From the Guidelines
Oxygen saturation (O2 sat) may fail to improve with oxygen therapy in a patient with a pulmonary embolism (PE) if there is a right-to-left shunt or severe hypoxemia refractory to conventional oxygen supplementation.
Key Considerations
- In patients with PE, oxygen therapy is indicated if SaO2 is <90% 1
- Severe hypoxemia that is refractory to conventional oxygen supplementation could be due to a right-to-left shunt through a patent foramen ovale or atrial septal defect 1
- Further oxygenation techniques such as high-flow oxygen or mechanical ventilation may be necessary in cases of extreme instability or severe hypoxemia 1
- The goal of oxygen therapy in PE is to achieve an oxygen saturation of 94-98% (or 88-92% if the patient is at risk of hypercapnic respiratory failure) 1
Important Details
- Patients with RV failure are at risk of worsening hypotension with mechanical ventilation, and non-invasive ventilation or high-flow nasal cannula should be preferred if possible 1
- If mechanical ventilation is used, care should be taken to limit its adverse hemodynamic effects, including the use of tidal volumes of approximately 6 mL/kg lean body weight and avoiding high positive end-expiratory pressure 1
From the Research
Oxygen Saturation in Pulmonary Embolism Patients
- Oxygen saturation (O2 sat) may not improve with oxygen therapy in some patients with pulmonary embolism (PE), particularly those with intermediate-risk PE who do not have hypoxemia at baseline 2.
- A study found that supplemental oxygen did not significantly increase the proportion of patients with nonhypoxemic intermediate-risk PE whose RV to LV ratio normalized after 48 hours of treatment 2.
- However, another study suggested that high-flow nasal cannula (HFNC) oxygen therapy may be more effective than conventional oxygen therapy in improving oxygen saturation and reducing respiratory rate in patients with PE and hypoxemic respiratory failure 3.
Factors Affecting Oxygen Saturation
- The effectiveness of oxygen therapy in improving oxygen saturation may depend on various factors, including the severity of PE, the presence of hypoxemia, and the type of oxygen therapy used 3, 2.
- A study found that adding oxygen saturation to the 2014 ESC risk stratification strategy improved the discriminatory power of the model for 30-day mortality and PE-related death in hemodynamically stable PE patients 4.
Oxygen Therapy in Pulmonary Embolism
- The use of oxygen therapy in patients with intermediate-risk PE who do not have hypoxemia at baseline is uncertain, and further studies are needed to determine its effectiveness 2, 5.
- A randomized trial found that supplemental oxygen improved echocardiographic parameters in nonhypoxemic patients with intermediate-risk PE, but the study was stopped prematurely due to the COVID-19 pandemic 2.
- Another study is currently underway to evaluate the efficacy and safety of oxygen therapy in patients with intermediate-risk acute PE who do not have hypoxemia at baseline 5.