Abstract
Prior to discharge from the neonatal unit it is clinically important to determine that an infant is stable from a respiratory perspective. Current practice is to monitor an infant using an apnoea monitor measuring breathing movement alone, with the assumption that the absence of alarms from the monitor demonstrates respiratory stability. The purpose of this study was to determine whether 24-hour oximetry provides a more sensitive and specific measurement of respiratory instability than an apnoea monitor measuring breathing movements alone in preterm infants prior to discharge.
We recruited infants from the Wellington Neonatal Intensive Care Unit who were born ≤32 weeks gestation, and performed a modified polysomnography to assess their respiratory stability once they were ≥35 weeks postmenstrual age. Infants were defined as unstable if they had more than 10 obstructive events per hour or any apnoea of greater than 20 seconds in length. We then compared the performance of a 24-hour oximetry and an apnoea monitor measuring breathing movement alone at detecting the unstable infants.
We found that 24-hour oximetry had a higher sensitivity and likelihood ratio than an apnoea monitor set to alarm at 20 seconds of no breath detected, at identifying the unstable infants. We demonstrated that the 24-hour oximetry test was significantly better than the apnoea monitor by area under the curve analysis (0.756 versus 0.533, p=0.02). We also found that despite no medical concerns about many of our participants, a high proportion of them were identified as unstable by the modified polysomnography.
We conclude that an apnoea monitor measuring breathing movement alone is inadequate at detecting those infants who are unstable from a respiratory point of view. We propose that 24-hour oximetry is more appropriate in assessing respiratory stability in preterm infants prior to discharge home, and should be routinely applied even in the absence of clinical concerns regarding respiratory instability.