Background: Mechanical ventilation is frequently used in pediatric patients to ensure adequate gas exchange, improve respiratory distress, and to resolve pulmonary or other disorders. Monitoring of various parameters which are invasive, while patient is on mechanical ventilation it is fundamental to observe the progress of patient’s condition. We conducted this study to observe if PaO2/FiO2 and the ratio of SPO2 /FiO2 can be used interchangeably, we can have option for lesser invasive parameter.

Aim: To determine the correlation of  PaO2/FiO2  with  SPO2 /FiO2 ratio in children on mechanical ventilation.

Methods:  A Cross-sectional study, Non-probability and purposive sampling. The study conducted at The Children’s hospital and the Institute of Child Health, Lahore from 04-10-2017 to 03-06-2018.

Informed consent was obtained. Arterial blood gas sampling for calculation of PaO2/FiO2 ratio and simultaneous recording of SPO2 for measurement of SPO2/FiO2 ratio was done. The data collected was analysed on S.P.S.S (Statistical Package for Social Sciences) version 22.

Results: In this study 30 patients on mechanical ventilation were enrolled with mean age of 58.55±5 months. There was male predominance. (M: F ratio 2:1). This study showed a

strong positive correlation of the PaO2/FiO2 with SPO2/FiO2 that is r=0.603.

Conclusion: According to our study noninvasive SpO2/FiO2 ratio (PFr) can reliably be used in place of  PaO2/FiO2 ratio(SFr) in children on mechanical ventilation as a  strong correlation was observed between them. The advantage is invasive arterial sampling can be replaced by non-invasive pulse oximetry for oxygen saturation.