Why should an arm not be used for taking blood pressure and how do you ensure this doesn't happen?

An arm should not be used for taking blood pressure if there are conditions such as trauma, recent surgery, or the presence of a fistula for dialysis, as these can lead to inaccurate readings or discomfort for the patient. To ensure this doesn't happen, always assess the patient's medical history and physical condition before taking a measurement, and use the opposite arm or a different site if any contraindications are present. Additionally, if a patient has an injury or condition affecting one arm, clearly communicate with them to choose the best alternative location.