Commentary: Feasibility to estimate mean systemic filling pressure with inspiratory holds at the bedside

Abstract

In a recent study Wijnberge and colleagues assessed the ability of mean systemic filling pressure (MSFP) determined with the inspiratory-hold method (MSFP insp_hold ) to track fluid boluses in 20 sedated and ventilated patients after coronary artery bypass grafting (Wijnberge et al., 2022). Since the method has been available for a decade, the authors implicitly raised the question why it has not been implemented in routine clinical use? The authors are to be commended to include a clinical feasibility assessment in their well performed study. Still, we think the main reason for the method not being widely used is not that it may be perceived as cumbersome, but rather that it has been proved inaccurate.We share the opinion of the authors that bedside knowledge of stressed vascular volume and driving pressure for venous return (VRdP) could aid in managing haemodynamic therapy. We respect the impetus to find a practical solution, but experimental evidence suggests that it does not come in the form of MSFP insp_hold .The development of the concept to assess MSFP by recording pressure-flow data pairs during changing inspiratory pressure is a fascinating story about applied physiology and heart-lung interactions and has deepened the understanding of venous return (VR) physiology. Already from the start, MSFP insp_hold produced surprisingly high values of MSFP and VRdP [the record being 33 and 24 mmHg respectively (Persichini et al., 2012)] as compared to zero-flow measurements in animal models and patients [clinical testing of implantable cardioverter-defibrillator devices typically report MSFP and VRdP of 10-13 and 4-4.5 mmHg respectively (Jellinek et al., 2000;Schipke et al., 2003)]. The hope of being able to measure the underlying MSFP with clinically useful accuracy was severely questioned when we demonstrated that MSFP insp_hold not only overestimated reference MSFPbut did so with a bias that varied with the volume state (Berger et al., 2016). Our initial porcine study was small but well-conducted, with intact circulation and reference method MSFP measured during intermittent right atrial balloon-occlusion. An additional physiological/mathematical

A framework for heart-lung interaction and its application to prone position in the acute respiratory distress syndrome

“…mathematical modelling by the method of Parkin and Leaning (Parkin and Leaning, 2008). Though beyond the scope of this discussion, the ventilator-hold and arm-occlusion methods over-estimate P MSF (Maas et al, 2012;Berger et al, 2016) for a variety of reasons (Moller and Berger, 2023) whereas the mean systemic filling pressure analogue (P MSA ) (i.e., the method of Parkin and Illustration of capacitance and compliance. Vessel A has a relatively small capacitance because its unstressed volume (V US A ) is small.…”

“…Though beyond the scope of this discussion, the ventilator-hold and arm-occlusion methods over-estimate P MSF ( Maas et al, 2012 ; Berger et al, 2016 ) for a variety of reasons ( Moller and Berger, 2023 ) whereas the mean systemic filling pressure analogue (P MSA ) (i.e., the method of Parkin and Leaning) accurately estimated absolute and changing values of P MSF in a porcine model ( Werner-Moller et al, 2022 ). Because it is simply calculated from P RA , cardiac output and mean arterial pressure ( Parkin and Leaning, 2008 ; Moller and Parkin, 2022 ), the P MSA is an attractive tool for guiding both prospective and retrospective research as well as clinical therapy ( Moller and Parkin, 2022 ; Moller and Berger, 2023 ). Given the above, the importance of understanding and, arguably, measuring the P MSF is that it is a hemodynamic variable the clinician can target therapeutically.…”

“…Leaning) accurately estimated absolute and changing values of P MSF in a porcine model (Werner-Moller et al, 2022). Because it is simply calculated from P RA , cardiac output and mean arterial pressure (Parkin and Leaning, 2008;Moller and Parkin, 2022), the P MSA is an attractive tool for guiding both prospective and retrospective research as well as clinical therapy (Moller and Parkin, 2022;Moller and Berger, 2023). Given the above, the importance of understanding and, arguably, measuring the P MSF is that it is a hemodynamic variable the clinician can target therapeutically.…”

Cardiopulmonary interactions—which monitoring tools to use?

“…With this method, the expected hemodynamic responses according to the physiological framework of venous return, could be confirmed following volume expansion and vasoconstriction in patients after cardiac surgery, and during septic shock ( Maas et al, 2009 ; Wijnberge et al, 2022 ; van den Berg et al, 2002 ; Aya et al, 2017 ; Cecconi et al, 2013 ), but the extrapolated values of MSFP may be inaccurate ( Berger et al, 2016b ). The underlying volume state (i.e., the state of interest) influences the accuracy of the measurements ( Berger et al, 2016b ; Werner-Moller et al, 2019 ), which may render this method invalid at the bedside ( Moller and Berger, 2023 ). Parkin and Leaning developed a simple formula to calculate an analogue for mean systemic pressure (Pmsa) based on the readily available variables of right atrial pressure, mean arterial pressure and cardiac output ( Parkin and Wright, 1991 ; Parkin et al, 1994 ; Parkin, 1999 ; Parkin and Leaning, 2008 ; Sondergaard et al, 2016 ).…”

The venous excess ultrasound score (VExUS) and the mean systemic filling pressure

“…Aya determined the least significant change of the method 14%, or 3.1 mmHg, corresponding to 29% of the driving pressure for VR (i.e., VRdP = P msf-P ra ). 4,5 (section 1.12) By contrast, we have validated P msa against gold-standard zero-flow measurements during porcine VA-ECMO. 6 Taken together, the available data suggests that the authors should have compared the change in VExUS score against P msa , and not P arm .…”