Hyaline membrane disease (HMD), also called respiratory distress syndrome (RDS), is one of the most common problems of premature babies. It can cause babies to need extra oxygen and help breathing. The course of illness with hyaline membrane disease depends on the size and gestational age of the baby, the severity of the disease, the presence of infection, whether or not a baby has a patent ductus arteriosus (a heart condition), and whether or not the baby needs mechanical help to breathe. HMD typically worsens over the first 48 to 72 hours, then improves with treatment.
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. Surfactant is found in amniotic fluid between 28 and 32 weeks. By about 35 weeks gestation, most babies have developed adequate amounts of surfactant.
Surfactant is normally released into the lung tissues where it helps lower surface tension in the airways. This 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 and further affect breathing ability. These cells are called hyaline membranes. The baby works harder and harder at breathing, trying to re-inflate the collapsed airways.
As the baby's lung function decreases, less oxygen is taken in and more carbon dioxide builds up in the blood. This can lead to increased acid in the blood called acidosis, a condition that can affect other body organs. Without treatment, the baby becomes exhausted trying to breathe and eventually gives up. A mechanical ventilator (breathing machine) must do the work of breathing instead.
HMD occurs in over half of babies born before 28 weeks gestation, but only in less than one-third of those born between 32 and 36 weeks. Some premature babies develop HMD severe enough to need a mechanical ventilator (breathing machine). The more premature the baby, the higher the risk and the more severe the HMD.
Although most babies with HMD are premature, other factors can influence the chances of developing the disease. These include the following:
The following are the most common symptoms of HMD. However, each baby may experience symptoms differently. Symptoms may include:
The symptoms of HMD usually peak by the third day, and may resolve quickly when the baby begins to diurese (excrete excess water in urine) and begins to need less oxygen and mechanical help to breathe.
The symptoms of HMD may resemble other conditions or medical problems. Always consult your baby's physician for a diagnosis.
HMD is usually diagnosed by a combination of assessments, including the following:
Specific treatment for HMD will be determined by your baby's physician based on:
Treatment for HMD may include:
Babies with HMD sometimes 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:
Preventing a preterm birth is the primary means of preventing HMD. 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.