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NURS 3104- Midterm Exam Guide - Comprehensive Notes for the exam ( 17 pages long!)


Department
Nursing
Course Code
NURS 3104
Professor
helena
Study Guide
Midterm

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MRU
NURS 3104
MIDTERM EXAM
STUDY GUIDE

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Cardiac Hemodynamics
An important determinant of blood flow in the cardiovascular system is the principle that fluid
flows from a region of higher pressure to one of lower pressure. The pressures responsible for
blood flow in the normal circulation are generated during systole and diastole. Figure 26-5
depicts the pressure differences in the great vessels and in the four chambers of the heart during
systole and diastole.
Cardiac Cycle
Beginning with systole, the pressure inside the ventricles rapidly rises, forcing the AV valves to
close. As a result,blood ceases to flow from the atria into the ventricles, and regurgitation
(backflow) of blood into the atria is prevented. The rapid rise of pressure inside the right and left
ventricles forces the pulmonic and aortic valves to open,and blood is ejected into the pulmonary
artery and aorta,respectively. The exit of blood is at first rapid; then, as the pressure in each
ventricle and its corresponding artery equalizes, the flow of blood gradually decreases. At the
end of systole, pressure within the right and left ventricles rapidly decreases. This lowers
pulmonary artery and aortic pressure, causing closure of the semilunar valves. These events mark
the onset of diastole. During diastole, when the ventricles are relaxed and the AV valves are
open, blood returning from the veins flowsinto the atria and then into the ventricles. Toward the
end of this diastolic period, the atrial muscles contract in response to an electrical impulse
initiated by the SA node(atrial systole). The resultant contraction raises the pressure inside the
atria, ejecting blood into the ventricles. Atrial systole augments ventricular blood volume by
15% to25% and is sometimes referred to as the “atrial kick.” At this point, ventricular systole
begins in response to propagation of the electrical impulse that began in the SA node some
milliseconds previously. The following section reviews the chamber pressures generated during
systole and diastole.
CHAMBER PRESSURES.
In the right side of the heart, the pressure generated during ventricular systole (15 to 25mm Hg)
exceeds the pulmonary artery diastolic pressure(8 to 15 mm Hg), and blood is ejected into the
pulmonary circulation. During diastole, venous blood flows into the atrium because pressure in
the superior and inferior vena cava (8 to 10 mm Hg) is higher than that in the atrium.Blood flows
through the open tricuspid valve and into the right ventricle until the two right chamber pressures
equalize (0 to 8 mm Hg).In the left side of the heart, similar events occur, although higher
pressures are generated. As pressure mounts in the left ventricle during systole (110 to 130 mm
Hg), resting aortic pressure (80 mm Hg) is exceeded and blood is ejected into the aorta. During
left ventricular ejection, the resultant aortic pressure (110 to 130 mm Hg) forces blood.
Progressively through the arteries. Forward blood flow into the aorta ceases as the ventricle
relaxes and pressure drops. During diastole, oxygenated blood returning from the pulmonary
circulation via the four pulmonary veinsflows into the atrium, where pressure remains low.
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Blood readily flows into the left ventricle because ventricular pressure is also low. At the end of
diastole, pressure in the atrium and ventricle equilibrates (4 to 12 mm Hg).
PRESSURE MEASUREMENT.
Chamber pressures are measured with the use of special monitoring catheters and
equipment.This technique is called hemodynamic monitoring. Nurses caring for critically ill
patients must have a sophisticated working knowledge of normal chamber pressures and the
hemodynamic changes that occur during serious illnesses. The data obtained from hemodynamic
monitoring assist with the diagnosis and management of pathophysiologic conditions affecting
critically ill patients.
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