Although endotracheal suctioning is a routine nursing intervention, this procedure can lead to an increase in intracranial pressure (ICP). This study was planned to determine the appropriate suctioning technique (open system suctioning [OS] and closed system suctioning [CS]) to minimize variability of ICP and cerebral perfusion pressure (CPP) in neurologically impaired patients. The study, which was designed as a crossover, single-blind clinical trial, consisted of 32 neurosurgical patients who underwent ICP monitoring, intra-arterial blood pressure monitoring, and endotracheal intubation in the intensive care unit. According to the need for suctioning, each patient in the experimental and control groups underwent suctioning with both closed and open systems. Recordings were composed of the patients' ICP, mean arterial blood pressure, CPP, heart rate (HR), and arterial blood gases during suctioning. It was observed that both suctioning techniques significantly increased ICP, mean arterial blood pressure, CPP, and HR; ICP was found to be significantly higher in OS compared with CS, whereas there were no significant differences in CPP and HR between the two techniques. The patients suctioned using OS had significantly lower mean PaO2 than those suctioned using CS; however, the comparison of the two techniques revealed no significant differences in PaCO2. The data obtained indicate that CS, compared with OS, can be used safely on this patient group.