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Clinical Reference Systems: Pediatric Advisor 10.0
Respiratory Distress Syndrome (RDS)
DESCRIPTION
If a baby is born before his lungs have matured, he will
develop respiratory distress syndrome (RDS). A baby with
RDS tries to cry and breathe at birth, but within minutes to
hours he starts working hard to breathe because his lungs
tend to collapse with each breath.
A baby with RDS:
- breathes faster than 60 breaths a minute
- makes a grunting sound when he breathes out
- pulls in the chest wall and the spaces between the ribs
when he tries to breathe (these movements during
breathing are called retractions)
- has flaring of the nostrils
- has a bluish color around the lips, which means that he
needs more oxygen.
CAUSE
Before birth a baby does not use his lungs because the
placenta transports oxygen from the mother to the baby's
bloodstream. However, once the baby is born, the lungs fill
with air and begin transporting oxygen into the bloodstream.
To prepare the lungs to work properly after birth, a baby
produces a substance called surfactant. Surfactant is a
material that lines the air sacs of the lungs and helps keep
the lungs open when we breathe out. Without surfactant, the
lungs tend to collapse with each breath. A lack of
surfactant causes RDS.
Babies usually start making surfactant sometime between the
30th and 36th weeks of the pregnancy. Nearly all babies
have made surfactant by the 35th week of pregnancy. Certain
events, such as premature rupture of the membranes (water
breaking early) or preterm labor, may cause a baby to start
making surfactant early. Drugs can be given to the mother
to help start production of surfactant by a baby before
birth. The most frequently used drug is betamethasone.
We can tell whether a baby has made surfactant by testing
the amniotic fluid. Amniotic fluid is collected by
amniocentesis. After the rupture of membranes it may be
obtained from the vagina. If the baby has not yet made
surfactant, the mother may be given betamethasone and the
doctor will try to delay the birth.
Two other causes of breathing problems in babies are
infection in the lungs (pneumonia) and extra fluid in the
lungs.
TREATMENT
Many babies develop RDS. Usually the babies who have RDS
are more than 6 weeks premature, but occasionally more
mature babies have RDS. There are many effective treatments
for babies with RDS, and most infants recover completely
within the first weeks of life.
- The special care nursery (SCN)
A baby who has breathing difficulties is placed on a
warming bed in the special care nursery (SCN). He is
attached to a monitor that continuously measures his
heart rate and respiratory (breathing) rate. This
monitor is called a cardiorespiratory monitor. The baby
is also attached to a monitor that records the amount of
oxygen in his skin. It is called a pulse oximeter.
- Laboratory tests
Certain laboratory tests are done to help determine the
cause of the breathing problems. These tests include
blood tests and an x-ray of the baby's chest. X-rays
for babies use very little radiation and do not cause
the baby any problems later in life.
- IV fluids
A baby with RDS breathes fast and uses all of his energy
to breathe. He does not have any energy left for eating
and cannot coordinate sucking with the fast breathing
rate. An intravenous (IV) line is inserted into the
veins of the baby's hands, feet, or scalp. The IV
provides fluid to prevent dehydration and gives the baby
sugar for energy. The baby will be able to take milk
after the lungs have improved.
All babies can go 4 or more days on IV fluids without
eating and be perfectly fine. Don't worry if your baby
can't eat at first and loses weight. Once he is well,
he will make up for lost time. Even a healthy baby who
eats immediately after birth loses weight in the first
week of life.
- Antibiotics
Because the cause of a breathing problem may not be
known right away, all babies are treated for the
possibility of infection with antibiotics. Before
starting the antibiotics, a sample of the baby's blood
is tested for infection. The test is called a blood
culture. If the baby does not have an infection, the
test will be negative and the antibiotics will be
stopped in 3 days. Antibiotics are safe and do not
cause any long-term problems.
- Oxygen
We breathe 21 percent oxygen from normal air. The most
oxygen we can breathe is 100 percent oxygen. A baby
with RDS needs to be given extra oxygen to keep the
level of oxygen in his blood in the normal range. If
tests show that a baby needs extra oxygen, he is placed
in a plastic hood into which extra oxygen is blown.
We call the level of oxygen a baby breathes the FiO2.
We call the level of oxygen in the blood the pO2.
- Blood gases
Blood gas tests show how much oxygen is in the
bloodstream. This information helps your physician know
how much oxygen the baby needs. It also indicates
indirectly how hard the baby is working to breathe and
whether he needs help to keep breathing.
Samples of blood may be obtained from the baby's heel (a
heel stick). Or the sample of blood may be gotten
directly from an artery.
- Umbilical artery catheter
If a baby needs more than 40 percent oxygen or a
ventilator to breathe, the blood gases are checked
frequently. So the baby does not have to be stuck with
a needle each time a sample of blood is needed, an IV
line may be inserted into an artery. The IV is often
placed in the artery in the umbilical cord and passed
into the aorta, the largest artery in the body. This
umbilical artery catheter allows blood to be taken
painlessly from the baby. The catheter can also be used
to give fluids and medications to the baby. Arteries in
the hands and feet may also be used for arterial lines.
- Assisting the baby's breathing
If the work of breathing becomes too difficult for the
baby, he will begin to tire. There are two ways to help
his breathing: nasal CPAP and a ventilator.
- Nasal CPAP
Nasal CPAP is a device that blows oxygen under
pressure in through the nose. It helps inflate the
lungs. A strap placed around the baby's head holds
the CPAP prongs in the nose. The baby does all the
breathing but the CPAP delivers oxygen at a pressure
that keeps the lungs inflated. Nasal CPAP is used
for the bigger and stronger babies or babies who have
mild disease and need just a little help.
- Ventilator
When a baby gets too tired to breathe effectively, a
ventilator may be used to give the baby extra
breaths. A tube is placed through the baby's mouth
and into the windpipe (trachea). The tube is kept in
place with tape across the baby's upper lip. The
ventilator blows oxygen under pressure through the
tube and into the baby's lungs. The baby breathes on
his own, but the ventilator gives extra breaths.
Babies usually get used to the ventilator and
actually feel more comfortable because they don't
have to work so hard to breathe. Occasionally a baby
may be irritated by the ventilator. If this happens
the baby may be given a mild sedative to help him
relax and sleep.
- Artificial surfactant
Babies who need a ventilator may be given two to four
doses of artificial surfactant during their first 24 to
48 hours of life. If artificial surfactant is given,
not as much oxygen or pressure on the ventilator will
have to be used, and the baby will get better faster.
The baby will still need the ventilator for about 3 days
and then will begin to get better as his lungs make his
own surfactant.
- Recovery
A baby with RDS is sick for about 3 days. In the first
3 days his need for oxygen will increase or stay the
same. He may tire and need to be placed on nasal CPAP
or a ventilator.
When the amount of oxygen a baby needs decreases, we
know he is getting better. If the baby is on the
ventilator, the amount of oxygen and breaths he is given
will be reduced until he can be allowed finally to
breathe on his own. At this time the breathing tube can
be removed (extubation).
- Feedings
When the baby is able to breathe easily at a normal rate
and does not need extra oxygen, he can begin feedings.
If the baby is strong and mature enough to suck, he can
begin to breast-feed or bottle-feed. However, often a
baby is weak because his lungs are still recovering. A
weak baby can be fed by passing a tube through his mouth
and into his stomach. Milk is dripped through the tube
into the baby's stomach. This is called gavage feeding.
This way the baby can be fed without using a lot of
energy to suck. Soon he will be able to breast- or
bottle-feed vigorously.
POTENTIAL COMPLICATIONS
Most babies recover completely from RDS with no short-
or long-term problems. The most common complication
occurring shortly after birth is a pneumothorax.
Long-term problems, such as chronic lung problems or
neurologic problems (brain damage), are usually related
to how premature the baby is rather than to the RDS.
- Pneumothorax
Sometimes the air sacs of a baby's lungs tear. The air
that should be inside the air sacs escapes outside the
lungs but remains inside the chest. The accumulated air
then presses on the lung and makes it even more
difficult for the baby to breathe. This is called an
air leak, or pneumothorax. A pneumothorax may occur at
any time with no apparent cause, or it may happen when
the baby is receiving oxygen under pressure (on CPAP or
a ventilator).
A small pneumothorax does not require treatment. A
larger one is treated by drawing the air out through a
needle. For the largest or most persistent air leaks, a
tube is inserted into the chest and the air is drained
out continuously. Over time (hours to days), the air
sacs heal themselves and the tube can be removed.
- Chronic lung disease
Babies who have unusually severe lung disease or are
very premature may require a lot of oxygen and pressure
from the ventilator to survive. This can scar the
lungs. Some of these babies may need to be on the
ventilator for several weeks and may need oxygen for
several months. These babies may be given steroids in
small amounts to reduce inflammation and scarring.
Most babies outgrow these problems in the first few
months. They grow new lung tissue, which replaces the
scarred lung tissue. However, during the first few
years of life they may have more bouts of wheezing and
may get pneumonia when they have upper respiratory
infections (colds). These problems will occur less
often as the children grow older.
LONG-TERM OUTCOME
Virtually all babies who have respiratory distress syndrome
grow up to be healthy, normal children. RDS does not cause
brain damage or long-term developmental problems.
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