MODEL RELEASED. Ambulatory blood pressure monitor. Man wearing an ambulatory blood pressure monitor on his waist and upper arm while lying down. This device takes measurements of a patient's blood pressure at home or at work, over an extended period. The measurement is done every 15 minutes during the day and every 30 minutes at night. This avoids the 'white coat effect' in which a patient's blood pressure rises significantly when it is measured in a clinical setting. High blood pressure (hypertension) can be caused by kidney disease, hormonal disorders and congenital problems and if left untreated can lead to heart and kidney failure.