R. Logier

Validation of a graphic measurement of heart rate variability to assess analgesia/nociception balance during general anesthesia

The optimization of analgesic drugs delivery during general anesthesia (GA) requires to evaluate the pain/analgesia balance. Heart Rate Variability (HRV) analysis has long been shown to measure the autonomic nervous system tone, which is strongly influenced by anesthetic drugs. Power spectrum measurements are widely used to assess HRV low (LF) and high frequency (HF) ranges, related to the sympathetic and parasympathetic systems. We have developed an original graphic measurement technique (EnvTOT) of the ventilatory influence on the RR series. Measurements on simulated RR series showed that the graphic assessment is independent from respiratory rate, while LF and HF spectral measurements are over- and underestimated for respiratory rates lower than 12 cycles min Clinical measurements on 49 patients during GA showed that normalized HF power was strongly related to hemodynamic responsiveness during GA, and was strongly correlated with normalized EnvTOT measurements. A real time computation of the RR series could therefore help medical staff to anticipate hemodynamic responsiveness and the analgesia/nociception balance during GA.

Pain/analgesia evaluation using heart rate variability analysis.

The optimization of analgesic drugs delivery during general anesthesia requires to evaluate the pain/analgesia balance. Heart rate variability analysis has been shown in several studies to measure the autonomic nervous system tone, which is strongly influenced by anesthetic drugs. Recording RR series during general anesthesia enabled us to observe that the respiratory sinus arrhythmia pattern changed when a surgical stimulation was painful, even though the patient was not conscious. We developed a pain/analgesia evaluation algorithm based on the magnitude analysis of the respiratory patterns on the RR series. The parameters computed from this algorithm were recorded in thirty nine patients during general anesthesia. We retrospectively compared our parameters at different levels of analgesia during surgical stimulation, and found that they were related to pain/analgesia and relatively independent from other anesthesia related events like hypnosis and haemodynamic conditions

OFSETH: Optical Fibre Embedded into technical Textile for Healthcare, an efficient way to monitor patient under magnetic resonance imaging

Healthcare monitoring is a general concern for patients requiring a continuous medical assistance and treatment. In order to increase mobility of such patients, a huge effort is pursued worldwide for the development of wearable monitoring systems able to measure vital physiological parameters such as respiratory movements, cardiac activity, pulse oximetry, temperature of the body. Technical or smart textiles that incorporate different sensors play a growing role in these developments as they are well suited for wearability and can ensure comfort to the user. While most developments up to now have been focused on the use of electrical sensors, the aim of OFSETH is to take advantage of pure optical sensing technologies for extending the capabilities of medical technical textiles for wearable health monitoring. OFSETH expects to achieve a breakthrough in healthcare monitoring applications where standard (non-optical) monitoring techniques show significant limits such as for the monitoring of anesthetized patients under Medical Resonance Imaging (MRI).

An efficient algorithm for R-R intervals series filtering

Spectral analysis of heart rate variability (HRV) constitute a simple and non invasive way to study the autonomic nervous system (ANS) activity. On-line implementation of this technique would allow to follow the evolution of the ANS activity and to track transient events during medical procedures. However, continuous spectral analysis of HRV is not reliable enough due to the difficulty to obtain a noiseless ECG signal during a long period. Indeed, the consequential effects of each ECG signal perturbation on the R-R intervals gives an erroneous evaluation of HRV spectral analysis. In this article, we describe a real time filtering algorithm for R-R intervals series. This filter is able to detect each disturbed area and to replace the erroneous samples with the most probable ones. Therefore, this method allows detecting and replacing up to 90 % of R-R series erroneous samples while keeping the real recording time and without having any effect, beyond measure, on the frequency analysis result.

Effects of consecutive administration of central and peripheral anticholinergic agents on respiratory sinus arrhythmia in normal subjects

Respiratory sinus arrhythmia is thought to be vagally mediated, since it disappears after atropine, but the site of action of the drug (central vs. peripheral) accounting for this effect has not been elucidated. To investigate the effects of anticholinergic agents on respiratory arrhythmia, ten healthy subjects received an intravenous bolus of tropatepine (a presumed central antagonist) at a dose of 0.08 mg per kg of body weight, then, 7 min later, prifinium (a peripheral antagonist) at a dose of 0.1 mg per kg of body weight. Respiratory sinus arrhythmia during controlled breathing was evaluated as the area under the high-frequency peak of the heart rate variability spectrum coinciding with the respiratory frequency +/- 0.02 Hz. The power of this high-frequency peak decreased by 55% after tropatepine (P less than 0.05) with a concomitant increase of the mean RR interval from 930 to 1072 ms (P less than 0.01). When prifinium was added, a further but non-significant decrease of respiratory arrhythmia was observed, while the mean RR interval decreased from 1072 to 714 ms (P less than 0.01). The low-frequency components (0.05 to 0.15 Hz) of the power spectrum, significantly decreased (P less than 0.05) after infusion of both drugs. In conclusion, tropatepine depresses respiratory sinus arrhythmia with a paradoxical concomitant bradycardia. This suggests that tropatepine acts like a pure central muscarinic antagonist, in support of the hypothesis that a central cholinergic receptor is involved in the respiratory modulation of heart rate.

Optical fibre sensors embedded into technical textile for a continuous monitoring of patients under Magnetic Resonance Imaging

The potential impact of optical fiber sensors embedded into medical textiles for the continuous monitoring of the patient during Magnetic Resonance Imaging (MRI) is presented. In that way, we report on several pure optical sensing technologies for pulse oximetry and respiratory movements monitoring. The technique for pulse oximetry measurement is known as NIRS (Near Infra-Red Spectroscopy) in a reflectance mode. On the other hand, we tested two different optical based designs for the respiratory motions measurements - a macro bending sensor and a Bragg grating sensor, designed to measure the elongation of thoracic and abdominal circumferences during breathing.

PhysioTrace: An efficient toolkit for biomedical signal processing

Healthcare monitoring applications requires the measurement and the analysis of multiple physiological data. In the field of biomedical research, these data are issued from different devices involving data centralization and synchronization difficulties. On the other hand, the analysis of the acquired data requires high level digital signal processing tools. In this paper we describe a real time toolkit for biomedical data acquisition, centralization, processing and visualization. This toolkit, composed of both hardware and software modules, allows users to model, test and perform all kind of digital signal processing algorithms for all kind of biomedical signals. These highly efficient hardware and software modules have been developed and tested especially for biomedical studies and used in a large number of clinical investigations. So, for developers, using such a toolkit will reduce the development time while increasing the application performances

Smart Textile Embedding Optical Fibre Sensors for Healthcare Monitoring during MRI

The potential impact of optical fibre sensors embedded into medical textiles for the continuous monitoring of the patient during Magnetic Resonance Imaging (MRI) is presented. In that way, we report on several pure optical sensing technologies for pulse oximetry and respiratory movements monitoring. The technique for pulse oximetry measurement is known as NIRS (Near Infra-Red Spectroscopy) in a reflectance mode. In parallel, we tested two different optical sensor based fabric designs breathing activity detection – a macro bending sensor and a fibre Bragg grating sensor consisting in respiratory frequency measurement by intensity variation detection and optical spectral analysis.

Fetal distress diagnosis using heart rate variability analysis: Design of a High Frequency Variability Index

Routine monitoring of Fetal Heart Rate (FHR) during labor enables diagnosis of fetal distress and appropriate management by the medical staff. Diagnosis of fetal distress relies mainly on a subjective visual assessment of FHR variations using baseline level, oscillations magnitude, decelerations and their time-relation to the parturient uterine contractions. Strong intra and inter-observer discrepancies exist with this widely used technique, and sometimes requires fetal scalp blood sample pH measurement, which is not fully reliable either. Gold standard assessment of fetal distress relies on blood pH measurement after the birth. In this paper we describe a new method for fetal distress diagnosis based on FHR variability analysis, measuring the high frequency content of FHR as a High Frequency Variability Index (HFVI). We tested this new index on 21 fetuses where FHR was recorded during labor for an observational clinical trial. FHR recordings were separated in two groups given the fetal arterial pH obtained after birth: group 1 - no distress, pH ⩾ 7.15, N=16 and group 2 - fetal distress, pH < 7.15, N=5. The new index was significantly higher in group 1 than in group 2 (non parametric Mann Whitney U-test, p=0.01).

Automated analgesic drugs delivery guided by vagal tone evaluation: Interest of the Analgesia Nociception Index (ANI).

Analgesic drugs delivery optimization constitutes one of the main objectives of modern anesthesia. Indeed, their over or under determination constitutes a risk for anesthetized patient in terms of hemodynamic reactivity or post-operative hyperalgesia. Nowadays, new physiological indexes allow anesthesiologists to evaluate the balance between the analgesia level and the noxious stimulus importance. A I is an index related to the autonomic nervous system activity based on heart rate variability analysis. Its ability for the analgesia / nociception balance evaluation has been established bringing evidences about its helpfulness for analgesic drug delivery. In this article, we describe a device for automatic analgesic drugs administration based on the A I evolution during surgical procedures under general anesthesia. We hypothesized that such a device could improve the quality and safety of anesthesia by reducing adverse cardiovascular events and delivered analgesic drugs doses.