Limits...
Respiratory variation in inferior vena cava diameter: surrogate of central venous pressure or parameter of fluid responsiveness? Let the physiology reply.

Bodson L, Vieillard-Baron A - Crit Care (2012)

Bottom Line: In the previous issue of Critical Care, Muller and colleagues investigated whether respiratory variation in inferior vena cava diameter (ΔIVC) could be a useful predictor of fluid responsiveness in spontaneously breathing patients.The study concludes that accuracy was not very good and therefore that this parameter should be used with caution in these patients.In this brief commentary, we try to summarize as clearly as possible the significance of IVC variation in different clinical settings.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
In the previous issue of Critical Care, Muller and colleagues investigated whether respiratory variation in inferior vena cava diameter (ΔIVC) could be a useful predictor of fluid responsiveness in spontaneously breathing patients. The study concludes that accuracy was not very good and therefore that this parameter should be used with caution in these patients. There is still confusion about the meaning of IVC respiratory variations, whether the patient is spontaneously breathing or mechanically ventilated. In this brief commentary, we try to summarize as clearly as possible the significance of IVC variation in different clinical settings.

Show MeSH

Related in: MedlinePlus

Relationship between inferior vena cava (IVC) diameter and central venous pressure (CVP), derived from Barbier and colleagues [5]. The pressure/diameter relationship shows an initial steep part where a minimal increase in CVP, in response to increased intrathoracic pressure, is associated with a large increase in IVC diameter and a flat part where the compliance of the IVC decreases, resulting in less IVC dilation and a larger increase in CVP. Dark arrow: effect of increased intrathoracic pressure in a preload-responsive patient. Gray arrow: effect of increased intrathoracic pressure in a preload-unresponsive patient.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3672574&req=5

Figure 2: Relationship between inferior vena cava (IVC) diameter and central venous pressure (CVP), derived from Barbier and colleagues [5]. The pressure/diameter relationship shows an initial steep part where a minimal increase in CVP, in response to increased intrathoracic pressure, is associated with a large increase in IVC diameter and a flat part where the compliance of the IVC decreases, resulting in less IVC dilation and a larger increase in CVP. Dark arrow: effect of increased intrathoracic pressure in a preload-responsive patient. Gray arrow: effect of increased intrathoracic pressure in a preload-unresponsive patient.

Mentions: However, there is still some confusion regarding the study of the IVC, and of its respiratory changes, in the intensive care unit. The paper by Muller and colleagues [1] offers an opportunity to try to re-emphasize the basic physiology of the IVC (Figure 1). ΔIVC depends on few factors: the intrathoracic and abdominal pressures, the central venous pressure (CVP), and the compliance of the vessel. In mechanically ventilated patients, the objective of studying the IVC is to assess its ability to dilate during tidal ventilation, when intrathoracic pressure is increasing more than abdominal pressure. This dilation actually reflects the ability of the IVC to receive more volume (preload reserve), like a preserved compliance. The IVC is then on the steep part of the relationship between IVC diameter and CVP (Figure 2). As reported by Barbier and colleagues [5], such a relationship is curvilinear. In contrast, the absence of significant dilation reflects the inability of the IVC to receive more fluid (no preload reserve), owing to low compliance. The IVC is then on the flat part of its relationship with CVP (Figure 2).


Respiratory variation in inferior vena cava diameter: surrogate of central venous pressure or parameter of fluid responsiveness? Let the physiology reply.

Bodson L, Vieillard-Baron A - Crit Care (2012)

Relationship between inferior vena cava (IVC) diameter and central venous pressure (CVP), derived from Barbier and colleagues [5]. The pressure/diameter relationship shows an initial steep part where a minimal increase in CVP, in response to increased intrathoracic pressure, is associated with a large increase in IVC diameter and a flat part where the compliance of the IVC decreases, resulting in less IVC dilation and a larger increase in CVP. Dark arrow: effect of increased intrathoracic pressure in a preload-responsive patient. Gray arrow: effect of increased intrathoracic pressure in a preload-unresponsive patient.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3672574&req=5

Figure 2: Relationship between inferior vena cava (IVC) diameter and central venous pressure (CVP), derived from Barbier and colleagues [5]. The pressure/diameter relationship shows an initial steep part where a minimal increase in CVP, in response to increased intrathoracic pressure, is associated with a large increase in IVC diameter and a flat part where the compliance of the IVC decreases, resulting in less IVC dilation and a larger increase in CVP. Dark arrow: effect of increased intrathoracic pressure in a preload-responsive patient. Gray arrow: effect of increased intrathoracic pressure in a preload-unresponsive patient.
Mentions: However, there is still some confusion regarding the study of the IVC, and of its respiratory changes, in the intensive care unit. The paper by Muller and colleagues [1] offers an opportunity to try to re-emphasize the basic physiology of the IVC (Figure 1). ΔIVC depends on few factors: the intrathoracic and abdominal pressures, the central venous pressure (CVP), and the compliance of the vessel. In mechanically ventilated patients, the objective of studying the IVC is to assess its ability to dilate during tidal ventilation, when intrathoracic pressure is increasing more than abdominal pressure. This dilation actually reflects the ability of the IVC to receive more volume (preload reserve), like a preserved compliance. The IVC is then on the steep part of the relationship between IVC diameter and CVP (Figure 2). As reported by Barbier and colleagues [5], such a relationship is curvilinear. In contrast, the absence of significant dilation reflects the inability of the IVC to receive more fluid (no preload reserve), owing to low compliance. The IVC is then on the flat part of its relationship with CVP (Figure 2).

Bottom Line: In the previous issue of Critical Care, Muller and colleagues investigated whether respiratory variation in inferior vena cava diameter (ΔIVC) could be a useful predictor of fluid responsiveness in spontaneously breathing patients.The study concludes that accuracy was not very good and therefore that this parameter should be used with caution in these patients.In this brief commentary, we try to summarize as clearly as possible the significance of IVC variation in different clinical settings.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
In the previous issue of Critical Care, Muller and colleagues investigated whether respiratory variation in inferior vena cava diameter (ΔIVC) could be a useful predictor of fluid responsiveness in spontaneously breathing patients. The study concludes that accuracy was not very good and therefore that this parameter should be used with caution in these patients. There is still confusion about the meaning of IVC respiratory variations, whether the patient is spontaneously breathing or mechanically ventilated. In this brief commentary, we try to summarize as clearly as possible the significance of IVC variation in different clinical settings.

Show MeSH
Related in: MedlinePlus