Providing PEEP during neonatal resuscitation: which device is best?

Positive Pressure Ventilation in Preterm Infants in the Delivery Room: A Review of Current Practices, Challenges, and Emerging Technologies

BACKGROUND

A major proportion of preterm neonates require positive pressure ventilation (PPV) immediately after delivery. PPV may be administered through a face mask (FM) or nasal prongs. Current literature indicates that either of these are associated with similar outcomes.

SUMMARY

Nonetheless, FM remains the most utilized and the best choice. However, most available FM sizes are too large for extremely preterm infants, which leads to mask leak and ineffective PPV. Challenges to providing effective PPV include poor respiratory drive, complaint chest wall, weak thoracic muscle, delayed liquid clearance, and surfactant deficiency in preterm infants. Mask leak, airway obstruction, poor technique, and inappropriate size are correctable causes of ineffective PPV. Visual assessment of chest rise is often used to assess the efficacy of PPV. However, its accuracy is debatable. Though end tidal CO2 may adjudge the effectiveness of PPV, clinical studies are limited. The compliance of a preterm lung is highly dynamic. The inflating pressure set on T-piece is constant throughout the resuscitation, but the lung volume and dynamics changes with every breath. This leads to huge fluctuations of tidal volume delivery and can trigger inflammatory cascade in preterm infants leading to brain and lung injury. Respiratory function monitoring in the delivery room has potential for guiding and optimizing delivery room resuscitation. This is, however, limited by high costs, complex information that is difficult to interpret during resuscitation, and absence of clinical trials.

KEY MESSAGES

This review summarizes the existing literature on PPV in preterm infants, the various aspects related to it such as the pathophysiology, interfaces, devices utilized to deliver it, appropriate technique, emerging technologies, and future directions.

Positive pressure ventilation at birth

OBJECTIVE

To review the current state of the art of positive pressure ventilation (PPV) during resuscitation FINDINGS: The frequency of PPV during delivery room resuscitation varies across settings and gestational age subgroups. Goal targets and parameters for delivery room PPV remain undefined. The T-piece resuscitator provides the most consistent pressures during PPV and may improve clinical outcomes. The laryngeal mask may be an important alternative interface for PPV, but more data are needed to identify the optimal role of the supraglottic airway during PPV. No objective monitors of PPV have conclusively demonstrated improved outcomes to date.

CONCLUSION

More information, including real-world data from population-based studies, is needed to provide data-driven guidelines for positive pressure ventilation during neonatal transition after birth.

Novel Ventilation Strategies to Reduce Adverse Pulmonary Outcomes

Extremely preterm infants who must suddenly support their own gas exchange with lungs that are incompletely developed and lacking adequate amount of surfactant and antioxidant defenses are susceptible to lung injury. The decades-long quest to prevent bronchopulmonary dysplasia has had limited success, in part because of increasing survival of more immature infants. The process must begin in the delivery room with gentle assistance in establishing and maintaining adequate lung aeration, followed by noninvasive support and less invasive surfactant administration. Various modalities of invasive and noninvasive support have been used with varying degree of effect and are reviewed in this article.

Sustained Inflation Versus Intermittent Positive Pressure Ventilation for Preterm Infants at Birth: Respiratory Function and Vital Sign Measurements

OBJECTIVE

To characterize respiratory function monitor (RFM) measurements of sustained inflations and intermittent positive pressure ventilation (IPPV) delivered noninvasively to infants in the Sustained Aeration of Infant Lungs (SAIL) trial and to compare vital sign measurements between treatment arms.

STUDY DESIGN

We analyzed RFM data from SAIL participants at 5 trial sites. We assessed tidal volumes, rates of airway obstruction, and mask leak among infants allocated to sustained inflations and IPPV, and we compared pulse rate and oxygen saturation measurements between treatment groups.

RESULTS

Among 70 SAIL participants (36 sustained inflations, 34 IPPV) with RFM measurements, 40 (57%) were spontaneously breathing prior to the randomized intervention. The median expiratory tidal volume of sustained inflations administered was 5.3 mL/kg (IQR 1.1-9.2). Significant mask leak occurred in 15% and airway obstruction occurred during 17% of sustained inflations. Among 34 control infants, the median expiratory tidal volume of IPPV inflations was 4.3 mL/kg (IQR 1.3-6.6). Mask leak was present in 3%, and airway obstruction was present in 17% of IPPV inflations. There were no significant differences in pulse rate or oxygen saturation measurements between groups at any point during resuscitation.

CONCLUSION

Expiratory tidal volumes of sustained inflations and IPPV inflations administered in the SAIL trial were highly variable in both treatment arms. Vital sign values were similar between groups throughout resuscitation. Sustained inflation as operationalized in the SAIL trial was not superior to IPPV to promote lung aeration after birth in this study subgroup.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT02139800.

Devices for Administering Ventilation at Birth: A Systematic Review

CONTEXT

Positive pressure ventilation (PPV) is the most important intervention during neonatal resuscitation.

OBJECTIVE

To compare T-piece resuscitators (TPRs), self-inflating bags (SIBs), and flow-inflating bags for newborns receiving PPV during delivery room resuscitation.

DATA SOURCES

Medline, Embase, Cumulative Index to Nursing and Allied Health Literature, Cochrane Database of Systematic Reviews, and trial registries (inception to December 2020).

STUDY SELECTION

Randomized, quasi-randomized, interrupted time series, controlled before-and-after, and cohort studies were included without language restrictions.

DATA EXTRACTION

Two researchers independently extracted data, assessed the risk of bias, and evaluated the certainty of evidence. The primary outcome was in-hospital mortality. When appropriate, data were pooled by using fixed-effect models.

RESULTS

Meta-analysis of 4 randomized controlled trials (1247 patients) revealed no significant difference between TPR and SIB for in-hospital mortality (risk ratio 0.74; 95% confidence interval [CI] 0.40 to 1.34). Resuscitation with a TPR resulted in a shorter duration of PPV (mean difference -19.8 seconds; 95% CI -27.7 to -12.0 seconds) and lower risk of bronchopulmonary dysplasia (risk ratio 0.64; 95% CI 0.43 to 0.95; number needed to treat 32). No differences in clinically relevant outcomes were found in 2 randomized controlled trials used to compare SIBs with and without positive end-expiratory pressure valves. No studies used to evaluate flow-inflating bags were found.

LIMITATIONS

Certainty of evidence was very low or low for most outcomes.

CONCLUSIONS

Resuscitation with a TPR compared with an SIB reduces the duration of PPV and risk of bronchopulmonary dysplasia. A strong recommendation cannot be made because of the low certainty of evidence. There is insufficient evidence to determine the effectiveness of positive end-expiratory pressure valves when used with SIBs.

European Resuscitation Council Guidelines 2021: Newborn resuscitation and support of transition of infants at birth

The European Resuscitation Council has produced these newborn life support guidelines, which are based on the International Liaison Committee on Resuscitation (ILCOR) 2020 Consensus on Science and Treatment Recommendations (CoSTR) for Neonatal Life Support. The guidelines cover the management of the term and preterm infant. The topics covered include an algorithm to aid a logical approach to resuscitation of the newborn, factors before delivery, training and education, thermal control, management of the umbilical cord after birth, initial assessment and categorisation of the newborn infant, airway and breathing and circulation support, communication with parents, considerations when withholding and discontinuing support.

[Newborn resuscitation and support of transition of infants at birth]

The European Resuscitation Council has produced these newborn life support guidelines, which are based on the International Liaison Committee on Resuscitation (ILCOR) 2020 Consensus on Science and Treatment Recommendations (CoSTR) for Neonatal Life Support. The guidelines cover the management of the term and preterm infant. The topics covered include an algorithm to aid a logical approach to resuscitation of the newborn, factors before delivery, training and education, thermal control, management of the umbilical cord after birth, initial assessment and categorisation of the newborn infant, airway and breathing and circulation support, communication with parents, considerations when withholding and discontinuing support.

Sustained inflation: The lung recruitment maneuvers for neonates

Establishing effective respiration is vital in the transition from fetal to neonatal life. Respiratory support mainly facilitates and creates functional residual capacity and maintains adequate gas exchange. Sustained inflation (SI) delivers prolonged inflation and rapidly creates and establishes the functional residual capacity. The use of SI in preterm infants in the delivery room is still controversial. The optimum settings of SI remain unknown. Animal studies and clinical reports have demonstrated the advantages and disadvantages of SI. In this article, the current literature was reviewed to examine the efficacy of SI in infants.

Validation of the disposable T-piece resuscitator (Neo-Tee): a bench study

OBJECTIVE

The Neo-Tee Infant T-piece resuscitator is a disposable T-piece resuscitator. The aim of this bench study was to assess the accuracy of the Neo-Tee using a measurement set-up and settings mimicking clinical practice.

STUDY DESIGN

Nine Neo-Tee devices were tested using a face mask interface and a manikin. Pressures were set using the built-in manometer and simultaneously measured at the interface. Peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) were studied under static conditions and positive pressure ventilation (PPV), using a wide range of clinically relevant flows and pressures. Pressures were measured without adjusting for a possible offset of PIP and PEEP after switching from static pressures to PPV. In an additional subset of measurements, PIP/PEEP offsets on the Neo-Tee manometer after starting PPV were adjusted.

RESULTS

Under static conditions, setting the PEEP level with the Neo-Tee manometer results in overestimation of the true PEEP applied at the airway opening, with a difference of approximately 1.5 cmH₂O. When switching to PPV, this difference almost disappears. In contrast to PEEP, PIP levels measured at the airway opening were accurate.Adjusting PIP and PEEP on the built-in manometer after starting PPV was necessary in all measurements, but this did not improve the accuracy of the targeted pressure delivery, especially for PEEP. A gas flow rate of 5 L/min was insufficient to reach commonly used PEEP levels of 5 cmH₂O.

CONCLUSION

The Neo-Tee T-piece resuscitator is accurate for delivering a static inflation and PPV, but not for delivering continuous positive airway pressure.

Delivery of positive end-expiratory pressure to preterm lambs using common resuscitation devices

BACKGROUND

In neonatal resuscitation, a ventilation device providing positive end-expiratory pressure (PEEP) is recommended. There is limited information about PEEP delivery in vivo, using different models of self-inflating bag (SIB) at different inflation rates and PEEP settings.

METHODS

We compared PEEP delivery to intubated preterm lambs using four commonly available models of paired SIBs and PEEP valves, with a T-piece, with gas flow of 8 L/min. Peak inspiratory pressure inflations of 30 cmH₂O, combined with set PEEP of 5, 7 and 10 cmH₂O, were delivered at rates of 20, 40 and 60/min. These combinations were repeated without gas flow. We measured mean PEEP, maximum and minimum PEEP, and its difference (PEEP reduction).

RESULTS

A total of 3288 inflations were analysed. The mean PEEP delivered by all SIBs was lower than set PEEP (P<0.001), although some differences were <0.5 cmH₂O. In 55% of combinations, the presence of gas flow resulted in increased PEEP delivery (range difference 0.3-2 cmH₂O). The mean PEEP was closer to set PEEP with faster inflation rates and higher set PEEPs. The mean (SD) PEEP reduction was 3.9 (1.6), 8.2 (1.8), 2 (0.6) and 1.1 (0.6) cmH₂O with the four SIBs, whereas it was 0.5 (0.2) cmH₂O with the T-piece.

CONCLUSIONS

PEEP delivery with SIBs depends on the set PEEP, inflation rate, device model and gas flow. At recommended inflation rates of 60/min, some devices can deliver PEEP close to the set level, although the reduction in PEEP makes some SIBs potentially less effective for lung recruitment than a T-piece.

Effective ventilation: The most critical intervention for successful delivery room resuscitation

Lung aeration is the critical first step that triggers the transition from fetal to postnatal cardiopulmonary physiology after birth. When an infant is apneic or does not breathe sufficiently, intervention is needed to support this transition. Effective ventilation is therefore the cornerstone of neonatal resuscitation. In this article, we review the physiology of cardiopulmonary transition at birth, with particular attention to factors the caregiver should consider when providing ventilation. We then summarize the available clinical evidence for strategies to monitor and perform positive pressure ventilation in the delivery room setting.

Positive end-expiratory pressure during resuscitation at birth in very-low birth weight infants: A randomized-controlled pilot trial

BACKGROUND

There is limited evidence of the effect of positive end-expiratory pressure (PEEP) during resuscitation soon after birth. Premature neonates may experience respiratory distress from surfactant insufficiency and providing PEEP after the very first breath, may improve outcomes following appropriate resuscitation. The objective of this study was to evaluate the short term respiratory outcomes after positive pressure ventilation (PPV) with PEEP in preterm infants at birth.

METHODS

A prospective randomized-controlled, pilot trial was conducted. Premature neonates ≤ 32 weeks gestational age or birth weight < 1500 g were recruited. Subjects were allocated to either PEEP of 5 cm H₂O (PEEP-5) or no PEEP (PEEP-0) if PPV was administered. Pre-ductal, peripheral capillary oxygen saturation (SpO₂) and fraction of inspired oxygen concentration (FiO₂) were monitored at 1, 3, 5, 10, 15, and 20 min after birth. FiO₂ was adjusted to achieve targeted SpO₂ using the 2010 neonatal resuscitation protocol guidelines.

RESULTS

56% (14/25; PEEP-0) and 50% (13/26; PEEP-5) infants received PPV. Mean gestational age was 30 (PEEP-0) vs 31 (PEEP-5) weeks. The mean [SD] birthweight (g) of PEEP-0 was significantly lower than PEEP-5 (1050.4 [262.7] vs 1218.8 [236.8], p = 0.02). Pre-ductal SpO_2, FiO₂ delivered at each time point, and rates of pneumothorax, surfactant administration and oxygen dependency at 36 weeks postmenstrual age or death was similar.

CONCLUSION

Due to the small sample size and potential bias accrued through random allocation of higher birthweight infants to the PEEP-5 group, the results did not confirm differences in outcomes between the groups, despite evidence favoring postnatal ventilation with PEEP. A further randomized, controlled clinical trial with a larger sample size is warranted to determine the utility and safety of PEEP during the resuscitation of premature infants immediately after birth.

Inflation pressures and times during initial resuscitation in preterm infants

BACKGROUND

The optimal combination of inflation pressures and times to produce adequate expiratory tidal volumes during initial resuscitation in prematurely born infants has not been determined. The aim of this study was therefore to assess combinations of inflation pressures and times and the resulting expiratory tidal volume levels using a respiratory function monitor.

METHODS

Sixty-four infants born before 34 weeks of gestation were studied. The infants were divided according to whether the inflation pressure (peak inflation pressure minus positive end expiratory pressure) was < or ≥20 cmH₂ O during the first five inflations delivered by a face mask, and those groups were then subdivided according to whether the inflation time was < or ≥1.5 s.

RESULTS

Inflation pressure ≥20 cmH₂ O compared with lower pressure at both inflation times produced significantly higher expiratory tidal volume. Longer compared with shorter inflation times when the inflation pressure was ≥20 cmH₂ O resulted in no significant difference in expiratory tidal volume. At <20 cmH₂ O inflation pressure, longer inflation time overall resulted in higher end tidal volume, but the majority of infants had a tidal volume less than the anatomical dead space.

CONCLUSIONS

At higher inflation pressure, a longer inflation time was not necessary to increase expiratory tidal volume.

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

BACKGROUND

Manual resuscitation devices for infants and newborns must be able to provide adequate ventilation in a safe and consistent manner across a wide range of patient sizes (0.5-10 kg) and differing clinical states. There are little comparative data assessing biomechanical performance of common infant manual resuscitation devices across the manufacturers' recommended operating weight ranges. We aimed to compare performance of the Ambu self-inflating bag (SIB) with the Neopuff T-piece resuscitator in three resuscitation models.

METHODS

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

RESULTS

3309 inflations were collected and analysed with analysis of variance for repeated measures. The Neopuff was unable to reach set peak inflation pressures and exhibited seriously elevated positive end expiratory pressure (PEEP) with all inflow gas rates (p<0.001) in this infant model. The Ambu SIB accurately delivered targeted pressures in all three models.

CONCLUSIONS

The Ambu SIB was able to accurately deliver targeted pressures across all three models from preterm to infant. The Neopuff infant resuscitator was unable to deliver the targeted pressures in the infant model developing clinically significant levels of inadvertent PEEP which may pose risk during infant resuscitation.

Neonatal ventilation with a manikin model and two novel PEEP valves without an external gas source

OBJECTIVE

Positive end expiratory pressure (PEEP) is beneficial when ventilating preterm newborns. The aim was to study whether inexperienced providers were able to generate PEEP during simulated neonatal ventilation, using two novel prototype PEEP valves, on a self-inflating bag without an external gas source.

DESIGN

Forty-six nursing students in Tanzania were trained in ventilation with a new Laerdal Upright resuscitator and mask on a NeoNatalie manikin with a newborn resuscitation monitor. Ventilation was studied with and without PEEP valve 1 (anticipated level 4-5 cm H₂O) and with and without PEEP valve 2 (anticipated level 9-10 cm H₂O) in random order for normal and low 'lung' compliance. The PEEP valves were concave silicone valves with a small slit that would open to let expiratory air out.

RESULTS

Mean PEEP with PEEP1 was 4.4 cm H₂O (SD 2.2) and with PEEP2 was 4.9 cm H₂O (SD 3.1). PEEP ≥4 cm H₂O was generated with 70% of inflations with PEEP1 and 65% with PEEP2. Mean airway pressure was 16.3 cm H₂O with both PEEP valves compared with 14.2 without PEEP (p<0.001). Mean mask leak was similar with and without PEEP (48% with PEEP1, 58% with PEEP2, 55% without PEEP). Mask leak and PEEP were inversely correlated. Findings with normal and low 'lung' compliance were similar.

CONCLUSIONS

PEEP between 4 cm H₂O and 5 cm H₂O was achieved when ventilating a neonatal manikin using a self-inflating bag and novel PEEP valves. Valves that can generate PEEP without external gas sources may aid resuscitation in resource-limited settings.

Golden 60 minutes of newborn's life: Part 2: Term neonate

The concept of "Golden 60 minutes" or "Golden Hour" has been derived from adult trauma. It has been defined as the first 60 min of postnatal life. It has been seen that care received by any newborn in the initial first hour has implications in the future life, showing the importance of golden hour. The major cause of neonatal mortality term newborn is asphyxia, which can be reduced with effective resuscitation. In golden hour approach for term newborn, the importance is given to effective and evidence based resuscitation, post-resuscitation care, delayed cord clamping, prevention of hypothermia, immediate breast feeding, prevention of hypoglycemia, and starting of therapeutic hypothermia in case of moderate to severe asphyxia. In this part of review, we will cover all the golden hour interventions in term neonate with current evidence.

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

BACKGROUND

The self-inflating bag (SIB) is the most common device used to resuscitate newborn infants worldwide. Delivering positive end-expiratory pressure (PEEP) may be important in infant resuscitation and limited research using one brand (Laerdal) SIB has led to international guidelines stating SIBs 'often deliver inconsistent positive end-expiratory pressure'.

AIM

To measure delivered PEEP using disposable and reusable Ambu SIBs fitted with Ambu PEEP valve and manometer comparing different rates of 20, 40 and 60 inflations per minute (IPM) and test lung compliance.

DESIGN

Three experienced neonatal medical staff provided positive pressure ventilation each using different disposable and reusable Ambu SIBs, targeting peak inflation pressure of 30-35 cm H2O at three different set PEEP levels of 5, 7.5 and 10 cm H2O on test lungs of compliance of 0.5 and 3.0 mL/cm H2O. Inflation data were captured with Florian Monitor and analysed by analysis of variance for repeated measures.

RESULTS

A total of 3265 inflations were analysed. The delivered PEEP was rate and lung compliance dependent. At set PEEP of 5 cm H2O, the adjusted measured PEEP was 3.6, 4.4 and 4.8 cm H2O at rates 20, 40 and 60 IPM, respectively, while at set PEEP of 10 cm H2O, the adjusted measured PEEP was 7.0, 8.8 and 9.8 cm H2O. The delivered PEEP was statistically higher with more compliant test lungs.

CONCLUSIONS

The Ambu SIB with Ambu PEEP valve can deliver consistent mean levels of PEEP close to the operator set PEEP. The performance of SIB with PEEP valves is likely brand specific and requires further evaluation.

Quality improvement project: implementing guidelines supporting noninvasive respiratory management for premature infants

PURPOSE

Based on research evidence, the purpose was to implement noninvasive approaches in the initial respiratory stabilization of preterm infants.

DESIGN

Quality improvement project.

SAMPLE

One hundred fourteen infants admitted to the neonatal intensive care nursery (NICN) from January 1, 2012 to May 31, 2012 served as a historical control group. Ninety-four infants admitted from January 1, 2013 to May 31, 2013 served as the intervention group.

RESULTS

After implementation of the quality improvement initiative, there was a statistically significant increase in the rate of using continuous positive airway pressure (CPAP ) by 65.3 percent for initial respiratory stabilization of preterm infants.

Neonatal endotracheal intubation: How to make it more baby friendly

Neonatal endotracheal intubation is commonly accompanied by significant disturbances in physiological parameters. The procedure is often poorly tolerated, and multiple attempts are commonly required before the airway is secured. Adverse physiological effects include hypoxemia, bradycardia, hypertension, elevation in intracranial pressure and possibly increase in pulmonary vascular resistance. Use of premedications to facilitate intubation has been shown to reduce but not eliminate these effects. Other important preventative factors include adequate training of the operators and guidelines to limit the duration of attempts. Pre-intubation stabilisation with optimal bag and mask ventilation should allow for better neonatal tolerance of the procedure. Recent research has described significant mask leak and airway obstruction compromising efficacy of neonatal mask ventilation. Further research should help in elucidating mask ventilation techniques which minimise mask leak and airway obstruction.

Sustained lung inflation at birth: what do we know, and what do we need to know?

A sustained inflation has been advocated as a potential method of augmenting lung aeration at birth. Clinical trials have suggested that a sustained inflation may lead to a reduced need for intubation and ventilation in the first few days of life, without cardiovascular compromise or increased lung injury. Despite this, a sustained inflation is not currently a standard of practice, mainly due to a lack of clarity regarding the optimal delivery method. Animal trials have sought to refine delivery techniques. This review will outline current recommendations regarding a sustained inflation, discuss potential strategies for its optimal delivery and suggest priorities for future research.

Manual Ventilation and Sustained Lung Inflation in an Experimental Model: Influence of Equipment Type and Operator's Training

Aim

To compare the influence of devices for manual ventilation and individual experience on the applied respiratory mechanics and sustained lung inflation.

Methods

A total of 114 instructors and non-instructors from the Neonatal Resuscitation Program of the Brazilian Society of Pediatrics participated in this study. Participants ventilated an intubated manikin. To evaluate respiratory mechanics and sustained lung inflation parameters, a direct comparison was made between the self-inflating bag and the T-shaped resuscitator (T-piece), followed by an analysis of the effectiveness of the equipment according to the participants’ education and training.

Results

A difference between equipment types was observed for the tidal volume, with a median (interquartile range) of 28.5 mL (12.6) for the self-inflating bag and 20.1 mL (8.4) for the T-piece in the instructor group and 31.6 mL (14) for the self-inflating bag and 22.3 mL (8.8) for the T-piece in the non-instructor group. Higher inspiratory time values were observed with the T-piece in both groups of professionals, with no significant difference between them. The operator’s ability to maintain the target pressure over the 10 seconds of sustained lung inflation was evaluated using the area under the pressure-time curve and was 1.7-fold higher with the use of the T-piece. Inspiratory pressure and mean airway pressure applied during sustained lung inflation were greater with the self-inflating bag, as evaluated between the beginning and the end of the procedure.

Conclusion

The T-piece resulted in lower tidal volume and higher inspiratory time values, irrespective of the operator’s experience, and increased the ease of performing the sustained lung inflation maneuver, as demonstrated by the maintenance of target pressure for the desired period and a higher mean airway pressure than that obtained using the self-inflating bag.

Ventilation strategies for preventing oxidative stress-induced injury in preterm infants with respiratory disease: an update

Reactive oxygen and nitrogen species are produced by several inflammatory and structural cells of the airways. The lungs of preterm newborns are susceptible to oxidative injury induced by both reactive oxygen and nitrogen species. Increased oxidative stress and imbalance in antioxidant enzymes may play a role in the pathogenesis of inflammatory pulmonary diseases. Preterm infants are frequently exposed to high oxygen concentrations, infections or inflammation; they have reduced antioxidant defense and high free iron levels which enhance toxic radical generation. Multiple ventilation strategies have been studied to reduce injury and improve outcomes in preterm infants. Using lung protective strategies, there is the need to reach a compromise between satisfaction of gas exchange and potential toxicities related to over-distension, derecruitment of lung units and high oxygen concentrations. In this review, the authors summarize scientific evidence concerning oxidative stress as it relates to resuscitation in the delivery room and to the strategies of ventilation.

Comparison of efficacy of three devices of manual positive pressure ventilation: a mannequin-based study

BACKGROUND

We compared the efficacy of and consistency in manual ventilation by trained healthcare professionals using three devices: self-inflating bag, flow-inflating bag, and T-piece resuscitator.

METHODS

Prospective analytical study at a level III Neonatal unit of a tertiary care hospital. Forty participants (consultants, postgraduates, interns, and neonatal nurses - 10 each) manually ventilated a mannequin with the above three devices for three minutes each. This procedure was video recorded. The pressure delivered during the three minutes and the breath rates for the first minute, second minute, and third minute were analyzed. Descriptive statistics were used to describe the study population and group statistics were used for various parameters of interest. Factorial analysis of variance was conducted to determine the main effects of device and specialty of users.

RESULTS

The mean (SD) peak inspiratory pressure of T-piece resuscitator was 16.5 (1.2), self-inflating bag (SIB) was 20.7 (4.4), and flow-inflating bag (AB) was 21.2 (5.0). The mean (SD) positive end expiratory pressure of T-piece resuscitator was 4.7 (0.9) cm of H2O and AB was 1.8 (1.7) cm of H2O. The maximum pressure delivered by T-piece resuscitator was 17.5, AB was 26.2, and SIB was 25.2 cm of H2O. Clinically appropriate breath rates were delivered using all of the devices. More effective breath rates were delivered using T-piece. There was no significant difference among the professional groups.

CONCLUSIONS

The T-piece resuscitator provides the most consistent pressures and is most effective. Level of training has no influence on pressures delivered during manual ventilation.

Bio-inspired flow sensor from printed PEDOT:PSS micro-hairs

This paper reports on the creation of a low-cost, disposable sensor for low flow velocities, constructed from extruded micro-sized 'hair' of conducting polymer PEDOT. These microstructures are inspired by hair strands found in many arthropods and chordates, which play a prime role in sensing air flows. The paper describes the fabrication techniques and the initial prototype testing results toward employing this sensing mechanism in applications requiring sensing of low flow rates such as a flow sensor in neonatal resuscitators. The fabricated 1000 μm long, 6 μm diameter micro-hairs mimic the bending movement of tactile hair strands to sense the velocity of air flow. The prototype sensor developed is a four-level direct digital-output sensor and is capable of detecting flow velocities of up to 0.97 m s(-1).

Fifty years in neonatology

Neonatology, the care and study of newborn infants, is a 'young' specialty. Over the last 50 years, there have been many advances in the way that neonatologists care for newborn infants, particularly those born preterm, leading to dramatic improvements in mortality. To illustrate these advances, we describe four eras in neonatology from the point of view of the junior hospital doctor.

Accuracy of a disposable compared to a non-disposable infant T-piece resuscitator

Both disposable and non-disposable T-piece resuscitator (TPR) devices are used. Accuracy of the disposable and non-disposable infant TPR was compared. Peak inspiratory pressures (PIP) and positive end-expiratory pressures (PEEP) were measured during ventilation of a test lung. Measured PIP ±1 cmH2O and PEEP ±0.5 cmH2O of the desired pressures were considered acceptable. We tested the following: (A) Accuracy of setting pressures using built-in manometers of three disposable TPRs, (B) Minimal and maximal PIP and PEEP levels for the non-disposable and disposable TPR were measured using different gas flow rates, and (C) Accuracy of 25 caregivers setting pressures (PIP 25 cmH2O and PEEP 5 cmH2O). The results of the tests performed were as follows: (A) With pressures set: PIP 20, 25, 30, and 40 cmH2O and PEEP 5-8 cmH2O with 1 cmH2O stepwise increment, measured PIPs and PEEPs were in acceptable range. (B) At gas flow rates 5, 8, 10, and 15 L/min (disposable vs. non-disposable), min-max PIP were 4.0-43.2 vs. 2.9-77.1 cmH2O and min-max PEEP were 0.3-22.3 and 0.6-59.7 cmH2O. (C) Set PIP (cmH2O) by participants using disposable vs. non-disposable TPR was 25.8 (0.8) vs. 25.9 (1.3) (ns). PEEP was 5.4(0.5) vs. 4.7(0.5); p < 0.001.

CONCLUSION

The accuracy of the disposable TPR is comparable to that of the non-disposable TPR.

Changes in positive end-expiratory pressure alter the distribution of ventilation within the lung immediately after birth in newborn rabbits

Current recommendations suggest the use of positive end-expiratory pressures (PEEP) to assist very preterm infants to develop a functional residual capacity (FRC) and establish gas exchange at birth. However, maintaining a consistent PEEP is difficult and so the lungs are exposed to changing distending pressures after birth, which can affect respiratory function. Our aim was to determine how changing PEEP levels alters the distribution of ventilation within the lung. Preterm rabbit pups (28 days gestation) were delivered and mechanically ventilated with one of three strategies, whereby PEEP was changed in sequence; 0-5-10-5-0 cmH₂O, 5-10-0-5-0 cmH₂O or 10-5-0-10-0 cmH₂O. Phase contrast X-ray imaging was used to analyse the distribution of ventilation in the upper left (UL), upper right (UR), lower left (LL) and lower right (LR) quadrants of the lung. Initiating ventilation with 10PEEP resulted in a uniform increase in FRC throughout the lung whereas initiating ventilation with 5PEEP or 0PEEP preferentially aerated the UR than both lower quadrants (p<0.05). Consequently, the relative distribution of incoming V_T was preferentially directed into the lower lobes at low PEEP, primarily due to the loss of FRC in those lobes. Following ventilation at 10PEEP, the distribution of air at end-inflation was uniform across all quadrants and remained so regardless of the PEEP level. Uniform distribution of ventilation can be achieved by initiating ventilation with a high PEEP. After the lungs have aerated, small and stepped reductions in PEEP result in more uniform changes in ventilation.

Repeated thermo-sterilisation further affects the reliability of positive end-expiratory pressure valves

AIM

Positive end-expiratory pressure (PEEP) valves are used together with self-inflating bags (SIB) to provide a preset PEEP during manual ventilation. It has recently been shown that these valves deliver highly variable levels of PEEP. We hypothesised that material fatigue due to repeated thermo-sterilisation (TS) may contribute to varying reliability of PEEP valves.

METHODS

In a laboratory study 10 new PEEP valves were tested before and after 10, 20 and 30 cycles of routine TS (7 min at 134°C) by using a neonatal lung model (compliance 0.2 mL/kPa). Settings were positive inflation pressure = 20 and 40 cm H(2)O, PEEP = 5 and 10 cm H(2)O, respiratory rate = 40 and 60/min, flow = 8l/min. PEEP was recorded using a respiratory function monitor.

RESULTS

Before TS, a mean (standard deviation) PEEP of 4.0 (0.9) and 7.7 (1.0) cm H(2)O was delivered by the 10 valves when the PEEP was set to 5 and 10 cm H(2)O, respectively. One new valve only delivered 2.0 (0.0) and 5.0 (0.0) cm H(2)O when the PEEP was adjusted to 5 and 10 cm H(2)O, respectively. Four of the 10 investigated valves showed significant variations in PEEP (coefficient of variation >10%) throughout the autoclaving process. One valve completely lost its function after the 20th TS. Common defects were tears in the softer materials or displacement of the rubber seal. Six of the 10 valves continued to provide PEEP in spite of repeated TS.

CONCLUSION

The reliability of PEEP valves is affected by repeated TS. Multi-use PEEP valves should be tested for reliable PEEP provision following TS.

Do we deliver the pressures we intend to when using a T-piece resuscitator?

Background

A T-piece resuscitator (TPR) uses a built-in manometer to set the inflation pressures, but we are not informed what pressures are actually delivered distally. Aim of this study was to measure the proximal and distal pressures under different gas conditions when using a TPR.

Methodology/Findings

A test lung was ventilated using a TPR (PIP 25 cmH₂O, PEEP 5 cmH₂O) with a gas flow rate of 8 L/min. A) Pressure delivered by six different TPRs was tested. To test variability 20 participants were asked to set PEEP and PIP pressures to 25/5 cmH₂O. B) PIP and PEEP were measured proximal and distal of the TPR when using standard tubing or heated tubing with or without a humidifier. In experiment A mean (SD) proximal PIP and PEEP of the TPRs were respectively 20.3 (0.3) cmH₂O (19.9–20.6 cmH₂O) and 4.9 (0.1) cmH₂O. When 20 participants set pressures; PIP 26.7 (0.5) cm H₂O and PEEP 5.9 (0.44) cmH₂O were measured. Experiment B showed that the decrease of PIP between proximal and distal pressures was not clinically significant. However there was a significant decrease of PEEP using the standard tubing (5.1 (0.1) cmH₂O proximally versus 4.8 (0.2) cmH₂O distally; p<0.001) compared to, when using a humidifier with associated tubing and the humidifier turned on, 5.1 (0.1) proximally versus 3.9 (0.2) cmH₂O distally; (p<0.001).

Conclusion/Significance

The accuracy of the built-in manometer of a TPR is acceptable. Most pressures set proximally are comparable to the actual pressures delivered distally. However, when using tubing associated with the humidifier PEEP decreases distally by 1.1–1.2 cmH₂O and users should anticipate on this.

Short- and intermediate-term outcomes of preterm infants receiving positive pressure ventilation in the delivery room

Although recent advances in neonatal care have improved survival rates, rates of bronchopulmonary dysplasia remain unchanged. Although neonatologists are increasingly applying gentle ventilation strategies in the neonatal intensive care unit, the same emphasis has not been applied immediately after birth. A lung-protective strategy should start with the first breath to help in the establishment of functional residual capacity, facilitate gas exchange, and reduce volutrauma and atelectotrauma. This paper will discuss techniques and equipment during breathing assistance in the delivery room.

Resuscitation of preterm infants: delivery room interventions and their effect on outcomes

Despite advances in neonatal care, the rate of oxygen dependence at 36 weeks' postmenstrual age or bronchopulmonary dysplasia has not fallen. Neonatologists are increasingly careful to apply ventilation strategies that are gentle to the lung in the neonatal intensive care unit. However, there has not been the same emphasis applying gentle ventilation strategies immediately after birth. A lung-protective strategy should start immediately after birth to establish a functional residual capacity, reduce volutrauma and atelectotrauma, facilitate gas exchange, and improve oxygenation during neonatal transition. This article discusses techniques and equipment recommended by international resuscitation guidelines during breathing assistance in the delivery room.

Fatores que afetam a ventilação com o reanimador manual autoinflável: uma revisão sistemática

OBJETIVO: O reanimador manual autoinflável é um dispositivo que fornece ventilação com pressão positiva. Pesquisas mostram que, apesar da padronização dos reanimadores manuais autoinfláveis pela American Society for Testing and Materials, diversos fatores afetam o desempenho da ventilação, porém, os resultados são conflitantes. O objetivo desse estudo foi verificar as evidências dos fatores que influenciam a ventilação pulmonar com reanimadores manuais infantil/adulto por meio de uma revisão sistemática da literatura. FONTES DE DADOS: Foram incluídos artigos indexados nas bases Medline, Lilacs e SciELO publicados entre janeiro de 1986 e março de 2011. Utilizaram-se as palavras-chaves: "reanimador manual", "ressuscitador manual", "ventilação manual", "ventilação com pressão positiva", em inglês e português, além de "bag-valve". SÍNTESE DOS DADOS: Foram selecionados 45 artigos, sendo a maioria experimental. Os trabalhos compararam os reanimadores manuais por marcas, modelos e analisaram as características dos profissionais que os utilizam. Estudos verificaram que a eficácia da ventilação com os reanimadores manuais depende da marca, modelo e características funcionais do aparelho utilizado, assim como formação, treinamento e experiência do profissional que os manipula. Outros fatores que podem influenciar são a forma de compressão dos reanimadores manuais, o uso da válvula limitadora de pressão e o fluxo de oxigênio fornecido aos aparelhos. CONCLUSÕES: A variabilidade nos parâmetros ventilatórios fornecidos durante a ventilação com reanimadores manuais não permite uniformizar a técnica, o que prejudica a reanimação cardiopulmonar. Apesar da maioria dos reanimadores manuais parecer estar de acordo com padrões internacionais, os equipamentos devem ser avaliados antes de utilizados no ambiente clínico. Pouco se sabe sobre os modelos pediátricos e neonatais.