Medical Emergencies · single question
If a patient's arm is positioned BELOW the level of the heart during blood pressure measurement, what happens to the reading?
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Correct answer: A. BP reads falsely HIGH
✓ A) BP reads falsely HIGH when arm is below heart level.
Hydrostatic pressure affects BP measurement: for every inch below heart level, approximately 2 mmHg is added to the reading (gravity increases hydrostatic pressure in the dependent arm). Arm BELOW heart → falsely elevated reading. Arm ABOVE heart → falsely low reading. The arm should be at heart level (mid-sternal level) for accurate measurement. This is a common clinical error in dental chairs where the patient is reclined and the arm hangs below heart level.
Hydrostatic pressure affects BP measurement: for every inch below heart level, approximately 2 mmHg is added to the reading (gravity increases hydrostatic pressure in the dependent arm). Arm BELOW heart → falsely elevated reading. Arm ABOVE heart → falsely low reading. The arm should be at heart level (mid-sternal level) for accurate measurement. This is a common clinical error in dental chairs where the patient is reclined and the arm hangs below heart level.
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