Figure 32-27 Respiratory influences on the measurement of central venous pressure (CVP). A, During spontaneous ventilation, the onset of inspiration (arrows) causes a reduction in intrathoracic pressure that is transmitted to both the CVP and the pulmonary artery pressure (PAP) waveforms. CVP should be recorded at end-expiration (mean CVP, 14 mm Hg). B, During positive-pressure ventilation, the onset of inspiration (arrows) causes an increase in intrathoracic pressure. CVP is still recorded at end-expiration (mean CVP, 8 mm Hg). (Redrawn from Mark JB: Atlas of Cardiovascular Monitoring. New York, Churchill Livingstone, 1998, Figs. 16-1 and 16-2.)