The human brain and spinal cord are immersed in the cerebrospinal fluid. The flu
ID: 1311845 • Letter: T
Question
The human brain and spinal cord are immersed in the cerebrospinal fluid. The fluid is normally continuous between the cranial and spinal cavities and exerts a pressure of 100 to 200 mm of H2O above the prevailing atmospheric pressure. In medical work, pressures are often measured in units of mm of H2O because body fluids, including the cerebrospinal fluid, typically have the same density as water. The pressure of the cerebrospinal fluid can be measured by means of a spinal tap as illustrated in the figure below. A hollow tube is inserted into the spinal column, and the height to which the fluid rises is observed. If the fluid rises to a height of 186 mm, we write its gauge pressure as 186 mm H2O.
(a) Express this pressure in the following units.
(b) Some conditions that block or inhibit the flow of cerebrospinal fluid can be investigated by means of Queckenstedt's test. In this procedure, the veins in the patient's neck are compressed to make the blood pressure rise in the brain, which in turn should be transmitted to the cerebrospinal fluid. Explain how the level of fluid in the spinal tap can be used as a diagnostic tool for the condition of the patient's spine.
Explanation / Answer
1 mmH2O is equal to 9.8 pascal
186 mm H2o = 186 * 9.8 pascals = 1822.8 Pa
1 mm H2O = 0.0000967841009836 ATM
186 mm H2O = 186* 0.0000967841009836 ATm = 0.018 ATM
1 mm H2O = 0.0735559121015 mm Hg
186 mm H2O = 186 * 0.0735559121015 mm Hg = 13.68 mm Hg
B) When the veins in the patient's neck is compressed to make the blood pressure rise in the brain, which in turn should be transmitted to the cerebrospinal fluid.
which leads to a rise in the intracranial pressure. Given normal anatomy, the intracranial pressure will be reflected as a rapidly rising pressure , within 10
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