On the diagnosis of acute respiratory distress syndrome in nosocomial pneumonias

Introduction

Clinical practice deals highly frequently with patients presenting a concomitant occurrence of acute respiratory distress syndrome (ARDS) and nosocomial pneumonia (NPn). Timely diagnosis of ARDS and NPn in such circumstances is problematic, but it provides a possibility of differential treatment. The aim of the investigation was to elucidate the value of the oxygenation index (OI), extravascular lung water index (EVLWI), pulmonary vascular permeability index (PVPI) and central hemodynamics indexes in the diagnosis of ARDS in NPn.

Methods

Thirty-eight cancer and severely traumatized patients were enrolled in the prospective clinical investigation. The patients were split into three groups according to the ARDS and NPn diagnostic criteria: group 1 (ARDS + NPn), group 2 (NPn), group 3 (no ARDS, no NPn). ARDS was diagnosed by means of the Lung Injury Score (LIS), the American-European Consensus Conference on ARDS criteria (1992), and the criteria of the V.A. Negovsky Research Institute of General Reanimatology (2006). All patients were investigated with a complex protocol, key elements of which were EVLWI, PVPI and central hemodynamics indexes measured by the transpulmonary thermodilution (Pulsion PiCCO plus, Pulsion Medical Systems, Germany). The data were analyzed by Statistica 7.0 (M ± SD, Newman-Keuls test, correlations). P < 0.05 was considered statistically significant.

Results

Patients of group 1 on the day of enrollment presented with a significantly lower OI (160.9 ± 51.7 mmHg vs 239.5 ± 96.7 mmHg) and static pulmonary compliance (46.3 ± 13.7 ml/water cm vs 72.4 ± 23.1 ml/water cm) and significantly higher EVLWI (12.7 ± 4.7 ml/kg vs 7.6 ± 1.6 ml/mg) and LIS (2.22 ± 0.67 scores vs 1.68 ± 0.58 scores) in comparison with group 2 patients. The patients of group 2 presented with an EVLWI within the physiological limits over the whole investigation period. PVPI calculated by three existing methods was available within the physiological limits even in the patients with a profound pulmonary edema. There were no significant differences between the groups in central hemodynamics parameters.

Conclusions

The OI, EVLWI, static pulmonary compliance and LIS made it possible to timely diagnose ARDS in NPn. Patients with NPn without ARDS presented with EVLWI within the physiological limits. A complex analysis of these indexes must be performed to diagnose ARDS in NPn. Physiological limits of the PVPI require an additional investigation due to an insufficient diagnostic value. Volumetric indexes of central hemodynamics should be measured to confirm the noncardiogenic nature of pulmonary edema.