At this point, the CSF should flow past the stopcock and up the manometer tubing. Again, ensure that the connecting tube is level with the stopcock. Watch the CSF flow up the manometer. When the CSF column reaches its peak you will notice a slight up and down variation with respiration. This is the opening pressure. Normal opening pressures are 5-20 cm H₂O with a relaxed back and legs. This pressure may be as high as 28 cm H₂O if the patient is left curled up.