Etiology and Mechanism of Intermittent Hypoxemia Episodes in Spontaneously Breathing Extremely Premature Infants

Abstract

To evaluate the mechanisms leading to intermittent hypoxemia (IH) episodes in spontaneously breathing extremely premature infants at 32 weeks and 36weeks postmenstrual age (PMA). We studied spontaneously breathing premature infants born at 23-28weeks of gestational age who presented with IH episodes while on noninvasive respiratory support at 32 or 36weeks PMA. Daytime recordings of arterial oxygen saturation (SpO2), esophageal pressure, respiratory inductive plethysmography of the abdomen, chest wall, and their sum were obtained during 4hours at 32 weeks and 36 weeks PMA. IH episodes (SpO2<90% for ≥5seconds) and severe IH episodes (SpO2<80% for ≥5seconds) were classified as resulting from apnea, active exhalation and breath holding, reduced tidal volume (VT), or reduced respiratory rate (RR) during the preceding 60seconds. Fifty-one infants with a mean gestational age of 25.9 ±1.5weeks and a mean birth weight of 846± 185g were included. Of these, 31 and 41 were included in the analysis at 32 weeks and 36weeks PMA, respectively. At both 32 weeks and 36weeks PMA, greater proportions of all IH episodes and severe IH episodes were associated with active exhalation and breath holding than with apnea, reduced RR, or reduced VT. The severity and duration of the IH episodes did not differ between mechanisms. In this group of premature infants, the predominant mechanism associated with daytime IH was active exhalation and breath holding. This etiology is more closely associated with behavioral factors than abnormal respiratory control and can have implications for prevention.