A new device for measuring dermal blood flow in critically ill patients

A new monitor, the Dermal Blood Flow (DBF) meter, which non-invasively (skin probe) assesses capillary flow, has recently been developed and used in a variety of medical settings, including the assessment of wound perfusion during surgery and peripheral perfusion in patients with vascular conditions. We tested the monitor in the ICU setting, where early and objective evidence of altered skin perfusion may provide important information regarding impending impairment of organ function, and compared it with the mean arterial blood pressure (MAP).

Methods

Ten critically ill patients were included in the study, which involved the continuous recording of minute-by-minute measurement of DBF and MAP (Datex-Ohmeda). The effect of specific interventions on both the measures, such as the giving of fluid boluses or vasopressors, was noted. We determined efficacy in terms of correlation between DBF and MAP (overall impression between the series graphs, and graded from rarely change together to nearly always change together), reliability (evaluated by a precision test of two randomly selected segments for each patient where the coefficient of variation is defined as the percentage of measurement error to mean results) and sensitivity analysis (any response to a specific intervention such as fluid bolus or use of vasopressor).

Results

The MAP and DBF changed together mostly or nearly always throughout the recording for seven of the 10 patients. The DBF showed superior precision (1.5%, 95% CI 1.1–2.0%) when compared with MAP (2.2%, CI 1.7–3.0%). Response to 16 interventions in all the patients was detected by a change in DBF in 13 observations and by a change in MAP in only 11 observations. The response to vasopressors was always detected while the response to fluid administration was less well detected by both measures.

Conclusions

This preliminary study has shown that the noninvasive DBF monitor was sensitive to therapeutic interventions in critically ill patients and was more reliable than MAP. Further studies comparing DBF with other modalities of peripheral perfusion are presently being performed.