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What is congenital high airway obstruction?

Congenital high airway obstruction (CHAOS) is a complete or nearly complete obstruction of the fetal airway.

The obstruction can be due to a variety of causes including:

  • a cyst in the larynx
  • a membrane that blocks the larynx or trachea
  • a malformation that closes off the trachea or larynx
  • a narrowing of the glottis (the middle part of the larynx)

This obstruction causes some serious problems in the fetus:

  • swelling of the lungs
  • swelling of the trachea and bronchial tubes
  • heart failure

Prenatally diagnosed CHAOS requires intervention sometime before your baby takes his first breath.

How often does congenital high airway obstruction occur?

CHAOS was once thought to be extremely rare. Yet, more than a dozen cases have been reported since 1989.

Researchers believe that CHAOS may be more common than they realized, since many fetuses affected with this condition either do not make it to term or are born without being diagnosed.

What causes congenital high airway obstruction?

No one knows. It occurs by chance. No hereditary basis has been identified.

Hope and compassionate care

The Maternal Fetal Care Center (MFCC) of Boston Children's Hospital is making a significant difference in the outcomes for families facing complex birth defects and other critical challenges to the health of their fetus or newborn.

We've got the expert physicians and staff to significantly improve outcomes for babies with complex health concerns like CHAOS, while delivering hope and compassionate care to families along the way.

Congenital High Airway Obstruction (CHAOS) | Diagnosis & Treatments

How is congenital high airway obstruction diagnosed?

CHAOS is first detected on prenatal ultrasound. If your doctor suspects a problem, you will be referred to a doctor who specializes in high-risk cases for a more detailed ultrasound.

What signs will my doctors look for in the ultrasound?

The main signs are swollen and elongated trachea and bronchial tubes. This swelling happens as a result of a build-up of fluid normally expelled through the trachea with fetal breathing movements.

In more advanced cases, doctors may notice the following:

  • signs of impending heart failure (hydrops)
  • polyhydramnios (excess amniotic fluid)
  • ascites (accumulation of fluid in the abdominal cavity)

The fetus may also appear to have abnormal breathing movements.

Will my doctor order any other tests?

Your doctor may decide that you should have an MRI (magnetic resonance imaging) of your abdomen to get better pictures of the fetus and to determine what's causing the obstruction, whether it's a cyst in the larynx, or atresia either of the larynx or trachea.

MRI may be necessary to rule out other conditions that resemble CHAOS, particularly cystic adenomatoid malformation (CCAM).

How is congenital high airway obstruction treated?

The first step in management may be further testing so that doctors can learn more about your baby's condition. There is a wide range of other congenital problems that seem to coincide with laryngeal atresia, such as abnormalities of the vertebrae, trachea, urinary tract, and heart.

These studies can include:

  • Fetal echocardiogram: This test is an ultrasound test performed during pregnancy to evaluate the heart of the unborn baby. Echocardiography assesses the heart's structures and function.
  • Amniocentesis: An amniocentesis is a procedure used to obtain a small sample of the amniotic fluid that surrounds the fetus to diagnose chromosomal disorders and open neural tube defects.

Will I have to have surgery?

Probably. All fetuses with advanced CHAOS require surgery before birth since there is a significantly high risk of death at birth if no intervention takes place.

The operation is usually performed as the baby is delivered by a procedure called ex utero intrapartum treatment (EXIT). For this procedure, the baby must be delivered at a hospital that specializes in EXIT like Children's.

EXIT procedure

Doctors perform a Cesarean section while the mother is under deep general anesthesia.

  • Doctors deliver only the fetus's head and neck so that the fetus is still sustained by the placenta.
  • The goal here is to stabilize the fetus's airway, so that when contractions begin the baby can breathe; the surgeons usually have about an hour.

This surgery may be performed as early as 24 weeks gestation, depending on how severe the problem is. To secure the airway, surgeons will perform one or a combination of the following procedures depending on what's causing the obstruction and how severe it is:

  • Laryngoscopy: This allows doctors to examine the interior of the larynx with an instrument called a laryngoscope. They may try to bypass the obstruction with an endotracheal breathing tube.
  • Bronchoscopy: This procedure uses a bronchoscope, which is designed to examine or treat the bronchi. Doctors may try to disrupt the obstruction if it's in the form of a cyst or a simple membrane.
  • Tracheostomy: If other efforts have failed, doctors will create a surgical opening through the skin into the trachea below the obstruction to create a temporary airway.

If the airway cannot be secured in time, the baby may be placed onto ECMO (heart-lung bypass).

What happens after the airway is secured?

Your baby will be placed in critical care. There, a neonatologist will examine your baby for any possible problems associated with CHAOS. Your baby will probably have blood tests, x-rays, an ultrasound, and an echocardiogram.

Once other conditions are ruled out, your baby will probably undergo surgery to either remove the obstruction, if necessary, and/or to repair the malformation in the larynx or trachea, such as atresia, that caused the problems.

What treatment will I have?

After delivery, our surgeon will work closely with an anesthesiologist to make sure any risks of maternal bleeding are minimized.

For more information about maternal risks associated with fetal surgery, be sure to talk to your doctor so that you understand them fully.

What's the outlook for my child?

After treatment, your baby will require close follow-up care.

  • If the obstruction was caused by a simple cyst or web in the larynx, your child should have normal speech.
  • If there was a severe malformation in the larynx, normal speech is less certain.

Otherwise, your child should be very healthy.

Congenital High Airway Obstruction (CHAOS) | Programs & Services