Effect of oxygen on chronic obstructive pulmonary disease
Encyclopedia
In some individuals, the effect of oxygen on chronic obstructive pulmonary disease is to cause increased carbon dioxide retention
, which may cause drowsiness, headaches, and in severe cases lack of respiration, which may lead to death. People with lung ailments or with central respiratory depression, who receive supplemental oxygen, require careful monitoring.
content in the blood (hypercapnia
). This leads to drowsiness (narcosis), deranged acid-base balance
due to respiratory acidosis
, and death.
have a low partial pressure of oxygen in the blood. Treatment with supplemental oxygen may improve their well-being; alternatively, in some this can lead to the adverse effect of elevating the carbon dioxide content in the blood (hypercapnia
) to levels that may become toxic.
of 90%.
CO2 retention
CO2 retention is a pathophysiological process in which too little carbon dioxide is removed from the blood by the lungs. The end result is hypercapnia, an elevated level of carbon dioxide dissolved in the bloodstream. Various diseases may lead to this state; disturbed gas exchange may lead to...
, which may cause drowsiness, headaches, and in severe cases lack of respiration, which may lead to death. People with lung ailments or with central respiratory depression, who receive supplemental oxygen, require careful monitoring.
Signs and symptoms
In individuals with chronic obstructive pulmonary disease and similar lung problems, the clinical features of oxygen toxicity are due to high carbon dioxideCarbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
content in the blood (hypercapnia
Hypercapnia
Hypercapnia or hypercapnea , also known as hypercarbia, is a condition where there is too much carbon dioxide in the blood...
). This leads to drowsiness (narcosis), deranged acid-base balance
Acid-base imbalance
Acid–base imbalance is an abnormality of the human body's normal balance of acids and bases that causes the plasma pH to deviate out of the normal range . In the fetus, the normal range differs based on which umbilical vessel is sampled...
due to respiratory acidosis
Respiratory acidosis
Respiratory acidosis is a medical condition in which decreased ventilation causes increased blood carbon dioxide concentration and decreased pH ....
, and death.
Causes
Many people with chronic obstructive pulmonary diseaseChronic obstructive pulmonary disease
Chronic obstructive pulmonary disease , also known as chronic obstructive lung disease , chronic obstructive airway disease , chronic airflow limitation and chronic obstructive respiratory disease , is the co-occurrence of chronic bronchitis and emphysema, a pair of commonly co-existing diseases...
have a low partial pressure of oxygen in the blood. Treatment with supplemental oxygen may improve their well-being; alternatively, in some this can lead to the adverse effect of elevating the carbon dioxide content in the blood (hypercapnia
Hypercapnia
Hypercapnia or hypercapnea , also known as hypercarbia, is a condition where there is too much carbon dioxide in the blood...
) to levels that may become toxic.
Mechanism
In individuals with chronic obstructive pulmonary disease who receive supplemental oxygen, carbon dioxide accumulation may occur through three main mechanisms:- Ventilation/perfusion matching: under-ventilated lung usually has a low oxygen content which leads to localised vasoconstrictionVasoconstrictionVasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
limiting blood flow to that lung tissue. Supplemental oxygen abolishes this constriction, leading to poor ventilation/perfusionVentilation/perfusion ratioIn respiratory physiology, the ventilation/perfusion ratio is a measurement used to assess the efficiency and adequacy of the matching of two variables: It is defined as: the ratio of the amount of air reaching the alveoli to the amount of blood reaching the alveoli.* "V" – ventilation – the air...
matching. This redistribution of blood to areas of the lung with poor ventilation reduces the amount of carbon dioxide eliminated from the system. - The Haldane effectHaldane effectThe Haldane effect is a property of hemoglobin first described by the Scottish physician John Scott Haldane. Deoxygenation of the blood increases its ability to carry carbon dioxide; this property is the Haldane effect. Conversely, oxygenated blood has a reduced capacity for carbon...
: most carbon dioxide is carried by the blood as bicarbonate, and deoxygenated hemoglobinHemoglobinHemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
promotes the production of bicarbonate. Increasing the amount of oxygen in the blood by administering supplemental oxygen reduces the amount of deoxygenated hemoglobin, and thus reduces the capacity of blood to carry carbon dioxide. - Respiratory homoeostasis: in healthy individuals, a rise in carbon dioxide causes an increase in the drive to breathe. However in some patients with chronic obstructive pulmonary disease, this response has been blunted, leaving low oxygen levels as the main stimulus of respiration (hypoxic driveHypoxic driveThe hypoxic drive is a form of respiratory drive in which the body uses oxygen chemoreceptors instead of carbon dioxide receptors to regulate the respiratory cycle....
). Hence, giving supplemental oxygen reduces their stimulus to breathe, causing respiration to slow (hypoventilationHypoventilationIn medicine, hypoventilation occurs when ventilation is inadequate to perform needed gas exchange...
), and allowing carbon dioxide to accumulate in the body.
Prevention
In people with chronic obstructive pulmonary disease, carbon dioxide toxicity can be prevented by careful control of the supplemental oxygen. Just enough oxygen is given to maintain an oxygen saturationOxygen saturation
Oxygen saturation or dissolved oxygen is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor or an optode in liquid media, usually water.It has particular significance in medicine and...
of 90%.