Apnoea

Question 1

Definition of serious apnoea

Answer 1

1. Cessation of breathing for >20 seconds OR for any duration if associated with cyanosis or bradycardia
2. Bradycardia follows apnoea by 1-2 seconds in >95% cases and is most often sinus, but occasionally could be nodal
3. Vagal responses and rarely heart block are causes of bradycardia without apnoea

Question 2

Definition of short apnoea

Answer 2

10 seconds - rarely associated with bradycardia

Question 3

Definition of periodic breathing

Answer 3

1. alternating breaths and brief respiratory pauses
   
   1. Usually defined as repetitive cycles of breathing and respiratory pauses 5-10 seconds in duration
   2. May be accompanied by oxygen desaturation and bradycardia not requiring intervention
   3. Common in preterm infants

Question 4

Pathogenesis

Answer 4

1. Gestational age is the most important determinant of respiratory age – frequency of apnoea inversely related to gestational age
2. Immaturity of brainstem centers is manifested by an attenuated response to CO2 and a paradoxical response to hypoxia that results in apnoea rather than hyperventilation – observed for first few months of life

Question 5

Classification

Answer 5

1. Idiopathic apnoea of prematurity = occurs in the absence of identified predisposing factors
   
   1. Mixed apnoea – with obstructive apnoea preceding (usually) or following central apnoea
2. Obstructive apnoea = absence of airflow but persistent chest wall movement; inspiratory efforts persist
3. Central apnoeas = decreased CNS stimuli to respiratory muscles; inspiratory efforts absent
4. Short episodes of apnoea are usually central, whereas prolonged ones are often mixed
5. Apnoea depends on sleep state; frequent during active (REM) sleep

Question 6

Aetiology

Answer 6

Question 7

Clinical manifestations

Answer 7

1. Apnoea may become evident in first 2-3 days after birth in preterm infants who are breathing spontaneously
2. Infants born >28 weeks = resolves before 37 weeks PMA
3. Infants born <28 weeks = frequently persists until term PMA
4. Significant apnoea does not typically persist beyond 43 weeks PMA

Question 8

Treatment

Answer 8

1. Cardiorespiratory monitoring
2. Gentile tactile stimulation
3. Treat underlying cause eg. anaemia
4. Nasal CPAP
5. In the absence of significant events home monitoring can be safely discontinued after 44 weeks post-conceptional age
6. Pharmacotherapy = methylxanthines
   
   1. Caffeine = fewer side effects (less tachycardia + feed intolerance), longer half-life, enteral absorption more reliable, no monitoring required unless signs of toxicity
   2. Theophylline = shorter half-life, narrow therapeutic window, requires monitoring, needs to be given more frequently

Question 9

methylxanthines

Answer 9

1. Indication
   
   1. Infants with apnoea of prematurity who require repeated tactile stimulation or ventilatory support
   2. ELBW infants (<1000g) prophylactic caffeine – apnoea occurs in nearly all infants
2. Mechanism = increase central respiratory drive by lowering the threshold of response to hypercapnia as well as enhancing contractility of the diaphragm and preventing diaphragmatic fatigue
3. Dose = loading 20 mg/kg followed by daily maintenance
4. Can start weaning 32 weeks, can stop 34weeks
5. Short-term
   
   1. ↓ assisted ventilation
   2. ↓ chronic lung disease
   3. ↓ PDA ligation
   4. ↓ severe ROP
6. Long-term
   
   1. ↑ disability free survival
   2. ↓ CP
   3. ↓ cognitive delay

Question 10

Prognosis

Answer 10

1. Withholding respiratory stimulants in infants with RDS may result in ventilatory dependency, increased BPD and death
2. Apnoea of prematurity does not alter infant’s prognosis unless severe, recurrent or refractory to therapy
3. Associated problems of IVH, BPD and ROP are critical in determining prognosis
4. Usually resolves by 37 weeks post-conceptional age – although may persistent beyond term particularly if extremely prelature
5. Does NOT predict future episodes of SIDS