Cardiorespiratory Events in Preterm Infants Referred for Apnea Monitoring Studies

Abstract

Background. Episodes of apnea, desaturation, and bradycardia are common in preterm infants. Such infants who have persistent cardiorespiratory events detected by clinical bedside monitoring often are referred for overnight apnea monitoring studies. Objective. To characterize apnea, bradycardia, and desaturation events in infants referred for an overnight apnea monitoring study and compare them with corresponding events in control infants of similar age and weight with no bedside monitor alarms. Methods. Twelve-hour bedside apnea monitoring studies were performed on 68 preterm infants before hospital discharge. This population included 35 infants who were referred by their attending physicians because of persistent bedside monitor alarms (referral group) and 33 infants who had no documented cardiorespiratory events for at least 2 days before the study (control group). Each study monitored respiration via respiratory inductance plethysmography, oxygen saturation (Sao2), and heart rate. Events were defined as meeting 1 of the following criteria: apnea ≥20 seconds, bradycardia ≤80 beats per minute, or Sao2 ≤80%. Results. The incidence of apnea ≥20 seconds was low, with no significant difference between infant groups. Referral infants exhibited a higher occurrence of desaturation episodes (20 ± 6 vs 6 ± 3 episodes/12-hour study) and a higher occurrence of bradycardia episodes (4.3 ± 0.8 vs 1.1 ± 0.3 episodes/12-hour study) than controls. These episodes of desaturation and bradycardia were always preceded by a respiratory pause, which was shorter in the referral infants (10.0 ± 0.4 seconds vs 12.0 ± 1.0 seconds). Baseline Sao2 was lower in referrals than controls (95 ± 1% vs 98 ± 1%), and the incidence of periodic breathing was significantly higher. Conclusions. Infants referred for apnea monitoring studies because of persistent bedside monitor alarms have very infrequent prolonged apnea but a higher frequency of desaturation and bradycardia in response to short respiratory pauses than infants without persistent bedside monitor alarms. Referral infants also exhibit a lower baseline Sao2. These abnormalities in oxygenation and cardiorespiratory control may be markers for subtle residual lung disease or functional central nervous system abnormalities.