When the heart stops beating and blood flow ceases, the pressure inside the vasculature does not fall to zero. A residual pressure distends the blood vessels even in the absence of flow, and physiologists call it mean circulatory filling pressure (MCFP). A new review in Annals of Intensive Care, published on 24 November 2025, examines why this base pressure exists and what it means for critically ill patients.
The review, authored by Sheldon Magder, Douglas Slobod and Antoine Vieillard-Baron, explains the physiological necessity of this base pressure. Although all pressures across the vasculature become equal when there is no flow, blood volume does not distribute evenly. Instead, volume distributes according to the compliance of the vessel walls in each compartment, meaning how much each compartment expands for a given change in pressure.
The systemic venous compartment has by far the largest compliance of any vascular region and contains most of the blood volume. This dominance of venous compliance is what makes the concept clinically useful. When the heart begins to pump and flow resumes, volume redistributes among the vascular regions based on the compliance of each region and the resistance of the vessels draining them.
Because the systemic venous compartment dominates total compliance, its pressure changes very little during this redistribution. That relatively stable venous pressure is called mean systemic filling pressure (MSFP). Under normal hemodynamic conditions, the review notes, the difference between MCFP and MSFP is trivial, precisely because venous compliance is so large compared with all other vascular regions.
The two pressures carry distinct significance. When cardiac function is maximal, MCFP determines the maximum possible cardiac output, setting a hard ceiling on how much blood the heart can deliver. MSFP matters for two separate reasons: it is the upstream pressure driving blood back to the right heart, and it is also the downstream pressure for systemic capillary drainage.
That second role has direct consequences for tissue fluid balance. A high MSFP opposes the drainage of fluid from the capillaries, so the review concludes that an elevated MSFP increases the risk of tissue edema. This links a classic hemodynamic concept to a practical concern in intensive care, where both fluid resuscitation and organ edema are daily preoccupations.
From the authors’ review of the studies, the pressure difference from MSFP to the right atrial pressure (RAP) generally falls in the range of 3 to 6 mmHg. This offers a bedside approximation: MSFP can be estimated by adding a value in this range to a properly measured right atrial pressure. The authors emphasize that the RAP must be properly measured for the approximation to hold.
The review also proposes a practical target. Ideally, MSFP should be less than 10 mmHg in order to limit capillary drainage and thereby reduce the risk of edema. As a review article, the work synthesizes existing physiological studies rather than reporting new measurements, and its recommendations reflect that synthesis of prior evidence. For clinicians managing fluids in intensive care, the message is that the pressure left in the vessels when the heart is not beating is not a physiological curiosity but a quantity that constrains cardiac output at its maximum and, when it rises too high, threatens the tissues with fluid accumulation.
Subject of Research: The physiological and clinical roles of mean circulatory and mean systemic filling pressures in venous return, cardiac output and edema risk
Article Title: Physiological and clinical significance of mean circulatory and mean systemic filling pressure
Article References: Magder, S., Slobod, D., & Vieillard-Baron, A. (2025). Physiological and clinical significance of mean circulatory and mean systemic filling pressure. Annals of Intensive Care, 15(1), Article 187. https://doi.org/10.1186/s13613-025-01595-0
Image Credits: AI Generated
DOI: 10.1186/s13613-025-01595-0
Keywords: mean circulatory filling pressure, mean systemic filling pressure, venous return, cardiac output, venous compliance, right atrial pressure, tissue edema, capillary drainage, hemodynamics, intensive care, fluid management, Physiological
News Source: Ophelia Keating. (October 29, 2026). Mean circulatory filling pressure emerges as key to cardiac output and edema risk. Scienmag.
