Gastroesophageal reflux and apnea of prematurity: No temporal relationship

Objective. A relationship between gastroesophageal reflux (GER) and apnea of prematurity (AOP) has long been suspected but is difficult to prove because most GER in this age group is nonacidic and thus undetectable by pH monitoring, the current standard for GER detection. The new multiple intraluminal impedance (MII) technique allows pH-independent reflux detection via changes in impedance caused by a liquid bolus inside the esophagus. We used this technique to investigate whether there is a temporal relationship between GER and AOP and whether GER occurs predominantly before a cardiorespiratory (CR) event. Methods. Nineteen infants with AOP (median gestational age at birth: 30 weeks; range: 24-34; age at study: 26 days [13-93]) underwent 20 6-hour recordings of MII, breathing movements, nasal airflow, electrocardiogram, pulse oximeter saturation, and pulse waveforms. MII signals were analyzed, independent of CR signals, for reflux episodes (RE), defined as a fall in impedance in at least the 2 most distal channels. CR signals were analyzed for CR events, ie, apneas of greater than or equal to4-second duration, desaturations to less than or equal to 80%, and falls in heart rate to less than or equal to 100/min. A temporal relationship between an RE and a CR event was considered present if both commenced within 20 seconds of each other. Results. There were 2039 apneas (median: 67; range: 10-346), 188 desaturations (6; 0-25), 44 bradycardias (0; 0-24), and 524 RE (25; 8-62). The frequency of apnea occurring within +/- 20 seconds of an RE was not significantly different from that during reflux-free epochs (0.19/min [0.00-0.85] vs 0.25/min [0.00-1.15]); the same was true for desaturations and bradycardias. Also, RE occurred similarly often within 20 seconds before as after an apnea (2; 0-14 vs 1;0-17). A minority of apneas (3.5%) was associated with an RE reaching the pharyngeal level; of these, significantly more (45 vs 26; median: 1; 0-10 vs 1; 0-7) occurred after rather than before an RE. Conclusion. Both CR events and GER were common in these infants but, with few exceptions, did not seem to be temporally related.