Blood Pressure Machines
And sometimes, blood pressure monitors will unmask a rare severe case of "white coat hypertension." In this situation, a person can have a nearly normal blood pressure at home but their blood pressure increases in the doctor's office - sometimes to over 180/100 - due to stress caused by seeing the "white coat." In this situation, if medications are given to aggressively treat the high blood pressures in the office, patients may even be at risk of passing out at home from low blood pressure. Automatic blood pressure monitors reveal the difference between the home and office pressures and are enormously helpful in these and other cases.
But rarely, the opposite happens - the presence of the machine itself causes high blood pressure. The occasional person is so unnerved by their blood pressure monitor that it actually causes their blood pressure to increase. Seeing the high blood pressure reading, in turn, causes them to panic, and they press the button on the machine again and again to take more readings, becoming more and more panicked, which in turn causes their pressure to rise even more. This usually results in a frantic phone call and sometimes a visit to the emergency room.
To prevent this from happening, I tell people to take their blood pressure only once after sitting quietly for five minutes. Thankfully, this usually solves this rarely occurring problem, and the majority of people find automatic blood pressure monitors helpful and reassuring.