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NR 224 Exam 3 Study GuideChapter 40 Oxygenation
Oxygen
-Cardiac and respiratory systems supply the oxygen demands of the body
-Blood oxygenated through mechanisms (ventilation, perfusion, and transport of resp. gases)
Respiratory Physiology
-Exchange of respiratory gases occur between environment and blood
-Respiration is exchange of oxygen and carbon dioxide during cellular metabolism
-Airways in lungs transfer oxygen from atmosphere to alveoli-oxy. Is exchanged for carbon dioxide.
Structure and Function
-Intrapleural pressure is negative/less than atmospheric pressure (760 mmHg) at seal level
-Air flow into lungs, intrapleural pressure becomes more negative-sets pressure gradient between
atmosphere and alveoli
-Diaphragm and external intercostal muscles contract to create negative pleural pressure, increase size of
thorax for inspiration
3 Steps of Oxygenation (Ventilation, Perfusion, Diffusion)
Ventilation: process of moving gases into and out of the lungs.
-coordination of lung and thorax
-major inspiratory muscle of respiration is diaphragm
-innervated by phrenic nerve, exits the spinal cord at 4th cervical vertebra
Perfusion: ability of the cardiovascular system to pump oxygenated blood to tissues and return
deoxygenated blood to lungs
Diffusion: responsible for moving respiratory gases from one area to another by concentration gradients
-exchange of respiratory gases need organ, nerves, muscles to be intact. Central nervous system
needs to regulate the respiratory cycle
Work of Breathing
-the effort required to expand and contract the lungs
Inspiration: an active process, stimulated by chemical receptors in aorta
Expiration: passive process, depends on the elastic recoil properties of lungs
-requires little or no muscle work
Surfactant: chemical produced in the lungs to maintain the surface tension of the alveoli and keep them
from collapsing
-Patients with COPD lose the elastic recoil of the lungs and thorax, WOB increases
Atelectasis: collapse of the alveoli that prevents normal exchange of oxygen and carbon dioxide
Compliance-the ability of the lungs to distend or expand in response to increased intraalveolar pressure
-decreases in diseases such as pulmonary edema, interstitial and pleural fibrosis, and congenital or
traumatic structural abnormalities such as kyphosis or fractured ribs
,NR 224 Exam 3 Study Guide
Airway resistance-increase in pressure occurs as diameter of airways decreases from mouth/nose to
alveoli
-Disease causing airway obstruction such as asthma and tracheal edema increase airway resistance
-Airway resistance increases, amount of oxygen delivered to alveoli decreases
Lung Volumes
-Normal lung values are determine by age, gender, and height
Tidal Volume: amount of air exhaled after normal inspiration
Residual Volume: amount of air left in the alveoli after a full expiration
Forced vital capacity: maximum amount of air that can be removed from the lungs during forced
expiration
Respiration Gas Exchange
-Thickness of membrane affects rate of diffusion
-Increased thickness of membrane impedes diffusion, gases take longer to transfer across membrane
-Pulmonary Edema, Pulmonary Infiltrates, Pulmonary Effusion have thickened membrane, results
in slow diffusion, slow exchange of respiratory gases, decreased delivery of oxygen to tissues
Oxygen Transport
-Consists of lungs and cardiovascular system
-Delivery depends on amount of oxygen entering lungs (ventilation), blood flow to lungs and tissues
(perfusion), rate of diffusion, and oxygen-carrying capacity
Three things influence the capacity of the blood to carry oxygen: amount of dissolved oxygen in plasma,
amount of hemoglobin, tendency of hemoglobin to bind with oxygen
Hemoglobin: carrier for oxygen and carbon dioxide
-transports most oxygen 97%
-hemoglobin molecule combines with oxygen to form oxyhemoglobin
-oxyhemoglobin is reversible, which frees oxygen to enter tissues
Carbon Dioxide Transport
-product of cellular metabolism, diffuse into red blood cells and is rapidly hydrated into carbonic acid
(H2CO3)
-Dissociates into hydrogen and bicarbonate ions HCO-3
-Hemoglobin buffers hydrogen ion and HCO-3 diffuses into plasma
-Venous blood transports majority of carbon dioxide back to the lungs to be exhaled
Cardiovascular Physiology
-Cardiopulmonary physiology involves delivery of deoxygenated blood (high in carbon/low in oxy.) to the
right side of heart and then to lungs where it is oxygenated
-Oxygenated blood (high in oxygen/low in carbon) travels from lungs to the left side of heart and the
tissues
Structure and Function
-Right ventricle pumps deoxygenated blood through the pulmonary circulation
, NR 224 Exam 3 Study Guide
-Left ventricle pumps oxygenated blood through the systemic circulation
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