Pulse

In medicine, pulse is the rhythmic expansion and contraction of an artery in response to the cardiac cycle (heartbeat). The pulse may be felt (palpated) in any place that allows an artery to be compressed near the surface of the body, such as at the neck (carotid artery), wrist (radial artery or ulnar artery), at the groin (femoral artery), behind the knee (popliteal artery), near the ankle joint (posterior tibial artery), and on foot (dorsalis pedis artery). The pulse is most commonly measured at the wrist or neck for adults and at the brachial artery (inner upper arm between the shoulder and elbow) for infants and very young children. A sphygmograph is an instrument for measuring the pulse.

Claudius Galen was perhaps the first physiologist to describe the pulse. The pulse is an expedient tactile method of determination of systolic blood pressure to a trained observer. Diastolic blood pressure is non-palpable and unobservable by tactile methods, occurring between heartbeats.

Pressure waves generated by the heart in systole move the arterial walls. Forward movement of blood occurs when the boundaries are pliable and compliant. These properties form enough to create a palpable pressure wave.

Pulse velocity, pulse deficits and much more physiologic data are readily and simplistically visualized by the use of one or more arterial catheters connected to a transducer and oscilloscope. This invasive technique has been commonly used in intensive care since the 1970s.

The pulse may be further indirectly observed under light absorbances of varying wavelengths with assigned and inexpensively reproduced mathematical ratios. Applied capture of variances of light signal from the blood component hemoglobin under oxygenated vs. deoxygenated conditions allows the technology of pulse oximetry.

The rate of the pulse can be observed and measured on the outside of an artery by tactile or visual means. It is recorded as arterial beats per minute or BPM. Although the pulse and heart beat are related, they are not the same. For example, there is a delay between the onset of the heart beat and the onset of the pulse, known as the pulse transit time, which varies by site. Similarly measurements of heart rate variability and pulse rate variability differ.

In healthy people, the pulse rate is close to the heart rate, as measured by ECG. Measuring the pulse rate is therefore a convenient way to estimate the heart rate. Pulse deficit is a condition in which a person has a difference between their pulse rate and heart rate. It can be observed by simultaneous palpation at the radial artery and auscultation using a stethoscope at the PMI, near the heart apex, for example. Typically, in people with pulse deficit, heart beats do not result in pulsations at the periphery, meaning the pulse rate is lower than the heart rate. Pulse deficit has been found to be significant in the context of premature ventricular contraction^{[citation needed]} and atrial fibrillation.

A normal pulse is regular in rhythm and force. An irregular pulse may be due to sinus arrhythmia, ectopic beats, atrial fibrillation, paroxysmal atrial tachycardia, atrial flutter, partial heart block etc. Intermittent dropping out of beats at pulse is called "intermittent pulse". Examples of regular intermittent (regularly irregular) pulse include pulsus bigeminus, second-degree atrioventricular block. An example of irregular intermittent (irregularly irregular) pulse is atrial fibrillation.