Prediction of inspired oxygen fraction for targeted arterial oxygen tension following open heart surgery in non-smoking and smoking patients

Abstract

Simple and accurate expressions describing the PaO2–FiO2 relationship in mechanically ventilated patients are lacking. The current study aims to validate a novel mathematical expression for accurate prediction of the fraction of inspired oxygen that will result in a targeted arterial oxygen tension in non-smoking and smoking patients receiving mechanical ventilation following open heart surgeries. One hundred PaO2–FiO2 data pairs were obtained from 25 non-smoking patients mechanically ventilated following open heart surgeries. One data pair was collected at each of FiO2 of 40, 60, 80, and 100% while maintaining same mechanical ventilation support settings. Similarly, another 100 hundred PaO2–FiO2 data pairs were obtained from 25 smoking patients mechanically ventilated following open heart surgeries. The utility of the new mathematical expression in accurately describing the PaO2–FiO2 relationship in these patients was assessed by the regression and Bland–Altman analyses. Significant correlations were seen between the true and estimated FiO2 values in non-smoking (r2 = 0.9424; p < 0.05) and smoking (r2 = 0.9466; p < 0.05) patients. Tight biases between the true and estimated FiO2 values for non-smoking (3.1%) and smoking (4.1%) patients were observed. Also, significant correlations were seen between the true and estimated PaO2/FiO2 ratios in non-smoking (r2 = 0.9530; p < 0.05) and smoking (r2 = 0.9675; p < 0.05) patients. Tight biases between the true and estimated PaO2/FiO2 ratios for non-smoking (−18 mmHg) and smoking (−16 mmHg) patients were also observed. The new mathematical expression for the description of the PaO2–FiO2 relationship is valid and accurate in non-smoking and smoking patients who are receiving mechanical ventilation for post cardiac surgery. © 2016, Springer Science+Business Media Dordrecht.