March 2026

PULMONARY

HOW RELIABLE IS WEDGE OXYGEN SATURATION IN PULMONARY HYPERTENSION?

Featuring: Ambalavanan Arunachalam, MD
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Pulmonary artery wedge (PAW) pressure remains a cornerstone measurement in the hemodynamic classification of pulmonary hypertension, but confirming a true wedge position during right heart catheterization can be challenging. Current guidelines recommend using PAW oxygen saturation with a threshold of ≥ 90% to verify accurate wedging. However, real‑world performance of this metric, particularly in patients with pulmonary hypertension, has been unclear.

​In a large, prospective study of over 200 patients undergoing right heart catheterization at a tertiary center, investigators evaluated:
  • How often PAW oxygen saturation reaches accepted diagnostic thresholds
  • If aspiration technique influences results

What the Study Found
Using two sequential blood withdrawals from a confirmed wedge position, after a standard 3.5 cc withdrawal, fewer than a third of patients achieved a PAW oxygen saturation of ≥ 90%.
  • Increasing the total withdrawal volume to 7 cc nearly doubled this proportion.
  • But about half of patients with pulmonary hypertension remained below the traditional cutoff, despite technically sound wedging.

These findings challenge the assumption that PAW oxygen saturation of < 90% reflects an inadequate wedge position. Instead, they highlight factors, such as residual pulmonary arterial blood, collateral flow and delayed capillary admixture, that may limit achievable PAW oxygen saturation in patients with pulmonary hypertension.

​The Study’s Takeaways
The study supports a more nuanced approach: increasing aspiration volume and repeating wedge maneuvers before defaulting to left ventricular end‑diastolic pressure measurement. This work provides critical insights into the limitations of PAW oxygen saturation that may inform cath lab practice.
Ambalavanan Arunachalam, MD, Assistant Professor of Pulmonary and Critical Care

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