Patient examinations using electrical impedance tomography—sources of interference in the intensive care unit
| Autor: | Sven Pulletz, Norbert Weiler, Alexander Frerichs, Gunnar Elke, Barbara Gawelczyk, Inéz Frerichs |
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| Rok vydání: | 2011 |
| Předmět: |
Male
Cardiac output Physiology Biomedical Engineering Biophysics Beds Signal Electromagnetic interference law.invention law Physiology (medical) Intensive care Electric Impedance Humans Medicine Waveform Cardiac Output Tomography Electrical impedance tomography Tidal volume Aged Monitoring Physiologic business.industry Air Respiration Middle Aged Thorax Intensive Care Units Anesthesia Ventilation (architecture) Female Artifacts business Biomedical engineering |
| Zdroj: | Physiological Measurement. 32:L1-L10 |
| ISSN: | 1361-6579 0967-3334 |
| Popis: | Electrical impedance tomography (EIT) is expected to become a valuable tool for monitoring mechanically ventilated patients due to its ability to continuously assess regional lung ventilation and aeration. Several sources of interference with EIT examinations exist in intensive care units (ICU). Our objectives are to demonstrate how some medical nursing and monitoring devices interfere with EIT measurements and modify the EIT scans and waveforms, which approaches can be applied to minimize these effects and how possible misinterpretation can be avoided. We present four cases of EIT examinations of adult ICU patients. Two of the patients were subjected to pulsation therapy using a pulsating air suspension mattress while being ventilated by high-frequency oscillatory or conventional pressure-controlled ventilation, respectively. The EIT signal modulation synchronous with the occurrence of the pulsating wave was 2.3 times larger than the periodic modulation synchronous with heart rate and high-frequency oscillations. During conventional ventilation, the pulsating mattress induced an EIT signal fluctuation with a magnitude corresponding to about 20% of the patient's tidal volume. In the third patient, interference with EIT examination was caused by continuous cardiac output monitoring. The last patient's examination was disturbed by impedance pneumography when excitation currents of similar frequency to EIT were used. In all subjects, the generation of functional EIT scans was compromised and interpretation of regional ventilation impossible. Discontinuation of pulsation therapy and of continuous cardiac output and impedance respiration monitoring immediately improved the EIT signal and scan quality. Offline processing of the disturbed data using frequency filtering enabled partial retrieval of relevant information. We conclude that thoracic EIT examinations in the ICU require cautious interpretation because of possible mechanical and electromagnetic interference. |
| Databáze: | OpenAIRE |
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