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

Intra-arrest blood-based biomarkers for out-of-hospital cardiac arrest: A scoping review

Objective

Blood-based biomarkers play a central role in the diagnosis and treatment of critically ill patients, yet none are routinely measured during the intra-arrest phase of out-of-hospital cardiac arrest (OHCA). Our objective was to describe methodological aspects, sources of evidence, and gaps in research surrounding intra-arrest blood-based biomarkers for OHCA.

Methods

We used scoping review methodology to summarize existing literature. The protocol was designed a priori following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews. Inclusion criteria were peer-reviewed scientific studies on OHCA patients with at least one blood draw intra-arrest. We excluded in-hospital cardiac arrest and animal studies. There were no language, date, or study design exclusions. We conducted an electronic literature search using PubMed and Embase and hand-searched secondary literature. Data charting/synthesis were performed in duplicate using standardized data extraction templates.

Results

The search strategy identified 11,834 records, with 118 studies evaluating 105 blood-based biomarkers included. Only eight studies (7%) had complete reporting. The median number of studies per biomarker was 2 (interquartile range 1-4). Most studies were conducted in Asia (63 studies, 53%).  Only 22 studies (19%) had blood samples collected in the prehospital setting, and only six studies (5%) had samples collected by paramedics. Pediatric patients were included in only three studies (3%). Out of eight predefined biomarker categories of use, only two were routinely assessed: prognostic (97/105, 92%) and diagnostic (61/105, 58%).

Conclusions

Despite a large body of literature on intra-arrest blood-based biomarkers for OHCA, gaps in methodology and knowledge are widespread.

Arterial Blood Gases and Arterial Lines in the Prehospital Setting: A Systematic Literature Review and Survey of Current United Kingdom Helicopter Emergency Medical Services

OBJECTIVE

Prehospital guidelines state that monitoring should match in-hospital standards, but consensus on the use of arterial blood gases (ABGs) and arterial lines remains unclear. The aim was to perform a systematic literature review and survey of UK helicopter emergency medical services (HEMS) use and perceptions of ABGs and arterial lines.

METHODS

A systematic literature review was conducted for arterial lines and ABGs and prehospital care. Additionally, two questionnaires were distributed to all UK HEMS (questionnaire 1: current clinical practice and questionnaire 2: clinicians' opinions).

RESULTS

From 1,028 results, 13 studies (10 ABGs and 3 arterial lines) were included, demonstrating it is feasible to obtain ABGs and place arterial lines in the prehospital setting. There were concerns about practical difficulties for ABGs and the time taken for arterial lines. Survey responses were obtained from all UK HEMS (N = 22). Six services carry equipment for performing ABGs and nine services for arterial lines. Clinicians expressed concerns relating to the time taken to perform both procedures, but most believed it would allow better monitoring and more targeted treatment.

CONCLUSION

The evidence of benefit for both procedures remains poor. Overall, there may be clinical benefits, but these are likely to be patient specific and require further investigation.

Reliability of mechanical ventilation during continuous chest compressions: a crossover study of transport ventilators in a human cadaver model of CPR

Background

Previous studies have stated that hyperventilation often occurs in cardiopulmonary resuscitation (CPR) mainly due to excessive ventilation frequencies, especially when a manual valve bag is used. Transport ventilators may provide mandatory ventilation with predetermined tidal volumes and without the risk of hyperventilation. Nonetheless, interactions between chest compressions and ventilations are likely to occur. We investigated whether transport ventilators can provide adequate alveolar ventilation during continuous chest compression in adult CPR.

Methods

A three-period crossover study with three common transport ventilators in a cadaver model of CPR was carried out. The three ventilators ‘MEDUMAT Standard²’, ‘Oxylog 3000 plus’, and ‘Monnal T60’ represent three different interventions, providing volume-controlled continuous mandatory ventilation (VC-CMV) via an endotracheal tube with a tidal volume of 6 mL/kg predicted body weight. Proximal airflow was measured, and the net tidal volume was derived for each respiratory cycle. The deviation from the predetermined tidal volume was calculated and analysed. Several mixed linear models were calculated with the cadaver as a random factor and ventilator, height, sex, crossover period and incremental number of each ventilation within the period as covariates to evaluate differences between ventilators.

Results

Overall median deviation of net tidal volume from predetermined tidal volume was − 21.2 % (IQR: 19.6, range: [− 87.9 %; 25.8 %]) corresponding to a tidal volume of 4.75 mL/kg predicted body weight (IQR: 1.2, range: [0.7; 7.6]). In a mixed linear model, the ventilator model, the crossover period, and the cadaver’s height were significant factors for decreased tidal volume. The estimated effects of tidal volume deviation for each ventilator were − 14.5 % [95 %-CI: −22.5; −6.5] (p = 0.0004) for ‘Monnal T60’, − 30.6 % [95 %-CI: −38.6; −22.6] (p < 0.0001) for ‘Oxylog 3000 plus’ and − 31.0 % [95 %-CI: −38.9; −23.0] (p < 0.0001) for ‘MEDUMAT Standard²’.

Conclusions

All investigated transport ventilators were able to provide alveolar ventilation even though chest compressions considerably decreased tidal volumes. Our results support the concept of using ventilators to avoid excessive ventilatory rates in CPR. This experimental study suggests that healthcare professionals should carefully monitor actual tidal volumes to recognise the occurrence of hypoventilation during continuous chest compressions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13049-021-00921-2.

Effect of tidal volume on gas exchange during rescue ventilation

Tidal volume V_T required for mouth-to-mouth (MTM) and bag-valve-mask (BVM) rescue ventilation remains debatable owing to differences in physiology and end-point objectives. Analysis of gas transport may clarify minimum necessary V_T and its determinants. Alveolar and arterial O₂ and CO₂ responses to MTM and air BVM ventilation for V_T between 0.4 and 1.2 liters were computed using a model of gas exchange that incorporates inspired gas concentrations, airway dead space, cardiac output, pulmonary shunt, blood gas dissociation curves, tissue compartments, and metabolic rate. Parameters were adjusted to match published human data. Steady state arterial oxygen saturation reached plateaus at V_T above 0.7 liters with MTM and 0.6 liters with air ventilation at 12 breaths per minute. Increasing shunt shifted oxygenation plateaus downward, but larger tidal volumes did not improve oxygen saturation. Carbon dioxide retention occurred at V_T below 2.3 liters for MTM ventilation and 0.6 liters for air ventilation. Results establish a physiological foundation for tidal volume requirements during resuscitation.

Use of a Load Distributing Band Device (with Ventilation Prompts) during Cardiopulmonary Resuscitation

Introduction

Over-ventilation can compromise coronary perfusion pressures during cardiopulmonary resuscitation (CPR) and should be minimised. We compared ventilations during manual and mechanical (load-distributing band - LDB) CPR, which gives ventilation prompts. Our primary objective was to compare the ventilation rate between manual CPR and LDB-CPR.

Method

This was a phased, non-randomised study at a tertiary hospital emergency department. All out-of-hospital, non-traumatic cardiac arrest adult patients during the study period from February 2007 till July 2008 were eligible. Pregnant females and patients aged less than 18 years of age were excluded. Ventilation rates in the first and second 5 minutes segments were recorded. Over-ventilation was defined as ventilation rate above 12 breaths per minute. All data analyses were performed with SPSS, version 17.0. Mean differences with 95% confidence interval (CI) were compared between the 2 treatment groups.

Results

From February 2007 till August 2007, there were 29 patients with manual CPR; and from September 2007 till July 2008, there were 62 with LDB-CPR. In the first 5 minutes of CPR, the proportion of patients that were over-ventilated, was 27.6% (manual) and 4.8% (LDB) (difference = 22.7%; 95% CI: 3.5-46.4%). In the next 5 minutes, the proportion of patients that were over-ventilated was 37.9% and 1.6% for manual and mechanical CPR respectively (difference = 36.3%; 95% CI: 16.5-58.9%).

Conclusion

Over-ventilation is reduced significantly in LDB-CPR compared to manual CPR during the first and second 5 minutes of resuscitation.

Chest Compression Synchronized Ventilation versus Intermitted Positive Pressure Ventilation during Cardiopulmonary Resuscitation in a Pig Model

Background

Guidelines recommend mechanical ventilation with Intermitted Positive Pressure Ventilation (IPPV) during resuscitation. The influence of the novel ventilator mode Chest Compression Synchronized Ventilation (CCSV) on gas exchange and arterial blood pressure compared with IPPV was investigated in a pig model.

Methods

In 12 pigs (general anaesthesia/intubation) ventricular fibrillation was induced and continuous chest compressions were started after 3min. Pigs were mechanically ventilated in a cross-over setting with 5 ventilation periods of 4min each: Ventilation modes were during the first and last period IPPV (100% O₂, tidalvolumes = 7ml/kgKG, respiratoryrate = 10/min), during the 2nd, 3rd and 4th period CCSV (100% O₂), a pressure-controlled and with each chest compression synchronized breathing pattern with three different presets in randomized order. Presets: CCSV_A: P_insp = 60mbar, inspiratorytime = 205ms; CCSV_B: P_insp = 60mbar, inspiratorytime = 265ms; CCSV_C: P_insp = 45mbar, inspiratorytime = 265ms. Blood gas samples were drawn for each period, mean arterial (MAP) and centralvenous (CVP) blood pressures were continuously recorded. Results as median (25%/75%percentiles).

Results

Ventilation with each CCSV mode resulted in higher PaO₂ than IPPV: PaO₂: IPPV_first: 19.6(13.9/36.2)kPa, IPPV_last: 22.7(5.4/36.9)kPa (p = 0.77 vs IPPV_first), CCSV_A: 48.9(29.0/58.2)kPa (p = 0.028 vs IPPV_first, p = 0.0001 vs IPPV_last), CCSV_B: 54.0 (43.8/64.1) (p = 0.001 vs IPPV_first, p = 0.0001 vs IPPV_last), CCSV_C: 46.0 (20.2/58.4) (p = 0.006 vs IPPV_first, p = 0.0001 vs IPPV_last). Both the MAP and the difference MAP-CVP did not decrease during twelve minutes CPR with all three presets of CCSV and were higher than the pressures of the last IPPV period.

Conclusions

All patterns of CCSV lead to a higher PaO₂ and avoid an arterial blood pressure drop during resuscitation compared to IPPV in this pig model of cardiac arrest.

Mechanical ventilation during cardiopulmonary resuscitation with intermittent positive-pressure ventilation, bilevel ventilation, or chest compression synchronized ventilation in a pig model

OBJECTIVE

Mechanical ventilation with an automated ventilator is recommended during cardiopulmonary resuscitation with a secured airway. We investigated the influence of intermittent positive-pressure ventilation, bilevel ventilation, and the novel ventilator mode chest compression synchronized ventilation, a pressure-controlled ventilation triggered by each chest compression, on gas exchange, hemodynamics, and return of spontaneous circulation in a pig model.

DESIGN

Animal study.

SETTING

University laboratory.

SUBJECTS

Twenty-four three-month-old female domestic pigs.

INTERVENTIONS

The study was performed on pigs under general anesthesia with endotracheal intubation. Arterial and central venous catheters were inserted and IV rocuronium (1 mg/kg) was injected. After 3 minutes of cardiac arrest (ventricular fibrillation at t = 0 min), animals were randomized into intermittent positive-pressure ventilation (control group), bilevel, or chest compression synchronized ventilation group. Following 10 minute uninterrupted chest compressions and mechanical ventilation, advanced life support was performed (100% O2, up to six defibrillations, vasopressors).

MEASUREMENTS AND MAIN RESULTS

Blood gas samples were drawn at 0, 4 and 13 minutes. At 13 minutes, hemodynamics was analyzed beat-to-beat in the end-inspiratory and end-expiratory cycle comparing the IPPV with the bilevel group and the CCSV group. Data were analyzed with the Mann-Whitney U test. Return of spontaneous circulation was achieved in five of eight (intermittent positive-pressure ventilation), six of eight (bilevel), and four of seven (chest compression synchronized ventilation) pigs. The results of arterial blood gas analyses at t = 4 minutes and t = 13 minutes (torr) were as follows: PaO2 intermittent positive-pressure ventilation, 143 (76/256) and 262 (81/340); bilevel, 261 (109/386) (p = 0.195 vs intermittent positive-pressure ventilation) and 236 (86/364) (p = 0.878 vs intermittent positive-pressure ventilation); and chest compression synchronized ventilation, 598 (471/650) (p < 0.001 vs intermittent positive-pressure ventilation) and 634 (115/693) (p = 0.054 vs intermittent positive-pressure ventilation); PaCO2 intermittent positive-pressure ventilation, 40 (38/43) and 45 (36/52); bilevel, 39 (35/41) (p = 0.574 vs intermittent positive-pressure ventilation) and 46 (42/49) (p = 0.798); and chest compression synchronized ventilation, 28 (27/32) (p = 0.001 vs intermittent positive-pressure ventilation) and 26 (18/29) (p = 0.004); mixed venous pH intermittent positive-pressure ventilation, 7.34 (7.31/7.35) and 7.26 (7.25/7.31); bilevel, 7.35 (7.29/7.37) (p = 0.645 vs intermittent positive-pressure ventilation) and 7.27 (7.17/7.31) (p = 0.645 vs intermittent positive-pressure ventilation); and chest compression synchronized ventilation, 7.34 (7.33/7.39) (p = 0.189 vs intermittent positive-pressure ventilation) and 7.35 (7.34/7.36) (p = 0.006 vs intermittent positive-pressure ventilation). Mean end-inspiratory and end-expiratory arterial pressures at t = 13 minutes (mm Hg) were as follows: intermittent positive-pressure ventilation, 28.0 (25.0/29.6) and 27.9 (24.4/30.0); bilevel, 29.1 (25.6/37.1) (p = 0.574 vs intermittent positive-pressure ventilation) and 28.7 (24.2/36.5) (p = 0.721 vs intermittent positive-pressure ventilation); and chest compression synchronized ventilation, 32.7 (30.4/33.4) (p = 0.021 vs intermittent positive-pressure ventilation) and 27.0 (24.5/27.7) (p = 0.779 vs intermittent positive-pressure ventilation).

CONCLUSIONS

Both intermittent positive-pressure ventilation and bilevel provided similar oxygenation and ventilation during cardiopulmonary resuscitation. Chest compression synchronized ventilation elicited the highest mean arterial pressure, best oxygenation, and a normal mixed venous pH during cardiopulmonary resuscitation.

Comparison of manually triggered ventilation and bag-valve-mask ventilation during cardiopulmonary resuscitation in a manikin model

BACKGROUND

To compare a novel, pressure-limited, flow adaptive ventilator that enables manual triggering of ventilations (MEDUMAT Easy CPR, Weinmann, Germany) with a bag-valve-mask (BVM) device during simulated cardiac arrest.

METHODS

Overall 74 third-year medical students received brief video instructions (BVM: 57s, ventilator: 126s), standardised theoretical instructions and practical training for both devices. Four days later, the students were randomised into 37 two-rescuer teams and were asked to perform 8min of cardiopulmonary resuscitation (CPR) on a manikin using either the ventilator or the BVM (randomisation list). Applied tidal volumes (V(T)), inspiratory times and hands-off times were recorded. Maximum airway pressures (P(max)) were measured with a sensor connected to the artificial lung. Questionnaires concerning levels of fatigue, stress and handling were evaluated. V(T), pressures and hands-off times were compared using t-tests, questionnaire data were analysed using the Wilcoxon test.

RESULTS

BVM vs. ventilator (mean±SD): the mean V(T) (408±164ml vs. 315±165ml, p=0.10) and the maximum V(T) did not differ, but the number of recorded V(T)<200ml differed (8.1±11.3 vs. 17.0±14.4 ventilations, p=0.04). P(max) did not differ, but inspiratory times (0.80±0.23s vs. 1.39±0.31s, p<0.001) and total hands-off times (133.5±17.8s vs. 162.0±11.1s, p<0.001) did. The estimated levels of fatigue and stress were comparable; however, the BVM was rated to be easier to use (p=0.03).

CONCLUSION

For the user group investigated here, this ventilator exhibits no advantages in the setting of simulated CPR and carries a risk of prolonged no-flow time.

Pre-hospital airway management: guidelines from a task force from the Scandinavian Society for Anaesthesiology and Intensive Care Medicine

This article is intended as a generic guide to evidence-based airway management for all categories of pre-hospital personnel. It is based on a review of relevant literature but the majority of the studies have not been performed under realistic, pre-hospital conditions and the recommendations are therefore based on a low level of evidence (D). The advice given depends on the qualifications of the personnel available in a given emergency medical service (EMS). Anaesthetic training and routine in anaesthesia and neuromuscular blockade is necessary for the use of most techniques in the treatment of patients with airway reflexes. For anaesthesiologists, the Task Force commissioned by the Scandinavian Society of Anaesthesia and Intensive Care Medicine recommends endotracheal intubation (ETI) following rapid sequence induction when securing the pre-hospital airway, although repeated unsuccessful intubation attempts should be avoided independent of formal qualifications. Other physicians, as well as paramedics and other EMS personnel, are recommended the lateral trauma recovery position as a basic intervention combined with assisted mask-ventilation in trauma patients. When performing advanced cardiopulmonary resuscitation, we recommend that non-anaesthesiologists primarily use a supraglottic airway device. A supraglottic device such as the laryngeal tube or the intubation laryngeal mask should also be available as a backup device for anaesthesiologists in failed ETI.

Arterial blood gases during basic life support of human cardiac arrest victims

BACKGROUND

Ventilation with tidal volumes sufficient to raise the victim's chest is an integral part of guidelines for lay-rescuer basic life support, but optimal tidal volume, frequency and ratio to chest compressions are not known.

METHODS

Adults with non-traumatic, out-of-hospital cardiac arrest, who were not successfully resuscitated following advanced life support by the staff of a physician-manned ambulance, were included. Advanced life support comprised tracheal intubation and mechanical ventilation with tidal volume of 700 ml and 100% oxygen, 12 times per min. An arterial blood sample was drawn at the end of the resuscitation attempt and analysed on the scene. After the victim was declared dead, basic life support was initiated with chest compressions and mouth-to-mask or mouth-to-tracheal tube ventilation (15:2), with volumes sufficient to make the chest rise. The tracheal tube was equipped with an impedance valve to avoid passive ventilation secondary to chest compressions. Arterial blood samples were drawn after 7-8 min of basic life support and analysed on the scene.

RESULTS

Six men and two women, median (range) age 72 (32-86) years, were included in the study. Four of these received mouth-to-mask ventilation and four mouth-to-tracheal tube ventilation. Mean (S.D.) arterial blood carbon dioxide and oxygen tension during advanced life support were 6.4 (1.4)kPa and 22 (15)kPa, respectively. Similar values during basic life support were 9.6 (1.9)kPa and 8.5 (1.6)kPa, respectively, with no differences between the ventilation methods.

CONCLUSION

Ventilation during basic life support performed according to international guidelines (2000) resulted in arterial hypercapnia and hypoxia.

Acute management of sudden cardiac death in adults based upon the new CPR guidelines

PURPOSE OF THE REVIEW

The aim of this article is to provide a comprehensive description of interventions that can improve outcomes in adults with sudden cardiac death. The new American Heart Association 2005 Guidelines introduced a number of changes for the initial management of cardiorespiratory arrest based on new data that accumulated over the last 5 years.

ACUTE MANAGEMENT OF SUDDEN CARDIAC DEATH

Appropriate interventions targeting the three phases of cardiopulmonary resuscitation (CPR) (electrical, circulatory, and metabolic) should be implemented. Early defibrillation in early witnessed arrest with one shock is very effective and can improve survival outcomes. When resuscitation efforts are delayed and CPR is performed by paramedics, 2 min of CPR before shock is recommended. Emphasis has been placed on fast and forceful continuous compressions with minimal interruptions, adequate decompression, and decrease in the rate of ventilations to 8-10/min for intubated patients with two rescuers and a universal increase in compression to ventilation ratio to 30:2 for lone rescuers. Mechanical adjuncts to improve circulation have been adapted in the recommendations. The inspiratory impedance threshold device that enhances negative intrathoracic pressure and improves venous preload has been recommended for application in intubated and bag-mask ventilated patients. Owing to the difficulty of endotracheal intubation, airway management devices (Combitube and Laryngeal Mask Airway) can be used as alternatives with minimal extra training.

CONCLUSION

The new guidelines for CPR have focused on early defibrillation, uninterrupted compressions, complete decompression, fewer ventilations, and simplification and uniformity of the process.

Insight into the New Changes in European Resuscitation Council Guidelines for Adult Resuscitation (2005)

It is five years now since the last European resuscitation guidelines were published(1). The science of resuscitation has been enriched with further significant scientific evidence that has led to new evidence-based guidelines. These guidelines were released in November 2005 and published in the international Journal of Resuscitation, November 2005(2).

Over-the-head cardiopulmonary resuscitation improves efficacy in basic life support performed by professional medical personnel with a single rescuer: a simulation study

Two-rescuer cardiopulmonary resuscitation (CPR) is considered the best method for professional basic life support (BLS). However, in many prehospital cardiac arrest situations, one rescuer has to begin CPR alone while the other performs additional tasks. In theory, over-the-head CPR is a suitable alternative in this situation, with the added benefit of allowing the single rescuer to use a self-inflating bag for ventilation. In this trial, we compared standard single-rescuer CPR with over-the-head CPR in manikins. We planned this study using a crossover study design where each participant administered both CPR techniques in a randomized order. Ventilation and chest compression data were collected with analysis software during a 2-min CPR test for each technique. Sixty-seven emergency medical technician students participated in this trial. Over-the-head CPR allowed for superior ventilation compared to standard CPR (number of correct ventilations: 330 of 760 versus 279 of 779; P = 0.002). The quality of delivered chest compressions did not differ between the two groups (correct chest compressions: 4293 of 6304 versus 4313 of 6395; P = 0.44). In conclusion, our study has shown that over-the-head CPR may be an effective alternative BLS technique when a single professional rescuer has to perform CPR, likely offering superior ventilation and comparable chest compression quality compared with standard BLS.