Intrathoracic impedance monitoring in a novel model of acute pulmonary edema

Abstract

OBJECTIVE: The goal of this study was to monitor changes in intrathoracic impedance in a reversible model of acute pulmonary edema (PE). METHODS: PE was induced in 9 pigs via simultaneous negative intratracheal pressure (ITP - 30 mmHg) during expiration and intravenous administration of phenylephrine. PE was reversed by cessation of phenylephrine and negative ITP and administration of PEEP (5 cmH20). After one hour, PEEP was removed and data collected for one additional hour. Impedance was recorded from a vector consisting of a lead placed in the RV apex and a subcutaneous device can emulator placed left lateral to the sternum. Similar data was collected in time control group of 4 animals. Hemodynamic data and arterial blood gases were acquired every half-hour. RESULTS: PE was validated by auscultation of pulmonary rales in the experimental group after 3.36 ± 1.14 hours. Mean impedance at BASELINE: (experimental vs. control) was 42.8 ± 3.9 vs. 48 ± 3, p < 0.05, at EDEMA: 37 ± 3.8 vs. 42 ± 4, p < 0.05, at PEEP: 37.1 ± 2.7 vs. 41 ± 4, p < 0.05, at RECOVERY: 36.6 ± 2.1 vs. 40 ± 3, p=NS. The PE model resulted in detection of pulmonary rales, increased RV pressure and decreased pO2 (p<0.05). CONCLUSIONS: Acute induced PE can be detected using thoracic impedance with an implantable bipolar electrode vector. © Springer-Verlag 2007.