Physiological instability after respiratory pauses in preterm infants

Background: The factors influencing the severity of apnea-related hypoxemia and bradycardia are incompletely characterized, especially in infants receiving noninvasive respiratory support.

Objectives: To identify the frequency and predictors of physiological instability (hypoxemia-oxygen saturation (SpO₂) <80%, or bradycardia-heart rate (HR) < 100 bpm) following respiratory pauses in infants receiving noninvasive respiratory support.

Methods: Respiratory pause duration, derived from capsule pneumography, was measured in 30 preterm infants of gestation 30 (24-32) weeks [median (interquartile range)] receiving noninvasive respiratory support and supplemental oxygen. For identified pauses of 5 to 29 seconds duration, we measured the magnitude and duration of SpO₂ and HR reductions over a period starting at the pause onset and ending 60 seconds after resumption of breathing. Temporally clustered pauses (<60 seconds separation) were analyzed separately. The relative contribution of respiratory pauses to overall physiological instability was determined, and predictors of instability were sought in regression analysis, including demographic, clinical and situational variables as inputs.

Results: In total, 17 105 isolated and 9180 clustered pauses were identified. Hypoxemia and bradycardia were more likely after longer duration and temporally-clustered pauses. However, the majority of such episodes occurred after 5 to 9 second pauses given their numerical preponderance, and short-lived pauses made a substantial contribution to physiological instability overall. Birth gestation, hemoglobin concentration, form of respiratory support, caffeine treatment, respiratory pause duration and temporal clustering were identified as predictors of instability.

Conclusions: Brief respiratory pauses, especially when clustered, contribute substantially to hypoxemia and bradycardia in preterm infants.