Impaired spreading of surfactant phospholipids in the lungs of newborn rats with pulmonary hypoplasia as a model of congenital diaphragmatic hernia induced by nitrofen

Assessment of the nitrofen model of congenital diaphragmatic hernia and of the dysregulated factors involved in pulmonary hypoplasia

PURPOSE

To study pulmonary hypoplasia (PH) associated with congenital diaphragmatic hernia (CDH), investigators have been employing a fetal rat model based on nitrofen administration to dams. Herein, we aimed to: (1) investigate the validity of the model, and (2) synthesize the main biological pathways implicated in the development of PH associated with CDH.

METHODS

Using a defined strategy, we conducted a systematic review of the literature searching for studies reporting the incidence of CDH or factors involved in PH development. We also searched for PH factor interactions, relevance to lung development and to human PH.

RESULTS

Of 335 full-text articles, 116 reported the incidence of CDH after nitrofen exposure or dysregulated factors in the lungs of nitrofen-exposed rat fetuses. CDH incidence: 54% (27-85%) fetuses developed a diaphragmatic defect, whereas the whole litter had PH in varying degrees. Downregulated signaling pathways included FGF/FGFR, BMP/BMPR, Sonic Hedgehog and retinoid acid signaling pathway, resulting in a delay in early epithelial differentiation, immature distal epithelium and dysfunctional mesenchyme.

CONCLUSIONS

The nitrofen model effectively reproduces PH as it disrupts pathways that are critical for lung branching morphogenesis and alveolar differentiation. The low CDH rate confirms that PH is an associated phenomenon rather than the result of mechanical compression alone.

Follistatin-like 1 expression is decreased in the alveolar epithelium of hypoplastic rat lungs with nitrofen-induced congenital diaphragmatic hernia

BACKGROUND/PURPOSE

Pulmonary hypoplasia (PH), characterized by incomplete alveolar development, remains a major therapeutic challenge associated with congenital diaphragmatic hernia (CDH). Follistatin-like 1 (Fstl1) is a crucial regulator of alveolar formation and maturation, which is strongly expressed in distal airway epithelium. Fstl1-deficient mice exhibit reduced airspaces, impaired alveolar epithelial cell differentiation, and insufficient production of surfactant proteins similar to PH in human CDH. We hypothesized that pulmonary Fstl1 expression is decreased during alveolarization in the nitrofen-induced CDH model.

METHODS

Timed-pregnant rats received nitrofen or vehicle on gestational day 9 (D9). Fetal lungs were harvested on D18 and D21 and divided into control-/nitrofen-exposed specimens. Alveolarization was assessed using morphometric analysis techniques. Pulmonary gene expression of Fstl1 was determined by qRT-PCR. Immunofluorescence-double-staining for Fstl1 and alveolar epithelial marker surfactant protein C (SP-C) was performed to evaluate protein expression/localization.

RESULTS

Radial alveolar count was significantly reduced in hypoplastic lungs of nitrofen-exposed fetuses with significant down regulation of Fstl1 mRNA expression on D18 and D21 compared to controls. Confocal-laser-scanning-microscopy revealed strikingly diminished Fstl1 immunofluorescence and SP-C expression in distal alveolar epithelium of nitrofen-exposed fetuses with CDH-associated PH on D18 and D21 compared to controls.

CONCLUSIONS

Decreased expression of Fstl1 in alveolar epithelium may disrupt alveolarization and pulmonary surfactant production, thus contributing to the development of PH in the nitrofen-induced CDH model.

LEVEL OF EVIDENCE

2b (Centre for Evidence-Based Medicine, Oxford).

Prenatal administration of all-trans retinoic acid upregulates leptin signaling in hypoplastic rat lungs with experimental congenital diaphragmatic hernia

PURPOSE

Pulmonary hypoplasia (PH), characterized by alveolar immaturity, is one of the leading causes of respiratory insufficiency in newborns with congenital diaphragmatic hernia (CDH). Leptin (Lep) and its receptor (Lep-R) play an important role in fetal lung growth by stimulating alveolar differentiation and maturation. Lep and Lep-R are strongly expressed by alveolar cells during the saccular stage of fetal lung development. Lep-deficient mice exhibit decreased alveolarization with reduced pulmonary surfactant phospholipid synthesis, similar to human and nitrofen-induced PH. Prenatal administration of all-trans retinoic acid (ATRA) has been shown to stimulate alveolarization in nitrofen-induced PH. Recent studies have demonstrated that Lep and Lep-R expression in developing lungs is regulated by ATRA. We hypothesized that prenatal treatment with ATRA increases pulmonary Lep and Lep-R expression in the nitrofen model of CDH-associated PH.

METHODS

Time-mated rats received either 100 mg nitrofen or vehicle via oral-gastric lavage on embryonic day 9.5 (E9.5). Control and nitrofen-exposed dams were randomly assigned to either intraperitoneal ATRA (5 mg/kg/d) or placebo administration on E18.5, E19.5 and E20.5. Fetal lungs were harvested on E21.5, and divided into Control+Placebo, Control+ATRA, Nitrofen+Placebo and Nitrofen+ATRA. Alveolarization was assessed using stereo- and morphometric analysis techniques. Surfactant phospholipid synthesis was analyzed by labeling for surfactant protein B (SP-B). Pulmonary gene expression levels of Lep and Lep-R were determined using quantitative real-time polymerase chain reaction. Immunohistochemical staining for Lep and Lep-R was performed to evaluate alveolar protein expression and localization.

RESULTS

In vivo administration of ATRA resulted in significantly increased lung-to-body weight ratio with enhanced radial alveolar count and decreased mean linear intercept compared to placebo treatment. Immunofluorescence analysis demonstrated markedly increased pulmonary SP-B expression in Nitrofen+ATRA compared to Nitrofen+Placebo. Relative mRNA expression of Lep and Lep-R was significantly increased in Nitrofen+ATRA compared to Nitrofen+Placebo. Lep and Lep-R immunoreactivity was markedly increased in interstitial and alveolar epithelial cells of Nitrofen+ATRA compared to Nitrofen+Placebo.

CONCLUSION

Increased Lep and Lep-R expression after prenatal administration of ATRA in nitrofen-induced PH suggests that ATRA may have therapeutic potential in attenuating CDH-associated PH by stimulating alveolarization and de novo surfactant production.

Evidence for decreased lipofibroblast expression in hypoplastic rat lungs with congenital diaphragmatic hernia

PURPOSE

Pulmonary hypoplasia (PH) is a serious condition in newborns with congenital diaphragmatic hernia (CDH). Lipid-containing interstitial fibroblasts (LIFs) play an essential role in fetal lung maturation by stimulating alveolarization and lipid homeostasis. In rodents, LIFs are first evident during the canalicular phase of lung development with a significant increase over the last 4 days of gestation. Adipocyte differentiation-related protein (ADRP), a functional lipogenic molecular marker characterizing LIFs, is highly expressed in fetal lungs during this critical time period. We hypothesized that LIF expression in hypoplastic rat lungs is decreased in the nitrofen-induced CDH model, which is accompanied by reduced alveolar ADRP expression and lipid content.

METHODS

On embryonic day 9.5 (E9.5), time-mated rats received either nitrofen or vehicle. Fetuses were sacrificed on selected time points E18.5 and E21.5, and dissected lungs were divided into controls and CDH-associated PH. Pulmonary gene expression levels of ADRP were determined by quantitative real-time polymerase chain reaction. ADRP immunohistochemistry and oil red O staining were used to assess pulmonary protein expression and lipid content. Immunofluorescence double staining for alpha smooth muscle actin, which is known to be absent in LIFs, and lipid droplets was performed to evaluate the pulmonary expression of this specific subset of fibroblasts.

RESULTS

Relative mRNA expression of ADRP was significantly reduced in lungs of CDH-associated PH on E18.5 and E21.5 compared to controls. ADRP immunoreactivity and lipid staining were markedly diminished in alveolar mesenchymal cells of CDH-associated PH on E18.5 and E21.5 compared to controls. Confocal laser scanning microscopy demonstrated markedly decreased LIF expression in alveolar interstitium of CDH-associated PH on E18.5 and E21.5 compared to controls.

CONCLUSION

Decreased pulmonary LIF expression during late gestation suggests impaired LIF functioning in the nitrofen-induced CDH model, which may cause disruption in fetal alveolarization and lipid homeostasis, and thus contribute to the development of PH.

Disturbance of parathyroid hormone-related protein signaling in the nitrofen-induced hypoplastic lung

PURPOSE

Despite remarkable progress in resuscitation and intensive care, the morbidity and mortality rates in congenital diaphragmatic hernia (CDH) remain high due to severe pulmonary hypoplasia. The pathogenesis of pulmonary hypoplasia associated with CDH is still not clearly understood. Pulmonary parathyroid hormone-related protein (PTHrP) is expressed in the type II epithelial cells and stimulates surfactant production by a paracrine feedback loop regulated by PTHrP receptor (PTHrP-R), which is expressed in the mesenchyme, during terminal airway differentiation. It has been reported that PTHrP knockout and PTHrP-R null mice both exhibit pulmonary hypoplasia, disrupting alveolar maturation before birth. We designed this study to test the hypothesis that gene expression of PTHrP and PTHrP-R is downregulated in the late stages of lung morphogenesis in the nitrofen-induced hypoplastic lung.

METHODS

Pregnant rats were exposed to either olive oil or nitrofen on day 9 of gestation (D9). Fetal lungs were harvested on D15, 18, and 21 and divided into three groups: control, nitrofen without CDH [CDH(-)], and nitrofen with CDH [CDH(+)] (n = 8 at each time point for each group, respectively). Total mRNA was extracted from fetal lungs and mRNA expression of PTHrP and PTHrP-R was analyzed by real-time RT-PCR and the significant differences between the groups were accepted at P < 0.05 by statistical analysis. Immunohistochemical studies were also performed to evaluate PTHrP and PTHrP-R protein expression at each time point.

RESULTS

Pulmonary mRNA expression of PTHrP-R was significantly decreased in both nitrofen groups [CDH(-) and CDH(+)] compared to controls at D18 and 21. The mRNA level of PTHrP was significantly decreased at D21 in both nitrofen groups compared to controls. Immunoreactivity of PTHrP and PTHrP-R at D18 and 21 was diminished in the distal epithelium and in the mesenchyme, respectively, in the nitrofen-induced hypoplastic lung compared to control lungs. There were no significant differences in both gene/protein expression of PTHrP and PTHrP-R on D15.

CONCLUSION

Downregulation of PTHrP and PTHrP-R gene expression during late lung morphogenesis may cause pulmonary hypoplasia in the nitrofen CDH model, disrupting alveolar maturation and surfactant production by interfering with mesenchymal-epithelial interactions.

Decreased surfactant phosphatidylcholine synthesis in neonates with congenital diaphragmatic hernia during extracorporeal membrane oxygenation

Purpose

Congenital diaphragmatic hernia (CDH) may result in severe respiratory insufficiency with a high morbidity. The role of a disturbed surfactant metabolism in the pathogenesis of CDH is unclear. We therefore studied endogenous surfactant metabolism in the most severe CDH patients who required extracorporeal membrane oxygenation (ECMO).

Methods

Eleven neonates with CDH who required ECMO and ten ventilated neonates without significant lung disease received a 24-h infusion of the stable isotope [U-¹³C] glucose. The ¹³C-incorporation into palmitic acid in surfactant phosphatidylcholine (PC) isolated from serial tracheal aspirates was measured. Mean PC concentration in epithelial lining fluid (ELF) was measured during the first 4 days of the study.

Results

Fractional surfactant PC synthesis was decreased in CDH-ECMO patients compared to controls (2.4 ± 0.33 vs. 8.0 ± 2.4%/day, p = 0.04). The control group had a higher maximal enrichment (0.18 ± 0.03 vs. 0.09 ± 0.02 APE, p = 0.04) and reached this maximal enrichment earlier (46.7 ± 3.0 vs. 69.4 ± 6.6 h, p = 0.004) compared to the CDH-ECMO group, which reflects higher and faster precursor incorporation in the control group. Surfactant PC concentration in ELF was similar in both groups.

Conclusion

These results show that CDH patients who require ECMO have a decreased surfactant PC synthesis, which may be part of the pathogenesis of severe pulmonary insufficiency and has a negative impact on weaning from ECMO.

Effects of antioxidant vitamins on molecular regulators involved in lung hypoplasia induced by nitrofen

INTRODUCTION

Oxidant herbicide nitrofen (2,4-dichloro-4'-nitrodiphenyl ether) induces in rat embryos congenital diaphragmatic hernia (CDH) with lung hypoplasia. The present study aims at examining whether antioxidant vitamins A, E, and C reverse the effects of the teratogen in the lungs of exposed rats and how they modify the expression of molecular regulators known to be involved in their pathogenesis.

MATERIALS AND METHODS

Wet lung weight-body weight ratio, total DNA, and total protein were determined. Thyroid transcription factor 1 (TTF-1), hepatocyte nuclear factor 3beta (HNF-3beta), and surfactant protein B (SP-B) proteins were measured by immunoblot assay in lung homogenates from rat fetuses exposed in utero to either nitrofen 100 mg intragastrically or vehicle. The coexpression of these factors in the alveolar epithelium was demonstrated by immunohistochemistry. The effects of the addition of vitamins A, C, and E were assessed by comparison with analysis of variance.

RESULTS

Nitrofen decreased lung weight, total DNA, and total protein. The addition of antioxidant vitamins had no effect on lung weight, but increased DNA and protein contents. TTF-1, HNF-3beta, and SP-B proteins were decreased in lung homogenates of exposed rats with CDH. The addition of antioxidant vitamins nearly normalized these values.

CONCLUSIONS

The effects of nitrofen in fetal rat lungs are reversed in part by antioxidant vitamins by upregulating the expression of TTF-1, HNF-3beta, and SP-B. This approach could help to develop transplacental prenatal interventions for CDH.

Surfactant metabolism in the neonate

With the use of stable isotope-labeled intravenous precursors for surfactant phosphatidylcholine (PC) synthesis, it has been shown that the de novo synthesis rates in preterm infants with respiratory distress syndrome (RDS) are very low as are turnover rates. This is consistent with animal data. Surfactant therapy does not inhibit endogenous surfactant synthesis, and prenatal corticosteroids stimulate it. With the use of stable isotope-labeled PC given endotracheally, surfactant pool size was estimated. It turned out to be low in RDS, as expected. Similar studies were performed in term neonates with severe lung diseases. In general, patients with lung injury show a lower surfactant synthesis. The controversy around surfactant in congenital diaphragmatic hernia (CDH) persists: studies on CDH with and without extracorporeal membrane oxygenation yielded different results. In severe meconium aspiration syndrome surfactant synthesis was found to be decreased but surfactant pool size was maintained. It is possible and safe to study surfactant metabolism in human neonates with the use of stable isotopes. This can help in answering clinical questions and has the potential to bring new in vitro and animal findings about surfactant metabolism to the patient.

Fetal lung and diaphragm development in congenital diaphragmatic hernia

Congenital Diaphragmatic Hernia (CDH) is a congenital disorder with an incidence of 1 in 2500 live births. Respiratory distress of newborns with CDH is the result of pulmonary hypoplasia and pulmonary hypertension. Hypoplastic lungs are characterized by a decreased number of airways with smaller airspaces, whereas the combination of a decreased number of vascular branches and an increased adventitia and medial thickness of the pulmonary arterial walls result in pulmonary hypertension. The appearance of the CDH lungs suggests that its complete formation is stalled during development. Understanding the basic mechanisms of lung development is mandatory to unravel the origin of CDH. Although the histological abnormalities in CDH lungs have been well described, less is known about the underlying molecular mechanisms. In this review we will discuss the current molecular and genetic background of lung formation, as well as a reflection of this knowledge towards CDH.

A dual stable isotope tracer method for the measurement of surfactant disaturated-phosphatidylcholine net synthesis in infants with congenital diaphragmatic hernia

The aim of the study was to measure for the first time in humans surfactant disaturated-phosphatidylcholine (DSPC) net synthesis and kinetics by using a novel, dual stable isotope tracer approach. Ten infants with congenital diaphragmatic hernia [CDH; birth weight, 3.4 +/- 0.2; gestational age, 39.8 +/- 0.4 wk] and 6 age-matched control subjects with no lung disease (birth weight, 3.2 +/- 0.3 kg; gestational age, 39.1 +/- 1.1 wk), all of whom were admitted to the neonatal intensive care unit (Padua, Italy), were studied. All infants received simultaneously an intratracheal (carbon-13 di-palmitoyl-phosphatidylcholine) and an i.v. (deuterated palmitic acid) stable isotope tracer. Isotopic enrichment curves of DSPC from sequential tracheal aspirates were analyzed by mass spectrometry. DSPC kinetic data were expressed as mean +/- SEM and compared by the Mann-Whitney test. DSPC net synthesis from plasma palmitate was nearly identical in infants with CDH and control subjects (8.6 +/- 2.2 and 8.1 +/- 1.5 mg. kg(-1). d(-1); P = 0.7). DSPC apparent pool size was 36.7 +/- 7.5 and 58.5 +/- 9.1 mg/kg (P = 0.07) and half-life was 26.7 +/- 4.5 and 50.3 +/- 9.7 h (P = 0.03) in infants with CDH and control subjects, respectively. Both DSPC turnover and percentage of catabolism/recycling significantly correlated with duration of mechanical ventilation. In conclusion, the measurements of net DSPC synthesis and catabolism/recycling were reported for the first time in humans. Mean net DSPC synthesis was approximately 8 mg. kg(-1). d(-1). No significant differences were found between control subjects and infants with CDH. DSPC turnover was faster in infants with CDH, presumably reflecting an increased DSPC catabolism/recycling. Whether this may ultimately lead to a secondary surfactant deficiency in infants with CDH is still to be ascertained.

Effect of epidermal growth factor on pulmonary hypoplasia in experimental diaphragmatic hernia

BACKGROUND/PURPOSE

Currently, tracheal occlusion (TO) is a potent stimulus for fetal lung growth but also a rather invasive and high-risk procedure. The aim of this study was to investigate a new and much less invasive therapeutic strategy, namely the maternal intraperitoneal administration of epidermal growth factor (EGF) and its effect on pulmonary hypoplasia in the nitrofen-induced congenital diaphragmatic hernia (CDH) rat model, especially its effect on type II pneumocytes.

METHODS

CDH was induced by maternal administration of a single oral dose (100 mg) of nitrofen on day 8.5 of pregnancy. Four groups of pregnant rats were designed on day 18.5: normal control (n = 4), CDH (n = 4), CDH plus Dex (n = 4), CDH plus EGF (n = 8). All fetuses were delivered by cesarean section on day 21. Accordingly, there were 4 groups of fetuses: normal controls (n = 33), nitrofen-induced CDH (n = 19), CDH plus Dex treatment (n = 15), and CDH plus EGF treatment (n = 24). Lung tissue weight (LW) and body weight (BW) of each fetus were recorded, lung histologic and morphometric evaluations were performed, and image analysis was combined after lung processing. Transmission electron microscopy was used for ultrastructural observation, especially type II pneumocytes.

RESULTS

CDH was observed in 58 of the 94 rat fetuses (61.7%). Lw/Bw of CDH group was significantly lower than those of Dex and EGF (P <.05). The lungs of CDH fetuses showed marked hypoplasia, in contrast to improved mesenchymal differentiation in that of Dex and EGF fetuses. Statistical differences of these morphologic parameters (RAC, MTBD, interstitial%, and alveoli%) were found (P <.05). As to ultrastructural features, type II cells of CDH lungs had few if any lamellar bodies and cytoplasmic organelles, and showed evidence of abundant glycogen granules. The sparse type II cells also showed cytoplasmic degenerative changes. By contrast, type II cells of EGF lungs showed numerous mitochondria, abundant lamellar bodies (surfactant) and deficiency of glycogen granules, and displayed prominent microvillous projections and pitlike depressions. The density of type II pneumocyte were 65 +/- 4.5, 31 +/- 3.1, and 8 +/- 1.5 for EGF, Dex, and CDH, respectively (EGF v Dex, P <.05; EGF v CDH, P < 0.01).

CONCLUSIONS

Compared with TO, prenatal EGF administration as a much less-invasive therapeutic strategy had shown marked improvement in pulmonary hypoplasia and promotion of type II pneumocyte differentiation in the nitrofen-induced CDH rat model. Thus, EGF could improve the prognosis of CDH by means of promoting pulmonary hypoplasia and improving the surfactant deficiency, which suggested a potential role in the clinical treatment of CDH.

Pulmonary surfactant protein A, B, and C mRNA and protein expression in the nitrofen-induced congenital diaphragmatic hernia rat model

Neonates with congenital diaphragmatic hernia (CDH) suffer from a diaphragmatic defect, lung hypoplasia, and pulmonary hypertension, with poor lung function forming the major clinical challenge. Despite prenatal diagnosis and advanced postnatal treatment strategies, the mortality rate of CDH is still high. CDH has been subject of extensive research over the past decades, but its etiology remains unknown. A major problem with CDH is the failure to predict the individual response to treatment modalities like high-frequency ventilation, inhaled nitric oxide, and extracorporeal membrane oxygenation. In this study, we tested the possibility that CDH lungs are surfactant protein deficient, which could explain the respiratory failure and difficulties in treating CDH infants. We investigated this hypothesis in the nitrofen-induced CDH rat model and assessed the cellular concentrations of surfactant protein (SP)-A, -B, and -C mRNA with a quantitative radioactive in situ hybridization technique. No differences were observed between control and CDH lungs for SP mRNA expression patterns. The cellular concentration (mean OD) of SP-A and SP-B mRNA was similar at all stages whereas the mean OD of SP-C mRNA and the volume fraction of cells (% Area) expressing SP mRNA was higher in CDH lungs at term. Immunohistochemical analysis revealed no differences between control and CDH lungs for SP protein expression. No differences in the mean OD or % Area for the SP mRNAs were found between the ipsi- and contralateral side of CDH lungs. We conclude that there is no primary deficiency of surfactant proteins in the nitrofen-induced CDH rat model.

Pulmonary surfactant disaturated-phosphatidylcholine (DSPC) turnover and pool size in newborn infants with congenital diaphragmatic hernia (CDH)

In animal CDH models, surfactant deficiency contributes to the pathophysiology of the condition but information on human disease is very limited. The aim of our study was to investigate surfactant kinetics in CDH newborns. We studied surfactant disaturated-phosphatidylcholine (DSPC) half-life, turnover and apparent pool size by stable isotope methodology in CDH newborns with no ExtraCorporeal Membrane Oxygenation (ECMO) support (n = 13, birth weight (BW) 3.2 +/- 2.2 kg, gestational age (GA) 39 +/- 0.4 wks, postnatal age 43 +/- 11 h) and in 8 term infants with no lung disease (CONTROLS, BW 2.7 +/- 0 kg, GA 38 +/- 0.8 wks, postnatal age 96 +/- 26 h). We administered a trace dose of 13C-palmitic acid dipalmitoyl-phosphatidylcholine (DPPC) through the endotracheal (ET) tube and we measured DSPC kinetics by gas chromatography-mass spectrometry from DSPC13C-enrichment decay curves obtained from sequential tracheal aspirates. DSPC amount from tracheal aspirates (TA-DSPC) was measured by gas chromatography. In CDH infants DSPC half-life was shorter (24 +/- 4 and 53 +/- 11 h, p = 0.01), turnover faster (0.6 +/- 0.1 and 1.5 +/- 0.3 d-1 p = 0.01), apparent pool size smaller (34 +/- 6 and 57 +/- 7 mg/kg body weight, p = 0.02) and tracheal aspirates DSPC amount lower (2.4 +/- 0.4 and 4.6 +/- 0.5 mg/mL Epithelial Lining Fluid (ELF), p = 0.007) than in CONTROLS. In conclusion surfactant kinetics is grossly abnormal in mechanically ventilated CDH. Whether alterations of DSPC kinetics in CDH infants are caused by a primary surfactant deficiency or are secondary to oxygen therapy and ventilator support has still to be determined.

Surfactant phosphatidylcholine pool size in human neonates with congenital diaphragmatic hernia requiring ECMO

OBJECTIVE

We measured surfactant phosphatidylcholine (PC) pool size and half-life in human congenital diaphragmatic hernia (CDH) patients who required extracorporeal membrane oxygenation (ECMO). Study design Surfactant PC pool size and half-life were measured by endotracheal administration of deuterium-labeled dipalmitoylphosphatidylcholine in 8 neonates with CDH on ECMO (CDH-ECMO), in 7 neonates with meconium aspiration syndrome on ECMO (MAS-ECMO), and in 6 ventilated infants (NON-ECMO).

RESULTS

Lung PC pool size in the CDH-ECMO group was 73 +/- 17 mg/kg (mean +/- SEM), which was not significantly different from the MAS-ECMO (50 +/- 18 mg/kg) and the NON-ECMO group (69 +/- 38 mg/kg). Surfactant PC concentration in tracheal aspirates was not different between groups (~6 mg/mL). However, the percentage of palmitic acid in surfactant PC was significantly lower in the MAS-ECMO (56.3%) and the NON-ECMO (55.8%) group compared with the CDH-ECMO (67.6%) group. Surfactant PC half-life (~24 hours) was not different between the groups. A correlation was found between the surfactant PC half-life and the duration of ECMO.

CONCLUSIONS

These data show no decreased surfactant PC pool size in high risk CDH patients who require ECMO. A shorter half-life of surfactant PC, indicating a faster turnover, may result in a faster improvement of the pulmonary condition during ECMO.