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Summary
Pulmonary fluid (PF) volume is crucial for fetal lung opening pressure (OP). Reduced PF in postmature lungs increases OP, while labor-induced surfactant release aids lung expansion.
Area of Science:
- Neonatal physiology
- Respiratory mechanics
- Fetal development
Background:
- Pulmonary fluid (PF) volume decreases in late gestation and labor.
- Surfactant is massively released into PF during labor.
- PF volume reduction continues in postmaturity, leading to fluid-free lungs and loss of surface activity.
Purpose of the Study:
- To investigate the role of PF volume and surface activity on fetal lung opening pressure (OP).
Main Methods:
- Fetal (term and post-term) and newborn lungs were inflated with air to record OP.
- Pulmonary fluid volume was manipulated by instilling saline into post-term lungs.
Main Results:
- Lowest OP was observed in term fetuses delivered after labor.
- Increased lung dryness (post-term, postnatal) correlated with increased OP.
- Restoring PF volume in post-term lungs decreased OP, while excessive fluid increased it.
- Fetal lungs showed a more acute OP-volume curve deflection than adult lungs.
Conclusions:
- A reduction in PF volume at birth beyond that of a term fetus may be detrimental to newborns.
- Massive surfactant release in PF during labor enhances air saccules opening.