Cardiorespiratory Changes After Birth

Dr. Harold Helbock

Generic Heart

The Cardiac Tube

The Adult Heart

Cardiac Outflow Anomalies

Abnormal conditions compatible with fetal life are often

Incompatible, or incapacitating to some degree, with postnatal life, including the adult.

Chief among the hazards induced by cardiac anomalies is the distribution of inadequately

oxygenated blood to the body.

Examples of Cardiac Anomalies

Tetralogy of Fallot• Stenosis of

pulmonary artery• Displacement of

aortic opening to the right.

• Intraventricular opening

• Hypertrophy of right ventricle.

Patent Ductus Arteriosus

• Blood regurgitates from the aorta to the pulmonary artery and is taken back to the lungs.

Examples of Cardiac Anomalies

Heart Rate in Labor

Characteristics of the Adult Pulmonary Respiratory System

Functions of the Lungs

• Gas Exchange

Oxygen absorption

Carbon Dioxide removal

• Immunologic Defense• Metabolic Function• Endocrine Function• Peptide Activators

Pulmonary capillary

• The newborn must switch rapidly from intrauterine mechanisms to adult physiology.

• This process is referred to as transition and involves changes in both pulmonary and circulatory physiology.

Transition Period from Prenatal To Postnatal Life

Normal Transition

of Circulation from Pre- to Post- natal

closed

open

expand

closed

Differences in oxygenation system of the fetus to the

newbornBronchi/airways uterine artery

Air sacks/alveoli placental sinusoids

Pulmonary vein umbilical vein

Oxygenated blood to the heart

Pulmonary artery umbilical artery

Venous blood to gas exchange organ

Diaphragm maternal myocardium

Move the gas to be exchanged

Events Happening at Birth

• First breath30-100 mm Hg vs. 5-10 mm Hg for

normal breathing• Closure of ductus arteriosus

Functional and later anatomic closure

Initially systemic and pulmonary pressures are equal

• Removal of fluid from the lungs

Protein molecules

Chloride

Major steps described in next slide

Removal of Lung Fluid at Birth1. Fetus = Cl- pumps move fluid into potential air space.

2. Very little protein in potential air space liquid.

3. Result = osmotic pressure draws liquid from the alveolar space to the interstitium = circulation.

4. Newborn = Cl- pumping stops and Na+ pump moves fluid out of alveoli.

5. Air pressure in the alveoli drives liquid out and into interstitium.

6. Expansion of the lung stretches open the pulmonary vessels and thereby reducing pulmonary vessel pressure and hydrostatic pressure.

7. Net result = liquid leaves air spaces and exits the interstitial space via the lymph and microcirculation.

The Apgar ScoreAssessment of transition

Score 0 1 2Heart rate

Respiratory effort

Muscle tone

Reflex irritability

Color

Absent

Absent

Limp

Absent

Blue, pale

Less than 100/min

Slow, irregular

Some flexion of extremities

Grimace

Body pink/extremities blue (acrocyanosis)

More than 100/min

Good, crying

Active motion

Grimace and cough or sneeze

Completely pink

The First

Hours of Life

The First Week of Life• The infant is given vitamin K.

– Eye drops are instilled to prevent blindness from bacterial infection.

– Hepatitis B (a major cause of hepatic cancer) immunization.

• Feedings– Infant slowly increased volume of milk taken at each

feeding until intake is about 1 fluid oz. per hour, on average.

– Parents get a little more sleep, but not much!!

• Jaundice is a common problem on days 2-4 and longer if blood group incompatibilities exist.– Principle: post birth adaptation must take place in

multiple systems, not just lungs and heart

• A good baby is a sick baby!• BW ~ IQ and 1/CV disease risk, mom’s diet

The First Week of Life