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Do the data obtained by the PiCCO system enable one to differentiate between direct ALI/ARDS and indirect ALI/ARDS?

Introduction

It is known that measurement of the intrathoracic blood volume (ITBV) is a more accurate estimate of cardiac preload than pressure measurements using central venous or pulmonary artery occlusion pressures. Extravascular lung water (EVLW) is defined as the value of the intrathoracic thermal volume minus the ITBV. An increase in EVLW is the pathophysiological basis for the development of pulmonary edema (PE). There is evidence to suggest that therapy to reduce EVLW may improve outcome in the critically ill patient. The bedside assessment of EVLW may be very useful in identifying and quantifying PE, and hence in selecting patients who might benefit from a fluid restriction/depletion therapeutic strategy based on EVLW monitoring. The PiCCO (Pulsion, Munich, Germany) provides an estimate of the ITBV, EVLW, and permeability index (PI) via a single transpulmonary thermodilution technique. PE is defined as the abnormal accumulation of fluid in the extravascular space of the lung. ALI/ARDS is characterized by pulmonary edema. PE consists of increased hydrostatic PE (cardiogenic PE) and increased permeability PE (ALI/ARDS). Increased permeability PE (ALI/ARDS) is further classified into direct lung injury type and indirect lung injury type. PI was calculated as the ratio of EVLW to ITBV, which was previously shown to reflect permeability of the alveolar-capillary barrier. The early recognition and differential diagnosis of direct lung injury and indirect lung injury may be challenging.

Objective

To clarify whether differentiation with direct injury ALI/ ARDS and indirect injury ALI/ARDS is possible by parameters obtained from PiCCO systems.

Materials and methods

We studied 10 patients, four with direct ALI/ARDS and six with indirect ALI/ARDS (sepsis induced). Direct ALI/ARDS consisted of two aspiration and two pneumonia. All patients in indirect ALI/ARDS were sepsis. Nine of the patients were male, one was female; aged 27–85 years. All patients were mechanically ventilated in the pressure mode. GEDV, ITBV and EVLW were measured by the PiCCO and the PI was calculated. Data are presented as the mean ± SD. For statistical analysis a paired t test was performed.

Results

One hundred and twenty measurements were available for analysis. ITBVI and EVLWI were significantly higher in indirect ALI/ ARDS than in direct ALI/ARDS. PI (PVPI = EVLW/ITBV) was significantly higher in direct ALI/ARDS than in indirect ALI/ARDS. See Table 1.

Table 1

Conclusion

Measurement of the ITBV, EVLW and PI using the PiCCO system contributes to differentiating between direct and indirect ALI/ARDS and to determining the therapeutic strategy for critically ill patients. These data are an important variable for increased permeability PE, direct injury and indirect injury ALI/ARDS, and may be very helpful for guiding fluid therapy in critically ill patients. There is a possibility that data such as the ITBI, EVLWI and PI obtained from the PiCCO system might be included in the diagnostic criteria ARDS in the future.

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Morisawa, K., Taira, Y., Takahashi, H. et al. Do the data obtained by the PiCCO system enable one to differentiate between direct ALI/ARDS and indirect ALI/ARDS?. Crit Care 10, P326 (2006). https://doi.org/10.1186/cc4673

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Keywords

  • Pulmonary Edema
  • Extravascular Lung Water
  • Permeability Index
  • Pulmonary Artery Occlusion Pressure
  • Cardiogenic Pulmonary Edema