Increased pulse pressure variations observed in a pulmonary experimental thromboembolism model

Background

Pulse pressure respiratory variation (PPV), which is the difference between the maximal and minimal arterial pulse pressure values after each positive-pressure breath, is largely used for early identification of hypovolemic status. Increased PPV observed in hypovolemia results from exaggerated respiratory variation in transpulmonary blood flow that results in corresponding left ventricular preload variations during respiratory cycles. Hence, any modulations that affect the left ventricular preload would influence PPV.

Objective

To test the hypothesis that PPV amplification observed in hypovolemia can also be detected after pulmonary thromboembolism obtained with central venous injection of blood cloth.

Methods

PPV was studied in five anesthetized and mechanically ventilated male rabbits weighing 1.6 ± 0.3 kg. The heart rate (HR) and mean arterial pressure (MAP) were monitored after central venous (jugular) and arterial (carotid) catheterization, and 1.5 ml/kg autologous blood cloth were injected slowly through the jugular catheter into the central circulation. The HR, MAP and PPV were registered before and after blood cloth injection and compared using the Student t test.

Results

The HR did not change, but the MAP was significantly lowered as much as PPV significantly increased after cloth injection. See Table 1.

Table 1

Conclusion

PPV amplification observed in hypovolemia can be also detected after pulmonary thromboembolism obtained with central venous injection of blood cloth. It is possible to conclude that pulmonary hypertension should be assumed as a limitation for cardiovascular fluid responsiveness determination by PPV.