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.

A new continuous noninvasive finger cuff device (Vitalstream) for cardiac output that communicates wirelessly via bluetooth or Wi-Fi.

BACKGROUND: The new noninvasive Vitalstream (VS) continuous physiological monitor (Caretaker Medical LLC, Charlottesville, Virginia), allows continuous cardiac output by a low pump-inflated, finger cuff that pneumatically couples arterial pulsations via a pressure line to a pressure sensor for detection and analysis. Physiological data are communicated wirelessly to a tablet-based user interface via Bluetooth or Wi-Fi. We evaluated its performance against thermodilution cardiac output in patients undergoing cardiac surgery. METHODS: We compared the agreement between thermodilution cardiac output to that obtained by the continuous noninvasive system during cardiac surgery pre and post-cardiac bypass. Thermodilution cardiac output was performed routinely when clinically indicated by an iced saline cold injectate system. All comparisons between VS and TD/CCO data were post-processed. In order to match the VS CO readings to the averaged discrete TD bolus data, the averaged CO readings of the ten seconds of VS CO data points prior to a sequence of TD bolus injections was matched. Time alignment was based on the medical record time and the VS time-stamped data points. The accuracy against reference TD measurements was assessed via Bland-Altman analysis of the CO values and standard concordance analysis of the ΔCO values (with a 15% exclusion zone). RESULTS: Analysis of the data compared the accuracy of the matched measurement pairs of VS and TD/CCO VS absolute CO values with and without initial calibration to the discrete TD CO values, as well as the trending ability, i.e., ΔCO values of the VS physiological monitor compared to those of the reference. The results were comparable with other non-invasive as well as invasive technologies and Bland-Altman analyses showed high agreement between devices in a diverse patient population. The results are significant regarding the goal of expanding access to effective, wireless and readily implemented fluid management monitoring tools to hospital sections previously not covered because of the limitations of traditional technologies. CONCLUSION: This study demonstrated that the agreement between the VS CO and TD CO was clinically acceptable with a percent error (PE) of 34.5 to 38% with and without external calibration. The threshold for an acceptable agreement between the VS and TD was considered to be below 40% which is below the threshold recommended by others.

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.

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.

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.

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.

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

BACKGROUND: Despite increased interest in non-invasive arterial pressure monitoring, the majority of commercially available technologies have failed to satisfy the limits established for the validation of automatic arterial pressure monitoring by the Association for the Advancement of Medical Instrumentation (AAMI). According to the ANSI/AAMI/ISO 81060-2:2013 standards, the group-average accuracy and precision are defined as acceptable if bias is not greater than 5 mmHg and standard deviation is not greater than 8 mmHg. In this study, these standards are used to evaluate the CareTaker® (CT) device, a device measuring continuous non-invasive blood pressure via a pulse contour algorithm called Pulse Decomposition Analysis. METHODS: A convenience sample of 24 patients scheduled for major abdominal surgery were consented to participate in this IRB approved pilot study. Each patient was monitored with a radial arterial catheter and CT using a finger cuff applied to the contralateral thumb. Hemodynamic variables were measured and analyzed from both devices for the first thirty minutes of the surgical procedure including the induction of anesthesia. The mean arterial pressure (MAP), systolic and diastolic blood pressures continuously collected from the arterial catheter and CT were compared. Pearson correlation coefficients were calculated between arterial catheter and CT blood pressure measurements, a Bland-Altman analysis, and polar and 4Q plots were created. RESULTS: The correlation of systolic, diastolic, and mean arterial pressures were 0.92, 0.86, 0.91, respectively (p < 0.0001 for all the comparisons). The Bland-Altman comparison yielded a bias (as measured by overall mean difference) of -0.57, -2.52, 1.01 mmHg for systolic, diastolic, and mean arterial pressures, respectively with a standard deviation of 7.34, 6.47, 5.33 mmHg for systolic, diastolic, and mean arterial pressures, respectively (p < 0.001 for all comparisons). The polar plot indicates little bias between the two methods (90%/95% CI at 31.5°/52°, respectively, overall bias = 1.5°) with only a small percentage of points outside these lines. The 4Q plot indicates good concordance and no bias between the methods. CONCLUSIONS: In this study, blood pressure measured using the non-invasive CT device was shown to correlate well with the arterial catheter measurements. Larger studies are needed to confirm these results in more varied settings. Most patients exhibited very good agreement between methods. Results were well within the limits established for the validation of automatic arterial pressure monitoring by the AAMI.

Assessment of Cardiovascular Parameters during Meditation with Mental Targeting in Varsity Swimmers.

Introduction. Athletes who develop an immunosuppressed state because of intensive training get upper respiratory infections (URIs) and may respond to meditation. Reflective exercise (RE), a westernized form of Qigong, combines meditation, breathing, and targeted mental attention to an internal pulsatile sensation, previously shown to protect varsity swimmers from URIs during the height of training. We report here the evaluation of cardiovascular parameters measured during meditation combined with targeted imagery (interoception) in a cohort of varsity swimmers taught RE. Methods. Thirteen subjects were enrolled on a prospective protocol that used the CareTaker, a noninvasive cardiovascular monitor before, during, and after RE training. Questionnaires regarding targeted mental imagery focusing on a pulsatile sensation were collected. The cardiovascular parameters include heart rate, blood pressure, and heart rate variability (HRV). Results. Increased variance in the subjects' BP and HRV was observed over the training period of 8 weeks. In nine subjects there was an increased low frequency (LF) HRV that was significantly (p < 0.05) associated with the subject's awareness of the pulsatile sensation that makes up a basic part of the RE practice. Summary. These data support further evaluation of HRV measurements in subjects while meditating with mental imagery. This direction could contribute to better understanding of neurocardiac mechanisms that relate meditation to enhanced immunity.

Utility of a multimodal neurophysiologic assessment tool in distinguishing between individuals with and without a history of mild traumatic brain injury.

This was a preliminary validation study of a multimodal concussion assessment battery incorporating eye-tracking, balance, and neurocognitive tests on a new hardware platform, the Computerized Brain Injury Assessment System. Using receiver-operating characteristics analyses, (1) we identified a subset of the most discriminating neurophysiological assessment tests involving smooth pursuit eye movement tracking errors, corrective saccade counts, a balance score ratio sensitive to vestibular balance performance, and two neurocognitive tests of response speed and memory/incidental learning; (2) we demonstrated the enhancement in discriminatory capability of detecting concussion-related deficits through the combination of the identified subset of assessments; and (3) we demonstrated the effectiveness of a robust and readily implemented global scoring approach was demonstrated for both eye track and balance assessment tests. These results are significant in introducing a comprehensive solution for concussion assessment that incorporates an economical, compact, and mobile hardware system and an assessment battery that is multimodal and time efficient and whose efficacy has been demonstrated on a preliminary basis. This represents a significant step toward the goal of a system capable of making a dependable return-to-play/duty determination based on concussion likelihood.

Validation of the pulse decomposition analysis algorithm using central arterial blood pressure.

BACKGROUND: There is a significant need for continuous noninvasive blood pressure (cNIBP) monitoring, especially for anesthetized surgery and ICU recovery. cNIBP systems could lower costs and expand the use of continuous blood pressure monitoring, lowering risk and improving outcomes.The test system examined here is the CareTaker® and a pulse contour analysis algorithm, Pulse Decomposition Analysis (PDA). PDA's premise is that the peripheral arterial pressure pulse is a superposition of five individual component pressure pulses that are due to the left ventricular ejection and reflections and re-reflections from only two reflection sites within the central arteries.The hypothesis examined here is that the model's principal parameters P2P1 and T13 can be correlated with, respectively, systolic and pulse pressures. METHODS: Central arterial blood pressures of patients (38 m/25 f, mean age: 62.7 y, SD: 11.5 y, mean height: 172.3 cm, SD: 9.7 cm, mean weight: 86.8 kg, SD: 20.1 kg) undergoing cardiac catheterization were monitored using central line catheters while the PDA parameters were extracted from the arterial pulse signal obtained non-invasively using CareTaker system. RESULTS: Qualitative validation of the model was achieved with the direct observation of the five component pressure pulses in the central arteries using central line catheters. Statistically significant correlations between P2P1 and systole and T13 and pulse pressure were established (systole: R square: 0.92 (p < 0.0001), diastole: R square: 0.78 (p < 0.0001). Bland-Altman comparisons between blood pressures obtained through the conversion of PDA parameters to blood pressures of non-invasively obtained pulse signatures with catheter-obtained blood pressures fell within the trend guidelines of the Association for the Advancement of Medical Instrumentation SP-10 standard (standard deviation: 8 mmHg(systole: 5.87 mmHg, diastole: 5.69 mmHg)). CONCLUSIONS: The results indicate that arterial blood pressure can be accurately measured and tracked noninvasively and continuously using the CareTaker system and the PDA algorithm. The results further support the physical model that all of the features of the pressure pulse envelope, whether in the central arteries or in the arterial periphery, can be explained by the interaction of the left ventricular ejection pressure pulse with two centrally located reflection sites.

Utility of a novel watch-based pulse detection system to detect pulselessness in human subjects.

BACKGROUND: The Wriskwatch is a novel, watch-based pulse detection device that detects the loss of a radial pulse via advanced pulse detection technology and immediately contacts emergency medical systems. OBJECTIVE: The purpose of this first-in-man, prospective, single-blinded, phase 1 study was to evaluate the ability of this device to detect motionlessness and pulselessness in human subjects as a simulation of sudden cardiac death. METHODS: The study cohort consisted of 34 patients: 24 hospitalized patients and 10 presenting for implantable cardioverter-defibrillator (ICD) testing. We simulated loss of pulse in our hospitalized patients via blood pressure cuff inflation to occlude the brachial arterial pulse at random times in 20 subjects with no inflations in 4 while the patients were instructed to keep perfectly still. Of the 10 patients undergoing ventricular fibrillation (VF) induction during ICD testing, the exact times of VF induction were recorded. A blinded reviewer determined if and when motion and pulse were lost in all patients using only data from the device. RESULTS: Of the 34 patients, 2 had an unusable signal, 1 had device ejection during ICD testing, and 2 had too much motion artifact and were excluded (5/34 patients, or 14.7% of the total cohort). Of the 29 remaining subjects, 4 had no loss of pulse of which the device correctly identified 3. In the remaining 25 patients, the device correctly identified the time of pulselessness in 23 of 25 (16/17 hospitalized patients and 7/8 ICD patients). Overall, the Wriskwatch was worn for a total of 561.2 minutes. Pulselessness was present for 5.8 minutes. The sensitivity of the watch to detect pulse status (based on 15-second intervals) was 99.9%, and the specificity was 90.3%. CONCLUSION: The Wriskwatch is a novel device that shows promise as a tool to hasten activation of emergency medical systems and facilitate early defibrillation in patients with cardiac arrest.

Pulse Decomposition Analysis of the digital arterial pulse during hemorrhage simulation.

BACKGROUND: Markers of temporal changes in central blood volume are required to non-invasively detect hemorrhage and the onset of hemorrhagic shock. Recent work suggests that pulse pressure may be such a marker. A new approach to tracking blood pressure, and pulse pressure specifically is presented that is based on a new form of pulse pressure wave analysis called Pulse Decomposition Analysis (PDA). The premise of the PDA model is that the peripheral arterial pressure pulse is a superposition of five individual component pressure pulses, the first of which is due to the left ventricular ejection from the heart while the remaining component pressure pulses are reflections and re-reflections that originate from only two reflection sites within the central arteries. The hypothesis examined here is that the PDA parameter T13, the timing delay between the first and third component pulses, correlates with pulse pressure.T13 was monitored along with blood pressure, as determined by an automatic cuff and another continuous blood pressure monitor, during the course of lower body negative pressure (LBNP) sessions involving four stages, -15 mmHg, -30 mmHg, -45 mmHg, and -60 mmHg, in fifteen subjects (average age: 24.4 years, SD: 3.0 years; average height: 168.6 cm, SD: 8.0 cm; average weight: 64.0 kg, SD: 9.1 kg). RESULTS: Statistically significant correlations between T13 and pulse pressure as well as the ability of T13 to resolve the effects of different LBNP stages were established. Experimental T13 values were compared with predictions of the PDA model. These interventions resulted in pulse pressure changes of up to 7.8 mmHg (SE = 3.49 mmHg) as determined by the automatic cuff. Corresponding changes in T13 were a shortening by -72 milliseconds (SE = 4.17 milliseconds). In contrast to the other two methodologies, T13 was able to resolve the effects of the two least negative pressure stages with significance set at p < 0.01. CONCLUSIONS: The agreement of observations and measurements provides a preliminary validation of the PDA model regarding the origin of the arterial pressure pulse reflections. The proposed physical picture of the PDA model is attractive because it identifies the contributions of distinct reflecting arterial tree components to the peripheral pressure pulse envelope. Since the importance of arterial pressure reflections to cardiovascular health is well known, the PDA pulse analysis could provide, beyond the tracking of blood pressure, an assessment tool of those reflections as well as the health of the sites that give rise to them.

The structure of the radial pulse--a novel noninvasive ambulatory blood pressure device.

A non-invasive wrist sensor, BPGuardian (Empirical Technologies C., Charlottesville, VA) has been developed that provides continuous pressure readings by de-convolving the radial arterial pulse waveform into its constituent component pulses (Pulse Decomposition Analysis). Results agree with the predictions of the model regarding the temporal and amplitudinal behavior of the component pulses as a function of changing diastolic and systolic blood pressure.