In medicine, a pulse represents the tactile arterial palpation of the cardiac cycle (heartbeat) by trained fingertips. The pulse may be 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), at the groin (femoral artery), behind the knee (popliteal artery), near the ankle joint (posterior tibial artery), and on foot (dorsalis pedis artery). Pulse (or the count of arterial pulse per minute) is equivalent to measuring the heart rate. The heart rate can also be measured by listening to the heart beat by auscultation, traditionally using a stethoscope and counting it for a minute. The radial pulse is commonly measured using three fingers. This has a reason: the finger closest to the heart is used to occlude the pulse pressure, the middle finger is used get a crude estimate of the blood pressure, and the finger most distal to the heart (usually the ring finger) is used to nullify the effect of the ulnar pulse as the two arteries are connected via the palmar arches (superficial and deep). The study of the pulse is known as sphygmology.
Physiology
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.
The heart rate may
greater or lesser than the pulse rate depending upon physiologic demand. In this case, the heart rate is determined by auscultation or audible sounds at the heart apex, in which case it is not the pulse. The pulse deficit (difference between heart beats and pulsations at the periphery) is determined by simultaneous palpation at the radial artery and auscultation at the PMI, near the heart apex. It may be present in case of premature beats or atrial fibrillation.
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 rate of the pulse is observed and measured by tactile or visual means on the outside of an artery and is recorded as beats per minute or BPM.
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.
Characteristics
Rate
Normal pulse rates at rest, in beats per minute (BPM):
The pulse rate can be used to check overall heart health and fitness level. Generally lower is better, but bradycardias can be dangerous. Symptoms of a dangerously slow heartbeat include weakness, loss of energy and fainting.
Rhythm
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.
Volume
The degree of expansion displayed by artery during diastolic and systolic state is called volume. It is also known as amplitude, expansion or size of pulse.
Hypokinetic pulse
A weak pulse signifies narrow pulse pressure. It may be due to low cardiac output (as seen in shock, congestive cardiac failure), hypovolemia, valvular heart disease (such as aortic outflow tract obstruction, mitral stenosis, aortic arch syndrome) etc.
Hyperkinetic pulse
A bounding pulse signifies high pulse pressure. It may be due to low peripheral resistance (as seen in fever, anemia, thyrotoxicosis, , A-V fistula, Paget's disease, beriberi, liver cirrhosis), increased cardiac output, increased stroke volume (as seen in anxiety, exercise, complete heart block, aortic regurgitation), decreased distensibility of arterial system (as seen in atherosclerosis, hypertension and coarctation of aorta).