Bronchoscopy and Electric Impedance Tomography (EIT) Pilot Study

Bronchoscopy and Electric Impedance Tomography to Investigate the Influence of Bronchoscopy on Pulmonary Regional Ventilation Measurements by Electric Impedance Tomography (EIT)

Electrical Impedance Tomography (EIT)is a technique based on the injection of small currents and voltage measurements using electrodes on the skin surface generating cross-sectional images representing impedance change in a slice of the thorax. It is a radiation free, non-invasive and portable lung imaging technique. Impedance changes in lung ventilation are investigated in mechanically ventilated patients who routinely undergo bronchoscopy in intensive care medicine. Bronchoscopy is performed to suction secretions as well as to analyze the secretions to recognize inflammations and diseases. It is an essential intervention which causes changes in ventilation which remain for 1-2 hours. It is not completely investigated why these changes in ventilation remain for so long time and how they are distributed regionally. Therefore the purpose of this study is to investigate the change in pulmonary regional ventilation in patients who routinely undergo bronchoscopy to possibly generate ideas how to optimize the ventilation after bronchoscopy to optimize the patient´s treatment.

In 20 mechanically ventilated patients who routinely undergo bronchoscopy Electrical Impedance Tomography (EIT) measurements whereby, evaluable data of 10 patients are needed, of about 1-2 minutes are performed directly before, directly after and 10, 30, and 60 minutes after bronchoscopy parallel to the following routine measurements: tidal volume, resistance, compliance, heart rate, blood pressure, SpO2 and blood gas values. Prior to the examination a rubber belt with 16 integrated electrocardiographic electrodes is placed around the thorax connected with an EIT- device. EIT data are generated by application of a small alternating current of 5mA and 50kHz and are stored and analyzed offline on a personal computer. The EIT provides a mapping of the distribution of the lung´s electrical impedance and exhibits a far temporal resolution of up to 40 tomograms per second. Because of electrical impedance of the pulmonal tissue is dependant to the air content, the air distribution within the lung over a certain period can be monitored. Analyzing the EIT- data it might be possible to explain the distribution in regional ventilation and how the ventilation could be optimized right after the bronchoscopy to optimize the patient´s treatment.

Inclusion Criteria:

• Female and male patients > 18 years old
• Mechanically ventilated patients who routinely undergo bronchoscopy

Exclusion Criteria:

• Pregnancy and Breastfeeding
• Active implants, heart pace makers and implanted converter defibrillator
• Foreign metallic objects in the thorax
• Cardiac valves