Forms Of Oxygen Administration

Oxygen Delivery Systems:

Compressed oxygen tanks, liquid oxygen tanks and oxygen concentrators.

Oxygen can be delivered from the delivery system to the patient in either low or high flow. Low flow systems use nasal cannula and masks reservoir, while masks with Venturi system are used under high flow systems.

Nasal cannulas or cannula. 

These are introduced in the nasal cavities (nostrils) and are inhaled using the normal nose breathing function. The exact amount of oxygen utilized cannot be defined exactly as there is a certain mix with ambient air, so the flow of oxygen is regulated to produced the needed amount. They can also be used even if the patient's breathing is predominantly oral, as it has been shown that a small but sufficient amount of oxygen is able to enter the respiratory system.

Face masks are also used by patients when sleeping if the tend to breath through their mouths.

Currently there are systems regulating oxygen, which aim to improve the efficiency of oxygen delivery, reducing its loss during exhalation, thereby reducing the cost by 25-50%. Continuous flow wastes oxygen as it is delivered constantly, even while breathing out. Some have a reservoir that collects oxygen during exhalation. Others are able to detect respiratory pressures and so are active only during inspiration.

Reservoir masks. 

In these masks there is a reservoir that accumulates sufficient oxygen to allow inspiratory flow demand of the patient who requires ventilation. The most widely used reservoir mask has three one-way valves that prevent the recirculation of exhaled gas: one located between the reservoir and the mask, which allows O2 pass from the reservoir during inspiration, but prevents the exhaled gas to mixed with the O2 reservoir during expiration. The other two, located on each side of the mask, allowing exhaled gas to exit into the atmosphere during exhalation while preventing ambient air entering during inhalation that could reduce the oxygen flow. These masks are used in hypoxemic respiratory failure because they allow the contribution of high concentrations of O2, but they are clearly inappropriate in hypercapnic patients, whose condition is aggravated by excessive administration of O2.

Masks with Venturi System. 

The oxygen enters the mask through a small hole at high speed, drawing air from the side doors. The final mixture reaches a flux ~ 40 L / min, which if excessive is removed through the side openings of the mask. These masks are uncomfortable, but have the advantage of ensuring a constant flow, not withstanding the breathing variations of the patient or if the breath is oral.

These masks deliver a gas where high flow oxygen concentrations can be adjusted between 24-50% FIO2. When oxygen passes through the narrow inlet the air velocity increases and drag the side doors. The amount of air entering the mask will depend on the flow of O2 and the opening of the doors, and determine the amount of inspired oxygen. This air-O2 mixture reaches a flow rate of 40 L / min and is sufficient to meet the ventilatory demands of the majority of patients with acute respiratory failure.

If the flow were to be excessive, there are escape hatches escapes through vents located on each side of the mask. On rare occasions when ventilatory demand is greater than 40 L / min, the patient can take ambient air through these openings.

 Masks with Venturi system are commonly used in two situations:

  * When hypoxia is risky and requires high and stable levels of O2.
  * When there is retention of CO2 in respiratory failure and accurate concentrations of oxygen should be administered.

Oxygen Humidification System

Oxygen gas is dry and can affect the mucus linings. The oxygen provided by the different methods is dry, so it is advisable to add water vapor prior to contact with the airways to prevent them drying out and producing secretions. The need for humidification is very critical when the gas flow rate is greater than 5 L / min or in intubated patients.

The types of humidifiers available for oxygen therapy are basically:

Bubble humidifiers. In these systems, humidification is achieved by passing the gas through water. The bubbles increase the air/liquid interface. These are commonly used humidifiers, typically for masks and nasal cannulas.

Cascade humidifiers. The oxygen travels down a tower and passes through a grid into a chamber of heated water. The displaced water rises above the grid, forming a liquid film that is converted to a froth as the gas also rises from the chamber through the grid. The process results in an airflow that can have a relative humidity of up to 100%. Preferably used for humidification of gases administered at high flow, especially in mechanical ventilators.

Indications For Oxygen Therapy

Oxygen therapy is used for both acute and chronic situations.

Acute situations are basically medical emergencies where there is respiratory insufficiency, hypoxia or where, in the absence of hypoxia, oxygen is needed to ensure proper tissue oxygen delivery, such as the shock from any cause, myocardial infarction, cerebral vascular accident, etc..

Chronic situations has important beneficial and has been proved to prolong survival. However, this effect has only been demonstrated in patients with COPD. In the other causes of chronic respiratory failure during its use O2 (interstitial disease, neuromuscular disease, other chronic airflow limitation) the beneficial effects are mainly symptomatic, decreased dyspnea, increased exercise capacity, as well sleep improvement sleep and better quality of life. The criteria used to provide continuous chronic use of oxygen are more or less universal.

Oxygen Administration Related Articles

Lungs, Oxygen and Carbon Dioxide 

The breathing process - the lungs, the oxygen add the carbon dioxide.  "In with the good air, out with the bad air".