Monitoring central venous pressure, arterial pressure and pulmonary wedge pressure

Direct measurement of vascular pressure requires the insertion of a cannula into a vessel. The cannula is connected to saline filled tubing attached to a transducer apparatus for measurement and display of the vascular pressure waveform. The transducer apparatus is essentially the same for all intravascular pressure measurement. Direct measurement of arterial pressure is indicated where rapid fluctuations in pressure are anticipated, where accurate control of pressure is required, and for repeated sampling of blood gases. Central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) measurement indicate the preload of the right and left side of the heart respectively; and when considered in conjunction with other physiological measures can give a guide to the volume status of a patient. Trends in response to therapeutic intervention should be used rather than any individual value being used in isolation. Direct measurement of vascular pressure involves invasive procedures which carry a risk of complications relating to insertion of the cannulae and duration of use.