Nursing 105

Essentials of Nursing Study Guide

Chapter Three: Oxygenation

©2018 Achieve Page 65 of 160 is the movement of gases and particles from an area of greater pressure or concentration to an area of lower pressure or concentration. Transport of respiratory gases is affected by cardiac output, the number of erythrocytes (blood hematocrit), as well as exercise. Erythrocytes are the red blood cells (men approximately 5 million/cubic milliliters; women approximately 4 ½ million/cubic milliliters). Hematocrit is the percentage of the blood that is erythrocytes (men 40-54%, women 37- 47%). Cardiac output is the volume of blood pumped by the heart in one minute and is roughly 4.9 L/min for women and 5.6 L/min for men. Carbon dioxide is transported from the cells to the lungs in three ways: • Bicarbonate (~65%) carried inside theRBC • Carbaminohemoglobin (~30%) carbon dioxide combined withhemoglobin • Carbonic acid (~5%) CO2 combined withwater 3.1 Physiology of the Respiratory System The upper respiratory system and lower respiratory system are composed of the mouth, trachea, nose, lungs, pharynx, bronchi, bronchioles, alveoli, larynx, pulmonary capillary network, and pleural membrane. The respiratory centers of the medulla and pons in the brain stem control breathing. If there is depressing of the central nervous system (head injury, drugs-opiates, and barbiturates) this can affect the respiratory center and impair the drive to breathe. The intra-pleural pressure (pressure in the cavity surrounding the lungs) is always slightly negative in relation to the atmospheric pressure. Intrapulmonary pressure (within the lungs) equalizes with atmospheric pressure. Respiration occurs when the diaphragm and intercostal muscles contract, increasing the size of the thoracic cavity. This will cause lung volume to increase, decreasing intrapulmonary pressure. Air then rushes into the lungs to equalize this pressure with atmospheric pressure. Tidal volume is approximately 500 mL of air that is inspired and expired with each breath. During strenuous exercise, tidal volume can increase to 1500 ml. Adequate ventilation depends on: • Clear airways • Intact CNS and respiratory center • Intact thoracic cavity capable of expanding and contracting • Adequate pulmonary compliance and recoil (lung compliance tends to decrease with aging, making it more difficult to expand the alveoli, increasing the risk of atelectasis, or collapse of a portion of the lung) Diffusion