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Cardiopulmonary Anatomy & Physiolo...

7th Edition
Des Jardins + 1 other
ISBN: 9781337794909

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Section
BuyFindarrow_forward

Cardiopulmonary Anatomy & Physiolo...

7th Edition
Des Jardins + 1 other
ISBN: 9781337794909
Textbook Problem

Which of the following decreases an individual's stroke volume index?

1. Dobutamine

2. Mechanical ventilation

3. Propranolol

4. Congestive heart failure

A. 2 only

B. 4 only

C. 1 and 3 only

D. 2, 3, and 4 only

Summary Introduction

Introduction:

Stroke volume represents the volume of blood that is pumped by the heart through the left ventricle in a minute. This index represents the ratio of stroke volume to the surface area of the body,

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Its unit is mL/beat/m2. The stroke volume index is altered when the stroke volume changes throughout the body. It is affected by multiple factors including pharmacological agents, chemical stimulus, and mechanical ventilation of the lungs.

Explanation

Justifications/ Explanations for the correct answer:

Option (d) is given as 2, 3 and 4 only. An individual stroke volume index is decreased by mechanical ventilation, propranolol, and congestive heart failure. The stroke volume index depends on the stroke volume of the heart. Mechanical ventilation involves providing oxygen to the body by artificial means. It often leads to hyperinflation of the lungs, causing an increase in ventilation of the lungs, resulting in an increased ventilation-perfusion ratio. This causes a decrease in pulmonary effusion and thus, the capillary blood flow to the alveoli is reduced. The volume of blood ejected by the heart in each contraction is reduced, which leads to a decrease in the stroke volume of the heart. This results in a decreased stroke volume index.

Propranolol is a beta-blocker drug that stimulates the heart muscles to relax. This decreases the heart rate and reduces the pressure requirement for the afterload which results in a decreased stroke volume and stroke volume index.

Congestive heart failure or heart failure is a condition where heart muscles become inadequate to pump efficiently and thus, the heart is unable to distribute the essential amount of blood to the tissues. This inefficiency leads to a decreased amount of blood released during each contraction and the stroke volume index gets reduced. Hence, option (d) is correct.

Explanation for the incorrect answer:

Option (a) is given as 2 only. Mechanical ventilation involves providing oxygen to the body by artificial means...

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