Luc J I Zimmermann

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−1p = 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.

Compound SFTPB 1549C→GAA (121ins2) and 457delC heterozygosity in severe congenital lung disease and surfactant protein B (SP-B) deficiency

Several human respiratory disorders have been linked to an abnormality of pulmonary surfactant synthesis or turnover. Among those conditions, hereditary deficiency in the hydrophobic surfactant protein B (SP‐B) has been recognized as a rare cause of respiratory failure in term newborn infants. Homozygosity for a common mutation (1549C→GAA, or 121ins2) of the SP‐B‐encoding gene (SFTPB) results in rapidly fatal respiratory failure, with complete absence of the mRNA and protein observed in lung fluid or biopsy specimens. Hereditary SP‐B deficiency is also associated with aberrant processing of proSP‐C and deficiency of the active SP‐C peptide. In the present study, we characterized the SFTPB gene in an infant with severe unexplained respiratory distress and identified a paternally derived 1549C→GAA lesion, as well as a hitherto unreported mutation (457delC) inherited from the mother. Analysis of bronchoalveolar lavage fluid demonstrated the complete absence of SP‐B. However, unlike previous infants with hereditary SP‐B deficiency, proSP‐C was processed to the active SP‐C peptide, suggesting that the defect in SP‐B, rather than SP‐C, caused the respiratory distress in this infant. The present findings demonstrate the importance of SFTPB in pulmonary function and support the need for further genotype–phenotype correlations in patients with SP‐B deficiency. Hum Mutat 14:502–509, 1999.

Surfactant kinetics in preterm infants on mechanical ventilation who did and did not develop bronchopulmonary dysplasia

ObjectiveTo characterize surfactant kinetics in vivo in two groups of premature infants on different levels of mechanical ventilation and at different risk of developing bronchopulmonary dysplasia. DesignControlled observational study in two independent groups of infants. SettingNeonatal intensive care unit. PatientsThirteen preterm infants (26 ± 0.5 wks, birth weight 801 ± 64 g) on high ventilatory setting and who finally all developed bronchopulmonary dysplasia (MechVentBPD), and eight (26 ± 0.5 wks, birth weight 887 ± 103 g) who had minimal or no lung disease and of whom none developed bronchopulmonary dysplasia (MechVentNoBPD). Measurements and Main ResultsEndotracheal 13C-labeled dipalmitoyl-phosphatidylcholine was administered and subsequent measurements of the 13C enrichment of surfactant-disaturated phosphatidylcholine (DSPC) from serial tracheal aspirates were made by gas chromatography-mass spectrometry. We calculated disaturated phosphatidylcholine pharmacokinetic variables in terms of half-life and apparent pool size from the enrichment decay curves over time. DSPC concentration from tracheal aspirates was expressed as milligrams/milliliter epithelial lining fluid (ELF-DSPC). Data are presented as mean ± se. In MechVentBPD infants vs. MechVentNoBPD, ELF-DSPC was much reduced, 2.9 ± 0.6 vs. 9.4 ± 3.0 mg/mL ELF (p = .03), half-life was shorter, 19.4 ± 2.8 vs. 42.5 ± 6.3 hrs (p = .002), and apparent pool size larger, 136 ± 21 vs. 65.8 ± 16.0 mg/kg (p = .057). In MechVentBPD, apparent DSPC pool size positively correlated with mean airway pressure × Fio2 and inversely correlated with ELF-DSPC. ELF-DSPC was inversely correlated with mean airway pressure × Fio2. No significant correlations were found in the MechVentNoBPD group. ConclusionsMechVentBPD infants showed profound alteration of surfactant kinetics compared with preterm infants with minimal lung disease, and these alterations were correlated with severity of ventilatory support.

Surfactant Phosphatidylcholine Half-life and Pool Size Measurements in Premature Baboons Developing Bronchopulmonary Dysplasia

Because minimal information is available about surfactant metabolism in bronchopulmonary dysplasia, we measured half-lives and pool sizes of surfactant phosphatidylcholine in very preterm baboons recovering from respiratory distress syndrome and developing bronchopulmonary dysplasia, using stable isotopes, radioactive isotopes, and direct pool size measurements. Eight ventilated premature baboons received 2H-DPPC (dipalmitoyl phosphatidylcholine) on d 5 of life, and radioactive 14C-DPPC with a treatment dose of surfactant on d 8. After 14 d, lung pool sizes of saturated phosphatidylcholine were measured. Half-life of 2H-DPPC (d 5) in tracheal aspirates was 28 ± 4 h (mean ± SEM). Half-life of radioactive DPPC (d 8) was 35 ± 4 h. Saturated phosphatidylcholine pool size measured with stable isotopes on d 5 was 129 ± 14 μmol/kg, and 123 ± 11 μmol/kg on d 14 at autopsy. Half-lives were comparable to those obtained at d 0 and d 6 in our previous baboon studies. We conclude that surfactant metabolism does not change during the early development of bronchopulmonary dysplasia, more specifically, the metabolism of exogenous surfactant on d 8 is similar to that on the day of birth. Surfactant pool size is low at birth, increases after surfactant therapy, and is kept constant during the first 2 wk of life by endogenous surfactant synthesis. Measurements with stable isotopes are comparable to measurements with radioactive tracers and measurements at autopsy.

Simultaneous Measurement of the Rates of Appearance of Palmitic and Linoleic Acid in Critically Ill Infants

Lipolysis has been measured in humans by means of stable isotope techniques using labeled palmitic acid (PA) or glycerol as tracers. If other fatty acids(FA) such as linoleic acid (LLA) have the same rate of appearance(Ra) as PA and therefore contribute equally to oxidative and nonoxidative metabolism is unknown. We infused albumin-bound [U-13C]PA and [U-13C]LLA in seven critically ill infants (weight 3.6 ± 1.3 kg, age 57 ± 64 d) receiving 20.9 ± 5.4 kcal· kg-1·d-1 of i.v. glucose only, and measured simultaneously the Ra of PA and LLA from the isotopic enrichment of plasma FFA by mass spectrometry. A needle biopsy of the s.c. adipose tissue was obtained for FA composition. PA in adipose tissue was higher than LLA (40 ± 6.7 versus 5.4 ± 3.2 mol%,p < 0.001). The Ra values of PA and LLA were 5.73 ± 2.79 and 1.34 ± 0.92μmol·kg-1·min-1, respectively (p = 0.005). However, the ratio of the FAs Ra to their respective mol% values in adipose tissue was lower for PA than for LLA (0.15 ± 0.06 versus 0.25 ± 0.06, p = 0.02). TheRa of LLA acid was higher than could be expected from the FA composition of adipose tissue, thus indicating a preferential release of LLA during lipolysis. In critically ill infants receiving only i.v. glucose, the contribution of LLA to the oxidative and nonoxidative metabolism may be larger than what assumed from the FA composition of plasma and adipose tissue.

Pulse oximetry screening for critical congenital heart defects: a European consensus statement

Critical congenital heart defects (CCHD) are life-threatening and timely detection is essential for optimal outcome. Experts in CCHD screening and representatives from major European paediatric and neonatal societies convened to develop suitable and implementable evidencebased recommendations on pulse oximetry screening (POS) for CCHD across Europe. POS has been shown to be a simple, quick and painless tool for identifying babies with CCHD which is inexpensive, acceptable and has a high specificity and moderate sensitivity. POS should be performed in two extremities (right hand and either foot) using new generation, motion tolerant equipment after 6 hours of life or before discharge (preferably before 24 hours of life). Several screening protocols are available and current data does not differentiate a ‘best’ protocol; thus, countries may decide upon which protocol best fits their population. Adopting POS at a national level across Europe will help improve management of these lifethreatening conditions.

275 Epithelial Repair in The Preterm Lung is Decreased in The Early Phase of Bronchopulmonary Dysplasia

Background: In the early phases bronchopulmonary dysplasia (BPD) is characterized by epithelial and endothelial damage and inflammation. A recent study showed an absent or decreased concentration of keratinocyte growth factor, a factor contributing to epithelial repair, in early BPD (Danan C et al, Am J Respir Crit Care Med. 2002;165:1384–7).Aim: To investigate whether bronchoalveolar lavage fluid (BALF) from preterm infants who develop BPD has a decreased capacity to stimulate epithelial repair compared to BALF from infants who recover from respiratory distress syndrome (RDS).Methods: A standardized blind bronchoalveolar lavage was performed with 2x1 ml/kg saline in ventilated preterm infants with a gestational age <30 weeks on day 2 to 4 of life. Infants who recovered from RDS were all extubated within the first week of life. BPD was defined as oxygen requirement at 28 days of life. A bronchial epithelial cell line (BEAS) was grown to confluence and a scratch of known surface area was made in the epithelium (Geiser et al, Am J Physiol Lung Cell Mol Physiol 2000;279:L1184–90). BALF (or control medium without serum) was added to the cell cultures for 18 hours and the closure of the epithelial wound was assessed (expressed as % closure above control medium).Results: BALF from infants who developed BPD (n=13) had a significantly lower capacity to stimulate epithelial wound closure than BALF from infants who recovered from RDS (n=10): 25±5% versus 48±4.5% closure above control medium (p=0.02 by t-test) (mean±SEM).Conclusion: BALF on day 2 to 4 from preterm infants who develop BPD has a decreased capacity to stimulate epithelial repair in an in vitro assay compared to BALF from infants who recover from RDS. This suggests that besides epithelial injury also decreased epithelial repair plays a role in the early phase of BPD development. Further investigations are necessary to elucidate which growth factors or other factors are important for the decreased epithelial repair in the early phase of BPD development.