Physiological Changes At Birth



  • (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

CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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