Reply to “Is the Guytonian framework justified in explaining heart lung interactions?” and “Venous return, mean systemic pressure and getting the right answer for the wrong reason”

Berger, David; Möller, Per Werner; Takala, Jukka

doi:10.21037/atm.2019.04.50

Cited by 5 publications

(3 citation statements)

References 10 publications

(8 reference statements)

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“…Many excellent reviews connecting Guyton's model of the circulatory system to critical-illness are available (Sylvester et al, 1983;Bressack and Raffin, 1987;Fessler, 1997;Jacobsohn et al, 1997;Magder, 2004;Gelman, 2008;Parkin and Leaning, 2008;Feihl and Broccard, 2009a;Feihl and Broccard, 2009b;Magder, 2012;Berlin and Bakker, 2015;Berger and Takala, 2018;Persichini et al, 2022). Though this model has been criticized and debated (Brengelmann, 2003;Beard and Feigl, 2011;Moller et al, 2017;Berger et al, 2019;Brengelmann, 2019;Werner-Moller et al, 2020;Kenny, 2021), these controversies are beyond the scope of this review. Guyton's contributions to hemodynamics are many and may be parsed into: 1.)…”

Section: Guyton Primermentioning

confidence: 99%

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

Kenny

2023

Front. Physiol.

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While both cardiac output (Qcirculatory) and right atrial pressure (PRA) are important measures in the intensive care unit (ICU), they are outputs of the system and not determinants. That is to say, in a model of the circulation wherein venous return and cardiac function find equilibrium at an ‘operating point’ (OP, defined by the PRA on the x-axis and Qcirculatory on the y-axis) both the PRA and Qcirculatory are, necessarily, dependent variables. A simplified geometrical approximation of Guyton’s model is put forth to illustrate that the independent variables of the system are: 1) the mean systemic filling pressure (PMSF), 2) the pressure within the pericardium (PPC), 3) cardiac function and 4) the resistance to venous return. Classifying independent and dependent variables is clinically-important for therapeutic control of the circulation. Recent investigations in patients with acute respiratory distress syndrome (ARDS) have illuminated how PMSF, cardiac function and the resistance to venous return change when placing a patient in prone. Moreover, the location of the OP at baseline and the intimate physiological link between the heart and the lungs also mediate how the PRA and Qcirculatory respond to prone position. Whereas turning a patient from supine to prone is the focus of this discussion, the principles described within the framework apply equally-well to other more common ICU interventions including, but not limited to, ventilator management, initiating vasoactive medications and providing intravenous fluids.

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Section: Guyton Primermentioning

confidence: 99%

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

Kenny

2023

Front. Physiol.

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“…A prerequisite for flow is the presence of a pressure gradient pushing blood from points of higher pressure to points of lower pressure. Venous return requires MSFP to exceed right atrial (RA) pressure (P RA ) and the flow is opposed by the resistive properties of (mainly, but not exclusively) venous vessels (resistance to VR: R VR ) ( Berger et al, 2016b ; Berger et al, 2019 ). While acknowledging that R VR is a mathematical abstraction representing complex physiology, it nevertheless can be expressed with the following relationship:

…”

Section: Veno-arterial Ecmomentioning

confidence: 99%

Interactions between extracorporeal support and the cardiopulmonary system

Bachmann,

Berger,

Moller

2023

Front. Physiol.

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This review describes the intricate physiological interactions involved in the application of extracorporeal therapy, with specific focus on cardiopulmonary relationships. Extracorporeal therapy significantly influences cardiovascular and pulmonary physiology, highlighting the necessity for clinicians to understand these interactions for improved patient care. Veno-arterial extracorporeal membrane oxygenation (veno-arterial ECMO) unloads the right ventricle and increases left ventricular (LV) afterload, potentially exacerbating LV failure and pulmonary edema. Veno-venous (VV) ECMO presents different challenges, where optimal device and ventilator settings remain unknown. Influences on right heart function and native gas exchange as well as end-expiratory lung volumes are important concepts that should be incorporated into daily practice. Future studies should not be limited to large clinical trials focused on mortality but rather address physiological questions to advance the understanding of extracorporeal therapies. This includes exploring optimal device and ventilator settings in VV ECMO, standardizing cardiopulmonary function monitoring strategies, and developing better strategies for device management throughout their use. In this regard, small human or animal studies and computational physiological modeling may contribute valuable insights into optimizing the management of extracorporeal therapies.

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“…The right atrial pressure (RAP) acts as a back pressure to venous return ( Moller et al, 2017 ). As with any system of related pressure and flow, the flow to the right atrium is opposed by the resistance to venous return (RVR) ( Berger et al, 2016a ; Bloch et al, 2016 ; Berger et al, 2019 ; Moller et al, 2019 ). The mean systemic filling pressure is the equilibrated vascular pressure of the systemic circulation at zero flow ( Magder and De Varennes, 1998 ).…”

Section: The Explanatory Model: Optimal Monitoring Within the Framewo...mentioning

confidence: 99%

Cardiopulmonary interactions—which monitoring tools to use?

2023

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Heart-lung interactions occur due to the mechanical influence of intrathoracic pressure and lung volume changes on cardiac and circulatory function. These interactions manifest as respiratory fluctuations in venous, pulmonary, and arterial pressures, potentially affecting stroke volume. In the context of functional hemodynamic monitoring, pulse or stroke volume variation (pulse pressure variation or stroke volume variability) are commonly employed to assess volume or preload responsiveness. However, correct interpretation of these parameters requires a comprehensive understanding of the physiological factors that determine pulse pressure and stroke volume. These factors include pleural pressure, venous return, pulmonary vessel function, lung mechanics, gas exchange, and specific cardiac factors. A comprehensive knowledge of heart-lung physiology is vital to avoid clinical misjudgments, particularly in cases of right ventricular (RV) failure or diastolic dysfunction. Therefore, when selecting monitoring devices or technologies, these factors must be considered. Invasive arterial pressure measurements of variations in breath-to-breath pressure swings are commonly used to monitor heart-lung interactions. Echocardiography or pulmonary artery catheters are valuable tools for differentiating preload responsiveness from right ventricular failure, while changes in diastolic function should be assessed alongside alterations in airway or pleural pressure, which can be approximated by esophageal pressure. In complex clinical scenarios like ARDS, combined forms of shock or right heart failure, additional information on gas exchange and pulmonary mechanics aids in the interpretation of heart-lung interactions. This review aims to describe monitoring techniques that provide clinicians with an integrative understanding of a patient’s condition, enabling accurate assessment and patient care.

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Reply to “Is the Guytonian framework justified in explaining heart lung interactions?” and “Venous return, mean systemic pressure and getting the right answer for the wrong reason”

Cited by 5 publications

References 10 publications

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

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

Interactions between extracorporeal support and the cardiopulmonary system

Cardiopulmonary interactions—which monitoring tools to use?

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