In these values, which unit is used to express all pressures?

In these values, which unit is used to express all pressures?

• A. mm Hg
• B. cm H2O
• C. kPa
• D. psi

Answer: (A)

Pressures in medical values often come in a few common units, and millimeters of mercury (mm Hg) is the broad, traditional unit used to express many different pressures, from arterial pressures to gas tensions. That makes mm Hg the most consistent choice when a set of pressures appears together, so you can compare values without converting. Why the others aren’t all-encompassing: centimeters of water (cm H2O) are used mainly for small pressure differences in the respiratory system, like airway or ventilator pressures, not for systemic or gas-tension values. Kilopascals (kPa) and pounds per square inch (psi) are SI or engineering units and aren’t standard for typical clinical normal-value tables; using them would require frequent conversions to interpret alongside common clinical measurements expressed in mm Hg.

Pressures in medical values often come in a few common units, and millimeters of mercury (mm Hg) is the broad, traditional unit used to express many different pressures, from arterial pressures to gas tensions. That makes mm Hg the most consistent choice when a set of pressures appears together, so you can compare values without converting.

Why the others aren’t all-encompassing: centimeters of water (cm H2O) are used mainly for small pressure differences in the respiratory system, like airway or ventilator pressures, not for systemic or gas-tension values. Kilopascals (kPa) and pounds per square inch (psi) are SI or engineering units and aren’t standard for typical clinical normal-value tables; using them would require frequent conversions to interpret alongside common clinical measurements expressed in mm Hg.