Hypoxemic Events in Spontaneously Breathing Premature Infants: Etiologic Basis

Abstract

Studies of severe hypoxemic events, defined as an arterial oxygen saturation < 80% greater than 4 s in spontaneously breathing infants, have been limited. The purpose of our study was to examine the distribution of respiratory events that lead to a fall in oximetrically measured oxygen saturation by using breathing patterns, heart rate, and validated pulse oximetry analysis. A total of 161 hypoxemic events were detected in 18 of 30 premature infants studied. Using an inductive plethysmographic based monitor, a total of 460 h of cardiorespiratory monitor recordings were analyzed. Hypoxemic events were categorized as being the direct result of apnea (duration longer than 15 s) or pauses (duration 4-14 s) with either unchanged or lower end-expiratory lung volumes compared with the preevent breaths. The breaths in the preevent period were analyzed for volume, timing, and thoracoabdominal coordination indices. Forty of the 161 events (25%) were associated with apnea of which 80% (31/40) had a mixed/obstructive basis. Ninety-four of the 161 severe hypoxemic events (58%) were associated with pauses with unchanged end-expiratory lung volume. Twenty-two of the 161 events (14%) showed pauses with lower end-expiratory lung volume. There were 5/161 events (3%) with severe hypoxemia in which no pause was observed. Comparison of the preevent periods in each category showed significant differences for only percent tidal volume from initial calibration and arterial oxygen saturation. Sixty-two percent (100/161) of severe hypoxemic events were preceded by hypopneic values of percent tidal volume. Seventy-five percent (40/161) of these hypoxemic events and their etiology would have gone undetected using respiratory monitoring from impedance pneumograms and ECGs. The varied basis for these events underscores the importance of analyzing detailed respiratory wave forms along with movement-free signal of arterial oxygen saturation and ECG, to formulate appropriate intervention strategies.

Relationship Between Functional Residual Capacity and Oxygen Desaturation During Short Central Apneic Events During Sleep in “Late Preterm” Infants

“…The proportion of apneic events with blood-O 2 - desaturation increases with lower baseline blood O 2 -saturation measured just before the apneic event. This confirms previous data (25). As a result, hypoventilation and low basal blood O 2 -saturation values are associated with low O 2 reserves and may increase the likelihood of blood O 2 -desaturation-even during short apneic events.…”

Heart Rate and Oxygen Saturation Correlates of Infant Apnea

“…Frequent episodes of oxygen desaturation have been reported to occur in asymptomatic premature infants, 5 and investigations have found that 75% of hypoxemic events in spontaneously breathing prematures would have gone undetected using our current practice of respiratory monitoring based on impedance pneumography and electrocardiography. 6 Our data suggest that infants at risk for apnea may experience minor perturbations in heart rate but large perturbations in oxygen saturation. Because the degree of oxygen desaturation may not be predicted by heart rate changes, it appears that home monitoring devices should include oxygen saturation detection.…”

Occurrence of oxygen desaturation events during preterm infant bottle feeding near discharge

“…The mechanism by which supplemental oxygen may prevent desaturation events or decrease their severity is unknown; however, it is hypothesized that supplemental oxygen increases the end-expiratory lung volume thereby improving ventilation/perfusion matching [28]. More research is needed to examine the effect of supplemental oxygen on early preterm infant feeding skills and to determine which infants may benefit most from the use of supplemental oxygen during feeding.…”

“…Poets et al [22] found that lower baseline SpO 2 was correlated with an increase in transient desaturations. Adams et al [28] found that preterm infants with lower baseline SpO 2 were more vulnerable to hypoxemic events with even brief interruptions in their breathing. In infants with chronic lung disease, McEvoy et al [29] reported less number and duration of desaturation events when infants' SpO 2 was maintained at a level of 94-96% rather than 87-91%.…”