Incidence of tricuspid regurgitation and vena caval backward flow in mechanically ventilated patients. A color Doppler and contrast echocardiographic study.

In 40 patients requiring mechanical ventilation for an episode of respiratory failure of various causes, prevalence of tricuspid regurgitation (TR) or other cause of vena caval backward flow (VCBF) was systematically investigated using transthoracic Doppler echocardiography. Quantification of TR was obtained from planimetry of the regurgitant jet during color Doppler examination. The influence of cyclic mechanical lung inflation was examined by contrast echography of the inferior vena cava and hepatic veins. All the 40 patients studied had TR, which was mild in 21, moderate in 9 and severe in 10. Using a planimetric scale, TR was more marked during mechanical ventilation, when compared with a brief period of spontaneous breathing. Moreover, contrast echocardiography demonstrated that systolic TR reached inferior vena cava and hepatic veins in 16 cases, and also evidenced direct mechanical action of lung inflation producing a pancardiac VCBF in 15 cases. This high incidence of TR and VCBF partially may explain the relatively poor reliability of the thermodilution method for measurement of cardiac output when used in ventilated patients.