Confirmatory Study of HFVI Guided Analgesic Administration in Surgical Subjects

Summary

Participation Requirements

Description

HFVi was designed to provide a standardized measure of the parasympathetic component (p?) of the Autonomous Nervous System (ANS). It tracts changes of the p? tonus induced by each respiratory cycle (spontaneous or artificial) to measure the relative balance of parasympathetic and sympathetic tone as...

HFVi was designed to provide a standardized measure of the parasympathetic component (p?) of the Autonomous Nervous System (ANS). It tracts changes of the p? tonus induced by each respiratory cycle (spontaneous or artificial) to measure the relative balance of parasympathetic and sympathetic tone as reflected in the EKG signal. These rapid changes of the p? tonus express themselves at the sinus node level by changes of the time interval separating two R waves of the electrocardiogram. The following normal RR intervals constitute the tachogram (displayed as respiratory pattern on the monitor). The p ? component is evaluated after filtering, standardization and re-sampling of the R-R series, by measuring the surface generated by respiratory cycles on the tachogram. Higher p? tonus is reflected as a larger measured surface area. In contrast, the measured surface decreases when the p? decreases. HFVi, a measure of the surface area, is expressed in the form of a dimensionless index ranging from 0 to 100. This index reflects the relative activity of the parasympathetic nervous system. It expresses the relative quantity of the present p? tonus compared to the Para and sympathetic tonus. The measure of HFVi displayed represents the average of a sequence of measurements: each elementary measure is realized on 64 seconds of data, updated each second using a sliding window. During development, a probabilistic interpretation of the HFVi was used to relate index values to a clinical state in an anesthetized subject. A significant hemodynamic response (increase of the heart rare or blood pressure of 20% compared to the baseline) within 10 minutes was used as an indicator of nociception/inadequate analgesia. As a measure of parasympathetic tone, HFVi may be influenced by many factors and thus be difficult to interpret in many of the following situations: arrhythmia no breathing (ex : apnea due to intubation) Respiratory rate lower than 9 cycles/min Tidal volume variable on the measuring time, thus 64 seconds Irregular breathing (when the patient speaks, laugh or cough) pace maker (some types) heart transplantation Drug use having a significant effect on the sinus cardiac activity

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