Oximetry for preterm infants at neonatal discharge: What is current practice in New Zealand and Australia?

Survey of the practices of neonatologists in managing neonates believed to be at high risk of sleep disordered breathing

OBJECTIVE

To determine the practices of neonatologists in managing high-risk neonates believed to be at risk of sleep disordered breathing (SDB).

DESIGN

An electronic web-based questionnaire assessing awareness of and current practices for managing neonates predisposed to SDB with conditions like craniofacial anomalies, neuromuscular disorders or airway problems was emailed to 232 neonatologists and neonatal fellows working in Australia and New Zealand (NZ). Additionally, neonatologists were approached directly during the annual Australia and NZ perinatal conference in 2019.

RESULTS

93 neonatologists (40%) responded to the survey. The majority (85%) of the respondents stated that there were no written protocols/criteria for sleep consultation in their unit. We found considerable variations in the threshold for performing tests including oximetry or referring for polysomnography. Most respondents would perform oximetry before referring for a sleep consultation. However, the duration of oximetry varied from 6 to 24 hours and there was no consensus about what is considered abnormal on an oximetry study.

CONCLUSION

Management of SDB is gaining importance in neonatal care because of prolonged length of hospital stay and possible long-term effects of SDB. Responses received suggest a lack of clarity regarding thresholds for referral for treatment of SDB. Likely contributory factors are concerns regarding a lack of long-term outcome data from treatment perceived to be onerous for the family, unsettling to some infants and delaying hospital discharge. To overcome inconsistencies in practice, standardised guidelines for assessing and managing SDB in neonates are needed.

Pre-discharge Cardiorespiratory Monitoring in Preterm Infants. the CORE Study

Objective: Ensuring cardiorespiratory (CR) stability is essential for a safe discharge. The aim of this study was to assess the impact of a new pre-discharge protocol named CORE on the risk of hospital readmission (RHR). Methods: Preterm infants admitted in our NICU between 2015 and 2018 were randomly assigned to CORE (exposed) or to standard (not-exposed) discharge protocol. CORE included 24 h-clinical observation, followed by 24 h-instrumental CR monitoring only for high-risk infants. RHR 12 months after discharge and length of stay represent the primary and secondary outcomes, respectively. Results: Three hundred and twenty three preterm infants were enrolled. Exposed infants had a lower RHR (log-rank p < 0.05). The difference was especially marked 3 months after discharge (9.09 vs. 21.6%; p = 0.004). The hospital length of stay in exposed and not-exposed infants was 39(26-58) and 43(26-68) days, respectively (p = 0.16). Conclusions: The CORE protocol could help neonatologists to define the best timing for discharge reducing RHR without lengthening hospital stay.

Comparison of 12-hour and 24-hour oximetry recordings in preterm infants

AIM

To compare the overnight 12-hour oximetry component of 24-hour oximetry recordings with the complete 24-h recording in terms of cardiorespiratory status data in preterm infants.

METHODS

Preterm infants from the Wellington neonatal intensive care unit underwent a 24-h pulse oximetry recording immediately prior to discharge home. Each recording was edited to resemble a 12-h overnight recording and compared to the full 24-h recording. Differences in a range of cardiorespiratory variables were assessed as to whether they were statistically significant and, if so, likely to be clinically significant.

RESULTS

The nadirs for heart rate and SpO₂ (both P < 0.001), the time spent <80% SpO₂ (P = 0.017) and highest heart rate (P < 0.001) were significantly different between the two recordings. Only the heart rate nadir differed by more than 5%, suggesting that this may be of clinical significance (median (interquartile range) 54 (28-69) for 24-h recording vs. 78 (54-96) for 12-h recording).

CONCLUSION

The 24-h oximetry reports were clinically similar to 12-h recordings for the majority of variables, and therefore, we suggest that 12-h oximetry studies are sufficient for determining cardiorespiratory status in infants.

Intermittent hypoxia in preterm infants: Measurement using the desaturation index

OBJECTIVE

The aims of this study were to: (i) Determine in preterm infants at neonatal discharge the prevalence of intermittent hypoxia (IH), as measured by the oxygen desaturation index (DSI) recorded by pulse oximetry and (ii) Determine the change in values for very preterm infants at 1-month post discharge.

METHODS

Preterm infants were recruited from the Wellington regional neonatal intensive care unit (NICU) and 24-h pulse oximetry recordings performed immediately before discharge. Infants born <32 weeks gestational age (GA) had repeat oximetry 1-month post discharge. Oxygenation measures included the 3% and 4% desaturation (DSI 3%, DSI 4%) indices.

RESULTS

At discharge from the neonatal unit the median and interquartile range (IQR) for DSI 4% was 51 (31-74) events per hour with normal mean SpO₂ (median of 97.9% [97.2-98.8 IQR]). Episodes of IH 1 month post discharge decreased with improvements of between 42% and 57% seen for the three DSI measures. Infants <32 weeks GA had higher median DSI 3 and 4% values at discharge but differences when compared with late preterm infants were not significant.

CONCLUSIONS

Preterm infants have frequent episodes of IH as measured by the 3% and 4% DSI when deemed otherwise ready for discharge home. Further research in a larger cohort of very preterm infants and also in term infants is needed to determine the significance of this finding.

24-hour oxygen saturation recordings in preterm infants: editing artefact

AIM

To create editing guidelines for artefact removal in preterm infant pulse oximetry recordings.

METHODS

38 preterm infants ready for discharge home from the neonatal intensive care unit underwent 24-hour pulse oximetry recording using the Masimo^® Rad-8 device. An expert panel determined editing rules based on clinical protocols. For each recording, three reports were generated, 'raw' no editing, 'auto' using the software editing feature and 'manual' reviewed and edited according to the rules. Primary outcome measures were desaturation indices including desaturation index 3% and 4%. Secondary measures included heart rate, mean oxygen saturation and time below 90%.

RESULTS

While all oximetry outcomes differed significantly between editing modes, the majority were not considered likely to influence clinical management. Use of the auto editing compared to no editing did alter by >5%: Time spent <90% oxygen saturation and Desaturation index 4% >10 seconds. The use of manual editing removed extremely low pulse values that were considered unphysiological in this group of otherwise healthy infants.

CONCLUSION

We recommend that oximetry recordings to determine cardiorespiratory stability in newborn infants ready for discharge from the neonatal unit have software editing features applied. This will remove artefact without consuming time in a busy unit.

Preterm infants at discharge: nap polysomnography versus 24-hour oximetry

AIM

This study aimed to determine whether measures of intermittent hypoxia derived from 24-hour oximetry correlate with measures of apnoea derived from modified nap polysomnography undertaken for preterm infants before discharge.

METHODS

Infants born ≤32 weeks of gestation were recruited from the neonatal intensive care unit and had a modified polysomnography to assess their respiratory stability once they were ≥35 weeks of postmenstrual age. Infants were defined as unstable if they had more than 10 obstructive events per hour or any apnoea of >20 seconds in length. Infants also had a 24-hour oximetry performed during this period. The results of the 24-oximetry desaturation index (DSI) were compared to nap polysomnography results for central and obstructive apnoea indices and correlations tested.

RESULTS

Twenty-four infants completed the study. There were 15 (63%) infants defined as unstable by the modified polysomnography. The 3% DSI and 4% DSI from the 24-hour oximetry were significantly higher in the unstable infants, and values for all infants correlated with the obstructive index and the central apnoea index from the modified polysomnography.

CONCLUSION

The 3% DSI and 4% DSI values from a 24-hour oximetry study may provide noninvasive measures of respiratory stability in preterm infants ready for discharge.