Wireless and cuffless monitoring of blood pressure in the operating room: the role of optical beat-to-beat technology

Authors
Yan Degiorgis1, Josep Solà2, Fabian Braun2, Nicolas Pierrel1, Christophe Verjus2, Mattia Bertschi2, Patrick Schoettker1


Background and Goal of Study:
Brachial cuff blood pressure measurement is the standard method for non-invasive hemodynamic measurement in the operating room, providing intermittent values with the risk of occulting hemodynamic instability. In case of necessity for beat-to-beat blood pressure readings, invasive intra-arterial monitoring is available. Photo-plethysmographic signals acquired at the fingertip are routinely recorded for pulse oximetry.  

The aim of this study is to demonstrate feasibility and efficacy of tracking beat-by-beat changes of blood pressure during induction of general anesthesia by simple optical means in comparison with an invasive arterial signal.

Materials and Methods: 
The study included 40 patients necessitating invasive arterial blood pressure monitoring for general anesthesia. Anesthesia was induced after arterial catheter had been inserted under local anesthesia, while photo-plethysmographic signals were acquired at the fingertip. A dedicated Pulse Wave Analysis (PWA) algorithm continuously generated blood pressure estimates that were further compared with reference readings provided by the arterial catheter. 

Results and Discussion:
Figures 1 illustrates the results of cuffless systolic blood pressure estimations compared to invasive arterial blood pressure references. Each data point corresponds to a patient’s heart beat. First row of each figure depicts correlation plots between invasive systolic blood pressure values and respectively, heart rate estimates and cuffless blood pressure estimates.

While comprehensive statistical analysis of the performances of the novel approach will be presented at finalization of the ongoing clinical study, preliminary results acquired on the first 30 patients support the hypothesis that blood pressure changes during general anesthesia can be reliably measured by dedicated PWA algorithms applied to fingertip photo-plethysmographic signals.

Conclusion(s): 
Estimating patients’ blood pressure changes in relation to induction of general anesthesia by means of a simple optical probe at the fingertip associated to a specific pulse-wave analysis is feasible and reliable.  
Experimental conditions were limited to induction of general anesthesia without major hemodynamic variations nor continuous vasopressive therapy. Further comparisons must be established to consider this device as an alternative to non invasive brachial cuff or arterial catheter.