A comparison of a prototype electromyograph vs. a mechanomyograph and an acceleromyograph for assessment of neuromuscular blockade.

The extent of neuromuscular blockade during anaesthesia is frequently measured using a train-of-four stimulus. Various monitors have been used to quantify the train-of-four, including mechanomyography, acceleromyography and electromyography. Mechanomyography is often considered to be the laboratory gold standard of measurement, but is not commercially available and has rarely been used in clinical practice. Acceleromyography is currently the most commonly used monitor in the clinical setting, whereas electromyography is not widely available. We compared a prototype electromyograph with a newly constructed mechanomyograph and a commercially available acceleromyograph monitor in 43 anesthetised patients. The mean difference (bias; 95% limits of agreement) in train-of-four ratios was 4.7 (-25.2 to 34.6) for mechanomyography vs. electromyography; 14.9 (-13.0 to 42.8) for acceleromyography vs. electromyography; and 9.8 (-31.8 to 51.3) for acceleromyography vs. mechanomyography. The mean difference (95% limits of agreement) in train-of-four ratios between opposite arms when using electromyography was -0.7 (-20.7 to 19.3). There were significantly more acceleromyography train-of-four values > 1.0 (23%) compared with electromyography or mechanomography (2-4%; p < 0.0001). Electromyography most closely resembled mechanomyographic assessment of neuromuscular blockade, whereas acceleromyography frequently produced train-of-four ratio values > 1.0, complicating the interpretation of acceleromyography results in the clinical setting.

Quantifying Real-World Upper-Limb Activity Via Patient-Initiated Movement After Nerve Reconstruction for Upper Brachial Plexus Injury.

BACKGROUND: A critical concept in brachial plexus reconstruction is the accurate assessment of functional outcomes. The current standard for motor outcome assessment is clinician-elicited, outpatient clinic-based, serial evaluation of range of motion and muscle power. However, discrepancies exist between such clinical measurements and actual patient-initiated use. We employed emerging technology in the form of accelerometry-based motion detectors to quantify real-world arm use after brachial plexus surgery. OBJECTIVE: To evaluate (1) the ability of accelerometry-based motion detectors to assess functional outcome and (2) the real-world arm use of patients after nerve transfer for brachial plexus injury, through a pilot study. METHODS: Five male patients who underwent nerve transfer after brachial plexus injury wore bilateral motion detectors for 7 d. The patients also underwent range-of-motion evaluation and completed multiple patient-reported outcome surveys. RESULTS: The average age of the recruits was 41 yr (±17 yr), and the average time from operation was 2 yr (±1 yr). The VT (time of use ratio) for the affected side compared to the unaffected side was 0.73 (±0.27), and the VM (magnitude ratio) was 0.63 (±0.59). VT strongly and positively correlated with shoulder flexion and shoulder abduction: 0.97 (P = .008) and 0.99 (P = .002), respectively. CONCLUSION: Accelerometry-based activity monitors can successfully assess real-world functional outcomes after brachial plexus reconstruction. This pilot study demonstrates that patients after nerve transfer are utilizing their affected limbs significantly in daily activities and that recovery of shoulder function is critical.

Novel Wearable Seismocardiography and Machine Learning Algorithms Can Assess Clinical Status of Heart Failure Patients.

BACKGROUND: Remote monitoring of patients with heart failure (HF) using wearable devices can allow patient-specific adjustments to treatments and thereby potentially reduce hospitalizations. We aimed to assess HF state using wearable measurements of electrical and mechanical aspects of cardiac function in the context of exercise. METHODS AND RESULTS: Patients with compensated (outpatient) and decompensated (hospitalized) HF were fitted with a wearable ECG and seismocardiogram sensing patch. Patients stood at rest for an initial recording, performed a 6-minute walk test, and then stood at rest for 5 minutes of recovery. The protocol was performed at the time of outpatient visit or at 2 time points (admission and discharge) during an HF hospitalization. To assess patient state, we devised a method based on comparing the similarity of the structure of seismocardiogram signals after exercise compared with rest using graph mining (graph similarity score). We found that graph similarity score can assess HF patient state and correlates to clinical improvement in 45 patients (13 decompensated, 32 compensated). A significant difference was found between the groups in the graph similarity score metric (44.4±4.9 [decompensated HF] versus 35.2±10.5 [compensated HF]; P<0.001). In the 6 decompensated patients with longitudinal data, we found a significant change in graph similarity score from admission (decompensated) to discharge (compensated; 44±4.1 [admitted] versus 35±3.9 [discharged]; P<0.05). CONCLUSIONS: Wearable technologies recording cardiac function and machine learning algorithms can assess compensated and decompensated HF states by analyzing cardiac response to submaximal exercise. These techniques can be tested in the future to track the clinical status of outpatients with HF and their response to pharmacological interventions.

Stretchable E-Skin Apexcardiogram Sensor.

A new strategy to measure the apex cardiogram with electronic skin technology is presented. An electronic skin apexcardiogram sensor, which can compensate the conventional electrocardiogram for cardiac diagnosis, is demonstrated through a highly sensitive and stretchable strain sensor with gold-nanoparticle composites.

A Wearable Patch to Enable Long-Term Monitoring of Environmental, Activity and Hemodynamics Variables.

We present a low power multi-modal patch designed for measuring activity, altitude (based on high-resolution barometric pressure), a single-lead electrocardiogram, and a tri-axial seismocardiogram (SCG). Enabled by a novel embedded systems design methodology, this patch offers a powerful means of monitoring the physiology for both patients with chronic cardiovascular diseases, and the general population interested in personal health and fitness measures. Specifically, to the best of our knowledge, this patch represents the first demonstration of combined activity, environmental context, and hemodynamics monitoring, all on the same hardware, capable of operating for longer than 48 hours at a time with continuous recording. The three-channels of SCG and one-lead ECG are all sampled at 500 Hz with high signal-to-noise ratio, the pressure sensor is sampled at 10 Hz, and all signals are stored to a microSD card with an average current consumption of less than 2 mA from a 3.7 V coin cell (LIR2450) battery. In addition to electronic characterization, proof-of-concept exercise recovery studies were performed with this patch, suggesting the ability to discriminate between hemodynamic and electrophysiology response to light, moderate, and heavy exercise.

New relative intensity ambulatory accelerometer thresholds for elderly men and women: the Generation 100 study.

BACKGROUND: Public health initiatives world-wide recommend increasing physical activity (PA) to improve health. However, the dose and the intensity of PA producing the most benefit are still debated. Accurate assessment of PA is necessary in order to 1) investigate the dose-response relationship between PA and health, 2) shape the most beneficial public health initiatives and 3) test the effectiveness of such initiatives. Actigraph accelerometer is widely used to objectively assess PA, and the raw data is given in counts per unit time. Count-thresholds for low, moderate and vigorous PA are mostly based on absolute intensity. This leads to largely inadequate PA intensity assessment in a large proportion of the elderly, who due to their declining maximal oxygen uptake (VO2max) cannot reach the moderate/vigorous intensity as defined in absolute terms. To resolve this issue, here we report relative Actigraph intensity-thresholds for the elderly. METHODS: Submaximal-oxygen-uptake, VO2max and maximal heart rate (HRmax) were measured in 111 70-77 year olds, while wearing an Actigraph-GT3X+. Relationship between VO2max percentage (%), counts-per-minute (CPM) and gender (for both the vertical-axis (VA) and vector-magnitude (VM)) and VO2max% and HRmax% was established using a mixed-regression-model. VM-and VA-models were tested against each other to see which model predicts intensity of PA better. RESULTS: VO2max and gender significantly affected number of CPM at different PA intensities (p < 0.05). Therefore, intensity-thresholds were created for both men and women of ranging VO2max values (low, medium, high). VM-model was found to be a better predictor of PA-intensity than VA-model (p < 0.05). Established thresholds for moderate intensity (46-63 % of VO2max) ranged from 669-3367 and 834-4048 CPM and vigorous intensity (64-90 % of VO2max) from 1625-4868 and 2012-5423CPM, for women and men, respectively. Lastly, we used this evidence to derive a formula that predicts customized relative intensity of PA (either VO2max% or HRmax%) using counts-per-minute values as input. CONCLUSION: Intensity-thresholds depend on VO2max, gender and Actigraph-axis. PA intensity-thresholds that take all these factors into account allow for more accurate relative intensity PA assessment in the elderly and will be useful in future PA research. TRIAL REGISTRATION: (ClinicalTrials.gov Identifier: NCT02017847, registered 17. December 2013).

The efficacy of several neuromuscular monitoring modes at the P6 acupuncture point in preventing postoperative nausea and vomiting.

BACKGROUND: In this study, we tested the efficacy of several neuromuscular monitoring modes at the P6 acupuncture point for preventing postoperative nausea and vomiting (PONV). METHODS: In this prospective, double-blind, randomized, placebo-controlled trial, 264 women undergoing laparoscopic hysterectomy were evaluated for PONV. Neuromuscular blockade was monitored by acceleromyography with 1-Hz single twitch (ST) over the ulnar nerve (n = 54, control), and ST (n = 52), train-of-four (n = 53), double-burst stimulation (n = 53), or tetanus (n = 52) over the median nerve stimulating at the P6 acupuncture point. RESULTS: The incidence of PONV (P = 0.022), the number of requests for patient-controlled analgesia (P = 0.009), and total patient-controlled analgesia volume (P = 0.042) 6 hours after tetanic stimulation were significantly reduced in the treatment group compared with the control group. Overall, patients in the tetanus group were more satisfied with the management of PONV compared with patients in the control group. CONCLUSION: Tetanic stimulation applied to the P6 acupuncture point can reduce PONV after laparoscopic hysterectomy compared with ST stimulation of the ulnar nerve, resulting in a greater degree of patient satisfaction. None of the stimulations, ST, train-of-four, or double-burst, applied to the P6 acupuncture point significantly affected PONV.

Recognition of activities in children by two uniaxial accelerometers in free-living conditions.

The aim of this study was to develop a classification procedure for accelerometer data to recognize the mode of children's physical activity (PA) in free-living conditions and to compare it with an established cutoff method. Hip and wrist accelerometer data with an epoch interval of 1 s were collected for 7 days from 24 girls (age: 10.7 ± 1.7 years) and 17 boys (age: 10.6 ± 1.6 years). Videos were recorded during the same 7 days at several points of time at school and during leisure time. Each second of video data was labeled as one of nine activity classes. A classification procedure based on pattern recognition algorithms was trained with the accelerometer data relating to respective video labels of half of the children and tested against the data from the other half of the children. The overall recognition rate of the classification procedure was 67%. The procedure was able to classify 90% of stationary activities, 83% of walking, 81% of running and 61% of jumping activities. The remaining activities could not be recognized by the main classifier. This study developed a classification procedure based on well-accepted accelerometers and video recordings to recognize children's PA in free-living conditions. It has been shown to be valid for the activities of being stationary, walking, running and jumping. In contrast to former measurement and analysis procedures, this method is able to determine the modes of specific activities among children. Consequently, the presented classification procedure provides additional information on the PA behavior in children registered by established accelerometers.

Utility of the actiheart accelerometer for estimating exercise energy expenditure in female adolescent runners.

There is a growing need to accurately assess exercise energy expenditure (EEE) in athletic populations that may be at risk for health disorders because of an imbalance between energy intake and energy expenditure. The Actiheart combines heart rate and uniaxial accelerometry to estimate energy expenditure above rest. The authors' purpose was to determine the utility of the Actiheart for predicting EEE in female adolescent runners (N = 39, age 15.7 ± 1.1 yr). EEE was measured by indirect calorimetry and predicted by the Actiheart during three 8-min stages of treadmill running at individualized velocities corresponding to each runner's training, including recovery, tempo, and 5-km-race pace. Repeated-measures ANOVA with Bonferroni post hoc comparisons across the 3 running stages indicated that the Actiheart was sensitive to changes in intensity (p < .01), but accelerometer output tended to plateau at race pace. Pairwise comparisons of the mean difference between Actiheart- and criterion-measured EEE yielded values of 0.0436, 0.0539, and 0.0753 kcal × kg-1 × min-1 during recovery, tempo, and race pace, respectively (p < .0001). Bland-Altman plots indicated that the Actiheart consistently underestimated EEE except in 1 runner's recovery bout. A linear mixed-model regression analysis with height as a covariate provided an improved EEE prediction model, with the overall standard error of the estimate for the 3 speeds reduced to 0.0101 kcal × kg-1 × min-1. Using the manufacturer's equation that combines heart rate and uniaxial motion, the Actiheart may have limited use in accurately assessing EEE, and therefore energy availability, in young, female competitive runners.

A personalized approach to exercise promotion in adolescents with type 1 diabetes.

PURPOSE: This exploratory study tested the feasibility of conducting a novel, personalized exercise intervention based upon the current fitness levels of adolescents with type 1 diabetes (T1DM). The relationships of perceptions of benefits and barriers to exercise, exercise self-efficacy and family support to exercise adherence and changes in cardiovascular (CV) fitness, quality of life (QOL), and glycemic control were studied. METHODS: Adolescents who were sedentary received a graded exercise test to determine their current fitness level (VO(2peak)). A 16-wk personalized exercise program was developed for each adolescent based upon individual fitness level and exercise preferences. Pretest and posttest measures of exercise self-efficacy, benefits and barriers to exercise, family support, and diabetes QOL were completed. A1c levels were obtained using the DCA2000. Adherence to exercise was measured using the Actigraph Accelerometer. RESULTS: Twelve adolescents completed the study. Accelerometry data revealed adherence to 60 min of moderate-to-vigorous physical activity (MVPA) per day for a mean of 45.5 (SD = 23.9)% of the days the accelerometer was worn. Adolescents' perceptions of family support for exercise improved following the intervention (p = 0.03). Adolescents who had more daily bouts of exercise lasting 60 min increased their CV fitness (r = 0.59, p = 0.04). A1c remained unchanged. CONCLUSIONS: Encouraging 60 min of accumulated exercise bouts/d can improve fitness levels in adolescents with T1DM, minimizing future CV risks. Although physical activity increased in adolescents, family based strategies are required to promote current physical activity recommendations.

Non-contact cardiac monitoring from carotid artery using optical vibrocardiography.

The aim of the present work is to establish a protocol for monitoring the cardiac activity measuring the skin surface vibrations of the main neck vessels, caused by vascular wall motion in carotid artery. The method is based on the optical recording of the movements of the neck by means of laser Doppler interferometry. The ECG signal and the velocity of vibration of the skin in correspondence of the carotid artery (named optical vibrocardiography: VCG) have been simultaneously recorded on five healthy subjects. Standard heart rate variability tests have been carried out. The capability of VCG signals to be used as a surrogate of the ECG in assessing both cardiac rate and heart rate variability (HRV) has been tested using time and spectral descriptors, and specific statistical analysis. Mean differences have been found lower than 3.13%. Optical vibrocardiography might be a simple approach to the clinical practice of cardiovascular screening, in particular in harsh environment, such as MR clinical practice, where ECG recordings are corrupted by artefacts and ECG cables might represent an hazard for the patients.

Monitoring and analysis of cardio respiratory and snoring signals by using an accelerometer.

In this paper we present a system based on a sensor of acceleration for acquisition and monitoring of diverse physiological signals, by extracting respiratory, cardiac and snoring components inside the main source. Digital signal processing techniques used frequently in Biomedical Engineering have been used. The acceleration produced by the cardiac signals, the respiratory movements and the vibrations generated by the snores are detected with help of an accelerometer placed on the skin of the subject in not invasive way. The presented device allows the monitoring of several biomedical parameters: heart rate (HR), heart rate variability (HRV), Sympathetic, parasympathetic and baroreflex activity, respiratory rhythms and their variations (bradypnea - tachypnea), snoring and abdominal-thoracic efforts. A simple and effective method and device [1] is provided for helping to the diagnosis of Sleep Apnea-Hypopnea Syndrome (SAHS) and other breathing disorders.

Wearable seismocardiography.

Seismocardiogram (SCG) is the recording of body vibrations induced by the heart beat. SCG contains information on cardiac mechanics, in particular heart sounds and cardiac output. In this paper we present a new wearable device for SCG recordings during long term monitorings, and the results of a validation test in 4 subjects. The system is based on the integration of the MagIC smart shirt (i.e., a textile-based wearable system for the assessment of ECG and respiratory movements), and an external triaxial MEMS accelerometer positioned on the left clavicle. SCG was estimated as the average of accelerations occurred in each heart beat. The SCG components due to the valve closure and to recoil forces following the heart contraction (ballistocardiogram) were extracted by high-pass (>18 Hz) and band-pass (0.6-20 Hz) filters respectively. Then the difference between the I and J waves of the ballistocardiogram (|I-J| index, possibly related to the cardiac output) was identified by an ad-hoc procedure and compared with the model flow indirect estimation of cardiac output. Validation on 4 volunteers showed that: 1) our wearable system provides statistically consistent estimates of both heart-sound related vibrations and recoil movements; 2) reliable estimates of the |I-J| index can be obtained by considering about 1 minute of SCG recording in stationary conditions; and 3) changes of the |I-J| index during exercise correlate well with changes of cardiac output estimated by the model flow.

[Monitoring of vital patient's functions by contact-free sensors]. / Monitoring zhiznennykh funktsii patsienta s ispol'zovaniem sensorov nekontaktnogo tipa.

An experimental device was constructed as well as hardware and software were designed to register the functional state parameters, i.e. external respiration functions, rhythmic heart activity and general motor activity (including the spastic and epileptic variations), when there is no direct galvanic contact with the patient's body.

Dynamical MCG mapping with an atomic vapor magnetometer.

We have developed a magnetometer based on magnetic resonance in cesium vapor optically pumped by resonant laser radiation, which has the sensitivity and bandwidth to record human magnetocardiograms. The device is operated as a first-order gradiometer in a weakly shielded environment and allows us to record 2-dimensional field maps by shifting the subject with respect to a single sensor and making time-sequential measurements. We discuss the magnetometer technique and its performance as well as obtained results, which include a comparison of MCG data recorded with our single channel optical magnetometer with SQUID measurements from a commercial multi-channel device as well as from SQUID reference data. The results obtained so far in the detection of cardiomagnetic signals using the optical magnetometer make us confident that the technique has a high potential to serve as an alternative to SQUID detection.

[Kinetocardiotocography--KCTG--during pregnancy in an ambulatory care patient sample and in hospitalized patients with special reference to tocolysis]. / Kinetokardiotokografie-KCTG--im Schwangerschaftsverlauf bei einem ambulantbetreuten und einem hospitalisierten Kollektiv unter besonderer Berücksichtigung der Tokolyse.

With kinetocardiotocography (KCTG), fetal movements can be registered parallel to the fetal heart rate. Hewlett Packard equipment of the series 1350 A allows the movements to be registered an quantified on the CTG paper. In this study, hospitalized pregnant women > 26 gestational weeks (GW) on i.v. tocolysis, and out-patients > 34 GW at the out patient department were examined with KCTG and the results compared. A wide distribution of fetal activity was seen in both groups. With advancing pregnancy, the number of fetal movements as well as the duration of activity per time unit decreased, whereas the length of time of individual movements slightly increased, in both groups. No statistically significant difference was seen between different gestational ages nor between the two groups. KCTG is being increasingly used to monitor the fetal condition, especially for risk pregnancies. It can provide additional information in the form of a biophysical variable.

A useful method for measuring daily physical activity by a three-direction monitor.

The purpose of this study was to investigate whether a three-direction accelerometer is useful for measuring daily physical activity. Physical activity, being an important part of human behavior, may be related to various aspects of health and disease. In this study, the relationship between the intensity of each action and the three-direction accelerometer (Actigraph) output was compared in 10 healthy subjects under free-living conditions. Subjects wore the Actigraph on their non-dominant wrist and filled out a physical activity check list (self-report) throughout the daytime. Daily physical activities were classified into six categories according to different intensities. The differences of the Actigraph output among each of the six categories were significant by the Kruskal-Wallis analysis (p = 0.001). The Actigraph output appeared to correlate highly with the intensity of actions by the Spearman Rank test (r = 0.95, p < 0.05). The Actigraph output was over-estimated while the subjects were typing, driving and being a passenger in a motor vehicle. The Actigraph was shown to be a useful and convenient device for measuring daily physical activity.