1. Assess the need for oxygen therapy
The most common reasons for oxygen therapy to be initiated are
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Acute hypoxemia (for example pneumonia, shock, asthma, heart failure, pulmonary embolism). |
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Ischemia (for example myocardial infarction, but only if associated with hypoxemia (abnormally high levels may be harmful to patients with ischemic heart disease and stroke). |
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Abnormalities in quality or type of hemoglobin (e.g., carbon monoxide poisoning). |
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Pneumothorax – Oxygen may increase the rate of resolution of pneumothorax. |
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Post-operative state (general anesthesia can lead to decrease in functional residual capacity with in the lungs. |
2. Assess for the complications of oxygen therapy
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Increases in carbon dioxide and respiratory acidosis in patient with carbon dioxide retention. |
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Drying of nasal and pharyngeal mucosa. |
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Oxygen toxicity. |
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Absorption atelectasis. |
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Skin irritation. |
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Fire hazard. |
3. Oxygen administration protocol
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Ensure patency of airway. |
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The type of delivery system used will depend on the needs and comfort of the patient. |
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All patients requiring oxygen therapy should have a prescription for oxygen therapy recorded on the patient’s prescription chart. |
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The prescription should incorporate a target saturation that will be identified by the clinician. |
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The oxygen delivery device and oxygen flow rate should be recorded alongside the oxygen saturation on the bedside observation chart. |
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Oxygen saturations must always be interpreted alongside the patient’s clinical status. |
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If the patient falls outside of the target saturation range, the oxygen therapy should be adjusted accordingly. |
4. Assessment of oxygen therapy
4.1. Pulse oximetry readings
Always keep in mind the following factors might affect the accuracy of pulse oximetry.
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Severe hypoxemia. |
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Carboxyhaemoglobin and methaemoglobin levels. |
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Dark skin. |
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Low perfusion. |
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Excessive ambient light. |
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Nail polish. |
4.2. Arterial blood gas (ABG)
Measurement of ABG should be considered in the following situations.
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Critically ill patients with cardiorespiratory or metabolic dysfunction. |
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In patients with an SpO 2 <92% in whom hypoxemia may be present. |
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Deteriorating oxygen saturation requiring increased FiO2. |
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Patients at risk of hypercapnia. |
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Breathless patients in whom a reliable oximetry signal cannot be obtained. |
5. Delivery system of Oxygen
5.1. Nasal Cannula (Low Flow/Common)
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Nasal cannula delivers oxygen at low gas flow 1-6 L/min with FiO 2 from 24-40%. |
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Best device for patient with high PCO 2 as there is no rebreathing. |
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High flow rates do not result in high FiO 2 and have a drying and irritating effect on nasal mucosa. |
Figure 1: Nasal cannula
5.2. Face Mask (Regular)
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Standard face masks deliver oxygen at flow rates of 5-10 L/min with FiO2of about 50%. |
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5 L/min is the minimum flow rate required to ensure CO 2 is flushed from the mask. |
Figure 2: Simple face mask
5.3. Nonrebreathing face mask with reservoir bag
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Nonrebreathing face mask with reservoir bag delivers oxygen at flow rates 10-15 L/min with maximum FiO 2 of 80%. |
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Delivery of oxygen is dependent on the patient inspiratory flow rates. |
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Do not attempt to wean the patient from this mask by reducing the oxygen flow rate. |
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To reduce the percentage of oxygen delivery, change the patient onto a Venturi mask. |
Figure 3: Nonrebreathing face mask with reservoir bag
5.4. Venturi mask
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Venturi masks are preferred for precise titration of oxygen being administered. |
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FiO 2 can be more precisely controlled from 0.24 to 0.6 at high flow rates simply by changing the jet nozzle and adjusting oxygen flow rates. (as mentioned) |
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There must be at least 6-inch-long corrugated tube between venturi device and mask for exact FiO2delivery. |
Figure 4: Venturi mask
5.5. High Flow Nasal Cannula (HFNC)
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HFNC delivers high inspiratory gas flow (up to 60 liters per minute), which is warmed and humidified. |
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HFNC may also improve patient comfort and compliance with the therapy. |
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HFNC allows the modification of only two variables: the percentage of oxygen being delivered and the rate of gas flow. |
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High flow nasal cannulation therapy may be beneficial in the following situations: ● Acute hypoxemic respiratory failure. ● Increased work of breathing. ● Preoxygenation before intubation. ● Acute COPD exacerbation. ● Severe pneumonia requiring high flow oxygen. ● Acute pulmonary edema. ● Post extubation support. ● Postoperative respiratory failure. ● In severely distressed do-not-resuscitate (DNR) patients. ● Patients with do-not-intubate (DNI) status and respiratory failure. |
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HFNC is contraindicated in following conditions: ● Nasal passage abnormalities or recent nasal surgery. ● Cerebro-spinal fluid leaks. ● Basal skull fractures. ● Severe epistaxis. ● Patients with type 2 respiratory failure requiring Non-invasive ventilation (NIV). ● Need immediate mechanical ventilation. |
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Signs of Failure of HFNC (one of the following) ● Worsening or non-improvement of oxygenation. ● Increased FiO2while target SpO 2 is not achieved. ● Increased work on breathing. ● Worsening or non-improvement of ventilation and/or work of breathing. ● Respiratory rate is worsening or not improving. ● Thoraco-abdominal asynchrony worsening or not improving. ● Clinical signs of exhaustion. ● PaCO2worsening or not improving. ● pH worsening or not improving. |
Steps of setting the HFNC parameters and further adjustment:
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Initial setup: ● Set Humidity as close to 37° as possible and titrate to affect airway hydration and patient comfort. ● Start with high flow rates (50-60 L/min) and titrate to affect Respiratory Rate (RR) and patient comfort. ● Set FiO 2 between 0.21 to 1.0 and titrate to affect SpO 2 (within target range). ● When increasing support is needed, move flow up first then Oxygen. ● When reducing support, move Oxygen down first then flow. |
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The flow rate should be increased if: ● Respiratory rate fails to improve. ● Oxygenation fails to adequately improve. ● Breathing remains labored. |
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Weaning of HFNC: ● When O 2 goals are achieved and the patient is clinically improving (decrease in respiratory rate and respiratory distress): reduce FiO2gradually by 5-10% every 2-4 hours. ● When FiO 2 ≤ 40% is reached, flow can be gradually reduced by 5-10 L/min every 2-4 hours. ● Switching to conventional O2 therapy should be considered when FiO 2 < 35% and flow <20 L/min. |
Further Readings:
1. Walters, H., Beasley, R. W., Chien, J., Douglas, J., Eastlake, L., Farah, C., ... & Smith, S. (2015). Thoracic Society of Australia and New Zealand oxygen guidelines for acute oxygen use in adults:'Swimming between the flags'.
2. O'driscoll, B. R., Howard, L. S., Earis, J., & Mak, V. (2017). BTS guideline for oxygen use in adults in healthcare and emergency settings. Thorax, 72(Suppl 1), ii1-ii90.
3. Oczkowski, S., Ergan, B., Bos, L., Chatwin, M., Ferrer, M., Gregoretti, C., ... & Scala, R. (2022). ERS clinical practice guidelines: high-flow nasal cannula in acute respiratory failure. European respiratory journal, 59(4).
