A comparison of central venous pressure and pleural pressure in supine dogs.

Respiration induced changes in central venous pressure were analyzed and compared with intrapleural pressure changes in dogs. During normal breathing intrapleural pressure changes were transmitted to the vena cava with distortion consisting of attenuation, addition of cardiac and mean pressure components, and a slight temporal delay. Attenuation and temporal delay increased in a regular manner as mean central venous pressure increased. Cardiac components could be removed by electronic filters. The presence of these distortions suggest the need for caution in interpreting intrapleural pressure changes from central venous pressure.