PULSE

INTRODUCTION

Pulse is the beat of the heart that is felt through the peripheral arteries. When the blood is pushed through the walls of the arteries a shock wave travels along the walls of the arteries as the heart contracts.

This shock wave is generated by the pounding of the blood as it is ejected from the heart under pressure. It is like the hammering sound felt in  arteries as the steam of blood is forced into the arteries under pressure from the ventricles.

DEFINITION

Pulse is a rhythmic dilation of an artery generated by the opening and closing of the aortic valve in the heart. A pulse can be felt by applying firm fingertip pressure to the skin at sites where the arteries travel near the skin’s surface.

STAGES OF PULSE

• Isovolumic Relaxation: Closure of the Semilunar valves (Aortic & Pulmonic) at the end of ejection stage that results in stop in the blood flow to the heart.
• Inflow: 
  • ventricles and atria together relax and expand; blood flows to the heart during ventricular and atrial diastole.
  • ventricles relaxed and expanded; atrial contraction (systole) forces blood under pressure into ventricles during ventricular diastole.
• Isovolumic Contraction: Closure of Atrio-ventricular valves at the end of ventricular diastole; blood flow stops; ventricles begin to contract.
• Ejection: Ventricles contract (ventricular systole); blood flows from the heart—to the lungs and to rest of body during ventricular ejection.

MECHANISM OF PULSE

• Isovolumic relaxation" plus “Inflow”—comprise the ventricular "Diastole" period, including atrial systole, during which blood returning to the heart flows through the atria into the relaxed ventricles.
• "Isovolumic contraction" plus "Ejection"—are the ventricular "Systole" period, which is the simultaneous pumping of separate blood supplies from the two ventricles, one to the pulmonary artery and one to the aorta.

PHYSIOLOGY OF PULSE

Starting in the diastolic period comprising of low volume in isovolumic relaxation stage

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Rapid rise in the blood flow during the components of inflow stages in the atria & Ventricles

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Increase in the volume causing systole in the Isovolumic Contraction Stage

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Rapid decrease in the blood volume that signifies the emptying of the ventricles in the Ejection Stage

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All equals to one heart beat that denotes the pulse

REGULATION OF PULSE

• SA Node: 
  • The heart rate is established by the Sinoatrial Node (SAN) – the pacemaker of the cardiac muscle. Heart rate and cardiac output varies in response to the needs of the body. By influencing the cells in the SAN, nerve impulses and hormones can affect the speed at which the SAN generates electrical impulse. This affects the heart rate & pulse.
• Autonomic Nervous System Regulation: 
  • The parasympathetic input into the heart is via the vagus nerve (CN X). The vagus nerve forms synapses with postganglionic cells in SAN and AVN. When stimulated, acetylcholine which binds on to M₂ receptors, which acts to decrease the slope of the pacemaker potential, leading to a decrease in heart rate (a negative chronotropic effect).
  • The sympathetic input into the heart is via the postganglionic fibres from the sympathetic trunk which innervate the SAN and AVN. The post ganglionic fibres release noradrenaline, which acts on B₁ adrenoreceptors to increase the slope of the pace maker potential, thereby increasing the heart rate as well as increasing the force of contraction (positive inotropic effect).
• Baroreceptor Reflex: 
  • Baroreceptors are mechanoreceptors located in both the carotid sinus and the aortic arch, which are sensitive to stretch. Their function is to detect changes in arterial pressure and communicate this to the medulla oblongata in the brainstem. The medullary centres in the brain are responsible for the overall output of the autonomic nervous system, and use the information feed back from baroreceptors to coordinate a response by stimulation of the Autonomic Nerves.
• Hormonal Control: 
  • Hormones also have the ability to affect the heart rate. Adrenaline, which is released from the medulla of adrenal glands is released into the blood stream at a time when a person encounters a stressful situation. The release of this hormone can result in a number of effects that increases of the heart rate.

CHARACTERISTICS OF PULSE: 

• Pulse Rhythm
  • The normal pulse rhythm is regular, meaning that the frequency of the pulsation felt by the fingers follows an even pattern with equal intervals between pulsations.
  • If a pulse has an irregular rhythm, it is important to determine whether it is regularly irregular (e.g., three regular beats and one missed and this is repeated) or if it is irregularly irregular (e.g., there is no rhythm to the irregularity).
• Pulse Rate
  • The pulse rate is counted by starting at one, which correlates with the first beat felt by palpating with fingers. Count for one minute to obtain the pulse rate. The Normal Pulse Rate at beats per minute are as follows.

• Pulse Force
  • The pulse force is the strength of the pulsation felt when palpating the pulse. The force is important to assess because it reflects the volume of blood, the heart’s functioning and cardiac output, and the arteries elastic properties. pulse force provides an idea of how hard the heart has to pump blood out of the heart and through the circulatory system.
  • Pulse force is recorded using a four-point scale:

3+ Full, bounding

2+ Normal/strong

1+ Weak, diminished, thready

0 Absent/non-palpable

• Pulse Equality
  • Pulse equality refers to whether the pulse force is comparable on both sides of the body. For example, palpate the radial pulse on the right and left wrist at the same time and compare whether the pulse force is equal. However, the carotid pulses should never be palpated at the same time as this can decrease and/or compromise cerebral blood flow.
• Pulse Volume
  • It is 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.
• Pulse Tension
  • It corresponds to diastolic blood pressure. A low tension pulse (pulsus mollis), the vessel is soft or impalpable between beats. In high tension pulse (pulsus durus), vessels feel rigid even between pulse beats.
• Pulse Form
  • A form or contour of a pulse is palpatory estimation of arteries. A quickly rising and quickly falling pulse (pulsus celer) is seen in aortic regurgitation. A slow rising and slowly falling pulse (pulsus tardus) is seen in aortic stenosis.

FACTORS AFFECTING HEART RATE

• Age: According to the Age of the Individual the Heart rate also varies
• Gender: Females have higher heart rate compared to males
• Body Size: People who are very obese with increased body Size will have a slightly Increased Heart rate than compared to people with less body mass.

FACTORS AFFECTING PULSE

• Emotions & Anxiety: Emotions and anxiety can raise heart rate by triggering hormones that increases the heart contractility.
• Weather & Body Temperature: When it is too hot or too cold the body senses a thermal stress. Temperatures above 70 degrees (F) and below 35 degrees (F) will increase heart rate at least 2-4 beats per minute
• Exercise:
  • Walk or run upstairs the heart rate increases.
  • Walk or run downstairs the heart rate decreases
• Dehydration: when dehydrated, blood becomes thicker and waste products build up in bloodstream. The heart contracts harder to maintain constant cardiac output. A fluid loss of 3% of body weight increases pulse rate because of decrease in circulating blood volume.
• Medications:
  • Depending upon the medication, heart rate can either decrease or increase.
  • Medications like beta blockers decreases the heart rate & Thyroid Drugs Increases the Heart Rate
• Beverages: Intake of Coffee, tea, Alcohol, Nicotine, Tobacco and soda Increases the heart rate.
• Present Illness: Any Recent Illnesses can vary the heart rate as in Tachycardia there is Increased heart rate & in Bradycardia the heart rate is decreased.