Table 2 Limitations with the use of pulse pressure variation (PPV) to predict fluid responsiveness

1

Spontaneous breathing activity

Irregular variations in intrathoracic pressure and thus the variation in stroke volume cannot correlate with preload dependency

False positive

(may occasionally be false negative depending on the type of breathing)

2

Cardiac arrhythmias

The variation in stroke volume is related more to the irregularity in diastole than to the heart‐lung interactions

False positive

3

Mechanical ventilation using low tidal volume (<8 ml/kg)

The small variations in intrathoracic pressure due to the low tidal volume are insufficient to produce significant changes in the intrathoracic pressure

False negative

4

Low lung compliance

The transmission of changes in alveolar pressure to the intrathoracic structures is attenuated

False negative

5

Open thorax

No change in intrathoracic pressure during the respiratory cycle

False negative

6

Increased intra‐abdominal pressure

Threshold values of PPV will be elevated

False positive

7

Low HR/RR ratio < 3.6 (severe bradycardia or high frequency ventilation)

If the RR is very high, the number of cardiac cycles per respiratory cycle may be too low to allow variation in stroke volume

False negative