•OXYGEN DELIVERY SYSTEMS

•DR SHANKAR IYER•DNB Pulmonary

Medicine

WHAT IS OXYGEN DELIVERY SYSTEM

•An oxygen delivery system is a device used to administer, regulate, and supplement oxygen to a subject to increase the arterial oxygenation. •In general, the system entrains oxygen and air to prepare a fixed concentration required for administration. •Oxygen delivery systems are generally classified as low-flow or variable-performance devices and high-flow or fixed-performance devices.

INDICATIONS FOR OXYGEN THERAPY

• Peri and post cardiac or respiratory arrest.• Hypoxia - oxygen saturation levels of <92%.• Acute and chronic hypoxemia PaO2 < 65mmHg, SaO2 < 92%.• Signs and symptoms of shock.• Low cardiac output and metabolic acidosis HCO3 < 18mmol/l.• Chronic type two respiratory failure (hypoxia and hypercapnia).• Dyspnoea without hypoxemia.• Post-operatively, dependent on instruction from surgical team.• Treatment of pneumothorax.

DEFINITIONS• FiO2 is defined as the percentage or concentration of oxygen

that a person inhales. The air that we inhale on a day to day basis is made up of 21% of oxygen, 78% of nitrogen and 1% of trace elements such as argon, carbon dioxide, neon, helium and methane.

• Sometimes, 21% of oxygen may not be enough to maintain adequate oxygen saturations. In these situations, supplemental oxygen can be administered via various oxygen delivery devices ranging from nasal prongs to invasive ventilation.

• This allows the concentration of oxygen to be increased, potentially increasing the FiO2 to 100%.

SpO2

• SpO2 is an estimate of arterial oxygen saturation, or SaO2, which refers to the amount of oxygenated haemoglobin in the blood.

• Normal SpO2 95 – 100%

PaO2

• PaO2 is the partial pressure of oxygen dissolved in the blood, expressed in mmHg.

• If PaO2 is < 80 mmHg, the patient has arterial hypoxemia.

• 79 - 70 mmHg mild hypoxemia.• 69 - 60 mmHg= moderate hypoxemia• 59 - 50 mmHg = severe hypoxemia• < 50 mmHg = extreme hypoxemia

LOW FLOW OXYGEN DEVICES• These provide a fraction of the patient’s minute ventilatory requirement as

pure oxygen. • The remainder of the ventilatory requirement is filled by addition of

entrained room air. Flows supplied through these devices are low, usually less than 6L/min.

• These are oxygen devices where some room air will be entrained, and therefore the exact FiO2 cannot be calculated, however it can be estimated. How much FiO2 is delivered to the patient is dependent on: Liter flow set at the flowmeter, respiratory rate and pattern of the ad equipment reservoir.

• Nasal cannula, simple mask and oxygen conserving reservoir cannula are the most widely used devices for delivery of low flow oxygen.

• Simple, inexpensive, easy to use and well tolerated.

NASAL CANNULA

• Low-flow nasal cannulae set to deliver oxygen at flows between 1-6L/min lead to an FiO2 between 0.24 and 0.44.

• Flows above 6L/min do not significantly increase FiO2 above 0.44. These higher flows may result in drying of mucous membranes and nose bleed.

OXYGEN MASKS

• A simple mask is usually used for patients who require a moderate flow rate for a short period of time.

• It is composed of a plastic mask that fits snugly over the patient’s mouth and nose. The mask has holes on each side that are used for exhalation and for air entrainment if the flow rate is too low.

• Simple mask has the ability to deliver oxygen concentrations of 40% to 60% with flow rates from 6 to 10 L/min.

• Because carbon dioxide can build up in the mask at low flow rates, do not use a flow rate lower than 6 L/min with this type of mask. When using this mask, consider humidification to keep the patients’ mucous membranes from becoming dry.

RESERVOIR CANNULAS• Reservoir cannulas — Reservoir cannulas function by storing oxygen during exhalation,

making that oxygen available as a bolus upon the onset of the next inhalation. Reservoir cannulas are particularly useful in patients who require a flow rate of oxygen 4 L/min or higher.

• These cannulas are available in two configurations:• A moustache configuration in which the reservoir is located directly beneath the nose

and a pendant configuration in which oxygen is stored in a reservoir located on the anterior chest. The reservoir membrane is pushed forward during exhalation, creating a chamber. This enables oxygen to be stored during exhalation in the reservoir. When the patient is ready to inhale, he/she receives the stored oxygen along with the continuously flowing supply oxygen, increasing the percent oxygen in the air that the patient inhales.

• Both reservoir cannulas are simple, reliable, inexpensive, and disposable. They operate in response to the patient's nasal airflow.

• Both devices are partial rebreathing systems. As they return some of the patient's warmed expired air with elevated moisture, they effectively increase the relative humidity of the inhaled oxygen.

HIGH-FLOW OXYGEN DEVICES

• These devices meet the inspiratory flow of the patient, and generate accurate FiO2s so long as there is a good seal between the mask and the patient's face.

• The flows are such that the patient will not be entraining room air that will lower the FiO2.

• Respiratory rate and tidal volume of the patient have no effect on FiO2 delivered.

• These devices include venturi mask, partial and non-rebreather mask and high-flow cannulae or mask.

NON REBREATHER MASK

• This device is used to deliver high flow rates and high concentrations of oxygen. Like the simple mask, the nonrebreather mask fits snugly over the patient’s mouth and nose.

• A nonrebreather mask has ports on each side that have one-way valves that keep the patient from breathing in room air to ensure that a high concentration of oxygen is delivered.

• The mask also has a reservoir bag that is inflated with pure oxygen. Between the mask and the bag is another one-way valve that allows the patient to breathe in the oxygen supplied by the source as well as oxygen from the reservoir. This provides the patient with an oxygen concentration of nearly 100%.

• A nonrebreather mask can deliver oxygen concentrations of 60% to 95% with flow rates from 10 to 15 L/min. At flow rates slower than 6 L/min, the risk of rebreathing carbon dioxide increases.

PARTIAL REBREATHER MASK• A partial rebreather mask is used for oxygen therapy. It delivers

oxygen gas to the patient at concentrations of 50 to 70 percent.• This is basically an NRB with both one-way valves removed

from the mask. The estimated FiO2 is 60-65%. Flow should be set at 6-15 lpm.

• With a partial rebreather mask, when the patient inhales, they inhale some of the exhaled air, which contains carbon dioxide. When carbon dioxide enters the lungs, it stimulates breathing.

• In contrast, non-rebreather masks have vents on the side of the mask that allow all exhaled air to escape.

VENTURI MASK

• A Venturi mask is most often used for critically ill patients who require administration of a specific concentration of oxygen. It consists of a mask with holes on each side that allow exhaled air to escape. At the base of the mask are color-coded entrainment ports that are adjustable to allow regulation of the concentration of oxygen administered.

• A Venturi mask can deliver oxygen concentrations from 24% to 60% with flow rates from 4 to 12 L/min. Because this device delivers a precise oxygen concentration and carbon dioxide buildup is minimal, it is commonly used for patients who have COPD. Humidification is usually unnecessary with this device.

• There is entrainment of room air with these devices, but it is fixed and not dependent on the patient's PIFR. Therefore the resulting delivered FiO2 is also constant.

HIGH FLOW NASAL OXYGEN• High flow nasal oxygen therapy is a form of respiratory support where oxygen,

often in conjunction with compressed air and humidification, is delivered to a patient at rates of flow higher than that delivered traditionally in oxygen therapy. (Traditional oxygen therapy is up to 16 L/min and high flow oxygen therapy is up to 60 L/min.)

• HFNC can generate FiO2 100% and PEEP of up to 7.4 cmH20 at 60 L/min.• High flow oxygen therapy is usually delivered using a blender connected to a

wall outlet, a humidifier, heated tubing and nasal cannula. • It also creates nasopharyngeal dead space washout, thereby decreasing CO2

rebreathing and provides an oxygen reservoir.• It offers low levels of PEEP which may contribute to alveolar recruitment

(decreased dead space), improved compliance and decreased work of breathing.• Low level of patient compliance needed. Very comfortable and allows them to

communicate, eat.

HOME OXYGEN DELIVERY SYSTEMS

• Oxygen cylinders• Oxygen cylinders are the primary source for home oxygen portable

systems. The advantages of oxygen cylinders include the fact that they come in a variety of sizes, do not waste oxygen, they can have their duration increased with the use of a conserving device and can provide high liter flows. The disadvantages include often cumbersome size, limited duration, need for frequent refills and the high storage pressure of the gas (often up to 2000 psi).

• Home oxygen concentrators: • Home oxygen concentrators are compressors that use a molecular

sieve material to remove the nitrogen from room air and provide oxygen concentrations of 85-97% pure oxygen. These concentrators can provide liter flows from 0.5l/min to 10l/min. Recent advances have allowed concentrators to become more portable, functioning on internal batteries, automobile adaptors or standard electricity. Portable oxygen concentrators are approved for airline travel.

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