Arterial Pulse Physiology Notes

Arterial Pulse Introduction

The arterial pulse is defined as the pressure changes transmitted in the form of waves through the arterial wall and blood column from the heart to the periphery.

When the heart contracts the blood is ejected into the aorta with great force. It causes distension of this blood vessel and a rise in pressure.

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A pressure wave is produced on the elastic wall of the aorta. It travels rapidly from the heart and can be felt after a brief interval, at any superficial peripheral artery like the radial artery at the wrist. Pulse rate is the accurate measure of heart rate except in conditions like pulse deficit.

Transmission Of Pulse

• The central arterial pulse is transmitted to the peripheral arteries as a peripheral arterial pulse.
• The formation and transmission of pulse waves depend upon the elasticity of blood vessels.
• Thus, when the walls of the arteries are more distensible the pressure rise is less and so the transmission of pulse is less.
• When the arterial wall loses its elastic property and becomes rigid as in old age, the pressure rise is more and the transmission of pulse is also more.
• Pulse is not transmitted to capillaries because capillaries are devoid of elastic tissues.

Velocity Of Transmission Of Pulse

• The average velocity at which the pulse wave is transmitted varies between 7 and 9 meters/second.
• The velocity of pulse transmission is greater than the velocity of blood flow.
• The maximum velocity of blood flow in the body (in larger arteries) is only 50 cm/second.

Delay In The Transmission Of Pulse

At the arteries, the pulse is felt after a short interval from the beginning of ventricular systole.

This delay is very small and, it can be measured only by accurate recording. The delay is directly proportional to the distance from the heart.

The delay at the common carotid artery is 0.01-0.OS second. In the radial artery, it is about 0.08 seconds.

Methods Of Recording Arterial Pulse

1. By Using Manometer

In animals, the pulse is recorded by inserting a cannula into the dissected artery. This cannula is connected to a manometer or any recording device.

2. By Using Dudgeon’S Sphygmograph

Dudgeon’s sphygmograph is tied to the wrist in such a way that a small plate rests on the skin over the radial artery.

Movements of the arterial wall are magnified by a series of levers and are recorded on a moving strip of smoked paper.

This instrument is outdated and it is replaced by electronic pulse transducers.

3. By Using Electronic Pulse Transducer

• It is placed over the finger and tied. The device throws light on the blood vessel through the skin.
• The reflected light from the flowing blood is deducted by the sensor of the device.
• The alteration in frequency of the reflected light rays is amplified and recorded by connecting the transducer to a recording device like a polygraph.
• The record shows finger pulse volume, which represents arterial pulse tracing.

Interpretation Of Arterial Pulse Tracing

The pulse recorded in a radial artery or femoral artery is the typical peripheral pulse.

Peripheral pulse tracing has three main features.

1. Anacrotic Limb

It is ascending limb or upstroke. It is also called a primary wave. It is due to the rise in pressure during systole.

2. Calaerotic Limb

It is describing or downstroke. It is due to the fall in pressure To diastole.

3. Catacrotic Notch

In the upper pad of the catacrotic limb of pulse tracing, a small notch appears. It is known as a catacrotic notch or incisura.

This notch is produced by the backflow of blood during the closure of semilunar valves at the beginning of the diastolic period, which produces a slight increase in pressure.

4. Pre and Postcatacrotic Waves

The wave appearing before the notch is called pre- catacrotic notch. The wave appearing after the notch is called postcatacrotic wave.

Pulse Points

Usually, the pulse is palpated on the radial artery because it is easily approachable and placed superficially.

However, the arterial pulse can be felt in different areas of the body. These areas are called pulse points.

1. Temporal pulse – over the temple in front of the ear on the superficial temporal artery
2. Facial pulse – on the facial artery at the angle of the jaw
3. Carotid pulse – in the neck along the anterior border of the sternocleidomastoid muscle on the common carotid artery
4. Axillary pulse – in axilla on axillary artery
5. Brachial pulse – in the cubital fossa along the medial border of the biceps muscle on the brachial artery
6. Radial pulse over the thumb side of the wrist between tendons of brachioradialis and flexor carpi radialis muscles on the radial artery
7. Ulnar pulse – over the little finger side of the wrist on the ulnar artery
8. Femoral pulse – in the groin on the femoral artery
9. Popliteal pulse – behind the knee in the popliteal fossa on the popliteal artery
10. Dorsalis pedis pulse – over the dorsum of the foot on dorsalis pedis artery
11. Tibialis pulse over the back of the ankle behind the medial malleolus on the posterior tibial artery.

Examination Of Radial Pulse

• Examination of the pulse is a valuable clinical procedure. Pulse represents the heartbeat.
• By examining the pulse, important information regarding cardiac function such as rate of contraction, rhythmicity, etc. can be obtained.
• In addition, an experienced physician can determine the mean arterial pressure by the hardness of the pulse and its amplitude.
• Pulse is examined by placing the tips of three fingers, index finger, middle finger, and ring finger on the artery.

While examining the pulse, the following features are observed:

1. Rate
2. Rhythm
3. Character
4. Volume
5. Condition of the blood vessel wall
6. Delayed pulse.

1. Rate

The number of pulses per minute is the pulse rate. It has to be counted at least for 30 seconds. The pulse rate in adults is 72 (per minute).

The pulse rate per minute at different ages is:

• In fetus:150-180
• At birth:130-140
• At 10 years of age:90
• After puberty:72

Radial Pulse Variations

The conditions which alter heart rate, alter pulse rate also.

Pulse rate increases during:

1. Exercise
2. Pregnancy
3. Emotional conditions
4. Fever
5. Anemia
6. Hypersecretion of catecholamines
7. Hyperthyroidism.

Pulse rate decreases during:

1. Sleep
2. Hypothermia
3. Hypothyroidism
4. Incomplete heart block.

2. Rhythm

• The regularity of the pulse is known as rhythm. Under normal conditions, the pulse appears at regular intervals.
• The rhythm of the pulse becomes irregular in conditions like atrial fibrillation, extrasystole, and other types of arrhythmia.
• The irregular rhythm of the pulse is of two types, regularly irregular and irregularly irregular.

3. Character

• The character of the pulse is observed while examining the pulse. it denotes the tension on the vessel wall produced by the waves of the pulse.
• Normally, it is not possible to detect the different waves of the pulse or slight variations in the character or form of the pulse.
• However, becomes more prominent in some abnormal conditions such as anacrotic pulse, water hammer pulse, pulses paradoxes, etc.

4. Volume

It is the determination of the movement of the vessel wall produced by the transmission of a pulse wave.

It is also a measure of pulse pressure. It depends upon the condition of the blood vessel.

5. Condition Of The Wall Of The Blood Vessel

• It is determined by obstructing the blood flow at the brachial artery and rolling the radial artery against the underlying bones.
• Normally, the wall of the vessel is not palpable in children and young adults.
• However, in old age, the wall of the vessel becomes rigid and palpable. In abnormal conditions like arteriosclerosis, it is felt as a hard rope.

6. Delayed Pulse

Sometimes the arrival of pulse in certain peripheral arteries is delayed. It is an important feature to be noted because it is useful in the diagnosis of certain diseases. Two such conditions are:

1. Femoral delay
2. Radial-radial delay.
3. Femoral Delay

1. Femoral Delay

• While palpating the radial pulse and femoral pulse simultaneously, there is a short delay in the arrival of the femoral pulse wave.
• Normally it is negligible and unnoticed. However, the prolonged or noticeable delay in the arrival of the femoral pulse indicates coarctation (narrowing) of the aorta.
• This delay is called femoral delay, radial femoral delay, or radiofemoral delay.

2. Radial-radial Delay

• When, both the radial pulses are examined simultaneously, sometimes the arrival of the pulse is delayed on one side.
• It is called radial-radial delay or radial-radial inequality. This indicates the narrowing of large arteries due to atherosclerosis.

Applied Physiology – Abnormal Pulse

1. Pulsus Deficit

• Pulsus deficit is an abnormal condition in which the pulse rate is less than the heart rate.
• It occurs in atrial fibrillation when the stroke volume is reduced. Because of reduced stroke volume, some of the pulse waves become weak and disappear before reaching the peripheral arteries.
• Pulsus deficit is the only condition in which the pulse rate is less than the heart rate.

2. Pulsus Alternans

• It is the abnormal condition in which the amplitude of every second wave in pulse tracing is relatively smaller.
• It is because of the alternate variation in the force of ventricular contraction.
• However, the rhythm of the pulse is not altered. It is common in severe myocardial diseases, paroxysmal tachycardia, and atrial fibrillation.

3. Anacrotic Pulse

An anacrotic pulse is an abnormal pulse characterized by a slow ascending limb that has a notch called an anacrotic notch. It is produced in aortic stenosis when ejection is slow.

4. Thready Pulse Or Weak Pulse

• A thready or weak pulse is an abnormal pulse in which the volume of the pulse becomes very feeble and is hardly felt in the arteries.
• It usually occurs whenever the stroke volume decreases or when there is severe vasoconstriction as in the case of severe hemorrhage or severe chills.
• In these conditions, the sympathetic activity increases enormously leading to generalized vasoconstriction.

5. Pulsus paradoxus

• Pulses paradoxus is the condition when the pulse becomes very strong and very weak alternately in relation to the respiratory cycle.
• Normally, there is a slight increase in the volume of the pulse during inspiration and a slight decrease in volume during expiration.
• But, it is hardly noticed. However, when it becomes very prominent, it is pathological.
• This type of pulse is noticed in cardiac tamponade. It is also noticed in physiological conditions such as deep breathing.

6. Water Hammer Pulse

• A water hammer pulse is an abnormal pulse characterized by a rapid upstroke and an equally rapid downstroke. It is also called collapsing or Corrigan pulse.
• It is seen in conditions like aortic regurgitation, patent ductus arteriosus, and arteriovenous fistula.
• It is best felt by raising the arm of the subject and holding it by grasping the wrist with the palm of the observer.

7. Abnormal Pulse In Patent Ductus

• Arteriosus in the fetus, the lungs are nonfunctioning.
• So, the blood, which is pumped by the right ventricle into the pulmonary artery, is diverted to the systemic aorta through the ductus arteriosus.
• After birth, the ductus arteriosus is closed.
• However, in some cases, the ductus arteriosus does not close and exists permanently. This condition is called patent ductus arteriosus Innominate artery
• The pulse pressure wave is very much altered in this condition. Since, the blood flows from the systemic aorta to the pulmonary artery, after every ventricular systole, the blood flows out of the aorta quickly.

• It decreases the diastole pressure and, the catacrotic limb of the pulse tracing falls below the level of 80 mm Hg.
• The flow of blood from the aorta to the pulmonary artery increases the venous return to the left side of the heart.
• So, the left ventricular output increases. It elevates the systolic pressure in arteries.
• Thus, in pulse tracing, the peak of the pulse wave is elevated above the level of 120 mm Hg.
• So, the pulse tracing in this condition reveals the increased pulse pressure.

8. Abnormal Pulse In Aortic Regurgitation

• Aortic regurgitation is the backflow of blood from the aorta into the left ventricle.
• It is common during incompetence of the semilunar valve in the aorta. It decreases the diastolic pressure.
• Because of the backflow of blood, the left ventricular filling increases greatly, leading to an increase in output and systolic pressure.
• Thus, the pulse tracing in aortic regurgitation is more or less similar to that in patent ductus arteriosus.
• The only difference is that, in the tracing during aortic regurgitation, the incisura is very mild. And in severe conditions, when the aortic valve does not close, the nebula is absent.