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Keywords: Breathing/Oxygen/ Nursing Practice Oxygen therapy/Respiratory care Practice educator ●This article has been double-blind Respiratory care peer reviewed Oxygen therapy can be lifesaving but nurses must know how it works, when to use it, and how to correctly assess and evaluate a patient’s treatment Practical procedures: oxygen therapy

In this article... 5 key The rationale for using oxygen therapy in acute illness points Hypoxia is an Available oxygen delivery devices and indications for use 1indication that The need for monitoring while administering oxygen therapy oxygen therapy should be started If blood Author Sandra Olive, respiratory nurse hypoxaemia (low blood oxygen levels); 2oxygen levels specialist, Norfolk and Norwich University » Prescribing a target oxygen are not low, oxygen Hospitals Foundation Trust. saturation range to guide will not treat Abstract Olive S (2016) Practical therapeutic treatment. breathlessness procedures: oxygen therapy. Oxygen does not treat breathlessness in A target Nursing Times; 112: 1/2, 12-14. the absence of hypoxaemia (O’Driscoll et 3oxygen Knowing when to start patients on oxygen al, 2008). saturation range therapy can save lives, but ongoing In an emergency situation, immediate should be assessment and evaluation must be assessment of airway patency, breathing prescribed to carried out to ensure the treatment is safe and circulation is essential, and in critical guide therapy and effective. This article outlines when illness such as peri-arrest, high-concentra- A lower target oxygen therapy should be used and the tion oxygen should be commenced via res- 4saturation procedures to follow. It also describes the ervoir mask at 10-15L/min if the patient is range should be delivery methods applicable to different hypoxic, with continuous monitoring of prescribed for patient groups, along with the appropriate pulse oximetry and prescription of an patients at risk of target saturation ranges, and details appropriate target range once the patient’s hypercapnia relevant nurse competencies. condition is stabilised (Resuscitation The amount of Council (UK), 2015). 5oxygen xygen is required by all tissues The target saturation range is pre- received by the to support cell metabolism; in scribed according to the risk of type 2 patient is acute illness, low tissue oxy- (hypercapnic) respiratory failure pending dependent on the Ogenation (hypoxia) can occur arterial blood gas measurement. For most delivery device due to a failure in any of the systems that patients, a target of 94-98% is appropriate. used; ensure deliver and circulate oxygen. Hypoxia is an For those at risk of carbon dioxide reten- appropriate device indication to start oxygen therapy; this tion (hypercapnia), a target of 88-92% is selected can be a life-saving intervention, but ensures safe levels of oxygenation and given without appropriate assessment minimises risk of respiratory acidosis. and ongoing evaluation, it can also be Those at risk include patients with: FIG 1. Nasal cannula detrimental to patients’ health (Ridler et » Chronic obstructive pulmonary al, 2014). disease (emphysema); » Neuromuscular and chest wall Oxygen treatment disorders; When used as a medical treatment, oxygen » Cystic fibrosis; is regarded as a drug and must be pre- » Morbid obesity. scribed. In 2008, the British Thoracic Pulse oximetry must be available in all Society produced guidelines for its use settings where emergency oxygen is used. with acutely unwell adult patients It is essential to: (O’Driscoll et al, 2008). This was endorsed » Record inspired oxygen (FiO2), delivery by 21 professional groups across a wide device and oxygen saturations; range of professions and specialties. » Monitor and document the effect The guidelines recommend: of any changes to administered

Alamy » Administering oxygen to treat oxygen therapy.

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FIG 2. Fixed-performance devices Venturi valve mechanism Fixed-performance devices (also known as controlled oxygen delivery systems) Entrained air deliver a fixed proportion of air and oxygen via a Venturi valve, ensuring an accurate concentration of oxygen is delivered, regardless of inspiratory volumes and res- piratory rate (Fig 2). Fixed-performance devices should be

O2 used in acute illness in patients who are at

O2 + risk of carbon dioxide retention. Air Venturi valves (Fig 3) are colour-coded to denote the fixed percentage of oxygen delivered; these range from 24% (blue) to 60% (green), provided that the minimum oxygen flow rate on the barrel of the device is given. The minimum flow rate varies between Entrained air oxygen-mask manufacturers, so it is important to check the minimum rate that is recommended on the device in use. Delivery devices may build up in the mask. Simple face If patients are extremely breathless but Oxygen is delivered via variable-perfor- masks should not be used for patients at achieving adequate oxygen saturation mance or fixed-performance devices. risk of type 2 respiratory failure. rates, increasing the oxygen flow rate by 50% (for example, increasing from 2L/min Variable-performance devices Nasal cannulae to 3L/min) will increase the gas flow into The amount of oxygen delivered by vari- Nasal cannulae (Fig 1) are comfortable and the mask without increasing the per- able-performance devices (also known as well tolerated by most patients. They do centage of oxygen delivered, and may be uncontrolled oxygen systems) is not need to be removed when the patient is more comfortable for them. NT dependent on the: talking or eating. Oxygen is inhaled even » Oxygen flow rate; when breathing through the mouth. Nasal FIG 3. Venturi valves » Patient’s inspiratory volumes; cannulae are useful: » Respiratory rate; » For patients who are stable; » Proportion of room air added » To provide supplemental oxygen during breathing. therapy during meals; » To provide air-driven nebulised Reservoir mask (non-rebreathing mask) therapy for those requiring controlled Oxygen at 10-15L/min via a reservoir mask oxygen therapy. delivers oxygen at concentrations of They are commonly used to deliver 60-85% and is recommended for short- oxygen in the home setting. term use in patients who are critically ill. Flow rates above 4L/min can cause con- The reservoir bag must be filled with siderable drying of nasal mucosa and are oxygen before use and the mask positioned more difficult to tolerate. The FiO2 to ensure a close fit on the patient’s face. A achieved varies with the rate and depth of one-way valve prevents exhaled air breathing and, therefore, nasal cannulae entering the bag. should not be used in patients with Oxygen via a reservoir mask cannot be unstable type 2 respiratory failure. humidified, and patients will be more comfortable if they can be maintained within target range on a humidified FIG 4. Titrating oxygen up or down system once they are more stable. Venturi 24% 2-4L/min (blue) Nasal cannulae 1L/min Simple face mask The simple, or “low flow”, face mask is Venturi 28% 4-6L/min (white) Nasal cannulae 2L/min intended for short-term use, such as post- operative recovery. Oxygen is delivered at Venturi 35% 8-10L/min (yellow) Nasal cannulae 4-6L/min 2-10L/min and supplemented with air drawn into the mask during breathing. Venturi 40% 10-12L/min (red) Simple face mask 5-6L/min The FiO2 achieved cannot be predicted as it depends on the rate and depth of the Venturi 60% 12-15L/min (green) Simple face mask 7-10L/min patient’s breathing. Oxygen flow rates of <5L/min may result in the patient Reservoir mask at 15L/min rebreathing exhaled carbon dioxide, which

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Nursing Practice Practice educator

Box 1. Oxygen therapy procedure Starting oxygen therapy ● Help the patient to stay in an upright position to maximise The following procedure should be followed when starting ventilation unless contraindicated by underlying clinical oxygen therapy in patients who are acutely ill (not those in problems, for example, spinal or skeletal trauma peri-arrest): ● Give other prescribed therapies, such as nebulised ● Ensure pulse oximetry is available to monitor response to bronchodilation, diuretics, ventilatory support oxygen therapy ● Refer for respiratory physiotherapy if patients have difficulty ● Document baseline observations including saturations, clearing thick secretions respiratory rate, blood pressure and pulse ● Observe potential pressure areas, particularly behind the ears, ● Note respiratory effort, colour, level of consciousness from nasal cannula tubing or mask elastic and ensure skin is ● Check that there is a prescription for oxygen with a stated protected and pressure is relieved by altering the position of the target saturation range (except in peri-arrest situation) tubing or using padding ● Where there is no known risk of carbon dioxide retention ● Be aware of the drying effect of oxygen on oral and nasal (target 94-98%), start oxygen therapy using a reservoir mask at mucosa; encourage patients to maintain adequate oral fluid 10-15L/min. Where there is a risk of carbon dioxide retention intake where appropriate, and provide water-based lubricant (target 88-92%), start oxygen therapy using a 28% Venturi gel to relieve nasal drying. Do not use oil-based preparations device and mask such as Vaseline or petroleum jelly ● Ensure delivery device is connected via tubing to ● Consider discontinuing oxygen therapy once the patient has oxygen supply and turned on to the appropriate flow rate stable saturations (at least two consecutive recordings) within (if cylinder, check fill level of cylinder and be aware of their target range on low-dose oxygen (for example, 1-2L/min duration time) via nasal cannula). Monitor saturations for five minutes after ● Explain procedure to the patient and gain consent where stopping oxygen and recheck after one hour possible. In patients who are acutely sick, this may not be possible and clinicians should act in the patient’s best interests Competencies ● Place the oxygen mask on the patient’s face, adjusting the Basic nose clip and elastic straps to ensure a close fit ● Be aware of, and understand, local oxygen policy/guidelines ● Reassure the patient – if the patient is very breathless, oxygen ● Demonstrate a basic understanding of oxygen physiology, masks can feel very claustrophobic normal and abnormal values ● Monitor response to oxygen therapy – recheck oxygen ● Be able to discuss the indications for oxygen and the saturations, vital signs, colour and level of consciousness potential risks ● Titrate oxygen according to oxygen saturations (Fig 4) to ● Demonstrate an ability to use oxygen equipment safely, maintain saturations within prescribed target range. Allow five including an awareness of fire risks and cylinder use minutes at each dose before further adjustment. Sudden ● Demonstrate an ability to use a pulse oximeter to determine withdrawal of oxygen in a patient with hypercapnia leads to oxygen saturations rebound hypoxaemia ● Demonstrate accurate monitoring and recording of ● Document all adjustments to inspired oxygen (FiO2), with oxygen therapy saturations recorded ● Be able to recognise changes in a patient’s respiratory status ● Understand how to use oxygen in emergency situations, for Ongoing care of patients requiring oxygen therapy in the example, cardiac arrest acute setting ● Continue to monitor oxygen saturations at least four times a Registered nurses day. Always record saturations at rest and document FiO2 in situ Basic plus at the time ● Demonstrate an understanding of target range prescriptions ● Patients requiring >28% oxygen for more than 24 hours can and applications to different patient groups have oxygen delivered via a humidification system for comfort ● Demonstrate an ability to assess suitability of delivery devices and to avoid the drying of secretions for individual patients and recognise when a change of device ● Stable patients may be more comfortable with nasal cannulae is needed but care must be taken to ensure saturations remain in the ● Be able to correctly identify and set up a range of oxygen- target range delivery devices ● Patients requiring increasing doses of oxygen to maintain ● Understand how to select appropriate oxygen/driving gas for saturations within range, or with signs of respiratory nebulised therapy deterioration (increasing respiratory rate, drowsiness, headache, ● Demonstrate accurate recording of adjustments to the tremor, increasing early warning score) require prompt medical oxygen dose and the patient’s response review and further assessment including monitoring of arterial ● Recognise the need for escalation of treatment/medical blood gas review and further assessment

References Defibrillation. London: RCUK. O’Driscoll BR et al (2008) Guideline for Bit.ly/RCUKALSGuidance2015 For more on this topic go online... emergency oxygen use in adult patients. Ridler N et al (2014) Oxygen therapy in Delivering oxygen therapy Thorax; 63: (Suppl 6), vi1-vi68. critical illness. Friend or foe? A review of oxygen in acute care Resuscitation Council (UK) (2015) Adult Basic therapy in selected acute illnesses. Journal of Life Support and Automated External Intensive Care Society; 15: 3, 190-198. Bit.ly/NTAcuteOxygen

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