Many premature babies suffer from apnea of prematurity. Apnea is defined as a pause in breathing patterns. Whenever parents hear that their baby stops breathing for short periods of time, it is scary for them.
In my article, I will describe the definition of apnea of prematurity, talk about diagnosis, treatment, and prognosis.
If you are interested in reading about other conditions affecting premature babies, you can find more of my articles by clicking on the upper tab labeled “categories” and choosing “preemie babies.”
Definition
Apnea of prematurity is defined as a cessation of breathing in a premature baby for 15-20 seconds or of shorter duration if it is associated with low oxygen levels or low heart rate. Importantly, other causes of apnea than just prematurity should be considered or ruled out first.
Apnea is a common condition in premature babies. 50% of babies born between 33 and 35 weeks of gestational age develop it. The majority of babies born at less than 28 weeks will suffer from apnea and will need treatment for it.
Often, persistent apnea will be the only remaining reason why a baby still needs to be hospitalized in NICU, leading to frustration among family members who would want to have their baby discharged home as soon as possible (Source).
For many micro preemies and extremely premature babies, resolution of apnea is reached only after 43-44 weeks of corrected gestational age (3-4 weeks after pregnancy expected due date).
Why premature babies develop apnea?
Apnea of prematurity is caused by the physiological immaturity of the respiratory center in the brain and anatomical immaturity of upper airways.
The brain respiratory center provides a constant respiratory drive. In mature babies, it can adapt to quickly changing levels of oxygen and carbon dioxide, slowing or increasing respiratory rate whenever needed. In premature babies, this regulatory process may malfunction, leading to so-called “central apnea.” In other words, central apnea occurs when the brain provides inadequate stimulation to muscles responsible for breathing movements.
Patency of upper airways is crucial for air movements during breathing efforts. Many premature babies develop obstructive apnea due to their narrow airways and weak muscles surrounding these airways.
In most situations, babies have mixed apnea, meaning both factors (lack of central stimulation and obstruction of the airways) play the role.
What are the symptoms of apnea of prematurity?
As I said above, apnea is defined as a cessation of breathing for 15-20 seconds or less if it is accompanied by low oxygen levels or low heart rate. Every premature baby who stays in NICU is monitored using cardiorespiratory and pulse oximeter monitors.
The cardiorespiratory monitor allows us to watch and record the baby’s respiratory rate and heart rate. The pulse oximeter measures hemoglobin saturation, which is an indirect indicator of oxygen levels in the baby’s blood.
Even if a nurse is not present all the time at the baby’s bedside, monitors will ring alarms whenever the baby’s vital parameters fall outside of the normal range.
Detecting pauses in breathing effort is relatively easy by watching the baby or reviewing recordings from the monitors. Determining that apneic episodes are due to prematurity requires going through the list of other possible differential diagnoses to rule them out first.
Is it apnea of prematurity, or could it be something else?
Whenever a baby presents to us with apnea, before making the diagnosis of apnea of prematurity, we should consider other options. We need to go over the list of conditions for which apnea may also be a symptom. Let’s look at some of these differential diagnoses below.
Sepsis – generalized infection
Whenever a previously stable baby develops apnea later than one week after birth, one should consider infection as a differential diagnosis. Extremely premature babies and micro-preemies are very prone to infections. Their immune system is undeveloped. They did not receive antibodies from their mothers due to shortened pregnancy, and they are exposed to central lines and ventilators that carry an increased risk of catching an infection.
Babies affected by infection may have other symptoms than apnea as well: low body temperature, exacerbated breathing problems, low blood pressure, low or high sugar levels, and feeding intolerance.
To rule out infection, doctors will order various tests but at minimum blood counts (CBC) and blood cultures (we may also test spinal fluid and urine). If a baby has symptoms that could be caused by infection, we often start antibiotics before the diagnosis is even confirmed.
Anemia
Premature babies often have low levels of red blood cells. Red blood cells carry oxygen to our organs and tissues; therefore, it is crucial to have an adequate amount of them.
Preemies may be born with a low amount of red blood cells, or develop anemia after birth as a result of frequent blood draws and bone marrow not being able to produce red blood cells quickly enough.
It has been described that severe anemia may exacerbate the existing apnea of prematurity or cause apneic events by itself.
Most clinicians would consider blood transfusion in a baby with apnea and significant anemia with a hematocrit of less than 25%. Hematocrit measures the proportion of red blood cells in the blood, and results are reported in “%.” Adults have hematocrit levels around 42%, and full-term babies around 55%.
NEC – Necrotic Enterocolitis
Necrotic Enterocolitis is a severe inflammatory and infectious disease of bowel loops, occurring particularly often in babies born at less than 28 weeks of gestational age. Apnea may be one of the presenting.symptoms. However, almost always, babies will also have severe feeding intolerance with gastric residuals, abdominal distension, and bloody stools.
Necrotic Enterocolitis is treated with antibiotics, IV fluids, and sometimes with surgery.
Intraventricular Hemorrhage (IVH)
Intraventricular Hemorrhage occurs mostly in very premature babies. The rupture of small blood vessels is a cause. Blood enters the ventricles and may compress on vital areas of the brain and later on may lead to hydrocephalus in affected babies.
During the time when a baby is developing IVH or later when a baby suffers from hydrocephalus, the baby may present with significant apneic episodes. Brain imaging with head ultrasound or head cat scan will confirm or rule out the diagnosis of IVH.
Seizure disorder
Babies may develop seizures during the newborn period. In some cases, apneic episodes may be the first or only sign of seizures. To confirm the seizure disorder, doctors will order an electric study of the brain called EEG.
There are many causes of seizures in newborn babies:
- Congenital abnormalities of the brain
- Hypoxia (low oxygen levels affecting the brain)
- Metabolic abnormalities such as low sugar and calcium levels (hypoglycemia, hypocalcemia)
- Intraventricular Hemorrhage
- Brain stroke
- Familial seizure disorders
- Genetic and metabolic disorders
Hypoglycemia – low sugar levels in a baby
Hypoglycemia is a medical term used to describe abnormally low sugar levels (glucose) in our body. It may be accompanied by apnea if sugar levels (glucose levels) are very low.
Hypoglycemia is more common in babies who were born very small (SGA) or very large (LGA) for their gestational age and in babies of mothers who have diabetes.
Neonatal Encephalopathy (Low oxygen levels at and around birth time in a baby)
Prolonged exposure of the baby to low oxygen levels during labor and delivery may lead to brain damage called Neonatal Encephalopathy. Apnea may be one of the symptoms of this condition. It is important to emphasize that neonatal encephalopathy occurs both in preterm and term babies.
Usually, it is easy to diagnose neonatal encephalopathy because babies with this condition will have a history of heart decelerations during labor and very low Apgar scores at birth (explanation of Apgar scores here).
Congenital anomalies of the airways
Various developmental anomalies that affect the patency of the airways may be the cause of apnea. Sometimes airway anomalies are evident during an external examination. However, often ENT specialist is needed to conduct a thorough examination of upper and lower airways in a baby to rule out this diagnosis conclusively.
Symptoms such as noisy breathing or choking episodes while feeding are suggestive of problems with the airways and may require ENT consult.
Feeding problems in premature baby
Oral feeding is a complex task for a baby. It involves three separate actions that need to be coordinated well: sucking, swallowing, and breathing. Many premature babies born at less than 34 weeks of gestational age do not know how to eat by mouth and have to learn that skill. During the learning process, they may have apneic episodes while feeding or right after.
In addition, many premature babies suffer from gastro-esophageal reflux due to physiologically weak esophageal sphincter muscle. As a result, stomach contents can travel back up into the esophagus, mouth, and nose and sometimes can be even aspirated into the lungs.
It is still debatable how much reflux contributes to apnea in premature babies, and if the treatment of reflux helps at all. However, it is plausible that severe reflux may be contributing to the severity of apnea in premature babies. Whether to treat it is another question.
Maternal medications such as opiates and magnesium sulfate
Opiates medications are used for control of labor pains and can be given to the mother. Opiates easily cross the placenta and enter the baby’s circulation before birth. Opioid medications are known to cause apnea in babies.
Magnesium sulfate is used in mothers to control blood pressure or slow down contractions. It causes muscle weakness and sleepiness in babies and may also lead to apnea.
Whenever apnea in a baby is due to maternal medications, it manifests itself soon after birth, and it gets better quickly. It usually resolves within 24-48 hours after delivery once the baby excretes all the medicines out of its system.
How do we treat apnea of prematurity?
Not all apneas of prematurity require treatment. Clinicians usually start treating apnea of prematurity when:
- Apneic episodes are persistent, prolonged and accompanied by oxygen desaturations – measured by pulse oximetry monitors – below 85%
- The baby requires frequent vigorous stimulation or artificial ventilation before restarting its breathing efforts
Once therapy is started, it is usually needed until at least 34 weeks of corrected gestational age, but in micro-preemies, it is not unusual to continue it until 44 weeks.
Doctors treat apnea of prematurity by providing appropriate respiratory support if needed, and medically – using caffeine.
Depending on the severity of premature baby’s lung disease, various types of respiratory support may be needed:
- Nasal cannula
- CPAP device
- Ventilator
Each technique is capable of providing a mixture of air with additional oxygen as needed for the baby. You can learn more details about respiratory support devices from my article here.
Caffeine is a medication that is also found in coffee and tea. We can give it to the baby orally or intravenously. Caffeine keeps us awake, but it also stimulates the baby’s respiration.
Caffeine has been known to us for a long time and is well tolerated by babies. The two most commonly occurring side effects are increased heart rate (tachycardia) and gastroesophageal reflux (Source).
If doctors are concerned about caffeine toxicity, they can measure caffeine levels in the blood, and its dose can be easily adjusted.
In extremely premature babies and micro-preemies, caffeine can be used prophylactically to facilitate the discontinuation of mechanical ventilation or to avoid it altogether.
Prognosis in apnea of prematurity
All premature babies outgrow apnea of prematurity. For some, it happens around 34-35 weeks of gestational age, but in tiniest babies, apnea may persist until 44 weeks of postconceptional age.
If apnea of prematurity does not resolve with time, apneic episodes are likely to be due to other causes than just prematurity.
If you have a premature baby born before 32 weeks receiving treatment in the NICU right now, I encourage you to explore my book “Babies Born Early” You will find a lot of useful information about conditions effecting premature babies, treatments, and discharge criteria.
Disclaimer
This article is only for general information purposes. It should not be viewed as any medical advice. There is a chance that information here may be inaccurate. It would be best if you always discussed all health-related matters with your doctor before making any decisions that may affect your health or health of your family members.