From the Guidelines
If a patient's oxygen saturations do not improve despite receiving 15 liters of oxygen via a non-rebreather mask, immediate escalation to advanced respiratory support is necessary. Consider transitioning to high-flow nasal cannula (HFNC) at 40-60 L/min with FiO2 of 100%, or initiate non-invasive positive pressure ventilation (NIPPV) such as BiPAP with settings of IPAP 10-14 cmH2O and EPAP 4-6 cmH2O, as recommended by the British Thoracic Society guidelines for oxygen use in adults in healthcare and emergency settings 1. If these measures fail, prompt endotracheal intubation and mechanical ventilation should be pursued.
While preparing for escalation, position the patient upright or in prone position if tolerated, ensure the oxygen delivery system is functioning properly, and assess for potential causes of refractory hypoxemia such as pneumothorax, pulmonary embolism, severe pneumonia, ARDS, pulmonary edema, or airway obstruction, as outlined in the BTS guideline 1. Obtain immediate arterial blood gas analysis, chest imaging, and consider point-of-care ultrasound. This situation represents a medical emergency as the patient is likely experiencing severe hypoxemic respiratory failure despite maximal conventional oxygen therapy, which can rapidly progress to cardiopulmonary arrest if not addressed promptly. Key considerations include:
- Assessing for underlying causes of hypoxemia, such as those listed in the BTS guideline 1
- Ensuring proper functioning of the oxygen delivery system
- Considering advanced respiratory support options, including HFNC and NIPPV, as recommended by the BTS guideline 1
- Preparing for potential endotracheal intubation and mechanical ventilation if necessary.
From the Research
Patient's Oxygen Saturations Not Improving
- If a patient's oxygen saturations do not improve despite receiving 15 liters of oxygen via a non-rebreather mask, several factors should be considered:
- The patient's underlying condition, such as COVID-19, may be causing refractory hypoxemia, as seen in a study comparing the efficacy of inhaled nitric oxide and inhaled epoprostenol in patients with COVID-19 2.
- The effectiveness of the non-rebreather mask in delivering oxygen, as studies have shown that nonrebreather masks with flush rate oxygen can be noninferior to bag-valve masks in preoxygenation 3, 4.
- The possibility of a mask leak or inadequate fit, which can compromise the effectiveness of the non-rebreather mask, as demonstrated in a study comparing preoxygenation methods 3.
Alternative Preoxygenation Methods
- Other preoxygenation methods, such as apneic oxygenation or delayed sequence intubation, may be considered for patients who are unable to achieve adequate saturations with conventional methods 5.
- The use of a nonrebreather mask with flush rate oxygen may be a practical solution for preoxygenation in the prehospital setting, as it has been shown to be noninferior to bag-valve masks in healthy volunteers 4.
Oxygen Delivery Devices
- The performance of oxygen delivery devices can be affected by the patient's breathing pattern, with high-flow devices being less affected by respiratory failure 6.
- Nonrebreathing masks have been shown to deliver a consistent fraction of inspired oxygen (FiO2) even when the breathing pattern of respiratory failure is simulated 6.