Investigation of the pulmonary vascular permeability index and extravascular lung water in patients with SIRS and ARDS under the PiCCO system

Background and objectives

The hallmark of both systemic inflammation response syndrome (SIRS) and acute respiratory distress syndrome (ARDS) is increased capillary permeability, which manifests itself in the lungs as altered alveolar–capillary barrier function and is characterised by accumulation of extravascular lung water (EVLW). It is known that EVLW estimated by transpulmonary single thermodilution correlates closely with gravimetric measurements in experiments on animal studies. The correlation in human beings, however, is uncertain. Furthermore, the pulmonary vascular permeability index (PVPI) in patients with SIRS and ARDS has never been investigated in the literature. The aims of our study were: to evaluate whether PVPI may be an indicator of systemic inflammation disease and the severity of lung injury; and to compare the postmortem lung weight and EVLW measured by transpulmonary single thermodilution.

Materials and methods

The PiCCO system (PULSION, Munich, Germany) data from 41 patients (APACHE II score 25 ± 7.5) treated in three hospitals between July 2004 and September 2005 was analysed retrospectively. The patients were divided into two groups. The first included patients who met the criteria of SIRS and the latter did not (SIRS vs non-SIRS). The SIRS groups was further subdivided into two; SIRS with ARDS, and SIRS without ARDS. We also considered four patients upon whom autopsies were carried out within 15 hours after the thermodilution EVLW measurement was performed.

Results

The PVPI was significantly higher in the SIRS group (n = 31) than the non-SIRS group (n = 10) (SIRS vs non-SIRS: 2.37 ± 1.0 vs 1.2 ± 0.21; P = 0.0013). The PVPI was highest in the SIRS with ARDS group (n = 13) and lowest in the non-SIRS group (P < 0.001). Moreover, the PVPI was higher in the SIRS with ARDS group than the SIRS without ARDS group (n = 18) (non-SIRS vs SIRS with ARDS vs SIRS without ARDS: 1.2 ± 0.21 vs 1.7 ± 0.44 vs 3.2 ± 1.10). There was a very close relationship between transpulmonary thermodilution and postmortem lung weight (n = 4, R = 0.985; P = 0.0015)

Conclusion

Measurement of extravascular lung water using the PiCCO system is very closely correlated with the gravimetric measurement of lung weight. The PVPI may increase due to systemic inflammation. This increase of PVPI may represent subclinical lung injury, which is undetectable by other bedside monitors or clinical examination.