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Background

A major barrier to the analysis of ventilation waveform data collected during CPR is the presence of artefacts caused by chest compressions. This study describes the development and evaluation of an algorithm to extract parameters regarding ventilation volume, pressure, and frequency from pneumotachography waveform data collected during ongoing simulated CPR.

Method

Ventilation waveform data was collected from a pneumotachograph connected to the respiratory circuit of a ventilator and a test lung. Both regular ventilation and ventilation during simulated CPR were used to develop the algorithm. A grid search was employed to optimize the algorithm parameters compared to the ventilator settings. The parameters were then manually tuned using clinical data from ventilation during CPR. The performance of the algorithm was described in terms of the median error vs. the known ventilator settings in the simulated data.

Results

Compared to the ventilator settings, the largest systematic errors of the algorithm was an overestimation of peak pressures during asynchronous CPR (median error of 3 (IQR 0.3–5.8) cmH₂O), and an underestimation of inspiratory volumes during synchronous CPR (median error 46 (IQR −76 to 10) ml).

Conclusion

In an experimental setting, the developed algorithm provides a novel solution to measure ventilation parameters during ongoing chest compressions. The algorithm is freely available under an open-source licence for use and further development. Further studies will be needed to validate the algorithm.

UNLABELLED: Accurate evaluation of kidney function is vital in the pediatric intensive care unit (PICU), where even small changes in cystatin C and creatinine concentrations can affect clinical decision-making. Diurnal patterns in renal biomarkers have been reported in adults, but their relevance in critically ill children remains unclear. Understanding whether sampling time contributes to biological variability is essential for reliable interpretation of kidney function tests. This retrospective study included 8619 cystatin C and 9314 creatinine results collected in a tertiary PICU between April 2014 and September 2025. The hourly distribution of sampling and hourly biomarker percentiles (0.10, 0.25, and 0.50) were evaluated across the 24-h cycle. Diurnal variation was quantified using coefficients of variation (CVs). Sampling was strongly clustered in the early morning, with 38.6% of cystatin C and 37.4% of creatinine samples drawn at 5:00-5:59 AM. The 0.10-0.50 percentiles of cystatin C showed minimal diurnal variation (CV 4.5-6.3%). Creatinine exhibited slightly greater variability, with CVs of 7.4-11.6% across the same percentiles. Median creatinine was significantly higher in the afternoon/evening than in the early morning, while cystatin C showed no clinically relevant hourly fluctuations.

CONCLUSION: In critically ill children, cystatin C demonstrates limited diurnal variation, while creatinine shows modest but measurable fluctuations across the 24-h period. These findings suggest that cystatin C is relatively robust to sampling time in the PICU, whereas creatinine may vary enough to influence interpretation in borderline cases. Incorporating knowledge of sampling time may improve the accuracy of kidney function assessment and AKI classification in pediatric critical care.

WHAT IS KNOWN: • Creatinine and cystatin C can show biological and circadian variability in adults and older children, with creatinine generally exhibiting greater within-day fluctuation than cystatin C.

WHAT IS NEW: • In critically ill children, cystatin C shows minimal diurnal variation, whereas creatinine displays modest but measurable time-of-day-related increases, indicating that sampling time may influence creatinine interpretation but not cystatin C in the PICU setting.

Background 

Resource Constrained Situations (RCS) at Emergency Medical Dispatch centers where there are more patients requiring an ambulance than there are available ambulances are common. Machine Learning (ML) techniques offer a promising but largely untested approach to assessing relative risks among these patients. The study aims to establish whether the provision of ML-based risk scores predicting patient outcomes improves the ability of dispatchers to identify patients at high risk for deterioration in RCS and dispatch the first available ambulance to them.

Methods and findings 

We performed a parallel-group, randomized trial of adult patients assessed by a dispatch nurse at two study sites in Sweden as requiring a low-priority ambulance response in RCS. Patients were randomized 1:1 to be prioritized with the aid of an ML-based risk assessment tool, or per current clinical practice. The primary outcome was defined in terms of whether the first available ambulance was sent to the patient with the highest National Early Warning Score (NEWS 2) based on subsequently collected vital signs. A total of 1,245 RCS were included in the study. In the intervention arm, 68.3% of RCS were assessed correctly per the primary outcome versus 62.5% in the control group, corresponding to an odds ratio of 1.28 (95% CI [1.00, 1.63], p = 0.047). This study was limited to only patients determined to require a low-priority ambulance response in two Swedish regions, and was underpowered for the primary outcome due to a smaller than expected sample size.

Conclusion 

This study suggests that clinical ML-based decision support tools may have the ability to influence care provider decisions and improve their capacity to rapidly differentiate between high- and low-risk patients at dispatch. Further research should establish the suitability of these tools in larger cohorts, for patients with both higher- and lower-levels of priority, and in other settings. The trial was registered at ClinicalTrials.gov (NCT04757194).

BACKGROUND: The aim of this experimental study was to elucidate whether different distances between central venous catheter tips can affect drug clearance during continuous renal replacement therapy (CRRT). Central venous catheters (CVCs) are widely used in intensive care patients for drug infusion. If a patient receives CRRT, a second central dialysis catheter (CDC) is required. Where to insert CVCs is directed by guidelines, but recommendations regarding how to place multiple catheters are scarce. There are indications that a drug infused in a CVC with the tip close to the tip of the CDC, could be directly aspirated into the dialysis machine, with a risk of increased clearance. However, studies on whether clearance is affected by different CVC and CDC tip positions, when the two catheters are in the same vessel, are few.

METHODS: In this model with 18 piglets, gentamicin (GM) and vancomycin (VM) were infused through a CVC during CRRT. The CVC tip was placed in different positions in relation to the CDC tip from caudal, i.e., proximal to the heart, to cranial, i.e., distal to the heart. Serum and dialysate concentrations were sampled after approximately 30 min of CRRT at four different positions: when the CVC tip was 2 cm caudally (+ 2), at the same level (0), and at 2 (- 2) and 4 (- 4) cm cranially of the tip of the CDC. Clearance was calculated. A mixed linear model was performed, and level of significance was set to p < 0.05.

RESULTS: Clearance of GM had median values at + 2 cm, 0 cm, - 2 cm and - 4 cm of 17.3 (5.2), 18.6 (7.4), 20.0 (16.2) and 26.2 (12.2) ml/min, respectively (p = 0.04). Clearance of VM had median values at + 2 cm, 0 cm, - 2 cm and - 4 cm of 16.2 (4.5), 14.7 (4.9), 19.0 (10.2) and 21.2 (11.4) ml/min, respectively (p = 0.02).

CONCLUSIONS: The distance between CVC and CDC tips can affect drug clearance during CRRT. A cranial versus a caudal tip position of the CVC in relation to the tip of the CDC led to the highest clearance.

BACKGROUND: Ventilation during cardiopulmonary resuscitation (CPR) has long been a part of the standard treatment during cardiac arrests. Ventilation is usually given either during continuous chest compressions (CCC) or during a short pause after every 30 chest compressions (30:2). There is limited knowledge of how ventilation is delivered if it effects the hemodynamics and if it plays a role in the occurrence of lung injuries. The aim of this study was to compare ventilation parameters, hemodynamics, blood gases and lung injuries during experimental CPR given with CCC and 30:2 in a porcine model.

METHODS: Sixteen pigs weighing approximately 33 kg were randomized to either receive CPR with CCC or 30:2. Ventricular fibrillation was induced by passing an electrical current through the heart. CPR was started after 3 min and given for 20 min. Chest compressions were provided mechanically with a chest compression device and ventilations were delivered manually with a self-inflating bag and 12 l/min of oxygen. During the experiment, ventilation parameters and hemodynamics were sampled continuously, and arterial blood gases were taken every five minutes. After euthanasia and cessation of CPR, the lungs and heart were removed in block and visually examined followed by sampling of lung tissue which were examined using microscopy.

RESULTS: In the CCC group and the 30:2 group, peak inspiratory pressure (PIP) was 58.6 and 35.1 cmH₂O (p < 0.001), minute volume (MV) 2189.6 and 1267.1 ml (p < 0.001), peak expired carbon dioxide (PECO₂) 28.6 and 39.4 mmHg (p = 0.020), partial pressure of carbon dioxide (PaCO₂) 50.2 and 61.1 mmHg (p = 0.013) and pH 7.3 and 7.2 (p = 0.029), respectively. Central venous pressure (CVP) decreased more over time in the 30:2 group (p = 0.023). All lungs were injured, but there were no differences between the groups.

CONCLUSIONS: Ventilation during CCC resulted in a higher PIP, MV and pH and lower PECO₂ and PaCO₂, showing that ventilation mode during CPR can affect ventilation parameters and blood gases.

BACKGROUND: In intensive care, different central venous catheters (CVC) are often used for infusion of drugs. If a patient is treated with continuous renal replacement therapy (CRRT) a second catheter, a central venous dialysis catheter (CVDC), is needed. Placing the catheters close together might pose a risk that a drug infused in a CVC could be directly aspirated into a CRRT machine and cleared from the blood without giving the effect intended. The purpose of this study was to elucidate if drug clearance is affected by different catheter placement, during CRRT. In this endotoxaemic animal model, an infusion of antibiotics was administered in a CVC placed in the external jugular vein (EJV). Antibiotic clearance was compared, whether CRRT was through a CVDC placed in the same EJV, or in a femoral vein (FV). To reach a target mean arterial pressure (MAP), noradrenaline was infused through the CVC and the dose was compared between the CDVDs.

RESULTS: The main finding in this study was that clearance of antibiotics was higher when both catheter tips were in the EJV, close together, compared to in different vessels, during CRRT. The clearance of gentamicin was 21.0 ± 7.3 vs 15.5 ± 4.2 mL/min (p 0.006) and vancomycin 19.3 ± 4.9 vs 15.8 ± 7.1 mL/min (p 0.021). The noradrenaline dose to maintain a target MAP also showed greater variance with both catheters in the EJV, compared to when catheters were placed in different vessels.

CONCLUSION: The results in this study indicate that close placement of central venous catheter tips could lead to unreliable drug concentration, due to direct aspiration, during CRRT.

Introduction: The presented study aimed to investigate whether a mechanical chest compression piston device with a suction cup assisting chest recoil could impact the hemodynamic status when compared to a bare piston during cardiopulmonary resuscitation.

Methods: 16 piglets were anesthetized and randomized into 2 groups. After 3 minutes of induced ventricular fibrillation, a LUCAS 3 device was used to perform chest compressions, in one group a suction cup was mounted on the device's piston, while in the other group, compressions were per -formed by the bare piston. The device was used in 30:2 mode and the animals were manually ventilated. Endpoints of the study were: end tidal carbon dioxide, coronary and cerebral perfusion pressures, and brain oxygenation (measured using near infrared spectroscopy). At the end of the protocol, the animals that got a return to spontaneous circulation were observed for 60 minutes, then euthanized.

Results: No difference was found in end tidal carbon dioxide or tidal volumes. Coronary perfusion pressure and cerebral oxygenation were higher in the Suction cup group over the entire experiment time, while cerebral perfusion pressure was higher only in the last 5 minutes of CPR. A passive tidal volume (air going in and out the airways during compressions) was detected and found correlated to end tidal carbon dioxide.

Conclusions: The use of a suction cup on a piston-based chest compression device did not increase end tidal carbon dioxide, but it was associated to a higher coronary perfusion pressure.

Background The COVID-19 pandemic has presented emergency medical services (EMS) worldwide with the difficult task of identifying patients with COVID-19 and predicting the severity of their illness. The aim of this study was to investigate whether physiological respiratory parameters in pre-hospital patients with COVID-19 differed from those without COVID-19 and if they could be used to aid EMS personnel in the prediction of illness severity. Methods Patients with suspected COVID-19 were included by EMS personnel in Uppsala, Sweden. A portable respiratory monitor based on pneumotachography was used to sample the included patient's physiological respiratory parameters. A questionnaire with information about present symptoms and background data was completed. COVID-19 diagnoses and hospital admissions were gathered from the electronic medical record system. The physiological respiratory parameters of patients with and without COVID-19 were then analyzed using descriptive statistical analysis and logistic regression. Results Between May 2020 and January 2021, 95 patients were included, and their physiological respiratory parameters analyzed. Of these patients, 53 had COVID-19. Using adjusted logistic regression, the odds of having COVID-19 increased with respiratory rate (95% CI 1.000-1.118), tidal volume (95% CI 0.996-0.999) and negative inspiratory pressure (95% CI 1.017-1.152). Patients admitted to hospital had higher respiratory rates (p<0.001) and lower tidal volume (p = 0.010) compared to the patients who were not admitted. Using adjusted logistic regression, the odds of hospital admission increased with respiratory rate (95% CI 1.081-1.324), rapid shallow breathing index (95% CI 1.006-1.040) and dead space percentage of tidal volume (95% CI 1.027-1.159). Conclusion Patients taking smaller, faster breaths with less pressure had higher odds of having COVID-19 in this study. Smaller, faster breaths and higher dead space percentage also increased the odds of hospital admission. Physiological respiratory parameters could be a useful tool in detecting COVID-19 and predicting hospital admissions, although more research is needed.

BACKGROUND: The novel coronavirus disease 2019 (Covid-19) pandemic has affected prehospital care systems across the world, but the prehospital presentation of affected patients and the extent to which prehospital care providers are able to identify them is not well characterized. In this study, we describe the presentation of Covid-19 patients in a Swedish prehospital care system, and asses the predictive value of Covid-19 suspicion as documented by dispatch and ambulance nurses.

METHODS: Data for all patients with dispatch, ambulance, and hospital records between January 1-August 31, 2020 were extracted. A descriptive statistical analysis of patients with and without hospital-confirmed Covid-19 was performed. In a subset of records beginning from April 14, we assessed the sensitivity and specificity of documented Covid-19 suspicion in dispatch and ambulance patient care records.

RESULTS: A total of 11,894 prehospital records were included, of which 481 had a primary hospital diagnosis code related to-, or positive test results for Covid-19. Covid-19-positive patients had considerably worse outcomes than patients with negative test results, with 30-day mortality rates of 24% vs 11%, but lower levels of prehospital acuity (e.g. emergent transport rates of 14% vs 22%). About half (46%) of Covid-19-positive patients presented to dispatchers with primary complaints typically associated with Covid-19. Six thousand seven hundred seventy-six records were included in the assessment of predictive value. Sensitivity was 76% (95% CI 71-80) and 82% (78-86) for dispatch and ambulance suspicion respectively, while specificities were 86% (85-87) and 78% (77-79).

CONCLUSIONS: While prehospital suspicion was strongly indicative of hospital-confirmed Covid-19, based on the sensitivity identified in this study, prehospital suspicion should not be relied upon as a single factor to rule out the need for isolation precautions. The data provided may be used to develop improved guidelines for identifying Covid-19 patients in the prehospital setting.

Introduction: The relations between specific ECG patterns and coronary angiographic findings in cardiac arrest patients with different comorbidities are not properly assessed. More evidence is needed to identify patients with the highest risk for acute coronary artery disease as a cause of the cardiac arrest. This study aims to describe the coronary artery findings after cardiac arrest in relation to ECG and comorbidity.

Method: A retrospective study of out-of-hospital cardiac arrest patients, with coronary angiography performed within 28 days. ECG on admission, comorbidity, PCI attempts and angiographic findings are described. Data were retrieved from national registries in Sweden.

Results: Among 1133 patients with available ECG and angiography information the mean age was 64 years. The rate of shockable rhythm was 79 degrees 0. The total incidence of any significant stenosis in cardiac arrest patients without ST-elevation who underwent coronary angiography within 28 days was 71 degrees 0. The incidence of any stenosis in patients with normal ECG was 62.1 degrees 0 and in patients with LBBB, 59.3 degrees 0. In patients with ST-depression or RBBB, PCI attempts were made in 47.1 degrees 0 and 42.4 degrees 0 respectively, compared with 33.3 degrees 0 in patients with normal ECG. Among patients without ST-elevation, those with diabetes mellitus and those with initial shockable rhythm respectively, 84.8 degrees 0 and 71.5 had at least one significant stenosis.

Conclusion: Our study suggests, that evaluation of ECG patterns and comorbidities in out-of-hospital cardiac arrest patients without ST-segment elevation may be important to identify those with a high risk of coronary artery lesions that could benefit from early revascularization.