The inspiration hold maneuver is a reliable method to assess mean systemic filling pressure but its clinical value remains unclear.

Background: The upstream pressure for venous return (VR) is considered to be a combined conceptual blood pressure of the systemic vessels: the mean systemic filling pressure (MSFP). The relevance of estimating the MSFP during dynamic changes of the circulation at the bedside is controversial. Herein, we studied the effect of high ventilatory pressures on the relationship between VR and central venous pressure (CVP).

Methods: In 9 healthy pigs under anaesthesia and mechanically ventilated, MSFP was estimated from extrapolated VR versus CVP relationships during inspiratory hold maneuvers (IHMs) with different levels of ventilatory pressure (Pvent). MSFP was measure 3 times per animal during euvolemia and hypovolemia. Hypovolemia was induced by bleeding with 10 mL/kg. The estimated MSFP values were compared to the blood pressure recording after induced ventricle fibrillation (i.e., mean circulatory filling pressure).

Results: Our results revealed a strong linear correlation between VR and CVP [R2 of 0.92 (range, 0.67-0.99)], during IHMs with different levels of Pvent. Volume status significantly alters the resulting MSFP, 20±1 and 16±2 mmHg for euvolemia and hypovolemia respectively. This estimation of the MSFP was strongly correlated-but not interchangeable-to the blood pressure recording after induced ventricle fibrillation (R2=0.8 and P=0.045).

Conclusions: In conclusion, we showed a strong linear correlation between VR and CVP-when applying IHMs with high levels of Pvent-however the clinical applicability of this method to guide volume therapy in its current form is improbable.