Epidemiology and Pathophysiology of Apnoea of Prematurity

Abstract

In preterm infants, reliance on the detection of apnoeic pauses and/or bradycardia results in significant amounts of hypoxaemia remaining undetected. In addition, recordings of breathing movements and ECG do not have predictive value for subsequent sudden infant death. In recent years, the ability to continuously monitor and record arterial oxygen saturation (SaO₂) has produced important information regarding the mechanisms for respiratory events in the preterm population. Normal data on SaO₂ (Nellcor N-200) and breathing movements have been collected in 160 preterm infants. Median baseline SaO₂ during regular breathing was 99.5% (range 88.7-100) at the time of discharge from SCBU and 100% (95.3–100) at follow-up 6 weeks later. Episodic desaturations (SaO₂ < 80% for ≥4s) ranged between 0 and 355 episodes per 12-hour recording. In a study of a separate group of 16 preterm infants with recurrent cyanotic episodes of unknown cause, the total number of abnormal hypoxaemic episodes was markedly increased. These hypoxaemic episodes were associated with three breathing pattern: (i) absent breathing movements; (ii) continued breathing movements, but absent airflow, and (iii) continuous airflow and breathing movements. Thus, preterm infants with cyanotic episodes have an increased number of clinically unapparent hypoxaemic episodes, some of which occur with continued breathing and airflow. In another study of 79 patients who had been born preterm and had a history of an apparent life-threatening event, 43 (54%) had abnormal oxygenation on multichannel recordings, including 23% with clinically undetected baseline hypoxaemia. Continuous additional inspired oxygen was given to 27 patients with recorded abnormalities in oxygenation and a history of recurrent ALTE needing cardiopulmonary resuscitation: in 25, episodes stopped or markedly reduced in frequency. Home PO₂ monitoring has been undertaken in 73 patients for a median duration of 7.1 months. Recognition and treatment of abnormalities in episodic or baseline hypoxaemia may reduce the risk for recurrent cyanotic episodes or subsequent apparent life-threatening events at home. In infants with a history of such episodes, the use of additional inspired oxygen and home PO₂ monitoring are helpful in management. The finding of abnormal hypoxaemia may be relevant to the increased risk of sudden death found in preterm infants.

Blood Transfusion in Anemic Infants with Apnea of Prematurity

“…Moreover, the same magnitude of response was also used as a criterion in other studies on interventions for AOP [22]. We concentrated on bradycardia and hypoxemia rather than on apnea because, from a physiological viewpoint, it is not the apnea that is potentially dangerous to an infant, but its effect on oxygenation or heart rate and, thereby, cerebral perfusion [9]. We combined the two to comply with previous work performed in our institution [14] and because we regard both as equally dangerous.…”

“…Some authors have found less apnea and/or bradycardia following transfusion [1][2][3][4][5]; others have not [6][7][8]. Recently, we studied the effects of blood transfusions on the frequency of bradycardia and desaturation, the clinically most important components of AOP [9], in a group of mildly anemic infants and found that there was no effect on AOP [10]. One potential explanation for this failure to prevent AOP may have been the relatively high hemoglobin level (mean 109 g/l) at which transfusions had been given [10].…”

Neonatal Intermittent Hypoxia Impairs Dopamine Signaling and Executive Functioning

“…[3][4][5][6] Studies confined to single institutions suggest that apnea-induced hypoxia occurs in 78% of infants born between 26 and 27 weeks of gestation. 3,4 As postconceptional age increases, the risk for apnea declines but remains significant; 54% of those born between 30 and 31 weeks, and 7% of those born between 34 and 35 weeks of gestation, demonstrate persistent apneas. 5 Furthermore, a recent multicenter study reports that 11% of neonates born prior to 34 weeks of gestation are discharged to home with an apnea monitor due to a diagnosis of persistent apneas.…”

Mild Intermittent Hypoxia Does Not Induce Stress Responses in the Neonatal Rat Brain

“…Our model of intermittent hypoxia was designed specifi cally to model apnea of prematurity [6,8] , and the fi nding that such a mild stressor evokes lasting changes in brain function is very disturbing in light of the high incidence of apnea among premature babies [1,2] . Our laboratory has demonstrated that the dopaminergic systems of the brain are exquisitely sensitive to intermittent hypoxia [6,8] .…”

“…Repetitive bouts of apnea with concomitant hypoxia occur in up to 54% of infants born between gestational ages of 30 and 31 weeks, and 7% of those born between 34 and 35 weeks after conception [1,2] . Apnea-induced hypoxia is also reported to occur in 2.9-11% of schoolaged children [3,4] .…”