What is Nasal Cannula? Full guide

The term “Nasal Cannula” is a medical device used to deliver concentrated oxygen or increased airflow to a patient or person who needs respiratory help. For this purpose, oxygen face masks can also be used but in generally Nasal cannulas are used because they have the slimline shape which allows a patient to move around and to perform normal activities like eating, drinking or talking more effectively than with a face mask. Nasal cannulas are also cheap to replace and can rapidly be placed in most patients.

Patients who are receiving long-term oxygen therapy, they most commonly use a nasal cannula. The appliance is usually well tolerated, allowing normal speech, eating, and drinking. Cannulas can be used by combining with spectacle frames for convenience. For patients receiving long-term oxygen therapy, oxygen conserving cannulas combined with inlet reservoir are also available which are more comfortable. As oxygen flows continuously, almost 80% of the gas is wasted during expiration, so to avoid oxygen loss there are valved reservoirs that allow the storage of incoming gas or oxygen unless patient starts inhaling.

 

Purpose:

The basic purpose behind respiratory support is to provide the adequate ventilation properly. In this, it is ensured that proper alveolar ventilation is taking place so that expelling of excessive carbon dioxide that is produced in the human body can take place. At present, to ensure the proper alveolar ventilation and minute ventilation is handled skillfully while invasive or noninvasive ventilator support. Those patients having COPD with acute aggravation the noninvasive ventilation becomes most commonly used primary modality for respiratory support because it increases inspiratory tidal volume (VT) and maintains proper alveolar ventilation. Due to bad mask tolerance, however, becoming more popular as it is best substitute for respiratory support for any patient in critical situation. The equipment consists of an air blender, a humidifier and nasal cannula. In oxygen/air blender, the inhalator fraction of oxygen have to be set from 0.21 to 1.0 in a flow of up to 60 liters per minute. The gas is first heated and humidified using some active humidifier and then send through heated circuit. One of the other difference between noninvasive ventilation and High flow nasal cannula is the interface. While other interfaces for noninvasive ventilation increases anatomical dead space, that is for high flow nasal cannula actually reduces dead space. Inhalator push and expiratory pull both can be effective in such kind of open circuit, high flow nasal cannula cannot diligently enhance inspiratory tidal volume (VT). It helps COPD patients by increasing the pulmonary area through which gaseous exchange takes place and it also improves the total volume of gas entering the lungs per minute.

 

Policy Of Nasal Cannula:

Respiratory Care Services will provide all the equipment needed and the therapy according to doctor’s orders for the patient in need of supplemental oxygen to maintain proper and adequate blood levels of oxygen.

Nasal Cannulas which are ordered at 3 liters flow per minute, or less will be set up without humidification unless the doctor specifically orders it.

Nasal Cannula Oxygen therapy is assumed to be continuous unless physicians are prescribed to discontinue after checking / assessing the patient.

 

Goals of Nasal Cannula:

1. It is used to treat hypoxia (deficiency in reaching the total amount of oxygen to the body tissues) and hypoxemia (an abnormally low concentration of oxygen in the blood).
2. To decrease the work of breathing which is the energy expenditure in inhalation and exhalation of breathing gasses. Usually, it is expressed in work per unit volume.
3. To decrease myocardial workload, as there is low oxygen reaching the tissues of the body so to compensate this heart start for working more and pumps more blood to fulfill the oxygen requirement by tissues.

 

Structure:

It may be available as either a soft plastic tube with an over-the-ear head-elastic or dual-flow with under-the-chin lariat adjustment. It consists of two prongs on one side which are placed in nostrils and through these prongs a mixture of air and oxygen flows. The other side of the tube is connected to oxygen supply machine via a flowmeter. Flow rates of 1-5 liters per minute are used with nasal cannulas. Flow rates up to 6 liters can also be used, but it may cause dryness of nasal passages or discomfort to patients. Whenever flow rate more than 6 liters per minute is used, the laminar flow becomes turbulent and causes discomfort.

Different sizes of nasal cannulas are available for infants, children, and adults. In pediatrics, specially sized cannulas allow babies to nurse and produce less trauma of the face and nose than oxygen masks. Because of inherently reduced minute ventilation of infants, flow requirements, flow requirements to the cannula must be proportionately reduced. It usually needs a pressure-compensated flow meter accurate at delivering oxygen flows in less than 1–3 liters per minute range.

When A Nasal Cannula Should Be Used:

A nasal cannula is used whenever a patient or person requires supplementary oxygen as in cases of respiratory insufficiency like Chronic Obstructive Pulmonary Disease (COPD) or hypoxia i-e decreased delivery of oxygen to body tissues.

The nasal cannula can often be used in elderly patients or patients who can get benefit from oxygen therapy but do not require it because they do not want to self-respiration with oxygen therapy.

A nasal cannula can also be used by pilots of small aircraft having the unpressurized cabin and which flew in a low altitude zone. It gives extra oxygen to pilots to compensate for low oxygen available for breathing at the low ambient pressure at higher altitude so thus avoiding hypoxia. It can also be used in patients, where vasoconstriction of vessels can exacerbate their condition as in a case of Stroke.

It can also be used in high flow therapy. In it, a high flow of air is administered via nasal cannula to reach the demand of the patient. In this, the gas is warmed so that it can match the body temperature of the patient and it is humidified so that it can match with ideal body saturation vapor pressure.

Nasal cannula which uses humidified and heated gas can be used for air flows more than 6 liters per minute with no associated discomfort to the patient and it also have the additional benefit of better mucociliary clearance. A nasal cannula can also be used to level the myocardial workload.

 

When A Nasal Cannula Should Not Be Used:

Those patients who have Nasal blockage due to any reason for example in the case of the foreign body, fluid accumulation in nasal cavity due to infection of the nasal mucosa. Patient with facial injuries or facial trauma due to which it would be impossible to use the Nasal cannula. Patients those feel uncomfortable with Nasal Cannula.

Nasal cannulas deliver oxygen in an uncontrolled manner, which means that the amount of oxygen inhaled by a patient depends upon the patient’s breathing rate and the pattern of breathing. So, for this reason, these cannulas are not suitable for those patients in which controlled oxygen therapy is required.

In acute illnesses like acute exacerbations of COPD, controlled oxygen therapy is needed, so, in this case, nasal cannulas are not used.

Who Can Administer Nasal Cannula?

• Professional physicians.
• Professional Nurses.
• Trained Workers.

How to Apply Nasal Cannula:

1. Equipment Required:
2. Oxygen source.
3. Humidifier.
4. Distilled Water.
5. Flowmeter.
6. The sign is showing “No Smoking.”

Procedure:

• First of all, check patient’s medical record for details of doctor order to avoid potential errors.

To perform this procedure we should need a physician order which must include the following:

1. Liter flow of oxygen i-e how much flow you should be needed to provide the patient.
2. For Adults, it should be 1-6 L/min
3. For Neonatal/ Pediatric it should be – 0.1-5 L/min
4. Specified FIO2 for a blender when being used to feed neonatal patients other than mother’s milk.
5. Mode of administration.
6. If the order is incomplete, then nasal cannula oxygen therapy will be administered if there is an emergency. The order should be checked as soon as possible after an emergency administration has occurred. Otherwise, the complete order must be checked as you get the first contact with the patient and after that the oxygen therapy should be administered.

• Wash your hands to avoid transmission of germs.
• Explain procedure to the patient. Tell the patient that oxygen will ease dyspnea or discomfort, and inform the client about safety precautions that are associated with oxygen use. Moreover, encourage the patient to take breathe through the nose. Ask removal of all smoking materials. Observe the room for possible safety hazards.
• Assist patient to semi Fowler’s position to facilitate optimal lung expansion.
• Insert flowmeter to a wall outlet. Now attach oxygen tubes to the flowmeter. For high flow attach humidifier. Flowmeter should be turned off while plugging into the outlet.
• Turn on the oxygen at the rate required. Check that oxygen is flowing through tubes.
• Hold down the nasal cannula in a proper position in such a way that prongs in a downward curve.
• Place cannula prongs into the nostrils.
• Wrap the tubing over and behind the ears to support.
• Now adjust the plastic slide under the chin until cannula fits properly.
• Place gauze at the ear underneath the tubing.
• If prongs dislodge from the nostrils, correct their position quickly to ensure proper oxygen delivery and to prevent hypoxia.
• Now assess the smooth functioning of the apparatus and check the initial response of the patient to oxygen therapy.
• Assessment can be done clinically by checking the color of skin, alertness of the patient, respiratory rate/ breathing rate per minute, work of breathing, pulse rate, and blood pressure.
• Monitor continuous therapy by assessing for pressure areas on the skin and nares every 2 hours and by rechecking flow rate every 4 to 8 hours.

 

Discontinuation of Nasal Cannula:

The patient should be evaluated for round about 72 hours. Patient’s vitals should be assessed during this period. A complete evaluation about respiration should be done after every 72 hours. Based on these evaluations and results the doctor should make the decision whether to continue the therapy and discontinue.

 

Assessment Of The outcome:

It can be done by taking the Arterial blood gas and mixed venous blood gas measurements. It can be done clinically by checking color of skin, alertness of the patient, respiratory rate/ breathing rate per minute, work of breathing, pulse rate, and blood pressure.

Pulse Oximeter: An oximeter is that measures the ratio of oxygenated Hb in the blood in pulsating vessels, especially it is checked in the capillaries of the finger or ear.

What to Tell the Patient About Nasal Cannula:

• The physician should instruct the patient about the nasal cannula as follows:
• Explain to the patient that why he/she is receiving oxygen therapy and relate this procedure to his/her condition.
• Clear the doubts of the patient that this is a safe method and this procedure is for the safety of the patient.
• Tell the patient that he/she can remove this nasal oxygen device only with physician order otherwise, it may be harmful.
• Instruct patient in safe use of oxygen.

Conclusion:

Nasal cannula oxygen delivery is proving to be a valuable aid to medical industry. It has been becoming more popular as an alternative means of respiratory support for seriously ill patients. Doctors have been using it for patients with a variety of underlying diseases. It seems to be more effective for treating those respiratory disorders in which there is carbon dioxide retention and mild to moderate hypoxemic respiratory failure. However, some important things remain to be resolved such as the indication of high flow nasal cannula and criteria for timing the start of a high flow nasal cannula, for stopping high flow nasal cannula, and for escalating treatment. As high flow nasal cannula is noninvasive, the positive end-expiratory pressure level is not measured. Despite these factors, a growing level of evidence suggests that high flow nasal cannula oxygen therapy is an advanced and effective modality for the early treatment of adults with respiratory failure which is associated with various underlying diseases.