Introduction

Limitations of minimally invasive hemodynamic monitoring devices are important in order to assess when and where these devices will provide utility. Challenging situations for these devices occur during extreme hyperdynamic conditions like septic shock, characterized by extreme loss of vascular tone and high cardiac output (CO). Identification that a patient has entered this condition could prove useful for assessing performance of the aforementioned devices, as well as providing additional information about patient condition, which should be evaluated for its potential utility.

Methods

In a group of 18 patients we evaluated the sensitivity and specificity for a new peripheral decoupling indicator (PDI) in assessing moments when physiological patient conditions may be causing the arterial pressure-derived cardiac output (APCO) to be underestimated. Comparison was made between a pulmonary artery catheter (PAC) and an APCO sensor (FloTrac Edwards Lifesciences, CA, USA). Data were collected over a period of 1,090 hours, providing a total of 196,369 data points for evaluation, with CO values ranging from 2 to 16.

Results

The PDI demonstrated specificity of 96.7% and sensitivity of 82.6%. During these identified periods, FloTrac consistently exhibited a one-sided bias in its CO value, with a lower CO value when compared with the PAC. Only two of the patients exhibited periods of peripheral decoupling. Overall, the PDI indicated 'on' for 4,392 of the data points collected, or 2.2% of the time. Figure 1 illustrates the data from one of these patients.

Figure 1
figure 1

PDI, peripheral decoupling indicator; APCO, arterial pressure-derived cardiac output; CCO, continuous cardiac output; ICO, intermittent (or bolus) cardiac output.

Conclusion

The PDI identified moments when patient physiology led to underestimation of the FloTrac CO value. Additional research is needed to determine whether the low incidence rate of extended peripheral decoupling observed in our study is typical in septic patients, and whether it could be correlated to patient condition or treatment. Further research is necessary to determine any potential prognostic value from the PDI.