Apnea Of Prematurity (AOP)

 Definition of terms

• Neonate: A newborn, up to 28 days of age (post-birth)
• Apnoea: No respiratory effort for greater than 20 seconds or if the cessation of breathing lasts for > 10 seconds & is accompanied by bradycardia (decrease in heart rate) and or desaturation (decrease in oxygen saturation – visible via a Pulseoximeter or through bluish discoloration of the skin).
• Periodic breathing: Three or more periods with no respiratory effort lasting 3 seconds or more in past 20 seconds. This is a normal neonatal breathing pattern and does not involve changes in heart rate or color.
• Seizures: Apnoea is an uncommon presentation of a neonatal seizure

Introduction

Apnoea is a common occurrence in preterm (<37 weeks of gestation )infants that is often due to idiopathic apnoea of prematurity but may also be due to underlying illness or pain.

In term infants, apnoea is almost always due to a pathological cause yet they may rarely experience apnoea of prematurity as well. 

The variety of causes of apnoea

There are 3 types of apnoea (central, obstructive and mixed), all of which present differently. 

Incidence

The most common cause of apnoea is “Apnoea of prematurity”; the incidence depends on the neonate's gestational age

• >60% when born at 28 weeks or below.
• 50% when born between 30-31 weeks.
• 14% when born between 32-33 weeks.
• 10% when born at 34-35 weeks or above.

Types of Apnoea

• Central apnoea:(40%) Caused by decreased central nervous system stimuli to respiratory muscles. Both the respiratory effort and airflow cease simultaneously (absence of chest wall movement and airflow).
• Obstructive apnoea:(10%) Caused by pharyngeal instability/collapse, neck flexion, or nasal obstruction. Absence of airflow in presence of inspiratory efforts (There is a presence of chest wall movement but no airflow).
• Mixed apnoea:(50%) Has a mixed etiology. Central apnoea is either preceded (usually) or followed by an obstructed respiratory effort

Short episodes of apnoea are usually central whereas prolonged ones are often mixed. Periodic breathing may be mistaken for apnoea. Apnoea may be a symptom of seizure activity. 

Causes

• Apnoea of prematurity: The most common cause of apnoea, is attributable to the immaturity of the respiratory center in the brain. Onset is from days 2-7 of life. Apnoea beginning immediately after birth suggests another cause. Term or near-term babies may rarely experience apnoea of prematurity but a pathological cause should be sought before making this diagnosis in this group.
• Airway obstruction: Assess the position of the head and neck to ensure neutral alignment.
• Infections: Sepsis, necrotizing enterocolitis, meningitis.
• Cardiovascular: Anaemia, hypotension, hypertension, patent ductus arteriosus, cardiac failure, hypovolaemia.
• Pain: Acute and chronic.
• Central nervous system: Intraventricular hemorrhage, seizures, hypoxic injury, neuromuscular disorders, brainstem infarction or anomalies, birth trauma, congenital malformations.
• Respiratory: Pneumonia, intrinsic/extrinsic mass or lesions causing airway obstruction, upper airway collapse, atelectasis, phrenic nerve paralysis, respiratory distress syndrome, pneumothorax, hypoxia, malformations of the chest, pulmonary hemorrhage, aspiration.
• Gastrointestinal: Oral feeding, bowel movement, oesophagitis, intestinal perforation, gastro-oesophageal reflux, abdominal distension.
• Metabolic: Hypoglycaemia, hypocalcemia, hyponatremia, hypernatremia, hyperammonaemia, low organic acids, high ambient temperature, hypothermia, hyperthermia.
• Drugs: Maternal drugs (consider neonatal abstinence syndrome), opiates, prostin, high levels of phenobarbitone, chloral hydrate or other sedatives, general anesthetic.

HOW TO MANAGE 

All neonates less than 34 weeks completed gestation should be routinely monitored with cardio-respiratory and oxygen saturation monitors for at least the first week of life or until apnoeic episodes have been absent for at least 7 days.

• Above 34 weeks completed gestation neonates only need to be monitored if they are unstable: all neonates in the NICU, PICU, and Cardiac Ward at the RCH are monitored for this reason. Continuous cardio-respiratory and pulse oximetry monitoring should occur as per the Observation and Continuous Monitoring guidelines.

Acute management

1. Observe event: Assess. Does the apnoea appear to be obstructive, central, or mixed? Is the apnoea self-limiting or will the infant require intervention?
2. Tactile stimulation: Gentle rubbing of soles of feet or chest is usually all that is required for episodes that are mild and intermittent. 
3. Position airway: Ensure the neonate's head and neck are positioned correctly (neutral position) to maintain a patent airway. Gently suction mouth and nostrils if necessary. Be mindful that deep suction may stimulate a vagal response.
4. Provision of PEEP or positive pressure ventilation: May be required until spontaneous respirations resume. If PEEP or positive pressure ventilation is required to treat apnoeic episodes, CPAP or mechanical ventilation should be considered. 
5. Refer to the" Basic Life support" pathway if the apnoeic episode doesn’t resolve after steps 1-4. 
6. Document event.

“It is important to note that although there are different types of Apnoeas, acute management is always the same”.

Ongoing management

• Pulse oximeter / cardiorespiratory monitor: This allows for observation of heart rate, respiratory rate, and oxygen saturation. As well as monitoring trends and patterns. 
• Identify the cause: If apnoea is not physiologic, investigate to identify the underlying cause and treat it appropriately. Differential diagnoses are outlined above.
• Apnoea monitor: This detects abdominal wall movement and may alarm falsely with normal periodic breathing. It will not detect obstructive apnoea. They are used routinely in some perinatal nurseries but at the RCH only used for home monitoring by parents who have undergone resuscitation training.
• Prone positioning: Has been shown to improve thoracoabdominal synchrony and stabilize the chest wall. Several studies have demonstrated that the prone position reduces apnoea of prematurity.
• Caffeine citrate: From the methylxanthine group of drugs; it can be given orally or intravenously and is usually routinely given to neonates <34 weeks gestation. It acts as a smooth muscle relaxant and a cardiac muscle and central nervous system stimulant.
• High flow nasal cannula (HFNC): As treatment for mixed and obstructive apnoeas. Often used when caffeine has failed.
• Nasal CPAP: As a treatment for mixed and obstructive apnoeas and when caffeine and or HFNC(High Flow Nasal Cannula) have failed.
• Mechanical ventilation: These are used when caffeine and HFNC and CPAP have been tried and there are still significant apnoeas. It is effective in all types of apnoea.

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