Comparing transpulmonary thermodilution monitoring to lung ultrasound during pneumonia: an observational study

Monitoring lung function during pneumonia is essential for the evaluation of the effectiveness of therapy in ICU patients. Among various bedside techniques, two particularly interesting are the lung ultrasound and the transpulmonary thermodilution technique. In this observational single center study we want to assess the correlation between the lung ultrasound examination (LUS) and transpulmonary thermodilution volumetric parameters such as extravascular lung water index (EVLWI) and pulmonary vascular permeability index (PVPI).

We analyzed data obtained from medical history of twelve patients requiring mechanical ventilation and hemodynamics monitoring with PICCO catheter due to newly diagnosed pneumonia. We compared lung ultrasound examination performed on the first and third day of new antimicrobial therapy with results of transpulmonary thermodilution examination made on same day. We also calculate the difference between values obtained on first and third day to compare the trends.

We did not find any association between tested variables, except a correlation between PVPI and EVLWI, both measured at the same day (Rho = 0.3; 95%CI -0.02-0.59; p = 0.03), and trends in the period of 3 days (Rho = 0.6; 95%CI 0.2-0.8; p = 0.005).

The results of the study indicate that volumetric values achieved using the PiCCO method as well as lung ultrasound should be interpreted with care and related to the clinical state of a patient, keeping in mind that no correlation between the result achieved and the actual state of inflammatory changes in the lungs may be possible.