Comparison of different inspiratory triggering settings in automated ventilators during cardiopulmonary resuscitation in a porcine model

Ventilation during cardiopulmonary resuscitation: A narrative review

Ventilation during cardiopulmonary resuscitation is vital to achieve optimal oxygenation but continues to be a subject of ongoing debate. This narrative review aims to provide an overview of various components and challenges of ventilation during cardiopulmonary resuscitation, highlighting key areas of uncertainty in the current understanding of ventilation management. It addresses the pulmonary pathophysiology during cardiac arrest, the importance of adequate alveolar ventilation, recommendations concerning the maintenance of airway patency, tidal volumes and ventilation rates in both synchronous and asynchronous ventilation. Additionally, it discusses ventilation adjuncts such as the impedance threshold device, the role of positive end-expiratory pressure ventilation, and passive oxygenation. Finally, this review offers directions for future research.

2024 RECOVER Guidelines: Basic Life Support. Evidence and knowledge gap analysis with treatment recommendations for small animal CPR

OBJECTIVE

To systematically review evidence and devise treatment recommendations for basic life support (BLS) in dogs and cats and to identify critical knowledge gaps.

DESIGN

Standardized, systematic evaluation of literature pertinent to BLS following Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. Prioritized questions were each reviewed by 2 Evidence Evaluators, and findings were reconciled by BLS Domain Chairs and Reassessment Campaign on Veterinary Resuscitation (RECOVER) Co-Chairs to arrive at treatment recommendations commensurate to quality of evidence, risk to benefit relationship, and clinical feasibility. This process was implemented using an Evidence Profile Worksheet for each question that included an introduction, consensus on science, treatment recommendations, justification for these recommendations, and important knowledge gaps. A draft of these worksheets was distributed to veterinary professionals for comment for 4 weeks prior to finalization.

SETTING

Transdisciplinary, international collaboration in university, specialty, and emergency practice.

RESULTS

Twenty questions regarding animal position, chest compression point and technique, ventilation strategies, as well as the duration of CPR cycles and chest compression pauses were examined, and 32 treatment recommendations were formulated. Out of these, 25 addressed chest compressions and 7 informed ventilation during CPR. The recommendations were founded predominantly on very low quality of evidence and expert opinion. These new treatment recommendations continue to emphasize the critical importance of high-quality, uninterrupted chest compressions, with a modification suggested for the chest compression technique in wide-chested dogs. When intubation is not possible, bag-mask ventilation using a tight-fitting facemask with oxygen supplementation is recommended rather than mouth-to-nose ventilation.

CONCLUSIONS

These updated RECOVER BLS treatment recommendations emphasize continuous chest compressions, conformation-specific chest compression techniques, and ventilation for all animals. Very low quality of evidence due to absence of clinical data in dogs and cats consistently compromised the certainty of recommendations, emphasizing the need for more veterinary research in this area.

[Paediatric Life Support]

The European Resuscitation Council (ERC) Paediatric Life Support (PLS) guidelines are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations of the International Liaison Committee on Resuscitation (ILCOR). This section provides guidelines on the management of critically ill or injured infants, children and adolescents before, during and after respiratory/cardiac arrest.

European Resuscitation Council Guidelines 2021: Paediatric Life Support

These European Resuscitation Council Paediatric Life Support (PLS) guidelines, are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the management of critically ill infants and children, before, during and after cardiac arrest.

Mechanical Ventilation Management During Mechanical Chest Compressions

Ventilation during chest compressions can lead to an increase in peak inspiratory pressure. High inspiratory pressure can raise the risk of injury to the respiratory system and make it challenging to deliver the required tidal volume. The utilization of mechanical devices for chest compression has exacerbated this challenge. The aim of this narrative review was to summarize the different mechanical ventilation strategies applied during mechanical cardiopulmonary resuscitation (CPR). To this end, we searched the PubMed and BioMed Central databases from inception to January 2020, using the search terms "mechanical ventilation," "cardiac arrest," "cardiopulmonary resuscitation," "mechanical cardiopulmonary resuscitation," and their related terms. We included all studies (human clinical or animal-based research studies, as well as studies using simulation models) to explore the various ventilation settings during mechanical CPR. We identified 842 relevant articles on PubMed and 397 on BioMed Central; a total of 38 papers were judged to be specifically related to the subject of this review. Of this sample, 17 studies were conducted on animal models, 6 considered a simulated scenario, 13 were clinical studies (5 of which were retrospective), and 2 studies constituted literature review articles. The main finding arising from the assessment of these publications is that a high [Formula: see text] must be guaranteed during CPR. Low-grade evidence suggests turning off inspiratory triggering and applying PEEP ≥ 5 cm H₂O. The analysis also revealed that many uncertainties persist regarding the ideal choice of ventilation mode, tidal volume, the ventilation rate setting, and the inspiratory:expiratory ratio. None of the current international guidelines indicate the "best" mechanical ventilation strategy to apply during mechanical CPR. We propose an operating algorithm worthy of future discussion and study. Future studies specifically addressing the topics covered in this review are required.

"Six-dial Strategy"-Mechanical Ventilation during Cardiopulmonary Resuscitation

As per current guidelines, whenever an advanced airway is in place during cardiopulmonary resuscitation, positive pressure ventilation should be provided without pausing for chest compression. Positive pressure ventilation can be provided through bag-valve resuscitator (BV) or mechanical ventilator (MV), which was found to be equally efficacious. In a busy emergency department, with less trained personnel use of MV is advantageous over BV in terms of reducing human errors and relieving the airway manager to focus on other resuscitation tasks. Currently, there are no guidelines specific to MV settings in cardiac arrest. We present a concept of "six-dial ventilator strategy during CPR" that encompasses the evidence-based settings appropriate during chest compression. We suggest use of volume control ventilation with the following settings: (1) positive end-expiratory pressure of 0 cm of water (to allow venous return), (2) tidal volume of 8 mL/kg with fraction of inspired oxygen at 100% (for adequate oxygenation), (3) respiratory rate of 10 per minute (for adequate ventilation), (4) maximum peak inspiratory pressure or P _max alarm of 60 cm of water (to allow tidal volume delivery during chest compression), (5) switching OFF trigger (to avoid trigger by chest recoil), and (6) inspiratory to expiratory time ratio of 1:5 (to provide adequate inspiratory time of 1 second). How to cite this article: Sahu AK, Timilsina G, Mathew R, Jamshed N, Aggarwal P. "Six-dial Strategy"-Mechanical Ventilation during Cardiopulmonary Resuscitation. Indian J Crit Care Med 2020;24(6):487-489.

Continuous chest compressions with a simultaneous triggered ventilator in the Munich Emergency Medical Services: a case series

Background: Mechanical chest compression devices are commonly used providing a constant force and frequency of chest compression during cardiopulmonary resuscitation. However, there are currently no recommendations on ventilation during cardiopulmonary resuscitation with a mechanical chest compression device using continuous mode. An effective method for ventilation in such scenarios might be a triggered oxygen-powered resuscitator. Methods: We report seven cardiopulmonary resuscitation cases from the Munich Emergency Medical Service where mechanical chest compression devices in continuous mode were used with an oxygen-powered resuscitator. In each case, the resuscitator (Oxylator®) was running in automatic mode delivering a breath during the decompression phase of the chest compressions at a frequency of 100 per minute. End-tidal carbon dioxide and pulse oximetry were measured. Additional data was collected from the resuscitation protocol of each patient. Results: End-tidal carbon dioxide was available in all cases while oxygen saturation only in four. Five patients had a return of spontaneous circulation. Based on the end-tidal carbon dioxide values of each of the cases, the resuscitator did not seem to cause hyperventilation and suggests that good-quality cardiopulmonary resuscitation was delivered. Conclusions: Continuous chest compressions using a mechanical chest compression device and simultaneous synchronized ventilation using an oxygen-powered resuscitator in an automatic triggering mode might be feasible during cardiopulmonary resuscitation.

Duration of cardiac arrest requires different ventilation volumes during cardiopulmonary resuscitation in a pig model

There are few studies examining the ventilation strategies recommended by current CPR guidelines. We investigated the influence of different minute volume applying to untreated cardiac arrest with different duration, on resuscitation effects in a pig model. 32 Landrace pigs with 4 or 8 min (16 pigs each) ventricular fibrillation (VF) randomly received two ventilation strategies during CPR. "Guideline" groups received mechanical ventilation with a tidal volume of 7 ml/kg and a frequency of 10/min, while "Baseline" groups received a tidal volume (10 ml/kg) and a frequency used at baseline to maintain an end-tidal PCO₂ (P_ETCO₂) between 35 and 40 mmHg before VF. Mean airway pressures and intrathoracic pressures (P_IT) in the Baseline-4 min group were significantly higher than those in the Guideline-4 min group (all P < 0.05). Similar results were observed in the 8 min pigs, except for no significant difference in minimal P_IT and P_ETCO₂ during 10 min of CPR. Venous pH and venous oxygen saturation were significantly higher in the Baseline-8 min group compared to the Guideline-8 min group (all P < 0.05). Aortic pressure in the Baseline-8 min group was higher than in the Guideline-8 min group. Seven pigs in each subgroup of 4 min VF models achieved the return of spontaneous circulation (ROSC). Higher ROSC was observed in the Baseline-8 min group than in the Guideline-8 min group (87.5% vs. 37.5%, P = 0.039). For 4 min VF but not 8 min VF, a guideline-recommended ventilation strategy had satisfactory results during CPR. A higher minute ventilation resulted in better outcomes for subjects with 8 min of untreated VF through thoracic pump.

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

AIM

Guidelines recommend detecting return of spontaneous circulation (ROSC) by a rising concentration of carbon dioxide in the exhalation air. As CO₂ is influenced by numerous factors, no absolute cut-off values of CO₂ to detect ROSC are agreed on so far. As trends in CO₂ might be less affected by influencing factors, we investigated an approach which is based on detecting CO₂-trends in real-time.

METHODS

We conducted a retrospective case-control study on 169 CO₂ time series from out of hospital cardiac arrests resuscitated by Muenster City Ambulance-Service, Germany. A recently developed statistical method for real-time trend-detection (SCARM) was applied to each time series. For each series, the percentage of time points with detected positive and negative trends was determined.

RESULTS

ROSC time series had larger percentages of positive trends than No-ROSC time series (p=0.003). The median percentage of positive trends was 15% in the ROSC time series (IQR: 5% to 23%) and 7% in the No-ROSC time series (IQR: 3% to 14%). A receiver operating characteristic (ROC) analysis yielded an optimal threshold of 13% to differentiate between ROSC and No-ROSC cases with a specificity of 58.4% and sensitivity of 73.9%; the area under the curve was 63.5%.

CONCLUSION

Patients with ROSC differed from patients without ROSC as to the percentage of detected CO₂ trends, indicating the potential of our real-time trend-detection approach. Since the study was designed as a proof of principle and its calculated specificity and sensitivity are low, more research is required to implement CO₂-trend-detection into clinical use.