS were measured and analyzed. Twenty patients with 40 measurements were collected. The mean (SD) age and weight were 11.6 (9.1) months and 6.8 (2.4) kg, respectively. The measured mean (SD) pharyngeal PIPs were 4.1 (3.3), 21.9 (7.0), 42.2 (12.3), and 65.5 (18.5) cmH2 O at SPI duration of 0, 1, 3, and 5 s, respectively, indicating significant (p<.001) positive correlation. At assigned locations, corresponding PLS images also displayed a significant increase in lumen expansion scores and a number of detected lesions with an increase in SPI duration (p < .004). The mean (SD) procedural time was 5.7 (1.2) min. No study-related complication was noted. FB utilizing PhO2 -NC as SPI of 1-3 s is a simple, less invasive, and valuable ventilation modality. It provides an adequate PIP level to expand the PLS and improve FB performance in children.

Cardiorespiratory effects of NIV-NAVA, NIPPV, and NCPAP shortly after extubation in extremely preterm infants: A randomized crossover trial.

Investigate the cardiorespiratory effects of noninvasive neurally adjusted ventilatory assist (NIV-NAVA), nonsynchronized nasal intermittent positive pressure ventilation (NIPPV), and nasal continuous positive airway pressure (NCPAP) shortly after extubation. Types of noninvasive pressure support and the presence of synchronization may affect cardiorespiratory parameters. Randomized crossover trial. Infants with birth weight (BW) 1250 g or under, undergoing their first planned extubation were randomly assigned to all three modes using a computer-generated sequence. Electrocardiogram and electrical activity of the diaphragm (Edi) were recorded for 30 min on each mode. Analysis of heart rate variability (HRV), diaphragmatic activity (Edi area, breath area, amplitude, inspiratory and expiratory times), and respiratory variability were compared between modes. Twenty-three infants had full data recordings and analysis: Median (IQR) gestational age = 25.9 weeks (25.2-26.4), BW = 760 g (595-900), and postnatal age 7 (4-19) days. There were no differences in HRV between modes. A significantly reduced Edi area and breath amplitude, and increased coefficient of variation (CV) of breath amplitude were observed during NIV-NAVA and NIPPV compared to NCPAP. A higher proportion of assisted breaths (99% vs. 51%; p < .001) provided a higher mean airway pressure (MAP; 9.4 vs. 8.2 cmH2 O; p = .002) with lower peak inflation pressures (PIPs; 14 vs. 16 cmH2 O; p < .001) during NIV-NAVA compared to NIPPV. NIV-NAVA and NIPPV applied shortly after extubation were associated with lower respiratory efforts and higher respiratory variability. These effects were more evident for NIV-NAVA where optimal patient-ventilator synchronization provided a higher MAP with lower PIPs.

Return of Spontaneous Circulation Depends on Cardiac Rhythm During Neonatal Cardiac Arrest in Asphyxiated Newborn Animals.

Objective: Pulseless electrical activity (PEA) occurs in asphyxiated newborn piglets and infants. We aimed to examine whether different cardiac rhythms (asystole, bradycardia, PEA) affects the resuscitation outcomes during continuous chest compressions (CC) during sustained inflations (CC+SI).Design: This study is a secondary analysis of four previous randomized controlled animal trials that compared CC+SI with different CC rate (90 or 120/min), SI duration (20 or 60 s), peak inflation pressure (10, 20, or 30 cmH2O), and oxygen concentration (18, 21, or 100%).Setting and Subjects: Sixty-six newborn mixed breed piglets (1–3 days of age, weight 1.7–2.4 kg) were obtained on the day of experimentation from the University Swine Research Technology Center.Interventions: In all four studies, piglets were randomized into intervention or sham. Piglets randomized to “intervention” underwent both hypoxia and asphyxia, whereas, piglets randomized to “sham” received the same surgical protocol, stabilization, and equivalent experimental periods without hypoxia and asphyxia.Measurements: To compare differences in asphyxiation time, time to return of spontaneous circulation (ROSC), hemodynamics, and survival rate in newborn piglets with asystole, bradycardia or PEA.Main Results: Piglets with PEA (n = 29) and asystole (n = 13) had a significantly longer asphyxiation time and time to ROSC vs. bradycardia (n = 24). Survival rates were similar between all groups. Compared to their baseline, mean arterial pressure and carotid blood flow were significantly lower 4 h after resuscitation in all groups, while being significantly higher in the bradycardia group.Conclusion: This study indicates that cardiac rhythm before resuscitation influences the time to ROSC and hemodynamic recovery after ROSC.

Characterization of Endothelial Cell Loss in Pre-Descemet Endothelial Keratoplasty Graft Preparation.

To characterize the pattern and factors affecting endothelial cell loss (ECL) in pre-Descemet Endothelial Keratoplasty (PDEK) graft preparation. A prospective study was performed to characterize the pattern of ECL and the impact of inflation pressure in PDEK. Donor corneas were randomized to inflation with air versus Optisol GS storage media. PDEK preparation was performed under continuous pressure monitoring. Trypan blue was used to grade the tissue as acceptable (<25% ECL) or unacceptable (≥25% ECL). Rate of unacceptable ECL was correlated with injection media type and inflation pressure. A retrospective study was then performed of all attempted PDEK preparations at Lions Gift of Sight to evaluate impact of donor tissue factors on ECL. Donor age and tissue preservation time were evaluated and correlated with ECL with PDEK bubbling. Twenty-five corneas were tested prospectively. A reticular pattern of ECL that varied in severity occurred with bubbling. There was no difference in peak inflation pressure or mean expansion pressure between air (706.0, 510.7 mm Hg) and Optisol GS (852.9, 653.0 mm Hg). Increasing peak inflation pressure and mean expansion pressure were associated with an increased risk for unacceptable ECL. On retrospective evaluation of 131 attempted PDEKs, only 44.0% of cases with successful bubbles had acceptable endothelium after processing. Increasing donor age and decreasing preservation time were associated with increased rates of acceptable endothelium. PDEK processing can result in a reticular pattern of ECL. Higher inflation pressures are associated with greater ECL. Older donor tissues with shorter preservation times might be preferable for PDEK.

Delivery of Positive End-Expiratory Pressure Using Self-Inflating Bags during Newborn Resuscitation Is Possible Despite Mask Leak

Background: Ventilation is the key intervention to resuscitate non-breathing newborns. Positive end-expiratory pressure (PEEP) may facilitate lung-liquid clearance and help establish functional residual capacity. Objectives: The aim of this study was to describe how mask leak and ventilation rates affect delivered PEEP and tidal volumes during newborn resuscitations using a self-inflating bag with an integrated PEEP valve. Methods: This was an observational study including near-term/term newborns who received bag-mask ventilation (BMV) with a new self-inflating bag with a novel 6 mbar PEEP valve, without external gas flow, between October 1, 2016 and June 30, 2018 in rural Tanzania. Helping Babies Breathe-trained midwives performed most of the resuscitations. Pressures and flow were continuously measured and recorded by resuscitation monitors. Results: In total, 198 newborns with a median gestation of 39 weeks (25th, 75th percentiles 37, 40) and birth weight of 3,100 g (2,580, 3,500) were included. The median delivered PEEP and expired (tidal) volume at different levels of mask leak were 6.0 mbar and 11.3 mL/kg at 0–20% mask leak, 5.5 mbar and 9.3 mL/kg at 20–40%, 5.2 mbar and 7.8 mL/kg at 40–60%, 4.6 mbar and 5.0 mL/kg at 60–80%, and 1.0 mbar and 0.6 mL/kg at 80–100% mask leak. A high ventilation rate (>60/min) nearly halved expired volumes compared to <60/min for 0–60% leak. The BMV rate had a negligible effect on peak inflation pressure (PIP) and PEEP. Conclusions: Mask leak up to 80% did not impair the provision of recommended PEEP or tidal volumes during BMV with a self-inflating bag. High or low ventilation rates did not significantly affect PIP or PEEP. Expired volumes were reduced at ventilation rates >60/min.

Effects of sustained inflation pressure duringneonatal cardiopulmonary resuscitation of asphyxiated piglets.

Sustained inflation (SI) during chest compression (CC = CC+SI) has been recently shown as an alternative method during cardiopulmonary resuscitation in neonates. However, the optimal peak inflation pressure (PIP) of SI during CC+SI to improve ROSC and hemodynamic recovery is unknown. To examine if different PIPs of SI during CC+SI will improve ROSC and hemodynamic recovery in severely asphyxiated piglets. Twenty-nine newborn piglets (1-3 days old) were anesthetized, intubated, instrumented and exposed to 30-min normocapnic hypoxia followed by asphyxia. Piglets were randomized into four groups: CC+SI with a PIP of 10 cmH2O (CC+SI_PIP_10, n = 8), a PIP of 20 cmH2O (CC+SI_PIP_20, n = 8), a PIP of 30 cmH2O (CC+SI_PIP_30, n = 8), and a sham-operated control group (n = 5). Heart rate, arterial blood pressure, carotid blood flow, cerebral oxygenation, and respiratory parameters were continuously recorded throughout the experiment. Baseline parameters were similar between all groups. There was no difference in asphyxiation (duration and degree) between intervention groups. PIP correlated positively with tidal volume (VT) and inversely with exhaled CO2 during cardiopulmonary resuscitation. Time to ROSC and rate of ROSC were similar between piglets resuscitated with CC+SI_PIP_10, CC+SI_PIP_20, and CC+SI_PIP_30 cmH2O: median (IQR) 75 (63-193) sec, 94 (78-210) sec, and 85 (70-90) sec; 5/8 (63%), 7/8 (88%), and 3/8 (38%) (p = 0.56 and p = 0.12, respectively). All piglets that achieved ROSC survived to four hours post-resuscitation. Piglets resuscitated with CC+SI_PIP_30 cmH2O exhibited increased concentrations of pro-inflammatory cytokines interleukin-1β and tumour necrosis factor-α in the frontoparietal cerebral cortex (both p<0.05 vs. sham-operated controls). In asphyxiated term newborn piglets resuscitated by CC+SI, the use of different PIPs resulted in similar time to ROSC, but PIP at 30 cmH2O showed a larger VT delivery, lower exhaled CO2 and increased tissue inflammatory markers in the brain.

T-piece resuscitators: can they provide safe ventilation in a low compliant newborn lung?

BackgroundT-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...

Establishment of functional residual capacity at birth: Observational study of 821 neonatal resuscitations

Aim of the studyEstablishing functional residual capacity (FRC) during positive pressure ventilation (PPV) of apnoeic neonates is critical for survival. This may be difficult due to liquid-filled airways contributing to low lung compliance. The objectives were to describe initial PPV, changes in lung compliance and establishment of FRC in near-term/term neonates ≥36 weeks gestation at birth. MethodsObservational study of all neonatal resuscitations between 01.07.13 and 30.06.18 in a Tanzanian referral hospital. Perinatal events and characteristics were observed and recorded by trained research assistants. PPV were performed using self-inflating bag-masks without positive end-expiratory pressure (PEEP). Ventilation signals (pressure/flow), expired CO2 (ECO2) and heart rate were recorded by resuscitation monitors. Results19,587 neonates were born, 1451 received PPV, of these 821 of median (p25, p75) birthweight 3180 (2844, 3500) grams and gestation 38 (37, 40) weeks had ≥20 ventilations and complete datasets. There was a significant increase in expired volume (from 3.3 to 6.0 ml/kg), ECO2 (0.3–2.4%), lung compliance (0.13–0.19 ml/kg/mbar) and heart rate (109–138 beats/min) over the first 20 PPVs. Inflation volume, time, and peak inflation pressure (PIP) were stable around 12–13 ml/kg, 0.45 s, and 36 mbar, respectively. ConclusionsThe combination of increasing expired volumes, ECO2, and heart rate with decreasing inflation/expired volume ratios and constant PIP, suggests establishment of FRC during the first 20 PPVs in near-term/term neonates using a self-inflating bag-mask without PEEP, the most common device worldwide for ventilating non-breathing neonates. Initial lung compliance is low, and with short inflation times, higher than recommended PIP seem necessary to deliver adequate tidal volumes.

Work of Breathing in Mechanically Ventilated Preterm Neonates.

To compare the imposed work of breathing by means of pressure-time product of the diaphragm in newborn infants receiving different modes of mechanical ventilation. Prospective observational crossover study. Tertiary care neonatal unit. Forty preterm newborns (gestational age ≤ 37 wk) in the phase of weaning from mechanical ventilation. Participants were ventilated in assist control, synchronized intermittent mandatory ventilation, and intermittent mandatory ventilation mode, in a crossover manner. The combination synchronized intermittent mandatory ventilation-pressure support (SIMV-PS) at 50% (SIMV-PS50) and 75% (SIMV-PS75) of the difference between peak inflating and positive end-expiratory pressure, was also applied in a subset of infants (n = 11). Each mode was maintained for 30 minutes. Transdiaphragmatic pressure was obtained by digital subtraction of esophageal from gastric pressure (both measured using a dual pressure-tipped catheter), and pressure-time product of the diaphragm was computed by integration of transdiaphragmatic pressure over inspiratory time. The pressure-time product of the diaphragm was 224.2 ± 112.8 in the intermittent mandatory ventilation mode, 165.8 ± 58.8 in the synchronized intermittent mandatory ventilation mode, and 125.5 ± 61.8 cm H2O × s × min in the assist control mode; all values were significantly different to each other (p < 0.0001). The pressure-time product of the diaphragm difference between assist control and intermittent mandatory ventilation, and assist control and synchronized intermittent mandatory ventilation was negatively related to postmenstrual age (regression coefficient, -0.365; p = 0.020 and -0.341; p = 0.031, respectively). In the SIMV-PS subcohort, the pressure-time product of the diaphragm was significantly higher in the intermittent mandatory ventilation mode as compared with assist control (p < 0.0001) or SIMV-PS75 (p = 0.0027), and in the synchronized intermittent mandatory ventilation mode as compared with assist control (p = 0.0301). In preterm infants, patient-triggered ventilation modalities result in lower work of breathing than intermittent mandatory ventilation, while the assist control mode is also associated with lower pressure-time product of the diaphragm compared with synchronized intermittent mandatory ventilation. The difference in the imposed diaphragmatic workload between these ventilation modalities was inversely related to postmenstrual age, implying that less mature infants benefit more from assist control-based ventilation strategies.

Tidal volume monitoring during initial resuscitation of extremely prematurely born infants.

Background Airway obstruction can occur during facemask (FM) resuscitation of preterm infants at birth. Intubation bypasses any upper airway obstruction. Thus, it would be expected that the occurrence of low expiratory tidal volumes (VTes) would be less in infants resuscitated via an endotracheal tube (ETT) rather than via an FM. Our aim was to test this hypothesis. Methods Analysis was undertaken of respiratory function monitoring traces made during initial resuscitation in the delivery suite to determine the peak inflating pressure (PIP), positive end expiratory pressure (PEEP), the VTe and maximum exhaled carbon dioxide (ETCO2) levels and the number of inflations with a low VTe (less than 2.2 mL/kg). Results Eighteen infants were resuscitated via an ETT and 11 via an FM, all born at less than 29 weeks of gestation. Similar inflation pressures were used in both groups (17.2 vs. 18.8 cmH2O, P = 0.67). The proportion of infants with a low median VTe (P = 0.6) and the proportion of inflations with a low VTe were similar in the groups (P = 0.10), as was the lung compliance (P = 0.67). Infants with the lowest VTe had the stiffest lungs (P < 0.001). Conclusion Respiratory function monitoring during initial resuscitation can objectively identify infants who may require escalation of inflation pressures.

Prediction of prolonged ventilator dependence in preterm infants

Volutrauma is an important factor in the pathogenesis of bronchopulmonary dysplasia (BPD). Our aims were to identify risk factors in the first 24h for prolonged ventilator dependence and assess volume delivery and carbon dioxide levels in infants with evolving BPD. A retrospective study was undertaken of 41 infants born at less than 32weeks of gestational age (GA). A higher tidal volume, minute volume and resistance and a lower GA, birth weight and compliance were associated with a significantly higher risk of ventilator dependence at 28days. The strongest relationships were with birth weight (area under the receiver operating characteristic curve, AUROC = 0.771) and GA (AUROC = 0.813). Tidal volume remained significantly higher after adjusting for GA in those who remained ventilator dependent at 28days. The 18 who remained ventilator dependent at 28days had increased mean carbon dioxide (PCO2) levels with increasing age from a mean of 41mmHg in the first 24h to 65mmHg at 28days PMA (p < 0.001). The increase in PCO2 occurred despite increases in peak inflation pressures (p < 0.001), tidal volumes (p = 0.002) and minute volumes (p < 0.001).Conclusion: These results suggest that initial volutrauma may contribute to the development of chronic ventilator dependence. What is Known: • In prematurely born infants, excessive tidal volumes are important in the pathogenesis of bronchopulmonary dysplasia (BPD), but a tidal volume that is too low will increase the risk of atelectasis, work of breathing and energy expenditure. What is New: • A high tidal volume in the first 24h was associated with an increased risk of ventilator dependence at 28days, which remained significant after adjusting for gestational age. Carbon dioxide levels significantly increased over the first month despite increased pressures and volumes in those who remained ventilator dependent.

New Strategies of Pulmonary Protection of Preterm Infants in the Delivery Room with the Respiratory Function Monitoring.

To investigate if the use of a visible respiratory function monitor (RFM) to use lower tidal volumes (Vts) during positive pressure ventilation (PPV) in the delivery room (DR) reduces the need of surfactant administration and invasive mechanical ventilation during the first 72 hours after birth of preterm infants <32 weeks' gestational age (GA). Infants <32 weeks' GA (n = 106) requiring noninvasive PPV were monitored with a RFM at birth and randomized to visible (n = 54) or masked (n = 52) display on RFM. Pulmonary data were recorded during the first 10 minutes after birth. Secondary analysis stratified patients by GA (<28, 28-29+6, or ≥30 weeks). Median expiratory Vts during inflations were greater in the masked group (7 mL/kg) than in the visible group (5.8 mL/kg; p = 0.001) same as peak inflation pressure (PIP) administered (21.5 vs. 19.7 cmH2O; p < 0.001). Consequently, minute volumes were greater in the masked group (256 vs. 214 mL/kg/min; p < 0.001), with no differences in respiratory rate. These differences were higher in those <30 weeks' GA. There was no difference in the need of surfactant administration or intubation during the first 72 hours of age. Using a RFM in the DR prevents the use of large Vt and PIP during respiratory support inflations, mostly in the more immature newborn infants, but with no other short-term benefits.