Objective:Growing interest in quantitative Doppler assessment has underscored the need for reliable, operator-independent tools to evaluate peripheral arterial circulation. This study aimed to evaluate the reliability of a novel ultrasound Doppler device (earlybird) for measuring blood-flow velocity in lower-extremity arteries and to validate its consistency across raters. We further explored multiple hemodynamic parameters derived from the Doppler spectrogram to examine their reproducibility and potential clinical applicability. Methods:Thirty-five participants, including 25 with varying degrees of peripheral arterial disease (PAD) and 10 healthy individuals, were recruited. Four raters performed independent measurements of the peripheral blood-flow velocity in each participant (280 measurements). Six blood-flow parameters were extracted from the Doppler spectrograms: peak systolic velocity (PSV), time-averaged velocity (TAV), end-diastolic velocity (EDV), pulsatility index (PI), resistive index (RI), and acceleration time (AT). The intraclass correlation coefficient (ICC) was used to assess reliability, which was visualized in scatter plots and Bland-Altman plots with 95% limits of agreement. Results:Good correlation and agreement among the different raters were observed, with inter-rater reliability ranging from an ICC of 0.755-0.835 (p < 0.001). Intra-rater reliability showed poor to excellent correlation, with ICCs ranging from 0.450 to 0.961, (p < 0.001). Bland-Altman plots revealed wide 95% limits of agreement for PSV, TAV, EDV, and PI, but narrower limits for RI (-9.8% to 9.8%) and AT (-17.3% to 17.1%). Conclusion:Earlybird was shown to be a reliable tool for assessing peripheral arteries across raters, with good inter- and intra-rater reliability. The angle-independent variables, RI and AT, showed narrow 95% limits of agreement, which justifies further exploration.

Background:The resuscitation society calls for precision-guided cardiopulmonary resuscitation (CPR), as current methods are inaccurate and time-consuming. RescueDoppler, a novel hands-free Doppler ultrasound system, continuously measures carotid blood flow during CPR. This pilot study assessed its performance, safety, and ability to detect chest compression-generated blood flow, spontaneous circulation, and return of spontaneous circulation (ROSC). Method:We investigated RescueDoppler in adult cardiac arrest patients at two centres, in-hospital (IHCA) and out-of-hospital (OHCA). The cardiac arrest team placed the RescueDoppler probe over the left common carotid artery with a self-adhesive patch, collecting blinded data during CPR. Data were later interpreted and time-synchronized with defibrillator data using custom MATLAB® software. Results:RescueDoppler was used in 26 IHCA and 36 OHCA patients from October 2023 to September 2024. Carotid blood flow curves were analyzed in 36 patients and synchronized with defibrillator data in 30. The RescueDoppler identified blood flow velocities generated by chest compressions and detected spontaneous circulation during rhythm checks. ROSC was defined by the presence of systolic and diastolic blood flow. No adverse events were reported but there were 22 device deficiencies mostly related to the self-adhesive patch and connecting cable. The system is user-friendly and requires minimal training. Conclusion:Real-time detection of blood flow in the carotid artery with hands-free Doppler ultrasound during CPR is safe and feasible, although the fastening patch and host unit need optimization. The RescueDoppler system detects spontaneous circulation and ROSC during rhythm checks and ongoing chest compressions. Further research is required to confirm clinical relevance.

BackgroundIdentifying spontaneous circulation during cardiopulmonary resuscitation (CPR) is challenging. Current methods, which involve intermittent and time-consuming pulse checks, necessitate pauses in chest compressions. This issue is problematic in both in-hospital cardiac arrest and out-of-hospital cardiac arrest situations, where resources for identifying circulation during CPR may be limited. The fraction of chest compression plays a pivotal role in improving survival rates. To address this challenge, we evaluated a newly developed hands-free, continuous carotid Doppler system (RescueDoppler), designed to identify spontaneous circulation during chest compressions. In our study, we utilized a porcine model of cardiac arrest to investigate sequences of ventricular fibrillation, followed by defibrillation, and monitoring for the return of spontaneous circulation during chest compressions with the carotid Doppler system. We explored both manual compressions at 100 and 50 compressions per minute and mechanical compressions. To estimate the detection rate (i.e., sensitivity), we employed a logistic mixed model with animal identity as random effect.ResultsOffline analysis of Doppler color M-mode and spectral display successfully identified spontaneous circulation during chest compressions in all compression models. Spontaneous circulation was detected in 51 of 59 sequences, yielding an expected sensitivity of 98% with a 95% confidence interval of 59% to 99%.ConclusionThe RescueDoppler, a continuous hands-free carotid Doppler system, demonstrates an expected sensitivity of 98% for identifying spontaneous circulation during both manual and mechanical chest compressions. Clinical studies are needed to further validate these findings.

Background: During cardiopulmonary resuscitation (CPR), identifying the return of spontaneous circulation (ROSC) is challenging. Methods such as manual palpation, end-tidal carbon dioxide, and point-of-care ultrasound to detect ROSC are inaccurate, time-consuming, or intermittent. They may also require halting or prolonging no-compression time to identify signs of circulation. Maintaining a high compression fraction is associated with an increased likelihood of achieving ROSC. Aim: This study aimed to investigate if using a novel continuous hands-free carotid Doppler system (RescueDoppler (RD)) could identify ROSC during chest compressions by distinguishing between spontaneous and chest compression-generated carotid blood flow velocity. Methods: We used a porcine cardiac arrest model to investigate the RD. The RD probe was positioned and fixated over the carotid artery. An invasive blood pressure catheter was inserted in the contralateral carotid artery. An implantable cardioverter defibrillator (ICD) was utilized to induce sequences of ventricular fibrillation followed by defibrillation and chest compressions (cardiac arrest sequences). Compressions were administered manually at a rate of 100 or 50 compressions per minute or using a mechanical chest compression device (LUCAS). Doppler blood flow velocity curves were retrospectively analyzed for signs of ROSC by examining both spontaneous and/or compression-generated velocities (Fig. 1,2). We combined color M-mode and Doppler spectrum (Fig. 1) to differentiate between chest compression and spontaneous velocities. Results: Data from eight animals (mean weight 30 kg) and 56 cardiac arrest sequences were included. In the analysis, chest compressions were identified as tissue movements through the whole spectrum of the color M-mode, in the spectral display (Fig. 1), or both. Spontaneous velocities were identified in a specific carotid depth of the color M-mode and between compression-generated peak velocities in the Doppler specter (Fig. 1). ROSC was confirmed by pausing chest compressions and evaluating ECG and invasive blood pressure. We identified spontaneous circulation during manual and mechanical chest compressions in 55 of 56 sequences. Conclusions: In a porcine cardiac arrest model, with ROSC, we could differentiate between spontaneous circulation and chest compression-generated blood flow velocity of the carotid artery using RescueDoppler.

BACKGROUND:In this pilot study, we investigated continuous cerebral blood flow velocity measurements to explore cerebrovascular hemodynamics in infants with congenital heart disease undergoing cardiac surgery. METHODS:A non-invasive transfontanellar cerebral Doppler monitor (NeoDoppler) was used to monitor 15 infants (aged eight days to nine months) during cardiac surgery with cardiopulmonary bypass. Numerical and visual analyses were conducted to assess trends and events in Doppler measurements together with standard monitoring equipment. The mean flow index, calculated as the moving Pearson correlation between mean arterial pressure and time averaged velocity, was utilized to evaluate dynamic autoregulation. Two levels of impaired autoregulation were defined (Mean flow index >0.3/0.45), and percentage of time above these limits were calculated. RESULTS:High quality recordings were achieved during 90.6% of the monitoring period. There was a significant reduction in time averaged velocity in all periods of cardiopulmonary bypass. All patients showed a high percentage of time with impaired dynamic autoregulation, with Mean flow index >0.3 and 0.45: 73.71% ± 9.06% and 65.16% ± 11.27% respectively. Additionally, the system promptly detected hemodynamic events. CONCLUSION:Continuous transfontanellar cerebral Doppler monitoring could become an additional tool in enhancing cerebral monitoring in infants during cardiac surgery. IMPACT:This pilot study demonstrates the feasibility of continuous transfontanellar Doppler monitoring of cerebral blood flow velocities during cardiac surgery in infants. It also demonstrates a high proportion of time with impaired cerebral autoregulation during cardiac surgery based on the Mean flow index. Continuous transfontanellar Doppler could become a useful tool to improve cerebral monitoring and provide new pathophysiological insight.

Background: Transcatheter interventions are increasingly used in children with congenital heart disease. However, these interventions can affect cardiac output and cerebral circulation. In this pilot study, we aimed to investigate the use of NeoDoppler, a continuous transfontanellar cerebral Doppler monitoring system, to evaluate the impact of transcatheter interventions on cerebral circulation. Methods: Nineteen participants under one year of age (mean age 3.5 months) undergoing transcatheter cardiac interventions were prospectively included. Transfontanellar cerebral Doppler monitoring with the NeoDoppler system was initiated after intubation and continued until the end of the procedure. Results: Instant detection of changes in cerebral blood flow were observed across a spectrum of transcatheter interventions. Balloon aortic valvuloplasty demonstrated temporary cessation of cerebral blood flow during balloon inflation. Increase in cerebral diastolic blood flow velocity and decreased pulsatility were observed during patent ductus arteriosus occlusion. Changes in cerebral blood flow patterns were detected in two patients who encountered complications during their transcatheter interventions. There was no significant change in Doppler parameters before and after the interventions for the entire patient group. High quality recordings were achieved in 87.3% of the monitoring period. Conclusions: Continuous transfontanellar cerebral Doppler is feasible in monitoring cerebral hemodynamic trends and shows instantaneous changes associated with interventions and complications. It could become a useful monitoring tool during transcatheter interventions in infants.

Background: Real-time hemodynamic feedback devices provide information on cardiopulmonary resuscitation (CPR) quality. This can improve hand positioning and technique, thereby maximizing blood flow and potentially improve survival. Hypothesis: We hypothesize that a newly developed hands-free Doppler for carotid blood flow velocity (RescueDoppler, RD), can identify optimal vs. suboptimal chest compression sites during CPR. Aim: To assess the potential of the RD device to continuously monitor the effect of each compression by ultrasound metrics and waveforms in a porcine model. Methods: Ventricular fibrillation was induced in 5 pigs using an ICD. Manual CPR (blinded for hemodynamic data) was performed for 10 seconds at 3 different compression sites in random order (Fig.), and repeated 6 times. We analyzed ultrasound waveforms with Time Average Velocity (TAV) in a linear mixed model with site as fixed effect, and animal and site within animal as random effects. We further compared TAV to invasive systolic blood pressure (SBP) from the contralateral carotid artery. Results: Data from 5 pigs (mean weight 31.2 kg) and 29 of 30 sequences were included. Overall, blood flow velocity was highest at compression site 2 (TAV 33 cm/s, P<0.01), but there was significant variability (P<0.01) in animals (SD= 3.7) and at sites within animal (SD= 7). A compression site yielding the highest TAV (range 19 to 48 cm/s) or lowest TAV (6-25 cm/s) was successfully identified in all animals with corresponding SBPs 50-81 mmHg, and 46-64 mmHg, respectively. The correlation between TAV and SBP was 0.62-0.90 within animals. Conclusions In this animal study, a newly developed hands-free Doppler enabled assessment of blood flow velocity during CPR and detected significant variation according to chest compression site. RD identified the sites with both high and low blood flow velocities and is thus a promising device for effectively identifying the optimal and suboptimal chest compression sites during CPR.

Aims:To improve quantification of valvular regurgitation, a 3D high-pulse repetition frequency Doppler (3D HPRFD) method was developed for regurgitant volume (RVol) estimation from transthoracic echocardiography (TTE). Although successfully applied in vitro and in selected clinical cases, a systematic clinical validation of 3D HPRFD has not been published. Hence, our aims were to investigate (i) feasibility of 3D HPRFD and (ii) correlation between 3D HPRFD and RVol estimates obtained by the 2D proximal isovelocity surface area (PISA) method and cardiac magnetic resonance (CMR) in patients with either aortic regurgitation (AR) or mitral regurgitation (MR). Methods and results:We included 45 patients with AR (42% mild, 40% moderate, and 18% severe) and 45 with MR (67% mild, 24% moderate, and 9% severe). Median time between start of TTE and start of CMR was 1.5 h, minimizing changes in load. Overall feasibility of 3D HPRFD was 56% in AR and 44% in MR. Feasibility was only 25% in patients with severe regurgitation. In AR, estimated RVol from 3D HPRF did not correlate with estimated RVol from PISA or CMR [Spearman rho = 0.06 (P = 0.78) and 0.04 (P = 0.4), respectively]. In MR, RVol estimates from 3D HPRFD correlated with PISA (rho = 0.72, P < 0.001) but not with CMR (rho = 0.31, P = 0.43). Conclusion:Regurgitant volume estimation by 3D HPRFD had a low feasibility, especially in severe regurgitation, and in general correlated poorly with PISA and CMR estimates. In its current state, 3D HPRFD is not ready for clinical use.

Objective Fat embolism syndrome and cerebral fat emboli are rare yet serious conditions arising from systemic distribution of bone marrow emboli. Emboli are known to produce high-intensity transient signals (HITS) in a Doppler signal. We hypothesized that both intramedullary nailing in pigs and median sternotomy in human infants cause bone marrow release, that some of these cause cerebral emboli, and that these were detectable by a new cerebral doppler ultrasound monitoring system (NeoDoppler). We also aimed to describe the intensity of HITS generated during these procedures. Methods Specific pathogen-free Norwegian landrace pigs were allocated to either bilateral femoral nailing or injection of autologous bone marrow (positive controls). Testing was carried out under continuous Doppler monitoring. Presence of cerebral emboli was confirmed with histology. NeoDoppler data from infants undergoing sternotomy prior to cardiac surgery were investigated for comparison. Results Eleven of twelve pigs were monitored with cerebral Doppler ultrasound during femoral surgery. HITS were seen in five (45%). Brain biopsies demonstrated bone marrow emboli in 11 of the 12 (92%). Four positive control pigs received intraarterial injections of bone marrow, saline, or contrast, and strong HITS were detected in all pigs (100%). Median sternotomy in eight human infants was associated with a significant increase in embolic burden; the HITS intensity was lower than HITS in pigs. Conclusion High-frequency cerebral Doppler ultrasound is a valuable tool for perioperative monitoring that can detect emboli in real-time, but sensitivity and specificity for bone marrow emboli may be limited and size-dependent.

Background: An accessible tool is required to analyze volume flow trends in arteriovenous fistulas for hemodialysis. Earlybird, an easy-to-place ultrasound Doppler device, has shown comparable accuracy to duplex ultrasound. In this study, we compared volume flow measurements obtained with duplex ultrasound and the dilution technique to an enhanced earlybird device, featuring a dual Doppler probe system, eliminating the requirement for a known insonation angle. Methods: Nine patients with a distal radiocephalic arteriovenous fistula were monitored for 12 months with regular volume flow measurements. Correlation and inter- and intra-class reliability analyses were conducted. Results: An overall moderate correlation was observed between earlybird and duplex ultrasound or dilution technique (intraclass correlation coefficient = 0.606 (95% confidence interval 0.064, 0.721) and 0.581 (0.039, 0.739), respectively). Duplex ultrasound compared to dilution measurements, demonstrated an overall moderate correlation (0.725 (0.219, 0.843)). Correlation between earlybird and duplex ultrasound was stronger for the arteriovenous fistula (0.778 (0.016, 0.901)) than the brachial artery (0.381 (−0.062, 0.461)). For earlybird, inter-rater reliability was excellent for the arteriovenous fistula (0.907 (0.423, 0.930)) and poor for the brachial artery (0.430 (0.241, 0.716)). Duplex ultrasound showed a good inter-rater reliability (arteriovenous fistula: 0.843 (0.610, 0.871), brachial artery: 0.819 (0.477, 0.864)). The overall intra-rater reliability was good for duplex ultrasound (rater A: 0.893 (0.727, 0.911); rater B: 0.853 (0.710, 0.891)), while excellent for earlybird (rater A: 0.905 (0.819, 0.928); rater B: 0.921 (0.632, 0.969)). Conclusion: We observed a weaker correlation in the measurements of volume flow rates in arteriovenous fistulas when obtained using earlybird compared to dilution technique, unlike the comparison between duplex ultrasound and the dilution technique. However, inter-rater reliability for the arteriovenous fistula was excellent with earlybird and good with duplex ultrasound, indicating the potential of earlybird as a tool for frequent measurements, enabling trend surveillance and predicting adverse outcomes.

Background: Controversy exists regarding surveillance of arteriovenous fistulas for hemodialysis to increase patency. A significant reduction in volume flow rate (VFR) should lead to diagnostic evaluation and eventually intervention. Several methods are available for VFR measurements, but all of them are associated with low reproducibility. VFR trend analysis is suggested as an improved solution. It is therefore a need to find user-friendly, cost and time-effective modalities. We present a novel Doppler ultrasound device (earlybird) which could bridge this gap. It includes an easy-to-use and light-weight single element transducer. Methods: In an experimental and clinical setting, we compared earlybird to duplex ultrasound to assess VFR. In a closed circuit of blood-mimicking fluid, 36 paired calculations of calibrated, duplex ultrasound and earlybird VFR was measured. In addition, 23 paired recordings of duplex ultrasound and earlybird VFR was measured in 16 patients with underarm arteriovenous fistulas. Pearson correlation, intraclass correlation coefficient, root-mean-square and Bland-Altman plots were analyzed. Results: Strong correlation ( r = 0.991, p < 0.001), and excellent level of agreement (ICC = 0.970 (95% CI 0.932 - 0.985), p < 0.001) between earlybird and the calibrated VFR was found in the experimental setup. This was confirmed in the clinical setting, with a strong correlation ( r = 0.781, p < 0.001) and moderate to good level of agreement (ICC = 0.750 (95% CI 0.502–0.885), p < 0.001) between earlybird and duplex ultrasound VFR measured at the arteriovenous fistulas outflow veins. In the Bland-Altman plot-analysis for the experimental setup, we found smaller limits of agreement, a smaller consistent and proportional bias, as well as greater accuracy of earlybird than DUS when compared to the calibrated VFR. Conclusion: Earlybird is a feasible tool for VFR measurements and could be a future promising device for easy assessment and surveillance of AVF for hemodialysis.

BACKGROUND:Current methods for fetal surveillance during labor have significant limitations. Since continuous fetal cerebral blood flow velocity (CBFV) monitoring during labor may add valuable information about fetal well-being, we developed a new ultrasound system called VisiBeam. VisiBeam consists of a flat probe (diameter 11 mm) with a cylindric plane wave beam, a vacuum attachment (diameter 40 mm), a scanner, and a display. AIMS:To assess the feasibility of VisiBeam for continuous fetal CBFV monitoring during labor, and to study changes in CBFV during uterine contractions. STUDY DESIGN:Descriptive observational study. SUBJECTS:Twenty-five healthy women in labor with a singleton fetus in cephalic presentation at term. A transducer was placed over a fontanelle and attached to the fetal head with vacuum suction. OUTCOME MEASURES:Achievement of continuous good quality fetal CBFV measures, such as peak systolic velocity, time averaged maximum velocity and end diastolic velocity. Trend plots of velocity measures display changes in CBFV between and during uterine contractions. RESULTS:Good quality recordings during and between contractions were achieved in 16/25 fetuses. In twelve fetuses, CBFV measures were stable during uterine contractions. Four fetuses showed patterns of reduced CBFV velocity measures during contractions. CONCLUSIONS:Continuous fetal CBFV monitoring by VisiBeam was feasible in 64 % of the subjects during labor. The system displayed variations of fetal CBFV not available by today's monitoring techniques and motivates for further studies. However, improvement of the probe attachment is required to ensure good quality signal in a higher proportion of fetuses during labor.

Background: General anaesthesia is associated with neurocognitive deficits in infants after noncardiac surgery. Disturbances in cerebral perfusion as a result of systemic hypotension and impaired autoregulation may be a potential cause. Our aim was to study cerebral blood flow (CBF) velocity continuously during general anaesthesia in infants undergoing noncardiac surgery and compare variations in CBF velocity with simultaneously measured near-infrared spectroscopy (NIRS), blood pressure, and heart rate. Methods: NeoDoppler, a recently developed ultrasound system, was used to monitor CBF velocity via the anterior fontanelle during induction and maintenance of general anaesthesia until the start of surgery, and during recovery. NIRS, blood pressure, and heart rate were monitored simultaneously and synchronised with the NeoDoppler measurements. Results: Thirty infants, with a median postmenstrual age at surgery of 37.6 weeks (range 28.6e60.0) were included. Compared with baseline, the trend curves showed a decrease in CBF velocity during induction and maintenance of anaesthesia and returned to baseline values during recovery. End-diastolic velocity decreased in all infants during anaesthesia, on average by 59%, whereas peak systolic-and time-averaged velocities decreased by 26% and 45%, respectively. In comparison, the reduction in mean arterial pressure was only 20%. NIRS values were high and remained stable. When adjusting for mean arterial pressure, the significant decrease in end-diastolic velocity persisted, whereas there was only a small reduction in peak systolic velocity. Conclusions: Continuous monitoring of CBF velocity using NeoDoppler during anaesthesia is feasible and may provide valuable information about cerebral perfusion contributing to a more targeted haemodynamic management in anaesthetised infants.

Valve regurgitation is a cardiac condition caused by the incomplete closure of a cardiac valve. Untreated, this condition may result in cardiac failure. Regular monitoring of this condition is essential in guiding the decision process for surgical intervention. Current guidelines recommend a multi-parametric assessment of valve regurgitation using echocardiography, which is both time consuming and heavily dependent on the experience of the examiner. Several methods have been proposed to provide quantitative markers to facilitate the assessment of valve regurgitation, most notably the Proximal Isovelocity Surface Area (PISA) method and methods based on the quantification of the total Regurgitant Volume (RVol) from the power of backscattered blood signal. In this work, we propose a framework based on trans-thoracic 3-D high frame-rate acquisitions for the simultaneous estimation of the jet cross-sectional area and jet velocity directly at the jet core, which are then combined to estimate the instantaneous flow rate and RVol patients with aortic or mitral insufficiency. We compare two methods for the segmentation of the jet cross-sectional area from the power Doppler signal. Validation on simulated data indicates good segmentation accuracy for the best method ( $\beta $ = 0.97, ${R}^{{2}}$ = 0.91). Validation on recordings from a flow phantom shows good agreement ( $\beta $ = 1.2, ${R}^{{2}}$ = 0.88) with an external flow rate meter. Clinical feasibility of the method is also shown in a patient with mitral regurgitation.

Cerebral Doppler ultrasound has been an important tool in pediatric diagnostics and prognostics for decades. Although the Doppler spectrum can provide detailed information on cerebral perfusion, the measured spectrum is often reduced to simple numerical parameters. To help pediatric clinicians recognize the visual characteristics of disease-associated Doppler spectra and identify possible areas for future research, a scoping review of primary studies on cerebral Doppler arterial waveforms in infants was performed. A systematic search in three online bibliographic databases yielded 4898 unique records. Among these, 179 studies included cerebral Doppler spectra for at least five infants below 1 y of age. The studies describe variations in the cerebral waveforms related to physiological changes (43%), pathology (62%) and medical interventions (40%). Characteristics were typically reported as resistance index (64%), peak systolic velocity (43%) or end-diastolic velocity (39%). Most studies focused on the anterior (59%) and middle (42%) cerebral arteries. Our review highlights the need for a more standardized terminology to describe cerebral velocity waveforms and for precise definitions of Doppler parameters. We provide a list of reporting variables that may facilitate unambiguous reports. Future studies may gain from combining multiple Doppler parameters to use more of the information encoded in the Doppler spectrum, investigating the full spectrum itself and using the possibilities for long-term monitoring with Doppler ultrasound.

Background/Purpose: Pulse palpation is an unreliable method for diagnosing cardiac arrest. To address this limitation, continuous hemodynamic monitoring may be a viable solution. Therefore, we developed a novel, hands-free Doppler system, RescueDoppler, to detect the pulse continuously in the carotid artery. Methods: In twelve pigs, we evaluated RescueDoppler ' s potential to measure blood flow velocity in three situations where pulse palpation of the carotid artery was insufficient: (1) systolic blood pressure below 60 mmHg, (2) ventricular fibrillation (VF) and (3) pulseless electrical activity (PEA). (1) Low blood pressure was induced using a Fogarty balloon catheter to occlude the inferior vena cava. (2) An implantable cardioverter-defibrillator induced VF. (3) Myocardial infarction after microembolization of the left coronary artery caused True-PEA. Invasive blood pressure was measured in the contralateral carotid artery. Time-averaged blood flow velocity (TAV) in the carotid artery was related to mean arterial pressure (MAP) in a linear mixed model. Results: RescueDoppler identified pulsatile blood flow in 41/41 events with systolic blood pressure below 60 mmHg, with lowest blood pressure of 19 mmHg. In addition the absence of spontaneous circulation was identified in 21/21 VF events and true PEA in 2/2 events. The intraclass correlation coefficient within animals for TAV and MAP was 0.94 (95% CI. 0.85-0.98). Conclusions: In a porcine model, RescueDoppler reliably identified pulsative blood flow with blood pressures below 60 mmHg. During VF and PEA, circulatory arrest was rapidly and accurately demonstrated. RescueDoppler could potentially replace unreliable pulse palpation during cardiac arrest and cardiopulmonary resuscitation.

There is a risk of gaseous and solid micro-embolus formation during transcatheter cardiac interventions and surgery in children with congenital heart disease (CHD). Our aim was to study the burden of high intensity transient signals (HITS) during these procedures in infants. We used a novel color M-mode Doppler (CMD) technique by NeoDoppler, a non-invasive ultrasound system based on plane wave transmissions for transfontanellar continuous monitoring of cerebral blood flow in infants. The system displays CMD with 24 sample volumes and a Doppler spectrogram. Infants with CHD undergoing transcatheter interventions (n = 15) and surgery (n = 13) were included. HITS were manually detected based on an "embolic signature " in the CMD with corresponding intensity increase in the Doppler spectrogram. Embolus-to-blood ratio (EBR) defined HITS size. A total of 1169 HITS with a median EBR of 9.74 dB (interquartile range [IQR]: 5.10-15.80 dB) were detected. The median number of HITS in the surgery group was 45 (IQR: 11-150), while in the transcatheter group the median number was 12 (IQR: 7-24). During cardiac surgery, the highest number of HITS per hour was seen from initiation of cardiopulmonary bypass to aortic X-clamp. In this study we detected frequent HITS and determined the feasibility of using NeoDoppler monitoring for HITS detection. (C) 2022 The Author(s). Published by Elsevier Inc. on behalf of World Federation for Ultrasound in Medicine & Biology. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

BackgroundA cerebroprotective effect of low frequency oscillations (LFO) in cerebral blood flow (CBF) has been suggested in adults, but its significance in neonates is not known. This observational study evaluates normal arterial and venous cerebral blood flow in healthy neonates using NeoDoppler, a novel Doppler ultrasound system which can measure cerebral hemodynamics continuously.MethodUltrasound Doppler data was collected for 2 h on the first and second day of life in 36 healthy term born neonates. LFO (0.04–0.15 Hz) were extracted from the velocity curve by a bandpass filter. An angle independent LFO index was calculated as the coefficient of variation of the filtered curve. Separate analyses were done for arterial and venous signals, and results were related to postnatal age and behavioral state (asleep or awake).ResultsThe paper describes normal physiologic variations of arterial and venous cerebral hemodynamics. Mean (SD) arterial and venous LFO indices (%) were 6.52 (2.55) and 3.91 (2.54) on day one, and 5.60 (1.86) and 3.32 (2.03) on day two. After adjusting for possible confounding factors, the arterial LFO index was estimated to decrease by 0.92 percent points per postnatal day (p < 0.001). The venous LFO index did not change significantly with postnatal age (p = 0.539). Arterial and venous LFO were not notably influenced by behavioral state.ConclusionThe results indicate that arterial LFO decrease during the first 2 days of life in healthy neonates. This decrease most likely represents normal physiological changes related to the transitional period. A similar decrease for venous LFO was not found.