FRITSCH-YELLE JM, CONVERTINO VA, SCHLEGEL TT (1999) ACUTE MANIPULA...

32. Fritsch-Yelle JM, Convertino VA, Schlegel TT (1999) Acute manipulations of plasma volume

alter arterial pressure responses during Valsalva maneuvers. J Appl Physiol 86:1852–1857

Central Venous Pressure: Uses and Limitations

T. Smith, R. M. Grounds, and A. Rhodes

Introduction

A key component of the management of the critically ill patient is the optimization

of cardiovascular function, including the provision of an adequate circulating

volume and the titration of cardiac preload to improve cardiac output. In spite of

the appearance of several newer monitoring technologies, central venous pressure

(CVP) monitoring remains in common use [1] as an index of circulatory filling

and of cardiac preload. In this chapter we will discuss the uses and limitations of

this monitor in the critically ill patient.

Defining Central Venous Pressure

What is the Central Venous Pressure?

Central venous pressure is the intravascular pressure in the great thoracic veins,

measured relative to atmospheric pressure. It is conventionally measured at the

junction of the superior vena cava and the right atrium and provides an estimate

of the right atrial pressure.

The Central Venous Pressure Waveform

The normal CVP exhibits a complex waveform as illustrated in Figure 1. The

waveform is described in terms of its components, three ascending ‘waves’ and

two descents. The a-wave corresponds to atrial contraction and the x descent to

atrial relaxation. The c wave, which punctuates the x descent, is caused by the

closure of the tricuspid valve at the start of ventricular systole and the bulging of

its leaflets back into the atrium. The v wave is due to continued venous return in

the presence of a closed tricuspid valve. The y descent occurs at the end of

ventricular systole when the tricuspid valve opens and blood once again flows

from the atrium into the ventricle. This normal CVP waveform may be modified

by a number of pathologies.

100 T. Smith, R. M. Grounds, and A. Rhodes

Fig. 1. Central venous pressure waveform from a ventilated patient (bottom) with time synchro-

nized electrocardiograph trace (top). The a-wave represents atrial contraction and occurs imme-

diately after atrial depolarization as represented by the p wave on the EKG. The c-wave represents

bulging of the tricuspid valve in early ventricular systole and is followed by the v-wave, caused by

atrial filling during ventricular systole.