Congenital high airway obstruction syndrome
Congenital high airway obstruction syndrome, or CHAOS, is a blockage of the fetus's trachea (windpipe) or larynx (voice box). This obstruction can be due to a number of factors, including narrowing of the airway, called stenosis; a web-like membrane; or even an area of the trachea that is missing, called atresia.
During pregnancy, the fetal lungs constantly produce fluid. If the airway is blocked, this fluid can't escape out the mouth and the baby's lungs become distended. This can put pressure on the heart and affect its function. If the heart can't beat effectively, congestive heart failure can occur.
The cause of CHAOS is currently unknown. It is a very rare condition and is not thought to recur in families.
The outcome for CHAOS depends greatly on what's causing the obstruction. If the obstruction is minor — a thin tissue membrane covering the larynx — it may be correctable with minor surgery before or after birth with no lasting complications.
A complete blockage of the larynx or a missing section of trachea is more serious. In these cases, the baby will not be able to breathe when born, and will need a tracheostomy after birth as well as multiple operations to correct the airway. There may also be problems with the ability to talk and to eat and drink by mouth. In more extreme cases, in which the lung swelling endangers the heart function, the fetus may need surgery before birth.
The condition can also be complicated by the presence of other birth defects, so it is important to test for other abnormalities. Amniocentesis can be used to test for problems with the baby's chromosomes, and an echocardiogram can be used to look more closely at the fetal heart structure and function.
If the chromosomes are normal and there are no additional birth defects other than CHAOS, the severity of the condition depends on the type of malformation causing the airway obstruction.
To determine the severity of the problem, a number of tests are recommended:
- Amniocentesis to look for chromosomal abnormalities
- A level II ultrasound to look for other abnormalities and to examine the anatomy of the airway
- A fetal echocardiogram to determine if the fetus has an associated heart defect or if the function of the heart has been affected
- An MRI to obtain an accurate picture of the airway and determine the level and length of the obstruction in the airway
After CHAOS is fully diagnosed through a formal evaluation, your doctor will explain your treatment options. In severe cases where the fetus has hydrops, fetal surgery to relieve the obstruction may be offered. Hydrops is the build-up of excess fluid, which can be seen in the fetal abdomen, lungs, skin or scalp.
If there is no fetal hydrops, we recommend delivering the baby via the EXIT (Ex Utero Intrapartum Treatment) procedure. The EXIT procedure is for babies who are known to have an airway obstruction. The goal is to provide the baby with a functioning airway so that oxygen can be delivered to the lungs after the baby is separated from placenta.
The EXIT procedure is a planned, specialized delivery. It should only be performed at a hospital that can provide a team consisting of a pediatric surgeon, an obstetrician, an anesthesiologist and a neonatologist.
The procedure begins much like a Caesarean section. However, unlike a Caesarean delivery, the mother is put under general anesthesia to ensure that the uterus is completely relaxed.
The baby's head is delivered and the pediatric surgeon passes a bronchoscope through the baby's mouth to look more closely at the airway. Depending on the type of blockage, the surgeon may then attempt to pass a tube through the baby's mouth into the trachea and give breaths to the baby. If this is successful, and oxygen is being delivered to the baby through the tube, the infant is delivered and the umbilical cord cut.
If a tube can't be passed from the mouth through the obstruction, the pediatric surgeon will need to place a tracheostomy tube through the neck directly into the trachea, bypassing the blockage. The surgeon will make an incision in the baby's neck and will place a tube below the airway blockage. Once the tube is placed, and the surgeon is confident that it is functioning and can be used to deliver oxygen to the baby, the infant is delivered.
After delivery via an EXIT procedure, the infant is brought to the Intensive Care Nursery for close observation and further assessment. Additional reconstructive surgeries may be needed.
UCSF Benioff Children's Hospitals medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your child's doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your child's provider.
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