What is the definition of apnea in neonates?

Definition of Apnea in Neonates

In neonates, apnea is defined as a cessation of breathing for at least 20 seconds, or a shorter respiratory pause of at least 10 seconds if associated with bradycardia (<100 beats per minute) or oxygen desaturation (<80%).

Types of Apnea in Neonates

Apnea in neonates can be classified into three main types:

1. Central apnea: Complete cessation of airflow with absence of respiratory effort
2. Obstructive apnea: Absence of airflow despite continued respiratory effort
3. Mixed apnea: Combination of central and obstructive components

Diagnostic Criteria

The American Academy of Sleep Medicine provides specific criteria for scoring respiratory events in neonates 1:

• Apnea Rule for Pediatric Patients:

  • Drop in peak signal excursion by ≥90% of pre-event baseline using appropriate sensors
  • Duration of the ≥90% drop must last at least the minimum duration as specified by obstructive, mixed, or central apnea duration criteria
  • For neonates, the minimum duration is two respiratory cycles (rather than the 10 seconds used in adults)

• Hypopnea Rule for Pediatric Patients:

  • Peak signal excursions drop by ≥30% of pre-events baseline
  • Duration of the ≥30% drop lasts for at least 2 breaths
  • Associated with ≥3% oxygen desaturation or arousal

Clinical Significance and Differentiation from BRUE

It's important to distinguish pathological apnea from Brief Resolved Unexplained Events (BRUE), which replaced the older term "Apparent Life-Threatening Event" (ALTE) 1. BRUE is defined as:

• A sudden, brief (<1 minute, typically <20-30 seconds), and resolved episode
• Including one or more of: cyanosis/pallor, absent/decreased/irregular breathing, marked change in tone, or altered responsiveness
• With no explanation after appropriate history and physical examination
• Occurring in infants <1 year of age

Prevalence and Risk Factors

Apnea of prematurity (AOP) is particularly common:

• Present in >50% of premature infants
• Almost universal in infants <1000g at birth 2
• Frequency decreases with increasing gestational age and postmenstrual age 3

Clinical Implications

Apnea events in neonates can have significant clinical implications:

• May be associated with acute conditions like late-onset sepsis and necrotizing enterocolitis 3
• Can lead to complications including failure to thrive, developmental delay, and cardiovascular morbidity if untreated 4
• May require monitoring and treatment before discharge, as many preterm infants continue to experience short apnea events with bradycardia and desaturation in the week prior to discharge 3

Monitoring Considerations

When monitoring for apnea in neonates:

• Pulse oximetry and abdominal pressure transduction are mainstay monitoring techniques 5
• Laboratory-based polysomnography is the gold standard for diagnosis of obstructive sleep apnea in neonates 4
• Automated detection algorithms can help identify apnea events in continuous monitoring data 3

Common Pitfalls

1. Inconsistent definitions: Current definitions of neonatal apnea appear arbitrary and vary between studies 6
2. Over-reliance on duration: Apnea is likely better defined by associated consequences (bradycardia, desaturation) than by pause duration alone 6
3. Monitor settings: Most infant breathing monitors are set to alert after a respiratory pause >20 seconds, which represents 17 missed breaths in a preterm infant 6
4. Misclassification: Infants referred for apnea monitoring often have infrequent prolonged apnea but more frequent desaturation and bradycardia in response to shorter respiratory pauses 7

Understanding these specific criteria for defining and diagnosing apnea in neonates is crucial for appropriate clinical management and research in this vulnerable population.