Cardiorespiratory Monitoring Can Be Telling of Outcomes in Extremely Preterm Infants

Physiologic data from cardiorespiratory monitoring may provide prognostic information about the clinical outcomes of extremely preterm infants, the Prematurity-Related Ventilatory Control (Pre-Vent) study found.

The endpoint of death or need for respiratory medications or support at 40 weeks postmenstrual age (PMA) was predicted by physiological parameters, the relationship growing stronger as the babies got older, from an area under the curve (AUC) of 0.792 at postnatal day 7 to an AUC of 0.855 at day 28, reported Namasivayam Ambalavanan, MD, of the University of Alabama at Birmingham, and coauthors.

In particular, intermittent hypoxemia with oxygen saturation (SpO₂) below 90% was the physiologic variable that contributed most to the accuracy of predicting these unfavorable outcomes, according to the multicenter, prospective cohort study published in the American Journal of Respiratory and Critical Care Medicine.

Models combining clinical data with physiologic variables had predictive accuracy reach AUC 0.86-0.88 at day 28.

“Our data demonstrate that while clinical variables such as [birth weight], GA [gestational age], and magnitude of respiratory support are strong predictors of respiratory outcome, physiologic data that reflect abnormalities of control of breathing are also associated with poor outcome,” the authors wrote.

“Although there is only incremental improvement in prediction accuracy in combining physiologic and clinical variables, physiologic data alone are independent predictors of unfavorable respiratory outcome,” they asserted.

Difficulty breathing is common in preterm infants and can lead to bradycardia, periodic breathing, intermittent hypoxemia, and bronchopulmonary dysplasia (BPD). BPD is associated with infections, pulmonary hypertension, heart defects, and many other health issues in infants as they grow, as well as an increased mortality risk.

“It is essential to consider the relevance of our results for the field of neonatology. Despite advances in neonatal care and reductions in neonatal mortality and many neonatal morbidities, the rate of BPD in extremely preterm infants has increased in recent years, indicating that additional research on the causes of respiratory morbidity is essential,” Ambalavanan’s group wrote.

Christian F. Poets, MD, of Tübingen Children’s Hospital in Germany, and Leif Nelin, MD, of Nationwide Children’s Hospital in Columbus, Ohio, cautioned that the present findings ultimately still need further investigation.

“What would an ability to predict the above outcomes based on physiologic parameters obtained at 32 weeks PMA mean in terms of clinical utility? With regard to BPD prevention, any therapy started beyond 32 weeks PMA would be unlikely to change a given infant’s risk of developing BPD, since the damage that ultimately leads to this outcome will already have occurred. There would also be minimal impact over the current counseling given to parents of babies born at <29 weeks GA,” the pair wrote in an editorial.

“Alternatively, could the fact that cardiorespiratory events were characteristic of infants subsequently developing an impaired respiratory outcome mean that they already had impaired lung function very early on in their course … rather than reflecting a primary respiratory control disorder? This kind of chicken-and-egg question will be nearly impossible to answer with the currently available data,” they continued.

A total of 717 infants born extremely preterm were included in the study. Participants had a median gestational age of 26.4 weeks, and a median birth weight of 850 g.

Favorable outcomes were defined as the patient staying alive and being discharged, or receiving inpatient care while being off of respiratory medications, O₂, or support at 40 weeks PMA. Unfavorable outcomes were defined as patient death or a discharge while on respiratory medications, O₂, or support at 40 weeks PMA.

Of the infants analyzed, 16% experienced a highly unfavorable outcome, 6% had a moderately unfavorable outcome, and 25% had a mildly unfavorable outcome.

Researchers developed a prediction model for patient outcomes based on infant monitoring data at 7, 14, 28, and 32 weeks PMA, utilizing physiologic data variables, clinical variables, and a combination of the two. Physiological measurements included apnea, intermittent hypoxemia events with SpO₂ less than 90% or 80%, bradycardia, and periodic breathing.

Investigators acknowledged they assessed short-term outcomes up to 40 weeks PMA or discharge, and longer-term respiratory data are pending follow-up evaluation. Additionally, apnea and periodic breathing could not be adequately characterized whenever mechanical ventilation was required.