The goal of this experimental study is to understand if endotracheal tube (ETT) suctioning increases pain and causes stress on the body in intubated adult ICU patients. These patients are already on ventilators, which means they need suctioning to keep their airways clear, but this procedure may be uncomfortable and cause stress. The main questions this study aims to answer are: Does ETT suctioning raise pain levels as measured by the Critical-Care Pain Observation Tool (CPOT)? Does ETT suctioning increase certain chemicals in the blood (hypoxanthine, xanthine, and uric acid) that show stress and lack of oxygen in the body? Researchers will compare patients who have ETT suctioning (intervention group) with those who do not have suctioning during the study period (control group) to see if there are differences in pain and blood markers of stress. Participants will: Have pain measured before and after suctioning using the CPOT. Have blood samples taken from an existing line at three time points: 5 minutes before, 5 minutes after, and 30 minutes after suctioning. Provide demographic information (like age, gender, and diagnosis) from medical records. This research will help improve how pain is managed for ICU patients who cannot speak for themselves, potentially leading to better pain relief methods in the future.