Introduction Extubation failure significantly increases duration of mechanical ventilation and ICU length of stay with increased risk of mortality. So validating certain parameters to predict extubation outcome and avoid extubation failure is necessary. This study aimed at assessing the usefulness of the dead space addition (DSA) test and swallowing evaluation in predicting extubation outcome in mechanically ventilated patients with chronic obstructive pulmonary disease (COPD). Patients and methods Invasively mechanically ventilated patients with COPD considered as candidates for extubation were enrolled and subjected to simplified acute physiology score II calculation, assessment of cough strength, endotracheal secretions quantity, delirium, cuff-leak test, DSA test, and swallowing before extubation. Results A total of 90 patients with mean age of 62.26±7.01 years were enrolled. Overall, 76.9% of patients who failed the DSA test compared with 20.8% of those who accomplished it had failed extubation, and 57.1% of patients with defective swallowing compared with 10.9% of those with efficient swallowing had failed extubation, with a highly significant association between extubation outcome and both DSA fate and swallowing efficiency. Sensitivity, specificity, positive predictive value, and negative predictive value for DSA test were 38.5, 95.3, 76.9, and 79.2%, respectively, and for swallowing were 76.9, 76.6, 57.1, and 89.1%, respectively. An increase of simplified acute physiology score II by one unit increases extubation failure 1.25 times. Moreover, patients who tolerated DSA test whereas had defective swallowing had a likelihood of extubation failure 10 times. Conclusion DSA can predict extubation success and failure by the same power, but swallowing assessment can predict extubation success more than failure. Combined DSA intolerance and defective swallowing increase the prediction of extubation failure by 31 times