What happens in respiratory distress syndrome in premature infants?

Respiratory distress syndrome (RDS) is a breathing problem that affects newborns, mostly those who are born more than 6 weeks early. The earlier or more premature a baby is born, the more likely the baby will develop RDS.

Many babies with milder symptoms get better in 3–4 days. Those who are very premature may take longer to recover.

What Are the Signs & Symptoms of Respiratory Distress Syndrome?

Within minutes or hours of being born, a baby with RDS will have breathing problems. If untreated, these problems get worse over time.

Symptoms of RDS include:

• fast breathing
• noisy breathing or grunting
• retractions (a tugging in of the muscles between the ribs, under the ribcage, and at the neck) while trying to breathe
• a blue tint in the lips, nail beds, and skin from lack of oxygen, called

What Happens in Respiratory Distress Syndrome?

RDS happens when a baby's lungs don't make enough of a fatty substance called surfactant (ser-FAK-tent).

Surfactant is made in the last few weeks of pregnancy. It helps tiny air sacs in the lungs called alveoli (al-VEE-oh-lye) open more easily. These sacs fill with air when a baby breathes after birth. Surfactant also helps keep the alveoli open when air leaves the lungs.

When a baby with RDS tries to breathe:

• many of the alveoli cave in and can't open
• oxygen can't get to the blood
• carbon dioxide can't leave the body

If untreated, in time this can damage a baby's brain and other vital organs.

How Is Respiratory Distress Syndrome Diagnosed?

Health care providers will suspect RDS in a premature baby who has trouble breathing and needs oxygen soon after birth. A chest X-ray of the lungs can confirm the diagnosis.

How Is Respiratory Distress Syndrome Treated?

To help prevent respiratory distress syndrome, doctors can give steroid medicines to pregnant women who are likely to deliver their babies early (before 37 weeks of gestation). Steroids help the baby's lungs mature and make more surfactant before the baby is born.

Doctors will give oxygen to a baby who has signs of RDS and breathing trouble. If breathing problems continue, the baby may need continuous positive airway pressure (CPAP). With CPAP:

• The baby wears a mask or a  that's connected to a machine.
• The machine sends a stream of air or oxygen into the lungs through the nose.

CPAP opens the alveoli, supplies oxygen, and prevents the alveoli from collapsing. A baby who continues to have signs of respiratory distress or trouble maintaining a good oxygen level may need more support with a breathing machine or ventilator.

Babies with RDS may need treatment with surfactant. Doctors give surfactant through a breathing tube right into the lungs.

Babies with RDS get treatment in a neonatal intensive care unit (NICU). There, a team of experts cares for these newborns, including:

• doctors who specialize in newborn care (neonatologists)
• skilled nurses and neonatal nurse practitioners
• respiratory therapists, who help with breathing machines

Many babies start to get better within 3 to 4 days, as their lungs start to make surfactant on their own. They'll start to breathe easier, look comfortable, need less oxygen, and can be weaned from the support of CPAP or a ventilator. Some babies — especially very premature babies — need longer treatment until they can breathe on their own.

What Else Should I Know?

Respiratory support with oxygen and a ventilator helps newborn babies with respiratory distress. But long-term use can damage a premature baby's lungs. Some babies born very early need oxygen support for a long time, leading to a condition called bronchopulmonary dysplasia (BPD).

Hyaline membrane disease (HMD), also called respiratory distress syndrome (RDS), is a condition that causes babies to need extra oxygen and help breathing.

• HMD is one of the most common problems seen in premature babies.
• The more premature the baby, the higher the risk and the more severe the HMD.
• HMD typically worsens over the first 48 to 72 hours and then improves with treatment.
• More than 90 percent of babies with HMD survive.

At Children’s Hospital Boston, we care for newborn babies who need intensive medical attention in a special area of the hospital called the Neonatal Intensive Care Unit (NICU). The NICU combines advanced technology and trained professionals to provide specialized care for the tiniest patients.

What causes HMD?

HMD occurs when there is not enough of a substance in the lungs called surfactant. Surfactant is made by the cells in the airways and consists of phospholipids and protein. It begins to be produced in the fetus at about 24 to 28 weeks of pregnancy, and is found in amniotic fluid between 28 and 32 weeks. By about 35 weeks gestation, most babies have developed adequate amounts of surfactant.

What does surfactant do?

In healthy lungs, surfactant is released into the lung tissues where it helps lower surface tension in the airways, which helps keep the lung alveoli (air sacs) open. When there is not enough surfactant, the tiny alveoli collapse with each breath. As the alveoli collapse, damaged cells collect in the airways, which makes it even harder to breath. These cells are called hyaline membranes. Your baby works harder and harder at breathing, trying to re-inflate the collapsed airways.

As your baby's lung function decreases, less oxygen is taken in and more carbon dioxide builds up in the blood. This can lead to acidosis (increased acid in the blood), a condition that can affect other body organs. Without treatment, your baby becomes exhausted trying to breathe and eventually gives up. A mechanical ventilator (breathing machine) must do the work of breathing instead.

What factors determine how HMD progresses?

The course of illness with HMD depends on the size and gestational age of your baby, the severity of the disease, the presence of infection, whether or not your baby has a patent ductus arteriosus (a heart condition) and whether or not she needs mechanical help to breathe.

Who is affected by HMD?

HMD occurs in about 60 to 80 percent of babies born before 28 weeks gestation, but only in 15 to 30 percent of those born between 32 and 36 weeks. About 25 percent of babies born at 30 weeks develop HMD severe enough to need a mechanical ventilator (breathing machine).

Although most babies with HMD are premature, other factors can influence the chances of developing the disease. These include the following:

• Caucasian or male babies
• previous birth of baby with HMD
• Cesarean delivery
• perinatal asphyxia (lack of air immediately before, during or after birth)
• cold stress (a condition that suppresses surfactant production)
• perinatal infection
• multiple births (multiple birth babies are often premature)
• infants of diabetic mothers (too much insulin in a baby's system due to maternal diabetes can delay surfactant production)
• babies with patent ductus arteriosus

What are the symptoms of HMD?

While each baby may experience symptoms differently, some of the most common symptoms of HMD include:

• difficulty breathing at birth that gets progressively worse
• cyanosis (blue coloring)
• flaring of the nostrils
• tachypnea (rapid breathing)
• grunting sounds with breathing
• chest retractions (pulling in at the ribs and sternum during

Symptoms of HMD usually peak by the third day and may resolve quickly when your baby begins to diurese (excrete excess water in urine) and needs less oxygen and mechanical help to breathe.

What complications are associated with HMD?

Your baby may develop complications of the disease or problems as side effects of treatment. As with any disease, more severe cases often have greater risks for complications. Some complications associated with HMD include the following:

• air leaks of the lung tissues such as:
• pneumomediastinum - air leaks into the mediastinum (the space between the two pleural sacs containing the lungs).
• pneumothorax - air leaks into the space between the chest wall and the outer tissues of the lungs
• pneumopericardium - air leaks into the sac surrounding the heart
• pulmonary interstitial emphysema (PIE) - air leaks and becomes trapped between the alveoli, the tiny air sacs of the lungs
• chronic lung disease, sometimes called bronchopulmonary dysplasia

Can HMD be prevented?

The best way of preventing HMD is by preventing a preterm birth. When a preterm birth cannot be prevented, giving the mother medications called corticosteroids before delivery has been shown to dramatically lower the risk and severity of HMD in the baby. These steroids are often given to women between 24 and 34 weeks gestation who are at risk of early delivery.

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