Matthias Borowski

Medical device alarms

Abstract The high number of false positive alarms has long been known to be a serious problem in critical care medicine – yet it remains unresolved. At the same time, threats to patient safety due to missing or suppressed alarms are being reported. The purpose of this paper is to present results from a workshop titled “Too many alarms? Too few alarms?” organized by the Section Patient Monitoring and the Workgroup Alarms of the German Association of Biomedical Engineering of the Association for Electrical, Electronic and Information Technologies. The current situation regarding alarms and their problems in intensive care, such as lack of clinical relevance, alarm fatigue, workload increases due to clinically irrelevant alarms, usability problems in alarm systems, problems with manuals and training, and missing alarms due to operator error are outlined, followed by a discussion of solutions and strategies to improve the current situation. Finally, the need for more research and development, focusing on signal quality considerations, networking of medical devices at the bedside, diagnostic alarms and predictive warnings, usability of alarm systems, education of healthcare providers, creation of annotated clinical databases for testing, standardization efforts, and patient monitoring in the regular ward, are called for.

Current practice of first-line treatment strategies in patients with critical limb ischemia.

OBJECTIVE Critical limb ischemia (CLI) is growing in global prevalence and is associated with high rates of limb loss and mortality. However, a relevant gap of evidence about the most optimal treatment strategy still exists. The aim of this study of the prospective, multicenter First-Line Treatments in Patients With Critical Limb Ischemia (CRITISCH) registry was to assess the current practice of all first-line treatments strategies in CLI patients in German vascular centers. METHODS Between January 2013 and September 2014, five first-line treatment strategies-endovascular revascularization (ER), bypass surgery (BS), femoral/profundal artery patchplasty (FAP), conservative treatment, and primary amputation-were determined among CLI patients in 27 vascular tertiary centers. The main composite end point was major amputation or death, or both, during the hospital stay. Secondary outcomes were hemodynamic failure, major adverse cardiovascular and cerebral events, and reintervention. Univariate logistic models were additionally built to preselect possible risk factors for either event, which were then used as candidates for a multivariate logistic model. RESULTS The study included 1200 consecutive patients. First-line treatment of choice was ER in 642 patients (53.4%), BS in 284 (23.7%), FAP in 126 (10.5%), conservative treatment in 118 (9.8%), and primary amputation in 30 (2.5%). The composite end point was met in 24 patients (4%) after ER, in 17 (6%) after BS, in 8 (6%) after FAP, and in 9 (8%) after conservative treatment (P = .172). The highest rate of in-hospital death was observed after primary amputation (10%) and of hemodynamic failure after conservative treatment (91%). Major adverse cardiovascular and cerebral events developed in 4% of patients after ER, in 5% after BS, in 6% after FAP, in 5% after conservative treatment, and in 13% after primary amputation. The reintervention rate was 8%, 14%, 6%, 5%, and 3% in each group, respectively. In the multivariate regression model, coronary artery disease (odds ratio [OR], 2.96; 95% confidence interval [CI], 1.42-6.17) and previous myocardial infarction (PMI) <6 months (OR, 3.67, 95% CI, 1.51-8.88) were identified as risk factors for the composite end point. Risk factors for amputation were dialysis (OR, 3.31, 95% CI, 1.44-7.58) and PMI (OR, 3.26, 95% CI, 1.23-8.36) and for death, BS compared with ER (OR, 3.32; 95% CI, 1.10-10.0), renal insufficiency without dialysis (OR, 6.34; 95% CI, 1.71-23.5), and PMI (OR, 7.41; 95% CI, 2.11-26.0). CONCLUSIONS The CRITISCH registry revealed ER as the most common first-line approach in CLI patients. Coronary artery disease and PMI <6 months were independent risk factors for the composite end point. Special attention should be also paid to CLI patients with renal insufficiency, with or without dialysis, and those undergoing BS.

Rapid Phenotypic Detection of Microbial Resistance in Gram-Positive Bacteria by a Real-Time Laser Scattering Method†

We developed a methodology for antimicrobial susceptibility testing (AST) based on the BacterioScanTM216R laser scattering technology, using methicillin resistance in Staphylococcus aureus and vancomycin resistance in enterococci as exemplar for important resistance phenotypes. Fifty methicillin-resistant (MRSA) and 50 methicillin-susceptible (MSSA) S. aureus, as well as 50 vancomycin-resistant enterococci (VRE) and 50 vancomycin-susceptible enterococci (VSE) isolates were used for the study. Optimal test conditions were derived by investigating the effects of inoculum size, medium, incubation temperature and broth filtration. We proposed four different statistical approaches for rapid discrimination between resistant and susceptible bacteria. The statistical approach based on raw measurements of bacterial concentrations delivered sensitivity of 100% and specificity of 94% for discrimination between MRSA and MSSA already after 3 hours of incubation. Categorical agreement of ≥90% was achieved after 140 min with this approach. Differentiation between VRE and VSE was possible with 98% sensitivity and 92% specificity after 3 hours, using a sophisticated statistical approach based on concentration slopes derived from the raw concentration measurements. This approach provided categorical agreement of ≥90% after 165 min. The sensitivity and specificity estimates were confirmed by leave-one-out cross validation. In conclusion, the phenotypic AST methods developed in this study are promising for rapid detection of MRSA and VRE. The development and application of this technology would allow early detection of the resistant pathogens, thus facilitating swift change to the targeted antimicrobial treatment as well as timely initiation of appropriate infection control measures. Further studies are warranted to validate this approach for the detection of other resistance phenotypes, including direct testing from clinical specimens.

Predicting ROSC in out-of-hospital cardiac arrest using expiratory carbon dioxide concentration: Is trend-detection instead of absolute threshold values the key?

AIM Guidelines recommend detecting return of spontaneous circulation (ROSC) by a rising concentration of carbon dioxide in the exhalation air. As CO2 is influenced by numerous factors, no absolute cut-off values of CO2 to detect ROSC are agreed on so far. As trends in CO2 might be less affected by influencing factors, we investigated an approach which is based on detecting CO2-trends in real-time. METHODS We conducted a retrospective case-control study on 169 CO2 time series from out of hospital cardiac arrests resuscitated by Muenster City Ambulance-Service, Germany. A recently developed statistical method for real-time trend-detection (SCARM) was applied to each time series. For each series, the percentage of time points with detected positive and negative trends was determined. RESULTS ROSC time series had larger percentages of positive trends than No-ROSC time series (p=0.003). The median percentage of positive trends was 15% in the ROSC time series (IQR: 5% to 23%) and 7% in the No-ROSC time series (IQR: 3% to 14%). A receiver operating characteristic (ROC) analysis yielded an optimal threshold of 13% to differentiate between ROSC and No-ROSC cases with a specificity of 58.4% and sensitivity of 73.9%; the area under the curve was 63.5%. CONCLUSION Patients with ROSC differed from patients without ROSC as to the percentage of detected CO2 trends, indicating the potential of our real-time trend-detection approach. Since the study was designed as a proof of principle and its calculated specificity and sensitivity are low, more research is required to implement CO2-trend-detection into clinical use.

On- and offline detection of structural breaks in thermal spraying processes

We investigate and develop methods for structural break detection, considering time series from thermal spraying process monitoring. Since engineers induce technical malfunctions during the processes, the time series exhibit structural breaks at known time points, giving us valuable information to conduct the investigations. First, we consider a recently developed robust online (also real-time) filtering (i.e. smoothing) procedure that comprises a test for local linearity. This test rejects when jumps and trend changes are present, so that it can also be useful to detect such structural breaks online. Second, based on the filtering procedure we develop a robust method for the online detection of ongoing trends. We investigate these two methods as to the online detection of structural breaks by simulations and applications to the time series from the manipulated spraying processes. Third, we consider a recently developed fluctuation test for constant variances that can be applied offline, i.e. after the whole time series has been observed, to control the spraying results. Since this test is not reliable when jumps are present in the time series, we suggest data transformation based on filtering and demonstrate that this transformation makes the test applicable.

Association between statin therapy and amputation-free survival in patients with critical limb ischemia in the CRITISCH registry

Objective Secondary prevention in patients with critical limb ischemia (CLI) is crucial for the reduction of cardiovascular morbidity and mortality. Nonetheless, current recommendations are extrapolated from other high‐risk populations because of the lack of CLI‐dedicated trials. The aim of this explorative study was to evaluate the association of statin therapy with the outcomes of CLI patients. Methods The First‐Line Treatments in Patients With Critical Limb Ischemia (CRITISCH) registry is a prospective multicenter registry analyzing the effectiveness of all available treatment strategies in 1200 CLI patients. For the purposes of this analysis, patients were divided into two groups based on statin administration. Treatment crossovers and nonadherent patients were excluded from analysis. The primary composite end point of this study was the amputation‐free survival (AFS). Major adverse cardiovascular and cerebral events (MACCEs), time to death, and time to major amputation were also analyzed. Results Statin therapy was applied in 445 individuals (37%), 371 (31%) patients received no statins, and 384 subjects were excluded from analysis (treatment crossovers). Patients receiving statins were more likely to be younger (P < .001) and to have a history of coronary heart disease (P < .001) or previous intervention at index limb (P < .001). Patients receiving statin therapy had a lower hazard regarding AFS (hazard ratio [HR], 0.45; 95% confidence interval [CI], 0.34‐0.63; P < .001) and death (HR, 0.40; 95% CI, 0.24‐0.66; P < .001) as well as lower odds of MACCE (odds ratio, 0.41; 95% CI, 0.23‐0.69; P = .001). However, statin therapy was not associated with reduced amputation rates (HR, 1.02; 95% CI, 0.67‐1.56; P = .922). Statin effect on AFS was consistent among diabetics (HR, 0.47; 95% CI, 0.31‐0.70; P < .001), patients with chronic kidney disease (HR, 0.53; 95% CI, 0.32‐0.87; P = .012), and patients older than 75 years (HR, 0.40; 95% CI, 0.26‐0.60; P < .001). Statin administration was also associated with an improved AFS in patients with antiplatelet medication (HR, 0.64; 95% CI, 0.41‐0.99; P = .049) and without antiplatelet medication (HR, 0.26; 95% CI, 0.12‐0.57; P = .001) and after both endovascular therapy (HR, 0.51; 95% CI, 0.34‐0.76; P = .001) and bypass revascularization (HR, 0.38; 95% CI, 0.21‐0.68; P = .001). Conclusions Statin therapy in CLI patients is associated with an increased AFS and lower rates of mortality and MACCEs without improving, however, the salvage rates of the affected limb.

Assessment of the Fetal Cerebral Artery: Importance of Doppler Preset Settings

The Doppler assessment of the middle cerebral artery (MCA) has a central role in the monitoring of high‐risk pregnancies. The objective of this study was to investigate the importance of Doppler preset settings for measurement of the peak systolic velocity (PSV) and pulsatility index (PI) of the MCA.

One-Year Results of First-Line Treatment Strategies in Patients With Critical Limb Ischemia (CRITISCH Registry):

Purpose: To examine the outcomes of all first-line strategies for the treatment of critical limb ischemia (CLI), identify factors that influenced the treatment choice, and determine the risk of amputation or death after each treatment. Methods: CRITISCH (ClinicalTrials.gov identifier NCT01877252) is a multicenter, national, prospective registry evaluating all available treatment strategies applied in 1200 consecutive CLI patients in 27 vascular centers in Germany. The recruitment started in January 2013 and was completed in September 2014. Treatment options were endovascular revascularization (642, 53.5%), bypass surgery (284, 23.7%), femoral artery patchplasty (126, 10.5%) with or without concomitant peripheral intervention, conservative treatment (118, 9.8%), and primary major amputation (30, 2.5%). The primary endpoint of this study was amputation-free survival (AFS). The Society of Vascular Surgery’s suggested objective performance goal (OPG) for AFS (71%) was used as the effectiveness criterion. Multivariable regression methods were employed to identify variables that influenced the treatment selection and AFS after each treatment; results are presented as the hazard ratio (HR) and 95% confidence interval (CI). Results: The 12-month AFS estimates following endovascular therapy, bypass grafting, femoral patchplasty, and conservative treatment were 75%, 72%, 73%, and 72%, respectively. Factors influencing treatment choice were age, chronic kidney disease (CKD), diabetes, smoking, prior vascular procedures in the index leg, TransAtlantic Inter-Society Consensus II C/D lesions, and absence of runoff vessels. Cox regression analysis identified CKD (HR 2.07, 95% CI 1.26 to 3.41, p=0.004), the use of a prosthetic bypass conduit (HR 1.97, 95% CI 1.23 to 3.14, p=0.004), and previous vascular intervention in the index limb (HR 1.52, 95% CI 0.94 to 2.43, p=0.085) as independent risk factors for diminished AFS after bypass surgery. CKD (HR 1.47, 95% CI 1.09 to 1.99, p=0.012) and Rutherford category 6 (HR 1.81, 95% CI 1.30 to 2.52, p<0.001) compromised the performance of endovascular revascularization. Conclusion: CRITISCH registry data revealed that all first-line treatment strategies selected and indicated by the treating physicians met the suggested OPGs. CKD was an important determinant of patient prognosis after treatment regardless of the revascularization method.

Direct determination of carbapenem-resistant enterobacteriaceae and pseudomonas aeruginosa from positive blood cultures using laser scattering technology

Delays in appropriate antimicrobial treatment contribute to increased mortality of septic patients. We aimed to develop a methodology for detection of carbapenem resistance in Gram-negative bacteria directly from positive blood cultures (BCs). Initially, meropenem-resistant Enterobacteriaceae (n = 13) and Pseudomonas aeruginosa (n = 32) isolates as well as the same numbers of meropenem-susceptible isolates were used to establish the detection of carbapenem resistance from agar cultures. Growth-based phenotypic detection of meropenem resistance was performed by a laser scattering (LS) method using a BacterioScan™216R instrument. A subset of the strain collection consisting of meropenem-susceptible and -resistant isolates (each comprising seven P. aeruginosa and three Klebsiella pneumoniae) was used for determination of carbapenem resistance directly from positive BCs. Lysis/centrifugation and filtration/dilution methods were investigated for processing of positive BCs. Four different statistical approaches to discriminate between susceptible and resistant bacteria in real-time were applied and were compared regarding their sensitivity and specificity. After 3 h and 4 h of incubation, respectively, detection of carbapenem resistance in Enterobacteriaceae (sensitivity, 100%; specificity, 100%) and P. aeruginosa (sensitivity, 100%; specificity, ≥90%) agar cultures was attainable. Detection of carbapenem resistance directly from positive BCs was achievable with 100% sensitivity and 100% specificity after 4 h and 5 h, respectively, applying lysis/centrifugation and filtration/dilution methods. In conclusion, LS technology combined with lysis/centrifugation and appropriate statistical real-time analyses represents a promising option for rapid detection of carbapenem resistance in Gram-negative rods directly from positive BCs.

Robust online-surveillance of trend-coherence in multivariate data streams: the similar trend monitoring (STM) procedure

When several data streams are observed simultaneously, it is often of great interest to monitor the coherences between all pairs of streams. We propose a new technique called Similar Trend Monitoring (STM) for this task: The current slopes of all univariate streams are estimated and compared pairwise at each time point. The STM statistic is the standardized slope difference, so that decisions about coherence can be made by means of the six-sigma-rule, for instance. The STM meets the high demands that come along with the online monitoring of multivariate data streams: it is fast to compute, robust against outliers, applicable when observations are missing, and does not require stationarity of the processes. We investigate the distribution and the performance of the STM and demonstrate its capabilities considering blood pressure time series from intensive care patient monitoring as an example.