Chronic obstructive pulmonary disease
Description
An in-depth report on the causes, diagnosis, treatment, and prevention of COPD -- emphysema and/or chronic bronchitis.
Alternative Names
COPD; Alpha-1 antitrypsin deficiency; Bronchitis - chronic; Chronic bronchitis; Emphysema
Oxygen-Replacement Therapy
Eventually, lung function may worsen to the point that patients may need to rely on supplemental oxygen provided through portable or stationary tanks.
Continuous Therapy.
Continuous oxygen therapy (more than 15 hours a day) is the only treatment for emphysema that has been proven to prolong survival in certain patients. It also improves alertness, motor speed, and hand strength. Usually continuous oxygen therapy is recommended for patients under the following circumstances:
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Lung oxygen level is below 55 mm/Hg while the patient is resting.
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Resting oxygen level is less than 60 mm/Hg, and the patient has right heart failure or an abnormal increase in red blood cells.
The patient should receive enough oxygen to keep the oxygen level at 65 mm/Hg ideally, but at no less than 60 mm/Hg, or at an oxygen saturation level of at least 90%. Additional oxygen flow may be needed during sleep or exertion (physical activity).
About 40% of patients improve enough in 1 month to stop continuous treatment, although such patients should be observed closely. COLD frequently deteriorates, requiring reinstitution of oxygen therapy. Some patients worsen in spite of treatment, although at this point it is not possible to predict who is at risk for oxygen therapy failure. The addition of nitric oxide, a gas that dilates blood vessels, may offer additional benefits.
Intermittent Oxygen.
Patients with less severe COLD who are not on permanent oxygen maintenance may need supplemental oxygen during specific circumstances:
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Patients whose oxygen level drops below 55 mm/Hg only while exercising may benefit from supplemental oxygen during physical activity. Supplemental oxygen does not necessarily improve exercise performance, but it does enhance delivery of oxygen to the muscles while they are working.
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Oxygen may be needed at night for patients whose oxygen level drops below 55 mm/Hg during sleep. Such patients usually experience fitful, poor-quality sleep. This type of oxygen therapy does not appear to affect survival or to delay prescription of continuous oxygen therapy.
Oxygen During Travel.
People on continuous oxygen therapy who are traveling by plane should increase their oxygen by one to two liters per minute during the trip. Supplemental oxygen may be required during air travel for those with COLD who are on intermittent oxygen therapy. This happens if the trip is longer than 2 hours and they develop symptoms, or if they experience a drop in oxygen levels before travel. People are not allowed to bring their own tanks on board an airplane; many airlines (unfortunately, not all) will provide oxygen if notified between 48 and 72 hours in advance. A 1999 study reported that costs for in-flight oxygen ranged from $64 to $1,500. It should be noted, however, that aircraft cabins are actually pressurized to the equivalent of 8,000 feet above sea level. (Most people believe they are pressurized to sea level.) Such pressures could be potentially dangerous for people with severe COLD.
Oxygen Storage and Delivery Systems
Unless they are bed bound, patients usually use a combination of stationary and mobile oxygen systems.
Stationary Systems.
The most common stationary oxygen system is the concentrator, an electrical device that extracts oxygen from the air. It weighs about 35 pounds and cannot be battery operated, so a patient can use it only at home.
Portable Units.
Portable units containing electronic oxygen-conserving devices weigh only a few pounds and can provide up to 8 hours of oxygen. As examples, some portable units weigh 6.5 lb with liquid oxygen supplies lasting 4 hours. Some weigh 9.5 lb with oxygen supply lasting 8 hours, when used at a flow rate of two liters per minute.
Compressed or Liquid Oxygen.
Oxygen can be administered in large stationary tanks or small portable ones, either as compressed gas or liquid oxygen. A container of liquid oxygen lasts four times longer than compressed gas of the same weight and is easier to fill. Liquid oxygen is very beneficial for patients who want to maintain an active life, although the tanks require occasional venting to release pressure, thereby wasting oxygen. They are also more expensive. For example, in some areas a stationary liquid oxygen system costs $3,500 compared to a compressed oxygen tank at $350.
Precautions.
Supplemental oxygen is a fire hazard, and some hotels and residences do not allow its use. No one should smoke near an oxygen tank, and tanks should be stored safely, secured to a wall and away from heaters and furnaces.
Devices for Administering Oxygen
Oxygen is usually administered in one of three ways: using a nasal canula, a transtracheal catheter, or an electronic demand device.
Nasal Canula.
Using a nasal canula, oxygen is delivered through a long, slender plastic tube that runs from the oxygen tank to small plastic prongs that fit in the nostrils. The tube can be very long when attached to a stationary tank in order to accommodate walking throughout a house, or relatively short when attached to a portable unit.
A reservoir pouch is a recent innovation added to this device that provides an extra rush of oxygen as a patient starts to inhale. This method is inexpensive and easy to use, but some patients are embarrassed by its appearance under their noses.
Transtracheal Oxygen.
Transtracheal oxygen is delivered directly into the windpipe (trachea) through a catheter tube implanted by a surgeon. The device is inconspicuous, and compliance is excellent. The initial cost is high, but over time expenses are reduced because of more efficient oxygen usage. Long-term complications may include infection, dislodgment, and blockage by mucus, which can be very serious. Complications of the procedure itself occur in 3% to 5% of cases and include lung spasms and uncontrollable coughing.
Electronic Demand Devices.
Electronic devices that sense the beginning of a breath and deliver a pulse of oxygen are also available, although they are complicated, expensive, and have a risk for mechanical failure. Newer units have a continuous flow bypass switch that allows delivery of oxygen if the battery has run down.
Continuous Positive Airflow Pressure (CPAP)
Continuous positive airflow pressure (CPAP) supplies a steady stream of air through a tube that connects to a small bedside machine. The patient wears a plastic mask, and the machine applies sufficient air pressure to prevent the tissues from collapsing during sleep. It is
not
an oxygen-delivery system, but is intended to improve airflow into the lungs. The device is sometimes uncomfortable, and noncompliance rates are high. Studies are mixed on its benefits, suggesting that certain patients, but not others, may be helped by it. More studies are needed. [For detailed information on this device,
see In-Depth
Report #65:
Sleep Apnea.]
Oxygen Delivery in Emergency Situations
In emergency situations, oxygen may be delivered to the patient in various ways:
Intubation.
When standard oxygen therapy does not meet the needs of the patient, endotracheal
intubation
may be required to deliver high concentrations of oxygen. With intubation, a tube is inserted down through either the nose or the mouth through which oxygen is administered.
Noninvasive Positive Pressure Ventilation (NPPV).
If the patient is able to breathe naturally, oxygen is delivered through a tube using a tightly fitted oxygen mask to maintain airway pressure during breathing. Experts now believe such devices should be first-line treatments (in addition to medications) for managing respiratory failure after an acute exacerbation. They allow the patient to communicate and drink fluids and are much better tolerated than nose or throat tubes. They cannot be used on patients with rapidly deteriorating disease, who are uncooperative, or who have facial structures that do not allow the mask to make a tight seal.
Mechanical Ventilation.
In very serious cases, such as acute respiratory failure, a mechanical ventilator takes over the function of breathing. The primary goal of ventilation is to eliminate carbon dioxide and restore a balanced exchange of gases with oxygen administration.
A variety of mechanical ventilators are currently in use. A 1999 study reported that mechanical ventilators that use small breaths of air reduced mortality rates by 25% compared to those that required larger breaths.
Unfortunately, most patients have a low tolerance for intubation, and the tubes are often removed prematurely because of discomfort. Painkillers, sedatives, or even muscle relaxants may be needed.
There are also several complications that cause removal of breathing tubes:
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Ejection of the tube after coughing
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Mucus plugging
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Bleeding
Removing ventilation tubes too early produces adverse events in nearly all such patients. A study found that patients may be able to go off the ventilator more quickly and safely if they are screened daily and encouraged to breathe spontaneously as soon as possible.
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Review Date: 4/28/2006
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Reviewed By: Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital
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