Beachey: Respiratory Care Anatomy and Physiology, 2nd Edition

Answers to Concept Questions

Chapter 21: Aging and the Cardiopulmonary System

21-1	Decreased mobility, especially the inability to walk leads to decreased lung expansion and ventilatory efficiency. That is, tidal volumes are shallower in the sitting or reclining position than they are in the upright standing position. This leads to a less effective mucociliary clearance mechanism, which combined with the somewhat impaired gag reflex of the elderly leads to an increased susceptibility to respiratory infection and pneumonia.

21-2	The increased compliance of the aging lung offers less recoil force to oppose the outward recoil force of the chest wall. Thus the chest wall is free to expand, stretching the lung until its inward recoil force once again counterbalances the chest wall’s outward recoil force. The end-result is an expanded, barrel-shaped chest (i.e., the anterior-posterior dimensions of the rib cage are nearly equal to its lateral, side-to-side dimensions).

21-3	Exercise requires greater diaphragm excursions to achieve greater tidal volumes; this generally leads to increased ventilation of the lung bases, which normally receive the greatest amount of blood flow because of gravitational effects. Thus basal ventilation-perfusion ratios normally improve with exercise. 

21-4	The effectiveness of a vaccine depends on the body’s ability to form antibodies to the antigen in the vaccine. The ability to form antibodies (protein synthesis) is diminished in older people. Thus vaccines against influenza and pneumonia are less effective in older people than in younger people.

21-5	Increased atrial size lengthens impulse conduction pathways, increasing the amount of time required to depolarize the atria. Atrial fibers are arranged in a circular fashion such that impulses return to their origin during depolarization. If the conduction path is too long, the muscle fibers at the impulse’s origin may have had enough time to repolarize by the time the original impulse returns; the stimulus then reenters these fibers and propagates repeated depolarization cycles—one mechanism of fibrillation.

21-6	Muscle weakness, decreased mobility, loss of dexterity, and a greater likelihood of choking (poor gag reflex) makes frail elderly people less inclined to exert the effort needed to drink water and other fluids.

21-7	Age impairs the cardiac muscle’s sarcoplasmic reticulum from taking up calcium ions after contraction; excess calcium ions in the vicinity of actin and myosin myofibrils hinder diastolic muscle relaxation. Calcium channel–blocking drugs limit the amount of calcium that can enter the muscle fiber in the first place, thus diminishing this problem.