Bystander mouth-to-mouth ventilation and regurgitation during cardiopulmonary resuscitation

Acute lung injury and post-cardiac arrest syndrome: a narrative review

BACKGROUND

Post-cardiac arrest syndrome (PCAS) presents a multifaceted challenge in clinical practice, characterized by severe neurological injury and high mortality rates despite advancements in management strategies. One of the important critical aspects of PCAS is post-arrest lung injury (PALI), which significantly contributes to poor outcomes. PALI arises from a complex interplay of pathophysiological mechanisms, including trauma from chest compressions, pulmonary ischemia-reperfusion (IR) injury, aspiration, and systemic inflammation. Despite its clinical significance, the pathophysiology of PALI remains incompletely understood, necessitating further investigation to optimize therapeutic approaches.

METHODS

This review comprehensively examines the existing literature to elucidate the epidemiology, pathophysiology, and therapeutic strategies for PALI. A comprehensive literature search was conducted to identify preclinical and clinical studies investigating PALI. Data from these studies were synthesized to provide a comprehensive overview of PALI and its management.

RESULTS

Epidemiological studies have highlighted the substantial prevalence of PALI in post-cardiac arrest patients, with up to 50% of survivors experiencing acute lung injury. Diagnostic imaging modalities, including chest X-rays, computed tomography, and lung ultrasound, play a crucial role in identifying PALI and assessing its severity. Pathophysiologically, PALI encompasses a spectrum of factors, including chest compression-related trauma, pulmonary IR injury, aspiration, and systemic inflammation, which collectively contribute to lung dysfunction and poor outcomes. Therapeutically, lung-protective ventilation strategies, such as low tidal volume ventilation and optimization of positive end-expiratory pressure, have emerged as cornerstone approaches in the management of PALI. Additionally, therapeutic hypothermia and emerging therapies targeting mitochondrial dysfunction hold promise in mitigating PALI-related morbidity and mortality.

CONCLUSION

PALI represents a significant clinical challenge in post-cardiac arrest care, necessitating prompt diagnosis and targeted interventions to improve outcomes. Mitochondrial-related therapies are among the novel therapeutic strategies for PALI. Further clinical research is warranted to optimize PALI management and enhance post-cardiac arrest care paradigms.

Enhancing Bystander Intervention: Insights from the Utstein Analysis of Out-of-Hospital Cardiac Arrests in Slovenia

Background and Objectives: Out-of-hospital cardiac arrest (OHCA) and survival is a pressing matter all around the world. Despite years of research and great strides and advancements, survival remains alarmingly low. The aim of this study was to measure the survival and characteristics of patients having an OHCA in Slovenia, with an in-depth look at how the bystanders affect the return of spontaneous circulation (ROSC) and survival of OHCA. Materials and Methods: In this observational cross-sectional prospective study, we enrolled patients between 1 September 2022 and 30 November 2022, with a follow-up period of 1 month. All OHCAs attended by the emergency medical services were included. Data were collected and analyzed according to the Utstein 2015 reporting template. Independent predictors of ROSC and 30-day survival or survival were explored using ridge regression. Results: ROSC was achieved in 41% of cases where resuscitation was attempted. The overall 30-day survival rate where resuscitation was attempted was 14%. In 13% of all cases where resuscitation was attempted, patients had a favorable neurological outcome. Using our prediction model, we found that defibrillation under 20 min and ventricular fibrillation as an initial rhythm improves survival, whilst no defibrillation and bystander full cardiopulmonary resuscitation negatively predicted survival. Conclusions: Slovenia has OHCA 30-day survival comparable to the rest of the European Union. The favorable neurological outcome is high. Our data show that bystanders do not significantly improve survival. This represents an untapped potential of general public education in cardiopulmonary resuscitation and automatic external defibrillator use. Following good practices from abroad and improving layperson CPR knowledge could further improve OHCA survival.

Standard cardiopulmonary resuscitation versus chest compressions only after out-of-hospital cardiac arrest: a protocol for a systematic review and meta-analysis

INTRODUCTION

The 2020 American Heart Association guidelines encourage lay rescuers to provide chest compression-only cardiopulmonary resuscitation to simplify the process and encourage cardiopulmonary resuscitation initiation. However, recent clinical trials had contradictory results about chest compression-only cardiopulmonary resuscitation. This study will aim to compare standard and chest compressions-only cardiopulmonary resuscitation after out-of-hospital cardiac arrest.

METHODS AND ANALYSIS

This study will retrieve only randomised and quasi-randomised controlled trials from the Cochrane Library, PubMed, Web of Science and Embase databases. Data on study design, participant characteristics, intervention details and outcomes will be extracted by a unified standard form. Primary outcomes to be assessed are hospital admission, discharge, and 30-day survival, and return of spontaneous circulation. The Grading of Recommendations, Assessment, Development and Evaluation framework will evaluate the quality of evidence. Cochrane's tool for assessing the risk of bias will evaluate risk deviation. If the I2 statistic is lower than 40%, the fixed-effects model will be used for meta-analysis. Otherwise, the random-effects model will be used. The search will be performed following the publication of this protocol (estimated to occur on 30 December 2024).

DISCUSSION

This study will evaluate the effect of chest compression-only cardiopulmonary resuscitation after out-of-hospital cardiac arrest and provide evidence for cardiopulmonary resuscitation guidelines.

ETHICS AND DISSEMINATION

No patient or public entity will be involved in this study. Therefore, the study does not need to be ethically reviewed. The results of the study will be disseminated through peer-reviewed journal publications and committee conferences.

PROSPERO REGISTRATION NUMBER

CRD42021295507.

Effect of stomach inflation during cardiopulmonary resuscitation on return of spontaneous circulation in out-of-hospital cardiac arrest patients: A retrospective observational study

BACKGROUND

Gastric inflation caused by excessive ventilation is a common complication of cardiopulmonary resuscitation. Gastric inflation may further compromise ventilation via increases in intrathoracic pressure, leading to decreased venous return and cardiac output, which may impair out-of-hospital cardiac arrest (OHCA) outcomes. The purpose of this study was to measure the gastric volume of OHCA patients using computed tomography (CT) scan images and evaluate the effect of gastric inflation on return of spontaneous circulation (ROSC).

METHODS

In this single-center, retrospective, observational study, CT scan was conducted after ROSC or immediately after death. Total gastric volume was measured. Primary outcome was ROSC. Achievement of ROSC was compared in the gastric distention group and the no gastric distention group; gastric distension was defined as total gastric volume in the ≥75th percentile. Additionally, factors associated with gastric distention were examined.

RESULTS

A total of 446 cases were enrolled in the study; 120 cases (27%) achieved ROSC. The median gastric volume was 400 ml for all OHCA subjects; 1068 ml in gastric distention group vs. 287 ml in no gastric distention group. There was no difference in ROSC between the groups (27/112 [24.1%] vs. 93/334 [27.8%], p = 0.440). Gastric distention did not have a significant impact, even after adjustments (adjusted odds ratio 0.73, 95% confidence interval [0.42-1.29]). Increased gastric volume was associated with longer emergency medical service activity time.

CONCLUSIONS

We observed a median gastric volume of 400 ml in patients after OHCA resuscitation. In our setting, gastric distention did not prevent ROSC.

Compromised cardiopulmonary resuscitation quality due to regurgitation during endotracheal intubation: a randomised crossover manikin simulation study

Background

Regurgitation is a complication common during cardiopulmonary resuscitation (CPR). This manikin study evaluated the effect of regurgitation during endotracheal intubation on CPR quality.

Methods

An airway-CPR manikin was modified to regurgitate simulated gastric contents into the oropharynx during chest compression during CPR. In total, 54 emergency medical technician-paramedics were assigned to either an oropharyngeal regurgitation or clean airway scenario and then switched to the other scenario after finishing the first. The primary outcomes were CPR quality metrics, including chest compression fraction (CCF), chest compression depth, chest compression rate, and longest interruption time. The secondary outcomes were intubation success rate and intubation time.

Results

During the first CPR–intubation sequence, the oropharyngeal regurgitation scenario was associated with a significantly lower CCF (79.6% vs. 85.1%, P < 0.001), compression depth (5.2 vs. 5.4 cm, P < 0.001), and first-pass success rate (35.2% vs. 79.6%, P < 0.001) and greater longest interruption duration (4.0 vs. 3.0 s, P < 0.001) than the clean airway scenario. During the second and third sequences, no significant difference was observed in the CPR quality metrics between the two scenarios. In the oropharyngeal regurgitation scenario, successful intubation was independently and significantly associated with compression depth (hazard ratio = 0.47, 95% confidence interval, 0.24–0.91), whereas none of the CPR quality metrics were related to successful intubation in the clean airway scenario.

Conclusion

Regurgitation during endotracheal intubation significantly reduces CPR quality.

Trial registration

ClinicalTrials.gov, NCT05278923, March 14, 2022.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12873-022-00662-0.

Cardiac arrest after pulmonary aspiration in hospitalised patients: a national observational study

OBJECTIVE

To study characteristics and outcomes among patients with in-hospital cardiac arrest (IHCA) due to pulmonary aspiration.

DESIGN

A retrospective observational study based on data from the Swedish Registry of Cardiopulmonary Resuscitation (SRCR).

SETTING

The SRCR is a nationwide quality registry that covers 96% of all Swedish hospitals. Participating hospitals vary in size from secondary hospitals to university hospitals.

PARTICIPANTS

The study included patients registered in the SRCR in the period 2008 to 2017. We compared patients with IHCA caused by pulmonary aspiration (n=127), to those with IHCA caused by respiratory failure of other causes (n=2197).

PRIMARY AND SECONDARY OUTCOME MEASURES

Primary outcome was 30-day survival. Secondary outcome was sustained return of spontaneous circulation (ROSC) defined as ROSC at the scene and admitted alive to the intensive care unit.

RESULTS

In the aspiration group 80% of IHCA occurred on general wards, as compared with 63.6% in the respiratory failure group (p<0.001). Patients in the aspiration group were less likely to be monitored at the time of the arrest (18.5% vs 38%, p<0.001) and had a significantly lower rate of sustained ROSC (36.5% vs 51.6%, p=0.001). The unadjusted 30-day survival rate compared with the respiratory failure group was 7.9% versus 18.0%, p=0.024. In a propensity score analysis (including variables; year, age, gender, location of arrest, initial heart rhythm, ECG monitoring, witnessed collapse and a previous medical history of; cancer, myocardial infarction or heart failure) the OR for 30-day survival was 0.46 (95% CI 0.19 to 0.94).

CONCLUSIONS

In-hospital cardiac arrest preceded by pulmonary aspiration occurred more often on general wards among unmonitored patients. These patients had a lower 30-day survival rate compared with IHCA caused by respiratory failure of other causes.

Efficacy of Manual Ventilation Techniques During Cardiopulmonary Resuscitation in Dogs

The efficacy of ventilation of dogs during cardiopulmonary resuscitation (CPR) with a tight fitting face mask or mouth-to-nose rescue breathing has not been evaluated. Twenty-four purpose bred research dogs: Dogs were randomized to be ventilated by cuffed orotracheal tube, tight fitting face mask, mouth-to-nose breathing or compressions only during CPR (n = 6 in all groups). Orotracheal tube and face mask ventilation was performed on room air. Chest compressions were performed during the experimental procedure. Arterial blood gases were performed prior to euthanasia (baseline), at 3 min and at 6 min of CPR. PaO₂ and PaCO₂ were compared for each time point and each group. There was no difference in PaO₂ or PaCO₂ between groups at baseline. At 6 min all groups had a significantly higher PaCO₂ (P ≤ 0.005) and the facemask and compression only groups had a significantly lower PaO₂ (P < 0.02) when compared to the orotracheal tube group. There was no difference between the PaO₂ of the mouth-to-nose group compared to the orotracheal tube group at 3 or 6 min. Gastric distension, regurgitation, gas leakage around the mouth, and ineffective breaths were all noted in both the face mask and mouth-to-nose group. The results of this study supports that orotracheal intubation is the preferred technique for ventilation during CPR in dogs. When orotracheal intubation is not possible, face mask ventilation or mouth-to-nose ventilation would be reasonable alternatives. When oxygen supplementation is available, face mask ventilation is likely to be superior. Appropriate training for both face mask and mouth-to-nose ventilation techniques is recommended.

Chest compressions do not disrupt the seal created by the laryngeal mask airway during positive pressure ventilation: a preliminary porcine study

OBJECTIVE

Pulmonary aspiration of gastric contents occurs 20 to 30% of the time during cardiopulmonary resuscitation (CPR) of cardiac arrest due to loss of protective airway reflexes, pressure changes generated during CPR, and positive pressure ventilation (PPV). Although the American Heart Association has recommended the laryngeal mask airway (LMA) as an acceptable alternative airway for use by emergency medical service personnel, concerns over the capacity of the device to protect from pulmonary aspiration remain. We sought to determine the occurrence of aspiration after LMA placement, CPR, and PPV.

METHODS

We inserted a size 4 LMA, modified so that a vacuum catheter could be advanced past the LMA diaphragm, into the hypopharynx of 16 consecutive postexperimental mixed-breed domestic swine. Fifteen millilitres of heparinized blood was instilled into the oropharynx. Chest compressions were performed for 60 seconds with asynchronous ventilation via a mechanical ventilator. We then suctioned through the LMA for 1 minute. The catheter was removed and inspected for signs of blood. The LMA cuff was deflated, removed, and inspected for signs of blood.

RESULTS

None of 16 animals (95% CI 0-17%) had a positive test for the presence of blood in both the vacuum catheter and the intima of the LMA diaphragm.

CONCLUSIONS

In this swine model of regurgitation after LMA placement, there were no cases with evidence of blood beyond the seal created by the LMA cuff. Future studies are needed to determine the frequency of pulmonary aspiration after LMA placement during CPR and PPV in the clinical setting.

Intubating laryngeal mask airway placement by non-physician healthcare providers in management out-of-hospital cardiac arrests: a case series

AIM OF THE STUDY

The role of supralaryngeal devices in airway management in out-of-hospital cardiac arrests (OHCA) remains controversial. The aim of this prospective observational trial was to evaluate the feasibility and effectiveness of intubating laryngeal mask airway (ILMA) when used by trained prehospital emergency nurses in the setting of OHCA.

METHODS

After approval from the Research Ethics Board, prehospital emergency nurses trained in placement of ILMA (Fastrach™, LMA Vitaid, Toronto, Ontario, Canada) followed a formal protocol for airway control during OHCA. The primary outcome was the success rate of ILMA placement, while secondary outcomes were success rate of tracheal intubation through the ILMA, and the incidence of regurgitation of gastric contents.

RESULTS

During the study period, 302 ILMA placements were attempted by emergency nurses during OHCA resuscitation. After ILMA placement, but before attempt for intubation, ventilation was possible in 290 patients (96%). Obstruction or major leaks were observed in 12 patients (4%). Tracheal tube insertion through the ILMA was attempted in 265 patients, and was performed in 254 (95.8%). This allowed for proper lung ventilation through the tracheal tube in 242 cases whereas 12 tubes were esophageal or proved obstructed. Regurgitation of gastric contents occurred in 43 (14.2%) patients; in 23 cases before arrival of the first aid team, in 18 cases before ILMA placement, and in 2 cases after the ILMA placement.

CONCLUSION

The use of ILMA for airway management by trained emergency nurses during OHCA resuscitation is feasible and allows for effective airway management. The success rate of tracheal tube placement through the ILMA was high. In addition, the incidence of regurgitation was lower when using the ILMA than that previous historical reports with face-mask ventilation.

Pulseless electrical activity and successful out-of-hospital resuscitation - long-term survival and quality of life: an observational cohort study

Background

The aim of the study was to evaluate the long-term outcome of patients successfully resuscitated from pre-hospital cardiac arrest with initial pulseless electrical activity (PEA), because the long-term outcome of these patients is unknown. Survival, neurological status one year after cardiac arrest and self-perceived quality of life after five years were assessed.

Methods

This retrospective study included adult patients resuscitated from PEA between August 2001 and March 2003 in three urban areas in southern Finland. A validated questionnaire was sent to patients while neurological status according to the Cerebral Performance Category (CPC) -classification was assessed based on medical database notes recorded during follow-up evaluations.

Results

Out of 99 included patients in whom resuscitation was attempted, 41 (41%) were successfully resuscitated and admitted to hospital. Ten (10%) patients were discharged from hospital. Seven were alive after one year and six after five years following cardiac arrest. Five of the seven patients alive one year after resuscitation presented with the same functional level as prior to cardiac arrest.

Conclusions

Patients with initial PEA have been considered to have poor prognosis, but in our material, half of those who survived to hospital discharge were still alive after 5 years. Their self-assessed quality of life seems to be good with only mild to moderate impairments in activities of daily life.

Effectiveness of mouth-to-mouth ventilation after video self-instruction training in laypersons

BACKGROUND

Mouth-to-mouth ventilation is a skill taught in cardiopulmonary resuscitation (CPR) training for laypersons. However, its effectiveness is questioned. Our aim was to determine the effectiveness of mouth-to-mouth ventilation training using a self-instruction CPR training video for laypersons.

METHODS

Video-self-instruction CPR training was conducted with CPR Anytime (American Heart Association [AHA] & Laerdal Corporation) for laypersons who had not received CPR training during the recent 5 years. Immediately before, immediately after, and 8 weeks after the CPR training, an AHA basic life support instructor carried out a skill performance test using a standardized checklist. Also, 8 weeks after the training, a skill test concerning chest compression and mouth-to-mouth ventilation was conducted using a trained reporter.

RESULTS

Cardiopulmonary resuscitation training of 84 laypersons was conducted. The mean performance score (from 0 to 2) for mouth-to-mouth ventilation was 0.24 right before the training, 1.58 right after the training, and 0.95 eight weeks after the training. The mean performance scores for chest compression were 0.13, 1.79, and 1.40, right before, right after, and 8 weeks after the CPR training, respectively. The rates of successful mouth-to-mouth ventilation and compression were 11.9%, and 39.1%, respectively.

CONCLUSIONS

The effectiveness and short-term retention rate of mouth-to-mouth ventilation after video self-instruction CPR training in laypersons was significantly lower than for chest compressions.

Effects of stomach inflation on haemodynamic and pulmonary function during cardiopulmonary resuscitation in pigs

AIM

Stomach inflation during cardiopulmonary resuscitation (CPR) is frequent, but the effect on haemodynamic and pulmonary function is unclear. The purpose of this study was to evaluate the effect of clinically realistic stomach inflation on haemodynamic and pulmonary function during CPR in a porcine model.

METHODS

After baseline measurements ventricular fibrillation was induced in 21 pigs, and the stomach was inflated with 0L (n=7), 5L (n=7) or 10L air (n=7) before initiating CPR.

RESULTS

During CPR, 0, 5, and 10L stomach inflation resulted in higher mean pulmonary artery pressure [median (min-max)] [35 (28-40), 47 (25-50), and 51 (49-75) mmHg; P<0.05], but comparable coronary perfusion pressure [10 (2-20), 8 (4-35) and 5 (2-13) mmHg; P=0.54]. Increasing (0, 5, and 10L) stomach inflation decreased static pulmonary compliance [52 (38-98), 19 (8-32), and 12 (7-15) mL/cmH(2)O; P<0.05], and increased peak airway pressure [33 (27-36), 53 (45-104), and 103 (96-110) cmH(2)O; P<0.05). Arterial oxygen partial pressure was higher with 0L when compared with 5 and 10L stomach inflation [378 (88-440), 58 (47-113), and 54 (43-126) mmHg; P<0.05). Arterial carbon dioxide partial pressure was lower with 0L when compared with 5 and 10L stomach inflation [30 (24-36), 41(34-51), and 56 (45-68) mmHg; P<0.05]. Return of spontaneous circulation was comparable between groups (5/7 in 0L, 4/7 in 5L, and 3/7 in 10L stomach inflation; P=0.56).

CONCLUSIONS

Increasing levels of stomach inflation had adverse effects on haemodynamic and pulmonary function, indicating an acute abdominal compartment syndrome in this CPR model.

Improving cardiopulmonary resuscitation quality to ensure survival

PURPOSE OF REVIEW

There is correlation between quality of bystander cardiopulmonary resuscitation and patient survival. Recent developments in defibrillator technology enable recording of cardiopulmonary resuscitation quality, and have shown quality of professional cardiopulmonary resuscitation far from guidelines' levels for factors such as chest compression depth and rate, ventilation rate, and pauses in chest compressions. The effects of cardiopulmonary resuscitation quality factors on patient survival are presently under scrutiny.

RECENT FINDINGS

Factors such as depth of and pauses in chest compressions immediately before defibrillation attempts affect outcome. Both immediate automated feedback on cardiopulmonary resuscitation quality and use of the same quality data during postevent debriefing improve cardiopulmonary resuscitation quality, and the combination appears to improve outcome. The increased awareness of quality problems, particularly unwanted pauses in chest compressions, has caused more emphasis on chest compressions in cardiopulmonary resuscitation protocols including the 2005 Guidelines. There is a growing number of reports of increased survival with these new protocols.

SUMMARY

Cardiopulmonary resuscitation quality affects survival after cardiac arrest. Reporting cardiopulmonary resuscitation quality data should be standard in all studies of cardiac arrest as effects of studied interventions can depend on or influence cardiopulmonary resuscitation quality. These data are also valuable in quality improvement processes both in-hospital and out-of-hospital.

Detection of carbon dioxide in expired air after oesophageal intubation; the role of bystander mouth-to-mouth ventilation

BACKGROUND

The identification of a correctly placed tube during anaesthesia routinely depends on the detection of carbon dioxide (CO2) in the expired air.

RESULTS

We describe a previously unreported cause of false-positive prediction in two patients with high initial values of CO2 in expired air after oesophageal intubation. Both patients had received bystander cardiopulmonary resuscitation with mouth-to-mouth ventilation, and the CO2 from the rescuers' expired air was trapped and subsequently detected after oesophageal intubation.

Incidence of regurgitation and pulmonary aspiration of gastric contents in survivors from out-of-hospital cardiac arrest

BACKGROUND

The regurgitation of gastric contents and subsequent pulmonary aspiration remain serious adverse events in cardiac arrest and cardiopulmonary resuscitation. The aim of this study was to determine the association between clinical signs of regurgitation and radiological findings consistent with aspiration in resuscitated out-of-hospital cardiac arrest (OHCA) patients admitted to hospital.

METHODS

The incidence of regurgitation was studied in 182 successfully resuscitated OHCA patients. The inclusion criterion was the restoration of spontaneous circulation after OHCA not caused by trauma or drug overdose.

RESULTS

The incidence of regurgitation was 20%. Regurgitation was associated with radiological findings consistent with aspiration with a high specificity (81%) and a low sensitivity (46%).

CONCLUSIONS

Although there was a strong association between clinical regurgitation and radiological findings consistent with aspiration, our data suggest that regurgitation is not invariably followed by radiological findings compatible with aspiration. Radiological findings consistent with aspiration are relatively infrequent without preceding signs of regurgitation in resuscitated patients.