From the Guidelines
Hypoxemia from a small patent foramen ovale (PFO) with right-to-left shunt can be correctable with supplemental nasal oxygen, as it increases the partial pressure of oxygen in the blood, thereby improving overall arterial oxygen content despite the anatomical shunt. The effectiveness of oxygen therapy depends on the size of the shunt and the underlying cause of the right-to-left flow. According to the BTS guideline for oxygen use in adults in healthcare and emergency settings 1, oxygen therapy is effective in increasing PAO2 and improving oxygen saturation, even in cases with low V/Q ratio or diffusion limitation. However, it is essential to note that oxygen therapy is a symptomatic treatment that does not address the underlying defect.
For patients with position-dependent hypoxemia (platypnea-orthodeoxia syndrome), oxygen may be particularly helpful when upright. The European Society of Cardiology guidelines on the diagnosis and management of acute pulmonary embolism 1 also support the use of nasal oxygen in patients with hypoxemia, including those with a patent foramen ovale.
Key considerations for oxygen therapy in these patients include:
- Monitoring oxygen saturation with pulse oximetry to ensure adequate oxygenation 1
- Titration of oxygen flow rates to maintain oxygen saturation above 92% or as directed by their physician
- Awareness that oxygen therapy does not treat the underlying causes of hypoxemia, which must be diagnosed and treated as a matter of urgency 1
- Consideration of definitive correction through PFO closure in cases where hypoxemia is severe or persistent despite supplemental oxygen.
From the Research
Hypoxemia from a Small PFO with Right to Left Shunt
- Hypoxemia due to a patent foramen ovale (PFO) with right to left shunt is a condition where deoxygenated blood from the right atrium enters and mixes with oxygenated arterial blood in the left atrium 2.
- The presence of right-to-left cardiac shunting can exacerbate the degree of hypoxemia in patients with underlying pulmonary disorders 2.
Correctability with Nasal Oxygen
- There is no direct evidence to suggest that hypoxemia from a small PFO with right to left shunt is correctable with nasal oxygen alone 3, 4, 5, 2, 6.
- Studies have shown that percutaneous closure of PFO can result in marked improvement in dyspnea and hypoxemia in patients with PFO-mediated right-to-left shunting 5, 6.
- Percutaneous closure of PFO has been shown to improve oxygen saturation, dyspnea, and quality of life in patients with PFO-related hypoxemia 6.
Management of Hypoxemia due to PFO
- Management of hypoxemia due to PFO should aim to decrease pulmonary vascular resistance and optimize ventilation/perfusion matching by treating the underlying cause of the right-to-left pressure gradient 3.
- Airway pressure release ventilation (APRV) can minimize pulmonary vascular resistance and maximize ventilation/perfusion ratios, and should be considered in treating patients with PFO-mediated hypoxemia 3.