Apnea of prematurity
Encyclopedia
Apnea of prematurity is defined as cessation of breathing by a premature
infant that lasts for more than 15 seconds and/or is accompanied by hypoxia
or bradycardia
. 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 tissues, which can block the flow of air though the pharynx and vocal cords. Central apnea occurs when there is a lack of respiratory effort. This may result from central nervous system immaturity, or from the effects of medications or illness. Many episodes of apnea of prematurity may start as either obstructive or central, but then involve elements of both, becoming mixed in nature.
(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).
, 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
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.
. 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.
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
. 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.)
Premature birth
In humans preterm birth refers to the birth of a baby of less than 37 weeks gestational age. The cause for preterm birth is in many situations elusive and unknown; many factors appear to be associated with the development of preterm birth, making the reduction of preterm birth a challenging...
infant that lasts for more than 15 seconds and/or is accompanied by hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
or bradycardia
Bradycardia
Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
. 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 tissues, which can block the flow of air though the pharynx and vocal cords. Central apnea occurs when there is a lack of respiratory effort. This may result from central nervous system immaturity, or from the effects of medications or illness. Many episodes of apnea of prematurity may start as either obstructive or central, but then involve elements of both, becoming mixed in nature.
Incidence
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.Pathophysiology
Ventilatory drive is primarily dependent on response to increased levels of carbon dioxideCarbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
(CO2) and acid in the blood. A secondary stimulus is hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
. 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).
Identification/Testing
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.Medications
Methylxanthines (theophylline and caffeine) have been used for almost three decades to treat apnea of prematurity.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 of 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 cannulaNasal cannula
The nasal cannula is a device used to deliver supplemental oxygen or airflow to a patient or person in need of respiratory help. This device consists of a plastic tube which fits behind the ears, and a set of two prongs which are placed in the nostrils. Oxygen flows from these prongs...
, which additionally may provide some stimulation due to the tactile stimulation of the cannula. CPAP
CPAP
CPAP may stand for:* Continuous positive airway pressure, a particular type of ventilation therapy* The Center for Public Administration and Policy, an academic department at Virginia Tech...
(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
In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...
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 oximetryPulse oximetry
Pulse oximetry is a non-invasive method allowing the monitoring of the oxygenation of a patient's hemoglobin.A sensor is placed on a thin part of the patient's body, usually a fingertip or earlobe, or in the case of an infant, across a foot....
. 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 42 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
Sudden infant death syndrome is marked by the sudden death of an infant that is unexpected by medical history, and remains unexplained after a thorough forensic autopsy and a detailed death scene investigation. An infant is at the highest risk for SIDS during sleep, which is why it is sometimes...
. 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.)
External links
- Information about apnea of prematurity - The Hospital for Sick Children
- Information about Infant Apnea or near-miss SIDS testing - Apnea Research