Apnea Of Prematurity
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Apnea of prematurity is a disorder in infants who are
preterm Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 weeks, very early preterm birth is betwee ...
that is defined as cessation of
breathing Breathing (spiration or ventilation) is the rhythmical process of moving air into ( inhalation) and out of ( exhalation) the lungs to facilitate gas exchange with the internal environment, mostly to flush out carbon dioxide and bring in oxy ...
(
apnea Apnea (also spelled apnoea in British English) is the temporary cessation of breathing. During apnea, there is no movement of the muscles of inhalation, and the volume of the lungs initially remains unchanged. Depending on how blocked the ...
) that lasts for more than 20 seconds and/or is accompanied by hypoxia or
bradycardia Bradycardia, also called bradyarrhythmia, is a resting heart rate under 60 beats per minute (BPM). While bradycardia can result from various pathological processes, it is commonly a physiological response to cardiovascular conditioning or due ...
. Apnea of prematurity is often linked to earlier prematurity (younger gestational age). Apnea is traditionally classified as either ''obstructive'', ''central'', or ''mixed'': *Obstructive apnea may occur when the infant's neck is hyperflexed or conversely, hyperextended. It may also occur due to low pharyngeal muscle tone or to inflammation of the
soft tissue Soft tissue connective tissue, connects and surrounds or supports internal organs and bones, and includes muscle, tendons, ligaments, Adipose tissue, fat, fibrous tissue, Lymphatic vessel, lymph and blood vessels, fasciae, and synovial membranes. ...
s, which can block the flow of air though the
pharynx The pharynx (: pharynges) is the part of the throat behind the human mouth, mouth and nasal cavity, and above the esophagus and trachea (the tubes going down to the stomach and the lungs respectively). It is found in vertebrates and invertebrates ...
and
vocal cords In humans, the vocal cords, also known as vocal folds, are folds of throat tissues that are key in creating sounds through Speech, vocalization. The length of the vocal cords affects the pitch of voice, similar to a violin string. Open when brea ...
. *Central apnea occurs when there is a lack of respiratory effort. This may result from
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...
immaturity, or from the effects of medications or illness. *Mixed apnea involves elements of both obstructive and central apnea. Many episodes of apnea of prematurity may start as either obstructive or central, but then involve elements of both, becoming mixed in nature. Over 50% of infants who are born preterm are estimated to be affected by apnea of prematurity. Infants who are born weighing less than 1000g have close to a 100% risk of being affected by apnea of prematurity. Most premature infants are affected by 'central' apnea due to the developmental stage of their
respiratory tract The respiratory tract is the subdivision of the respiratory system involved with the process of conducting air to the alveoli for the purposes of gas exchange in mammals. The respiratory tract is lined with respiratory epithelium as respirato ...
. Apnea of prematurity can increase the risk of chronic health conditions including
retinopathy Retinopathy is any damage to the retina of the eyes, which may cause vision impairment. Retinopathy often refers to retinal vascular disease, or damage to the retina caused by abnormal blood flow. Age-related macular degeneration is technically in ...
and increases the risk of problems with the infant's neurological development. Apnea lasting more than 60 seconds may result in death or disability. The main treatment for apnea of prematurity has been pharmaceutical treatment with methylxanthines that have a mechanism of action of bronchodilation and a stimulant of the respiratory system to promote spontaneous breathing.
Caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class and is the most commonly consumed Psychoactive drug, psychoactive substance globally. It is mainly used for its eugeroic (wakefulness pr ...
,
theophylline Theophylline, also known as 1,3-dimethylxanthine, is a drug that inhibits phosphodiesterase and blocks adenosine receptors. It is used to treat chronic obstructive pulmonary disease (COPD) and asthma. Its pharmacology is similar to other met ...
, and minophylline are the common medications used.


Pathophysiology

Ventilatory drive is primarily dependent on response to increased levels of
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
(CO2) and acid in the blood. A secondary stimulus is hypoxia. Responses to these stimuli are impaired in premature infants due to immaturity of specialized regions of the brain that sense these changes. In addition, premature infants have an exaggerated response to laryngeal stimulation (a normal reflex that closes the airway as a protective measure).


Diagnosis

Apnea of prematurity can be readily identified from other forms of infant apnea such as obstructive apnea, hypoventilation syndromes, breathing regulation issues during feeding, and reflux associated apnea with an infant pneumogram or infant apnea/sleep study. It has been reported that the incidence of neonatal apnea happens in almost all infants with gestational age of less than 29 weeks or the birth weight of less than 1000g.Robertson CM, Watt MJ, Dinu IA. Outcomes for the extremelypremature infant: what is new? And where are we going. Pediatr Neurol2009;40:189–96.


Treatment


Medications

Methylxanthines (
theophylline Theophylline, also known as 1,3-dimethylxanthine, is a drug that inhibits phosphodiesterase and blocks adenosine receptors. It is used to treat chronic obstructive pulmonary disease (COPD) and asthma. Its pharmacology is similar to other met ...
and
caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine chemical classification, class and is the most commonly consumed Psychoactive drug, psychoactive substance globally. It is mainly used for its eugeroic (wakefulness pr ...
) have been used for almost three decades to treat apnea of prematurity. These medications are thought to help by stimulating the preterm infant's respiratory drive, increasing activity of the diaphragm muscles, and by bronchodilation. There is some evidence that these medications can reduce to need for mechanical ventilation in preterm infants. There is no clear evidence to determine which type of methylxanthine formulation is more effective for preterm infants. The long term effects of this treatment approach has not been well studied. There is also not a lot of evidence to support the most effective way to treat very young preterm infants such as those who are born earlier than 28 weeks of gestational age.


Respiratory support

Simple tactile stimulation by touching the skin or patting the infant may stop an apneic episode by raising the infant's level of alertness. Increasing the environmental oxygen level by placing the infant in a tent or hood with supplemental oxygen can diminish the frequency of AOP, and may also help the infant maintain adequate oxygenation during short episodes of apnea. Increased oxygen at low levels can also be delivered using a
nasal cannula The nasal cannula (NC) is a device used to deliver supplemental oxygen or increased airflow to a patient or person in need of respiratory help. This device consists of a lightweight tube which on one end splits into two prongs which are place ...
, which additionally may provide some stimulation due to the tactile stimulation of the cannula. CPAP (continuous positive airway pressure) is sometimes used for apnea when medications and supplemental oxygen are not sufficient. Usually as a last resort,
mechanical ventilation Mechanical ventilation or assisted ventilation is the Medicine, medical term for using a ventilator, ventilator machine to fully or partially provide artificial ventilation. Mechanical ventilation helps move air into and out of the lungs, wit ...
is used to support infants whose apnea cannot be controlled sufficiently by other methods and where the potential risk of harm from recurrent hypoxia is felt to outweigh the risks of injury from ventilation.


Monitoring

In-hospital monitors in the NICU typically measure respiratory movements, heartrate, and
pulse oximetry Pulse oximetry is a noninvasive method for monitoring blood oxygen saturation. Peripheral oxygen saturation (SpO2) readings are typically within 2% accuracy (within 4% accuracy in 95% of cases) of the more accurate (and invasive) reading of art ...
. Central apnea can be detected quickly since it results in absence of respiratory movements. Obstructive apnea can be detected when the level of oxygen has declined in the blood and/or results in slowing of the heart rate. Home apnea monitors (which must be distinguished from infant monitors that are designed only to allow parents to listen to the infant remotely) most frequently measure only respiratory movements and/or heart rate. They are generally used with premature infants who are otherwise ready for discharge, but who continue to require supplemental oxygen or medication for mild residual AOP. Home apnea monitoring is typically required for 6–12 weeks after discharge.


Outcome

Since AOP is fundamentally a problem of the immaturity of the physiological systems of the premature infant, it is a self-limited condition that will resolve when these systems mature. It is unusual for an infant to continue to have significant problems with AOP beyond 43 weeks post-conceptual age. Infants who have had AOP are at increased risk of recurrence of apnea in response to exposure to anesthetic agents, at least until around 52 weeks post-conceptual age. There is no evidence that a history of AOP places an infant at increased risk for
SIDS Sudden infant death syndrome (SIDS), sometimes known as cot death or crib death, is the sudden unexplained death of a child of less than one year of age. Diagnosis requires that the death remain unexplained even after a thorough autopsy and ...
. However, any premature infant (regardless of whether they have had AOP) is at increased risk of SIDS. It is important that other factors related to SIDS risk be avoided (exposure to smoking, prone sleeping, excess bedding materials, etc.)


Epidemiology

Apnea of prematurity occurs in at least 85 percent of infants who are born at less than 34 weeks of gestation. The incidence is inversely related to the gestational maturity of the infant, but has considerable individual variability.


References


External links

{{Respiratory system symptoms and signs Breathing abnormalities Preterm birth