Teacher:In this task, you are given a sentence. You are expected to write the name of the organism substances in the body mentioned in the input. Although there might be several correct answers, you need to write one of them.
Teacher: Now, understand the problem? Solve this instance:  Intra - operative monitoring of partial pressure of tissue oxygen ( PtiO2 ) is a very sensitive method of detecting the decrease of oxygen for cell utilization , due to decreased blood flow , during temporary clipping and after definitive clipping , in middle cerebral artery incidental unruptured aneurysm surgery .
Student:
blood