Respiratory distress syndrome (RDS)

What is it?

RDS, previously known as Hyaline membrane disease, is a breathing problem in premature babies caused by their lungs not being fully developed and not having enough surfactant. It tends to affect babies born at 34 weeks gestation or earlier, and is most common in babies born before 28 weeks.

Most babies who develop RDS show signs of breathing problems at birth or within the next few hours. Their symptoms may include: bluish colour of the skin, shortness of breath and grunting, flaring of the nostrils, brief stops in breathing (apnoea), rapid or shallow breathing, “odd” movement of chest muscles while breathing, puffy or swollen extremities.

Why does it occur?

Normally an unborn baby will start producing surfactant at around 26 to 24 weeks gestation. This liquid coats the insides of the lungs, making them flexible and able to inflate and stay open and filled with air as the baby breathes in and out after birth.

When a baby is born prematurely, their lungs are immature and don’t produce enough surfactant. As a result, the lungs remain stiff and the air sacs tend to collapse when the baby breathes out. The baby then has to work much harder to breathe in.

In addition to prematurity, the chances of having neonatal RDS are increased if the mother has diabetes, if the baby is delivered by caesarean, if labour is short or the baby is one of a multiple (twins or more). Interestingly, the risk may be decreased if the mother has chronic, pregnancy-related high blood pressure or prolonged rupture of membranes, because the stress of these situations causes the infant’s lungs to mature sooner.

Why is it a problem?

Without surfactant, the lungs collapse and the baby has to work hard to breathe. The muscles used for breathing tire and become weak. Low oxygen levels in the blood, if untreated, will eventually lead to damage to the brain and other organs.

Severe RDS may also lead a baby to develop other serious medical problems, such as a collapsed lung, bronchopulmonary dysplasia (another lung disease in premature babies), IVH (bleeding in the brain), bleeding in the lung, eye problems such as ROP, and necrotising enterocolitis (NEC), a disease of the bowel. In some cases severe RDS may be fatal.

How is it treated?

Doctors try to prevent RDS from developing by delaying delivery until the baby’s lungs have matured (after 34 weeks). Even a few days can make a big difference to lung maturity.

If labour cannot be delayed, the mother may be given injections of a corticosteroid medicine. This drug can speed up surfactant production and development of the baby’s lungs, brain and kidneys so that 24-48 hours after starting the injections, the baby’s chances of developing RDS are reduced, or if they do develop RDS, it will be milder. Steroids also reduce the chances of your baby having IVH or NEC.

Once a baby is born and diagnosed with RDS, the main treatments are

• For babies with mild RDS – supplemental oxygen, usually delivered via a tube in the nose.

• For babies with more severe RDS – replacement surfactant and breathing support.

Giving the baby replacement surfactant until their lungs are developed enough to start making their own can be lifesaving. Surfactant is often given directly to the lungs via a ventilator (breathing machine) while the baby is intubated, and treatment may be repeated several times over the first few days. Since treatment with surfactant was introduced in the 1990s, deaths from RDS have greatly reduced.

Baby on CPAP

Breathing support can be via a ventilator such as a high frequency oscillator (HFO) with a breathing tube running through the baby’s mouth or nose into the windpipe. This is known as intubation and tends to be used for babies who are really struggling to breathe for themself. Where a baby can breathe but needs help to keep the airways open, hospitals tend to use CPAP (continuous positive airway pressure) where a machine pushes slightly pressurized air into the baby’s lungs via prongs in the nostrils. Additional oxygen may be given at the same time. Although breathing support can be essential, pressure can lead to damage to the fragile lung tissue and excess oxygen can cause eye problems, so oxygen and pressure are reduced as soon as possible to avoid any side effects.

All babies with RDS need supportive care to help reduce their oxygen needs. This includes gentle handling, minimising disturbances and maintaining an ideal body temperature.

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This is one of a series of articles I’ve written for the L’il Aussie Prems newsletter under the heading of Premmie Health. Read my disclaimer here.