- (1) loss of umbilical circulation to placenta
- (2) closure of ductus venosus
- (3) closure of the foramen ovale
- (4) closure of ductus arteriosus
- (5) large increase in pulmonary circulation
- (6) increase in RBF from decrease renal vascular resistance
- (7) changes in skin blood flow
- (1) loss of placental gas exchange
- (2) initiation of ventilation of the newborns lung
- (3) commencement of pulmonary gas exchange
- (4) establishment of FRC
1. First breath -> lungs expand -> pulmonary blood flow increases markedly -> drop in PVR -> bolus of blood to LA + LV -> reversing pressure & closure of foramen ovale.
2. Loss of umbilical circulation (clamping cord) -> increased SVR
3. Closure of ductus venosus
4. Closure of ductus arteriosus
- functional not anatomical due to increased exposure to increased PO2, pH and decreased PCO2 -> inhibiton of prostaglandins E1 & E2 -> vasoconstriction
5. Large increase in pulmonary circulation.
- inflation of lungs drawing blood into thorax
- prostaglandin & NO action
6. Changes in skin blood flow from exposure.
7. Decrease renal vascular resistance -> increase in RBF & GFR.
8. Increased FiO2 shifting oxy-Hb curve to to right -> less fetal Hb & increased 2,3 DPG.
- passage through birth canal compresses the babies chest wall -> expels foetal fluid
- also reabsorbed (lung lymphatics) and replaced with air
- high negative intrathoracic pressure (-50cmH2O) -> breathing comes easier c/o sufactant & establishment of air-liquid interface.
- @ 10min FRC = 20mL/kg
- @ 60min FRC = 30mL/kg
- neonatal alveolar ventilation 120 to 140mL/kg/min (double adults) -> achieved through an increase in RR