Proximity Extension Assay in Combination with Next-Generation Sequencing for High-throughput Proteome-wide Analysis

Understanding the dynamics of the human proteome is crucial for developing biomarkers to be used as measurable indicators for disease severity and progression, patient stratification, and drug development. The Proximity Extension Assay (PEA) is a technology that translates protein information into actionable knowledge by linking protein-specific antibodies to DNA-encoded tags. In this report we demonstrate how we have combined the unique PEA technology with an innovative and automated sample preparation and high-throughput sequencing readout enabling parallel measurement of nearly 1500 proteins in 96 samples generating close to 150,000 data points per run. This advancement will have a major impact on the discovery of new biomarkers for disease prediction and prognosis and contribute to the development of the rapidly evolving fields of wellness monitoring and precision medicine.

Tidal volume measurements via transthoracic impedance waveform characteristics: The effect of age, body mass index and gender. A single centre interventional study

BACKGROUND AND AIM

Measuring tidal volumes (TV) during bag-valve ventilation is challenging in the clinical setting. The ventilation waveform amplitude of the transthoracic impedance (TTI-amplitude) correlates well with TV for an individual, but poorer between patients. We hypothesized that TV to TTI-amplitude relations could be improved when adjusted for morphometric variables like body mass index (BMI), gender or age, and that TTI-amplitude cut-offs for ventilations with adequate TV (>400ml) could be established.

MATERIALS AND METHODS

Twenty-one consenting adults (9 female, and 9 overall overweight) during positive pressure ventilation in anaesthesia before scheduled surgery were included. Seventeen ventilator modes were used (⩾ five breaths per mode) to adjust different TVs (150-800 ml), ventilation frequencies (10-30 min^-1) and insufflation times (0.5-3.5 s). TTI from the defibrillation pads was filtered to obtain ventilation TTI-amplitudes. Linear regression models were fitted between target and explanatory variables, and compared (coefficient of determination, R²).

RESULTS

The TV to TTI-amplitude slope was 1.39 Ω/l (R²=0.52), with significant differences (p<0.05) between male/female (1.04 Ω/l vs 1.84 Ω/l) and normal/overweight subjects (1.65 Ω/l vs 1.04 Ω/l). The median (interquartile range) TTI-amplitude cut-off for adequate TV was 0.51 Ω(0.14-1.20) with significant differences between males and females (0.58 Ω/0.39 Ω), and normal and overweight subjects (0.52 Ω/0.46 Ω). The TV to TTI-amplitude model improved (R²=0.66) when BMI, age and gender were included.

CONCLUSIONS

TTI-amplitude to TV relations were established and cut-offs for ventilations with adequate TV determined. Patient morphometric variables related to gender, age and BMI explain part of the variability in the measurements.

Shock decision algorithm for use during load distributing band cardiopulmonary resuscitation

AIM

Chest compressions delivered by a load distributing band (LDB) induce artefacts in the electrocardiogram. These artefacts alter shock decisions in defibrillators. The aim of this study was to demonstrate the first reliable shock decision algorithm during LDB compressions.

METHODS

The study dataset comprised 5813 electrocardiogram segments from 896 cardiac arrest patients during LDB compressions. Electrocardiogram segments were annotated by consensus as shockable (1154, 303 patients) or nonshockable (4659, 841 patients). Segments during asystole were used to characterize the LDB artefact and to compare its characteristics to those of manual artefacts from other datasets. LDB artefacts were removed using adaptive filters. A machine learning algorithm was designed for the shock decision after filtering, and its performance was compared to that of a commercial defibrillator's algorithm.

RESULTS

Median (90% confidence interval) compression frequencies were lower and more stable for the LDB than for the manual artefact, 80 min^-1 (79.9-82.9) vs. 104.4 min^-1 (48.5-114.0). The amplitude and waveform regularity (Pearson's correlation coefficient) were larger for the LDB artefact, with 5.5 mV (0.8-23.4) vs. 0.5 mV (0.1-2.2) (p < 0.001) and 0.99 (0.78-1.0) vs. 0.88 (0.55-0.98) (p < 0.001). The shock decision accuracy was significantly higher for the machine learning algorithm than for the defibrillator algorithm, with sensitivity/specificity pairs of 92.1/96.8% (machine learning) vs. 91.4/87.1% (defibrillator) (p < 0.001).

CONCLUSION

Compared to other cardiopulmonary resuscitation artefacts, removing the LDB artefact was challenging due to larger amplitudes and lower compression frequencies. The machine learning algorithm achieved clinically reliable shock decisions during LDB compressions.

A fine-needle aspiration-based protein signature discriminates benign from malignant breast lesions

There are increasing demands for informative cancer biomarkers, accessible via minimally invasive procedures, both for initial diagnostics and to follow-up personalized cancer therapy. Fine-needle aspiration (FNA) biopsy provides ready access to relevant tissues; however, the minute sample amounts require sensitive multiplex molecular analysis to achieve clinical utility. We have applied proximity extension assays (PEA) and NanoString (NS) technology for analyses of proteins and of RNA, respectively, in FNA samples. Using samples from patients with breast cancer (BC, n = 25) or benign lesions (n = 33), we demonstrate that these FNA-based molecular analyses (a) can offer high sensitivity and reproducibility, (b) may provide correct diagnosis in shorter time and at a lower cost than current practice, (c) correlate with results from routine analysis (i.e., benchmarking against immunohistochemistry tests for ER, PR, HER2, and Ki67), and (d) may also help identify new markers related to immunotherapy. A specific 11-protein signature, including FGF binding protein 1, decorin, and furin, distinguished all cancer patient samples from all benign lesions in our main cohort and in smaller replication cohort. Due to the minimally traumatic sampling and rich molecular information, this combined proteomics and transcriptomic methodology is promising for diagnostics and evaluation of treatment efficacy in BC.

Snail regulates BMP and TGFβ pathways to control the differentiation status of glioma-initiating cells

Glioblastoma multiforme is a brain malignancy characterized by high heterogeneity, invasiveness, and resistance to current therapies, attributes related to the occurrence of glioma stem cells (GSCs). Transforming growth factor β (TGFβ) promotes self-renewal and bone morphogenetic protein (BMP) induces differentiation of GSCs. BMP7 induces the transcription factor Snail to promote astrocytic differentiation in GSCs and suppress tumor growth in vivo. We demonstrate that Snail represses stemness in GSCs. Snail interacts with SMAD signaling mediators, generates a positive feedback loop of BMP signaling and transcriptionally represses the TGFB1 gene, decreasing TGFβ1 signaling activity. Exogenous TGFβ1 counteracts Snail function in vitro, and in vivo promotes proliferation and re-expression of Nestin, confirming the importance of TGFB1 gene repression by Snail. In conclusion, novel insight highlights mechanisms whereby Snail differentially regulates the activity of the opposing BMP and TGFβ pathways, thus promoting an astrocytic fate switch and repressing stemness in GSCs.

Analytically Sensitive Protein Detection in Microtiter Plates by Proximity Ligation with Rolling Circle Amplification

BACKGROUND

Detecting proteins at low concentrations in plasma is crucial for early diagnosis. Current techniques in clinical routine, such as sandwich ELISA, provide sensitive protein detection because of a dependence on target recognition by pairs of antibodies, but detection of still lower protein concentrations is often called for. Proximity ligation assay with rolling circle amplification (PLARCA) is a modified proximity ligation assay (PLA) for analytically specific and sensitive protein detection via binding of target proteins by 3 antibodies, and signal amplification via rolling circle amplification (RCA) in microtiter wells, easily adapted to instrumentation in use in hospitals.

METHODS

Proteins captured by immobilized antibodies were detected using a pair of oligonucleotide-conjugated antibodies. Upon target recognition these PLA probes guided oligonucleotide ligation, followed by amplification via RCA of circular DNA strands that formed in the reaction. The RCA products were detected by horseradish peroxidase-labeled oligonucleotides to generate colorimetric reaction products with readout in an absorbance microplate reader.

RESULTS

We compared detection of interleukin (IL)-4, IL-6, IL-8, p53, and growth differentiation factor 15 (GDF-15) by PLARCA and conventional sandwich ELISA or immuno-RCA. PLARCA detected lower concentrations of proteins and exhibited a broader dynamic range compared to ELISA and iRCA using the same antibodies. IL-4 and IL-6 were detected in clinical samples at femtomolar concentrations, considerably lower than for ELISA.

CONCLUSIONS

PLARCA offers detection of lower protein levels and increased dynamic ranges compared to ELISA. The PLARCA procedure may be adapted to routine instrumentation available in hospitals and research laboratories.

Stability of Proteins in Dried Blood Spot Biobanks

An important motivation for the construction of biobanks is to discover biomarkers that identify diseases at early, potentially curable stages. This will require biobanks from large numbers of individuals, preferably sampled repeatedly, where the samples are collected and stored under conditions that preserve potential biomarkers. Dried blood samples are attractive for biobanking because of the ease and low cost of collection and storage. Here we have investigated their suitability for protein measurements. Ninety-two proteins with relevance for oncology were analyzed using multiplex proximity extension assays (PEA) in dried blood spots collected on paper and stored for up to 30 years at either +4 °C or −24 °C.

Our main findings were that (1) the act of drying only slightly influenced detection of blood proteins (average correlation of 0.970), and in a reproducible manner (correlation of 0.999), (2) detection of some proteins was not significantly affected by storage over the full range of three decades (34 and 76% of the analyzed proteins at +4 °C and −24 °C, respectively), whereas levels of others decreased slowly during storage with half-lives in the range of 10 to 50 years, and (3) detectability of proteins was less affected in dried samples stored at −24 °C compared with at +4 °C, as the median protein abundance had decreased to 80 and 93% of starting levels after 10 years of storage at +4 °C or −24 °C, respectively. The results of our study are encouraging as they suggest an inexpensive means to collect large numbers of blood samples, even by the donors themselves, and to transport, and store biobanked samples as spots of whole blood dried on paper. Combined with emerging means to measure hundreds or thousands of protein, such biobanks could prove of great medical value by greatly enhancing discovery as well as routine analysis of blood biomarkers.

Tracing Cellular Origin of Human Exosomes Using Multiplex Proximity Extension Assays

Extracellular vesicles (EVs) are membrane-coated objects such as exosomes and microvesicles, released by many cell-types. Their presence in body fluids and the variable surface composition and content render them attractive potential biomarkers. The ability to determine their cellular origin could greatly move the field forward. We used multiplex proximity extension assays (PEA) to identify with high specificity and sensitivity the protein profiles of exosomes of different origins, including seven cell lines and two different body fluids. By comparing cells and exosomes, we successfully identified the cells originating the exosomes. Furthermore, by principal component analysis of protein patterns human milk EVs and prostasomes released from prostate acinar cells clustered with cell lines from breast and prostate tissues, respectively. Milk exosomes uniquely expressed CXCL5, MIA, and KLK6, whereas prostasomes carried NKX31, GSTP1, and SRC, highlighting that EVs originating from different origins express distinct proteins. In conclusion, PEA provides a powerful protein screening tool in exosome research, for purposes of identifying the cell source of exosomes, or new biomarkers in diseases such as cancer and inflammation.

Detecting individual extracellular vesicles using a multicolor in situ proximity ligation assay with flow cytometric readout

Flow cytometry is a powerful method for quantitative and qualitative analysis of individual cells. However, flow cytometric analysis of extracellular vesicles (EVs), and the proteins present on their surfaces has been hampered by the small size of the EVs – in particular for the smallest EVs, which can be as little as 40 nm in diameter, the limited number of antigens present, and their low refractive index. We addressed these limitations for detection and characterization of EV by flow cytometry through the use of multiplex and multicolor in situ proximity ligation assays (in situ PLA), allowing each detected EV to be easily recorded over background noise using a conventional flow cytometer. By targeting sets of proteins on the surface that are specific for distinct classes of EVs, the method allows for selective recognition of populations of EVs in samples containing more than one type of EVs. The method presented herein opens up for analyses of EVs using flow cytometry for their characterization and quantification.

Chest compression duration influences outcome between integrated load-distributing band and manual CPR during cardiac arrest

BACKGROUND

The Circulation Improving Resuscitation Care (CIRC) Trial found equivalent survival in adult out-of-hospital cardiac arrest (OHCA) patients who received integrated load-distributing band CPR (iA-CPR) compared to manual CPR (M-CPR). We hypothesized that as chest compression duration increased, iA-CPR provided a survival benefit when compared to M-CPR.

METHODS

A pre-planned secondary analysis of OHCA of presumed cardiac etiology from the randomized CIRC trial. Chest compressions duration was defined as the total number of minutes spent on compressions during resuscitation and identified from transthoracic impedance and accelerometer data recorded by the EMS defibrillator. Logistic regression was used to model the interaction between treatment and duration of chest compressions and was covariate-adjusted for trial site, patient age, witnessed arrest, and initial shockable rhythm. Primary outcome was survival to hospital discharge.

RESULTS

We enrolled 4231 subjects and of those, 2012 iA-CPR and 2002 M-CPR had complete outcome and duration of chest compressions data. While covariate-adjusted odds ratio for survival to hospital discharge was 1.86 in favor of iA-CPR (95% CI 1.16-3.0), there was an interaction between duration and study arm. When this was factored into the multivariate equation, the odds ratio for survival to hospital discharge showed a significant benefit for iA-CPR vs. M-CPR for chest compression duration greater than 16.5 min.

CONCLUSION

After adjusting for compression duration and duration-treatment interaction, iA-CPR showed a significant benefit for survival to hospital discharge vs. M-CPR in patients with OHCA if chest compression duration was longer than 16.5 min.

Sensitive detection of aggregated prion protein via proximity ligation

The DNA assisted solid-phase proximity ligation assay (SP-PLA) provides a unique opportunity to specifically detect prion protein (PrP) aggregates by investigating the collocation of 3 or more copies of the specific protein. We have developed an SP-PLA that can detect PrP aggregates in brain homogenates from infected hamsters even after a 10(7)-fold dilution. In contrast, brain homogenate from uninfected animals did not generate a detectable signal at 100-fold higher concentration. Using either of the 2 monoclonal anti-PrP antibodies, 3F4 and 6H4, we successfully detected low concentrations of aggregated PrP. The presented results provide a proof of concept that this method might be an interesting tool in the development of diagnostic approaches of prion diseases.

Physiologic, demographic and mechanistic factors predicting New Injury Severity Score (NISS) in motor vehicle accident victims

BACKGROUND

Current literature on motor vehicle accidents (MVAs) has few reports regarding field factors that predict the degree of injury. Also, studies of mechanistic factors rarely consider concurrent predictive effects of on-scene patient physiology. The New Injury Severity Score (NISS) has previously been found to correlate with mortality, need for ICU admission, length of hospital stay, and functional recovery after trauma. To potentially increase future precision of trauma triage, we assessed how the NISS is associated with physiologic, demographic and mechanistic variables from the accident site.

METHODS

Using mixed-model linear regression analyses, we explored the association between NISS and pre-hospital Glasgow Coma Scale (GCS) score, Revised Trauma Score (RTS) categories of respiratory rate (RR) and systolic blood pressure (SBP), gender, age, subject position in the vehicle, seatbelt use, airbag deployment, and the estimated squared change in vehicle velocity on impact ((Δv)(2)). Missing values were handled with multiple imputation.

RESULTS

We included 190 accidents with 353 dead or injured subjects (mean NISS 17, median NISS 8, IQR 1-27). For the 307 subjects in front-impact MVAs, the mean increase in NISS was -2.58 per GCS point, -2.52 per RR category level, -2.77 per SBP category level, -1.08 for male gender, 0.18 per year of age, 4.98 for driver vs. rear passengers, 4.83 for no seatbelt use, 13.52 for indeterminable seatbelt use, 5.07 for no airbag deployment, and 0.0003 per (km/h)(2) velocity change (all p<0.002).

CONCLUSION

This study in victims of MVAs demonstrated that injury severity (NISS) was concurrently and independently predicted by poor pre-hospital physiologic status, increasing age and female gender, and several mechanistic measures of localised and generalised trauma energy. Our findings underscore the need for precise information from the site of trauma, to reduce undertriage, target diagnostic efforts, and anticipate need for high-level care and rehabilitative resources.

Separate mechanisms act concurrently to shed and release the prion protein from the cell

The cellular prion protein (PrP (C) ) is attached to the cell membrane via its glycosylphosphatidylinositol (GPI)-anchor and is constitutively shed into the extracellular space. Here, three different mechanisms are presented that concurrently shed PrP (C) from the cell. The fast α-cleavage released a N-terminal fragment (N1) into the medium and the extreme C-terminal cleavage shed soluble full-length (FL-S) PrP and C-terminally cleaved (C1-S) fragments outside the cell. Also, a slow exosomal release of full-length (FL) and C1-fragment (C1) was demonstrated. The three separate mechanisms acting simultaneously, but with different kinetics, have to be taken into consideration when elucidating functional roles of PrP (C) and also when processing of PrP (C) is considered as a target for intervention in prion diseases. Further, in this study it was shown that metalloprotease inhibitors affected the extreme C-terminal cleavage and shedding of PrP (C) . The metalloprotease inhibitors did not influence the α-cleavage or the exosomal release. Taken together, these results are important for understanding the different mechanisms acting in parallel in the shedding and cleavage of PrP (C) .

Polymorphisms and variants in the prion protein sequence of European moose (Alces alces), reindeer (Rangifer tarandus), roe deer (Capreolus capreolus) and fallow deer (Dama dama) in Scandinavia

The prion protein (PrP) sequence of European moose, reindeer, roe deer and fallow deer in Scandinavia has high homology to the PrP sequence of North American cervids. Variants in the European moose PrP sequence were found at amino acid position 109 as K or Q. The 109Q variant is unique in the PrP sequence of vertebrates. During the 1980s a wasting syndrome in Swedish moose, Moose Wasting Syndrome (MWS), was described. SNP analysis demonstrated a difference in the observed genotype proportions of the heterozygous Q/K and homozygous Q/Q variants in the MWS animals compared with the healthy animals. In MWS moose the allele frequencies for 109K and 109Q were 0.73 and 0.27, respectively, and for healthy animals 0.69 and 0.31. Both alleles were seen as heterozygotes and homozygotes. In reindeer, PrP sequence variation was demonstrated at codon 176 as D or N and codon 225 as S or Y. The PrP sequences in roe deer and fallow deer were identical with published GenBank sequences.

Standard basic life support vs. continuous chest compressions only in out-of-hospital cardiac arrest

BACKGROUND

The importance of ventilations after cardiac arrest has been much debated recently and eliminating mouth-to-mouth ventilations for bystanders has been suggested as a means to increase bystander cardiopulmonary resuscitation (CPR). Standard basic life support (S-BLS) is not documented to be superior to continuous chest compressions (CCC).

METHODS

Retrospective, observational study of all non-traumatic cardiac arrest patients older than 18 years between May 2003 and December 2006 treated by the community-run emergency medical service (EMS) in Oslo. Outcome for patients receiving S-BLS was compared with patients receiving CCC. All Utstein characteristics were registered for both patient groups as well as for patients not receiving any bystander CPR by reviewing Ambulance run sheets, Utstein forms and hospital records. Method of bystander CPR as well as dispatcher instruction was registered by first-arriving ambulance personnel.

RESULTS

Six-hundred ninety-five out of 809 cardiac arrests in our EMS were included in this study. Two-hundred eighty-one (40%) received S-CPR and 145 (21%) received CCC. There were no differences in outcome between the two patient groups, with 35 (13%) discharged with a favourable outcome for the S-BLS group and 15 (10%) in the CCC group (P=0.859). Similarly, there was no difference in survival subgroup analysis of patients presenting with initial ventricular fibrillation/ventricular tachycardia after witnessed arrest, with 32 (29%) and 10 (28%) patients discharged from hospital in the S-BLS and CCC groups, respectively (P=0.972).

CONCLUSIONS

Patients receiving CCC from bystanders did not have a worse outcome than patients receiving standard CPR, even with a tendency towards a higher distribution of known negative predictive features.

The evolutionary trajectory of the mating-type (mat) genes in Neurospora relates to reproductive behavior of taxa

Background

Comparative sequencing studies among a wide range of taxonomic groups, including fungi, have led to the discovery that reproductive genes evolve more rapidly than other genes. However, for fungal reproductive genes the question has remained whether the rapid evolution is a result of stochastic or deterministic processes. The mating-type (mat) genes constitute the master regulators of sexual reproduction in filamentous ascomycetes and here we present a study of the molecular evolution of the four mat-genes (mat a-1, mat A-1, mat A-2 and mat A-3) of 20 Neurospora taxa.

Results

We estimated nonsynonymous and synonymous substitution rates of genes to infer their evolutionary rate, and confirmed that the mat-genes evolve rapidly. Furthermore, the evolutionary trajectories are related to the reproductive modes of the taxa; likelihood methods revealed that positive selection acting on specific codons drives the diversity in heterothallic taxa, while among homothallic taxa the rapid evolution is due to a lack of selective constraint. The latter finding is supported by presence of stop codons and frame shift mutations disrupting the open reading frames of mat a-1, mat A-2 and mat A-3 in homothallic taxa. Lower selective constraints of mat-genes was found among homothallic than heterothallic taxa, and comparisons with non-reproductive genes argue that this disparity is not a nonspecific, genome-wide phenomenon.

Conclusion

Our data show that the mat-genes evolve rapidly in Neurospora. The rapid divergence is due to either adaptive evolution or lack of selective constraints, depending on the reproductive mode of the taxa. This is the first instance of positive selection acting on reproductive genes in the fungal kingdom, and illustrates how the evolutionary trajectory of reproductive genes can change after a switch in reproductive behaviour of an organism.

Characterization of proteinase K-resistant N- and C-terminally truncated PrP in Nor98 atypical scrapie

An increasing number of scrapie cases with atypical characteristics, designated Nor98, have recently been recognized. Here, the proteinase K (PK)-resistant prion protein (PrP) fragments from two Swedish cases of Nor98 atypical scrapie have been characterized. The prominent, fast-migrating band in the distinct Nor98 Western immunoblot electrophoretic profile was determined to be of 7 kDa in size and was accordingly designated Nor98-PrP7. The antigenic composition of Nor98-PrP7, as assayed by a panel of anti-PrP antibodies, revealed that this fragment comprised a mid-region of PrP from around aa 85 to 148. N- and C-terminally truncated fragments spanning the mid-region of PrP have only been observed in the genetic prion disorder Gerstmann–Sträussler–Scheinker disease. It is shown here that the long-term PK resistance of Nor98-PrP7 is reduced compared with that of PrPresin classical scrapie. Enzymic deglycosylation did not change the distinct electrophoretic profile of Nor98-PrP7. A previously unidentified, PK-resistant, C-terminal PrP fragment of around 24 kDa was detected and its PK resistance was investigated. After deglycosylation, this fragment migrated as a 14 kDa polypeptide and was designated PrP-CTF14. Antigenic determination and the size of 14 kDa suggested a fragment spanning approximately aa 120–233. The existence of two PK-resistant PrP fragments, Nor98-PrP7 and PrP-CTF14, that share an overlapping region suggests that at least two distinct PrP conformers with different PK-resistant cores are present in brain extracts from Nor98-affected sheep. The structural gene of PrP in three Nor98-affected sheep was analysed, but no mutations were found that could be correlated to the aberrant PK-resistant profile observed.

Arterial blood gases with 700 ml tidal volumes during out-of-hospital CPR

The optimal tidal and minute ventilation during cardiopulmonary resuscitation (CPR) is not known. In the present study seven adult, non-traumatic, out-of-hospital cardiac arrest patients were intubated and mechanically ventilated at 12 min(-1) with 100% oxygen and a tidal volume of 700 ml (10 +/- 2 ml kg(-1)). Arterial blood gas samples were analysed after 6-8 min of unsuccessful resuscitation and mechanical ventilation. Mean PaCO2 was 5.2 +/- 1.3 kPa and mean PaO2 30.7 +/- 17.2 kPa. The patient with the highest (14 ml kg(-1)) and lowest (8 ml kg(-1)) tidal volumes per kg had the lowest and highest PaCO2 values of 2.6 and 6.8 kPa, respectively. Linear regression analysis confirmed a significant correlation between arterial pCO2 and tidal volume in ml/kg, r2 = 0.87. We conclude that aiming for an estimated ventilation of 10 ml kg(-1) tidal volume at frequency of 12 min(-1) might be expected to achieve normocapnia during ALS.

Oxygen delivery and return of spontaneous circulation with ventilation:compression ratio 2:30 versus chest compressions only CPR in pigs

The need for rescue breathing during the initial management of sudden cardiac arrest is currently being debated and reevaluated. The present study was designed to compare cerebral oxygen delivery during basic life support (BLS) by chest compressions only with chest compressions plus ventilation in pigs with an obstructed airway mimicked by a valve hindering passive inhalation. Resuscitability was then studied during the subsequent advanced life support (ALS) period. After 3 min of untreated ventricular fibrillation (VF) BLS was started. The animals were randomised into two groups. One group received chest compressions only. The other group received ventilations and chest compressions with a ratio of 2:30. A gas mixture of 17% oxygen and 4% carbon dioxide was used for ventilation during BLS. After 10 min of BLS, ALS was provided. All six pigs ventilated during BLS attained a return of spontaneous circulation (ROSC) within the first 2 min of advanced cardiopulmonary resuscitation (CPR) compared with only one of six compressions-only pigs. While all except one compressions-only animal achieved ROSC before the experiment was terminated, the median time to ROSC was shorter in the ventilated group. With a ventilation:compression ratio of 2:30 the arterial oxygen content stayed at 2/3 of normal, but with compressions-only, the arterial blood was virtually desaturated with no arterio-venous oxygen difference within 1.5-2 min. Haemodynamic data did not differ between the groups. In this model of very ideal BLS, ventilation improved arterial oxygenation and the median time to ROSC was shorter. We believe that in cardiac arrest with an obstructed airway, pulmonary ventilation should still be strongly recommended.

Quality of CPR with three different ventilation:compression ratios

Current adult basic cardiopulmonary resuscitation (CPR) guidelines recommend a 2:15 ventilation:compression ratio, while the optimal ratio is unknown. This study was designed to compare arterial and mixed venous blood gas changes and cerebral circulation and oxygen delivery with ventilation:compression ratios of 2:15, 2:50 and 5:50 in a model of basic CPR. Ventricular fibrillation (VF) was induced in 12 anaesthetised pigs, and satisfactory recordings were obtained from 9 of them. A non-intervention interval of 3 min was followed by CPR with pauses in compressions for ventilation with 17% oxygen and 4% carbon dioxide in a randomised, cross-over design with each method being used for 5 min. Pulmonary gas exchange was clearly superior with a ventilation:compression ratio of 2:15. While the arterial oxygen saturation stayed above 80% throughout CPR for 2:15, it dropped below 40% during part of the ventilation:compression cycle for both the other two ratios. On the other hand, the ratio 2:50 produced 30% more chest compressions per minute than either of the two other methods. This resulted in a mean carotid flow that was significantly higher with the ratio of 2:50 than with 5:50 while 2:15 was not significantly different from either. The mean cerebrocortical microcirculation was approximately 37% of pre-VF levels during compression cycles alone with no significant differences between the methods. The oxygen delivery to the brain was higher for the ratio of 2:15 than for either 5:50 or 2:50. In parallel the central venous oxygenation, which gives some indication of tissue oxygenation, was higher for the ratio of 2:15 than for both 5:50 and 2:50. As the compressions were done with a mechanical device with only 2-3 s pauses per ventilation, the data cannot be extrapolated to laypersons who have great variations in quality of CPR. However, it might seem reasonable to suggest that basic CPR by professionals should continue with ratio of 2:15 at present if it can be shown that similar brief pauses for ventilation can be achieved in clinical practice.

Dispatcher-assisted cardiopulmonary resuscitation. An evaluation of efficacy amongst elderly

Bystander cardiopulmonary resuscitation (CPR) increases survival rates. The largest group of cardiac arrest patients are men over the age of 60 in the home, and the most probable potential CPR provider is an older woman who is not likely to have received CPR training. One method to increase the percentage of bystander-initiated CPR in this setting is for CPR instruction to be provided by nurse dispatchers via telephone. Two male and 18 female volunteers with a median age of 78 years and no previous CPR experience performed 9 min of telephone assisted CPR on a manikin. They were randomised to receive telephone instructions in chest compressions alone or standard CPR including mouth-to-mouth ventilation. Variables were registered by a recording manikin, visual observations, and video and audiotape recordings. The median period from dispatcher contact until continuous CPR was significantly longer for standard instructions than for compression only, 4.9 versus 3.4 min, and fewer chest compressions were provided during the 9 min test period, median 124 versus 334 compressions. In both groups the overall CPR performance was of very poor quality, and unlikely to have affected outcome in a real situation. Other telephone assisted CPR scripts should be tested in this potential bystander group.

Effectiveness of ventilation-compression ratios 1:5 and 2:15 in simulated single rescuer paediatric resuscitation

Current guidelines for paediatric basic life support (BLS) recommend a ventilation-compression ratio of 1:5 during child resuscitation compared with 2:15 for adults, based on the consensus that ventilation is more important in paediatric than in adult BLS. We hypothesized that the ratio 2:15 would provide the same minute ventilation as 1:5 during single-rescuer paediatric BLS due to the reduced time required to change between ventilations and compressions. Fourteen lay rescuers were trained with both ratios and thereafter performed single rescuer BLS for approximately 4 min with each of the two ratios in random order on a child-sized manikin with a built-in respiratory monitor. Quality of chest compressions was assessed by measurement of the rate, depth and position. There were no significant differences in tidal volumes or minute ventilation between the ratios. Nearly all chest compressions were within acceptable limits for depth and place with both methods, but the mean number of chest compressions per minute was 48+/-15% greater with ratio 2:15. In conclusion, there was no difference in ventilation, but nearly one and a half times as many compressions with a ratio of 2:15 than 1:5 for lay rescuers during single rescuer paediatric CPR. In order to simplify CPR training for laypersons, we recommend a 2:15 ratio for both single- and two-person, adult and paediatric layperson BLS.

An automated voice advisory manikin system for training in basic life support without an instructor. A novel approach to CPR training

Twenty-four paramedic students with previous basic life support training were randomised, performing cardiopulmonary resuscitation (CPR) on a manikin for 3 min without any feedback followed by 3 min of CPR with audio feedback from the manikin after a 2-min break, or vice versa. A computer recorded information on timing, ventilation flow rates and volumes and all movements of the sternum of the manikin. The software allowed acceptable limits to be set for all ventilation and compression/release variables giving appropriate on-line audio feedback according to these settings from among approximately 40 pre-recorded messages. Students who started without feedback significantly improved after feedback in terms of the median percentage of correct inflations (from 2 to 64%), with most inflations being rapid before feedback (94%), compressions of correct depth (from 32 to 92%), and the duration of compressions in the duty cycle (from 41 to 44%). There were no problems with the median compression rate, sternal release during decompressions, or the hand position, even before feedback. There were no significant differences in any variables with and without feedback for the students who started with feedback, or between the audio feedback periods of the two groups. It is concluded that this automated voice advisory manikin system, a novel approach to basic CPR training, caused an immediate improvement in the skills performance of paramedic students.

Arterial blood-gases with 500- versus 1000-ml tidal volumes during out-of-hospital CPR

The correct tidal volume during cardiopulmonary resuscitation (CPR) is presently debated. While the European Resuscitation Council (ERC) and American Heart Association (AHA) previously recommended a tidal volume of 800-1200 ml, the ERC has recently reduced this to 400-600 ml. In a prospective, randomised study of 17 non-traumatic out-of-hospital cardiac arrest patients intubated and mechanically ventilated 12 min(-1) with 100% oxygen, we have therefore compared arterial blood gases generated with tidal volumes of 500 and 1000 ml. Mean time from cardiac arrest to arrival of the ambulance was 13+/-8 and 14+/-8 min in the two groups, respectively. Arterial blood samples were taken percutaneously 5 and 10-15 min after onset of the mechanical ventilation and analysed instantly. Pa(CO(2)) was significantly higher for a tidal volume of 500 than 1000 ml at both 5 and 10-15 min, 7.48+/-2.23 versus 3.70+/-0.83 kPa (P=0.002) and 7. 45+/-1.19 versus 3.98+/-1.58 kPa (P<0.001). The pH was lower for 500 than 1000 ml at 10-15 min, 7.01+/-0.10 versus 7.20+/-0.17 (P=0.034), with a strong trend in the same direction at 5 min (P=0.06). There was adequate oxygenation with no differences in Pa(O(2)) or BE at any time between the two groups, and no significant differences in any blood gas variables between the 5- and 10-15-min samples. We conclude that arterial normocapnia is not achieved with either tidal volume during advanced life support with non-rebreathing ventilation at 12 min(-1). What ventilation volume is required for CO(2) removal and oxygenation during basic life support with mouth-to-mouth ventilation cannot be extrapolated from the present data. In that situation the risk of gastric inflation, regurgitation and aspiration must also be taken into account.

Airway pressure with chest compressions versus Heimlich manoeuvre in recently dead adults with complete airway obstruction

In a previous case report a standard chest compression successfully removed a foreign body from the airway after the Heimlich manoeuvre had failed. Based on this case, standard chest compressions and Heimlich manoeuvres were performed by emergency physicians on 12 unselected cadavers with a simulated complete airway obstruction in a randomised crossover design. The mean peak airway pressure was significantly lower with abdominal thrusts compared to chest compressions, 26.4+/-19.8 cmH(2)O versus 40.8+/-16.4 cmH(2)O, respectively (P=0.005, 95% confidence interval for the mean difference 5.3-23.4 cmH(2)O). Standard chest compressions therefore have the potential of being more effective than the Heimlich manoeuvre for the management of complete airway obstruction by a foreign body in an unconscious patient. Removal of the Heimlich manoeuvre from the resuscitation algorithm for unconscious patients with suspected airway obstruction will also simplify training.

Active compression-decompression cardiopulmonary resuscitation: a population-based, prospective randomised clinical trial in out-of-hospital cardiac arrest

Different mechanical devices have been developed to improve cardiopulmonary resuscitation (CPR). The aim of this study was to evaluate active compression-decompression (ACD) CPR applied by Emergency Medical Service (EMS) in a defined population. The Trondheim region EMS (population 154,000) employs simultaneous paramedic and physician response. Upon decision to treat, patients with cardiac arrest of presumed cardiac origin were allocated to ACD CPR (CardioPump) or standard CPR by drawing a random number tag. Outcome in each patient was determined on a 5 point ordinal scale (no clinical improvement = 1, survival to discharge = 5). In 4 years, CPR was attempted in a total of 431 cardiac arrests, 54 patients (13%) survived to discharge; 302 patients with similar baseline characteristics were randomised. The prevalence of bystander CPR was 57% and the median call-arrival interval 9 min. By intention to treat, the mean score in the standard CPR group was 2.51 and 17/145 patients (12%) survived. The mean score in the ACD CPR group was 2.53 (P = 0.9) and 20/157 patients (13%) survived. Cerebral outcome was similar in the two groups. Among the 145 ACD patients, the technique was successfully applied in 110, found inapplicable in 35 and in seven patients chest compressions were unnecessary. This is the largest, single-centre, randomised, population based study of ACD CPR in out-of-hospital cardiac arrest to date. Even when considering a wider outcome spectrum than crude survival, we found no evidence of clinical benefit. In a quarter of cases ACD CPR was inapplicable, further limiting its potential usefulness.

Improved haemodynamics with increased compression-decompression rates during ACD-CPR in pigs

The haemodynamic effects of variations in the compression-decompression frequency, 60, 90 and 120 min(-1) during ACD-CPR, were tested in a randomized cross-over design during ventricular fibrillation (VF) in 12 anaesthetized pigs (17-22 kg) using an automatic hydraulic chest compression-decompression device. There were significant increases with increasing frequency for mean (+/- S.D.) carotid blood flow (17 +/- 5, 25 +/- 9 and 36 +/- 12 ml min(-1), transit time flow probe), cerebral blood flow (17 +/- 7, 30 +/- 17 and 40 +/- 13 ml min(-1) 100 g(-1), radionuclide microspheres) and mean aortic pressure (34 +/- 8, 37 +/- 10 and 43 +/- 7 mmHg), respectively. Myocardial blood flow (radionuclide microspheres) and diastolic coronary perfusion pressure, CPP, increased significantly from 60 to 90 min(-1) with no further significant increase to 120 min(-1) (28 +/- 13, 46 +/- 23 and 49 +/- 19 ml min(-1) 100 g(-1) and 25 +/- 8, 31 +/- 11 and 32 +/- 9 mmHg, respectively). Renal and hepatic blood flow also increased with increasing rate. No significant differences in the expired CO2 levels were observed. In conclusion increasing the compression-decompression frequency from 60 to 90 and 120 min(-1) improved the haemodynamics during ACD-CPR in a pig model with VF.

Effect of different compression--decompression cycles on haemodynamics during ACD-CPR in pigs

The haemodynamic effects of variations in the relative duration of the compression and active decompression (4 cm/2 cm) during active compression-decompression cardiopulmonary resuscitation (ACD-CPR), 30/70, 50/50 and 70/30, were tested in a randomized cross-over design during ventricular fibrillation in seven anaesthetized pigs (17-23 kg) using an automatic hydraulic chest compression-decompression device. Duty cycles of 50/50 and 70/30 gave significantly higher values than 30/70 for mean carotid blood flow (32 and 36 vs. 21 ml min-1, transit time flow probe, cerebral blood flow (30 and 34 vs. 19, radionuclide microspheres), mean aortic pressure (35 and 41 vs. 29 mmHg) and mean right atrial pressure (24 and 33 vs. 16 mmHg). A higher mean aortic, mean right atrial and mean left ventricular pressure for 70/30 were the only significant differences between 50/50 and 70/30. There were no differences in myocardial blood flow (radionuclide microspheres) or coronary perfusion pressure (CPP, aortic-right atrial pressure) between the three different duty cycles. CPP was positive in both the early and late compression period and during the whole decompression period. The expired CO2 was significantly higher with 70/30 than 30/70 during the compression phase of ACD-CPR. Beyond that no significant differences in the expired CO2 levels were observed. In conclusion a reduction of the compression period to 30% during ACD-CPR reduced the cerebral circulation, the mean aortic and right atrial pressures with no effect on the myocardial blood flow of varying the compression-decompression cycle.

Impact of a child first aid wall calendar on lay people's skills and knowledge of infant CPR

The aim of the study was to evaluate whether mass-mailing of a 12-month wall calendar which focused on child and infant safety and first aid treatment had any educational effect on lay people. The calendar included algorithms for removal of a foreign body from the airways and infant and child CPR. The knowledge and skills in these procedures were tested in two groups using a previously validated check-list before and after the introduction of the calendar. One group received the calendar by mass mailing, free-of-charge. Six months after calendar distribution the mean result for 52 persons tested was 18% correct, not different from the 19% correct for 65 persons tested before calendar distribution. The other group received the calendar as part of an internal company campaign focusing on infant and child safety with a possibility for borrowing a baby manikin, but with no instruction involved. In this group the mean result improved significantly from 27% precalendar (n = 57) to 47% (n = 125) (P < 0.001) 1 week after calendar distribution with a significant reduction to 38% (n = 52) (P = 0.004) 6 months later, still significantly better than precalendar (P = 0.004). Test persons younger than 50 years old scored better than those older than 50 years (39 vs. 22%, P < 0.001), and the test persons scored better if they had been tested previously (44 vs. 35%, P = 0.04) or had practised with a baby manikin (45 vs. 35%, P = 0.02). Whether the test persons had children 0-8 years old or not, did not affect the results. In conclusion the calendar had no educational effect when distributed by mail, but a safety campaign which included distribution of the calendar and a possibility to borrow a manikin had a positive influence on the first aid skills and knowledge of lay people. Mass mailing of CPR or other first aid material free-of-charge does not seem to further the goal of increasing the rate and proficiency of bystander interventions to save lives.

Quality of mechanical, manual standard and active compression-decompression CPR on the arrest site and during transport in a manikin model

The quality of mechanical CPR (M-CPR) was compared with manual standard CPR (S-CPR) and active compression-decompression CPR (ACD-CPR) performed by paramedics on the site of a cardiac arrest and during manual and ambulance transport. Each technique was performed 12 times on manikins using teams from a group of 12 paramedic students with good clinical CPR experience using a random cross-over design. Except for some lost ventilations the CPR effort using the mechanical device adhered to the European Resuscitation Council guidelines, with an added time requirement of median 40 s for attaching the device compared with manual standard CPR. Throughout the study, in comparison with mechanical CPR the quality of CPR with either manual method was significantly worse. In particular, there were considerable individual variations during stretcher transport. With S-CPR and ACD-CPR the median compression times were 38 and 31%, significantly lower than the recommended 50%, and 46-98% of the decompression efforts with ACD-CPR were too weak, particularly during transport on the stairs. With both manual methods, there were no significant differences in the CPR effort between the site of the arrest and the ambulance transport. However, compression rates were reduced and became more erratic during stretcher transport to the ambulance. When walking horizontally, a median of 19% of S-CPR compressions and 84% of ACD-CPR compressions were to weak. On the stairs, 68% of S-CPR compressions and 100% of ACD-CPR compressions were too weak. In conclusion, when evaluated on a manikin, in comparison with manual standard and ACD-CPR, mechanical CPR adhered more closely to ERC guidelines. This was particularly true when performing CPR during transport on a stretcher.

Active compression-decompression cardiopulmonary resuscitation (ACD-CPR) compared with standard CPR in a manikin model--decompression force, compression rate, depth and duration

During active compression-decompression cardiopulmonary resuscitation (ACD-CPR), the rescuer applies traction to the chest between compressions. Under experimental conditions, cardiac output increases, possibly through accentuated intrathoracal pressure fluctuations. ACD-CPR requires specific training and may be more complex to perform than standard CPR. The aim of this study was to characterize ACD-CPR performance compared with standard CPR by emergency care providers; in terms of decompression force, compression rate, depth and duration. Thirty-three ambulance paramedics were studied while performing standard CPR and ACD-CPR with the Ambu Cardiopump on a specially designed transducer-equipped manikin 9 months following initial training. The order of CPR performance was determined randomly by cross-over design. Performance data were recorded by a computer. The 2-min average active decompression force was 9.3 kg (interquartile range 2.5-15.3 kg) and six subjects (18%) met the manufacturers recommendation of 10-15 kg. External chest compression (ECC) rate decreased from 85 (70-101) to 76 (63-88) min-1 (P < 0.001), ECC depth decreased from 54 (50-58) to 45 (39-48) mm (P < 0.001) and compression duration from 40 (35-45) to 31% (28-33%) (P < 0.001) upon change from standard CPR to ACD-CPR. We conclude that the recommended level of decompression force was achieved by less than one fifth of study subjects. ACD-CPR when compared with standard CPR causes a consistent and significant reduction of compression rate, depth and duration. These are all factors of possible clinical significance. Training in ACD-CPR should address this issue, with special emphasis on optimal decompression force and ECC rate.

Intubation with laryngoscope versus transillumination performed by paramedic students on manikins and cadavers

Seventeen paramedic students, all of whom are novice intubators, performed laryngoscopic and Trachlight intubation after supervised training for 90 min on two manikins (Laerdal, AMBU) and 30 min on cadavers. A maximum of two intubation attempts lasting a maximum 30 s each were permitted on each manikin and the cadaver. The time for confirming tube placement by auscultation and securing the tube was added. Laryngoscopic intubation was successful on cadavers and both manikins in 94-100% of the trials. Intubation with the Trachlight was 100% successful in the Laerdal manikin, but significantly lower than with the laryngoscope in the AMBU manikin (65%), and in cadavers (50%). The mean intubation time was significantly longer (30-44 s) with the Trachlight compared with laryngoscopic intubation (10-23 s) in both manikins and cadavers. The present results do not indicate that intubation with the Trachlight is an improvement upon laryngoscopic intubation for novices.

Active compression-decompression cardiopulmonary resuscitation--instructor and student manual for teaching and training. Part I: The workshop

In an attempt to standardize the teaching and training of active compression-decompression cardiopulmonary resuscitation (ACD-CPR), a group of leading emergency physicians, cardiologists, anesthesiologists, paramedics and nurses with practical, theoretical, educational, and scientific experience in the subject met in June 1995. The group was called The International Working Group of Teaching and Training Active Compression-Decompression CPR. The group was 'born' as a result of the first International Conference of Active Compression-Decompression CPR held in Copenhagen in March 1995. The following paper describes the background, development and text of and ACD-CPR course manual for both students and instructors.

A comparison of prolonged manual and mechanical external chest compression after cardiac arrest in dogs

The effects of manual and a new mechanical chest compression device (Heartsaver 2000) during prolonged CPR with respect to haemodynamics and outcome were tested in a prospective, randomized, controlled experimental trial during ventricular fibrillation in 12 dogs of 9-13 kg body weight after 1 min of cardiac arrest. During the first 10 min of CPR the dogs were resuscitated according to the Basic Life Support (BLS) algorithm, followed by 20 min of Advanced Life Support (ALS) algorithm. After 30 min of CPR both manual and mechanical CPR groups were resuscitated following a standardized ALS protocol. During CPR, coronary perfusion pressure and end tidal CO2 were greater with mechanical CPR. All animals were successfully resuscitated and neurological deficit scores were not different. The CPR trauma score was less in the mechanical group. Mechanical external chest compression provided better haemodynamics than the manual technique, though outcome did not differ. Both optimally performed manual and mechanical techniques produce flow sufficient to maintain organ viability for 30 min of CPR after a 1 min arrest interval.

Future directions for resuscitation research. II. External cardiopulmonary resuscitation basic life support

In sudden cardiac deaths outside hospitals, the present performance of external cardiopulmonary resuscitation-basic life support (CPR-BLS), as a bridge to advanced life support (ALS) attempts for restoration of spontaneous circulation (ROSC), still yields suboptimal results. Therefore, future education research should develop more effective, simpler and quicker ways to enable everyone to acquire the necessary BLS skills. Individualized self-training by lay persons is being revived. Although airway control and direct mouth-to-mouth ventilation skills are difficult to acquire, they must continue to be taught to the lay public and health professionals, primarily for use on relatives and friends where infection risk is not a problem. In children and trauma victims, steps A and B alone may be lifesavers. The best way to ventilate and oxygenate during the initiation of brief external CPR-BLS should be re-evaluated. There is a great difference between animals and humans in the behavior of the airway and thorax during coma, and thus in the need for added positive pressure ventilation. During chest compressions in humans, steps A and B are needed. Details deserve re-evaluation. The low perfusion pressures (borderline blood flows) produced by standard external CPR remain the most serious limitation of this method. In spite of extensive efforts so far, novel laboratory research to remedy this limitation is important for the development of more effective emergency artificial circulation. The results of such studies are greatly influenced by different details in animal models. Active compression-decompression (ACD) external CPR, also called 'push-pull' CPR, with a plunger-type device used by hand or a machine, and intermittent abdominal compression (IAC) external CPR are both promising modifications of standard external CPR. Both need further experimental and clinical clarification. For BLS, developing a more effective purely manual CPR-BLS method for help in rapid ROSC should be given high priority. Portable external CPR machines need improvements. They will serve for bridging ROSC-resistant cases through transport and ALS attempts, primarily by freeing the hands of health professionals for more effective sophisticated ALS measures.