Thoracic, Peripheral, and Cerebral Volume, Circulatory and Pressure Responses To PEEP During Simulated Hemorrhage in a Pig Model: a Case Study

Rheoencephalography: A non-invasive method for neuromonitoring

In neurocritical care, the gold standard method is intracranial pressure (ICP) monitoring for the patient's lifesaving. Since it is an invasive method, it is desirable to use an alternative, noninvasive technique. The computerized real-time invasive cerebral blood flow (CBF) autoregulation (AR) monitoring calculates the status of CBF AR, called the pressure reactivity index (PRx). Studies documented that the electrical impedance of the head (Rheoencephalography - REG) can detect the status of CBF AR (REGx) and ICP noninvasively. We aimed to test REG to reflect ICP and CBF AR. For nineteen healthy subjects we recorded bipolar bifrontal and bitemporal REG derivations and arm bioimpedance pulses with a 200 Hz sampling rate. The challenges were a 30-second breath-holding and head-down-tilt (HDT - Trendelenburg) position. Data were stored and processed offline. REG pulse wave morphology and REGx were calculated. The most relevant finding was the significant morphological change of the REG pulse waveform (2nd peak increase) during the HDT position. Breath-holding caused REG amplitude increase, but it was not significant. REGx in male and female group averages have similar trends during HDT by indicating the active status of CBF AR. The morphological change of REG pulse wave during HDT position was identical to ICP waveform change during increased ICP, reflecting decreased intracranial compliance. A correlation study between ICP and REG was initiated in neurocritical care patients. The noninvasive REG monitoring would also be useful in space research as well as in military medicine during the transport of wounded service members as well as for fighter pilots to indicate the loss of CBF and consciousness.

Noninvasive neuromonitoring with rheoencephalography: a case report

Cerebral blood flow (CBF) autoregulation (AR) can be monitored using invasive modalities, such as intracranial pressure (ICP) and arterial blood pressure (ABP) to calculate the CBF AR index (PRx). Monitoring PRx can reduce the extent of secondary brain damage in patients. Rheoencephalography (REG) is an FDA-approved non-invasive method to measure CBF. REGx, a CBF AR index, is calculated from REG and arm bioimpedance pulse waves. Our goal was to test REG for neuromonitoring. 28 measurement sessions were performed on 13 neurocritical care patients. REG/arm bioimpedance waveforms were recorded on a laptop using a bioimpedance amplifier and custom-built software. The same program was used for offline data processing. Case #1: The patient's mean REGx increased from - 0.08 on the first day to 0.44 on the second day, indicating worsening intracranial compliance (ICC) (P < 0.0001, CI 0.46-0.58). Glasgow Coma Scale (GCS) was 5 on both days. Case #2: REGx decreased from 0.32 on the first recording to 0.07 on the last (P = 0.0003, CI - 0.38 to - 0.12). GCS was 7 and 14, respectively. Case #3: Within a 36-minute recording, REGx decreased from 0.56 to - 0.37 (P < 0.0001, 95%, CI - 1.10 to - 0.76). Central venous pressure changed from 14 to 9 mmHg. REG pulse wave morphology changed from poor ICC to good ICC morphology. Bioimpedance recording made it possible to quantify the active/passive status of CBF AR, indicate the worsening of ICC, and present it in real time. REGx can be a suitable, non-invasive alternative to PRx for use in head-injured patients.