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  • Glossary: Explanation of Medical Terms

  • Alveole: an air-filled "bubble" lined with thin lung cells (epithelial cells) that is the smallest unit of lung tissue. Our lungs are composed of millions of such alveoli.

    Bochdalek: a type of diaphragmatic hernia named after Vincent Alexander Bochdalek, the Czech anatomist (1801-1883) who first described the condition. It is the most common type of diaphragmatic hernia, whereby the hole in the diaphragm is in the back. It is more common on the left than on the right.

    Carbon dioxide: carbon dioxide is a gas that is made as a byproduct of breathing (when oxygen is used by the body). Just as oxygen is breathed into the lungs, carbon dioxide is breathed out. One of the main functions of blood is to transport oxygen from the lungs (or the placenta, in the fetus) to the tissues in the body, and to transport carbon dioxide from the tissues back to the lung (or placenta), so that the body can get rid of it.

    Chromosomal: a disease or condition is called chromosomal when it is known to occur because of the presence of an abnormal chromosome. Normally, there are 26 pairs of chromosomes in each human cell. If there is one copy of a chromosome too many, the condition is called trisomy. The most common trisomies are Trisomy 13, Trisomy 18 and Trisomy 21 (Down syndrome). Because of the thousands of genes on each chromosome, chromosomal anomalies are generally much more serious than genetic anomalies.

    Congenital: a condition that is present at or before birth. For example, a congenital diaphragmatic hernia is a hole in the diaphragm that is present in the fetus.

    Congenital diaphragmatic hernia (CDH): a hole in the diaphragm found in the fetus, which causes the intestines and other abdominal organs to move into the chest and compress the lungs, and often causes severe breathing problems at birth.

    Diaphragm: the thin muscle layer that separates the chest from the abdominal cavity.

    Endoscopic fetal surgery: the technique of operating on a fetus or the placenta through tiny telescopes and surgical instruments, without having to open the uterus.

    Esophagus: the food-pipe. In the embryo, the trachea (wind-pipe) and bronchi (the smaller airways) form from an outpouching of the upper portion of the esophagus.

    Extracorporeal Membrane Oxygenation (ECMO): an artificial lung system that allows the baby's lungs to rest, while blood is directed through a circuit with a "membrane oxygenator" that acts like a lung. Often used for newborns with pulmonary hypoplasia or other temporary lung problems, such as meconium aspiration syndrome.

    Feeding tube: infants who are not able to feed by mouth may require a small plastic tube into their stomach to feed them that way. Sometimes (especially if it appears that a feeding tube will have to be used for a long time), it may be better to surgically place a small tube directly into the stomach (gastrostomy tube, or "G-tube").

    Fetal: related to the fetus.

    Fetal intervention: any treatment applied directly to the fetus, before birth. More specifically, an operation or other invasive procedure on the fetus.

    Fetal surgery: the most aggressive form of fetal intervention, whereby an operation is performed on the fetus. This can be done by "open" fetal surgery, where the fetus is partially removed from the uterus through a large incision in the mother's abdominal wall and uterus, or endoscopically, whereby tiny telescopes and surgical instruments are introduced into the uterus.

    Familial: a condition or disorder that is seen in several members of a family. Familial conditions are suspected to be genetic: predetermined by a gene defect (even if the exact gene or gene defect is not yet known). The opposite of a familial disorder is a sporadic disorder: one that occurs randomly, not one that "runs in families."

    Intubation: placement of a tube; refers specifically to the insertion of a plastic tube in someone's trachea and connecting it to a breathing machine (ventilator or respirator).

    Level II ultrasound: a specialized prenatal ultrasound that looks at the fetal anatomy in more detail than a level I ultrasound. A level I ultrasound is a "routine" ultrasound during pregnancy. If there is a suspicion of an anomaly by routine ultrasound, a pregnant woman may be referred for level II ultrasound.

    Lung-head ratio (LHR): a number that indicates the degree of pulmonary hypoplasia of the contralateral lung (i.e., the lung on the opposite side of the diaphragmatic hernia). It is the obtained by dividing the lung area by the head circumference (using head circumference, which is a good measurement of the size and age of the fetus, allows us to use the LHR ratio to describe the size of the lung, regardless of the exact gestational age). An LHR > 1.4 describes very mild pulmonary hypoplasia; conversely, an LHR < 0.7 describes a very small and hypoplastic lung.

    Magnetic resonance imaging (MRI): a type of imaging test that does not use radiation, and provides very detailed images of the inside of the body.

    Morgagni: A less common type of diaphragmatic hernia (and usually less severe form), whereby the hole in the diaphragm is in front, just under the sternum. It is named after the Italian anatomist Giovanni Battista Morgagni (1682-1771).

    Multifactorial: having more than one cause. Pure genetic anomalies are the result of a single gene defect (examples are cystic fibrosis and sickle cell anemia). Environmental conditions are typically caused by something in the environment, such as toxins. Acquired disorders are usually thought not to have a genetic cause. However, many conditions are now understood to be multifactorial: some people with a genetic predisposition may be more susceptible than others to acquire diseases, such as hypertension or congestive heart failure.

    Open fetal surgery: the technique of making a wide (C-section-like) incision in the mother's abdominal wall and uterus, to partially expose and perform an operation on the fetus.

    Prognosis: the predicted outcome of a disease or condition. A prognostic factor or prognostic indicator is a factor that is believed or known to affect the outcome. Examples are early diagnosis, presence of the liver in the chest and a low LHR, all factors that are believed to worsen the outcome in diaphragmatic hernia.

    Pulmonary hypoplasia: impaired growth and development of the lung. It can be caused by a variety of conditions, such as prolonged compression of the fetal lung by a large lesion in the chest or abdominal organs that have migrated through a hole in the diaphragm (CDH).

    Respiratory support: if a patient is having difficulties breathing on his own, respiration may be assisted by placing the patient on a respirator (or ventilator). This breathing machine pumps air into the lungs of the intubated patient, allowing oxygen to enter the lungs and carbon dioxide to be removed. Classically, administering oxygen is called "oxygenation" while removing carbon dioxide is called "ventilation."

    Sternum: the breast bone.

    Surfactant: a liquid that is secreted by the lung cells to coat alveoli. This liquid prevents alveoli from collapsing, thereby making gas exchange easier. Premature infants do not make much surfactant yet, and are therefore at risk of significant lung disease, which leads to "bronchopulmonary dysplasia" or BPD.

    Trachea: the wind-pipe; the upper portion of the airways. It divides into two branches, the left and right main stem bronchus. Each main stem bronchus is the main airway to a lung.

    Tracheal occlusion: a newly developed technique to help the lungs grow before birth. By blocking the trachea, fluid accumulates in the lungs and makes them grow larger. This tracheal occlusion (sometimes referred to as PLUG, or "Plug the Lung Until it Grows") can be performed through open fetal surgery or endoscopically. The latter technique is less invasive, and can be done using an inflatable (and detachable) balloon left inside the trachea. Regardless of the method used, it is important to remove the blockage before the newborn baby can breathe. (Before birth, the lungs of the fetus are not used for breathing, and blocking the trachea will not cause any direct harm to the fetus). It is important to note that this form of treatment before birth is still considered experimental.

    Trisomy 21: Down syndrome, a condition caused by the presence of an extra chromosome 21.

    Sporadic: a condition that does not "run in families," i.e. that is not believed to be related to a gene disorder.

    Ventilatory strategies: there are several ways to improve oxygenation and ventilation of the infant with severe pulmonary hypoplasia. These include:

    • gentle ventilation, often referred to as "gentilation:" because the lungs are small and underdeveloped, using high pressures to pump air into them may in fact damage them - it is better to keep the pressures (and the volume of air) to a minimum.
    • Permissive hypercapnia: instead of trying to remove as much carbon dioxide as possible (by increasing the ventilatory volumes and the degree of assisted ventilation), it is better to minimize the amount of stress on the lungs, even if this allows the level of carbon dioxide to rise a little higher than normal.
    • Nitric oxide is a substance that can sometimes be used to open up blood vessels (capillaries) close to a portion of the lung that is functioning well: Inhaled nitric oxide reaches only those alveoli that are open, not the ones that are collapsed. Therefore, blood (carrying carbon dioxide and oxygen) will only reach these alveoli, and respiration will be more efficient.