Physiological Changes At Birth
SUMMARY
Cardiovascular
- (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
Respiratory
- (1) loss of placental gas exchange
- (2) initiation of ventilation of the newborns lung
- (3) commencement of pulmonary gas exchange
- (4) establishment of FRC
CARDIOVASCULAR
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.
RESPIRATORY
- 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
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
| INTENSIVE | RAGE | Resuscitology | SMACC
