The aim of this study was to analyze signal loss (SL) resulting from low signal quality of pulse oximetry-derived hemoglobin oxygen saturation (SpO(2)) measurements during prolonged hypoxemic episodes (pHE) in very preterm infants receiving automatic oxygen control (AOC). We did a post hoc analysis of a randomized crossover study of AOC, programmed to set FiO(2) to “back-up FiO(2)” during SL. In 24 preterm infants (median (interquartile range)) gestational age 25.3 (24.6 to 25.6) …