"Early Non-Invasive Microcirculation-based Detection"

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Our dermal blood flow (DBF) monitor underwent proof-of-concept testing in 10 critically ill patients in the general medical ICU at Rabin Medical Center,Petach Tikva, Israel1. Reduced organ perfusion is a feature of worsening clinical status in ICU patients. In order to assess the ability of DBF to detect changes in organ perfusion, it was compared to the current gold standard, invasively recorded mean arterial pressure (MAP). Continuous minute-by-minute noninvasive measurement of DBF and MAP were recorded. The effect of specific interventions, such as fluid boluses or vasopressors, on both the measures was noted. Efficacy was determined in terms of correlation between DBF and MAP data series graphs, and graded from "rarely change together" to "nearly always change together"; reliability was evaluated by a precision test of two randomly selected segments for each patient, where the coefficient of variation was defined as the percentage ratio of measurement error to mean results; and sensitivity analysis was made by assessing any response to a specific intervention, such as fluid bolus or use of vasopressor.

Results:

  • MAP and DBF changed together mostly/nearly always during recording for 7 of 10 patients.
  • DBF showed superior precision when compared with MAP. For 16 interventions in all the patients, DBF detected changes associated with 13 interventions whereas MAP changed in only 11 observations.
  • The response to vasopressors was always detected while the response to fluid administration was less well detected by both measures.

Of particular interest was the ability of DBF to provide rapid alerts, as aptly demonstrated in this recording made from a patient who expired. DBF values appeared to be a significantly better predictor of patient death than MAP (see graph below).

Clinical indication of a serious negative change in the patient's health status, as observed through decreased DBF values versus MAP's values continuing unchanged at baseline, occurred approximately 100 minutes prior to the patient's death. Neither MAP nor any of the other typically measured critical care parameters showed any changes in the patient's condition until just prior to death. This example highlights the significant potential value anticipated from this device as an early detector of worsening clinical status.

Not only is DBF sensitive to changes in organ perfusion, but sensitivity to changes in tissue perfusion has also been demonstrated. In an additional proof-of-concept study performed at Washington University, St. Louis, MO, 56 colon resection patients were studied postoperatively to assess whether aggressive intraoperative fluid administration during surgery increased tissue oxygen levels surrounding the wound, thereby potentially leading to faster recovery2. The authors stated that DBF correlated well with tissue oxygen partial pressure, and it is indicated that DBF also correlated well with MAP, as in the Rabin Medical Center study.

These studies were published in well respected peer-reviewed journals as below:

1A new device for measuring dermal blood flow in critically ill patients. Cohen J, Skoletsky I, Geva D, Ephrath H and Singer P. Department of General Intensive Care, Rabin Medical Center, Campus Beilinson, Petah Tikva and the Sackler School of Medicine, Tel Aviv University, Israel. From 23rd International Symposium on Intensive Care and Emergency Medicine, Brussels, Belgium. 18-21 March 2003, Critical Care 2003, 7(Suppl 2):P195, 3 March 2003

2Supplemental perioperative fluid administration increases tissue oxygen pressure. Arkilic CF, Taguchi A, Sharma N, et al. Surgery 133(1); 49-55, 2003.

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