Electrical bioimpedance for diagnosing thoracic injuries -test on a porcine pneumothorax and hemothorax model
Background: Thoracic injuries such as pneumothorax (PTX) and hemothorax (HTX) are common injuries for motor vehicle crashes that pose a high risk of patient fatality if not treated adequately. The dilemma is that these conditions are sometimes difficult to diagnose in the prehospital setting. In order to prevent unnecessary morbidity and mortality a point-of-care test is needed to diagnose PTX/HTX and monitor its progression before the patient reaches a hospital. For this purpose, electrical bioimpedance (EBI) is a noninvasive, harmless, non-expensive, portable, rapid and easy to use technology suitable for the prehospital environment.
Objective: Testing whether thoracic injuries such as PTX and HTX produce detectable changes in thoracic EBI.
Methods: An experimental model was set up in two anesthetized Landraze pigs. Eight Ag/AgCl electrodes were attached symmetrically on both sides of the pigs’ chest. Air was insufflated into the pleural space in twelve incremental steps from small PTX volume (50mL) to large volume (2000 mL). Hemothorax was mimicked by injecting water. Lateral PTX (right lung), bilateral PTX and HTX were produced in both pigs. An EBI measurement was performed with Biopac EBI100C amplifier at 50 kHz following each injection of air or water.
Results: Signal quality was excellent and allowed clear visualization of breathing rate and pulse. The ratio between the average values of both sides’measurements, ξ = Lungleft/Lungright was identified as the best indicator of PTX andHTX. The trends of ξ with evolving PTXwere as expected; EBI theory predicts air volume should increase resistivity and water decrease it. The signal trends were similar for both pigs.
Conclusions: The results indicate that EBI measurements could be useful in a future medical device for diagnosing/monitoring PTX and HTX. EBI could also be useful for continuous monitoring of vital signs.