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300 Longwood Avenue
Boston, MA 02115
(617) 355-6000
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My Child Has:
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Congenital High Airway Obstruction (CHAOS)
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Congenital high airway obstruction is a complete or nearly complete obstruction of the fetal airway that blocks the upper trachea (windpipe) or larynx (voice box). The obstruction can be due to a variety of causes including: a cyst in the larynx, a membrane (web) that blocks the larynx or trachea , a malformation that closes off the trachea or larynx (atresia), or a narrowing of the glottis. See Respiratory System This obstruction causes the lungs to swell and elongate, the tracheobronchial tree to dilate and eventually may cause congenital heart failure. (hydrops) Prenatally diagnosed CHAOS requires intervention sometime before the baby takes a first breath.
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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 most realize since many fetuses affected with this condition either do not make it to term or are still born and were never diagnosed.
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The cause of this condition is unknown. It occurs sporadically, meaning it does not recur in families.
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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 Level 3 ultrasound. Doctors will probably notice that the fetus's tracheobronchial tree is stretched out and swollen (distended) This distention can be traced to the level of obstruction in the trachea and is caused by a build up of fluid naturally produced in the lungs of the fetus. This fluid is normally expelled through the trachea with fetal breathing movements.
In more advanced cases, doctors may notice signs of impending heart failure (hydrops), polyhydramnios (excess amniotic fluid) and/or ascites (accumulation of fluid in the entire abdominal cavity, in spaces between tissues and organs.) The fetus may also appear to have abnormal breathing movements. Your doctor may decide that you should have an MRI (Magnetic Resonance Imaging) of your abdomen to get better pictures of the fetus. MRI is a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body. MRI may be necessary to rule out other conditions that resemble CHAOS, particularly cystic adenomatoid malformation (CCAM).
The doctor may also use MRI (Magnetic Resonance Imaging) of your abdomen to get better pictures of the fetus and help determine what's causing the obstruction, whether it's a cyst in the larynx or atresia either of the larynx or trachea. MRI can also help rule out other conditions that resemble CHAOS, particulary congenital cystic adenomatoid malformation (CCAM).
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The first step in management of this condition may be further testing so that doctors can learn more about your baby's condition. For example, 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. Some cases of CHAOS, however, have no associated problems, but the doctor will want to check for them. These studies can include:
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- 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. A small probe called a transducer (similar to a microphone) is placed on the mother's abdomen and sends out ultrasonic sound waves at a frequency too high to be heard. When the transducer is placed in certain locations and at certain angles, the ultrasonic sound waves move through the mother's and baby's skin and other body tissues to the baby's heart tissues, where the waves bounce (or "echo") off of the heart structures. The transducer picks up the reflected waves and sends them to a computer. The computer interprets the echoes into an image of the heart walls and valves. For more on this test, see Fetal Echocardiography.
- 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. The procedure involves inserting a long, thin needle through the mother's abdomen into the amniotic sac to withdraw a small sample of the amniotic fluid for examination. The amniotic fluid contains cells shed by the fetus, which contain genetic information. For more on this test, see Amniocentesis.
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A surgical plan, based on all of this information, will be put together that considers the CHAOS and associated problems, if there are any. All fetuses with advanced CHAOS require surgery before birth since there is a significantly high risk of perinatal death (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.
During this procedure, doctors perform a Cesarean section while the mother is under deep general anesthesia. The right level of anesthesia is critical for obtaining relaxation of the uterus and the normal exchanges of blood and gases between mother's uterus and placenta.
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 uteroplacental gas exchange is shut down, the baby can breath. Usually, surgeons have about an hour before contractions begin and uteroplacental exhange is cut off. 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:
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- Laryngoscopy: 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.
- Bronchosopy: allows doctors to use 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.
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Once the airway is secured, the cord is clamped and the infant is placed in critical care. If the airway cannot be secured in time, the baby may be placed onto ECMO (heart lung bypass.) After delivery, the surgeon will work closely with the 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.
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Once the airway is secured, the cord is clamped and the infant is placed in critical care. If the airway cannot be secured in time, the baby may be placed onto ECMO (heart lung bypass.) After delivery, the surgeon will work closely with the 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.
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Once the airway is established and your newborn is stabilized, a neonatologist will examine the baby for any possible problems associated with CHAOS discussed above. Your baby will probably undergo blood tests, x-rays, ultrasound, 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.
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These babies require close follow-up. Very little information exists on long-term outcome. What is known is that if the obstruction was caused by a more simple laryngeal cyst or web, normal voice function is likely. If there was a severe malformation in the larynx, normal speech is less certain. Otherwise these children are usually very healthy.
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The information on this website should not be taken as medical advice,
which can only be given to you by your personal health care professional. |
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Copyright © Children's Hospital Boston. All rights reserved. |
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