The Effect of Imputation of Pa o2/F i o2from Sp o2/F i o2on the Performance of the Pediatric Index of Mortality 3*

Abstract

Objectives: To investigate if the performance of Pediatric Index of Mortality 3 is improved by including imputed values for the Pao2/Fio2ratio where measurements of Pao2or Fio2are missing. Design: A prospective observational study. Setting: A bi-national pediatric intensive care registry. Patients: The records of 37,983 admissions of children less than 16 years old admitted to 19 ICUs. Interventions: None. Measurements and Main Results: Seven published equations describing an association between Pao2/Fio2and oxygen saturation measured by pulse oximetry (Spo2)/Fio2were used to derive an alternative variable d100 × Fio2/Pao2for the Pediatric Index of Mortality 3 variable 100 × Fio2/Pao2. Six equations exclude Spo2/Fio2values if Spo2is greater than 96-98%. 100 × Fio2/Pao2was missing in 72% of patient records primarily due to missing Pao2, d100 × Fio2/Pao2was missing in 71% of patient records if values of Spo2greater than 97% were excluded or in 17% of patient records if all measurements of Spo2were included. Univariable analysis supported the inclusion of Spo2values greater than 97%. Compared to the standard Pediatric Index of Mortality 3 model, two alternative models imputing 100 × Fio2/Pao2from d100 × Fio2/Pao2only if 100 × Fio2/Pao2was missing, or using d100 × Fio2/Pao2values exclusively, resulted in a small but statistically significant improvements in discrimination of Pediatric Index of Mortality 3 (area under the receiver operator curve 0.9068 [0. 8965-0. 9171]; 0.9083 [0.8981-0.9184]; 0.9087 [0.8987-0.9188], respectively). Conclusions: Imputation of the Pao2/Fio2ratio in cases where arterial sampling was not performed resulted in a large reduction in the rate of missing data if all values of Spo2were included. The imputation technique improved the discrimination of Pediatric Index of Mortality 3; however, the magnitude of the increment in overall model performance was small. A possible benefit of the approach is reducing the potential for bias resulting from variation in practice for invasive monitoring of oxygenation.L6319817452020-06-10 <br />