Clonal Decomposition and DNA Replication States Defined by Scaled Single-Cell Genome Sequencing.

Accurate measurement of clonal genotypes, mutational processes, and replication states from individual tumor-cell genomes will facilitate improved understanding of tumor evolution. We have developed DLP+, a scalable single-cell whole-genome sequencing platform implemented using commodity instruments, image-based object recognition, and open source computational methods. Using DLP+, we have generated a resource of 51,926 single-cell genomes and matched cell images from diverse cell types including cell lines, xenografts, and diagnostic samples with limited material. From this resource we have defined variation in mitotic mis-segregation rates across tissue types and genotypes. Analysis of matched genomic and image measurements revealed correlations between cellular morphology and genome ploidy states. Aggregation of cells sharing copy number profiles allowed for calculation of single-nucleotide resolution clonal genotypes and inference of clonal phylogenies and avoided the limitations of bulk deconvolution. Finally, joint analysis over the above features defined clone-specific chromosomal aneuploidy in polyclonal populations.

Interfaces of Malignant and Immunologic Clonal Dynamics in Ovarian Cancer.

High-grade serous ovarian cancer (HGSC) exhibits extensive malignant clonal diversity with widespread but non-random patterns of disease dissemination. We investigated whether local immune microenvironment factors shape tumor progression properties at the interface of tumor-infiltrating lymphocytes (TILs) and cancer cells. Through multi-region study of 212 samples from 38 patients with whole-genome sequencing, immunohistochemistry, histologic image analysis, gene expression profiling, and T and B cell receptor sequencing, we identified three immunologic subtypes across samples and extensive within-patient diversity. Epithelial CD8+ TILs negatively associated with malignant diversity, reflecting immunological pruning of tumor clones inferred by neoantigen depletion, HLA I loss of heterozygosity, and spatial tracking between T cell and tumor clones. In addition, combinatorial prognostic effects of mutational processes and immune properties were observed, illuminating how specific genomic aberration types associate with immune response and impact survival. We conclude that within-patient spatial immune microenvironment variation shapes intraperitoneal malignant spread, provoking new evolutionary perspectives on HGSC clonal dispersion.

Need for Blood Transfusion Volume Is Associated With Increased Mortality in Severe Traumatic Brain Injury.

INTRODUCTION: Many patients suffering from isolated severe traumatic brain injury (sTBI) receive blood transfusion on hospital arrival due to hypotension. We hypothesized that increasing blood transfusions in isolated sTBI patients would be associated with an increase in mortality. METHODS: We performed a trauma quality improvement program (TQIP) (2017-2019) and single-center (2013-2021) database review filtering for patients with isolated sTBI (Abbreviated Injury Scale head ≥3 and all other areas ≤2). Age, initial Glasgow Coma Score (GCS), Injury Severity Score (ISS), initial systolic blood pressure (SBP), mechanism (blunt/penetrating), packed red blood cells (pRBCs) and fresh frozen plasma (FFP) transfusion volume (units) within the first 4 h, FFP/pRBC ratio (4h), and in-hospital mortality were obtained from the TQIP Public User Files. RESULTS: In the TQIP database, 9257 patients had isolated sTBI and received pRBC transfusion within the first 4 h. The mortality rate within this group was 47.3%. The increase in mortality associated with the first unit of pRBCs was 20%, then increasing approximately 4% per unit transfused to a maximum mortality of 74% for 11 or more units. When adjusted for age, initial GCS, ISS, initial SBP, and mechanism, pRBC volume (1.09 [1.08-1.10], FFP volume (1.08 [1.07-1.09]), and FFP/pRBC ratio (1.18 [1.08-1.28]) were associated with in-hospital mortality. Our single-center study yielded 138 patients with isolated sTBI who received pRBC transfusion. These patients experienced a 60.1% in-hospital mortality rate. Logistic regression corrected for age, initial GCS, ISS, initial SBP, and mechanism demonstrated no significant association between pRBC transfusion volume (1.14 [0.81-1.61]), FFP transfusion volume (1.29 [0.91-1.82]), or FFP/pRBC ratio (6.42 [0.25-164.89]) and in-hospital mortality. CONCLUSIONS: Patients suffering from isolated sTBI have a higher rate of mortality with increasing amount of pRBC or FFP transfusion within the first 4 h of arrival.

Just Say NO: Inhaled Nitric Oxide Effect on Respiratory Parameters Following Traumatic Brain Injury in Humans and a Porcine Model.

INTRODUCTION: The mechanism of post-traumatic brain injury (TBI) hypoxemia involves ventilation/perfusion mismatch and loss of pulmonary hypoxic vasoconstriction. Inhaled nitric oxide (iNO) has been studied as an adjunct treatment to avoid the use of high positive end-expiratory pressure and inspired oxygen in treatment-refractory hypoxia. We hypothesized that iNO treatment following TBI would improve systemic and cerebral oxygenation via improved matching of pulmonary perfusion and ventilation. METHODS: Thirteen human patients with isolated TBI were enrolled and randomized to receive either placebo or iNO with measured outcomes including pulmonary parameters, blood gas data, and intracranial pressure (ICP) /perfusion. To complement this study, a porcine model of TBI (including 10 swine) was utilized with measured outcomes of brain tissue blood flow and oxygenation, ventilator parameters, and blood gas data both after administration and following drug removal and clearance. RESULTS: There were no clinically significant changes in pulmonary parameters in either the human or porcine arm following administration of iNO when compared to either the placebo group (human arm) or the internal control (porcine arm). Analysis of pooled human data demonstrated the preservation of alveolar recruitment in TBI patients. There were no clinically significant changes in human ICP or cerebral perfusion pressure following iNO administration compared to controls. CONCLUSIONS: iNO had no significant effect on clinically relevant pulmonary parameters or ICPs following TBI in both human patients and a porcine model. The pressure-based recruitment of the human lungs following TBI was preserved. Further investigation will be needed to determine the degree of utility of iNO in the setting of hypoxia after polytrauma.

Validation of Preload Assessment Technologies at Altitude in a Porcine Model of Hemorrhage.

INTRODUCTION: Dynamic preload assessment measures including pulse pressure variation (PPV), stroke volume variation (SVV), pleth variability index (PVI), and hypotension prediction index (HPI) have been utilized clinically to guide fluid management decisions in critically ill patients. These values aid in the balance of correcting hypotension while avoiding over-resuscitation leading to respiratory failure and increased mortality. However, these measures have not been previously validated at altitude or in those with temporary abdominal closure (TAC). METHODS: Forty-eight female swine (39 ± 2 kg) were separated into eight groups (n = 6) including all combinations of flight versus ground, hemorrhage versus no hemorrhage, and TAC versus no TAC. Flight animals underwent simulated aeromedical evacuation via an altitude chamber at 8000 ft. Hemorrhagic shock was induced via stepwise hemorrhage removing 10% blood volume in 15-min increments to a total blood loss of 40% or a mean arterial pressure of 35 mmHg. Animals were then stepwise transfused with citrated shed blood with 10% volume every 15 min back to full blood volume. PPV, SVV, PVI, and HPI were monitored every 15 min throughout the simulated aeromedical evacuation or ground control. Blood samples were collected and analyzed for serum levels of serum IL-1ß, IL-6, IL-8, and TNF-α. RESULTS: Hemorrhage groups demonstrated significant increases in PPV, SVV, PVI, and HPI at each step compared to nonhemorrhage groups. Flight increased PPV (P = 0.004) and SVV (P = 0.003) in hemorrhaged animals. TAC at ground level increased PPV (P < 0.0001), SVV (P = 0.0003), and PVI (P < 0.0001). When TAC was present during flight, PPV (P = 0.004), SVV (P = 0.003), and PVI (P < 0.0001) values were decreased suggesting a dependent effect between altitude and TAC. There were no significant differences in serum IL-1ß, IL-6, IL-8, or TNF-α concentration between injury groups. CONCLUSIONS: Based on our study, PPV and SVV are increased during flight and in the presence of TAC. Pleth variability index is slightly increased with TAC at ground level. Hypotension prediction index demonstrated no significant changes regardless of altitude or TAC status, however this measure was less reliable once the resuscitation phase was initiated. Pleth variability index may be the most useful predictor of preload during aeromedical evacuation as it is a noninvasive modality.

Re-Evaluating the Use of High Sensitivity Troponin to Diagnose Blunt Cardiac Injury.

INTRODUCTION: Blunt cardiac injury (BCI) can be challenging diagnostically, and if misdiagnosed, can lead to life-threatening complications. Our institution previously evaluated BCI screening with troponin and electrocardiogram (EKG) during a transition from troponin I to high sensitivity troponin (hsTnI), a more sensitive troponin I assay. The previous study found an hsTnI of 76 ng/L had the highest capability of accurately diagnosing a clinically significant BCI. The aim of this study was to determine the efficacy of the newly implemented protocol. METHODS: Patients diagnosed with a sternal fracture from March 2022 to April 2023 at our urban level-1 trauma center were retrospectively reviewed for EKG findings, hsTnI trend, echocardiogram changes, and clinical outcomes. The BCI cohort and non-BCI cohort ordinal measures were compared using Wilcoxon's two-tailed rank sum test and categorical measures were compared with Fisher's exact test. Youden indices were used to evaluate hsTnI sensitivity and specificity. RESULTS: Sternal fractures were identified in 206 patients, of which 183 underwent BCI screening. Of those screened, 103 underwent echocardiogram, 28 were diagnosed with clinically significant BCIs, and 15 received intervention. The peak hsTnI threshold of 76 ng/L was found to have a Youden index of 0.31. Rather, the Youden index was highest at 0.50 at 40 ng/L (sensitivity 0.79 and specificity 0.71) for clinically significant BCI. CONCLUSIONS: Screening patients with sternal fractures for BCI using hsTnI and EKG remains effective. To optimize the hsTnI threshold, this study determined the hsTnI threshold should be lowered to 40 ng/L. Further improvements to the institutional protocol may be derived from multicenter analysis.

Predictive Value of Early Inflammatory Markers in Trauma Patients Based on Transfusion Status.

INTRODUCTION: Seven key inflammatory biomarkers were recently found to be associated with the risk of mortality in a multicenter study of massively transfused patients. The aim of this prospective single-center study was to determine which of these early inflammatory markers could predict 30-d mortality among all critically injured trauma patients. METHODS: Serum samples were collected at 6, 24, and 72 h from 238 consecutive patients admitted to the intensive care unit following traumatic injury. Inflammatory markers syndecan-1, eotaxin, IL-1ra, IL-6, IL-8, IL-10, IP-10, and MCP-1 were analyzed via multiplex enzyme-linked immunosorbent assay. Subgroup analysis was performed for patients undergoing massive transfusion (≥5 red blood cells), submassive transfusion (1-4 red blood cells), or no transfusion during the first 4 h postinjury. The primary outcome of 30-d survival was modeled as a function of each biomarker and confounders using repeat measures logistic regression. RESULTS: Patients had a median age of 51.3 y [33.7, 70.2], 70.6% were male, 17.4% experienced penetrating trauma, and had a median injury severity score of 22 [14, 33]. IL-1ra, IL-8, IL-10, and MCP-1 were significantly increased during the first 72 h in nonsurvivors (n = 31). Elevated IL-1ra, IL-8, IL-10, and MCP-1 at 6 h postinjury were associated with 30-d mortality. By contrast, serum syndecan-1 and eotaxin levels were not associated with mortality at any time point. IL-8 and lactate were increased at 6 h in 30-d nonsurvivors for patients receiving submassive transfusion (n = 78). CONCLUSIONS: Early evaluations of IL-1ra, IL-8, IL-10, and IP-10 within 6 h of injury are useful predictors of 30-d mortality. Subgroup analysis suggests that transfusion status does not significantly affect early inflammatory markers. LEVEL OF EVIDENCE: Level III, prognostic/epidemiological.

Co-producing Human and Animal Experimental Subjects: Exploring the Views of UK COVID-19 Vaccine Trial Participants on Animal Testing.

Preclinical (animal) testing and human testing of drugs and vaccines are rarely considered by social scientists side by side. Where this is done, it is typically for theoretically exploring the ethics of the two situations to compare relative treatment. In contrast, we empirically explore how human clinical trial participants understand the role of animal test subjects in vaccine development. Furthermore, social science research has only concentrated on broad public opinion and the views of patients about animal research, whereas we explore the views of a public group particularly implicated in pharmaceutical development: experimental subjects. We surveyed and interviewed COVID-19 vaccine trial participants in Oxford, UK, on their views about taking part in a vaccine trial and the role of animals in trials. We found that trial participants mirrored assumptions about legitimate reasons for animal testing embedded in regulation and provided insight into (i) the nuances of public opinion on animal research; (ii) the co-production of human and animal experimental subjects; (iii) how vaccine and medicine testing, and the motivations and demographics of clinical trial participants, change in an outbreak; and (iv) what public involvement can offer to science.

Change in country-level COVID-19 lethality is associated with improved testing: no apparent role of medical care or disease-specific knowledge.

AIM: Reductions in the case fatality rate of COVID-19 in the unvaccinated have been credited to improvements in medical care. Here I test whether either of these factors predicts reductions in the case fatality rate, and whether observed reductions are better explicable by improved ascertainment of mild cases. METHODS: Using weighted log-log regression, I compute the association between changes in the case fatality rate and test density between 3 July 2020 and 5 January 2021 in 162 countries; and check whether case fatality rate change is associated with either per capita medical spending (proxy for critical care access) or timing of the pandemic (proxy for COVID-specific knowledge). RESULTS: The median test density increased from 175 tests per thousand population to 1200, while the median case fatality rate dropped from 4.1% to 2.0%. While the case fatality rate was higher at both timepoints in Europe/North America than Africa / Asia, its association with test density was similar across countries. For each doubling in test density, the mean case fatality rate decreased by 18% (P<0.0001) with a median (interquartile rate) country-level decline of 20% (5-30) per doubling of test density. The rate of change of the case fatality rate was not associated with either medical care access or COVID-specific knowledge (all P>0.10). CONCLUSIONS: Declines in the case fatality rate were adequately explained by improved testing, with no effect of either medical knowledge or improvements in care. The true lethality of COVID-19 may not have changed much at the population level. Prevention should remain a priority.

Self-estimated BMI, but not self-perceived body size, accurately identifies unhealthy weight in US adults.

BACKGROUND: Self-perceptions of health and disease can be a major driver of health behaviors. Improving accuracy of self-ascertainment of obesity may prompt uptake of weight-control behaviors in those with obesity. METHODS: We assess performance of self-perceived body size ('too small', 'about right' or 'too large'), self-estimated BMI in kg/m2, and sociodemographics in detecting measured BMI category (under-, normal-, overweight and obese; BMI cutpoints 18.5, 25 and 30) in first bivariate and then multivariable models. RESULTS: Of 37,281 adults in the US from NHANES, 2, 34, 33 and 32% were under-, normal-, overweight and obese. Respectively 56, 73, 60 and 91% self-perceived as 'too small', 'about right', 'too large' and 'too large.' Of those who self-perceived as 'too small', 22% were underweight and 10% were overweight or obese. 99.7% of obese participants self-estimated a BMI in the overweight/obese range, including many who did not self-perceive as 'too large'. Among obese participants, self-perception as either 'about right' or 'too small' was more likely for those who were younger (OR for perception as 'too large' 1.01 per year, 95% confidence interval 1.00-1.01) male (OR 0.33, (0.28-0.39)) nonwhite (ORs 0.36-0.79 for different ethnicities), low-income (ORs 0.61 and 1.8 for the lowest and highest of six categories, vs. the third) or measured recently (OR 0.98 (0.96-1.0) per year since 1999). Misperception was less common, but still existed, for participants with moderate or severe obesity (ORs 2.9 (2.3-3.5) and 7.9 (5.4-12), vs. 'mild.') (all p < 0.01.) CONCLUSIONS: A tenth of adults in the US with obesity, especially those from overweight peer groups, self-perceive as normal or underweight and thus may not be motivated to control their weight. However, virtually all self-estimate an overweight or obese BMI. If measured BMI is not available, self-estimates are sufficiently accurate that interventions may rely on it to identify obesity.

Clonal genotype and population structure inference from single-cell tumor sequencing.

Single-cell DNA sequencing has great potential to reveal the clonal genotypes and population structure of human cancers. However, single-cell data suffer from missing values and biased allelic counts as well as false genotype measurements owing to the sequencing of multiple cells. We describe the Single Cell Genotyper (https://bitbucket.org/aroth85/scg), an open-source software based on a statistical model coupled with a mean-field variational inference method, which can be used to address these problems and robustly infer clonal genotypes.

A collaborative filtering-based approach to biomedical knowledge discovery.

Motivation: The increase in publication rates makes it challenging for an individual researcher to stay abreast of all relevant research in order to find novel research hypotheses. Literature-based discovery methods make use of knowledge graphs built using text mining and can infer future associations between biomedical concepts that will likely occur in new publications. These predictions are a valuable resource for researchers to explore a research topic. Current methods for prediction are based on the local structure of the knowledge graph. A method that uses global knowledge from across the knowledge graph needs to be developed in order to make knowledge discovery a frequently used tool by researchers. Results: We propose an approach based on the singular value decomposition (SVD) that is able to combine data from across the knowledge graph through a reduced representation. Using cooccurrence data extracted from published literature, we show that SVD performs better than the leading methods for scoring discoveries. We also show the diminishing predictive power of knowledge discovery as we compare our predictions with real associations that appear further into the future. Finally, we examine the strengths and weaknesses of the SVD approach against another well-performing system using several predicted associations. Availability and implementation: All code and results files for this analysis can be accessed at https://github.com/jakelever/knowledgediscovery. Contact: sjones@bcgsc.ca. Supplementary information: Supplementary data are available at Bioinformatics online.

Single Cell Phenotyping Reveals Heterogeneity Among Hematopoietic Stem Cells Following Infection.

The hematopoietic stem cell (HSC) niche provides essential microenvironmental cues for the production and maintenance of HSCs within the bone marrow. During inflammation, hematopoietic dynamics are perturbed, but it is not known whether changes to the HSC-niche interaction occur as a result. We visualize HSCs directly in vivo, enabling detailed analysis of the 3D niche dynamics and migration patterns in murine bone marrow following Trichinella spiralis infection. Spatial statistical analysis of these HSC trajectories reveals two distinct modes of HSC behavior: (a) a pattern of revisiting previously explored space and (b) a pattern of exploring new space. Whereas HSCs from control donors predominantly follow pattern (a), those from infected mice adopt both strategies. Using detailed computational analyses of cell migration tracks and life-history theory, we show that the increased motility of HSCs following infection can, perhaps counterintuitively, enable mice to cope better in deteriorating HSC-niche microenvironments following infection. Stem Cells 2017;35:2292-2304.

Physical activity, subjective sleep quality and time in bed do not vary by moon phase in German adolescents.

Lunar periodicity in human biology and behaviour, particularly sleep, has been reported. However, estimated relationships vary in direction (more or less sleep with full moon) if they exist at all, and studies tend to be so small that there is potential for confounding by weekly or monthly cycles. Lunar variation in physical activity has been posited as a driver of this relationship, but is likewise not well studied. We explore the association between lunar cycle, sleep and physical activity in a population-based sample of 1411 Germans age 14-17 years (46% male). Physical activity (daily minutes moderate-to-vigorous activity) was objectively assessed by accelerometry for a total of 8832 days between 2011 and 2014. At the same time, time in bed (h) and subjective sleep quality (1-6) were diaried each morning. In models corrected for confounding, we found that lunar phase was not significantly associated with physical activity, subjective sleep quality or time in bed in either sex, regardless of season. Observed relationships varied randomly in direction between models, suggesting artefact. Thus, this large, objectively-measured and well-controlled population of adolescents displayed no lunar periodicity in objective physical activity, subjective sleep quality or time in bed.

Histological Transformation and Progression in Follicular Lymphoma: A Clonal Evolution Study.

BACKGROUND: Follicular lymphoma (FL) is an indolent, yet incurable B cell malignancy. A subset of patients experience an increased mortality rate driven by two distinct clinical end points: histological transformation and early progression after immunochemotherapy. The nature of tumor clonal dynamics leading to these clinical end points is poorly understood, and previously determined genetic alterations do not explain the majority of transformed cases or accurately predict early progressive disease. We contend that detailed knowledge of the expansion patterns of specific cell populations plus their associated mutations would provide insight into therapeutic strategies and disease biology over the time course of FL clinical histories. METHODS AND FINDINGS: Using a combination of whole genome sequencing, targeted deep sequencing, and digital droplet PCR on matched diagnostic and relapse specimens, we deciphered the constituent clonal populations in 15 transformation cases and 6 progression cases, and measured the change in clonal population abundance over time. We observed widely divergent patterns of clonal dynamics in transformed cases relative to progressed cases. Transformation specimens were generally composed of clones that were rare or absent in diagnostic specimens, consistent with dramatic clonal expansions that came to dominate the transformation specimens. This pattern was independent of time to transformation and treatment modality. By contrast, early progression specimens were composed of clones that were already present in the diagnostic specimens and exhibited only moderate clonal dynamics, even in the presence of immunochemotherapy. Analysis of somatic mutations impacting 94 genes was undertaken in an extension cohort consisting of 395 samples from 277 patients in order to decipher disrupted biology in the two clinical end points. We found 12 genes that were more commonly mutated in transformed samples than in the preceding FL tumors, including TP53, B2M, CCND3, GNA13, S1PR2, and P2RY8. Moreover, ten genes were more commonly mutated in diagnostic specimens of patients with early progression, including TP53, BTG1, MKI67, and XBP1. CONCLUSIONS: Our results illuminate contrasting modes of evolution shaping the clinical histories of transformation and progression. They have implications for interpretation of evolutionary dynamics in the context of treatment-induced selective pressures, and indicate that transformation and progression will require different clinical management strategies.

Physical activity is not associated with spirometric indices in lung-healthy German youth.

In lung disease, physical activity improves lung function and reduces morbidity. However, healthy populations are not well studied. We estimate the relationship between spirometric indices and accelerometric physical activity in lung-healthy adolescents.895 nonsmoking German adolescents without chronic lung disease (45% male, mean±sd age 15.2±0.26 years) from the GINIplus and LISAplus cohorts completed questionnaires, spirometry, 7-day accelerometry and an activity diary. Physical activity was measured as minutes, quintiles and regularity of daily moderate, vigorous and moderate-to-vigorous physical activity (MVPA), participation in sport and active commuting to school. Primary outcomes were forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC and forced expiratory flow at 25-75% of FVC; they were separately correlated with physical activity and adjusted for confounders of respiratory function, including early-life exposures.Adolescents averaged 40 min MVPA per day, typical for European youth. 79% participated in sports and 51% commuted actively. An association was suggested between 3% higher FVC (∼100 mL) and either extreme MVPA quintile or percentage of days with >30 min MVPA (p<0.05). However, after Bonferroni correction all associations between spirometry, active lifestyle and physical activity were nonsignificant.Spirometric indices were not significantly associated with active lifestyle or measures of activity in lung-healthy adolescents after adjustment for confounding and multiple-comparison artefacts.

Neighbourhood and physical activity in German adolescents: GINIplus and LISAplus.

INTRODUCTION: Impact of neighbourhood on physical activity (PA) is under-investigated in European adolescents, and few studies have used objective data on both exposures and outcomes. Therefore we investigated the association between objectively measured neighbourhood characteristics and PA in 15-year-old German adolescents. METHODS: Study populations comprised of 688 adolescents residing in the urban Munich area and 504 from the rural Wesel area from the GINIplus and LISAplus birth cohorts. Neighbourhood was defined as a circular 500-m buffer around the residence. Greenness was calculated 1) as the mean Normalized Difference Vegetation Index (NDVI), and 2) as percent tree cover. Neighbourhood green spaces and sport and leisure facilities were defined as present or absent in a neighbourhood (data only available for Munich). Data on PA were collected from one-week triaxial accelerometry (hip-worn ActiGraph GT3X). Minutes of PA were classified into moderate-to-vigorous (MVPA), light and sedentary using Romanzini's et al. triaxial cutoffs, and averaged over the recording period. Activity diaries were used for differentiation between school and leisure (total minus school) PA. Area-specific associations were assessed by adjusted negative binomial regressions. RESULTS: In the Wesel area, residing in a neighbourhood with higher NDVI was associated with 9% more leisure MVPA among females and with 8% more leisure MVPA in rural dwellers. In the Munich area, residing in a neighbourhood with sport facilities was associated with 9% more leisure MVPA. The latter association was only significant in urban dwellers while neighbourhood leisure facilities increased MVPA in rural dwellers. Estimates were very similar when total MVPA was considered rather than solely leisure. CONCLUSION: There is indication that neighbourhood features could be associated with MVPA in German adolescents. However, different features seem to be important across sexes and in rural/urban settings, which need to be specifically addressed in future studies.

Evaluation of a Rebreathing System for Use with Portable Mechanical Ventilators.

INTRODUCTION: Maximizing the capabilities of available lowflow oxygen is key to providing adequate oxygen to prevent/treat hypoxemia and conserve oxygen. We designed a closed-circuit system that allows rebreathing of gases while scrubbing carbon dioxide (CO2) in conjunction with portable mechanical ventilators in a bench model. METHODS: We evaluated the system using two portable mechanical ventilators currently deployed by the Department of Defense-Zoll 731 and AutoMedx SAVe II-over a range of ventilator settings and lung models, using 1 and 3L/min low-flow oxygen into a reservoir bag. We measured peak inspired oxygen concentration (FiO2), CO2-absorbent life, gas temperature and humidity, and the effect of airway suctioning and ventilator disconnection on FiO2 on ground and at altitude. RESULTS: FiO2 was =0.9 across all ventilator settings and altitudes using both oxygen flows. CO2-absorbent life was >7 hours. Airway humidity range was 87%-97%. Mean airway temperature was 25.4°C (SD 0.5°C). Ten-second suctioning reduced FiO2 22%-48%. Thirtysecond ventilator disconnect reduced FiO2 29%-63% depending on oxygen flow used. CONCLUSION: Use of a rebreathing system with mechanical ventilation has the potential for oxygen conservation but requires diligent monitoring of inspired FiO2 and CO2 to avoid negative consequences.

Identifying and Reducing Insulin Errors in the Simulated Military Critical Care Air Transport Environment: A Human Factors Approach.

INTRODUCTION: During high-fidelity simulations in the Critical Care Air Transport (CCAT) Advanced course, we identified a high frequency of insulin medication errors and sought strategies to reduce them using a human factors approach. MATERIALS AND METHODS: Of 169 eligible CCAT simulations, 22 were randomly selected for retrospective audio-video review to establish a baseline frequency of insulin medication errors. Using the Human Factors Analysis Classification System, dosing errors, defined as a physician ordering an inappropriate dose, were categorized as decision-based; administration errors, defined as a clinician preparing and administering a dose different than ordered, were categorized as skill-based. Next, 3 a priori interventions were developed to decrease the frequency of insulin medication errors, and these were grouped into 2 study arms. Arm 1 included a didactic session reviewing a sliding-scale insulin (SSI) dosing protocol and a hands-on exercise requiring all CCAT teams to practice preparing 10 units of insulin including a 2-person check. Arm 2 contained arm 1 interventions and added an SSI cognitive aid available to students during simulation. Frequency and type of insulin medication errors were collected for both arms with 93 simulations for arm 1 (January-August 2021) and 139 for arm 2 (August 2021-July 2022). The frequency of decision-based and skill-based errors was compared across control and intervention arms. RESULTS: Baseline insulin medication error rates were as follows: decision-based error occurred in 6/22 (27.3%) simulations and skill-based error occurred in 6/22 (27.3%). Five of the 6 skill-based errors resulted in administration of a 10-fold higher dose than ordered. The post-intervention decision-based error rates were 9/93 (9.7%) and 23/139 (2.2%), respectively, for arms 1 and 2. Compared to baseline error rates, both arm 1 (P = .04) and arm 2 (P < .001) had a significantly lower rate of decision-based errors. Additionally, arm 2 had a significantly lower decision-based error rate compared to arm 1 (P = .015). For skill-based preparation errors, 1/93 (1.1%) occurred in arm 1 and 4/139 (2.9%) occurred in arm 2. Compared to baseline, this represents a significant decrease in skill-based error in both arm 1 (P < .001) and arm 2 (P < .001). There were no significant differences in skill-based error between arms 1 and 2. CONCLUSIONS: This study demonstrates the value of descriptive error analysis during high-fidelity simulation using audio-video review and effective risk mitigation using training and cognitive aids to reduce medication errors in CCAT. As demonstrated by post-intervention observations, a human factors approach successfully reduced decision-based error by using didactic training and cognitive aids and reduced skill-based error using hands-on training. We recommend the development of a Clinical Practice Guideline including an SSI protocol, guidelines for a 2-person check, and a cognitive aid for implementation with deployed CCAT teams. Furthermore, hands-on training for insulin preparation and administration should be incorporated into home station sustainment training to reduced medication errors in the operational environment.