Physiological signals measured by TMT

a. Electrocardiogram (ECG):

The electrocardiogram (ECG or EKG) is a diagnostic tool that measures and records the electrical activity of the heart in exquisite detail. Interpretation of these details allows diagnosis of a wide range of heart conditions. These conditions can vary from minor to life threatening. It is a noninvasive recording produced by an electrocardiographic device .

Electrical impulses in the heart originate in the Sino atrial node and travel through the intimate conducting system to the heart muscle. The impulses stimulate the myocardial muscle fibers to contract and thus induce systole. The electrical waves can be measured at electrodes placed at specific points on the skin. Electrodes on different sides of the heart measure the activity of different parts of the heart muscle. An ECG displays the voltage between pairs of these electrodes, and the muscle activity that they measure, from different directions, can also be understood as vectors. This display indicates the overall rhythm of the heart and weaknesses in different parts of the heart muscle.

b.   Blood pressure (BP):

Blood pressure (BP) is the pressure exerted by circulating blood on the walls of blood vessels, and is one of the vital signs. During each heartbeat, BP varies between a maximum (systolic) and a minimum (diastolic) pressure. The mean BP, due to pumping by the heart and resistance in blood vessels, decreases as the circulating blood moves away from the heart through arteries. It has its greatest decrease in the small arteries and arterioles, and continues to decrease as the blood moves through the capillaries and back to the heart through veins .Gravity, valves in veins, and pumping from contraction of skeletal muscles, are some other influences on BP at various places in the body .

The term blood pressure usually refers to the pressure measured at a person's upper arm. It is measured on the inside of an elbow at the brachial artery, which is the upper arm's major blood vessel that carries blood away from the heart. A person's BP is usually expressed in terms of the systolic pressure and diastolic pressure. BP is sometimes measured at other places and by other methods, for instance at an ankle. Arterial pressure is most commonly measured via a sphygmomanometer, which use the height of a column of mercury to reflect the circulating pressure. Today BP values are still reported in millimeters of mercury (mmHg), though aneroid and electronic devices do not use mercury  .For each heartbeat, BP varies between systolic and diastolic pressures. Systolic pressure is peak pressure in the arteries, which occurs near the end of the cardiac cycle when the ventricles are contracting. Diastolic pressure is minimum pressure in the arteries, which occurs near the beginning of the cardiac cycle when the ventricles are filled with blood.