Oxygen therapy
Oxygen therapy, also known as supplemental oxygen, is the use of oxygen as a medical treatment. This can include for low blood oxygen, carbon monoxide toxicity, cluster headaches, and to maintain enough oxygen while inhaled anesthetics are given. Long-term oxygen is often useful in people with chronically low oxygen such as from severe COPD or cystic fibrosis. Oxygen can be given in a number of ways including nasal cannula, face mask, and inside a hyperbaric chamber.
Oxygen is required for normal cell metabolism. Excessively high concentrations can cause oxygen toxicity such as lung damage or result in respiratory failure in those who are predisposed. Higher oxygen concentrations also increase the risk of fires, particularly while smoking, and without humidification can also dry out the nose. The target oxygen saturation recommended depends on the condition being treated. In most conditions a saturation of 94–96% is recommended, while in those at risk of carbon dioxide retention saturations of 88–92% are preferred, and in those with carbon monoxide toxicity or cardiac arrest they should be as high as possible. Air is typically 21% oxygen by volume while oxygen therapy increases this by some amount up to 100%.
The use of oxygen in medicine became common around 1917. It is on the World Health Organization's List of Essential Medicines. The cost of home oxygen is about US$150 a month in Brazil and US$400 a month in the United States. Home oxygen can be provided either by oxygen tanks or an oxygen concentrator. Oxygen is believed to be the most common treatment given in hospitals in the developed world.
Medical uses
Oxygen is used as a medical treatment in both chronic and acute cases, and can be used in hospital, pre-hospital or entirely out of hospital.Chronic conditions
A common use of supplementary oxygen is in people with chronic obstructive pulmonary disease, the occurrence of chronic bronchitis or emphysema, a common long-term effect of smoking, who may require additional oxygen to breathe either during a temporary worsening of their condition, or throughout the day and night. It is indicated in people with COPD, with arterial oxygen partial pressure Pa ≤ 55 mmHg or arterial oxygen saturation Sa ≤ 88% and has been shown to increase lifespan.Oxygen is often prescribed for people with breathlessness, in the setting of end-stage cardiac or respiratory failure, advanced cancer or neurodegenerative disease, despite having relatively normal blood oxygen levels. A 2010 trial of 239 subjects found no significant difference in reducing breathlessness between oxygen and air delivered in the same way.
Acute conditions
Oxygen is widely used in emergency medicine, both in hospital and by emergency medical services or those giving advanced first aid.In the pre-hospital environment, high-flow oxygen is indicated for use in resuscitation, major trauma, anaphylaxis, major bleeding, shock, active convulsions, and hypothermia.
It may also be indicated for any other people where their injury or illness has caused low oxygen levels, although in this case oxygen flow should be moderated to achieve oxygen saturation levels, based on pulse oximetry. Excessively use of oxygen in those who are acutely ill however increases the risk of death. In 2018 recommendations within the British Medical Journal were that oxygen should be stopped if saturations are greater than 96% and should not be started if above 90 to 93%. Exceptions were those with carbon monoxide poisoning, cluster headaches, attacks of sickle cell disease, and pneumothorax.
For personal use, high concentration oxygen is used as home therapy to abort cluster headache attacks, due to its vaso-constrictive effects.
People who are receiving oxygen therapy for low oxygen following an acute illness or hospitalization should not routinely have a prescription renewal for continued oxygen therapy without a physician's re-assessment of the person's condition. If the person has recovered from the illness, then the hypoxemia is expected to resolve and additional care would be unnecessary and a waste of resources.
Side effects
Many EMS protocols indicate that oxygen should not be withheld from anyone, while other protocols are more specific or circumspect. However, there are certain situations in which oxygen therapy is known to have a negative impact on a person's condition.Oxygen should never be given to a person who has paraquat poisoning unless they have severe respiratory distress or respiratory arrest, as this can increase the toxicity. Paraquat poisoning is rare with about 200 deaths globally from 1958 to 1978. Oxygen therapy is not recommended for people who have pulmonary fibrosis or other lung damage resulting from bleomycin treatment.
High levels of oxygen given to infants cause blindness by promoting overgrowth of new blood vessels in the eye obstructing sight. This is retinopathy of prematurity.
Oxygen has vasoconstrictive effects on the circulatory system, reducing peripheral circulation and was once thought to potentially increase the effects of stroke. However, when additional oxygen is given to the person, additional oxygen is dissolved in the plasma according to Henry's Law. This allows a compensating change to occur and the dissolved oxygen in plasma supports embarrassed neurons, reduces inflammation and post-stroke cerebral edema. Since 1990, hyperbaric oxygen therapy has been used in the treatments of stroke on a worldwide basis. In rare instances, people receiving hyperbaric oxygen therapy have had seizures. However, because of the aforementioned Henry's Law effect of extra available dissolved oxygen to neurons, there is usually no negative sequel to the event. Such seizures are generally a result of oxygen toxicity, although hypoglycemia may be a contributing factor, but the latter risk can be eradicated or reduced by carefully monitoring the person's nutritional intake prior to oxygen treatment.
Oxygen first aid has been used as an emergency treatment for diving injuries for years. Recompression in a hyperbaric chamber with the person breathing 100% oxygen is the standard hospital and military medical response to decompression illness. The success of recompression therapy as well as a decrease in the number of recompression treatments required has been shown if first aid oxygen is given within four hours after surfacing. There are suggestions that oxygen administration may not be the most effective measure for the treatment of decompression illness and that heliox may be a better alternative.
Chronic obstructive pulmonary disease
Care needs to be exercised in people with chronic obstructive pulmonary disease, such as emphysema, especially in those known to retain carbon dioxide. Such people may further accumulate carbon dioxide and decreased pH if administered supplemental oxygen, possibly endangering their lives. This is primarily as a result of ventilation–perfusion imbalance. In the worst case, administration of high levels of oxygen in people with severe emphysema and high blood carbon dioxide may reduce respiratory drive to the point of precipitating respiratory failure, with an observed increase in mortality compared with those receiving titrated oxygen treatment. However, the risk of the loss of respiratory drive are far outweighed by the risks of withholding emergency oxygen, and therefore emergency administration of oxygen is never contraindicated. Transfer from field care to definitive care, where oxygen use can be carefully calibrated, typically occurs long before significant reductions to the respiratory drive.A 2010 study has shown that titrated oxygen therapy is less of a danger to people with COPD and that other, non-COPD people, may also, in some cases, benefit more from titrated therapy.
Fire risk
Highly concentrated sources of oxygen promote rapid combustion. Oxygen itself is not flammable, but the addition of concentrated oxygen to a fire greatly increases its intensity, and can aid the combustion of materials which are relatively inert under normal conditions. Fire and explosion hazards exist when concentrated oxidants and fuels are brought into close proximity; however, an ignition event, such as heat or a spark, is needed to trigger combustion. A well-known example of an accidental fire accelerated by pure oxygen occurred in the Apollo 1 spacecraft in January 1967 during a ground test; it killed all three astronauts. A similar accident killed Soviet cosmonaut Valentin Bondarenko in 1961.Combustion hazards also apply to compounds of oxygen with a high oxidative potential, such as peroxides, chlorates, nitrates, perchlorates, and dichromates because they can donate oxygen to a fire.
Concentrated will allow combustion to proceed rapidly and energetically. Steel pipes and storage vessels used to store and transmit both gaseous and liquid oxygen will act as a fuel; and therefore the design and manufacture of systems requires special training to ensure that ignition sources are minimized. Highly concentrated oxygen in a high-pressure environment can spontaneously ignite hydrocarbons such as oil and grease, resulting in fire or explosion. The heat caused by rapid pressurization serves as the ignition source. For this reason, storage vessels, regulators, piping and any other equipment used with highly concentrated oxygen must be "oxygen-clean" prior to use, to ensure the absence of potential fuels. This does not apply only to pure oxygen; any concentration significantly higher than atmospheric carries a potential risk.
Hospitals in some jurisdictions, such as the UK, now operate "no-smoking" policies, which although introduced for other reasons, support the aim of keeping ignition sources away from medical piped oxygen. Recorded sources of ignition of medically prescribed oxygen include candles, aromatherapy, medical equipment, cooking, and unfortunately, deliberate vandalism. Smoking of pipes, cigars, and cigarettes is of special concern. These policies do not entirely eliminate the risk of injury with portable oxygen systems, especially if compliance is poor.
Alternative medicine
Some practitioners of alternative medicine have promoted "oxygen therapy" as a cure for many human ailments including AIDS, Alzheimer's disease and cancer. The procedure may include injecting hydrogen peroxide, oxygenating blood, or administering oxygen under pressure to the rectum, vagina, or other bodily opening. According to the American Cancer Society, "available scientific evidence does not support claims that putting oxygen-releasing chemicals into a person's body is effective in treating cancer", and some of these treatments can be dangerous.Storage and sources
Oxygen can be separated by a number of methods, including chemical reaction and fractional distillation, and then either used immediately or stored for future use. The main types of sources for oxygen therapy are:- Liquid storage – Liquid oxygen is stored in chilled tanks until required, and then allowed to boil to release oxygen as a gas. This is widely used at hospitals due to their high usage requirements, but can also be used in other settings. See Vacuum Insulated Evaporator for more information on this method of storage.
- Compressed gas storage – The oxygen gas is compressed in a gas cylinder, which provides a convenient storage, without the requirement for refrigeration found with liquid storage. Large oxygen cylinders hold and can last about two days at a flow rate of 2 litres per minute. A small portable M6 cylinder holds and weighs about. These tanks can last 4–6 hours when used with a conserving regulator, which senses the person's breathing rate and sends pulses of oxygen. Conserving regulators may not be usable by people who breathe through their mouths.
- Instant usage – The use of an electrically powered oxygen concentrator or a chemical reaction based unit can create sufficient oxygen for a person to use immediately, and these units are in widespread usage for home oxygen therapy and portable personal oxygen, with the advantage of being continuous supply without the need for additional deliveries of bulky cylinders.
Delivery
Low-dose oxygen
Many people only require a slight increase in oxygen in the air they breathe, rather than pure or near-pure oxygen. This can be delivered through a number of devices dependent on the situation, the flow required and in some instances person's preference.A nasal cannula is a thin tube with two small nozzles that protrude into the person's nostrils. It can only comfortably provide oxygen at low flow rates, 2–6 litres per minute, delivering a concentration of 24–40%.
There are also a number of face mask options, such as the simple face mask, often used at between 5 and 8 LPM, with a concentration of oxygen to the person of between 28% and 50%. This is closely related to the more controlled air-entrainment masks, also known as Venturi masks, which can accurately deliver a predetermined oxygen concentration to the trachea up to 40%.
In some instances, a partial rebreathing mask can be used, which is based on a simple mask, but featuring a reservoir bag, which increases the provided oxygen concentration to 40–70% oxygen at 5–15 LPM.
Non-rebreather masks draw oxygen from attached reservoir bags, with one-way valves that direct exhaled air out of the mask. When properly fitted and used at flow rates of 8–10 LPM or higher, they deliver close to 100% oxygen. This type of mask is indicated for acute medical emergencies.
Demand oxygen delivery systems or oxygen resuscitators deliver oxygen only when the person inhales, or, in the case of a non-breathing person, the caregiver presses a button on the mask. These systems greatly conserve oxygen compared to steady-flow masks, which is useful in emergency situations when a limited supply of oxygen is available and there is a delay in transporting the person to higher care. They are very useful in performing CPR, as the caregiver can deliver rescue breaths composed of 100% oxygen with the press of a button. Care must be taken not to over-inflate the person's lungs, and some systems employ safety valves to help prevent this. These systems may not be appropriate for people who are unconscious or those in respiratory distress, because of the effort required to breathe from them.
High flow oxygen delivery
In cases where the person requires a high concentration of up to 100% oxygen, a number of devices are available, with the most common being the non-rebreather mask, which is similar to the partial rebreathing mask except it has a series of one-way valves preventing exhaled air from returning to the bag. There should be a minimum flow of 10 L/min. The delivered FIO2 of this system is 60–80%, depending on the oxygen flow and breathing pattern.Another type of device is a humidified high flow nasal cannula which enables flows exceeding a person's peak inspiratory flow demand to be delivered via nasal cannula, thus providing FIO2 of up to 100% because there is no entrainment of room air, even with the mouth open. This also allows the person to continue to talk, eat and drink while still receiving the therapy. This type of delivery method is associated with greater overall comfort, and improved oxygenation and respiratory rates than with face mask oxygen.
In specialist applications such as aviation, tight-fitting masks can be used, and these also have applications in anaesthesia, carbon monoxide poisoning treatment and in hyperbaric oxygen therapy
Positive pressure delivery
People who are unable to breathe on their own will require positive pressure to move oxygen into their lungs for gaseous exchange to take place. Systems for delivering this vary in complexity, starting with a basic pocket mask adjunct which can be used by a basically trained first aider to manually deliver artificial respiration with supplemental oxygen delivered through a port in the mask.Many emergency medical service and first aid personnel, as well as hospitals, will use a bag-valve-mask, which is a malleable bag attached to a face mask, usually with a reservoir bag attached, which is manually manipulated by the healthcare professional to push oxygen into the lungs. This is the only procedure allowed for initial treatment of cyanide poisoning in the UK workplace.
Automated versions of the BVM system, known as a resuscitator or pneupac can also deliver measured and timed doses of oxygen direct to people through a facemask or airway. These systems are related to the anaesthetic machines used in operations under general anaesthesia that allows a variable amount of oxygen to be delivered, along with other gases including air, nitrous oxide and inhalational anaesthetics.
As a drug delivery route
Oxygen and other compressed gasses are used in conjunction with a nebulizer to allow the delivery of medications to the upper and/or lower airways. Nebulizers use compressed gas to propel liquid medication into an aerosol, with specific therapeutically sized droplets, for deposition in the appropriate, desired portion of the airway. A typical compressed gas flow rate of 8–10 L/min is used to nebulize medications, saline, sterile water, or a mixture of the preceding into a therapeutic aerosol for inhalation. In the clinical setting room air, molecular oxygen, and Heliox are the most common gases used to nebulize a bolus or a continuous volume of therapeutic aerosols.Exhalation filters for oxygen masks
Filtered oxygen masks have the ability to prevent exhaled, potentially infectious particles from being released into the surrounding environment. These masks are normally of a closed design such that leaks are minimized and breathing of room air is controlled through a series of one-way valves. Filtration of exhaled breaths is accomplished either by placing a filter on the exhalation port or through an integral filter that is part of the mask itself. These masks first became popular in the Toronto healthcare community during the 2003 SARS Crisis. SARS was identified as being respiratory based and it was determined that conventional oxygen therapy devices were not designed for the containment of exhaled particles. Common practices of having suspected people wear a surgical mask was confounded by the use of standard oxygen therapy equipment. In 2003, the HiOx80 oxygen mask was released for sale. The HiOx80 mask is a closed design mask that allows a filter to be placed on the exhalation port. Several new designs have emerged in the global healthcare community for the containment and filtration of potentially infectious particles. Other designs include the ISO- oxygen mask, the Flo2Max oxygen mask, and the O-Mask. The use of oxygen masks that are capable of filtering exhaled particles is gradually becoming a recommended practice for pandemic preparation in many jurisdictions.Typical oxygen masks allow the person to breathe in room air in addition to their therapeutic oxygen, but because filtered oxygen masks use a closed design that minimizes or eliminates the person's contact with and ability to inhale room air, delivered oxygen concentrations to the person have been found to be higher, approaching 99% using adequate oxygen flows. Because all exhaled particles are contained within the mask, nebulized medications are also prevented from being released into the surrounding atmosphere, decreasing the occupational exposure to healthcare staff and other people.
Aircraft
In the United States, most airlines restrict the devices allowed on board aircraft. As a result, passengers are restricted in what devices they can use. Some airlines will provide cylinders for passengers with an associated fee. Other airlines allow passengers to carry on approved portable concentrators. However, the lists of approved devices varies by airline so passengers need to check with any airline they are planning to fly on. Passengers are generally not allowed to carry on their own cylinders. In all cases, passengers need to notify the airline in advance of their equipment.Effective May 13, 2009, the Department of Transportation and FAA ruled that a select number of portable oxygen concentrators are approved for use on all commercial flights. FAA regulations require larger airplanes to carry D-cylinders of oxygen for use in an emergency.