Just Breathe: Your Preemie and the Respiratory System

When a baby is born prematurely, they will often have difficulty breathing on their own and need some sort of assistance. The type of respiratory assistance your baby will need will depend on how early your baby was born. You may have been told that your baby has something called RDS. RDS or Respiratory Distress Syndrome is one of the more common problems a baby will encounter when born prematurely.

Before the baby is born, the lungs are collapsed and oxygen is provided to the baby through the placenta. The placenta allows the passage of oxygen and nutrients from the mother’s blood to the baby’s blood via the umbilical cord. After the baby is born this all changes. When the umbilical cord is cut, the lifeline of oxygen enriched placental blood is severed. Air hunger begins and the newborn baby will begin to gasp for air. With this gasp the lungs expand for the first time and convert from a collapsed, solid mass to soft air filled bags.

How Lungs Work

Mature lungs are made up of spongy, elastic tissue that stretches and constricts as you breathe. There are millions of tiny, round pockets called alveoli that expand when air moves in. Inside the alveoli, is a thin layer of liquid called surfactant. Surfactant is soap-like substance that naturally coats the inside of mature lungs and prevents these tiny balloons (alveoli) from collapsing.

Surfactant is essential for this exchange of oxygen and carbon dioxide between the lungs and the blood. Production of surfactant within the cells of the lungs begins between 24 to 28 weeks gestation, with increased production until the baby is term gestation.

When a baby is born too early, they have immature lungs and often lack enough surfactant.

The lungs can’t open up well enough to trap oxygen to be efficiently absorbed into the bloodstream and distributed to the vital body organs. Premature lungs also have fewer immature alveoli that affect the ability to exchange oxygen and carbon dioxide. The lungs continue to make alveoli until delivery. The more preterm the baby the less alveoli they will have. These alveoli are very small and have a moist surface. Wet surfaces stick together, causing surface tension. Surfactant reduces this tension allowing the wet surfaces of the lungs to expand, allowing air exchange.

The air we breathe is made up of several different gases, oxygen, being the most important because the cells need it for energy and growth. Without oxygen, the body’s cells would begin to die. Carbon dioxide is the gaseous waste produced made by the metabolism as part of the energy making processes of the body. The lungs allow oxygen in the air to be taken into the body, while also enabling the body to get rid of carbon dioxide in the air breathed out.

Surfactant is essential for this exchange of oxygen and carbon dioxide between the lungs and the blood. Production of surfactant within the cells of the lungs begins between 24 to 28 weeks gestation, with increased production until the baby is term gestation. When a baby is born too early, they have immature lungs and often lack enough surfactant. The lungs can’t open up well enough to trap oxygen to be efficiently absorbed into the bloodstream and distributed to the vital body organs. Premature lungs also have fewer immature alveoli that affect the ability to exchange oxygen and carbon dioxide. The lungs continue to make alveoli until delivery. The more preterm the baby the fewer alveoli they will have.

Premature Delivery and Respiratory Problems

In general, the earlier the baby is born, the greater risk of developing respiratory distress. If premature delivery can be postponed a day or two, the mother can be given up to 2 injections, 24 hours apart, of steroids, such as betamethasone before delivery. Betamethasone is used to help aid in fetal lung development if premature birth is expected.

Preemies with RDS will usually receive artificial doses of surfactant, given down a breathing tube; directly into the lungs where it coats the air sacs allowing for better air exchange. A baby with RDS may get worse in the first few days of birth, but will show signs of improvement when the lungs begin to produce their own surfactant, usually within a couple of weeks.

Babies with RDS will typically need some form of supplemental oxygen. One way to improve the baby’s oxygen absorption is to increase the concentration of oxygen in the air the infant is receiving. Normal room air is about 21 percent oxygen. Babies requiring supplemental oxygen can receive up to 100 percent oxygen, in extreme cases, if needed. The oxygen settings and levels are monitored very closely as it is important to get the right concentration. Too little can cause damage to the nervous system and too much can cause damage to the lungs themselves, as well as the eyes.

Oxygen saturation monitors, (often referred to as pulse ox or sat probe) are placed on either the foot or wrist of the baby- this measures the oxygen levels in the infants blood. The amount of oxygen is recorded as a percent. This percent is the amount of oxygen the hemoglobin molecule in the blood is carrying.

A blood sample called a blood gas is another way to measure how this exchange is taking place within the baby’s system. This test gives more information than the saturation monitor and is usually used when a baby is on higher levels of respiratory support. The goal is to have the least amount of support to keep the baby’s oxygen levels in the desired range. (This range is based on gestational age.)

There are several different levels of support for a baby with RDS. As the lungs mature, the amount of respiratory support will be reduced in a process called weaning. This weaning process is very individual to the infant and will be determined by how hard the baby is working to breathe, oxygen saturation, and blood gas levels, and overall health of the baby.

Here is some of the more common equipment used for respiratory support, generally explained:

  • Ventilator- Pumps air and oxygen into the lungs through an endotracheal tube. (Also called ET tube or breathing tube.) The ventilator will breathe for the baby and is set to give a breath a certain amount of times a minute.
  • Oscillator- a type of ventilator that works by vibrating oxygen in and carbon dioxide out via hundreds of tiny inflating breathes per minute.
  • Continuous Positive Airway Pressure- Also known as CPAP. CPAP doesn’t mechanically breathe for the baby, but blows a constant stream of air into the infant’s lungs at a low pressure keeping the lungs partially inflated at all times. CPAP is delivered through nasal prongs.
  • (Bubble) CPAP- works by delivering a constant pressure to the infant’s airway. (Via nasal prongs) similar to CPAP but has a breathing circuit that is placed under water, and bubbles- which generates pressure and provides constant oscillation within the lung fields.
  • Nasal Cannula- Oxygen that is delivered directly to the baby through a plastic tube that has small prongs that are placed in the baby’s nostrils.

RDS is very common in the premature baby because the lungs are immature themselves. Based on how early your baby was born will determine how they will progress through this condition. It is very scary to see your little one struggle with the simple things we as adults take for granted every second of every day. Hopefully, this information helped you understand the whys and what’s of RDS and helps you, yourself breathe a little easier, right alongside your baby.

References

Bubbles, Babies and Biology: The Story of Surfactant. (n.d.). Retrieved from http://www.fasebj.org/content/18/13/1624e.full

Facts About Retinopathy of Prematurity (ROP) | National Eye Institute. (n.d.). Retrieved from https://www.nei.nih.gov/health/rop/rop

The Immature Lung - AboutKidsHealth. (n.d.). Retrieved from http://www.aboutkidshealth.ca/en/resourcecentres/prematurebabies/aboutprematurebabies/breathing/pages/the-immature-lung.aspx

Recommendations for neonatal surfactant therapy. (n.d.). Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2722820/

Continue Reading