Thoracic Impedance Research Articles

Standardization of transthoracic impedance values for estimating heart failure and its utility

Abstract Background The use of intrathoracic impedance for examining pleural effusion in heart failure patients has been explored previously. However, due to concerns about its accuracy and complexity, transthoracic impedance values have had limitations in quantifying extravascular lung water. Our dual objectives were to clarify the relationship between intrathoracic conditions and percutaneous transthoracic impedance values, and to establish a basic model for a new machine learning-based estimation system for assessing intrathoracic conditions in patients with heart failure. Methods First, we developed a live porcine congested lung model that induced pleural effusion by substantial fluid loading, and then longitudinally evaluated its correlation with percutaneous transthoracic impedance values. Second, we conducted multi-frequency bioelectrical impedance analysis to simultaneously collect electrical, physical, and hematological data from 63 hospitalized heart failure patients and 82 healthy volunteers Results In the porcine model, pleural effusion correlated with a concurrent decrease in SpO2 and a gradual decrease in impedance. We indexed and generated features from the measured values and developed an intrathoracic estimation model based on electrical measurements and clinical findings using a decision tree-based machine learning approach. Among the 286 features collected per individual, the model used 16 features. Notably, the model demonstrated high accuracy in discriminating patients with pleural effusion, achieving an AUC of 0.905 (95% CI: 0.870-0.940) in cross-validation, significantly outperforming the conventional frequency-based method. Conclusions Transthoracic impedance values, when indexed, reflect intrathoracic conditions and improve estimation. Our results highlighted the potential of machine learning and thoracic impedance measurement for accurate estimation of pleural effusion. This approach provides an effective means of assessing intrathoracic conditions. Figure: The upper figure shows the relationship between impedance values and pleural effusion in the congested lung model. On these results, human data were collected to construct the estimation model. The lower illustrates the accuracy of the model and provides a comprehensive view of the system.

Enhancing Heart Failure Diagnosis Accuracy and Distinguishing It From Other Pulmonary Conditions: A Retrospective Case Series Study Leveraging the HeartLogic Parameters.

Introduction Heart failure (HF) poses a substantial and escalating medical and economic challenge, marked by significant morbidity and mortality. It stands as the primary cause of hospital admissions among the elderly, contributing significantly to healthcare expenditures in developed nations. Evaluating cardiac and pulmonary function remains challenging, necessitating careful interpretation to mitigate misdiagnosis and inappropriate treatment. Remote monitoring has emerged as a preventive strategy to curb HF-related hospitalizations, emphasizing the importance of early detection of impending acute HF decompensation. Implantable cardiac defibrillators (ICDs) capture various parameters, including heart rhythm, pacing percentages, thoracic impedance, and physical activity. Objective In this study, we aim to investigate the effectiveness of HeartLogic (Boston Scientific, Marlborough, Massachusetts) parameters in accurately distinguishing HF patients from individuals with alternative diagnoses. Methods This cross-sectional study was conducted at Cabell Huntington Hospital, St. Mary's Medical Center in Huntington, West Virginia, between 2021 and 2022. The study involved a retrospective chart review of electronic medical records, approved by the institutional review board, encompassing patients aged >18 admitted with Heartlogic-capable devices. The analysis included demographic variables, admission and discharge diagnoses, length of hospital stays, health literacy index, and thoracic impedance. Results Of the initially included 26 patients, 19 met all inclusion criteria. The demographic profile highlighted a predominantly older population with a male preponderance and a notable incidence of congestive heart failure (CHF). Physiological changes, particularly in thoracic impedance and the HeartLogic Index, demonstrated significant alterations. Logistic regression analysis revealed that changes in health literacy index and thoracic impedance significantly contributed to predicting the change in CHF diagnosis. Conclusion This study, conducted in a rural setting, demonstrates the capability of the HeartLogic algorithm in predicting HF events, providing valuable insights into its utility in diverse clinical environments. The findings emphasize the potential of this technology to enhance diagnostic accuracy and improve patient outcomes.Despite inherent limitations, this analysis contributes unique perspectives, particularly in the context of a specific and underexplored rural population in West Virginia.

Influence of different electrode placement patterns on electromagnetic interference generated by Left Ventricular Assist Devices (LVADs) during electrocardiogram performance

Abstract Background Heart failure (HF), with an incidence of approximately 3/1000 person-years, often progresses to advanced stages where symptoms persist despite treatment. In such cases, mechanical circulatory assist devices, particularly left ventricular assist devices (LVADs) in ambulatory patients, enhance survival and quality of life. These LVADs generate electromagnetic interference, resulting in noise artefacts in conventional electrocardiograms (ECGs). The conventional ECG should be configured with a low-pass filter of 150 Hz and a high-pass filter of 0.05 Hz, as recommended by the American Heart Association/American College of Cardiology/Heart Rhythm Society. LVADs, such as the HeartMate 3 (Abbott®), typically operate at a rotational speed of 5000 to 6000 rpm, corresponding to oscillatory frequencies of 83.3 to 100 Hz. Objective To assess the impact of various surface electrode placement strategies and modifications to the low-pass filter on the electromagnetic interference produced by LVADs. Methods We conducted an observational study involving seven patients with HeartMate 3 adjusted to various rotational speeds (refer to Table 1). Three distinct electrode placement schemes (AHA, Mason Likar, and modified Torso) were employed for the frontal plane leads. The horizontal plane leads remained unmodified. Each patient underwent a total of 6 ECGs, corresponding to each of the aforementioned schemes. ECG recordings were performed using a high-pass filter set at 0.05 Hz and a low-pass filter set at 150 Hz. Additionally, a set of ECGs was obtained by modifying the low-pass filter to 40 Hz for further analysis. Results Figure 1 displays ECGs obtained from a male with a HeartMate 3 operating at 4600 rpm or 76.6 Hz. This device employs an algorithm to generate an "artificial pulse" by cyclically accelerating and decelerating the pump speed by 2000 rpm every 2 seconds, resulting in rotational speeds of 2600 rpm and 6600 rpm (43.3 Hz and 110 Hz, respectively). No specific placement scheme demonstrated consistent noise reduction across all cases, likely due to inter-individual variability resulting from factors such as the final position of the LVAD the rpm in each case, and the thoracic impedance of each patient. However, the modification of the low-pass filter to 40 Hz yielded a noteworthy improvement in noise reduction across all cases. In our limited sample, this adjustment did not pose issues for ECG interpretation. Nevertheless, it is essential to acknowledge that excessively low filter settings may not only eliminate noise but also potentially discard clinically relevant high-frequency signals (e.g., pacemaker spikes, large amplitude Rs, QRS notches). Conclusions Individualizing the electrode placement scheme is crucial for minimizing noise generated by LVADs. The adjustment of the low-pass filter to 40 Hz could generally prove beneficial in reducing artifact generation, despite the clinical limitations it may entail.

Separation of ventilation and perfusion of electrical impedance tomography image streams using multi-dimensional ensemble empirical mode decomposition

Objective. In the future, thoracic electrical impedance tomography (EIT) monitoring may include continuous and simultaneous tracking of both breathing and heart activity. However, an effective way to decompose an EIT image stream into physiological processes as ventilation-related and cardiac-related signals is missing.Approach. This study analyses the potential of Multi-dimensional Ensemble Empirical Mode Decomposition by application of the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise and a novel frequency-based combination criterion for detrending, denoising and source separation of EIT image streams, collected from nine healthy male test subjects with similar age and constitution.Main results. In this paper, a novel approach to estimate the lung, the heart and the perfused regions of an EIT image is proposed, which is based on the Root Mean Square Error between the index of maximal respiratory and cardiac variation to their surroundings. The summation of the indexes of the respective regions reveals physiologically meaningful time signals, separated into the physiological bandwidths of ventilation and heart activity at rest. Moreover, the respective regions were compared with the relative thorax movement and photoplethysmogram (PPG) signal. In linear regression analysis and in the Bland–Altman plot, the beat-to-beat time course of both the ventilation-related signal and the cardiac-related signal showed a high similarity with the respective reference signal.Significance. Analysis of the data reveals a fair separation of ventilatory and cardiac activity realizing the aimed source separation, with optional detrending and denoising. For all performed analyses, a feasible correlation of 0.587 to 0.905 was found between the cardiac-related signal and the PPG signal.

Thoracic impedance during national holidays

Abstract Background Several studies have observed increased incidence of myocardial infarctions during Christmas and national holidays. Emotional stress, overindulgence in food and alcohol have been suggested as potential underlying mechanisms. Monitoring of thoracic impedance (TI) by cardiac implantable electronic devices (CIED) has been proposed as a tool for detection of fluid accumulation. We aimed to assess the relationship between TI and national holidays in patients treated with CIED with and without reduced left ventricular ejection fraction (LVEF). Method Consecutive patients with CIED capable of TI monitoring enrolled in the remote monitoring program at a tertiary care hospital in Sweden were screened. Full disclosure remote CIED monitoring database containing daily measurements of TI and device therapy delivery was accessed as the source of information for this retrospective cohort study. Patients were included if they had the monitoring data for at least one holiday (Christmas, New Year or Midsummer) between June 2015 and January 2020. TI during the holiday was compared with baseline values, defined as a mean value of three days preceding Christmas Eve and Midsummer. Clinical characteristics, LVEF, medical treatment and possible contact with healthcare during the holidays or the following week were obtained from medical records. A linear mixed model was used since dependent observations existed. Result In total, 96 patients (82 % men, age 69±10 years, 92 % ICD, 78 % CRT, 72 % with LVEF<40%) were included, which provided data for 255 patient-holidays. TI decreased by mean 1.3 Ohm (95% CI -1.9 to -0.6, p< 0.001) on the Christmas Day, 0.6 Ohm (95 % CI -1.4 to 0.1, p = 0.08) on New Years Day and 1.0 Ohm (95 %CI -1.7 to -0.3, p=0.005) on Midsummer Day. These TI changes were not related to age and did not differ between men and women. Holiday-related TI drop was observed regardless of LVEF: mean decrease on Christmas Day 1,1 vs 1,4 Ohm, New Years Day 0,2 vs 0,4 Ohm and Midsummer Day 1,2 vs 1,0 Ohm for LVEF <40% and >40% respectively. By the third day after a holiday, TI had reached the baseline level. Only one ventricular tachycardia event requiring shock therapy and hospital admission was documented. No other patients were seeking care during the holidays or the days afterwards. Conclusion A significant transient decrease in thoracic impedance was evident during Christmas Day and Midsummer Day in CIED treated patients with reduced and preserved LVEF. These holidays are therefore associated with both decrease in thoracic impedance and incidence of myocardial infarction and it is possible that decrease in thoracic impedance could contribute to the increased incidence of myocardial infarction during holidays.

Left-ventricular-only cardiac resynchronization therapy with electrocardiographic optimization: 100-day follow-up

Abstract Background LV-only (LVo) cardiac resynchronization therapy (CRT) was recognized in 2013 as a non-inferior alternative to bi-ventricular (biV) CRT [1]. In a triple-chamber device it can extend service life, reduce atrial fibrillation risk. A number of LVo systems have been proposed but have not been shown to be superior to biV [2] due to a lack of individualized optimization of the LV atrio-ventricular delay. Purpose An LVo algorithm with an electrocardiographic optimization for each patient along general principles was developed and successfully implanted in a dozen patients with triple-chamber devices. The algorithm has been reported earlier. Since the RV lead is redundant, a dual chamber CRT (dcCRT) version was developed, with just the RA and LV leads. A preliminary series of 8 dcCRT implants were performed with good results. Methods A 2-week training class on LV lead implantation was held in July 2023. Fourteen dcCRT’s were implanted. Inclusion criteria: CRT indications, Left-bundle-branch block, good A-RV conduction, mostly sinus rhythm. 100-day follow-ups were performed on 15 patients (including 2 earlier patients) and reported here. Results In Fig.1 Implant LVEFs (Simpson): 16% to 38%. At the 100-day follow-ups, the LVEFs range from 24% to 62%. 6 (40%) remained below LVEF 35%, 9 (60%) exceeded the 35% threshold, 3 (20%) exceeded 45%, including 2 (13%) with 56% and 62%. Only 3 patients with small 2-3% LVEF improvements. All others were >5%, up to 29%. Since the devices can measure thoracic impedance, Z, 1024 times/hour, with the hourly average combined for a daily average, the 100-day daily Z trends were analyzed. The implant and 100-day Z’s are plotted in Fig.2. Except for the 2 patients whose Z measurements were left off, the universal upward Z trend is an indication of improved LV blood flow in all patients, helping reduced excessive lung fluid. Z changes range from 14 to 34 Ohms. Of the 2 patients in Fig.1 with only 2% LVEF improvements, their Z improvements were meaningful 23 Ohms increases! The Z and LVEF trends indicate that the therapy had a 100% success. Conclusions The 100-day follow-ups of the ECG optimized LVo CRT of 15 patients with dcCRTs show results superior to what have been reported in previous biV studies, thanks to the ECG optimization. This indicates that this may be a superior alternative to biV CRT. While the study was done with dcCRT, it should be applicable to all triple chamber CRT (-P/-D) devices which can support LVo pacing. Unlike other CRT algorithms, if the device supports LVo, it can be applied. It is safe since the programming can be reverted to biV at any time! This opens the possibility for improving the health of current CRT patients and extending the service lives of their devices, in addition to improved de novo results. The dcCRT is no longer viable since bipolar LV leads have been discontinued in favor of quadripolar leads, but the results apply to all CRT systems.Fig 1. LVEF @ implant & 100 dayFig 2. Thoracic Z @implant & 100 day

Regional Pulmonary Ventilation Assessment Method and System Based on Impedance Sensing Information from the Pentapulmonary Lobes

Regional lung ventilation assessment is a critical tool for the early detection of lung diseases and postoperative evaluation. Biosensor-based impedance measurements, known for their non-invasive nature, among other benefits, have garnered significant attention compared to traditional detection methods that utilize pressure sensors. However, solely utilizing overall thoracic impedance fails to accurately capture changes in regional lung air volume. This study introduces an assessment method for lung ventilation that utilizes impedance data from the five lobes, develops a nonlinear model correlating regional impedance with lung air volume, and formulates an approach to identify regional ventilation obstructions based on impedance variations in affected areas. The electrode configuration for the five lung lobes was established through numerical simulations, revealing a power–function nonlinear relationship between regional impedance and air volume changes. An analysis of 389 pulmonary function tests refined the equations for calculating pulmonary function parameters, taking into account individual differences. Validation tests on 30 cases indicated maximum relative errors of 0.82% for FVC and 0.98% for FEV1, all within the 95% confidence intervals. The index for assessing regional ventilation impairment was corroborated by CT scans in 50 critical care cases, with 10 validation trials showing agreement with CT lesion localization results.

Measuring congestion with a non-invasive monitoring device in heart failure and haemodialysis: CONGEST-HF.

We examined the effectiveness of a novel cardiopulmonary management wearable sensor (worn for less than 5 mins) at measuring congestion and correlated the device findings with established clinical measures of congestion. We enrolled three cohorts of patients: (1) patients with heart failure (HF) receiving intravenous diuretics in hospital; (2) patients established on haemodialysis, and (3) HF patients undergoing right heart catheterization (RHC). The primary outcomes in the respective cohorts were a Spearman correlation between (1) change in weight and change in thoracic impedance (TI) (from enrolment, 24 h after admission to discharge) in patients hospitalized for HF; (2) lung ultrasound B-lines and volume removed during dialysis with device measured TI, and (3) pulmonary capillary wedge pressure (PCWP) and sub-acoustic diastolic, third heart sound (S3) in the patients undergoing RHC. A total of 66 patients were enrolled. In HF patients (n = 25), change in weight was correlated with both change in device TI (Spearman correlation [rsp] = -0.64, p = 0.002) and change in device S3 (rsp = -0.53, p = 0.014). In the haemodialysis cohort (n = 21), B-lines and TI were strongly correlated before (rsp = -0.71, p < 0.001) and after (rsp = -0.77, p < 0.001) dialysis. Volume of fluid removed by dialysis was correlated with change in device TI (rsp = 0.49, p = 0.024). In the RHC cohort (n = 20), PCWP measured at one time point and device S3 were not significantly correlated (rsp = 0.230, p = 0.204). There were no device-related adverse events. A non-invasive device was able to detect changes in congestion in patients with HF receiving decongestion therapy and patients having fluid removed at haemodialysis. The cardiopulmonary management device, which measures multiple parameters, is a potentially useful tool to monitor patients with HF to prevent hospitalizations.

Ventilation during cardiopulmonary resuscitation with mechanical chest compressions: How often are two insufflations being given during the 3-second ventilation pauses?

BackgroundMechanical chest compression devices in 30:2 mode provide 3-second pauses to allow for two insufflations. We aimed to determine how often two insufflations are provided in these ventilation pauses, in order to assess if prehospital providers are able to ventilate out-of-hospital cardiac arrest (OHCA) patients successfully during mechanical chest compressions. MethodsData from OHCA cases of the regional ambulance service of Utrecht, The Netherlands, were prospectively collected in the UTrecht studygroup for OPtimal registry of cardIAc arrest database (UTOPIA). Compression pauses and insufflations were visualized on thoracic impedance and waveform capnography signals recorded by manual defibrillators. Ventilation pauses were analyzed for number of insufflations, duration of the subintervals of the ventilation cycles, and ratio of successfully providing two insufflations over the course of the resuscitation. Generalized linear mixed effects models were used to accurately estimate proportions and means. ResultsIn 250 cases, 8473 ventilation pauses were identified, of which 4305 (51%) included two insufflations. When corrected for non-independence of the data across repeated measures within the same subjects with a mixed effects analysis, two insufflations were successfully provided in 45% of ventilation pauses (95% CI: 40–50%). In 19% (95% CI: 16–22%) none were given. ConclusionProviding two insufflations during pauses in mechanical chest compressions is mostly unsuccessful. We recommend developing strategies to improve giving insufflations when using mechanical chest compression devices. Increasing the pause duration might help to improve insufflation success.

Monitoring Adolescent and Young Adult Patients With Cancer via a Smart T-Shirt: Prospective, Single-Cohort, Mixed Methods Feasibility Study (OncoSmartShirt Study).

Wearables that measure vital parameters can be potential tools for monitoring patients at home during cancer treatment. One type of wearable is a smart T-shirt with embedded sensors. Initially, smart T-shirts were designed to aid athletes in their performance analyses. Recently however, researchers have been investigating the use of smart T-shirts as supportive tools in health care. In general, the knowledge on the use of wearables for symptom monitoring during cancer treatment is limited, and consensus and awareness about compliance or adherence are lacking. The aim of this study was to evaluate adherence to and experiences with using a smart T-shirt for the home monitoring of biometric sensor data among adolescent and young adult patients undergoing cancer treatment during a 2-week period. This study was a prospective, single-cohort, mixed methods feasibility study. The inclusion criteria were patients aged 18 to 39 years and those who were receiving treatment at Copenhagen University Hospital - Rigshospitalet, Denmark. Consenting patients were asked to wear the Chronolife smart T-shirt for a period of 2 weeks. The smart T-shirt had multiple sensors and electrodes, which engendered the following six measurements: electrocardiogram (ECG) measurements, thoracic respiration, abdominal respiration, thoracic impedance, physical activity (steps), and skin temperature. The primary end point was adherence, which was defined as a wear time of >8 hours per day. The patient experience was investigated via individual, semistructured telephone interviews and a paper questionnaire. A total of 10 patients were included. The number of days with wear times of >8 hours during the study period (14 d) varied from 0 to 6 (mean 2 d). Further, 3 patients had a mean wear time of >8 hours during each of their days with data registration. The number of days with any data registration ranged from 0 to 10 (mean 6.4 d). The thematic analysis of interviews pointed to the following three main themes: (1) the smart T-shirt is cool but does not fit patients with cancer, (2) the technology limits the use of the smart T-shirt, and (3) the monitoring of data increases the feeling of safety. Results from the questionnaire showed that the patients generally had confidence in the device. Although the primary end point was not reached, the patients' experiences with using the smart T-shirt resulted in the knowledge that patients acknowledged the need for new technologies that improve supportive cancer care. The patients were positive when asked to wear the smart T-shirt. However, technical and practical challenges in using the device resulted in low adherence. Although wearables might have potential for home monitoring, the present technology is immature for clinical use.

Experimental validation of an advanced impedance pneumography for monitoring ventilation volume during programmed cycling exercise

Objective. Impedance pneumography (IP) has provided static assessments of subjects’ breathing patterns in previous studies. Evaluating the feasibility and limitation of ambulatory IP based respiratory monitoring needs further investigation on clinically relevant exercise designs. The aim of this study was to evaluate the capacity of an advanced IP in ambulatory respiratory monitoring, and its predictive value in independent ventilatory capacity quantification during cardiopulmonary exercise testing (CPET). Approach. 35 volunteers were examined with the same calibration methodology and CPET exercise protocol comprising phases of rest, unloaded, incremental load, maximum load, recovery and further-recovery. In 3 or 4 deep breaths of calibration stage, thoracic impedance and criterion spirometric volume were simultaneously recorded to produce phase-specific prior calibration coefficients (CCs). The IP measurement during exercise protocol was converted by prior CCs to volume estimation curve and thus calculate minute ventilation (VE) independent from the spirometry approach. Main results. Across all measurements, the relative error of IP-derived VE (VER) and flowrate-derived VE (VEf) was less than 13.8%. In Bland-Altman plots, the aggregate VE estimation bias was statistically insignificant for all 3 phases with pedaling exercise and the discrepancy between VER and VEf fell within the 95% limits of agreement (95% LoA) for 34 or all subjects in each of all CPET phases. Significance. This work reinforces the independent use of IP as an accurate and robust alternative to flowmeter for applications in cycle ergometry CPET, which could significantly encourage the clinical use of IP and improve the convenience and comfort of CPET.

Hemodynamic and Metabolic Responses to Moderate and Vigorous Cycle Ergometry in Men Who Have Had Transtibial Amputation.

Adults who have had an amputation face barriers to having an active lifestyle which attenuates cardiorespiratory fitness. Prior studies in amputees typically involve treadmill walking or arm ergometry, yet physiological responses to bilateral leg cycling are less understood. This study assessed the hemodynamic and metabolic responses to moderate and vigorous cycle ergometry in men who have had a transtibial amputation (TTA). Five men who had had a unilateral TTA (age = 39 ± 15 yr) and six controls (CONs) without an amputation (age = 31 ± 11 yr) performed two 20 min bouts of cycling differing in intensity. Cardiac output (CO), stroke volume (SV), and oxygen consumption (VO2) were measured during moderate intensity continuous exercise (MICE) and high intensity interval exercise (HIIE) using thoracic impedance and indirect calorimetry. In response to MICE and HIIE, the HR and VO2 levels were similar (p > 0.05) between groups. Stroke volume and CO were higher (p < 0.05) in the CONs, which was attributed to their higher body mass. In men with TTAs, HIIE elicited a peak HR = 88%HRmax and substantial blood lactate accumulation, representing vigorous exercise intensity. No adverse events were exhibited in the men with TTAs. The men with TTAs show similar responses to MICE and HIIE versus the CONs.

Accuracy of Automatic Chest Compression Detection of Different Manufacturers

Research question The detection of single chest compressions (CCs) in defibrillator records is crucial to evaluate CPR quality parameters like longest pause duration.1 Currently, defibrillators detect CCs automatically and provide performance feedback via their proprietary software. While some manufacturers (e.g. Stryker) report the accuracy of their CC detection algorithm and allow to manually revise the automatically detected CCs to improve accuracy, others (e.g. ZOLL) do not offer this option.2 Recent works further suggest that using automatically detected CCs without revision or other open source methods is sufficient to compute quality markers.3,4 We aim to compare the accuracy of the automatic CC detection of two defibrillators. Methodology 131 defibrillator recordings from ZOLL’s X-Series devices with an applied feedback sensor and 70 recordings of Stryker’s LIFEPAK 15 devices were exported. ZOLL detects CC based on accelerometry data from its CC feedback sensor, while Stryker uses the thoracic impedance signal. Each set of recordings was annotated by a single annotator by adding missing CCs and deleting excess CCs, forming a ground truth. The results are reported as median, (10th percentile, 90th percentile) and were tested on statistical significance with a Mann-Whitney U test. Results Per case, the device by ZOLL detects in median 99.6, (97.8,99.9) % of all CCs correctly. 0.4, (0.1,2.3) % are deleted and 0.4, (0.1,2.3) % are added during the annotation process. For Stryker’s LIFEPAK 15 the respective numbers are: correctly detected: 96.7, (81.5,99.2) %, deleted: 1.8, (0.2,10.9) %, added: 3.3, (.8,18.5) %. The difference between the correctly identified CCs is significant (p&lt;0.0001). The distribution of missing and excess CCs for all cases is shown in Figure 1. Interpretation It appears that ZOLL’s CC detection via an accelerometry based feedback sensor is more accurate than Stryker’s method using thoracic impedance. However, Stryker’s accuracy exceeds 95% as well, providing a reasonably reliable basis for CPR quality marker calculations.

Assessing pulmonary function in ALS using electrical impedance tomography

Objective We sought to determine whether thoracic electrical impedance tomography (EIT) could characterize pulmonary function in amyotrophic lateral sclerosis (ALS) patients, including those with facial weakness. Thoracic EIT is a noninvasive, technology in which a multi-electrode belt is placed across the chest, producing real-time impedance imaging of the chest during breathing. Methods We enrolled 32 ALS patients and 32 age- and sex-matched healthy controls (HCs) without underlying lung disease. All participants had EIT measurements performed simultaneously with standard pulmonary function tests (PFTs), including slow and forced vital capacity (SVC and FVC) in upright and supine positions and maximal inspiratory and expiratory pressures (MIPs and MEPs, respectively). Intraclass correlation coefficients (ICCs) were calculated to assess the immediate reproducibility of EIT measurements and Pearson’s correlations were used to explore the relationships between EIT and PFT values. Results Data from 30 ALS patients and 27 HCs were analyzed. Immediate upright SVC reproducibility was very high (ICC 0.98). Correlations were generally strongest between EIT and spirometry measures, with R values ranging from 0.64 to 0.82 (p < 0.001) in the ALS cohort. There were less robust correlations between EIT values and both MIPs and MEPs in the ALS patients, with R values ranging from 0.33 to 0.44. There was no significant difference for patients with and without facial weakness. There were no reported adverse events. Conclusion EIT-based pulmonary measures hold the promise of providing an alternative approach for lung function assessment in ALS patients. Based on these early results, further development and study of this technology are warranted.

Remote monitoring of severe heart failure.

Patients with advanced heart failure, due to the instability of their clinical conditions, need close surveillance to avoid dangerous exacerbations or sudden events. Digital technology can be of great help in this contest, thanks to remote monitoring, made possible with the use of wearable or implantable instruments. The latter are currently generally inserted inside defibrillators or resynchronization systems, or inserted inside the pulmonary circulation for monitoring pulmonary pressure. Parameters such as thoracic impedance, physical activity, heart rate variability, atrial and ventricular arrhythmias, blood pressure, and O2 saturation can be controlled remotely. The data relating to the actual benefit in terms of avoidable events (death and hospitalizations) are not definitive, but certainly from an organizational point of view, the benefit is evident, both on the part of the patient and of the organization of care. The latter, provided in the form of televisits, requires a re-modulation of the system, making use of trained personnel, a well-structured network, and digital technologies (platforms, electronic health records) that are not yet perfectly developed. The evolution of the solutions offered by artificial intelligence guarantees a rapid and progressive refinement of telemedicine in this sector.

A review of infant apnea monitor design

Apnea detection is critical to the management of infant apnea. Effective monitoring and management of apnea using apnea monitors is known to reduce complications and possible fatalities in infants. There is a need to determine the critical design considerations in apnea monitors. This article reviews the design and development of infant apnea monitors. We conducted a targeted literature review from different databases, including PubMed, ScienceDirect, and Google Scholar. We reviewed articles published between January 1995 and February 2023. The search was done using combinations of key terms, namely, “apnea,” “apnea monitors,” and “apnea monitor design.” Articles that met the inclusion criteria were extracted and analyzed. The review investigated common physiological parameters, sensor types, and validation results of apnea monitors. The review revealed important design considerations adopted in the literature as well as the different sensor types and methods of apnea detection. It was found that thoracic impedance pneumography, thermistors, respiratory inductance plethysmography, pneumotachograph, and MEMS accelerometer are the most common sensor types used to design apnea monitors. The review revealed that most apnea monitors were designed to measure multiple physiological parameters. Device validation results varied from one device to another, with sensitivity and specificity metrics ranging between 80% and 96%. With the high burden of infant apnea in developing countries and its associated mortality and morbidity, the design of functional infant apnea monitors has become increasingly important to complement the expensive and complex polysomnography technique. Therefore, we must use appropriate sensors and design approaches for effective detection of infant apnea.

A Wearable Internet of Things Device for Noninvasive Remote Monitoring of Vital Signs Related to Heart Failure

Cardiovascular disease is one of the leading causes of death in the world. Heart failure is a cardiovascular disease in which the heart is unable to pump sufficient blood to fulfill the body’s requirements and can lead to fluid overload. Traditional solutions are not adequate to address the progression of heart failure. Herein, we report a body-mounted wearable sensor to monitor the parameters related to heart failure. These include heart rate, blood oxygen saturation, thoracic impedance, and activity status. The device is compact and wearable and measures the parameters continuously in real time. The device is an Internet of Things (IoT) device connected with a cloud-based database enabling the parameters to be visualized on a mobile application.

Validation of three-dimensional thoracic electrical impedance tomography of horses during normal and increased tidal volumes

Objective. Data from two-plane electrical impedance tomography (EIT) can be reconstructed into various slices of functional lung images, allowing for more complete visualisation and assessment of lung physiology in health and disease. The aim of this study was to confirm the ability of 3D EIT to visualise normal lung anatomy and physiology at rest and during increased ventilation (represented by rebreathing). Approach. Two-plane EIT data, using two electrode planes 20 cm apart, were collected in 20 standing sedate horses at baseline (resting) conditions, and during rebreathing. EIT data were reconstructed into 3D EIT whereby tidal impedance variation (TIV), ventilated area, and right-left and ventral-dorsal centres of ventilation (CoVRL and CoVVD, respectively) were calculated in cranial, middle and caudal slices of lung, from data collected using the two planes of electrodes. Main results. There was a significant interaction of time and slice for TIV (p < 0.0001) with TIV increasing during rebreathing in both caudal and middle slices. The ratio of right to left ventilated area was higher in the cranial slice, in comparison to the caudal slice (p = 0.0002). There were significant effects of time and slice on CoVVD whereby the cranial slice was more ventrally distributed than the caudal slice (p < 0.0009 for the interaction). Significance. The distribution of ventilation in the three slices corresponds with topographical anatomy of the equine lung. This study confirms that 3D EIT can accurately represent lung anatomy and changes in ventilation distribution during rebreathing in standing sedate horses.

A wearable telehealth system for the monitoring of parameters related to heart failure

Heart failure is a cardiovascular disease in which heart fails to pump sufficient blood required by the body. Significant signs of worsening heart failure include decreased thoracic impedance, increased heart rate, irregular electrocardiogram (ECG), and lack of motion activity of the patient. Heart failure can be better managed if monitored continuously and in real-time. The existing solutions for continuous monitoring of these parameters are invasive and hence are not only expensive but can also cause serious health risks. This paper discusses the development of a telehealth system that consists of an Internet of Things including a wearable device connected to a cloud-based database and a mobile application using Wi-Fi. The wearable device is a noninvasive monitor that consists of different sensors embedded with a microcontroller and can be a potential solution for better management of heart failure. It continuously monitors the above-mentioned parameters and sends data to the mobile application using a cloud-based system. The mobile application has separate portals for patients and doctors where doctor can monitor a specific patient enrolled under his profile. The performance of the developed device is validated in 10 healthy individuals.

Effects of exposition to glycol ethers on heart rate recovery, parasympathetic modulation and oxygen diffusion at rest and during exercise

Introduction Daily exposition to ether glycols is common. Caretakers using cleaning products are critically exposed by combining physical activity with exposition to highly concentrated products. Previous animal studies showed hemato-, respiratory and autonomic nervous system toxicity amongst others. Yet, no controlled study explored the combination of an exposition to glycol ethers with physical activity in humans. Methods 30 young healthy participants were exposed a control condition (ambient air) and to one of three vaporized glycol ethers: propylene glycol n-propyl ether (PGPE, 25 ppm, n = 10) or propylene glycol ethyl ether (PGEE, 35 ppm, n = 10) or propylene glycol monomethyl ether (PGME, 35 ppm, n = 10) in a single-blind cross-over design. They performed an orthostatic test (5-min supine, 5-min standing) and a 6-min steady-state exercise at 1.5 W/kg followed by 10-min recovery in PGPE/PGEE conditions. In addition, an incremental exercise to exhaustion followed in PGME condition. Heart rate variability (HRV) was measured throughout the protocol, Heart rate recovery (HRR) was assessed during the 10-min recovery post steady-state exercise. Root-mean-square of the successive differences (RMSSD), power spectrum of the low- (LF) and high-frequency (HF) bands, tau, amplitude and T30 were computed for HRR. Near Infrared spectroscopy (NIRS) and cardiac output (using thoracic impedance) were measured for PGME exposition. PO2, PCO2 and pH were measured regularly via arterialized and venous blood sampling. Results Resting values of supine LF (1,180 ± 851 vs. 2,993 ± 2,259 ms2) and standing RMSSD (32 ± 17 vs. 41 ± 17 ms) increased under PGEE. Supine and standing HR decreased under PGPE (65.5 ± 4.8 vs. 61.3 ± 6.9 and 83.8 ± 7.0 vs. 76.1 ± 10.0 bpm) whereas standing RMSSD (26.6 ± 10.0 vs. 37.0 ± 14.9 ms) and LF (825 ± 474 vs. 2,028 ± 1,471 ms2) increased. Parasympathetic reactivation (e.g., RMSSD, LF and HF) was increased post-exercise under exposition to all three glycol ethers. In addition, amplitude significantly increased when exposed to PGEE. However, unexpectedly, HRR was neither slowed nor speeded. Finally, no differences were observed in any NIRS variables or cardiac output. Accordingly, the modelled muscle oxygen diffusion coefficient was not modified between any solvent conditions. Arterialized blood pH (7.35 ± .06 vs. 7.39 ± .04) and PaCO2 (34.1 ± 5.0 vs. 35.7 ± 4.3 mmHg) increased whilst PaO2 (81.8 ± 9.7 vs. 77.9 ± 10.6 mmHg) decreased. Discussion/Conclusion: The decrease in supine/standing HR associated with a general increase in HRV during recovery likely indicate an increase in parasympathetic modulation, which is compatible with the sedative effects of glycol ethers previously described in animal models. However, HR recovery was not altered. Despite no change in the O2 diffusion coefficient, there was an increase in PaCO2, a decrease in PaO2 and an increase in blood pH, all indicative of potential impaired blood oxygenation during exercise, to be further investigated. To conclude, exposition to different glycol ethers induced an enhanced parasympathetic activation without any changes in HR recovery or O2 diffusion.