24 Questions
What is the cross-sectional shape of an infant's thorax?
Cylindrical
At what age is the adult chest shape achieved?
3 years
What is the orientation of infant ribs compared to adult ribs?
More horizontal
What is the difference in diaphragm insertion between infants and adults?
Infant diaphragms insert horizontally
At what gestation do true alveoli develop?
36 weeks
What is the number of alveoli in a term new-born?
150 million
What is the difference in muscle mass and fiber content between infant and adult diaphragms?
Infant diaphragms have relatively lower muscle mass and lower content of high-endurance muscle fibers
By what gestation can the air-blood barrier support gas exchange?
20-27 weeks
What happens to the de-oxygenated blood that enters the right ventricle in a fetus?
It is shunted away from the lungs and into the aorta
What is the purpose of the ductus venousus in fetal circulation?
To direct de-oxygenated blood from the umbilical cord to the liver
What causes the closure of the foramen ovale after birth?
Decrease in right heart pressure
What is the result of the baby taking their first breath after birth?
The pressure gradient in the heart changes, favoring higher left atrial pressure
What is the role of the placenta in the closure of the ductus arteriosus?
It produces prostaglandins that keep the ductus arteriosus open
What is an example of a congenital heart defect that occurs when the foramen ovale fails to close?
Patent Foramen Ovale
When do lamella bodies, which contribute to the development of surfactant, begin to be seen in utero?
At 20 weeks' gestation
What is the result of a lack of surfactant in pre-term infants?
Infant Respiratory Distress Syndrome (IRDS)
Which of the following is a risk factor for IRDS and mortality?
Male gender
What is the sequence of events leading to atelectasis in IRDS?
Reduced surfactant production → Increased surface tension → Decreased lung compliance → Atelectasis
Why are infants prone to alveolar collapse?
None of the pathways for collateral ventilation are available at birth
What is the definition of barotrauma?
Airway pressure trauma
Why are infants up to 6 months of age preferential nasal breathers?
Their airway is prone to obstruction
What is the function of the ductus venousus in fetal circulation?
Shunts blood from the placenta to the inferior vena cava
What is the purpose of the foramen ovale in fetal circulation?
Shunts blood from the right atrium to the left atrium
How many umbilical arteries are present in the umbilical cord?
Two
Study Notes
Cardiorespiratory Differences Across the Lifespan
- Anatomical and physiological differences between adults and paediatric populations make it impossible to directly transfer adult physiotherapy assessment and interventions to paediatric populations.
Thoracic Cavity
- Infant thorax has a cylindrical cross-sectional shape, whereas adult thorax is elliptical.
- Newborn ribs are softer and more horizontal compared to older children and adults, which affects the 'bucket handle' motion.
- Adult chest shape is achieved by three years of age.
Diaphragm
- Infant diaphragm inserts horizontally, giving them a mechanical disadvantage.
- Infant diaphragm has lower muscle mass and lower content of high-endurance muscle fibers.
Alveoli Development
- Air-blood barrier is thin enough to support gas exchange by 20-27 weeks of gestation.
- True alveoli develop only after 36 weeks' gestation.
- Term newborn has approximately 150 million alveoli, with most developing in the first two years of life.
Surfactant and IRDS
- Lamella bodies, which contribute to surfactant development, are seen in utero at about 20 weeks' gestation.
- Pre-term infants (28-32 weeks' gestation) lack surfactant, making them susceptible to Infant Respiratory Distress Syndrome (IRDS).
- IRDS is a breathing disorder in newborns caused by immature lungs, with male gender being a risk factor.
Collateral Ventilation
- Infants lack pathways for collateral ventilation, predisposing them to alveolar collapse.
- Pores of Kohn develop between 1-2 years, and canals of Lambert appear around 6 years of age.
Airway Anatomy
- Infants have large heads, prominent occiputs, short necks, large tongues, smaller retracted lower jaws, and high larynxes, making their airway prone to obstruction.
- Infants up to 6 months are preferential nasal breathers, and any nasal passage obstruction compromises breathing.
Fetal Circulation
- Fetal circulation is different from adult circulation, with oxygenated blood coming from the mother's placenta through shunts.
- The three shunts are:
- Ductus venousus: shunts blood from the placenta to the inferior vena cava.
- Foramen ovale: shunts blood from the right atrium to the left atrium.
- Ductus arteriosus: shunts blood from the pulmonary artery to the aorta.
- At birth, the ductus venousus disappears, and the foramen ovale and ductus arteriosus close due to changes in pressure and hormones.
Congenital Heart Defects
- Understanding the differences between circulation systems is crucial for understanding congenital heart defects.
- Patent Foramen Ovale is an example of a congenital heart defect, where the foramen ovale shunt does not close after birth.
This quiz explores the anatomical and physiological differences in cardiorespiratory systems between adults and paediatric populations, and their implications for physiotherapy assessment and interventions.
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