BCG Biosensor and Non- and Invasive Monitoring During Emergency Medicine Cases, a Prospective Feasibility Study

Pre-hospital monitoring of vital signs has documented to increase survival. Especially advanced multi-monitoring units have shown to have this impact but they are demanding in use. Low blood pressure/blood flow are frequent in emergency medicine cases and diagnosed by combining clinical evaluation (breathing, circulation, neurology) with biosensor measures of vital signs. Examples of biosensors are ECG, Ballistocardiographic (BCG), End Tidal CO2 (EtCO2), pulse oximetry (SpO2), saturation cerebral tissue oximetry (SctO2), transthoracic impedance (TTI), and invasive arterial pressure measurements such as pulse contour analysis for cardiac output measures. The gold standard for blood flow measurement is cardiac output [Cardiac Output (CO), volume of blood pumped by the heart pr. minute as the product of stroke volume (SV) and heart rate]. Cardiac output may be measured by invasive (thermodilution, Fick method) or noninvasively techniques [oesophageal Doppler, transoesophageal echocardiography, lithium dilatation cardiac output, pulse contour cardiac output (PICCO, Pulse Cardiac Output system, FloTrac ™), partial CO2 rebreathing, thoracic electrical bioimpedance. Pulse contour analysis is based on that the area under the systolic part of the arterial pressure waveform is proportional to the stroke volume (SV). This may limit the optimal goal for monitoring adequately several emergency medicine cases. There is, therefore, a need to develop and evaluate biosensor devices in these situations. BCG biosensors have been introduced and have documented to be useful in monitoring noninvasively vital signs but they have not been used in acute emergency medicine. It has been documented a correlation (r2=0.85) between BCG biosensor and cardiac output measured by Doppler echocardiogram. The biosensor record very subtle rhythmic movements on the patient skin (abdomen and/or neck) and shows a graph which is presented based on filters and custom-made algorithms as continuous hemodynamic variables (heart- and respiration-rates, heart rate variability, and relative stroke volume). BCG piezoelectric biosensors (BGPS) are easy to put on the patient, non-invasive, light (grams), small (2 x 2 cm), and costs are low. They support live streaming with automatic downloads of data. For most other measuring devices this must be done manually post event. With limited time of education and training all personnel prehospitally can deploy the biosensor over the carotid or abdominal aorta. Based on pilots and a validation study comparing two BCG biosensors (accelerometer and piezoelectric) with measures performed by present clinical practise the piezoelectric biosensor is best for use in situations where measures must be instant. In the same validation study, the investigators documented that pulse contour analysis with the latest software upgrade of FloTrac™ system worked well compared with Doppler echocardiography (manuscript in progress, ClinTrialGov). Studies have validated the efficacy of FloTrac ™ with pulmonary artery catheter and found different results. A review article concluded that FloTrac ™ has the possibility to increase patient safety in relation to perioperative hemodynamic monitoring. A comparison of simultaneous Stroke Volume (SV) and Cardiac Output measurements by echocardiography and FloTrac ™ were done in ten mechanically ventilated intensive care patients and showed a correlation between them (SV, y = 0.9545x + 3.3, R2 = 0.98 and for CO, y = 0.9104x + 7.7074, R² = 0.97). Therefore, it is indicated to use this biosensor for out of hospital cases. Although pulse contour analysis is an invasive method, the investigators have experience with invasive arterial access in the doctor car that respond to emergency cases in Oslo since invasive monitoring is the standard.

In a pre-hospital observational study performed by the doctor manned car (119-unit) in Oslo and Akershus, the investigators will compare and document (correlations, sensitivities, specificities) biosensor measures to current gold standard measures during cardiopulmonary resuscitation (CPR), hypotension, and intensive care transports. This challenges the current practice because most pre-hospital units responding to emergency medicine cases do not have alternatives to advanced measures. Therefore, the patient is not monitored well enough in addition to that they seldom receive instant guidance according to the effect of treatment. The investigators approach is novel and innovative since it has never been done but the investigators study group have recent experience with performing similar advanced clinical monitoring studies prehospitally. There is a potential that more pre-hospital units will deliver better monitoring and care to more patients with these non- and invasive approaches. Ultimately, better healthcare will be provided.

The data captured for the cardiac arrest patients will be compared with data from NCT02479152.

If the current project is successful, the investigators plan to implement this technology in a larger scale and may then be able to study potentially improved survival and morbidity rates with sufficient statistical power in future studies.