450 - Etiology and Mechanism of Intermittent Hypoxemia Episodes in Extremely Premature Infants

Poster Number: 450
Publication Number: 450.228

Alaleh Dormishian, University of Miami, Miami, FL, United States; Jose N. Tolosa, University of Miami Leonard M. Miller School of Medicine, Miami, FL, United States; Ana C. Aguilar, University of Miami Leonard M. Miller School of Medicine, Miami, Florida 33161, FL, United States; Alini Schott, University of Miami, Miami, FL, United States; Vicente F. Jimenez, University of Miami Leonard M. Miller School of Medicine, Doral, FL, United States; Eduardo H. Bancalari, University of Miami, Jackson Memorial Hospital, MIAMI, FL, United States; Nelson Claure, University of Miami Leonard M. Miller School of Medicine, Miami, FL, United States

Background: Apnea episodes are believed to be the primary mechanism of intermittent hypoxemia (IH) episodes in spontaneously breathing extremely premature infants. Spontaneous abdominal contractions that impinge on the diaphragm and lead to loss in lung volume and hypoventilation have been shown to trigger IH episodes in intubated infants and shortly after extubation. These contractions are commonly seen during periods of agitation and increased spontaneous activity.

Objective: To determine the prevalence of the above mechanisms of IH episodes in spontaneously breathing extremely premature infants at advancing age.

Design/Methods: Premature infants of 23-28 weeks gestational age enrolled in the University of Miami/Jackson Memorial site study of the NHLBI Prematurity Related Ventilatory Control Program (Pre-Vent) who presented IH episodes were included in the analysis. Recordings of arterial oxygen saturation (SpO2), esophageal pressure (Pesoph), respiratory inductive plethysmography (RIP) of the abdomen (RIPabd), chest wall (RIPcw) and their sum (RIPsum) obtained during 4-hour periods at 32 and/or 36 w PMA were evaluated. IH episodes were defined as a decline in SpO2 < 90% for ≥ 5 s. IH episodes were classified as those resulting from central apnea, abdominal contraction or both during the preceding 30 seconds. Central apnea was identified as a respiratory pause of at least 5 seconds in Pesph, RIPabd and RIPcw. Abdominal contraction was identified as a rise in Pespoh with decrease in RIPabd and/or RIPcw signals and reduced or disorganized ventilation in RIPsum.

Results: Forty-eight infants were studied, 31 at 32w PMA and 46 at 36w PMA. Of these, 29 and 37 infants had IH episodes at 32 and 36w PMA, respectively. In these infants most IH episodes resulted from abdominal contraction with reduced or disorganized ventilation at both 32 and 36w PMA (Table).Conclusion(s): In this group of extremely premature infants the most common mechanism leading to IH episodes was associated with abdominal contraction and reduced or disorganized ventilation. These findings suggest an etiology that is more associated with behavioral changes than with abnormal control of breathing function. This can have important implications for the prevention or treatment of these episodes.
Funded by Prematurity Related Ventilatory Control Program (Pre-Vent) of the National Heart Lung and Blood Institute of the National Institutes of Health (U01HL1336891, U01HL133689).
Table. Number and proportion of IH Episodes according to the trigger mechanismData are Mean ±SD. *: p < .05 vs others by General Linear Model for Repeated Measures.