Continuous Non-invasive finger cuff CareTaker® comparable to invasive intra-arterial pressure in patients undergoing major intra-abdominal surgery

Haemodynamic monitoring during noncardiac surgery: past, present, and future

During surgery, various haemodynamic variables are monitored and optimised to maintain organ perfusion pressure and oxygen delivery - and to eventually improve outcomes. Important haemodynamic variables that provide an understanding of most pathophysiologic haemodynamic conditions during surgery include heart rate, arterial pressure, central venous pressure, pulse pressure variation/stroke volume variation, stroke volume, and cardiac output. A basic physiologic and pathophysiologic understanding of these haemodynamic variables and the corresponding monitoring methods is essential. We therefore revisit the pathophysiologic rationale for intraoperative monitoring of haemodynamic variables, describe the history, current use, and future technological developments of monitoring methods, and finally briefly summarise the evidence that haemodynamic management can improve patient-centred outcomes.

The interactive effect of intra-beat and inter-beat blood pressure variability on neurodegeneration in older adults

Blood pressure variability (BPV) and arterial stiffness are age-related hemodynamic risk factors for neurodegenerative disease, but it remains unclear whether they exert independent or interactive effects on brain health. When combined with high inter-beat BPV, increased intra-beat BPV indicative of arterial stiffness could convey greater pressure wave fluctuations deeper into the cerebrovasculature, exacerbating neurodegeneration. This interactive effect was studied in older adults using multiple markers of neurodegeneration, including medial temporal lobe (MTL) volume, plasma neurofilament light (NfL) and glial fibrillary acidic protein (GFAP). Older adults (N=105) without major neurological or systemic disease were recruited and underwent brain MRI and continuous BP monitoring to quantify inter-beat BPV through systolic average real variability (ARV) and intra-beat variability through arterial stiffness index (ASI). Plasma NfL and GFAP were assessed. The interactive effect of ARV and ASI on MTL atrophy, plasma NfL, and GFAP was studied using hierarchical linear regression. Voxel-based morphometry (VBM) was used to confirm region-of-interest analysis findings. The interaction between higher ARV and higher ASI was significantly associated with left-sided MTL atrophy in both the region-of-interest and false discovery rate-corrected VBM analysis. The interactive effect was also significantly associated with increased plasma NfL, but not GFAP. The interaction between higher ARV and higher ASI is independently associated with increased neurodegenerative markers, including MTL atrophy and plasma NfL, in independently living older adults. Findings could suggest the increased risk for neurodegeneration associated with higher inter-beat BPV may be compounded by increased intra-beat variability due to arterial stiffness.

Reliability of beat-to-beat blood pressure variability in older adults

Blood pressure variability (BPV) is emerging as an important risk factor across numerous disease states, including cerebrovascular and neurodegenerative disease in older adults. However, there is no current consensus regarding specific use cases for the numerous available BPV metrics. There is also little published data supporting the ability to reliably measure BPV across metrics in older adults. BPV metrics were derived from continuous beat-to-beat blood pressure monitoring data. Two sequential 7-minute waveforms were analyzed. Absolute and relative reliability testing was performed. Differences between antihypertensive medication users and non-users on BPV metric reliability was also assessed. All sequence and dispersion based BPV metrics displayed good test-retest reliability. A measure of BP instability displayed only moderate reliability. Systolic and diastolic average real variability displayed the highest levels of reliability at ICC= .87 and .82 respectively. Additionally, systolic average real variability was the most reliable metric in both the antihypertensive use group, and the no antihypertensive use group. Beat-to-beat dispersion and sequence-based metrics of BPV can be reliably obtained from older adults using noninvasive continuous blood pressure monitoring. Average real variability may be the most reliable and specific beat-to-beat blood pressure variability metric due to its decreased susceptibility to outliers and low frequency blood pressure oscillations.

A Direct Assessment of Noninvasive Continuous Blood Pressure Monitoring in the Emergency Department and Intensive Care Unit

INTRODUCTION

Noninvasive continuous blood pressure monitoring has the potential to improve patient treatment in the hospital setting. Such noninvasive devices can be applied earlier in the treatment process to empower nurses and clinicians to react more quickly to patient deterioration with the added benefit of eliminating the risks associated with invasive monitoring. However, emerging technologies must be capable of reproducing current clinical measures for medical decision making.

METHODS

This study aimed to determine the usability and willingness of nurses to implement a noninvasive continuous blood pressure monitoring device. The secondary aim directly compared the systolic blood pressure, diastolic blood pressure, and mean arterial pressure values recorded by the device (VitalStream; CareTaker Medical LLC, Charlottesville, VA) with the "gold standard" brachial cuff and arterial line measures recorded in the emergency department and intensive care unit settings.

RESULTS

VitalStream was similarly received by nurses in the emergency department and intensive care setting, but ultimately had greater promotion from emergency nurses. Despite some statistical similarity between measurement methodologies, all direct comparisons were found to not meet the Association for the Advancement of Medical Instrumentation 2008 and Association for the Advancement of Medical Instrumentation / European Society of Hypertension / International Organization for Standardization 2019 consensus statement criteria for acceptable blood pressure measure differences between the VitalStream and "gold standard" clinical measures. In all instances, the standard deviation of the Bland-Altman bias exceeded 8 mm Hg with less than 85% of paired differences falling within 10 mm Hg of the "gold standard."

DISCUSSION

Taken together, the tested device requires additional postprocessing for medical decision making in trauma or emergent care.

Short-term blood pressure variability and brain functional network connectivity in older adults

Background

Blood pressure variability is increasingly linked with cerebrovascular disease and Alzheimer's disease, independent of mean blood pressure levels. Elevated blood pressure variability is also associated with attenuated cerebrovascular reactivity, which may have implications for functional hyperemia underpinning brain network connectivity. It remains unclear whether blood pressure variability is related to functional network connectivity. We examined relationships between beat-to-beat blood pressure variability and functional connectivity in brain networks vulnerable to aging and Alzheimer's disease.

Methods

53 community-dwelling older adults (mean [SD] age = 69.9 [7.5] years, 62.3% female) without history of dementia or clinical stroke underwent continuous blood pressure monitoring and resting state fMRI scan. Blood pressure variability was calculated as variability independent of mean. Functional connectivity was determined by resting state fMRI for several brain networks: default, salience, dorsal attention, fronto-parietal, and language. Multiple linear regression examined relationships between short-term blood pressure variability and functional network connectivity.

Results

Elevated short-term blood pressure variability was associated with lower functional connectivity in the default network (systolic: standardized ß = -0.30 [95% CI -0.59, -0.01], p = .04). There were no significant associations between blood pressure variability and connectivity in other functional networks or between mean blood pressure and functional connectivity in any network.

Discussion

Older adults with elevated short-term blood pressure variability exhibit lower resting state functional connectivity in the default network. Findings support the role of blood pressure variability in neurovascular dysfunction and Alzheimer's disease. Blood pressure variability may represent an understudied early vascular risk factor for neurovascular dysfunction relevant to Alzheimer's disease, with potential therapeutic implications.

Agreement between cardiac output estimation with a wireless, wearable pulse decomposition analysis device and continuous thermodilution in post cardiac surgery intensive care unit patients

PURPOSE

Pulse Decomposition Analysis (PDA) uses integration of the systolic area of a distally transmitted aortic pulse as well as arterial stiffness estimates to compute cardiac output. We sought to assess agreement of cardiac output (CO) estimation between continuous pulmonary artery catheter (PAC) guided thermodilution (CO-CCO) and a wireless, wearable noninvasive device, (Vitalstream, Caretaker Medical, Charlottesville, VA), that utilizes the Pulse Decomposition Analysis (CO-PDA) method in postoperative cardiac surgery patients in the intensive care unit.

METHODS

CO-CCO measurements were compared with post processed CO-PDA measurements in prospectively enrolled adult cardiac surgical intensive care unit patients. Uncalibrated CO-PDA values were compared for accuracy with CO-CCO via a Bland-Altman analysis considering repeated measurements and a concordance analysis with a 10% exclusion zone.

RESULTS

259.7 h of monitoring data from 41 patients matching 15,583 data points were analyzed. Mean CO-CCO was 5.55 L/min, while mean values for the CO-PDA were 5.73 L/min (mean of differences +- SD 0.79 ± 1.11 L/min; limits of agreement - 1.43 to 3.01 L/min), with a percentage error of 37.5%. CO-CCO correlation with CO-PDA was moderate (0.54) and concordance was 0.83.

CONCLUSION

Compared with the CO-CCO Swan-Ganz, cardiac output measurements obtained using the CO-PDA were not interchangeable when using a 30% threshold. These preliminary results were within the 45% limits for minimally invasive devices, and pending further robust trials, the CO-PDA offers a noninvasive, wireless solution to complement and extend hemodynamic monitoring within and outside the ICU.

Schrödinger spectrum based continuous cuff-less blood pressure estimation using clinically relevant features from PPG signal and its second derivative

The presented study estimates cuff-less blood pressure (BP) from photoplethysmography (PPG) signals using multiple machine-learning (ML) models and the semi-classical signal analysis (SCSA) technique. The study proposes a novel signal reconstruction algorithm, which optimizes the semi-classical constant of the SCSA approach and eliminates the trade-off between complexity and accuracy during signal reconstruction. It predicts BP values using regression algorithms by processing reconstructed PPG signals' spectral features, extracting clinically relevant PPG and its second derivative's (SDPPG) morphological features. The developed method was assessed using a virtual in-silico dataset with more than 4000 subjects and the Multi-Parameter Intelligent Monitoring in Intensive Care Units (MIMIC-II) dataset. Results showed that the method attained a mean absolute error (MAE) of 5.37 and 2.96 mmHg for systolic and diastolic BP, respectively, using the CatBoost algorithm. This approach met the Association for the Advancement of Medical Instrumentation's standard and achieved Grade A for all BP categories in the British Hypertension Society protocol. The proposed framework performs well even when applied to a combined clinically relevant database originating from MIMIC-III and the Queensland dataset. The proposed method's performance is further evaluated in a non-clinical setting with noisy and deformed PPG signals to validate the efficacy of the SCSA method. The noise stress tests further showed that the algorithm maintained its key feature detection, signal reconstruction capability, and estimation accuracy up to a 10 dB SNR ratio. The proposed cuff-less BP estimation technique has the potential to perform well in mobile healthcare devices due to its straightforward implementation approach.

The Promise and Illusion of Continuous, Cuffless Blood Pressure Monitoring

PURPOSE OF REVIEW

Blood pressure (BP) fluctuations outside of clinic are increasingly recognized for their role in the development of cardiovascular disease, syncope, and premature death and as a promising target for tailored hypertension treatment. However, current cuff-based BP devices, including home and ambulatory devices, are unable to capture the breadth of BP variability across human activities, experiences, and contexts.

RECENT FINDINGS

Cuffless, wearable BP devices offer the promise of beat-to-beat, continuous, noninvasive measurement of BP during both awake and sleep periods with minimal patient inconvenience. Importantly, cuffless BP devices can characterize BP variability, allowing for the identification of patient-specific triggers of BP surges in the home environment. Unfortunately, the pace of evidence, regulation, and validation testing has lagged behind the pace of innovation and direct consumer marketing. We provide an overview of the available technologies and devices for cuffless BP monitoring, considerations for the calibration and validation of these devices, and the promise and pitfalls of the cuffless BP paradigm.

Estimating Blood Pressure during Exercise with a Cuffless Sphygmomanometer

Accurately measuring blood pressure (BP) is essential for maintaining physiological health, which is commonly achieved using cuff-based sphygmomanometers. Several attempts have been made to develop cuffless sphygmomanometers. To increase their accuracy and long-term variability, machine learning methods can be applied for analyzing photoplethysmogram (PPG) signals. Here, we propose a method to estimate the BP during exercise using a cuffless device. The BP estimation process involved preprocessing signals, feature extraction, and machine learning techniques. To ensure the reliability of the signals extracted from the PPG, we employed the skewness signal quality index and the RReliefF algorithm for signal selection. Thereafter, the BP was estimated using the long short-term memory (LSTM)-based neural network. Seventeen young adult males participated in the experiments, undergoing a structured protocol composed of rest, exercise, and recovery for 20 min. Compared to the BP measured using a non-invasive voltage clamp-type continuous sphygmomanometer, that estimated by the proposed method exhibited a mean error of 0.32 ± 7.76 mmHg, which is equivalent to the accuracy of a cuff-based sphygmomanometer per regulatory standards. By enhancing patient comfort and improving healthcare outcomes, the proposed approach can revolutionize BP monitoring in various settings, including clinical, home, and sports environments.

Short-term blood pressure variability is inversely related to regional amplitude of low frequency fluctuations in older and younger adults

Blood pressure variability (BPV), independent of mean blood pressure levels, is associated with cerebrovascular disease burden on MRI and postmortem evaluation. However, less is known about relationships with markers of cerebrovascular dysfunction, such as diminished spontaneous brain activity as measured by the amplitude of low frequency fluctuations (ALFF), especially in brain regions with vascular and neuronal vulnerability in aging. We investigated the relationship between short-term BPV and concurrent regional ALFF from resting state fMRI in a sample of community-dwelling older adults (n = 44) and healthy younger adults (n = 49). In older adults, elevated systolic BPV was associated with lower ALFF in widespread medial temporal regions and the anterior cingulate cortex. Higher systolic BPV in younger adults was also related to lower ALFF in the medial temporal lobe, albeit in fewer subregions, and the amygdala. There were no significant associations between systolic BPV and ALFF across the right/left whole brain or in the insular cortex in either group. Findings suggest a possible regional vulnerability to cerebrovascular dysfunction and short-term fluctuations in blood pressure. BPV may be an understudied risk factor for cerebrovascular changes in aging.

Patent landscape review of non-invasive medical sensors for continuous monitoring of blood pressure and their validation in critical care practice

Objectives

Continuous non-invasive monitoring of blood pressure is one of the main factors in ensuring the safety of the patient's condition in anesthesiology, intensive care, surgery, and other areas of medicine. The purpose of this work was to analyze the current patent situation and identify directions and trends in the application of non-invasive medical sensors for continuous blood pressure monitoring, with a focus on clinical experience in critical care and validation thereof.

Materials and methods

The research results reflect data collected up to September 30, 2022. Patent databases, Google Scholar, the Lens database, Pubmed, Scopus databases were used to search for patent and clinical information.

Results

An analysis of the patent landscape indicates a significant increase in interest in the development of non-invasive devices for continuous blood pressure monitoring and their implementation in medical practice, especially in the last 10 years. The key players in the intellectual property market are the following companies: Cnsystems Medizintechnik; Sotera Wireless INC; Tensys Medical INC; Healthstats Int Pte LTD; Edwards Lifesciences Corp, among others. Systematization of data from validation and clinical studies in critical care practice on patients with various pathological conditions and ages, including children and newborns, revealed that a number of non-invasive medical sensor technologies are quite accurate and comparable to the "gold standard" continuous invasive blood pressure monitoring. They are approved by the FDA for medical applications and certified according to ISO 81060-2, ISO 81060-3, and ISO/TS 81060-5. Unregistered and uncertified medical sensors require further clinical trials.

Conclusion

Non-invasive medical sensors for continuous blood pressure monitoring do not replace, but complement, existing methods of regular blood pressure measurement, and it is expected to see more of these technologies broadly implemented in the practice in the near future.

A Review of Skin-Wearable Sensors for Non-Invasive Health Monitoring Applications

The early detection of fatal diseases is crucial for medical diagnostics and treatment, both of which benefit the individual and society. Portable devices, such as thermometers and blood pressure monitors, and large instruments, such as computed tomography (CT) and X-ray scanners, have already been implemented to collect health-related information. However, collecting health information using conventional medical equipment at home or in a hospital can be inefficient and can potentially affect the timeliness of treatment. Therefore, on-time vital signal collection via healthcare monitoring has received increasing attention. As the largest organ of the human body, skin delivers significant signals reflecting our health condition; thus, receiving vital signals directly from the skin offers the opportunity for accessible and versatile non-invasive monitoring. In particular, emerging flexible and stretchable electronics demonstrate the capability of skin-like devices for on-time and continuous long-term health monitoring. Compared to traditional electronic devices, this type of device has better mechanical properties, such as skin conformal attachment, and maintains compatible detectability. This review divides the health information that can be obtained from skin using the sensor aspect's input energy forms into five categories: thermoelectrical signals, neural electrical signals, photoelectrical signals, electrochemical signals, and mechanical pressure signals. We then summarize current skin-wearable health monitoring devices and provide outlooks on future development.

Upper-Arm Photoplethysmographic Sensor with One-Time Calibration for Long-Term Blood Pressure Monitoring

Wearable cuffless photoplethysmographic blood pressure monitors have garnered widespread attention in recent years; however, the long-term performance values of these devices are questionable. Most cuffless blood pressure monitors require initial baseline calibration and regular recalibrations with a cuffed blood pressure monitor to ensure accurate blood pressure estimation, and their estimation accuracy may vary over time if left uncalibrated. Therefore, this study assessed the accuracy and long-term performance of an upper-arm, cuffless photoplethysmographic blood pressure monitor according to the ISO 81060-2 standard. This device was based on a nonlinear machine-learning model architecture with a fine-tuning optimized method. The blood pressure measurement protocol followed a validation procedure according to the standard, with an additional four weekly blood pressure measurements over a 1-month period, to assess the long-term performance values of the upper-arm, cuffless photoplethysmographic blood pressure monitor. The results showed that the photoplethysmographic signals obtained from the upper arm had better qualities when compared with those measured from the wrist. When compared with the cuffed blood pressure monitor, the means ± standard deviations of the difference in BP at week 1 (baseline) were -1.36 ± 7.24 and -2.11 ± 5.71 mmHg for systolic and diastolic blood pressure, respectively, which met the first criterion of ≤5 ± ≤8.0 mmHg and met the second criterion of a systolic blood pressure ≤ 6.89 mmHg and a diastolic blood pressure ≤ 6.84 mmHg. The differences in the uncalibrated blood pressure values between the test and reference blood pressure monitors measured from week 2 to week 5 remained stable and met both criteria 1 and 2 of the ISO 81060-2 standard. The upper-arm, cuffless photoplethysmographic blood pressure monitor in this study generated high-quality photoplethysmographic signals with satisfactory accuracy at both initial calibration and 1-month follow-ups. This device could be a convenient and practical tool to continuously measure blood pressure over long periods of time.

A novel smartphone app for blood pressure measurement: a proof-of-concept study against an arterial catheter

Smartphones may provide a highly available access to simplified hypertension screening in environments with limited health care resources. Most studies involving smartphone blood pressure (BP) apps have focused on validation in static conditions without taking into account intraindividual BP variations. We report here the first experimental evidence of smartphone-derived BP estimation compared to an arterial catheter in a highly dynamic context such as induction of general anesthesia. We tested a smartphone app (OptiBP) on 121 patients requiring general anesthesia and invasive BP monitoring. For each patient, ten 1-min segments aligned in time with ten smartphone recordings were extracted from the continuous invasive BP. A total of 1152 recordings from 119 patients were analyzed. After exclusion of 2 subjects and rejection of 565 recordings due to BP estimation not generated by the app, we retained 565 recordings from 109 patients (acceptance rate 51.1%). Concordance rate (CR) and angular CR demonstrated values of more than 90% for systolic (SBP), diastolic (DBP) and mean (MBP) BP. Error grid analysis showed that 98% of measurement pairs were in no- or low-risk zones for SBP and MBP, of which more than 89% in the no-risk zone. Evaluation of accuracy and precision [bias ± standard deviation (95% limits of agreement)] between the app and the invasive BP was 0.0 ± 7.5 mmHg [- 14.9, 14.8], 0.1 ± 2.9 mmHg [- 5.5, 5.7], and 0.1 ± 4.2 mmHg [- 8.3, 8.4] for SBP, DBP and MBP respectively. To the best of our knowledge, this is the first time a smartphone app was compared to an invasive BP reference. Its trending ability was investigated in highly dynamic conditions, demonstrating high concordance and accuracy. Our study could lead the way for mobile devices to leverage the measurement of BP and management of hypertension.

Perioperative changes in fluid distribution and haemodynamics in acute high-risk abdominal surgery

BACKGROUND

Understanding the pathophysiology of fluid distribution in acute high-risk abdominal (AHA) surgery is essential in optimizing fluid management. There is currently no data on the time course and haemodynamic implications of fluid distribution in the perioperative period and the differences between the surgical pathologies.

METHODS

Seventy-three patients undergoing surgery for intestinal obstruction, perforated viscus, and anastomotic leakage within a well-defined perioperative regime, including intraoperative goal-directed therapy, were included in this prospective, observational study. From 0 to 120 h, we measured body fluid volumes and hydration status by bioimpedance spectroscopy (BIA), fluid balance (input vs. output), preload dependency defined as a > 10% increase in stroke volume after preoperative fluid challenge, and post-operatively evaluated by passive leg raise.

RESULTS

We observed a progressive increase in fluid balance and extracellular volume throughout the study, irrespective of surgical diagnosis. BIA measured variables indicated post-operative overhydration in 36% of the patients, increasing to 50% on the 5th post-operative day, coinciding with a progressive increase of preload dependency, from 12% immediately post-operatively to 58% on the 5th post-operative day and irrespective of surgical diagnosis. Patients with overhydration were less haemodynamically stable than those with normo- or dehydration.

CONCLUSION

Despite increased fluid balance and extracellular volumes, preload dependency increased progressively during the post-operative period. Our observations indicate a post-operative physiological incoherence between changes in the extracellular volume compartment and inadequate physiological preload control in patients undergoing AHA surgery. Considering the increasing overhydration during the observational period, our findings show that an indiscriminate correction of preload dependency with intravenous fluid bolus could lead to overhydration. Trial registration clinicaltrials.gov. (NCT03997721), Registered 23 May 2019, first participant enrolled 01 June 2019.

Long-term stability of over-the-counter cuffless blood pressure monitors: a proposal

Blood pressure is an important cardiovascular parameter. Currently, the cuff-based sphygmomanometer is a popular, reliable, measurement method, but blood pressure monitors without cuffs have become popular and are now available without a prescription. Blood pressure monitors must be approved by regulatory authorities. Current cuffless blood pressure (CL-BP) monitors are not suitable for at-home management and prevention of hypertension. This paper proposes simple criteria for over-the-counter CL-BP monitoring. First, the history of the sphygmomanometer and current standard blood pressure protocol are reviewed. The main components of CL-BP monitoring are accuracy during the resting condition, accuracy during dynamic blood pressure changes, and long-term stability. In this proposal we recommend intermittent measurement to ensure that active measurement accuracy mirrors resting condition accuracy. A new experimental protocol is proposed to maintain long-term stability. A medically approved automated sphygmomanometer was used as the standard device in this study. The long-term accuracy of the test device is based on the definition of propagation error, i.e., for an oscillometric automated sphygmomanometer (5 ± 8 mmHg) ± the error for the test device static accuracy (-0.12 ± 5.49 mmHg for systolic blood pressure and - 1.17 ± 5.06 mmHg for diastolic blood pressure). Thus, the long-term stabilities were - 3.38 ± 7.1 mmHg and - 1.38 ± 5.4 mmHg, which satisfied propagation error. Further research and discussion are necessary to create standards for use by manufacturers; such standards should be readily evaluated and ensure high-quality evidence.

Supplementary information

The online version contains supplementary material available at 10.1007/s12553-023-00726-6.

The consistency of invasive and non-invasive arterial blood pressure for the assessment of dynamic cerebral autoregulation in NICU patients

Background

Studies of the clinical application of dynamic cerebral autoregulation show considerable variations, and differences in blood pressure devices may be one of the reasons for this variation. Few studies have examined the consistency of invasive and non-invasive arterial blood pressure for evaluating cerebral autoregulation. We attempted to investigate the agreement between invasive and non-invasive blood pressure methods in the assessment of dynamic cerebral autoregulation with transfer function analysis.

Methods

Continuous cerebral blood flow velocity and continuous invasive and non-invasive arterial blood pressure were simultaneously recorded for 15 min. Transfer function analysis was applied to derive the phase shift, gain and coherence function at all frequency bands from the first 5, 10, and 15 min of the 15-min recordings. The consistency was assessed with Bland-Altman analysis and intraclass correlation coefficient.

Results

The consistency of invasive and noninvasive blood pressure methods for the assessment of dynamic cerebral autoregulation was poor at 5 min, slightly improved at 10 min, and good at 15 min. The values of the phase shift at the low-frequency band measured by the non-invasive device were higher than those measured with invasive equipment. The coherence function values measured by the invasive technique were higher than the values derived from the non-invasive method.

Conclusion

Both invasive and non-invasive arterial blood pressure methods have good agreement in evaluating dynamic cerebral autoregulation when the recording duration reaches 15 min. The phase shift values measured with non-invasive techniques are higher than those measured with invasive devices. We recommend selecting the most appropriate blood pressure device to measure cerebral autoregulation based on the disease, purpose, and design.

A pilot randomized controlled trial of supervised, at-home, self-administered transcutaneous auricular vagus nerve stimulation (taVNS) to manage long COVID symptoms

Background

Although the coronavirus disease 19 (COVID-19) pandemic has now impacted the world for over two years, the persistent secondary neuropsychiatric effects are still not fully understood. These “long COVID” symptoms, also referred to as post-acute sequelae of SARS-CoV-2 infection (PASC), can persist for months after infection without any effective treatments. Long COVID involves a complex heterogenous symptomology and can lead to disability and limit work. Long COVID symptoms may be due to sustained inflammatory responses and prolonged immune response after infection. Interestingly, vagus nerve stimulation (VNS) may have anti-inflammatory effects, however, until recently, VNS could not be self-administered, at-home, noninvasively.

Methods

We created a double-blind, noninvasive transcutaneous auricular VNS (taVNS) system that can be self-administered at home with simultaneous remote monitoring of physiological biomarkers and video supervision by study staff. Subsequently, we carried out a pilot (n = 13) randomized, sham-controlled, trial with this system for four weeks to treat nine predefined long covid symptoms (anxiety, depression, vertigo, anosmia, ageusia, headaches, fatigue, irritability, brain fog). No in-person patient contact was needed, with informed consent, trainings, ratings, and all procedures being conducted remotely during the pandemic (2020–2021) and equipment being shipped to individuals’ homes. This trial was registered on ClinicalTrials.gov under the identifier: NCT04638673 registered November 20, 2020.

Results

Four-weeks of at-home self-administered taVNS (two, one-hour sessions daily, delivered at suprathreshold intensities) was feasible and safe. Although our trial was not powered to determine efficacy as an intervention in a heterogenous population, the trends in the data suggest taVNS may have a mild to moderate effect in reducing mental fatigue symptoms in a subset of individuals.

Conclusions

This innovative study demonstrates the safety and feasibility of supervised self-administered taVNS under a fully contactless protocol and suggests that future studies can safely investigate this novel form of brain stimulation at-home for a variety of neuropsychiatric and motor recovery applications.

A pilot randomized controlled trial of supervised, at-home, self-administered transcutaneous auricular vagus nerve stimulation (taVNS) to manage long COVID symptoms

Background Although the coronavirus disease 19 (COVID-19) pandemic has now impacted the world for over two years, the persistent secondary neuropsychiatric effects are still not fully understood. These "long COVID" symptoms, also referred to as post-acute sequelae of SARS-CoV-2 infection (PASC), can persist for months after infection without any effective treatments. Long COVID involves a complex heterogenous symptomology and can lead to disability and limit work. Long COVID symptoms may be due to sustained inflammatory responses and prolonged immune response after infection. Interestingly, vagus nerve stimulation (VNS) may have anti-inflammatory effects, however, until recently, VNS could not be self-administered, at-home, noninvasively. Methods We created a double-blind, noninvasive transcutaneous auricular VNS (taVNS) system that can be self-administered at home with simultaneous remote monitoring of physiological biomarkers and video supervision by study staff. Subsequently, we carried out a pilot (n = 13) randomized, sham-controlled, trial with this system for four weeks to treat nine predefined long covid symptoms (anxiety, depression, vertigo, anosmia, ageusia, headaches, fatigue, irritability, brain fog). No in-person patient contact was needed, with informed consent, trainings, ratings, and all procedures being conducted remotely during the pandemic (2020-2021) and equipment being shipped to individuals' homes. This trial was registered onClinicalTrials.gov under the identifier: NCT04638673. Results Four-weeks of at-home self-administered taVNS (two, one-hour sessions daily, delivered at suprathreshold intensities) was feasible and safe. Although our trial was not powered to determine efficacy as an intervention in a heterogenous population, the trends in the data suggest taVNS may have a mild to moderate effect in reducing mental fatigue symptoms in a subset of individuals. This innovative study demonstrates the safety and feasibility of supervised self-administered taVNS under a fully contactless protocol and suggests that future studies can safely investigate this novel form of brain stimulation at-home for a variety of neuropsychiatric and motor recovery applications.

D-dimer in Marfan syndrome: effect of obstructive sleep apnea induced blood pressure surges

Aortic dissection and rupture are the major causes of premature death in persons with Marfan syndrome (MFS), a rare genetic disorder featuring cardiovascular, skeletal, and ocular impairments. We and others have found that obstructive sleep apnea (OSA) confers significant vascular stress in this population and may accelerate aortic disease progression. We hypothesized that D-dimer, a diagnostic biomarker for several types of vascular injury that is also elevated in persons with MFS with aortic enlargement, may be sensitive to cardiovascular stresses caused by OSA. To test this concept, we recruited 16 persons with MFS without aortic dissection and randomized them to two nights of polysomnography, without (baseline) and with OSA treatment: continuous positive airway pressure (CPAP). In addition to scoring OSA by the apnea-hypopnea index (AHI), beat-by-beat systolic BP (SBP) and pulse-pressure (PP) fluctuations were quantified. Morning blood samples were also assayed for D-dimer levels. In this cohort (male:female, 10:6; age, 36 ± 13 yr; aortic diameter, 4 ± 1 cm), CPAP eliminated OSA (AHI: 20 ± 17 vs. 3 ± 2 events/h, P = 0.001) and decreased fluctuations in SBP (13 ± 4 vs. 9 ± 3 mmHg, P = 0.011) and PP (7 ± 2 vs. 5 ± 2 mmHg, P = 0.013). CPAP also reduced D-dimer levels from 1,108 ± 656 to 882 ± 532 ng/mL (P = 0.023). Linear regression revealed a positive association between the maximum PP during OSA and D-dimer in both the unadjusted (r = 0.523, P = 0.038) and a model adjusted for contemporaneous aortic root diameter (r = 0.733, P = 0.028). Our study revealed that overnight CPAP reduces D-dimer levels commensurate with the elimination of OSA and concomitant hemodynamic fluctuations. Morning D-dimer measurements together with OSA screening might serve as predictors of vascular injury in MFS.NEW & NOTEWORTHY What is New? Surges in blood pressure caused by obstructive sleep apnea during sleep increase vascular stress and D-dimer levels in Marfan syndrome. Elevations in D-dimer can be lowered with CPAP. What is Noteworthy? D-dimer levels might serve as a marker for determining the significance of obstructive sleep apnea in persons with Marfan syndrome. D-dimer or obstructive sleep apnea screening is a potential method to identify persons with Marfan syndrome at risk for adverse cardiovascular events.

Elucidation of obstructive sleep apnoea related blood pressure surge using a novel continuous beat-to-beat blood pressure monitoring system

BACKGROUND

Obstructive sleep apnoea (OSA) episode related blood pressure (BP) surge may mediate the association of OSA with cardiovascular disease. However, BP is not measured during a clinical sleep study.

METHOD

We tested the feasibility of incorporating the Caretaker physiological monitor, which utilizes a novel continuous beat-to-beat (b-b) BP monitoring technology, into polysomnography (PSG) and aimed to characterize BP surges related to obstructive respiratory events. B-b BP was concurrently collected and merged with PSG data on a posthoc basis. We compared BP surge between mean respiratory (apnoea, hypopnea and desaturation-alone events) and nonrespiratory events (spontaneous or leg movement-related arousals). We examined the association of the degree of oxygen desaturation with BP surge in a given respiratory event combining all events. A total of 17 consecutive patients (12 men, mean 52 years old, nine diagnostic and eight split-night PSGs) undergoing clinically indicated PSG were included after excluding one patient with poor signal quality due to excessive movement.

RESULTS

Caretaker was well tolerated. Mean respiratory BP surge ranged from 5 to 19 mmHg [Median (IQR) = 13.9 (9.5--16.2)]. Mean BP surge between the respiratory and nonrespiratory events was similar [13.8 (4.5) vs. 14.9 (5.3) mmHg, P = 0.13]. Accounting for the count distribution of desaturation/BP surge data pair events, there was a linear correlation between the degree of oxygen desaturation and BP surge (R = 0.57, P < 0.001). In eight patients undergoing split-night sleep studies, the number of BP surge events (≥10 mmHg/h) decreased during continuous positive airway pressure in all but one patient.

CONCLUSION

We demonstrated highly variable OSA-related BP surge patterns using the Caretaker's b-b BP monitoring technology that has the potential to be integrated into sleep studies.

Assessment of pleural pressure during sleep in Marfan syndrome

STUDY OBJECTIVES

Patients with Marfan syndrome (MFS) have a high risk for aortic aneurysms. They are also susceptible to sleep-disordered breathing that may expose them to highly negative intrathoracic pressures known to increase aortic transmural pressure which may accelerate aortic dilatation. Our objective was to quantify overnight intrathoracic pressure changes during sleep in snoring patients with MFS, and the therapeutic effect of continuous positive airway pressure (CPAP).

METHODS

We used a questionnaire to identify self-reported snoring patients with MFS. In these patients, we monitored intrathoracic pressure using esophageal pressure (Pes) during overnight baseline and CPAP sleep studies. We defined a peak inspiratory Pes (Pes_peak-insp) < - 5 cmH₂O as greater than normal, and examined the distribution of Pes_peak-insp during baseline and CPAP studies.

RESULTS

In our sample of 23 MFS snorers, we found that 70% of sleep breaths exhibited Pes_peak-insp < -5 cmH₂O, with apneas/hypopneas accounting for only 12%, suggesting prevalent stable flow-limited breathing and snoring. In a subset (n=12) with Pes monitoring during CPAP night, CPAP lowered the mean proportion of breaths with Pes_peak-insp < -5 cmH₂O from 83.7±14.9% to 3.6±3.0% (p<0.001). In addition, contemporaneous aortic root diameter was associated with the mean Pes_peak-insp during IFL and apneas/hypopneas (β= -0.05, r=0.675, p=0.033).

CONCLUSIONS

The sleep state in MFS revealed prolonged exposure to exaggerated negative inspiratory Pes, which was reversible with CPAP. Since negative intrathoracic pressure can contribute to thoracic aortic stress and aortic dilatation, snoring may be a reversible risk factor for progression of aortic pathology in MFS.

Tracking of the beat-to-beat blood pressure changes by the Caretaker physiological monitor against invasive central aortic measurement

OBJECTIVE

There is an unmet need for noninvasive continuous blood pressure (BP) monitoring technologies in various clinical settings. Continuous and noninvasive central aortic BP monitoring is technically not feasible currently, but if realized, would provide more accurate and real-time global hemodynamic information than any form of peripheral arterial BP monitoring in an acute care setting. As part of our efforts to develop such, herein we examined the tracking correlation between noninvasively-derived peripheral arterial BP by Caretaker device against invasively measured central aortic BP.

METHODS

Beat-to-beat BP by Caretaker was recorded simultaneously with central aortic BP measured in patients undergoing cardiac catheterization. Pearson's correlation was also derived for SBP and DBP. A trend comparison analysis of the beat-to-beat BP change was performed using a four-quadrant plot analysis with the exclusion zones of 0.5 mmHg/s to determine concordance, (i.e. the direction of beat-to-beat changes in SBP and DBP).

RESULTS

A total of 47 patients were included in the study. A total of 31 369 beats representing an average of 17.3 min of recording were used for analysis. The trend analysis yielded concordances of 84.4 and 83.5% for SBP and DBP, respectively. Respective correlations (Pearson's r) for SBP and DBP trends were 0.87 and 0.86 (P < 0.01). Tracking of beat-to-beat BP by Caretaker showed excellent concordance and correlation in the direction and the degree of BP change with central aortic BP, respectively.

CONCLUSION

This study supports the satisfactory performance of the Caretaker device in continuous tracking of central aortic BP beat-to-beat BP and provides a basis to develop an algorithm for absolute central aortic BP estimation in the future.

Syncope and the aging patient: Navigating the challenges

Syncope in the elderly patient is a common presentation and the most common causes are usually non-cardiac. Older adults however are more challenging dilemmas as their presentation is complicated by co-morbidities, mainly cardiovascular and neurodegenerative disorders. Frailty and cognitive impairment add to the ambiguity of the presentation, and polypharmacy is often a major modifiable contributing factor. Vasovagal syncope is a common presentation throughout life even as we age. It has a favorable prognosis and conservative management usually suffices. Vasovagal syncope in this population may be misdiagnosed as accidental falls and is frequently associated with injury, as is carotid sinus syndrome. The initial approach to these patients entails a detailed history and physical examination including a comprehensive medication history, orthostatic vital signs, and a 12-lead electrocardiogram. Further cardiac and neuroimaging rarely helps, unless directed by specific clinical findings. Head-up tilt testing and carotid sinus massage retain their diagnostic accuracy and safety in the elderly, and implantable loop recorders provide important information in many elderly patients with unexplained falls and syncope. The starting point in management of this population with non-cardiac syncope is attempting to withdraw unnecessary vasoactive and psychotropic medications. Non-pharmacologic and pharmacologic therapy for syncope in the elderly has limited efficacy and safety concerns. In selected patients, pacemaker therapy might offer symptomatic relief despite lack of efficacy when vasodepression is prominent. An approach focused on primary care with targeted specialist referral seems a safe and effective strategy.

Non-Invasive Continuous Measurement of Haemodynamic Parameters-Clinical Utility

The evaluation and monitoring of patients’ haemodynamic parameters are essential in everyday clinical practice. The application of continuous, non-invasive measurement methods is a relatively recent solution. CNAP, ClearSight and many other technologies have been introduced to the market. The use of these techniques for assessing patient eligibility before cardiac procedures, as well as for intraoperative monitoring is currently being widely investigated. Their numerous advantages, including the simplicity of application, time- and cost-effectiveness, and the limited risk of infection, could enforce their further development and potential utility. However, some limitations and contradictions should also be discussed. The aim of this paper is to briefly describe the new findings, give practical examples of the clinical utility of these methods, compare them with invasive techniques, and review the literature on this subject.

Continuous Noninvasive Blood Pressure Monitoring of Beat-By-Beat Blood Pressure and Heart Rate Using Caretaker Compared With Invasive Arterial Catheter in the Intensive Care Unit

OBJECTIVE

To examine the accuracy of noninvasively-derived peripheral arterial blood pressure (BP) by the Caretaker device (CT) against invasively measured arterial BP and the fidelity of heart rate variability by CT compared with electrocardiogram (ECG)-derived data.

DESIGN

Prospective cohort study.

PARTICIPANTS

Adult surgical and trauma patients admitted to the intensive care unit.

SETTING

Academic tertiary care medical center.

INTERVENTIONS

In a prospective manner, beat-by-beat BP by CT was recorded simultaneously with invasive arterial BP measured in patients in the intensive care unit. Invasive arterial BPs were compared with those obtained by the CT system. All comparisons among the CT data, arterial catheter data, and ECG data were postprocessed.

MEASUREMENTS AND MAIN RESULTS

From 37 enrolled patients, 34 were included with satisfactory data that overlapped between arterial catheter and CT. A total of 87,757 comparative data points were obtained for the 40-minute time window comparisons of the 34 patients, spanning approximately 22.5 hours in total. Systolic BP and diastolic BP correlations (Pearson coefficient), as well as the mean difference (standard deviation), were 0.92 and -0.36 (7.57) mmHg and 0.83 and -2.11 (6.00) mmHg, respectively. The overall interbeat correlation was 0.99, with the mean difference between interbeats obtained with the arterial BP and the CT of -0.056 ms (6.0).

CONCLUSIONS

This study validated the noninvasive tracking of BP using the CT device, and the pulse decomposition analysis approach is possible within the guidelines of the standard.

Toward Smart Monitoring with Phones, Watches, and Wearable Sensors

Smartphones are increasingly powerful computers that fit in our pocket. Thanks to dedicated applications or "Apps," they can connect with external sensors to record, analyze, display, store, and share multiple physiologic signals and data. In addition, because modern smartphones are equipped with accelerometers, gyroscopes, cameras, and pressure sensors, they can also be used to directly gather physiologic information. Smartphones and connected sensors are creating opportunities to empower patients, individualize perioperative care, follow patients during their surgical journey, and simplify clinicians' life.

Surrogate based continuous noninvasive blood pressure measurement

Arterial blood pressure is one of the most often measured vital parameters in clinical practice. State-of-the-art noninvasive ABP measurement technologies have noticeable limitations and are mainly based on uncomfortable techniques of complete or partial arterial occlusion by cuffs. Most commonplace devices provide only intermittent measurements, and continuous systems are bulky and difficult to apply correctly for nonprofessionals. Continuous cuffless ABP measurements are still an unmet clinical need and a topic of ongoing research, with only few commercially available devices. This paper discusses surrogate-based noninvasive blood pressure measurement techniques. It covers measurement methods of continuously and noninvasively inferring BP from surrogate signals without applying external pressures, except for reference or initialization purposes. The BP is estimated by processing signal features, so called surrogates, which are modulated by variations of BP. Discussed techniques include well-known approaches such as pulse transit time and pulse arrival time techniques, pulse wave analysis or combinations thereof. Despite a long research history, these methods have not found widespread use in clinical and ambulatory practice, in part due to technical limitations and the lack of a standardized regulatory framework. This work summarizes findings from an invited workshop of experts in the fields covering clinical expertise, engineering aspects, commercialization and standardization issues. The goal is to provide an application driven outlook, starting with clinical needs, and extending to technical actuality. It provides an outline of recommended research directions and includes a detailed overview of clinical use case scenarios for these technologies, opportunities, and limitations.

Non-invasive haemodynamic monitoring with Clearsight in patients undergoing spinal anaesthesia for total hip replacement. A prospective observational cohort study

BACKGROUND

Patients undergoing elective primary total hip replacement and spinal anesthesia may encounter significant hemodynamic instability Objective: The study is aimed at observing the haemodynamic modifications after spinal anaesthesia during total hip replacement in patients managed to "preload independence" with goal directed fluid therapy (GDFT) and monitored non-invasively with Clearsight.

METHODS

Thirty patients, aged 50-80 years, with an American Society of Anaesthesiologists' (ASA) score II-III, undergoing elective primary total hip replacement and spinal anaesthesia were enrolled. Patients were monitored with the EV1000 platform and the Clearsight finger-cuff and managed with a goal directed fluid therapy.

RESULTS

The 79% of the population showed preload independence at baseline. After spinal, the 93% did not show a significant mean arterial pressure reduction. In our population, 79% reported a decrease >10% of the stroke volume during surgery, while 66% in the Recovery Room. Patients showed an improvement in mean arterial pressure, systemic vascular resistances indexed (SVRI), stroke volume (SV) and stroke volume indexed (SVI) at spinal resolution compared to baseline.

CONCLUSIONS

Our cohort population showed hemodynamic stability throughout the study period, with increased SV and decreased SVRI at spinal resolution compared to basal values. Further randomized prospective studies are advocated in the same setting.

Blood pressure monitoring in sleep: time to wake up

Hypertension is a highly common condition with well-established adverse consequences. Ambulatory blood pressure monitoring has repeatedly been shown to better predict cardiovascular outcomes and mortality, compared to single office visit blood pressure. Non-dipping of sleep-time blood pressure is an independent marker for increased cardiovascular risk. We review blood pressure variability and the challenges of blood pressure monitoring during sleep. Although pathological sleep such as obstructive sleep apnea has been associated with non-dipping of sleep-time blood pressure, blood pressure is not routinely measured during sleep due to lack of unobtrusive blood pressure monitoring technology. Second, we review existing noninvasive continuous blood pressure monitoring technologies. Lastly, we propose including sleep-time blood pressure monitoring during sleep studies and including sleep studies in patients undergoing ambulatory blood pressure monitoring.

The application of a neural network to predict hypotension and vasopressor requirements non-invasively in obstetric patients having spinal anesthesia for elective cesarean section (C/S)

Background

Neural networks are increasingly used to assess physiological processes or pathologies, as well as to predict the increased likelihood of an impending medical crisis, such as hypotension.

Method

We compared the capabilities of a single hidden layer neural network of 12 nodes to those of a discrete-feature discrimination approach with the goal being to predict the likelihood of a given patient developing significant hypotension under spinal anesthesia when undergoing a Cesarean section (C/S). Physiological input information was derived from a non-invasive blood pressure device (Caretaker [CT]) that utilizes a finger cuff to measure blood pressure and other hemodynamic parameters via pulse contour analysis. Receiver-operator-curve/area-under-curve analyses were used to compare performance.

Results

The results presented here suggest that a neural network approach (Area Under Curve [AUC] = 0.89 [p < 0.001]), at least at the implementation level of a clinically relevant prediction algorithm, may be superior to a discrete feature quantification approach (AUC = 0.87 [p < 0.001]), providing implicit access to a plurality of features and combinations thereof. In addition, the expansion of the approach to include the submission of other physiological data signals, such as heart rate variability, to the network can be readily envisioned.

Conclusion

This pilot study has demonstrated that increased coherence in Arterial Stiffness (AS) variability obtained from the pulse wave analysis of a continuous non-invasive blood pressure device appears to be an effective predictor of hypotension after spinal anesthesia in the obstetrics population undergoing C/S.

This allowed us to predict specific dosing thresholds of phenylephrine required to maintain systolic blood pressure above 90 mmHg.

Wireless vitals-Proof of concept for wireless patient monitoring in an emergency department setting

Vital sign assessment is a common task in emergency medicine, but resources for continuous monitoring are restricted, data is often recorded manually, and entangled wires cause frustration. Therefore, we designed a small, wireless photoplethysmographic device capable of continuously assessing pulse, respiratory frequency and oxygen saturation on the sternum and tested the performance and feasibility in an emergency department setting. Fifty (56.3 ± 20.2 years), consenting emergency patients (29 male) were recruited. Heart rate, respiratory rate and oxygen saturation were recorded simultaneously using the device and standard monitoring equipment. Data was compared using Bland-Altman plotting (heart rate, respiratory rate) and mean difference (oxygen saturation). The bias for heart- and respiratory rate was 0.4 (limits of agreements -11.3, 12.2 and -6.1, 7.0). Mean difference for oxygen saturation was -0.21 ± 2.35%. This may be the first wireless device to use photoplethysmography on the sternum for vital sign assessment. We noted good agreement with standard monitors, but lack of standardization in data processing between monitoring systems may limit the generalizability of these findings. Although further improvements are needed, the feasibility of this approach provides proof of concept for a new paradigm of large scale, wireless patient monitoring.

Wireless Monitoring for Office-Based Anesthesia

Current research on wireless hemodynamic monitoring during anesthesia is limited as the topic is just beginning to be explored. The aim of this article is to stimulate technological advancements in monitored anesthesia care that will increase safety and efficiency. Here, we introduce this exciting new concept and propose an innovative model for monitoring patients undergoing office-based anesthesia.

Continuous Non-Invasive Arterial Pressure Assessment during Surgery to Improve Outcome

Blood pressure (BP) is one of the most important variables evaluated during almost every medical examination. Most national anesthesiology societies recommend BP monitoring at least once every 5 min in anesthetized subjects undergoing surgical procedures. In most cases, BP is monitored non-invasively using oscillometric cuffs. Although the risk of arterial cannulation is not very high, the invasive BP monitoring is usually indicated only in the case of high-risk patients or in complex surgical procedures. However, recent evidence points out that when using intermittent BP monitoring short periods of hypotension may be overlooked. In addition, large datasets have demonstrated that even short periods of low BP (or their cumulative duration) may have a detrimental impact on the development of postoperative outcome including increased risk of acute kidney or myocardial injury development. Recently marketed continuous non-invasive blood pressure monitoring tools may help us to recognize the BP fluctuation without the associated burden of arterial cannulation filling the gap between intermittent non-invasive cuff and continuous invasive arterial pressure. Among others, several novel devices based either on volume clamp/vascular unloading method or on applanation tonometry are nowadays available. Moreover, several near-future smart technologies may lead to better hypotension recognition or even prediction potentially improving our ability to maintain BP stability throughout the anesthesia or surgical procedure. In this review, novel or emerging technologies of non-invasive continuous blood pressure assessment and their potential to improve postoperative outcome are discussed.