NURS 303 Oxygenation and Perfusion Summary

Oxygenation and Perfusion
Oxygen is necessary for normal metabolism and carbon dioxide is a waste product of this metabolism.
The primary function of the respiratory system is gas exchange which consists of obtaining O2 from the
atmosphere and removing CO2 from the blood. Air is taken in through the upper airways, through the
lower airways into the small bronchioles and alveoli within the lung tissue where gas exchange occurs. In
this way, the respiratory tract primarily has the conduction of air zone and the respiratory zone. The
diaphragm and other respiratory muscles within the chest wall play significant roles in ensuring air
conduction into the lungs

Physiology of Oxygenation
Oxygenation-WKHGHOLYHU\RIR[\JHQWRWKHERG\¶VWLVVXHVDQGFHOOVGHSHQGVXSRQWKHLQWHUSOD\RI
the pulmonary, hematologic and cardiovascular systems. Three steps in the process of
oxygenation are n, and . Ventilation is the process of moving gases
. Perfusion relates to the ability of the cardiovascular system to pump
. Diffusion is
responsible for m
For the exchange of respiratory gases to occur, the organs, nerves, and muscles of respiration
need to be intact; and the central nervous system needs to be able to regulate the respiratory
cycle.
The exchange of respiratory gases occurs between the environment and the blood. Gases move
into and out of the lungs through pressure changes. Intrapleural pressure is negative, or less than
atmospheric pressure. For air to flow into the lun
e, setting up a pressure gradient between the atmosphere and the alveoli. During
ventilation (external), the airways of the lung transfer oxygen from the atmosphere to the alveoli,
where the oxygen is exchanged for carbon dioxide. Through the alveolar capillary membrane,
oxygen transfers to the blood. In oxygen transport and delivery, at the cellular level (internal or
cellular respiration), in response to concentration gradient, oxygen diffuses from the blood to the
tissues while C02 moves from the tissues to the blood and the blood is reoxygenated by the
lungs. Thus, based on the pressure gradient, during internal or cellular respiration, oxygen
concentration of tissue fluid is lower than that of the blood to enable diffusion of oxygen into the
tissues and carbon dioxide into the blood.
Hemoglobin, the oxygen carrying protein of the RBCs transports oxygen (approximately 97%)
to the tissues. The hemoglobin molecule combines with oxygen to form oxyhemoglobin. The
formation of oxyhemoglobin is easily reversible, allowing hemoglobin and oxygen to dissociate
(deoxyhemoglobin), which frees oxygen to enter tissues. Reduced hemoglobin
(deoxyhemoglobin) combines with carbon dioxide, and the venous blood transports the majority
of carbon dioxide back to the lungs to be exhaled. Relaxation of the diaphragm and contraction
of the internal intercostal muscles allow air to escape from the lungs.


Oxygen carried in a sample of blood can be measured as:




Obizoba 2021 pg. 1

, The oxygen dissolved in plasma expressed as the Normal
Pa02
expressed as the percentage of oxygen that is
saturated with oxygen Normal saturation is
Factors Influencing Oxygenation
Any condition that affects respiratory muscles and cardiopulmonary functioning directly affects
WKHERG\¶VDELOLW\WRPHHWR[\JHQGHPDQGV Since hemoglobin carries the majority of oxygen to
tissues, anemia and inhalation of toxic substances decrease the oxygen-carrying capacity of
blood by reducing the amount of available hemoglobin to transport oxygen. Anemia (e.g., a
lower-than-normal hemoglobin level) is a result of decreased hemoglobin production, increased
red blood cell destruction, and/or blood loss leading to fatigue.
Any condition that reduces chest wall movement will result in decreased ventilation. If the
diaphragm is unable to descend fully with breathing, the volume of inspired air decreases,
delivering less oxygen to the alveoli and all tissues. With the decline of the concentration of
inspired oxygen, the oxygen-carrying capacity of the blood decreases. Decreases in the
re caused by upper or lower airway obstruction, which
limits delivery of inspired oxygen to alveoli. When there is low oxygen, the body attempts to
adapt to the increased carbon dioxide levels by increasing the rate and depth of respiration. The
patienW¶Vwork of breathing increases, and the patient eventually displays signs and symptoms of
hypoxemia.
Patients with pulmonary diseases are at greater risk for hypoxemia. Oxygenation decreases as a
direct consequence of chronic lung disease. Changes in the anteroposterior diameter of the chest
wall (barrel chest) occur because of overuse of accessory muscles and air trapping as in
emphysema. The diaphragm is flattened, and the lung fields are over distended, resulting in
varying degrees of hypoxemia and/or hypercapnia.
Administering Cardiopulmonary resuscitation (CAB)
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cessation of cardiac output and circulation. When this occurs, oxygen is not delivered to tissues,
carbon dioxide is not transported from tissues, tissue metabolism becomes anaerobic, and
metabolic and respiratory acidosis occurs. Permanent heart, brain, and other tissue damage occur
within 4 to 6 minutes. Cardiopulmonary Resuscitation (CPR) is needed to restore circulation.
Recall the chest compressions, airway opening, breathing, and defibrillation with automatic
external defibrillator [AED] of CPR.




Obizoba 2021 pg. 2