Clinical associations of immature breathing in preterm infants: part 1-central apnea

Abstract

Background: Apnea of prematurity (AOP) is nearly universal among very preterm infants, but neither the apnea burden nor its clinical associations have been systematically studied in a large consecutive cohort.

Methods: We analyzed continuous bedside monitor chest impedance and electrocardiographic waveforms and oxygen saturation data collected on all neonatal intensive care unit (NICU) patients <35 wk gestation from 2009 to 2014 (n = 1,211; >50 infant-years of data). Apneas, with bradycardia and desaturation (ABDs), defined as central apnea ≥10 s associated with both bradycardia <100 bpm and oxygen desaturation <80%, were identified using a validated automated algorithm.

Results: Number and duration of apnea events decreased with increasing gestational age (GA) and postmenstrual age (PMA). ABDs were more frequent in infants <31 wk GA at birth but were not more frequent in those with severe retinopathy of prematurity (ROP), bronchopulmonary dysplasia (BPD), or severe intraventricular hemorrhage (IVH) after accounting for GA. In the day before diagnosis of late-onset septicemia and necrotizing enterocolitis, ABD events were increased in some infants. Many infants continued to experience short ABD events in the week prior to discharge home.

Conclusion: Frequency of apnea events is a function of GA and PMA in infants born preterm, and increased apnea is associated with acute but not with chronic pathologic conditions.

Figure 1. Respiratory support

Type of respiratory support over the course of the NICU stay is shown for all 1268 infants <35 weeks’ GA with bedside monitor data available for analysis. Number of infants in each GA week group is shown on the right y axis, and the change in color represents mode of respiratory support with advancing postmenstrual age: ventilator (black), nasal continuous positive airway pressure (CPAP, green), nasal cannula (NC, yellow), and room air (blue).

Figure 2. Apnea, bradycardia, desaturation example and incidence

Apnea at least 10 seconds with associated bradycardia <100 beats/minute and oxygen desaturation <80% were analyzed using a published algorithm(17) A) Graphic representation of 60 seconds of vital sign and waveform data showing a representative ABD event. From top to bottom: Heart rate (HR with 100 beats per minute threshold of bradycardia indicated by the thin green line), oxygen saturation (SpO₂ with 80% threshold of desaturation indicated by the thin blue line), chest impedance (CI), filtered chest impedance (FCI), and computer algorithm-detected probability of apnea (P_A). An “ABD10” event is shown, with apnea duration >10 seconds and associated bradycardia and oxygen desaturation. Another shorter breathing pause occurred without associated bradycardia, which did not meet our definition of an “ABD” event. B) ABDs were analyzed on all infants all times that bedside monitor data were available and the infant was not on mechanical ventilation. Number of infants of each gestational age with at least one algorithm-detected ABD10 event (black fill) and with no events detected (white) is shown.

Figure 3. Mean number of ABD events per day based on gestational and postmenstrual age

For 1211 infants <35 weeks’ GA, ABDs were analyzed during all times that data were available and infants were not on mechanical ventilation. A) Heat map of mean daily #ABD10s (apnea at least 10 seconds with associated bradycardia and desaturation) for each week of GA and PMA. Color scale goes from blue (zero) to red (eight) events per day. The line graph below showsmean daily #ABD10s for infants <27 weeks GA (blue), 27–30 weeks (green), and 31–34 weeks (red). B) Mean daily #ABD20s (apnea at least 20 seconds with bradycardia and desaturation) for each week of GA and PMA.