Background : The premise of this study design is based on the fact that patient’s metabolic status plays an important role in weaning off a patient from mechanical ventilation. So, we have tried to assess the relative importance of different pulmonary indices of weaning while we also made an attempt to find out the significance of non–pulmonary weaning indices, absolutely as well as relatively Materials And Methods : Total 90 patients [divided randomly into 4 groups with 15 patients in group 1,2,3each (named Pulmonary group) while group 4 comprised of 45 patients(named Non–pulmonary group] of either sex between the age groups of 16 to 60 years requiring mechanical ventilation. While pulmonary indices were calibrated on pre–set numerical values based on several texts, the non–pulmonary group was assigned a composite score system for quantification purpose. Results : For results, we analyzed the 90 patients in 2 groups namely Pulmonary and Non Pulmonary (45 in each group). The incidence of positive weaning was 77.78% in non–pulmonary groups. The percentage of positive weaning status was maximum in RSBI subgroup (66.7%) in the pulmonary group. There was a significant mean value of composite non–pulmonary score above which a positive outcome could be predicted in both pulmonary and non–pulmonary groups. On regression analysis P/F ratio significantly affected positive outcome on the overall patients , the significance being 0.033. Also, the non–pulmonary variables taken together were also found to significantly affect the positive outcome in total number of patients, significance being 0.001. Conclusion : • On sub–group analysis of pulmonary group, there were non–significant differences between the subgroups with respect to incidence of weaning. • Overall incidence of weaning is higher in non–pulmonary group compared to pulmonary group, but the difference is non–significant (p=0.11) • The non–pulmonary variables (composite score) affect significantly the incidence of weaning in pulmonary group. • On whole model (pooled: n=90), regression analysis shows non–pulmonary variables (composite score) and PF ratio are significant contributors to the incidence of weaning while RSBI and Trigger are non–significant; Further, the non–pulmonary variables (composite score) are more significant than PF ratio.