Respiratory support in meconium aspiration syndrome: a practical guide

Use of surfactant beyond respiratory distress syndrome, what is the evidence?

Surfactant replacement therapy is currently approved by the United States Food and Drug Administration (FDA) for premature infants with respiratory distress syndrome (RDS) caused by surfactant deficiency due to immaturity. There is strong evidence that surfactant decreases mortality and air leak syndromes in premature infants with RDS. However, surfactant is also used "off-label" for respiratory failure beyond classic RDS. This review discusses current evidence for the use of off-label surfactant therapy for (1) term infants with lung disease such as meconium aspiration syndrome (MAS), pneumonia/sepsis, and congenital diaphragmatic hernia (2) premature infants after 72 h for acute respiratory failure, and (3) the use of surfactant lavage. At last, we briefly describe the use of surfactants for drug delivery and the current evidence on evaluating infants for surfactant deficiency.

Meconium aspiration syndrome: from pathophysiology to treatment

Meconium aspiration syndrome (MAS) is a clinical condition characterized by respiratory distress in neonates born through meconium-stained amniotic fluid (MSAF). Despite advances in obstetric practices and perinatal care, MAS remains an important cause of morbidity and mortality in term and post-term newborns. Since the 1960s, there have been significant changes in the perinatal and postnatal management of infants born through MSAF. Routine endotracheal suctioning is no longer recommended in both vigorous and non-vigorous neonates with MSAF. Supportive care along with new treatments such as surfactant, inhaled nitric oxide, and high-frequency ventilation has significantly improved the outcome of MAS patients. However, determining the most appropriate approach for this condition continues to be a topic of debate. This review offers an updated overview of the epidemiology, etiopathogenesis, diagnosis, management, and prognosis of infants with MAS.

Meconium aspiration syndrome: a comprehensive review

Meconium aspiration syndrome (MAS) is a complex respiratory disease that continues to be associated with significant morbidities and mortality. The pathophysiological mechanisms of MAS include airway obstruction, local and systemic inflammation, surfactant inactivation and persistent pulmonary hypertension of the newborn (PPHN). Supplemental oxygen and non-invasive respiratory support are the main therapies for many patients. The management of the patients requiring invasive mechanical ventilation could be challenging because of the combination of atelectasis and air trapping. While studies have explored various ventilatory modalities, evidence to date does not clearly support any singular modality as superior. Patient's pathophysiology, symptom severity, and clinician/unit expertise should guide the respiratory management. Early identification and concomitant management of PPHN is critically important as it contributes significantly to mortality and morbidities.

Effect of Endotracheal Suctioning on Infants Born through Meconium-Stained Amniotic Fluid: A Meta-analysis

OBJECTIVE

Meconium is a common finding in amniotic fluid and placental specimens, particularly in term and post-term pregnancies. The objective of this paper was to perform a meta-analysis to examine the impact of endotracheal suctioning on the occurrence of meconium aspiration syndrome (MAS), mortality, and complications.

STUDY DESIGN

PubMed, EMBASE, and the Cochrane library were systematically searched for comparative studies. Odds ratios (ORs), weighted mean differences (WMDs), and corresponding 95% confidence intervals (CIs) were used to compare the outcomes.

RESULTS

Twelve studies were included in the meta-analysis. There were no significant impacts of endotracheal suctioning on the occurrence of MAS (OR = 3.05, 95% CI: 0.48-19.56), mortality (OR = 1.25, 95% CI: 0.35-4.44), the need for mechanical ventilation (OR = 4.20, 95% CI: 0.32-54.72), the occurrence of pneumothorax (OR = 0.99, 95% CI: 0.34-2.85), persistent pulmonary hypertension of the newborn (PPHN), (OR = 1.31, 95% CI: 0.58-2.98), hypoxic-ischemic encephalopathy (HIE) (OR = 0.82, 95% CI: 0.52-1.30), and length of stay (WMD = -0.11, 95% CI: -0.99-0.77).

CONCLUSION

Routine endotracheal suctioning at birth is not useful in preventing MAS, mortality, mechanical ventilation, PPHN, HIE, and prolonged length of stay in neonates born through MSAF.

KEY POINTS

· Routine suctioning is not recommended for newborns.. · Endotracheal aspiration is not beneficial for MAS.. · Future research may focus on selected neonates..

Determinants of meconium aspiration syndrome among neonates admitted to neonatal intensive care unit at Nigist Eleni Mohammed Memorial Comprehensive Specialized Hospital, South Ethiopia: Unmatched case-control study

Objective:

To identify determinants of meconium aspiration syndrome among neonates admitted to the neonatal intensive care unit at Nigist Eleni Mohammed Memorial Comprehensive Specialized Hospital, South Ethiopia, in 2022.

Method:

A facility-based unmatched case–control study was used to identify meconium aspiration syndrome with a total sample size of 249 from January to April 2022. Data were entered by using EpiData version 3.1 and analyzed using SPSS version 24 software. Descriptive findings were presented by frequency tables and percentages. Multicollinearity was checked and the goodness of fit test was done. To determine the independent determinants associated with meconium aspiration syndrome, bivariate analysis was done and variables with a p value of <0.05 were taken to multivariate logistic regression analysis. Adjusted odds ratio with a 95% confidence interval was calculated, and statistical significance was declared at a p value less than 0.05.

Result:

Two hundred forty-nine (83 cases and 166 controls) mothers with their respective neonates were included in this study and that made the overall response rate 100%. Preeclampsia (adjusted odds ratio: 3.35, 95% confidence interval: 1.02, 10.97), antepartum hemorrhage (adjusted odds ratio: 3.63, 95% confidence interval: 1.50, 8.78), duration of labor (adjusted odds ratio: 4.34, 95% confidence interval: 1.83, 10.30), premature rupture of membrane (adjusted odds ratio: 16.02, 95% confidence interval: 5.66, 45.29), and obstructed labor (adjusted odds ratio: 4.57, 95% confidence interval: 1.42, 14.70) were determinants of meconium aspiration syndrome.

Conclusion:

In this study, preeclampsia, antepartum hemorrhage, duration of labor, premature rupture of membrane, and obstructed labor were determinants of meconium aspiration syndrome. Therefore, to reduce the risk of meconium aspiration syndrome, prevention, early identification, and management of these obstetrical factors may help to reduce meconium aspiration syndrome locally.

Safety use of high frequency oscillatory ventilation in transport of newborn infants affected by severe respiratory failure: preliminary data in central Tuscany

Background

Neonatal Emergency Transport Services play a fundamental role in neonatal care. Stabilization before transport of newborns suffering from severe respiratory failure is often a challenging problem and some critically ill infants may benefit from High Frequency Oscillatory Ventilation (HFOV) as rescue treatment. In these cases, transition to conventional ventilation for transport may cause a deterioration in clinical conditions. HFOV during neonatal transport has been only exceptionally used, due to technical difficulties. Since May 2018, a new neonatal transport unit is available at the Neonatal Protected Transport Service of the Meyer University Hospital in Florence, equipped with a pulmonary ventilator capable of delivering HFOV. Therefore, we conducted an analysis on patients transferred in HFOV to Neonatal Intensive Care Unit (NICU), in order to evaluate the safety and feasibility of its use during neonatal transport.

Methods

A retrospective analysis was performed reviewing medical records of the neonates transported by Meyer Children Hospital’s Neonatal Transport Service between May 2018 and December 2020, and newborns treated with HFOV during ground neonatal transport were identified. Safety was assessed by the comparison of vital signs, hemogas-analysis values and pulmonary ventilator parameters, at the time of departure and upon arrival in NICU. The dose of inotropes, the main respiratory complications (air leak, dislocation or obstruction of the endotracheal tube, loss of chest vibrations) and the number of deaths and transfer failures were recorded.

Results

Out of the approximate 400 newborns transported during the analysis period, 9 were transported in HFOV. We did not find any statistically significant difference in vital parameters, hemogas-analytical values and pulmonary ventilator settings recorded before and after neonatal transport of the nine patients’ parameters (p > 0,05). No patient required additional inotropes during transport. No transport-related deaths or significant complications occurred during transport.

Conclusions

The interest of our report is in the possibility of using HFOV during inter-hospital neonatal transfer. As far as our experience has shown, HFOV appears to be safe for the transportation of newborns with severe respiratory failure. Nevertheless, further larger, prospective and multicentre studies are needed to better evaluate the safety and efficacy of HFOV during neonatal transport.

Prise en charge périnatale du nouveau-né lors d’une naissance en milieu extrahospitalier

Les accouchements inopinés extrahospitaliers représentent environ 0,3 % des accouchements en France. La prise en charge du nouveau-né en préhospitalier par une équipe Smur fait partie de l’activité courante. L’évaluation initiale du nouveau-né comprend systématiquement la mesure de sa fréquence cardiaque (FC) et respiratoire (FR), l’appréciation de son tonus ainsi que la mesure de sa température axillaire. En cas de doute ou de transition incomplète un monitoring cardiorespiratoire sera immédiatement mis en place (FC, FR, SpO2). Nous faisons ici une mise au point sur les données connues et avons adapté les pratiques, si besoin, au contexte extrahospitalier, car la majeure partie des données rapportées dans la littérature concernent les prises en charge en maternité ou en milieu hospitalier. Nous abordons les points essentiels de la prise en charge des nouveau-nés, à savoir la réanimation cardiopulmonaire, le clampage tardif du cordon ombilical, la lutte contre l’hypothermie et l’hypoglycémie; ainsi que des situations particulières comme la prématurité, la conduite à tenir en cas de liquide méconial ou de certaines malformations congénitales. Nous proposons aussi quels peuvent être : le matériel nécessaire à la prise en charge des nouveau-nés en extrahospitalier, les critères d’engagement d’un renfort pédiatrique à la régulation ainsi que les méthodes de ventilation et d’abord vasculaire que l’urgentiste doit maîtriser. L’objectif de cette mise au point est de proposer des prises en charge les plus adaptées au contexte préhospitalier.

Is meconium exposure associated with autism spectrum disorders in children?

BACKGROUND

The results differ among published studies regarding exposure to meconium and the risk of developing autism spectrum disorders (ASDs).

PURPOSE

The present study pooled all of the epidemiologic studies retrieved from broader databases on the association between meconium exposure and risk of developing ASD in children.

METHODS

The Web of Science, PubMed, Scopus, and Google Scholar databases were searched without language restrictions for articles published between their inception to February 20, 2020, using relevant keywords. The pooled odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated as random-effect estimates of the associations among studies. A subgroup analysis was conducted to explore any potential sources of heterogeneity among studies.

RESULTS

The pooled estimate of OR reported a weakly significant association between meconium exposure and ASD development in children (OR, 1.13; 95% CI, 1.03-1.24). There was low heterogeneity among the articles reporting risk for ASD among children (I2=19.3%; P=0.259). The results of subgroup analysis based on meconium exposure showed a significant association between a meconium-stained neonate and ASD development (OR, 1.18; 95% CI, 1.11-1.24).

CONCLUSION

Meconium exposure was weakly associated with an increased risk of ASD. However, more evidence based on large prospective cohort studies is required to provide conclusive evidence about whether meconium exposure is associated with an increased risk of ASD development.

The "Hub and Spoke" (HandS) ECMO for "Resuscitating" Neonates with Respiratory Life-Threatening Conditions

Background: Extracorporeal membrane oxygenation (ECMO) implantation for neonates with severe cardiorespiratory life-threatening conditions is highly effective. However, since ECMO is a high-risk and complex therapy, this treatment is usually performed in centers with proven expertise. Methods: A retrospective review of neonates, from January 2014 to January 2020, presenting with life-threatening conditions and treated by means of Hub and Spoke (HandS) ECMO in peripheral (spoke) hospitals. Data were retrieved from our internal ECMO registry. Protocols and checklists were revised and shared with all spoke hospitals located in North-Eastern Italy. Results: Eleven neonates receiving maximal respiratory and cardiovascular support at a spoke hospital underwent HandS ECMO management. All but three patients were affected by life-threatening meconium aspiration syndrome (MAS). The median ECMO support duration and hospitalization were four (range 2–32) and 30 days (range 8–50), respectively. All but two patients (with congenital diaphragmatic hernia), were weaned off ECMO and discharged home. At a mean follow up of 33.7 ± 29.2 months, all survivors were alive and well, without medications, and normal somatic growth. All but one had normal neuropsychological development. Conclusion: HandS ECMO model for neonates with life-threatening conditions is effective and successful. A specialized multidisciplinary team and close cooperation between Hub and Spoke centers are essential for success.

Meconium aspiration pneumonia and otitis media in two goat kids

We report meconium aspiration in 2 sibling goat kids, and characterize the expected lesions of aspiration pneumonia in conjunction with the rare lesion of otitis media. Grossly, the lungs were multifocally consolidated, and there was yellow-green exudate within the middle ear. Histologically, the lung was characterized by pyogranulomatous pneumonia and foreign-body reaction around aspirated debris. Within the lumen of the middle ear, aspirated squamous cells, keratin, meconium debris, and neutrophils, without evidence of bacteria, were accompanied by a subepithelial accumulation of lymphocytes, plasma cells, and fewer macrophages. This is an especially rare phenomenon, which is thought to result from transport of meconium from the oropharynx through the auditory tube (Eustachian tube) to the middle ear.

Recombinant Human Superoxide Dismutase and N-Acetylcysteine Addition to Exogenous Surfactant in the Treatment of Meconium Aspiration Syndrome

This study aimed to evaluate the molecular background of N-acetylcysteine (NAC) and recombinant human superoxide dismutase (rhSOD) antioxidant action when combined with exogenous surfactant in the treatment of meconium aspiration syndrome (MAS), considering redox signalling a principal part of cell response to meconium. Young New Zealand rabbits were instilled with meconium suspension (Mec) and treated by surfactant alone (Surf) or surfactant in combination with i.v. NAC (Surf + NAC) or i.t. rhSOD (Surf + SOD), and oxygen-ventilated for 5 h. Dynamic lung-thorax compliance, mean airway pressure, PaO₂/FiO₂ and ventilation efficiency index were evaluated every hour; post mortem, inflammatory and oxidative markers (advanced oxidation protein products, total antioxidant capacity, hydroxynonenal (HNE), p38 mitogen activated protein kinase, caspase 3, thromboxane, endothelin-1 and secretory phospholipase A₂) were assessed in pulmonary tissue homogenates. rhSOD addition to surfactant improved significantly, but transiently, gas exchange and reduced levels of inflammatory and oxidative molecules with higher impact; Surf + NAC had stronger effect only on HNE formation, and duration of treatment efficacy in respiratory parameters. In both antioxidants, it seems that targeting reactive oxygen species may be strong supporting factor in surfactant treatment of MAS due to redox sensitivity of many intracellular pathways triggered by meconium.

HandS ECMO: Preliminary Experience With "Hub and Spoke" Model in Neonates With Meconium Aspiration Syndrome

We aim to evaluate clinical outcomes of emergent extracorporeal membrane oxygenation (ECMO) implantation in newborns with life-threatening meconium aspiration syndrome (MAS) in peripheral hospitals with Hub and Spoke (HandS) setting. We retrospectively reviewed all neonates presenting with MAS, with no other comorbidities, treated with HandS ECMO, in peripheral hospitals. Team activation time (TAT) was described as the time from first alerting call to ECMO support initiation. From May 2014 to December 2016, 4 patients met our inclusion criteria. In addition, 2 cases occurred on the same day, requiring a second simultaneous HandS ECMO team activation. All patients were younger than 8 days of life (1, 1, 4, and 7), with a mean BSA 0.21 ± 0.03m² , and TAT of 203, 265, 320, and 340 min. One patient presented ventricular fibrillation after priming administration. Veno-arterial ECMO was established in all patients after uneventful surgical neck vessels cannulation (right carotid artery and jugular vein). Mean time from skin incision to ECMO initiation was 19 ± 1.4 min. Mean length of ECMO support was 2.75 ± 1.3 days. All patients were weaned off support without complications. At a mean follow up of 20.5 ± 7.8 months, all patients are alive, with no medications, normal somatic growth, and neuropsychological development. MAS is a life-threatening condition that can be successfully managed with ECMO support. A highly trained multidisciplinary HandS ECMO team is crucial for the successful management of these severely ill newborns in peripheral hospitals.

Selective inhibition of NF-kappaB and surfactant therapy in experimental meconium-induced lung injury

Meconium aspiration syndrome (MAS) in newborns is characterized mainly by respiratory failure due to surfactant dysfunction and inflammation. Previous meta-analyses did not prove any effect of exogenous surfactant treatment nor glucocorticoid administration on final outcome of children with MAS despite oxygenation improvement. As we supposed there is the need to intervene in both these fields simultaneously, we evaluated therapeutic effect of combination of exogenous surfactant and selective inhibitor of NF-kappaB (IKK-NBD peptide). Young New Zealand rabbits were instilled by meconium suspension and treated by surfactant alone or surfactant in combination with IKK-NBD, and oxygen-ventilated for 5 h. PaO(2)/FiO(2), oxygenation index, oxygen saturation and ventilation efficiency index were evaluated every hour; post mortem, total and differential leukocyte counts were investigated in bronchoalveolar lavage fluid (BALF) and inflammatory, oxidative and apoptotic markers were assessed in lung tissue homogenates. Exogenous surfactant combined with IKK-NBD improved oxygenation, reduced neutrophil count in BALF and levels of IL-1beta, IL-6, p38 MAPK and caspase 3 in comparison with surfactant-only therapy. It seems that inhibition of inflammation may be strong supporting factor in surfactant treatment of MAS.

Effect of Nasal Continuous Positive Airway Pressure on Infants With Meconium Aspiration Syndrome: A Randomized Clinical Trial

IMPORTANCE

Nasal continuous positive airway pressure (NCPAP) as a primary respiratory therapy in meconium aspiration syndrome (MAS) has not been studied extensively. Nasal continuous positive airway pressure, when applied in newborns with MAS, may resolve atelectasis by sufficiently expanding partially obstructed small airways and stabilizing the collapsing terminal airways to enhance oxygen exchange.

OBJECTIVE

To compare NCPAP vs standard care in neonates with moderate to severe respiratory failure due to MAS in reducing the need for invasive ventilation.

DESIGN, SETTINGS, AND PARTICIPANTS

This multicenter open-label, parallel-group (1:1 ratio) randomized clinical trial was conducted from August 5, 2014, to May 26, 2016. Data were collected from 3 tertiary care neonatal intensive care units. All infants admitted with respiratory distress, defined as Downe score greater than 4 and peripheral capillary oxygen saturation less than 90%, were assessed for study eligibility if the chest radiograph was suggestive of MAS and they met the other inclusion criteria: gestation longer than 35 weeks, a birth weight greater than 2000 g, and born through meconium-stained amniotic fluid.

INTERVENTIONS

Infants were randomly assigned to either NCPAP or standard care (5-10 L/min hood oxygen).

MAIN OUTCOMES AND MEASURES

The primary outcome was the need for mechanical ventilation in the first 7 days of life.

RESULTS

After excluding 14 infants, 67 infants were randomized to bubble NCPAP and 68 infants to standard care. Baseline characteristics were similar between the 2 groups. Infants randomized to the bubble NCPAP group needed mechanical ventilation less frequently in the first 7 days of life compared with standard care (2 [3.0%] vs 17 [25.0%]); odds ratio, 0.09; 95% CI, 0.02-0.43; P = .002). The need for surfactant (3 [4.5%] vs 11 [16.2%]; odds ratio, 0.24; 95% CI, 0.05-0.87) and culture-positive sepsis (4 [6.0%] vs 13 [19.0%]; odds ratio, 0.28; 95% CI, 0.09-0.93) were higher in the standard care group. There was an increased duration of oxygen therapy (median [interquartile range], 45.5 [28.0-78.3] vs 26 [20.0-48.0] hours; P = .001) in the standard care group. In the NCPAP group vs standard care group, incidence of persistent pulmonary hypertension (9 [13%] vs 19 [28%]; odds ratio, 0.42; 95% CI, 0.17-1.01) and duration of hospital stay (median [interquartile range], 5.0 [4.0-8.8] vs 4.0 [4.0-6.0] days; P = .14) were similar.

CONCLUSIONS AND RELEVANCE

Bubble NCPAP in comparison with standard care for infants with MAS reduces the need for mechanical ventilation in the first 7 days of life.

TRIAL REGISTRATION

Clinical Trial Registry, India Identifier: CTRI/2015/03/005631.

Meconium "aspiration" (or respiratory distress associated with meconium-stained amniotic fluid?)

The designation meconium aspiration syndrome (MAS) reflects a spectrum of disorders in infants born with meconium-stained amniotic fluid, ranging from mild tachypnea to severe respiratory distress and significant mortality. The frequency of MAS is highest among infants with post-term gestation, thick meconium, and birth asphyxia. Pulmonary hypertension is an important component in severe cases. Prenatal hypopharyngeal suctioning and postnatal endotracheal intubation and suctioning of vigorous infants are not effective. Intubation and suctioning of non-breathing infants is controversial and needs more investigation. Oxygen, mechanical ventilation, and inhaled nitric oxide are the mainstays of treatment. Surfactant is often used in infants with severe parenchymal involvement. High-frequency ventilation and extracorporeal membrane oxygenation are usually considered rescue therapies.

Effects of Conventional Mechanical Ventilation Performed by Two Neonatal Ventilators on the Lung Functions of Rabbits with Meconium-Induced Acute Lung Injury

Severe meconium aspiration syndrome (MAS) in the neonates often requires a ventilatory support. As a method of choice, a conventional mechanical ventilation with small tidal volumes (VT<6 ml/kg) and appropriate ventilatory pressures is used. The purpose of this study was to assess the short-term effects of the small-volume CMV performed by two neonatal ventilators: Aura V (Chirana Stara Tura a.s., Slovakia) and SLE5000 (SLE Ltd., UK) on the lung functions of rabbits with experimentally-induced MAS and to estimate whether the newly developed neonatal version of the ventilator Aura V is suitable for ventilation of the animals with MAS.

In the young rabbits, a model of MAS was induced by an intratracheal instillation of a suspension of neonatal meconium (4 ml/kg, 25 mg/ml). After creating the model of MAS, the animals were ventilated with small-volume CMV (frequency 50/min, VT <6 ml/kg, inspiration time 50 %, fraction of inspired oxygen 1.0, positive end-expiratory pressure 0.5 kPa, mean airway pressure 1.1 kPa) performed by ventilator Aura V (Aura group, n=7) or ventilator SLE5000 (SLE group, n=7) for additional 4 hours. One group of animals served as healthy non-ventilated controls (n=6). Blood gases, oxygenation indexes, ventilatory pressures, lung compliance, oxygen saturation and total and differential white blood cell (WBC) count were regularly determined. After euthanizing the animals, a left lung was saline-lavaged and total and differential counts of cells in the bronchoalveolar lavage (BAL) fluid were determined. A right lung was used for estimation of lung edema formation (expressed as a wet/dry weight ratio) and for analysis of concentrations of pro-inflammatory cytokines (IL-1β, IL-8, TNF). The cytokines were measured also in the blood plasma taken at the end of experiment.

Meconium instillation seriously worsened the gas exchange and induced inflammation and lung edema formation. In the Aura group, slightly lower concentrations of cytokines were found and better gas exchange early after creating the MAS model was observed. However, there were no significant differences in the respiratory parameters between the ventilated groups at the end of experiment (P>0.05).

Concluding, the newly developed neonatal version of the ventilator Aura V was found to be fully comparable to widely used neonatal ventilator SLE5000. Results provided by Aura V in CMV ventilation of rabbits with meconium-induced acute lung injury suggest its great potential also for future clinical use, i.e. for ventilation of the neonates with MAS.

Inflammatory indices in meconium aspiration syndrome

INTRODUCTION

Meconium aspiration syndrome (MAS) is linked to inflammation, but data on the patterns of hematological indices and C-reactive protein (CRP) in MAS are lacking. The aim of the study was to evaluate CRP, white blood cell count (WBC), absolute neutrophil count (ANC), and immature-to-total neutrophil ratio (IT-ratio) in MAS and to assess their association with disease severity.

METHODS

Retrospective cross-sectional study including 239 consecutively admitted neonates with MAS to a level III NICU. Neonates with early onset sepsis were excluded. Results Neonates with severe MAS (invasive mechanical ventilation for <7 days) and very severe MAS (invasive mechanical ventilation for ≥7 days or high frequency ventilation or ECMO) had higher CRP and IT-ratio compared to neonates with non-severe MAS (no invasive mechanical ventilation) during the first 2 days of life (CRP: 13.0 and 40.9 vs. 9.5 mg/L, P = 0.039 and <0.001, respectively) and neonates with very severe MAS had lower WBC and ANC. All four inflammatory indices correlated significantly with duration of invasive mechanical ventilation, duration of respiratory support and with length of hospital stay, arterial hypotension, and persistent pulmonary hypertension. Neonates with all four inflammatory indices beyond the normal range had a more than 20-fold increase in risk for very severe MAS.

CONCLUSION

High CRP and IT-ratio and low WBC and ANC values were closely linked to a more severe course of MAS during the early phases of the disease. These findings reflect the role of inflammation in the pathogenesis of MAS. Pediatr Pulmonol. 2016;51:601-606. 2015 Wiley Periodicals, Inc.

High-Frequency Jet Ventilation against Small-Volume Conventional Mechanical Ventilation in the Rabbit Models of Neonatal Acute Lung Injury

Patients with acute lung injury are ventilated by conventional mechanical ventilation (CMV) rather than high-frequency jet ventilation (HFJV). This study estimated the potential usefulness of HFJV in acute lung injury. The issue was addressed by comparing the effects on lung function of CMV and HFJV in two rabbit models of neonatal acute lung injury: repetitive saline lung lavage (LAV) and meconium aspiration syndrome (MAS) induced by intratracheal meconium instillation. The animals were then ventilated with either HFJV or CMV for 4 h. Ventilatory pressures, blood gases, and indexes of gas exchange were assessed. Lung edema formation was expressed as wet-dry lung weight ratio. Both LAV and MAS significantly decreased lung compliance, increased airway resistance, and caused severe hypoxemia, hypercarbia, and acidosis. Although CMV was superior to HFJV at 1 h of ventilation, there were no clinically relevant differences in lung function or edema formation between CMV and LAV in both models of respiratory insufficiency at 4 h of ventilation. We conclude that, HFJV may be used for ventilation in acute non-homogenous lung injury.

Efficiency of high-frequency oscillatory ventilation combined with pulmonary surfactant in the treatment of neonatal meconium aspiration syndrome

The aim of this study was to investigate the clinical efficiency of the use high-frequency oscillatory ventilation (HFOV) combined with pulmonary surfactant (PS) for the treatment of neonatal meconium aspiration syndrome (MAS). Clinical data of 53 MAS patients admitted to neonatal intensive care unit (NICU) was collected and the patients were divided into 3 groups according to the different treatment approach: group 1 conventional mechanical ventilation (CMV); group 2 HFOV; group 3 HFOV + PS. By monitoring the changes in oxygenation function indicators such as inhaled oxygen concentration (FiO2), oxygenation index (OI) and arterial oxygen tension/alveolar arterial oxygen tension (a/ApO2) of three groups after 2, 12, 24, 48 h of treatment, the usage of the ventilator, duration of hospitalization, changes in clinical manifestations and outcomes of three groups were analyzed. As compared to group 1, the difference in all the oxygenation function indicators after treatment in group 2 and group 3 was statistically significant at different points in time (P < 0.05). However, the timing and extent of the change in the indicators in group 3 were more significant than in group 2; as compared to group 1, the ventilation time, duration of the oxygen therapy and hospitalization time of group 2 and group 3 were significantly shorter and the difference was statistically significant (P < 0.05). Early use of HFOV combined with PS to treat MAS has significant therapeutic effect, especially for the treatment of severe MAS where it can be used as a safer and more effective rescue measure.

High-frequency oscillatory ventilation with low oscillatory frequency in pulmonary interstitial emphysema

BACKGROUND

Pulmonary interstitial emphysema (PIE) is a common respiratory illness in preterm infants associated with significant morbidity and mortality for which the ventilatory management is imperfect.

OBJECTIVES

To evaluate the impact of high-frequency oscillatory ventilation (HFOV) with a low oscillatory frequency and thus prolonged expiratory time in preterm infants with severe PIE.

METHODS

In a retrospective cohort study, preterm infants ≤30 weeks' gestation with radiological findings of severe PIE, and either high FiO2 or persistent respiratory acidosis were studied if managed on HFOV with a low frequency (5-6 Hz, inspiratory time 30%) for >24 h. Trends in physiological and ventilatory parameters were examined over the first 72 h, radiological changes noted, and in-hospital outcomes ascertained.

RESULTS

19 cases were identified and analysed in two groups: 14 with bilateral and 5 with predominantly unilateral disease. After transition to low-frequency HFOV, physiological responses were seen in both groups, in particular a rapid and sustained improvement in oxygenation in the bilateral group (mean (SD) alveolar-arterial oxygen difference at baseline: 404 ± 206 mm Hg; 4 h post-transition: 262 ± 181 mm Hg; 72 h: 155 ± 74 mm Hg; p = 0.0003). This occurred following a reduction in mean airway pressure (mean (SD) baseline: 14 ± 3.9 cm H2O; 72 h: 12 ± 2.9 cm H2O; p = 0.011). In the unilateral group, radiological resolution of PIE was observed on re-inflation following collapse of the affected lung. Overall, 15 infants survived, including 10 of the bilateral cases (71%), and all of the unilateral cases.

CONCLUSION

HFOV with a low oscillatory frequency may afford benefit in preterm babies with severe PIE.