Monitoring water content of rat lung tissuein vivo using microwave reflectometry

Intraoperative lung edema monitoring by microwave reflectometry

Microwave reflectometry might be a suitable tool for the thoracic surgeon to monitor edema formation of the lung during lung surgery. A new setup of microwave reflectometry for lung water measurements was developed and tested for clinical application. Three lung models were used for the microwave reflectometry tests: 1) the model of an ex vivo isolated perfused rat lung to investigate lung edema formation during ischemia-reperfusion (n=6), 2) the in situ lung of a human patient to demonstrate the feasibility of lung water monitoring during a surgical operation, 3) the model of an ex vivo isolated perfused human lung to investigate edema formation during postischemic reperfusion and to investigate the changes in water content in the region of a tumor. During human lung operation, significant changes in water content occurred in different lung areas. During isolated perfusion, a significant increase in lung water was measured in models 1) and 3) (P=0.03). Water content of tumor tissue was higher than in the surrounding healthy lung tissue. Microwave reflectometry offers a non-invasive approach to monitor lung edema formation in experimental models and during thoracic surgery.

Monitoring of Lung Edema by Microwave Reflectometry during Lung Ischemia-Reperfusion Injury in vivo

It is still unclear whether lung edema can be monitored by microwave reflectometry and whether the measured changes in lung dry matter content (DMC) are accompanied by changes in PaO2 and in pro- to anti-inflammatory cytokine expression (IFN-gamma and IL-10). Right rat lung hili were cross-clamped at 37 degrees C for 0, 60, 90 or 120 min ischemia followed by 120 min reperfusion. After 90 min (DMC: 15.9 +/- 1.4%; PaO2: 76.7 +/- 18 mm Hg) and 120 min ischemia (DMC: 12.8 +/- 0.6%; PaO2: 43 +/- 7 mm Hg), a significant decrease in DMC and PaO2 throughout reperfusion compared to 0 min ischemia (DMC: 19.5 +/- 1.11%; PaO2: 247 +/- 33 mm Hg; p < 0.05) was observed. DMC and PaO2 decreased after 60 min ischemia but recovered during reperfusion (DMC: 18.5 +/- 2.4%; PaO2: 173 +/- 30 mm Hg). DMC values reflected changes on the physiological and molecular level. In conclusion, lung edema monitoring by microwave reflectometry might become a tool for the thoracic surgeon.