310 - Tachycardia-Desaturation Episodes: Toward a new cardiorespiratory stress metric in the NICU

Poster Number: 310
Publication Number: 310.441

Karen D. Fairchild, University of Virginia School of Medicine, Charlottesville, VA, United States; VP Nagraj, University of Virginia School of Medicine, Charlottesville, VA, United States; Hannah B. Kearns, University of Virginia School of Medicine, Charlottesville, VA, United States; Brynne Sullivan, University of Virginia School of Medicine, KESWICK, VA, United States

Background: Much attention has been paid to bradycardia-desaturation episodes (BDs) in the Neonatal Intensive Care Unit (NICU). In our prior work we developed an automated algorithm to quantify BDs in >1000 preterm NICU patients, and studied the relationship of these events to central apnea. Obstructive apnea can also lead to BDs but we have found it is sometimes associated with tachycardia-desaturations (TDs; Figure 1). We have observed that TDs also occur during periods of agitation and stress without apnea. We sought to quantify these episodes in relation to gestational and postmenstrual age (GA, PMA), with the long-term goal of understanding the importance of TDs as a biomarker of cardiorespiratory stress in the NICU.

Objective: Quantify daily TDs and BDs in NICU patients across a range of GA and PMA.

Design/Methods: All patients in the University of Virginia NICU since 2009 have continuous bedside monitor vital sign data stored for research. For this study we analyzed 2-second heart rate and pulse oximeter oxygen saturation (HR, SpO2) from all infants 24-39w GA admitted from 2012 to 2015. TDs were defined as a 20% increase in HR from the previous 2-hour mean baseline and concurrent SpO2 < 80% at least 10 seconds. BDs were defined as in our prior publications as HR < 100 bpm for at least 4 seconds with concurrent SpO2 < 80% at least 10 seconds. We calculated the median daily TDs and BDs for the entire NICU stay.

Results: HR and SpO2 data from 1725 infants were analyzed at each combination of GA and PMA. TDs were less frequent than BDs and occurred more often at higher PMA (Figure 2 bottom). GA did not have a major impact on number of daily TDs; at 38-39 weeks PMA, median daily TDs was between 1 and 3 across a range of GA. In contrast, BDs were more frequent at lower GA and PMA (Figure 2, top). BDs occurred most frequently in infants < 29 weeks GA and BDs decreased as these infants approached term PMA.Conclusion(s): Episodes of tachycardia-desaturation at the thresholds defined in this analysis occur more frequently at term corrected age. Quantification of TD episodes is a first step toward understanding their clinical significance including potential association with obstructive apnea as well as agitation and stress in NICU patients.
Figure 1: Example of TDs associated with obstructive apneaIn this 20 minute tracing from a capnography study, OA is evidenced by exhaled CO2-Respiratory Rate (purple) declining toward zero while the chest impedance respiratory rate (red) does not indicate central apnea. There are several episodes of OA with HR (blue) increasing by more than 30 beats/minute and SpO2 decreasing to < 80%.
Figure 2: Daily BD and TD episodes by gestational and postmenstrual age.Median number of daily BDs (top) and TDs (bottom) by GA (y axis 24-39 weeks bottom to top) and PMA (x axis 24-39 weeks left to right). The heat map color scale goes from lowest in blue (0 episodes/day) to highest in red (6 episodes/day). Number of infants with data analyzed at each GA and PMA is indicated in the boxes.