The role of lung inflation and sodium transport in airway liquid clearance during lung aeration in newborn rabbits

Pediatr Res. 2013 Apr;73(4 Pt 1):443-9. doi: 10.1038/pr.2012.197. Epub 2012 Dec 26.

Abstract

Background: Recent phase-contrast X-ray imaging studies suggest that inspiration primarily drives lung aeration and airway liquid clearance at birth, which questions the role of adrenaline-induced activation of epithelial sodium channels (ENaCs). We hypothesized that pressures generated by inspiration have a greater role in airway liquid clearance than do ENaCs after birth.

Methods: Rabbit pups (30 d of gestation) were delivered and sedated, and 0.1 ml of saline (S) or amiloride (Am; an ENaC inhibitor) was instilled into the lungs before mechanical ventilation. Two other groups (30 d of gestation) were treated similarly but were also given adrenaline (S/Ad and Am/Ad) before mechanical ventilation.

Results: Amiloride and adrenaline did not affect functional residual capacity (FRC) recruitment (P > 0.05). Amiloride increased the rate of FRC loss between inflations (Am: -5.2 ± 0.6 ml/kg/s), whereas adrenaline reduced the rate of FRC loss (S/Ad: -1.9 ± 0.3 ml/kg/s) as compared with saline-treated controls (S: -3.5 ± -0.6 ml/kg/s; P < 0.05).

Conclusion: These data indicate that inspiration is a major determinant of airway liquid clearance and FRC development during positive pressure ventilation. Although ENaC inhibition and adrenaline administration had no detectable effect on FRC development, ENaC may help to prevent liquid from re-entering the airways during expiration.

Publication types

  • Research Support, Non-U.S. Gov't
  • Video-Audio Media

MeSH terms

  • Amiloride / administration & dosage
  • Animals
  • Animals, Newborn
  • Epinephrine / administration & dosage
  • Epithelial Sodium Channel Blockers / administration & dosage
  • Epithelial Sodium Channels / drug effects
  • Epithelial Sodium Channels / metabolism*
  • Functional Residual Capacity
  • Gestational Age
  • Hydrostatic Pressure
  • Inhalation*
  • Lung / diagnostic imaging
  • Lung / drug effects
  • Lung / metabolism*
  • Lung Volume Measurements
  • Mucociliary Clearance*
  • Plethysmography
  • Rabbits
  • Radiography
  • Respiration, Artificial*
  • Respiratory Mucosa / drug effects
  • Respiratory Mucosa / metabolism*
  • Sodium / metabolism*
  • Sodium Chloride / administration & dosage
  • Time Factors

Substances

  • Epithelial Sodium Channel Blockers
  • Epithelial Sodium Channels
  • Sodium Chloride
  • Amiloride
  • Sodium
  • Epinephrine