Apnea of prematurity-it’s classification and treatment
Apnea of prematurity is recurrent pauses in respiration. It may be more than 20 seconds or less than 20 seconds. It is also associated with bradycardia, central cyanosis, or oxygen desaturation.
This kind of respiratory problem mainly appears in the premature neonate. Here the prematurity refers to a neonate born at less than 37 weeks of the gestational period and not having any disorders lead to apnea.
What happens in apnea of prematurity?
The apnea is mainly seen in preemies. For which the diagnosis is done immediately after the birth of the baby. Also, it is always recommended before the mother and the baby are discharged from the hospital.
In conditions like AOP( Apnea of prematurity), the part of the nervous system( like the brain and spinal cord) does not develop properly. For which they are unable to provide non-stop breathing to the child.
It may result in large bursts of breath. It is followed by periods of shallow breathing or stopped breathing. AOP may lead to hypoxia, hypercapnia, and disturbances in sleep status. whereas the role of gastroesophageal reflux and anemia is not known clearly.
The relation between bradycardia and AOP?
Apnea of the premature begins from the second day of life. It lasts up to 2 to 3 months after birth. Apnea is somehow normal for all babies. But, it is very complicated in preemies.
The respiratory pauses are mainly responsible for the dropping of the heart rates. It drops 80beats/min. So, they are the key reason behind bradycardia.
AOP causes them to become pale and bluish. And the baby’s look is limp and their breaths are very noisy.
Is AOP similar to periodic breathing?
Although periodic breathing and apnea of premature are very common in a premature newborn, the mechanism of periodic breathing is totally different from AOP.
In the periodic breathing is a pause in normal breathing. it lasts just for a few seconds. and it is followed by several fast and shallow breaths.
Pathophysiology of AOP(Apnea of prematurity)
Enhanced inhibitory reflexes
The inhibitory reflex means the laryngeal chemoreflex. It is mediated through the superior laryngeal afferent nerve.
So, here the activation of laryngeal mucosa can lead to apnea in preemies. Not only AOP but also some conditions like bradycardia and hypotension. This reflex is assumed to be protective but enhanced activation may lead to Apnea of prematurity.
Diminished hypercapnic responses
The decreased hypercapnic responses are mostly seen in the premature infant, having apnea.
During hypercapnia, the ventilation increases, and the period of expiration becomes prolonged. but there is no increase in the breath frequency and tidal volume. Due to a decrease in hypercapnic responses, the baby may suffer from apnea.
Hypoxic ventilatory depression
The delay in declination of spontaneous breathing is termed hypoxic ventilatory depression. It may associate with the delayed postnatal respiratory adjustment that occurs in preemies.
Classification of Apnea in premature infants
Central apnea means a pause in alveolar ventilation. it is due to a lack of diaphragmatic activity. The immature medullary respiratory control center in premature infants is responsible for it.
There is no signal to transmit breath response from CNS to respiratory muscles. the preemies also show an immature response to peripheral vagal stimulation.
Because of the immature response system, apnea may develop in premature infants. for example; the laryngeal receptors responsible for coughing in adults but the same receptors cause AOP.
It refers to the pause in alveolar ventilation which is due to the obstruction of airflow within the upper airway. It takes place particularly at the level of the pharynx.
Here the pharynx collapses because of the negative pressure. This pressure generates during inspiration.
There are two muscles which are genioglossus and geniohyoid. They are helping in keeping the airway open. But, in premature infants both are weak.
Once the pharynx collapses, the mucosa level provides adhesive force it prevents the reopening of the airway during expiration. excessive secretion of the nasopharynx and hypopharynx also cause obstructive apnea. Here the flexion of the neck becomes worse.
It is the combination of both central and obstructive apnea. Here the central apnea is either proceed or followed by airway obstruction.
The causes include;
- Babies having large bursts of breath like shallow breathing or stopped breathing.
- Immature CNS
Other causes included;
- Bleeding in or damage to the brain
- Lung Problem
- Digestive problems such as refluxes
- Too low or too high level of chemicals in the body like glucose and calcium
- Heart or blood vessels problems
- Triggering reflexes like feeding tubes, suctioning, neck position may lead to apnea
- Changes in body temperature
- Errors of metabolism
- Drugs like narcotics, beta-blockers, sedatives, hypnotics, etc.
- Hematological causes
Sign and symptoms of AOP
.Periods of absent breathing for 20 seconds or more
. the symptoms begin right after birth or within two weeks
The the diagnostic evaluation includes;
.arterial blood gas
Others are dependent on history and physical examination.
Treatment of apnea in premature
.maintain airway, breathing, and circulation.
.avoid vigorous suctioning of the oropharynx.
. avoid oral feed for at least 24 hours.
.adjust environmental temperature.
.avoid swings in environmental temperature.
.treatment of the underlying causes like sepsis, anemia, polycythemia, hypoglycemia, hypocalcemia, RDS.
.transfuse packed cell if hematocrit is less than 30%
In specific measures, we should give drugs like amitriptyline, caffeine, doxapram, methylxanthine.
(c) nasal continuous positive airway pressure(CPAP)
.check for bradycardia, cyanosis, and airway obstruction.
.the neck should position in a slight extension manner and suction the oropharynx.
.tactile stimulation should be given.
.provide oxygen therapy to maintain saturation (92-95%) by a headbox or nasal prongs.
.if the neonate does not respond to the tactile stimulation then ventilation should be given by using a bag and mask.
complication of Apnea of prematurity
.spastic diplegia or qudriplegia
. various degrees of mental retardation.