Nursing 105

Essentials of Nursing Study Guide

©2018 Achieve Page 71 of 160 is the partial pressure of oxygen in the alveoli and is about 100 mmHg. In venous blood of the pulmonary arteries is about 60 mmHg. PCO2 is the partial pressure of carbon dioxide in the alveoli and is about 40 mmHg, In venous blood of the pulmonary capillaries it is about 45 mmHg. PaO2 the ‘a’ stands for arterial blood. With the transport of O2 and CO2, normally most the O2 (97%) combines loosely with hemoglobin in the red blood cells and is carried to the tissues as oxyhemoglobin. The remaining oxygen is dissolved and transported in the fluid of the plasma and cells. Transport Factors affecting the rate of transport: • Cardiac output: the amount of blood pumped by the heart in one minute (5 lpm) • Hematocrit: the percentage of blood that is erythrocytes; the number of erythrocytes and blood hematocrit will affect transport • Exercise: exercise prevents pooling of blood in the periphery, improves diaphragmatic excursion, and decreases the respiratory effort; the intake of oxygen can increase up to 20 times normal with vigorous exercise Carbon dioxide is transported from the cells to the lungs in three ways: • Bicarbonate (~65%) carried inside the RBC • Carboxyhemoglobin (30%) carbon dioxide combinedwith hemoglobin and carbonic acid (5%) • CO2 combined with water Intrapleural pressure is always slightly negative; pressure creates suction that holds visceral pleura and parietal pleura together. Intrapulmonary pressure equalizes with atmospheric pressure. Tidal volume is the degree of chest expansion during normal breathing, (~ 500mL/breath in adults). Heart Disease and strenuous exercise can cause more than 1500 mL to move with each breath. Lung Compliance is the stretching ability of lung tissue, which decreases with aging making an increased risk of atelectasis (a collapse of part of lung). Lung recoil is a continual tendency of the lungs to collapse away from the chest wall. Surfactant is a lipoprotein produced by alveolar cells, which reduces surface tension. Premature infants are not capable of producing adequate surfactant and may develop respiratory distress. Adult respiratory distress syndrome (ARDS ) may develop as a complication of illness or trauma. Alveolar gas exchange is the diffusion of oxygen from the alveoli and into the pulmonary blood vessels. Diffusion is movement of gases or other particles from an area of greater pressure or concentration to one of lesser pressure or concentration. Partial pressure is the pressure exerted by each gas in a mixture according to its concentration in the mixture. PO2