How is the opening pressure measured during a lumbar puncture (LP)?
A lumbar puncture can be conducted with the patient sitting upright or in the lateral recumbent or prone positions. The lateral recumbent or prone positions are favored over the upright position because they allow for a more precise assessment of the opening pressure. However, excessive flexion can compromise the upper airway. For lumbar punctures conducted under fluoroscopic supervision, the prone position is commonly used. To measure the opening pressure, the patient must lie in the lateral recumbent position with legs straightened to avoid false elevated pressures. Attach a sterile manometer through a stopcock when the fluid is returned from the needle and record the height of the column. The normal opening pressure is less than 20 cm of H2O. It is crucial to measure the opening pressure for evaluation of cryptococcal meningitis or pseudomotor cerebri.