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Updated: Oct 9, 2026
Surfactant Depletion Combined with Injurious Ventilation Results in a Reproducible Model of the Acute Respiratory Distress Syndrome (ARDS)
Published on: April 7, 2021
Endogenous surfactant turnover in preterm infants with respiratory distress syndrome studied with stable isotope
P Cavicchioli1, L J Zimmermann, P E Cogo
1Department of Pediatrics, University of Padua, Padua, Italy.
Insights
This study measured surfactant kinetics in preterm infants using stable isotope-labeled lipids, finding different synthesis rates and half-lives for palmitic and linoleic acids. Exogenous surfactant treatment affected secretion timing but not overall kinetics.
Area of Science:
- Neonatology
- Biochemistry
- Respiratory Physiology
Background:
- Surfactant deficiency is a primary cause of respiratory distress syndrome (RDS) in preterm infants.
- Understanding surfactant kinetics is crucial for optimizing treatment strategies.
- Previous studies have not fully elucidated the dynamic behavior of surfactant components in vivo.
Purpose of the Study:
- To investigate surfactant kinetics in preterm infants on mechanical ventilation using stable isotope-labeled fatty acids.
- To compare the fractional synthesis rate (FSR) and half-life (HL) of phosphatidylcholine with palmitic acid (PC-PA) and linoleic acid (PC-LLA).
- To assess the impact of exogenous surfactant treatment on surfactant kinetics.
Main Methods:
- Stable isotope-labeled palmitic acid (PA) and linoleic acid (LLA) were infused into 11 preterm infants on Day 1 of life.
- Tracheal aspirates were collected to measure isotopic enrichment in surfactant phosphatidylcholine (PC-PA and PC-LLA) via mass spectrometry.
- Fractional synthesis rate (FSR) and half-life (HL) were calculated for PC-PA and PC-LLA.
Main Results:
- Significant isotopic enrichment of PC-PA and PC-LLA was measurable in all infants.
- The FSR of PC-LLA was significantly higher than that of PC-PA (22.7% vs. 12.1% per day).
- The HL of PC-PA was significantly longer than that of PC-LLA (94.7 h vs. 46.6 h).
- Infants receiving exogenous surfactant showed longer secretion times and delayed peak times, but FSR and HL remained unaffected.
Conclusions:
- Surfactant kinetics can be reliably measured in preterm infants using stable isotope-labeled lipids.
- Palmitic acid and linoleic acid yield different surfactant FSR and HL values, highlighting the complexity of surfactant metabolism.
- Exogenous surfactant treatment influences surfactant secretion dynamics but not the intrinsic synthesis or degradation rates.
- In vivo surfactant FSR derived from plasma free fatty acids is higher than previously reported FSR from plasma glucose in a similar infant population.
Abstract:
We studied surfactant kinetics on Day 1 of life in 11 preterm infants on mechanical ventilation by infusing stable isotope labeled palmitic (PA) and linoleic acid (LLA). Six infants received exogenous surfactant for the treatment of respiratory distress syndrome (RDS) and five did not meet treatment criteria because of minimal or no disease. The isotopic enrichment of plasma free PA and LLA and of surfactant phosphatidylcholine PA (PC-PA) and LLA (PC-LLA) from tracheal aspirates was measured by mass spectrometry. Significant isotopic enrichment could be measured in PC-PA and PC-LLA from all patients. The fractional synthesis rate (FSR) of PC-LLA was higher than that of PC-PA (22.7 +/- 15.9 versus 12.1 +/- 7.7% per day, p = 0.018). Half-life (HL) of PC-PA was longer than that of PC-LLA (94.7 +/- 18.8 versus 46.6 +/- 32.6 h, p = 0.028). Patients who received exogenous surfactant had longer secretion times (ST) and delayed peak times (PK) but FSR and HL were unaffected. We concluded that: (1) surfactant kinetics can be measured in preterm infants with stable isotope labeled lipids; (2) surfactant FSR and HL calculated with PA and LLA gave different results; (3) patients treated with exogenous surfactant had similar FSRs compared with the nontreated subjects but had longer ST and delayed PK; (4) FSR from plasma free fatty acids (present study) was higher than that from plasma glucose in our previous work (Bunt JEH, Zimmermann LJI, Wattimena D, van Beek R, Sauer PJJ, Carnielli VP. Am J Respir Crit Care Med 1998;157:810-814) in a comparable population of preterm infants with RDS.
