Platypnea-Orthodeoxia Syndrome Provoked by Small Bowel Obstruction

Platypnea-orthodeoxia syndrome (POS) is a rare condition in which positional change from recumbent to upright causes dyspnea and hypoxemia due to a cardiac or pulmonary shunt. Most cases require a primary anatomic defect and a secondary anatomic or functional factor that increases right-to-left shunting.

We report the case of a 74-year-old man who presented with unexplained hypoxemia and was found to have a patent foramen ovale and small bowel obstruction, which precipitated POS.

POS typically requires both a primary intracardiac or intrapulmonary defect and a secondary factor increasing right atrial pressure or altering septal geometry. Extracardiac contributors are often pulmonary, but in this case, a small bowel obstruction increased intra-abdominal pressure, elevating intrathoracic and right atrial pressures and increasing shunt fraction via a Valsalva-like mechanism.

POS should be considered in unexplained hypoxemia, especially when conditions such as gastrointestinal obstruction increase intra-abdominal and intrathoracic pressures.