Term
By the 16th week of gestation, how far are the lungs developed?
How many alveoli do full term kiddos have? |
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Definition
To the terminal bronchioles
20 million--compared to the 300 million in an adult! |
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Term
| So if kids are born with a decreased number of alveoli, how long does it take for them to develop a full set? What happens to the alveoli as the chest grows? |
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Definition
| The alveoli increase in number till the age of 8. As the chest wall grows, the alveoli get bigger. |
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Term
| As the alveoli grow, what happens to the pulmonary vessles? What about the smooth muscle? |
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Definition
| The number of pulmonary vessels increases, but the smooth muscle lags. Children do not have full smooth muscle tone in the pulmonary vasculature until adolescence. |
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Term
| What conditions can inhibit growth of the pulmonary vascular bed? |
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Definition
| While there are many, lung hypoplasia associated with diaphragmatic hernia is the one listed. |
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Term
| What is the normal position of ribs in kids, and what effect does this have on breathing? |
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Definition
The ribs are horizontal, which produces little movement with inspiration. In fact, the chest wall may move in during inspiration d/t the compliant chestwall.
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Term
What muscle do kids need to breathe?
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Definition
| The diaphragm. So you better believe those kids better be reversed at the end of the case, cuz muscle relaxants will paralyze the diaphragm. |
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Term
| When do the ribs begin to change position? |
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Definition
| When kids begin to assume an upright position |
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Term
| What type of fibers are predominantly in the pediatric diaphragm? |
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Definition
Type II--at birth, they only have 10% type I fibers at 37 weeks, 25% at term, and 50% as adults.
Type I gets breathing done.
Type II tires. |
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Term
How does FRC of kids and adults compare on a kg basis?
What about total lung capacity? |
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Definition
FRC is similar.
Adults have a larger total lung capacity, mostly due to inspiration--adults can generate 100 cm H2O of negative inspiratory pressure |
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Term
| What happens to closing capacity? How does the newborn closing capacity compare to the tidal volume? |
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Definition
| Closing capacity declines through adolescence, then increases with age. In infants, the tidal volume is well within the closing capacity range. |
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Term
| When does the airway resistance change for kids? Does it increase or decrease? |
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Definition
| By age 5. It decreases, which is why little kids with high resistance do not tolerate bronchiolar infections well, developing severe oxygen and ventilation impairment. |
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Term
| In newborns and premies, their tracheal rings are compliant. What does this mean? |
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Definition
| The trachea can collapse on inspiration. |
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Term
| When does surfactant production begin, and when is it adequate? |
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Definition
| Begins at 24 weeks, adequate at 36 |
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Term
| Compare the alveolar-arterial oxygen difference between an adult, premie, and newborn (most to least) |
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Definition
| Preterm >full term > adult |
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Term
Why do babies have a bigger difference in oxygen in the alveoli and the arteries? Why does this change with age?
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Definition
| They have less surface area for diffusion to occur. Diffusion capacity increases with linear height, which is associated with lung growth and age. |
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Term
| How does venous admixture compare in an infant to an adult? How would a patent foramen ovale impact this? |
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Definition
| Newborn venous admixture is 10-20% of cardiac output, compared to 2% in an adult. If baby has a patent foramen ovale, the amount of venous admixture increases! |
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Term
| What is the oxygen consumption rate of a newborn? What is an adult's? |
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Definition
5-8 ml/kg/min
2-3 ml/kg/min |
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Term
| How do tidal volumes compare in a newborn to an adult? |
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Definition
| Nearly the same, about 6 ml/kg |
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Term
How does the newborn ventilatory gas exchange compare to an adults?
How do babies change oxygenation and CO2 elimination rates? |
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Definition
The adult has nearly 10X greater exchange than infants, with a similar TV.
Since infants can't vary TV much, they change their ventilatory rate. |
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Term
What is the normal PaO2 in utero?
What about the PaO2 of a newborn on room air? |
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Definition
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Term
| Are chemoreceptors fully developed at birth? |
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Definition
| No, they are somewhat immature |
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Term
| How do infants respond to an increase in PaCO2? |
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Definition
| They increase alveolar ventilation, just as an adult, however, the strength of the response is directly related to gestational age, as the central chemoreceptors are not fully developed. |
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Term
| Newborns are a little like COPD-ers. What does this tell you about their response to oxygen concentrations? |
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Definition
| Exposure to high concentration of oxygen depresses their respirations, while low concentration stimulate it. |
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Term
| How do micro-premies respond to hypoxia? |
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Definition
| First, they increase respiration for several minutes, then they develop apnea. |
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