Lung fluid absorption is induced in preterm guinea pigs ventilated with low tidal volumes

ABSTRACT

The objective of this study was to determine if low tidal volume (V_t) ventilation was beneficial when ventilating preterm fetuses. The authors ventilated preterm guinea pig fetuses at gestation day (GD) 67, 3 days before birth, newborn, and 10-day-old (PD10) guinea pigs with low V_t (6 mL/kg body weight [bw]) and compared them to age-matched fetuses/animals ventilated with higher potentially injurious V_t (12 mL/kg bw). Lung fluid absorption was measured after intratracheal instillation of 5% albumin in 0.9% NaCl. Low V_t ventilation stimulated lung fluid absorption when compared to higher V_t in all groups. The increased lung fluid absorption in low V_t–ventilated fetuses was associated with increased α epithelial Na channel (αEnaC) mRNA. However, αENaC and βENaC protein was unchanged over the 1-hour study. Because stretch induces mitogen-activated protein (MAP) kinase expression and MAP kinases may affect lung fluid absorption, the authors investigated if MAP kinase (MAPK) expression was affected by V_t. Extracellular signal-regulated kinase (ERK) and MAPK/ERK kinase (MEK) were phosphorylated in the higher V_t–ventilated guinea pig fetuses. This suggested that a reduced activation of MAP kinases might explain the increased lung fluid absorption in the low V_t–ventilated fetuses. Thus these data suggest that low V_t ventilation increases fetal lung fluid absorption and thus may be preferential to use clinically.

KEYWORDS :

• alveolar fluid clearance
• ENaC
• lung fluid absorption
• MAP kinases
• preterm delivery
• ventilation