4.3 Apnea of Prematurity

Apnea of Prematurity

Quick Answer: Apnea of prematurity (AOP) is a pause in breathing of 20 seconds or longer, or a shorter pause with bradycardia or oxygen desaturation, in a preterm infant whose brainstem and upper airway are immature. Events are central (no effort), obstructive (effort, no flow), or mixed (both—the usual preterm pattern). Caffeine citrate, tactile stimulation, and CPAP are the core treatments. New clusters of apnea are sepsis, anemia, GER, and thermal or airway problems until proven otherwise. NRP secondary apnea is a delivery-room asphyxia state that needs PPV; it is not AOP on day 10.

Apnea of prematurity is its own leaf on the current Neonatal CCRN Test Plan (Respiratory, 15% domain). This OpenExamPrep section is independent teaching. It does not claim AACN endorsement. Discharge home on a monitor, the car-seat challenge, and safe-sleep teaching overlap with later continuum and safety content; this section names the overlap so you do not treat AOP as finished when the infant is still 33 weeks postmenstrual age in an open crib.

Definition you can quote on an item

AOP is not every pause. Periodic breathing—clusters of short pauses lasting a few seconds without bradycardia or desaturation—is common in preterms and is not the same diagnosis. The operational definition used at the bedside and on this exam is:

• Cessation of breathing for ≥20 seconds, or
• A shorter pause that comes with bradycardia (many alarms use <80–100 beats/min—know your unit number) or desaturation (a drop below the target band, often into the 70s–80s on the tracing)

Document the duration, the lowest heart rate, the lowest SpO2, whether stimulation or PPV was required, and the infant's position. A 12-second pause to SpO2 68% and heart rate 62 that needed a bag is more serious than a 22-second pause that self-resolved at SpO2 88%. The 20-second rule does not give the self-resolved event a free pass if the infant is otherwise crashing.

Incidence falls as postmenstrual age (PMA) rises. Almost all infants born before 28 weeks have events. Many infants born at 28–32 weeks do too. AOP often quiets by 34–36 weeks PMA in infants who were not extremely preterm; infants born before 28 weeks may still have events approaching 40 weeks PMA. That calendar is why a 26-week infant at 35 weeks PMA can still be caffeine-dependent while a 34-week infant at the same PMA is feeding in a crib.

Central, obstructive, and mixed

Central apnea is a pause in respiratory effort. Chest impedance is flat. The immature brainstem has a blunted response to CO2 and a tendency to pause, especially in active sleep. Hypoxia itself can depress (not stimulate) the preterm respiratory drive—the opposite of a healthy adult's hypoxic ventilatory response.

Obstructive apnea is effort without airflow. The chest moves; the airway is closed at the pharynx, from neck flexion, secretions, a malpositioned CPAP prong, or hypotonia. Impedance monitors can miss obstruction because the chest still moves. The pulse oximeter and the nurse's eyes catch it.

Mixed apnea starts with a central pause and then obstructive breaths against a closed airway, or the reverse. Mixed events are the most common pattern in preterms. That is why caffeine (drive) plus CPAP (splint) is a physiologic pair, not two random orders.

A 24-week infant whose neck is flexed in a nest, with gasping chest pulls and no breath sounds, is obstructing. Extend the neck to sniffing, check the prongs, and do not answer with a second caffeine load as the only thought. A 30-week infant in quiet sleep with a 25-second flat tracing, no obstruction, and a drop to heart rate 70 is a central event—stimulate, then look at the caffeine level and the sepsis workup if the pattern is new.

Why preterms pause: the physiology, not the vibe

The preterm brainstem has fewer dendritic connections, a blunted CO2 response curve, and unstable sleep-state control. The chest wall is so compliant that FRC collapses between breaths, and hypoxemia then deepens the next pause. Upper-airway dilator muscles (genioglossus) are hypotonic. Anemia reduces oxygen carrying so each pause desaturates faster. Infection adds cytokines and a higher metabolic rate. Gastroesophageal reflux can temporally associate with some events; it is a contributor to sort, not the explanation for every AOP diagnosis, and fundoplication is not first-line AOP therapy.

Thermal swings matter. An overheated incubator and a cold stress both destabilize. Keep the infant in a thermoneutral range (36.5–37.5 °C axillary or abdominal skin per unit device). After a bath or a scale weigh, expect a cluster and do not call it unexplained until you have restored temperature.

Caffeine citrate: the medication you will be asked to dose conceptually

Caffeine citrate is a methylxanthine adenosine-receptor antagonist that increases minute ventilation, CO2 sensitivity, and diaphragmatic function. It is standard for infants at high AOP risk (commonly under 29–32 weeks, follow your unit start rule) and for infants who already have events.

Typical dosing (citrate salt, the usual NICU label):

• Loading dose about 20 mg/kg IV or enteric
• Maintenance about 5–10 mg/kg/day (once daily is common; some units divide)

Caffeine base is half of the citrate milligram number (20 mg/kg citrate ≈ 10 mg/kg base). Order-entry errors happen when a base protocol is applied to a citrate product. Confirm the salt on the syringe.

The Caffeine for Apnea of Prematurity (CAP) trial associated caffeine with less bronchopulmonary dysplasia, less treatment for PDA, and better survival without neurodevelopmental disability at 18–21 months. That evidence is why caffeine is not merely an alarm-silencer. Side effects: tachycardia, jitteriness, feeding intolerance, GER, and, in overdose, vomiting and seizures. A heart rate that jumps from 150 to 195 after a load is expected-range methylxanthine effect until it is not; a heart rate of 220 with emesis is toxicity until the level and the dose are reviewed.

Theophylline is an older methylxanthine with a narrower window and more tachycardia and GI toxicity. Caffeine is preferred in contemporary NICUs. Do not answer an AOP item with theophylline as first-line without a unit-specific reason.

Weaning: many teams continue caffeine until the infant has a defined apnea-free interval (often 5–7 days of no significant events) and a PMA often in the 33–35 week range, longer if born extremely preterm. Stopping caffeine and then discharging 24 hours later is a trap. Watch through at least the unit's observation window after the last dose (caffeine's half-life in preterms can be days).

Stimulation, CPAP, and when you bag

Tactile stimulation—rubbing the sole of the foot, a gentle tap, or a reposition—restarts many events. If the heart rate is still falling or there is no chest rise, PPV is required. Standing at the bedside counting to 20 while the heart rate is 50 is not watchful waiting; it is delayed NRP inside the NICU.

Nasal CPAP (or NIPPV) reduces mixed and obstructive events by stenting the pharynx and defending FRC so the next breath starts from a better volume. HFNC is used as a step-down in some units; it is not automatically equal to CPAP for a 25-week infant with mixed apnea and a hazy film.

Prone or side positioning can reduce events in a monitored NICU infant. That is not a discharge safe-sleep instruction. When the infant is in an open crib approaching home, supine safe sleep is the teaching—document monitored exceptions while respiratory support is still required. Do not export NICU prone-for-apnea into the family's crib without the monitor and the context.

Reversible contributors: do not call every cluster AOP

AOP is a diagnosis of an immature infant, but new or worsening events are a workup:

• Infection (late-onset sepsis, NEC, meningitis, RSV later in the stay). A 12-day-old 27-week infant who was event-free on caffeine and now has a cluster, thermal instability, and a rising lactate is sepsis until cultures and a clinical exam say otherwise. Chapter 14 owns the full sepsis pathway; this section owns the apnea clue.
• Anemia of prematurity. A hemoglobin that has drifted to 7–8 g/dL with a high oxygen extraction can turn brief pauses into deep desaturations. Transfusion decisions are unit- and trial-protocol based; the nursing action is to put anemia on the list, not to ignore a hematocrit of 22% because caffeine is on the eMAR.
• GER and aspiration. Temporal association is not always causation. Position after feeds, evaluate the nasogastric tube, and do not leap to fundoplication as AOP therapy. Milk in the airway is also aspiration, a different test-plan leaf.
• Airway and equipment. Kinked CPAP, secretions, vocal-cord edema after extubation, choanal issues, and a neck rolled into flexion.
• Neurologic events. Seizures and IVH can declare as pauses. If the tracing looks rhythmic or the infant is deeply encephalopathic, that is not ordinary AOP (neurology chapters).
• Metabolic and thermal. Hypoglycemia, electrolyte swings, and incubator overheating.
• Drugs. Maternal magnesium in the first hours, prostaglandin infusions (apnea is the signature PGE1 effect from chapter 2), and sedatives.

NRP secondary apnea versus AOP

Hold the two phrases in different rooms of your brain.

Secondary apnea (section 4.1): perinatal asphyxia sequence, minutes of life, stimulation fails, PPV is mandatory, heart rate often <60–100. The treatment is NRP, not a caffeine load.

AOP: days to weeks of life, immature preterm, caffeine already in play or about to be, stimulation often works, workup for reversible causes when the pattern changes.

An item that says a 4-minute-old term infant is apneic after shoulder dystocia is not asking for caffeine citrate 20 mg/kg. An item that says a 29-week infant on day 9 has mixed events on CPAP is not asking you to declare secondary apnea.

Discharge, monitors, and the car-seat overlap (without stealing chapter 16)

Home oxygen, an apnea monitor, and the infant car-seat challenge for infants born at less than 37 weeks sit in later continuum, transport, and safety teaching. What you must not miss here:

• Many units require a documented apnea-free interval off caffeine (or after the last significant event) before discharge—often on the order of 5–8 days, longer after a last caffeine dose because of the long half-life.
• A car-seat challenge looks for desaturation, apnea, or bradycardia in the semi-upright seat. Failure means the infant is not ready for that position for the ride home; it does not by itself diagnose a new central-nervous-system disease, and it does not replace the apnea-free interval.
• Safe sleep at home is supine, firm surface, no loose bedding. NICU positioning for AOP on a monitor is a different rule set.

If a stem asks for the complete discharge bundle, growth, hearing, and ROP, that work lives later in the guide. If it asks why a 35-week PMA former 27-week infant is still in the hospital with a caffeine wean, the answer can still be AOP.

Worked examples and exam traps

Example A. A 26-week infant, day 6, on caffeine maintenance 8 mg/kg/day and CPAP 5. A 18-second pause, heart rate 72, SpO2 76%, responds to a foot rub. Mixed tracing. This is AOP on treatment. Continue caffeine and CPAP; no PPV was required this time.

Example B. The same infant on day 14, previously quiet, now has six PPV events in four hours, a temperature of 36.1 °C, and a glucose of 38 mg/dL. This is not ordinary AOP. Warm, treat hypoglycemia, and start the late-onset infection pathway.

Example C. A 3.6 kg term infant at 8 minutes of life, apneic after a placental abruption, heart rate 40, no response to drying. Secondary apnea—PPV now. Caffeine is the wrong drug class.

Exam traps: treating a 10-second pause without desaturation as AOP that must be medicated; missing obstruction because the impedance tracing still wiggles; using theophylline as default; calling NRP secondary apnea AOP; skipping a sepsis evaluation on a new day-12 cluster; teaching families to prone at home because prone reduced events in the NICU; describing this OpenExamPrep chapter as official AACN training. Independent mixed-item practice is at /practice/ccrn-neonatal.