Mechanism of reduced lung injury by high-frequency nasal ventilation in a preterm lamb model of neonatal chronic lung disease

Evaluating tidal volume stability in extremely preterm infants on high-frequency oscillatory ventilation with volume guarantee

BACKGROUND

High Frequency Oscillatory Ventilation (HFOV) combined with volume guarantee (HFOV-VG) represents an innovative ventilation mode designed for managing respiratory failure in neonates. This study aimed to assess the stability of High Frequency tidal volume (VThf) in extremely preterm infants ventilated on HFOV with VG during the first 48 h of life. Additional objectives included examining the correlations between VThf, Diffusion Coefficient of Carbon Dioxide (DCO2) and key respiratory markers.

METHODS

This retrospective, single-center study included 22 extremely preterm infants treated with HFOV-VG as the primary mode of ventilation at King Abdulaziz Medical City. Data were collected directly from the ventilator every minute for the first 48 h of life. Blood gases were analyzed every 4-6 h to maintain normocapnia (PCO2 40-55 mmHg). The distribution of continuous variables was assessed using the Shapiro-Wilk test for normality. As most data were found to be non-normally distributed, results are presented as medians with interquartile ranges (IQR). The Kruskal-Wallis test was used to compare non-normally distributed continuous variables across groups. The Spearman's rank correlation coefficient (Spearman's rho) was used to evaluate correlations between key clinical and ventilatory variables. All statistical analyses were conducted using Stata software (version 17; StataCorp LLC, College Station, TX), with statistical significance set at p < 0.05.

RESULTS

Twenty-two infants had a median gestational age of 26.5 weeks (IQR 24-28) and a median birth weight of 830 g (IQR 600-1300). The median set VThf per kilogram was 2.2 mL/kg [IQR 2,2.6], which was consistent with the measured VThf. Significant correlations were observed between weight-corrected DCO2 and VThf (spearman rho = 0.8089, p < 0.0001), and between measured amplitude and weight corrected DCO2 (spearman rho = 0.6497p < 0.0001). Raw DCO2 correlated with measured amplitude (spearman rho = 0.1364, p < 0.0001). PCO2 showed no significant correlation with raw DCO2 (p = 0.4813) and weight-corrected DCO2 (p = 0.4845). Notable variations in FiO2, frequency, and MAP were identified between different PCO2 levels (p < 0.01) as well as the weight corrected DCO2 (p = 0.04).

CONCLUSIONS

HFOV-VG effectively stabilized VThf in extremely preterm infants with fluctuations in amplitude, providing consistent ventilation support during the early critical period. The weight-corrected DCO2 correlated strongly with VThf and measured amplitude, underscoring its potential as a reliable marker for CO2 clearance. These findings highlight the utility of HFOV-VG in managing respiratory needs in extreme preterm infant.

Nasal High-Frequency Oscillatory Ventilation Use in Romanian Neonatal Intensive Care Units-The Results of a Recent Survey

BACKGROUND

Nasal high-frequency oscillatory ventilation (nHFOV) has emerged as an effective initial and rescue noninvasive respiratory support mode for preterm infants with respiratory distress syndrome (RDS); however, little is known about nHFOV use in Romanian neonatal intensive care units (NICUs).

OBJECTIVES

We aimed to identify the usage extent and clinical application of nHFOV in Romania.

METHODS

A structured web-based questionnaire was designed to find the rate of nHFOV use and knowledge of this new method of noninvasive respiratory support in Romanian level III NICUs. Using multiple-choice, open-ended, and yes/no questions, we collected information on the NICU's size, noninvasive respiratory support modes used, nHFOV use, indications, settings, nasal interfaces, secondary effects, and equipment used. Descriptive statistics and comparisons were performed using IBM SPSS Statistics 26.0.

RESULTS

A total of 21/23 (91.3%) leaders from level III NICUs (median [IQR] number of beds of 10 [10-17.5]) responded to the survey. The most frequently used noninvasive ventilation modes were CPAP mode on mechanical ventilators (76.2%), followed by NIPPV (76.2%); heated, humidified high-flow nasal cannula (HHHFNC) (61.9%); and nHFOV (11/21 units; 52.4%). A total of 5/11 units reported frequent nHFOV use (in two or more newborns/month) in both term and preterm infants. The main indications reported for nHFOV use were CPAP failure (90.9%), hypercapnia (81.8%), and bronchopulmonary dysplasia (72.7%). Face/nasal masks and short binasal prongs are the most commonly used nasal interfaces (90.9% and 72.7%, respectively). Air leaks at the interface level (90.9%), thick secretions (81.8%), and airway obstruction (63.6%) were the most frequently mentioned adverse effects of nHFOV. Only three of the NICUs had a written protocol for nHFOV use. Most units not yet using nHFOV cited lack of equipment, experience, training, or insufficient information and evidence for the clinical use and outcome of nHFOV use in neonates as the main reasons for not implementing this noninvasive respiratory mode.

CONCLUSIONS

Our survey showed that nHFOV is already used in more than half of the Romanian level III NICUs to support term and preterm infants with respiratory distress despite a lack of consensus regarding indications and settings during nHFOV.

Mesenchymal stromal cell extracellular vesicles improve lung development in mechanically ventilated preterm lambs

Novel therapies are needed for bronchopulmonary dysplasia (BPD) because no effective treatment exists. Mesenchymal stromal cell extracellular vesicles (MSC-sEVs) have therapeutic efficacy in a mouse pup neonatal hyperoxia BPD model. We tested the hypothesis that MSC-sEVs will improve lung functional and structural development in mechanically ventilated preterm lambs. Preterm lambs (∼129 days; equivalent to human lung development at ∼28 wk gestation) were exposed to antenatal steroids, surfactant, caffeine, and supported by mechanical ventilation for 6-7 days. Lambs were randomized to blinded treatment with either MSC-sEVs (human bone marrow MSC-derived; 2 × 1011 particles iv; n = 8; 4 F/4 M) or vehicle control (saline iv; 4 F/4 M) at 6 and 78 h post delivery. Physiological targets were pulse oximetry O2 saturation 90-94% ([Formula: see text] 60-90 mmHg), [Formula: see text] 45-60 mmHg (pH 7.25-7.35), and tidal volume 5-7 mL/kg. MSC-sEVs-treated preterm lambs tolerated enteral feedings compared with vehicle control preterm lambs. Differences in weight patterns were statistically significant. Respiratory severity score, oxygenation index, A-a gradient, distal airspace wall thickness, and smooth muscle thickness around terminal bronchioles and pulmonary arterioles were significantly lower for the MSC-sEVs group. S/F ratio, radial alveolar count, secondary septal volume density, alveolar capillary surface density, and protein abundance of VEGF-R2 were significantly higher for the MSC-sEVs group. MSC-sEVs improved respiratory system physiology and alveolar formation in mechanically ventilated preterm lambs. MSC-sEVs may be an effective and safe therapy for appropriate functional and structural development of the lung in preterm infants who require mechanical ventilation and are at risk of developing BPD.NEW & NOTEWORTHY This study focused on potential treatment of preterm infants at risk of developing bronchopulmonary dysplasia (BPD), for which no effective treatment exists. We tested treatment of mechanically ventilated preterm lambs with human mesenchymal stromal cell extracellular vesicles (MSC-sEVs). The results show improved respiratory gas exchange and parenchymal growth of capillaries and epithelium that are necessary for alveolar formation. Our study provides new mechanistic insight into potential efficacy of MSC-sEVs for preterm infants at risk of developing BPD.

Pulmonary phenotypes of bronchopulmonary dysplasia in the preterm infant

Bronchopulmonary dysplasia (BPD) remains the most common complication of premature birth, imposing a significant and potentially life-long burden on patients and their families. Despite advances in our understanding of the mechanisms that contribute to patterns of lung injury and dysfunctional repair, current therapeutic strategies remain non-specific with limited success. Contemporary definitions of BPD continue to rely on clinician prescribed respiratory support requirements at specific time points. While these criteria may be helpful in broadly identifying infants at higher risk of adverse outcomes, they do not offer any precise information regarding the degree to which each compartment of the lung is affected. In this review we will outline the different pulmonary phenotypes of BPD and discuss important features in the pathogenesis, clinical presentation, and management of these frequently overlapping scenarios.

The effect of non-invasive high-frequency oscillatory ventilation on the duration of non-invasive respiratory support in late preterm and term infants with transient tachypnea of the newborn: a randomized controlled trial

Nasal continuous positive airway pressure (nCPAP) is one of the most commonly used non-invasive respiratory support modes in neonates with transient tachypnea of the newborn (TTN). Non-invasive high-frequency oscillatory ventilation (nHFOV) is a non-invasive respiratory support mode that has been increasingly used in neonatal respiratory disorders. This prospective randomized controlled study compared the efficacy of nHFOV and nCPAP in reducing the duration of non-invasive respiratory support. Late preterm and term infants > 34 weeks' gestation were included in the study. The infants were randomly assigned to receive either nHFOV or nCPAP. Treatment was started with standard settings in both groups. Infants who met treatment failure criteria were switched to nasal intermittent mandatory ventilation for further positive-pressure support. A total of 60 infants were included in the study. Thirty of these infants were included in the nHFOV group and 30 were included in the nCPAP group. The median duration of non-invasive respiratory support was not significantly different between the two groups (21 h [IQR: 16-68] for nHFOV vs 15 h [IQR: 11-33] for nCPAP; p = 0.09). However, after adjusting for potential confounders, nHFOV was associated with a shorter duration of non-invasive respiratory support than nCPAP (adjusted mean difference: 16.3 h; 95% CI: 0.7 to 31.9; p = 0.04). nHFOV was well tolerated and did not increase the risk of complications.    Conclusion: Our findings suggest that nHFOV is an effective and safe ventilation mode for late preterm and term neonates with TTN.   Trial registry: Clinicaltrials.gov (NCT03006354). Date of registration: December 30, 2016. What is Known: • nHFOV is a ventilation model that has been increasingly used for the management of RDS. • TTN is one of the most common causes of neonatal respiratory distress. What is New: • nHFOV is associated with shorter duration of non-invasive respiratory support and duration of oxygen support. • nHFOV may be a safe and effective alternative to nCPAP for neonates with TTN.

Rescue high-frequency oscillatory ventilation combined with intermittent mandatory ventilation for infants with acute respiratory distress syndrome after congenital heart surgery

BACKGROUND

This study aimed to evaluate the efficacy and safety of high-frequency oscillation ventilation combined with intermittent mandatory ventilation in infants with acute respiratory distress syndrome after congenital heart surgery.

METHODS

We retrospectively analysed the clinical data of 32 infants who were ventilated due to acute respiratory distress syndrome after congenital heart surgery between January, 2020 and January, 2022. We adopted high-frequency oscillation ventilation combined with intermittent mandatory ventilation as the rescue ventilation mode for infants who were failing conventional mechanical ventilation.

RESULTS

After rescue high-frequency oscillation ventilation combined with intermittent mandatory ventilation, the dynamic compliance (Cdyn), PaO2 and PaO2/FiO2 ratio of the infants improved compared with conventional mechanical ventilation (p < 0.05). Moreover, high-frequency oscillation ventilation combined with intermittent mandatory ventilation resulted in a significant decrease in arterial-alveolar oxygen difference (AaDO2), FiO2, and oxygenation index (p < 0.05). No significant effect on haemodynamic parameters was observed. Moreover, no serious complications occurred in the two groups.

CONCLUSION

Rescue high-frequency oscillation ventilation combined with intermittent mandatory ventilation significantly improved oxygenation in infants who failed conventional mechanical ventilation for acute respiratory distress syndrome after congenital heart surgery. Thus, this strategy is considered safe and feasible. However, further studies must be conducted to confirm the efficacy and safety of high-frequency oscillation ventilation combined with intermittent mandatory ventilation as a rescue perioperative respiratory support strategy for CHD.

Association between postnatal environmental tobacco smoke exposure controlling for prenatal exposure and conduct problems in children: A systematic review

Prenatal exposure to environmental tobacco smoke (ETS) is commonly associated with conduct problems in children. However, there is limited research on the effects of postnatal ETS exposure on the development of conduct problems, and many studies focusing on the postnatal period fail to control for the effects of prenatal ETS. This systematic review explores the association between postnatal ETS exposure and child conduct problems in studies that control for prenatal ETS exposure. Of the thirteen studies identified, nine reported a significant positive association of postnatal ETS exposure and child conduct-related behavior problems when controlling for prenatal ETS exposure. Results from tests of dose-response relationships were mixed. These findings highlight the significance of postnatal ETS exposure in conferring risk for conduct problems over and above prenatal ETS, and thus provide important information for guiding public health recommendations.

Heat shock protein 70 protects the lungs from hyperoxic injury in a neonatal rat model of bronchopulmonary dysplasia

Hyperoxia plays a significant role in the pathogenesis of lung injury, such as bronchopulmonary dysplasia (BPD), in premature infants or newborns. BPD management aims to minimize further injury, provide an optimal environment to support growth and recovery. In clinic neonatal care, we need a new therapy for BPD. Heat shock protein 70 (Hsp70) inhibit cell apoptosis and promote cell repair allowing cells to survive lethal injury. We hypothesized that Hsp70 could be used to prevent hyperoxia related BPD in the neonatal rat model through its anti-apoptotic and anti-inflammatory effects. In this study, we explored the effect of Hsp70 on hyperoxia-induced lung injury using neonatal rats. Neonatal Wistar rats were delivered naturally at full term of gestation and were then pooled and randomly assigned to several groups to receive heat stimulation (41°C for 20 min) or room temperature conditions. The Hsp70 group received recombinant Hsp70 intraperitoneally (200 μg/kg, daily). All newborn rats were placed under hyperoxic conditions (85% oxygen) for 21 days. Survival rates in both heat-hyperoxia and Hsp70-hyperoxia groups were higher than those in the hyperoxia group (p < 0.05). Both endogenous and exogenous Hsp70 could reduce early apoptosis of alveolar cells under hyperoxia. Additionally, there were less macrophage infiltration in the lung of the Hsp70 groups (p < 0.05). Heat stress, heat shock proteins, and exogenous recombinant Hsp70 significantly increased the survival rate and reduced pathological hyperoxia induced lung injuries in the development of BPD. These results suggest that treating hyperoxia-induced lung injury with Hsp70 may reduce the risk of developing BPD.

Pilot dose-ranging of rhIGF-1/rhIGFBP-3 in a preterm lamb model of evolving bronchopulmonary dysplasia

BACKGROUND

Low levels of insulin-like growth factor-1 (IGF-1) protein in preterm human infants are associated with bronchopulmonary dysplasia (BPD). We used our preterm lamb model of BPD to determine (1) dosage of recombinant human (rh) IGF-1 bound to binding protein-3 (IGFBP-3) to reach infant physiologic plasma levels; and (2) whether repletion of plasma IGF-1 improves pulmonary and cardiovascular outcomes.

METHODS

Group 1: normal, unventilated lambs from 128 days gestation through postnatal age 5 months defined normal plasma levels of IGF-1. Group 2: continuous infusion of rhIGF-1/rhIGFBP-3 (0.5, 1.5, or 4.5 mg/kg/day; n = 2) for 3 days in mechanically ventilated (MV) preterm lambs determined that 1.5 mg/kg/day dosage attained physiologic plasma IGF-1 concentration of ~125 ng/mL, which was infused in four more MV preterm lambs.

RESULTS

Group 1: plasma IGF-1 protein increased from ~75 ng/mL at 128 days gestation to ~220 ng/L at 5 months. Group 2: pilot study of the optimal dosage (1.5 mg/kg/day rhIGF-1/rhIGFBP-3) in six MV preterm lambs significantly improved some pulmonary and cardiovascular outcomes (p < 0.1) compared to six MV preterm controls. RhIGF-1/rhIGFBP-3 was not toxic to the liver, kidneys, or lungs.

CONCLUSIONS

Three days of continuous iv infusion of rhIGF-1/rhIGFBP-3 at 1.5 mg/kg/day improved some pulmonary and cardiovascular outcomes without toxicity.

IMPACT

Preterm birth is associated with rapid decreases in serum or plasma IGF-1 protein level. This decline adversely impacts the growth and development of the lung and cardiovascular system. For this pilot study, continuous infusion of optimal dosage of rhIGF-1/rhIGFBP-3 (1.5 mg/kg/day) to maintain physiologic plasma IGF-1 level of ~125 ng/mL during mechanical ventilation for 3 days statistically improved some structural and biochemical outcomes related to the alveolar formation that would favor improved gas exchange compared to vehicle-control. We conclude that 3 days of continuous iv infusion of rhIGF-1/rhIGFBP-3 improved some physiological, morphological, and biochemical outcomes, without toxicity, in mechanically ventilated preterm lambs.

Moving bronchopulmonary dysplasia research from the bedside to the bench

Although advances in the respiratory management of extremely preterm infants have led to improvements in survival, this progress has not yet extended to a reduction in the incidence of bronchopulmonary dysplasia (BPD). BPD is a complex multifactorial condition that primarily occurs due to disturbances in the regulation of normal pulmonary airspace and vascular development. Preterm birth and exposure to invasive mechanical ventilation also compromises large airway development, leading to significant morbidity and mortality. Although both predisposing and protective genetic and environmental factors have been frequently described in the clinical literature, these findings have had limited impact on the development of effective therapeutic strategies. This gap is likely because the molecular pathways that underlie these observations are yet not fully understood, limiting the ability of researchers to identify novel treatments that can preserve normal lung development and/or enhance cellular repair mechanisms. In this review article, we will outline various well-established clinical observations while identifying key knowledge gaps that need to be filled with carefully designed preclinical experiments. We will address these issues by discussing controversial topics in the pathophysiology, the pathology, and the treatment of BPD, including an evaluation of existing animal models that have been used to answer important questions.

Respiratory and Gastrointestinal Management of an Infant with a Birth Weight of 258 Grams

Today, more infants weighing less than or equal to 300 g are born, and they survive because of the improvements in neonatal care and treatment. However, their detailed clinical course and neonatal intensive care unit management remain unknown due to their low survival rate and dearth of reports. A male infant was born at 24 weeks and 5 days of gestation and weighed 258 g. The infant received 72 days of invasive and 92 days of noninvasive respiratory support, including high-frequency oscillatory ventilation with volume guarantee and noninvasive neurally adjusted ventilatory assist. Meconium-related ileus was safely treated using diatrizoate. Although the infant was diagnosed with severe bronchopulmonary dysplasia and retinopathy of prematurity requiring laser photocoagulation, he had no other severe complications. He was discharged 201 days postdelivery (3 months of corrected age) with a weight of 3.396 kg. Although managing infants weighing less than or equal to 300 g is difficult, our experience shows that it is possible by combining traditional and modern management methods. The management of such infants requires an understanding of the expected difficulties and adaptation of existing methods to their management. The management techniques described here should help improve their survival and long-term prognosis.

Nasal High-Frequency Ventilation

Noninvasive high-frequency oscillatory (NHFOV) and percussive (NHFPV) ventilation represent 2 nonconventional techniques that may be useful in selected neonatal patients. We offer here a comprehensive review of physiology, mechanics, and biology for both techniques. As NHFOV is the technique with the wider experience, we also provided a meta-analysis of available clinical trials, suggested ventilatory parameters boundaries, and proposed a physiology-based clinical protocol to use NHFOV.

Application of high-frequency oscillation ventilation combined with volume guarantee in infants with acute hypoxic respiratory failure after congenital heart surgery

OBJECTIVE

This study aimed to evaluate the efficacy and safety of high-frequency oscillation ventilation combined with volume guarantee (HFOV-VG) compared with the safety and efficacy of HFOV alone in infants with acute hypoxemic respiratory failure (AHRF) after congenital heart surgery.

METHODS

We retrospectively analyzed the clinical data of 44 infants who were ventilated for AHRF after congenital heart surgery between January 2020 and January 2021. HFOV alone was used in 23 of the 44 infants, whereas HFOV-VG was used in the other 21 infants.

RESULTS

The average frequency tidal volume (VThf) of the HFOV-VG group was lower than that of the HFOV group, and the proportion of VThf exceeding the target range of infants in the HFOV-VG group was also lower (p < .01). In addition, the incidence of hypocapnia and hypercapnia in infants supported with HFOV-VG was significantly lower (p < .01). Furthermore, the duration of invasive ventilation and the median ventilator adjustment per hour in the HFOV-VG group was also lower than that in the HFOV group (p < .01).

CONCLUSIONS

Compared with HFOV alone, HFOV-VG decreases the fluctuation of VThf and the incidence of hypercapnia and hypocapnia. Moreover, it reduces the workload of bedside medical staff. Further studies are needed to confirm the efficacy and safety of HFOV-VG as a routine respiratory support strategy for congenital heart disease during the perioperative period.

Nasal high-frequency jet ventilation (NHFJV) as a novel means of respiratory support in extremely low birth weight infants

OBJECTIVE

Describe our experience of successfully using nasal high-frequency jet ventilation (NHFJV) in extremely low birth weight infants with respiratory failure.

STUDY DESIGN

A retrospective review was conducted on 16 infants with birth weights <1000 g who received NHFJV from 2015 to 2019. Successful use was defined as avoiding intubation for at least 72 hours and demonstrating tolerance after being placed on NHFJV.

RESULTS

Median gestational age was 24.5 weeks (IQR 24, 25), and weight at the start of NHFJV 1090 g (IQR 905, 1250). NHFJV was used successfully in 13/16 (81%) infants with a median duration of 7 days (IQR 3, 12). Days on invasive (30 vs. 186) and noninvasive (46 vs. 81) ventilation were shorter when compared to those who failed the use of NHFJV.

CONCLUSION

This is the first reported case series for the successful use of NHFJV. Our study highlights the feasibility of a potential new mode of noninvasive respiratory support.

Non-invasive Respiratory Support of the Premature Neonate: From Physics to Bench to Practice

Premature births continue to rise globally with a corresponding increase in various morbidities among this population. Rates of respiratory distress syndrome and the consequent development of Bronchopulmonary Dysplasia (BPD) are highest among the extremely preterm infants. The majority of extremely low birth weight premature neonates need some form of respiratory support during their early days of life. Invasive modes of respiratory assistance have been popular amongst care providers for many years. However, the practice of prolonged invasive mechanical ventilation is associated with an increased likelihood of developing BPD along with other comorbidities. Due to the improved understanding of the pathophysiology of BPD, and technological advances, non-invasive respiratory support is gaining popularity; whether as an initial mode of support, or for post-extubation of extremely preterm infants with respiratory insufficiency. Due to availability of a wide range of modalities, wide variations in practice exist among care providers. This review article aims to address the physical and biological basis for providing non-invasive respiratory support, the current clinical evidence, and the most recent developments in this field of Neonatology.

Nasal High-Frequency Oscillatory Ventilation in Preterm Infants With Respiratory Distress Syndrome and ARDS After Extubation: A Randomized Controlled Trial

BACKGROUND

Nasal high-frequency oscillatory ventilation (NHFOV) has been described as supplying the combined advantages of nasal CPAP (NCPAP) and HFOV. However, its effect on preterm infants needs to be further elucidated. Our objective was to assess whether NHFOV could reduce intubation and Pco₂ levels as compared with NCPAP during the postextubation phase in preterm infants.

METHODS

This was a single-center, randomized, controlled trial, and it was registered at clinicaltrials.gov (NCT03140891) and conducted between May 2017 and May 2018. Ventilated infants born at less than 37 weeks' gestational age and ready to be extubated were included and randomized to either the NHFOV or NCPAP group. Primary outcomes were the incidence of reintubation within 1 week and the Pco₂ level within 6 h.

RESULTS

A total of 206 preterm infants were included. Of them, 127 (61.7%) were diagnosed with respiratory distress syndrome, 53 (25.7%) with ARDS, and 26 (12.6%) with both respiratory distress syndrome and ARDS. Comparing with NCPAP, NHFOV significantly reduced the reintubation rate (16:87 vs 35:68; 95% CI, 0.18-0.70; P = .002), especially in the subgroup with a gestational age of ≤ 32 weeks (12:34 vs 25:20; 95% CI, 0.12-0.68; P = .004). The Pco₂ level was also significant lower in the NHFOV group (49.6 ± 8.7 vs 56.9 ± 9.9; 95% CI, -9.95 to -4.80; P = < .001). Moreover, NHFOV significantly reduced the reintubation rate in preterm infants with ARDS (10:33 vs 21:15; 95% CI, 0.08-0.57; P = .002).

CONCLUSIONS

NHFOV was shown to be superior to NCPAP in avoiding reintubation, especially in very preterm infants and those infants diagnosed with ARDS.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT03140891; URL: www.clinicaltrials.gov.

Noninvasive high-frequency oscillatory ventilation versus nasal continuous positive airway pressure in preterm infants with respiratory distress syndrome: a randomized controlled trial

Background: Respiratory distress syndrome (RDS) is one of the main causes of mortality in premature neonates. Treatment of these neonates with invasive mechanical ventilation has side effects such as chronic pulmonary diseases. Noninvasive ventilation, such as nasal continuous positive airway pressure (NCPAP) and nasal high-frequency oscillation ventilation (NHFOV), has shown to reduce the burden of chronic lung disease. NHFOV is a promising new mode of noninvasive ventilation and may reduce the need for mechanical ventilation and reduce possible complications. In this study, we hypothesized that early NHFOV would reduce the need for invasive respiratory support in comparison to NCPAP in preterm neonates with RDS.Methods: One hundred twenty-four neonates between 28 to 34 weeks of gestational age (GA) with RDS hospitalized at Imam Khomeini Hospital, Ahvaz in 2016 were included in this randomized controlled study. The primary outcomes were the failure of NHFOV and NCPAP within 72 h after birth. The secondary outcomes were the duration of invasive ventilation and possible side effects.Results: Out of 124 neonates in this study, 63 and 61 neonates were studied in the NHFOV and NCPAP groups, respectively. There were no significant differences between NHFOV (6.5%) and NCPAP (14.1%) groups in terms of rates of primary consequences (p = .13). However, the duration of noninvasive ventilation in NHFOV was significantly less than that of NCPAP group (p = .01).Conclusion: In our study group, preterm infants from 28 to 34 weeks of GA, NHFOV did not reduce the need for mechanical ventilation during the first 72 h after birth compared to NCPAP; however, the duration of noninvasive ventilation in the NHFOV group was significantly shorter.

Bronchopulmonary Dysplasia: Crosstalk Between PPARγ, WNT/β-Catenin and TGF-β Pathways; The Potential Therapeutic Role of PPARγ Agonists

Bronchopulmonary dysplasia (BPD) is a serious pulmonary disease which occurs in preterm infants. Mortality remains high due to a lack of effective treatment, despite significant progress in neonatal resuscitation. In BPD, a persistently high level of canonical WNT/β-catenin pathway activity at the canalicular stage disturbs the pulmonary maturation at the saccular and alveolar stages. The excessive thickness of the alveolar wall impairs the normal diffusion of oxygen and carbon dioxide, leading to hypoxia. Transforming growth factor (TGF-β) up-regulates canonical WNT signaling and inhibits the peroxysome proliferator activated receptor gamma (PPARγ). This profile is observed in BPD, especially in animal models. Following a premature birth, hypoxia activates the canonical WNT/TGF-β axis at the expense of PPARγ. This gives rise to the differentiation of fibroblasts into myofibroblasts, which can lead to pulmonary fibrosis that impairs the respiratory function after birth, during childhood and even adulthood. Potential therapeutic treatment could target the inhibition of the canonical WNT/TGF-β pathway and the stimulation of PPARγ activity, in particular by the administration of nebulized PPARγ agonists.

The Effect of Noninvasive High-Frequency Oscillatory Ventilation on Desaturations and Bradycardia in Very Preterm Infants: A Randomized Crossover Trial

Noninvasive high-frequency oscillatory ventilation compared with nasal continuous positive airway pressure significantly reduced the number of desaturations and bradycardia in preterm infants. However, noninvasive high-frequency oscillatory ventilation was associated with increased oxygen requirements and higher heart rates.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trial Registry: ACTRN12616001516471.

Unitary Physiology

The common relationships among a great variety of biological phenomena seem enigmatic when considered solely at the level of the phenotype. The deep connections in physiology, for example, between the effects of maternal food restriction in utero and the subsequent incidence of metabolic syndrome in offspring, the effects of microgravity on cell polarity and reproduction in yeast, stress effects on jellyfish, and their endless longevity, or the relationship between nutrient abundance and the colonial form in slime molds, are not apparent by phenotypic observation. Yet all of these phenomena are ultimately determined by the Target of Rapamycin (TOR) gene and its associated signaling complexes. In the same manner, the unfolding of evolutionary physiology can be explained by a comparable application of the common principle of cell-cell signaling extending across complex developmental and phylogenetic traits. It is asserted that a critical set of physiologic and phenotypic adaptations emanated from a few crucial, ancestral receptor gene duplications that enabled the successful terrestrial transition of vertebrates from water to land. In combination, mTor and its cognate receptors and a few crucial genetic duplications provide a mechanistic common denominator across a diverse spectrum of biological responses. The proper understanding of their purpose yields a unified concept of physiology and its evolutionary development. © 2018 American Physiological Society. Compr Physiol 8:761-771, 2018.

Noninvasive high-frequency oscillatory ventilation versus nasal continuous positive airway pressure in preterm infants with moderate-severe respiratory distress syndrome: A preliminary report

OBJECTIVE

The aim of this study was to compare the effect of noninvasive high-frequency oscillatory ventilation (nHFOV) with nasal continuous positive airway pressure (nCPAP) in preterm infants with moderate-severe respiratory distress syndrome (RDS) after surfactant administration via INSURE (intubation, surfactant, extubation) method on the need for invasive mechanical ventilation (IMV).

METHODS

A total of 81 infants with a gestational age (GA) of 28-34 weeks were eligible and were randomized to nCPAP (n = 42) or to nHFOV (n = 39). The need for IMV was the primary outcome. The incidence of bronchopulmonary dysplasia (BPD), occurrence of intraventricular hemorrhage (IVH), and air leaks, and mortality were considered as secondary outcomes.

RESULT

A total 76 infants finally completed the study. The need for IMV was significantlylower in the nHFOV group compared with the nCPAP group(24.3% vs 56.4%, P < 0.01). The incidence of IVH, air leaks or BPD was similar between the two groups. In addition, the mortality rate was not statistically different.

CONCLUSION

In this prospective, randomized controlled study, nHFOV significantly reduced the need for IMV as compared with nCPAP in preterm infants with moderate-severe RDS without increase in adverse effects.

Regulation of the angiotensin II-p22phox-reactive oxygen species signaling pathway, apoptosis and 8-oxoguanine-DNA glycosylase 1 retrieval in hyperoxia-induced lung injury and fibrosis in rats

The present study was designed to explore the impact of hyperoxia on lung injury and fibrosis via the angiotensin II (AngII)-p22phox-reactive oxygen species (ROS) signaling pathway, apoptosis and 8-oxoguanine-DNA glycosylase 1 (OGG1) repair enzyme. Newborn Sprague-Dawley rats were randomly divided in the newborn air group, newborn hyperoxia group and newborn intervention group, the latter of which was administered the chymotrypsin inhibitor, 2-(5-formylamino-6-oxo-2-phenyl-1, 6-dihydropyrimidine-1-yl)-N-[4-dioxo-1-phenyl-7-(2-pyridyloxy)] 2-heptyl-acetamide (NK3201). A group of adult rats also received hyperoxic treatment. Histomorphological changes in lung tissues were dynamically observed. AngII, ROS, angiotensin type 1 receptor (AT₁R) and p22phox messenger RNA (mRNA) levels, and OGG1 and peroxisome proliferator-activated receptor-γ (PPARγ) protein levels in the lung tissues were detected at various times after hyperoxia. Hyperoxia led to traumatic changes in the lungs of newborn rats that resulted in decreased viability, increased mortality, morphological changes and the apoptosis of alveolar type II epithelial cells (AT-II), as well as increased expression levels of AngII, AT₁R and p22phox, which would ultimately lead to secondary diseases. NK3201 significantly inhibited the hyperoxia-induced increased expression of AngII, AT₁R and p22phox and further promoted OGG1 and PPARγ protein expression, thus reducing the intrapulmonary ROS level, the apoptotic index and caspase-3 levels. However, the adult hyperoxia group only exhibited tachypnea and reduced viability. This study suggested that the AngII-p22phox-ROS signaling pathway, PPARγ and OGG1 together contributed to the hyperoxia-induced lung injury and that NK3201 was able to reverse the effects of hyperoxia.

[Research advances in noninvasive high-frequency oscillatory ventilation in neonates]

Noninvasive ventilation is an important respiratory management technique for the treatment of mild or moderate respiratory failure in the neonatal intensive care unit. Its reasonable application can effectively avoid the use of invasive ventilation and related complications. Recent studies have found that noninvasive high-frequency oscillatory ventilation has the advantages of both nasal continuous positive airway pressure and high-frequency ventilation and can rapidly improve oxygenation, effectively remove carbon dioxide, and improve respiratory failure. Therefore, it is considered a new and effective noninvasive ventilation mode. There are many studies on the rational use, efficacy, and safety of noninvasive high-frequency oscillatory ventilation in neonates around the world. This article reviews the advances in the clinical studies on noninvasive high-frequency oscillatory ventilation in neonates.

[Research advances in noninvasive high-frequency oscillatory ventilation in neonates]

Noninvasive ventilation is an important respiratory management technique for the treatment of mild or moderate respiratory failure in the neonatal intensive care unit. Its reasonable application can effectively avoid the use of invasive ventilation and related complications. Recent studies have found that noninvasive high-frequency oscillatory ventilation has the advantages of both nasal continuous positive airway pressure and high-frequency ventilation and can rapidly improve oxygenation, effectively remove carbon dioxide, and improve respiratory failure. Therefore, it is considered a new and effective noninvasive ventilation mode. There are many studies on the rational use, efficacy, and safety of noninvasive high-frequency oscillatory ventilation in neonates around the world. This article reviews the advances in the clinical studies on noninvasive high-frequency oscillatory ventilation in neonates.

Limiting ventilator-associated lung injury in a preterm porcine neonatal model

PURPOSE

Preterm infants are prone to respiratory distress syndrome (RDS), with severe cases requiring mechanical ventilation for support. However, there are no clear guidelines regarding the optimal ventilation strategy. We hypothesized that airway pressure release ventilation (APRV) would mitigate lung injury in a preterm porcine neonatal model.

METHODS

Preterm piglets were delivered on gestational day 98 (85% of 115day term), instrumented, and randomized to volume guarantee (VG; n=10) with low tidal volumes (5.5cm³kg^-1) and PEEP 4cmH₂O or APRV (n=10) with initial ventilator settings: P_High 18cmH₂O, P_Low 0cmH₂O, T_High 1.30s, T_Low 0.15s. Ventilator setting changes were made in response to clinical parameters in both groups. Animals were monitored continuously for 24hours.

RESULTS

The mortality rates between the two groups were not significantly different (p>0.05). The VG group had relatively increased oxygen requirements (F_iO₂ 50%±9%) compared with the APRV group (F_iO₂ 28%±5%; p>0.05) and a decrease in PaO₂/FiO₂ ratio (VG 162±33mmHg; APRV 251±45mmHg; p<0.05). The compliance of the VG group (0.51±0.07L·cmH₂O^-1) was significantly less than the APRV group (0.90±0.06L·cmH₂O^-1; p<0.05).

CONCLUSION

This study demonstrates that APRV improves oxygenation and compliance as compared with VG. This preliminary work suggests further study into the clinical uses of APRV in the neonate is warranted.

LEVEL OF EVIDENCE

Not Applicable (Basic Science Animal Study).

Non-invasive high-frequency ventilation versus bi-phasic continuous positive airway pressure (BP-CPAP) following CPAP failure in infants <1250 g: a pilot randomized controlled trial

OBJECTIVE

Non-invasive high-frequency ventilation (NIHFV), a relatively new modality, is gaining popularity despite limited data. We sought to evaluate the effectiveness of NIHFV versus bi-phasic continuous positive airway pressure (BP-CPAP) in preterm infants failing CPAP.

STUDY DESIGN

Infants with BW<1250 g on CPAP were randomly assigned to NIHFV or BP-CPAP if they met pre-determined criteria for CPAP failure. Infants were eligible for randomization after 72 h age and until 2000 g. Guidelines for adjustment of settings and criteria for failure of assigned mode were implemented. The primary aim was to assess feasibility of a larger trial. In addition, failure of assigned non-invasive respiratory support (NRS) mode, invasive mechanical ventilation (MV) 72 h and 7 days post-randomization, and bronchopulmonary dysplasia (BPD) were assessed.

RESULTS

Thirty-nine infants were randomized to NIHFV (N=16) or BP-CPAP (N=23). There were no significant differences in mean (s.d.) postmenstrual age (28.6 (1.5) versus 29.0 (2.3) weeks, P=0.47), mean (s.d.) weight at randomization (965.0 (227.0) versus 958.1 (310.4) g, P=0.94) or other baseline demographics between the groups. Failure of assigned NRS mode was lower with NIHFV (37.5 versus 65.2%, P=0.09), although not statistically significant. There were no differences in rates of invasive MV 72 h and 7 days post-randomization or BPD.

CONCLUSION

NIHFV was not superior to BP-CPAP in this pilot study. Effectiveness of NIHFV needs to be proven in larger multi-center, appropriately powered trials before widespread implementation.

Bronchopulmonary dysplasia: new becomes old again!

Despite the many advances in neonatology, bronchopulmonary dysplasia (BPD) continues to be a frustrating disease of prematurity. BPD is a disease which is defined oddly by its treatment rather than its pathophysiology, leading to frequently changing nomenclature which has widespread implications on our ability to both understand and follow the progression of BPD. As various treatment modalities for BPD were developed and a larger number of extremely preterm infants survived, the "old" BPD based on lung injury from oxygen therapy and mechanical ventilation transitioned into a "new" BPD focused more on the interruption of normal development. However, the interruption of normal development does not solely apply to lung development. The effects of prematurity on vascular development cannot be overstated and pulmonary vascular disease has become the new frontier of BPD. As we begin to better understand the complex, multifactorial pathophysiology of BPD, it is necessary to again focus on appropriate, pathology-driven nomenclature that can effectively describe the multiple clinical phenotypes of BPD.

High-Frequency Ventilation as a Mode of Noninvasive Respiratory Support

High-frequency ventilation (HFV) as a mode of noninvasive respiratory support (NRS) in preterm neonates is gaining popularity. Benefits may accrue from combining the ventilatory efficiency of HFV delivered through a noninvasive interface, enhancing respiratory support while potentially limiting lung injury. Current evidence suggests that noninvasive HFV (NIHFV) may be superior to other NRS modes in eliminating carbon dioxide and preventing endotracheal ventilation after failure of other NRS modes. Animal data suggest NIHFV may promote improved alveolar development compared to endotracheal ventilation. However, adequately powered large-scale controlled trials are required to evaluate efficacy and safety prior to widespread use of NIHFV.

Non-invasive high-frequency oscillatory ventilation in neonates: review of physiology, biology and clinical data

Non-invasive high-frequency oscillatory ventilation (NHFOV) consists of the application of a bias flow generating a continuous distending positive pressure with superimposed oscillations, which have constant frequency and active expiratory phase. NHFOV matches together the advantages of high-frequency ventilation (no need for synchronisation, high efficacy in removing CO₂) and nasal continuous positive airway pressure (CPAP) (non-invasive interface, increase in functional residual capacity allowing oxygenation to improve). There is enough clinical expertise demonstrating that NHFOV may be tried in some selected cases, in whom CPAP or conventional non-invasive ventilation have failed. Nonetheless, there are no clear data about its clinical usefulness and there is a need for randomised controlled studies. Our purpose is to review the physiology and biological effects of NHFOV, to present the current clinical evidence on its use, to provide some guiding principles to clinicians and suggest directions for further research.

High-frequency ventilation for non-invasive respiratory support of neonates

Non-invasive respiratory support is increasingly used in lieu of intubated ventilator support for the management of neonatal respiratory failure, particularly in very low birth weight infants at risk for bronchopulmonary dysplasia. The optimal approach and mode for non-invasive support remains uncertain. This article reviews the application of high-frequency ventilation for non-invasive respiratory support in neonates, including basic science studies on mechanics of gas exchange, animal model investigations, and a review of current clinical use in human neonates.

The Effect of Continuous Positive Airway Pressure in a Mouse Model of Hyperoxic Neonatal Lung Injury

BACKGROUND

Continuous positive airway pressure (CPAP) and supplemental oxygen have become the mainstay of neonatal respiratory support in preterm infants. Although oxygen therapy is associated with respiratory morbidities including bronchopulmonary dysplasia (BPD), the long-term effects of CPAP on lung function are largely unknown. We used a hyperoxia-induced mouse model of BPD to explore the effects of daily CPAP in the first week of life on later respiratory system mechanics.

OBJECTIVE

We wanted to test the hypothesis that daily CPAP in a newborn-mouse model of BPD improves longer-term respiratory mechanics.

METHODS

Mouse pups from C57BL/6 pregnant dams were exposed to room air (RA) or hyperoxia (50% O2, 24 h/day) for the first postnatal week with or without exposure to daily CPAP (6 cm H2O, 3 h/day). Respiratory system resistance (Rrs) and compliance (Crs) were measured following a subsequent 2-week period of RA recovery. Additional measurements included radial alveolar and macrophage counts.

RESULTS

Mice exposed to hyperoxia had significantly elevated Rrs, decreased Crs, reduced alveolarization and increased macrophage counts at 3 weeks when compared to RA-treated mice. Daily CPAP treatment significantly improved Rrs, Crs and alveolarization and decreased lung macrophage infiltration in the hyperoxia-exposed pups.

CONCLUSIONS

We have demonstrated that daily CPAP had a longer-term benefit on baseline respiratory system mechanics in a neonatal mouse model of BPD. We speculate that this beneficial effect of CPAP was the consequence of a decrease in the inflammatory response and resultant alveolar injury associated with hyperoxic lung injury in newborns.

Understanding the Impact of Infection, Inflammation, and Their Persistence in the Pathogenesis of Bronchopulmonary Dysplasia

The concerted interaction of genetic and environmental factors acts on the preterm human immature lung with inflammation being the common denominator leading to the multifactorial origin of the most common chronic lung disease in infants - -bronchopulmonary dysplasia (BPD). Adverse perinatal exposure to infection/inflammation with added insults like invasive mecha nical ventilation, exposure to hyperoxia, and sepsis causes persistent immune dysregulation. In this review article, we have attempted to analyze and consolidate current knowledge about the role played by persistent prenatal and postnatal inflammation in the pathogenesis of BPD. While some parameters of the early inflammatory response (neutrophils, cytokines, etc.) may not be detectable after days to weeks of exposure to noxious stimuli, they have already initiated the signaling pathways of the inflammatory process/immune cascade and have affected permanent defects structurally and functionally in the BPD lungs. Hence, translational research aimed at prevention/amelioration of BPD needs to focus on dampening the inflammatory response at an early stage to prevent the cascade of events leading to lung injury with impaired healing resulting in the pathologic pulmonary phenotype of alveolar simplification and dysregulated vascularization characteristic of BPD.

On the evolution of the pulmonary alveolar lipofibroblast

The pulmonary alveolar lipofibroblast was first reported in 1970. Since then its development, structure, function and molecular characteristics have been determined. Its capacity to actively absorb, store and 'traffic' neutral lipid for protection of the alveolus against oxidant injury, and for the active supply of substrate for lung surfactant phospholipid production have offered the opportunity to identify a number of specialized functions of these strategically placed cells. Namely, Parathyroid Hormone-related Protein (PTHrP) signaling, expression of Adipocyte Differentiation Related Protein, leptin, peroxisome proliferator activator receptor gamma, and the prostaglandin E2 receptor EP2- which are all stretch-regulated, explaining how and why surfactant production is 'on-demand' in service to ventilation-perfusion matching. Because of the central role of the lipofibroblast in vertebrate lung physiologic evolution, it is a Rosetta Stone for understanding how and why the lung evolved in adaptation to terrestrial life, beginning with the duplication of the PTHrP Receptor some 300 mya. Moreover, such detailed knowledge of the workings of the lipofibroblast have provided insight to the etiology and effective treatment of Bronchopulmonary Dysplasia based on physiologic principles rather than on pharmacology.

Non-invasive Ventilation in Premature Infants: Based on Evidence or Habit

Despite surfactant and mechanical ventilation being the standard of care for preterm infants with respiratory failure, non-invasive respiratory support is increasingly being employed in neonatal units. The latter can be accomplished in a variety of ways but none of them have been proven so far to be superior to intubation and mechanical ventilation. Nonetheless, they appear to be safe and effective in experienced hands. This article relates to the use of non-invasive forms of respiratory support and evidence is reviewed from the clinical trials which have evaluated the use of these techniques.

Postnatal inflammation in the pathogenesis of bronchopulmonary dysplasia

Exposure to hyperoxia, invasive mechanical ventilation, and systemic/local sepsis are important antecedents of postnatal inflammation in the pathogenesis of bronchopulmonary dysplasia (BPD). This review will summarize information obtained from animal (baboon, lamb/sheep, rat and mouse) models that pertain to the specific inflammatory agents and signaling molecules that predispose a premature infant to BPD.

Rosiglitazone, a peroxisome proliferator-activated receptor-γ agonist, restores alveolar and pulmonary vascular development in a rat model of bronchopulmonary dysplasia

PURPOSE

We tested whether rosiglitazone (RGZ), a peroxisome proliferator-activated receptor-γ agonist, can restore alveolar development and vascular growth in a rat model of bronchopulmonary dysplasia (BPD).

MATERIALS AND METHODS

A rat model of BPD was induced through intra-amniotic delivery of lipopolysaccharide (LPS) and postnatal hyperoxia (80% for 7 days). RGZ (3 mg/kg/d, i.p.) or vehicle was given daily to rat pups for 14 days. This model included four experimental groups: No BPD+vehicle (V), No BPD+RGZ, BPD+V, and BPD+RGZ. On D14, alveolarization, lung vascular density, and right ventricular hypertrophy (RVH) were evaluated.

RESULTS

Morphometric analysis revealed that the BPD+RGZ group had significantly smaller and more complex airspaces and larger alveolar surface area than the BPD+V group. The BPD+RGZ group had significantly greater pulmonary vascular density than the BPD+V group. Western blot analysis revealed that significantly decreased levels of vascular endothelial growth factor (VEGF) and its receptor VEGFR-2 by the combined exposure to intra-amniotic LPS and postnatal hyperoxia were restored by the RGZ treatment. RVH was significantly lesser in the BPD+RGZ group than in the BPD+V group.

CONCLUSION

These results suggest that RGZ can restore alveolar and pulmonary vascular development and lessen pulmonary hypertension in a rat model of BPD.

On the evolution of development

Perhaps development is more than just morphogenesis. We now recognize that the conceptus expresses epigenetic marks that heritably affect it phenotypically, indicating that the offspring are to some degree genetically autonomous, and that ontogeny and phylogeny may coordinately determine the fate of such marks. This scenario mechanistically links ecology, ontogeny and phylogeny together as an integrated mechanism for evolution for the first time. As a functional example, the Parathyroid Hormone-related Protein (PTHrP) signaling duplicated during the Phanerozoic water-land transition. The PTHrP signaling pathway was critical for the evolution of the skeleton, skin barrier, and lung function, based on experimental evidence, inferring that physiologic stress can profoundly affect adaptation through internal selection, giving seminal insights to how and why vertebrates were able to evolve from water to land. By viewing evolution from its inception in unicellular organisms, driven by competition between pro- and eukaryotes, the emergence of complex biologic traits from the unicellular cell membrane offers a novel way of thinking about the process of evolution from its beginnings, rather than from its consequences as is traditionally done. And by focusing on the epistatic balancing mechanisms for calcium and lipid homeostasis, the evolution of unicellular organisms, driven by competition between pro- and eukaryotes, gave rise to the emergence of complex biologic traits derived from the unicellular plasma lemma, offering a unique way of thinking about the process of evolution. By exploiting the cellular-molecular mechanisms of lung evolution as ontogeny and phylogeny, the sequence of events for the evolution of the skin, kidney and skeleton become more transparent. This novel approach to the evolution question offers equally novel insights to the primacy of the unicellular state, hologenomics and even a priori bioethical decisions.

High-frequency oscillatory ventilation combined with volume guarantee in a neonatal animal model of respiratory distress syndrome

Objective. To assess volume guarantee (VG) ventilation combined with high-frequency oscillatory ventilation (HFOV) strategy on PaCO₂ regulation in an experimental model of neonatal distress syndrome. Methods. Six 2-day-old piglets weighing 2.57 ± 0.26 kg were used for this interventional experimental study. Animals were ventilated during physiologic lung conditions and after depletion of lung surfactant by bronchoalveolar lavage (BAL). The effect of HFOV combined with VG on PaCO₂ was evaluated at different high-frequency expired tidal volume (VThf) at constant frequency (f_R) and mean airway pressure (mPaw). Fluctuations of the pressure (ΔPhf) around the mPaw and PaCO₂ were analyzed before and after lung surfactant depletion. Results. PaCO₂ levels were inversely proportional to VThf. In the physiological lung condition, an increase in VThf caused a significant decrease in PaCO₂ and an increase in ΔPhf. After BAL, PaCO₂ did not change as compared with pre-BAL situation as the VThf remained constant by the ventilator. Conclusions. In this animal model, using HFOV combined with VG, changes in the VThf settings induced significant modifications in PaCO₂. After changing the lung condition by depletion of surfactant, PaCO₂ remained unchanged, as the VThf setting was maintained constant by modifications in the ΔPhf done by the ventilator.

Curcumin protects the developing lung against long-term hyperoxic injury

Curcumin, a potent anti-inflammatory and antioxidant agent, modulates peroxisome proliferator-activated receptor-γ signaling, a key molecule in the etiology of bronchopulmonary dysplasia (BPD). We have previously shown curcumin's acute protection against neonatal hyperoxia-induced lung injury. However, its longer-term protection against BPD is not known. Hypothesizing that concurrent treatment with curcumin protects the developing lung against hyperoxia-induced lung injury long-term, we determined if curcumin protects against hyperoxic neonatal rat lung injury for the first 5 days of life, as determined at postnatal day (PND) 21. One-day-old rat pups were exposed to either 21 or 95% O₂ for 5 days with or without curcumin treatment (5 mg/kg) administered intraperitoneally one time daily, following which the pups grew up to PND21 in room air. At PND21 lung development was determined, including gross and cellular structural and functional effects, and molecular mediators of inflammatory injury. To gain mechanistic insights, embryonic day 19 fetal rat lung fibroblasts were examined for markers of apoptosis and MAP kinase activation following in vitro exposure to hyperoxia for 24 h in the presence or absence of curcumin (5 μM). Curcumin effectively blocked hyperoxia-induced lung injury based on systematic analysis of markers for lung injury (apoptosis, Bcl-2/Bax, collagen III, fibronectin, vimentin, calponin, and elastin-related genes) and lung morphology (radial alveolar count and alveolar septal thickness). Mechanistically, curcumin prevented the hyperoxia-induced increases in cleaved caspase-3 and the phosphorylation of Erk1/2. Molecular effects of curcumin, both structural and cytoprotective, suggest that its actions against hyperoxia-induced lung injury are mediated via Erk1/2 activation and that it is a potential intervention against BPD.

Effects of different ventilation strategies on lung injury in newborn rabbits

BACKGROUND

The results from experimental and clinical studies have shown that mechanical ventilation (MV) and/or hyperoxia may aggravate a pre-existing lung injury, or even cause lung injury in healthy lungs, despite the fact that it might be the only life-saving intervention available to a patient. The present study was designed to investigate the roles of MV and hyperoxia in the pathogenesis of lung injury.

METHODS

Newborn New Zealand white rabbits were randomly assigned to an unventilated air control group or to one of the 2 × 3 × 3 ventilation strategies using a factorial design. The experimental groups were assigned different fractions of inspired oxygen (FiO(2)), peak inspiratory pressures (PIP), and respiratory times (RT). The lung wet-to-dry ratio (W/D), lung histopathology scores, and cells in the bronchoalveolar lavage fluid (BALF) were analyzed for each group. The apoptosis levels were studied by immunohistochemistry and a terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) assay.

RESULTS

Different ventilation regimes induced alterations in microvascular permeability, differential histopathological grading, WBC and/or neutrophil and/or lymphocyte influx, and apoptosis levels; moreover, there were significant correlations and interaction effects between these indices.

CONCLUSIONS

Our data demonstrate that different ventilation regimes can induce lung injury and that the interaction effects of the FiO(2), the PIP and the RT may play crucial roles in the pathogenesis of lung injury.

Effect of amplitude and inspiratory time in a bench model of non-invasive HFOV through nasal prongs

BACKGROUND AND OBJECTIVES

Non-invasive high frequency oscillatory ventilation through nasal prongs (nHFOV) has been proposed to combine the advantages of oscillatory pressure waveform and non-invasive interface. We studied the effect of oscillation amplitude and inspiratory time on the pressure transmission and tidal volume delivery through different nasal prongs.

METHODS

In vitro mechanical study on a previously described bench model of nHFOV. The model was built connecting SM3100A tubings to a neonatal lung model, via two differently sized binasal prongs. A circuit with no nasal prongs was used as control. Tidal volume (T(v) ), oscillatory pressure ratio (ΔP(dist) /ΔP(prox) ), and ventilation (DCO(2) ) were measured across a range of amplitudes and inspiratory times (I(T) ). Measurements were performed with a low-dead space hot wire anemometer coupled with a pressure transducer.

RESULTS

Using both nasal prongs, T(v) , ΔP(dist) /ΔP(prox) , and DCO(2) were 83%, 40%, and 71%, respectively, of those provided with the control circuit. No differences were noticed between small and large prongs. T(v) and ΔP(prox) were linked by a quadratic relationship. T(v) plateaus for amplitude values >65 cmH(2) O. ΔP(dist) /ΔP(prox) shows same tendency. Same results were obtained with both types of prongs and with increasing I(T) . On the whole, mean T(v) was higher with I(T) at 50% than at 33% (2.4 ml vs. 1.4 ml; P < 0.001).

CONCLUSIONS

Changing oscillation amplitude and I(T) has a significant effect on ventilation. Varying these two parameters provides a theoretical T(v) within the ideal values for HFOV also using the smallest nasal prongs.

Noninvasive respiratory support in the preterm infant

Multiple randomized controlled trials have suggested that nasal intermittent positive pressure ventilation, compared with nasal continuous airway pressure, prevents extubation failure and may decrease bronchopulmonary dysplasia. This article summarizes these studies and suggests strategies for the use of nasal intermittent positive pressure ventilation in neonates.

PPARγ Signaling Mediates the Evolution, Development, Homeostasis, and Repair of the Lung

Epithelial-mesenchymal interactions mediated by soluble growth factors determine the evolution of vertebrate lung physiology, including development, homeostasis, and repair. The final common pathway for all of these positively adaptive properties of the lung is the expression of epithelial parathyroid-hormone-related protein, and its binding to its receptor on the mesenchyme, inducing PPARγ expression by lipofibroblasts. Lipofibroblasts then produce leptin, which binds to alveolar type II cells, stimulating their production of surfactant, which is necessary for both evolutionary and physiologic adaptation to atmospheric oxygen from fish to man. A wide variety of molecular insults disrupt such highly evolved physiologic cell-cell interactions, ranging from overdistention to oxidants, infection, and nicotine, all of which predictably cause loss of mesenchymal peroxisome-proliferator-activated receptor gamma (PPARγ) expression and the transdifferentiation of lipofibroblasts to myofibroblasts, the signature cell type for lung fibrosis. By exploiting such deep cell-molecular functional homologies as targets for leveraging lung homeostasis, we have discovered that we can effectively prevent and/or reverse the deleterious effects of these pathogenic agents, demonstrating the utility of evolutionary biology for the prevention and treatment of chronic lung disease. By understanding mechanisms of health and disease as an evolutionary continuum rather than as dissociated processes, we can evolve predictive medicine.