Paradoxical hypoxemia following positive pressure ventilation: exploring the pathophysiology

Abstract

Positive pressure ventilation (PPV), both non-invasive and invasive, enhances ventilation but can sometimes lead to unexpected hypoxemia. This case report describes an instance of paradoxical hypoxemia after initiating bilevel positive airway pressure (BiPAP) in a 58-year-old female with a medical history of systemic lupus erythematosus, interstitial lung disease, and pulmonary embolism. BiPAP was started, leading to improved hypercarbia but worsened hypoxemia. Further investigation revealed a right-to-left interatrial shunt via a small patent foramen ovale (PFO). Adjusting BiPAP settings improved arterial blood gas parameters. This case illustrates how positive pressure ventilation with underlying PFO can cause paradoxical hypoxemia. The case emphasizes the importance of understanding the pathophysiology and tailoring BiPAP settings based on individual haemodynamics.

Keywords

• hypoxemia
• positive pressure ventilation
• patent foramen ovale
• shunt