Pulse

# Overview
Pulse is the throbbing of the arteries as an effect of the heart beat. It can be felt in any place that allows for an artery to be compressed against a bone, such as at the neck (carotid artery), at the wrist (radial artery), behind the knee (popliteal artery), on the inside of the elbow (brachial artery), and near the ankle joint (posterior tibial artery). The pulse rate can also be measured by measuring the heart beats directly (the apical pulse).
Pressure waves move the artery walls, which are pliable; these waves are not caused by the forward movement of the blood. When the heart contracts, blood is ejected into the aorta and the aorta stretches. At this point, the wave of distention (pulse wave) is pronounced but relatively slow-moving (36 m/s). As it travels towards the peripheral blood vessels, it gradually diminishes and becomes faster. In the large arterial branches, its velocity is 710 m/s; in the small arteries, it is 1535 m/s. The pressure pulse is transmitted fifteen or more times more rapidly than the blood flow.
Pulse is also used, although incorrectly, to denote the frequency of the heart beat, usually measured in beats per minute. In most people, the pulse is an accurate measure of heart rate. Under certain circumstances, including arrhythmias, some of the heart beats are ineffective, and the aorta is not stretched enough to create a palpable pressure wave. The pulse is too irregular and the heart rate can be (much) higher than the pulse rate. In this case, the heart rate should be determined by auscultation of the heart apex, in which case it is not the pulse. The pulse deficit (difference between heart beats and pulsations at the periphery) should be determined by simultaneous palpation at the radial artery and auscultation at the heart apex.
A normal pulse rate for a healthy adult, while resting, can range from 60 to 100 beats per minute (BPM), although well conditioned athletes may have a healthy pulse rate lower than 60 BPM. Bradycardia occurs when the pulse rate is below 60 per minute, whereas tachycardia occurs when the rate is above 100 BPM. During sleep, this can drop to as low as 40 BPM; during strenuous exercise, it can rise as high as 150200 BPM. Generally, pulse rates are higher in infants and young children. The resting heart rate for an infant is usually close to an adult's pulse rate during strenuous exercise (average 110 BPM for an infant).
A collapsing pulse is a sign of hyperdynamic circulation.

# Common pulse sites
- Apical pulse: located in the 4th or 5th left intercostal space, just to the left of the sternum. In contrast with other pulse sites, the apical pulse site is unilateral, and measured not over an artery, but over the heart itself (more specifically, the apex of the heart).
- Brachial pulse: located between the biceps and triceps, on the medial side of the elbow cavity, frequently used in place of carotid pulse in infants (brachial artery)
- Carotid pulse: located in the neck (carotid artery). The carotid artery should be palpated gently and while the patient is sitting or lying down. Stimulating its baroreceptors with vigorous palpitation can provoke severe bradycardia or even stop the heart in some sensitive persons. Also, a person's two carotid arteries should not be palpated at the same time. Doing so may limit the flow of blood to the head, possibly leading to fainting or brain ischemia.  It can be felt between the anterior border of the sternocleidomastoid muscle, above the hyoid bone and lateral to the thyroid cartilage.
- Dorsalis pedis pulse: located on top of the foot (dorsalis pedis artery).
- Facial pulse: located on the mandible (lower jawbone) on a line with the corners of the mouth (facial artery).
- Femoral pulse: located in the thigh, halfway between the pubic symphysis and anterior superior iliac spine (femoral artery).
- Popliteal pulse: located behind the knee in the popliteal fossa, found by holding the bent knee. The patient bends the knee at approximately 120, and the physician holds it in both hands to find the popliteal artery in the pit behind the knee.
- Radial pulse: located on the thumb side of the wrist (radial artery).   It can also be found in the anatomical snuff box.
- Temporal pulse: located on the temple directly in front of the ear (superficial temporal artery).
- Tibialis posterior pulse: located on the medial side of the ankle (facing inwards) behind the medial malleolus (posterior tibial artery).
- Ulnar pulse: located on the little finger side of the wrist(ulnar artery).
The ease of palpability of a pulse is dictated by the patient's blood pressure. If his or her systolic blood pressure is below 80 mmHg, the radial pulse will not be palpable. Below 70 mmHg, the brachial pulse will not be palpable. Below 60 mmHg, the carotid pulse will not be palpable. However, a study by the National Institutes of Health indicated that this method was not accurate enough and often overestimated a patient's systolic blood pressure. The lack of a palpable carotid pulse is often an indication of death.

# Reading a pulse
Pulses are manually palpated with fingers. When palpating the carotid artery, the femoral artery or the brachial artery, the thumb may be used. However, the thumb has its own pulse which can interfere with detecting the patient's pulse at other points, where two or three fingers should be used. Fingers or the thumb must be placed near an artery and pressed gently against a firm structure, usually a bone, in order to feel the pulse.
Make sure the person is calm and has been resting for 5 minutes before reading the pulse. Put the index and middle fingers over the pulse count, and count for 30 seconds, and afterwards multiply by 2, to get the pulse rate. If the person's pulse rate is irregular, count for a full minute, and do not multiply. Averaging multiple readings may give a more representative figure.
Home blood pressure measurement devices also typically give a pulse reading.