Effects of smaller tidal volumes during basic life support ventilation in patients with respiratory arrest: good ventilation, less risk?

Automatic Mechanical Ventilation vs Manual Bag Ventilation During CPR: A Pilot Randomized Controlled Trial

BACKGROUND

There is insufficient evidence supporting the theory that mechanical ventilation can replace the manual ventilation method during CPR.

RESEARCH QUESTION

Is using automatic mechanical ventilation (MV) feasible and comparable to the manual ventilation method during CPR?

STUDY DESIGN AND METHODS

This pilot randomized controlled trial compared MV and manual bag ventilation (BV) during CPR after out-of-hospital cardiac arrest (OHCA). Patients with medical OHCA arriving at the ED were randomly assigned to two groups: an MV group using a mechanical ventilator and a BV group using a bag valve mask. Primary outcome was any return of spontaneous circulation (ROSC). Secondary outcomes were changes of arterial blood gas analysis results during CPR. Tidal volume, minute volume, and peak airway pressure were also analyzed.

RESULTS

A total of 60 patients were enrolled, and 30 patients were randomly assigned to each group. There were no statistically significant differences in basic characteristics of OHCA patients between the two groups. The rate of any return of spontaneous circulation was 56.7% in the MV group and 43.3% in the BV group, indicating no significant (P = .439) difference between the two groups. There were also no statistically significant differences in changes of PH, Pco2, Po2, bicarbonate, or lactate levels during CPR between the two groups (P values = .798, 0.249, .515, .876, and .878, respectively). Significantly lower tidal volume (P < .001) and minute volume (P = .009) were observed in the MV group.

INTERPRETATION

In this pilot trial, the use of MV instead of BV during CPR was feasible and could serve as a viable alternative. A multicenter randomized controlled trial is needed to create sufficient evidence for ventilation guidelines during CPR.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov; No.: NCT05550454; URL: www.

CLINICALTRIALS

gov.

Out-of-Hospital Cardiac Arrest

Survival from out-of-hospital cardiac arrest (OHCA) is predicated on a community and system-wide approach that includes rapid recognition of cardiac arrest, capable bystander CPR, effective basic and advanced life support (BLS and ALS) by EMS providers, and coordinated postresuscitation care. Management of these critically ill patients continues to evolve. This article focuses on the management of OHCA by EMS providers.

Performances and limits of Bag-Valve-Device for pre-oxygenation and manual ventilation: A comparative bench and cadaver study

INTRODUCTION

Bag-Valve-Device (BVD) is the most frequently used device for pre-oxygenation and ventilation during cardiopulmonary resuscitation (CPR). A minimal expired fraction of oxygen (FeO2) above 0.85 is recommended during pre-oxygenation while insufflated volume (VTi) should be reduced during manual ventilation. The objective was to compare the performances of different BVD in simulated conditions.

METHODS

Nine BVD were evaluated during pre-oxygenation: spontaneous breathing patients were simulated on a test lung (mild and severe conditions). FeO2 was measured with and without positive end-expiratory pressure (PEEP). CO2 rebreathing was evaluated. Then, manual ventilation was performed by 36 caregivers (n = 36) from three hospitals on a specific manikin; same procedure was repeated by 3 caregivers (n = 3) on two human cadavers with three of the nine BVD: In non-CPR scenario and during mechanical CPR with Interrupted Chest Compressions strategy (30:2).

RESULTS

Pre-oxygenation: FeO2 was lower than 0.85 for three BVD in severe condition and for two BVD in mild condition. FeO2 was higher than 0.85 in eight of nine BVD with an additional PEEP valve (PEEP 5 cmH2O). One BVD induced CO2 rebreathing. Manual ventilation: For non-CPR manual ventilation, mean VTi was within the predefined lung protective range (4-8 mL/kg PBW) for all BVD on the bench. For CPR manual ventilation, mean VTi was above the range for three BVD on the bench. Similar results were observed on cadavers.

CONCLUSIONS

Several BVD did not reach the FeO2 required during pre-oxygenation. Manual ventilation was significantly less protective in three BVD. These observations are related to the different BVD working principles.

2023 American Heart Association Focused Update on the Management of Patients With Cardiac Arrest or Life-Threatening Toxicity Due to Poisoning: An Update to the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care

In this focused update, the American Heart Association provides updated guidance for resuscitation of patients with cardiac arrest, respiratory arrest, and refractory shock due to poisoning. Based on structured evidence reviews, guidelines are provided for the treatment of critical poisoning from benzodiazepines, β-adrenergic receptor antagonists (also known as β-blockers), L-type calcium channel antagonists (commonly called calcium channel blockers), cocaine, cyanide, digoxin and related cardiac glycosides, local anesthetics, methemoglobinemia, opioids, organophosphates and carbamates, sodium channel antagonists (also called sodium channel blockers), and sympathomimetics. Recommendations are also provided for the use of venoarterial extracorporeal membrane oxygenation. These guidelines discuss the role of atropine, benzodiazepines, calcium, digoxin-specific immune antibody fragments, electrical pacing, flumazenil, glucagon, hemodialysis, hydroxocobalamin, hyperbaric oxygen, insulin, intravenous lipid emulsion, lidocaine, methylene blue, naloxone, pralidoxime, sodium bicarbonate, sodium nitrite, sodium thiosulfate, vasodilators, and vasopressors for the management of specific critical poisonings.

Out-of-Hospital Cardiac Arrest

Survival from out-of-hospital cardiac arrest (OHCA) is predicated on a community and system-wide approach that includes rapid recognition of cardiac arrest, capable bystander CPR, effective basic and advanced life support (BLS and ALS) by EMS providers, and coordinated postresuscitation care. Management of these critically ill patients continues to evolve. This article focuses on the management of OHCA by EMS providers.

Cardiopulmonary Resuscitation: The Importance of the Basics

Cardiac arrest is the loss of organized cardiac activity. Unfortunately, survival to hospital discharge is poor, despite recent scientific advances. The goals of cardiopulmonary resuscitation (CPR) are to restore circulation and identify and correct an underlying etiology. High-quality compressions remain the foundation of CPR, optimizing coronary and cerebral perfusion pressure. High-quality compressions must be performed at the appropriate rate and depth. Interruptions in compressions are detrimental to management. Mechanical compression devices are not associated with improved outcomes but can assist in several situations.

Airway Management of the Cardiac Arrest Victim

Appropriate airway management is critical to successful cardiac arrest resuscitation. However, the timing and method of airway management during cardiac arrest have traditionally been guided by expert and consensus opinion informed by observational data. In the last 5 years, recent studies, including several randomized controlled trials (RCTs), have provided additional clarity to help guide airway management. This article will review both current data and guidelines for airway management in cardiac arrest, a stepwise approach to airway management, the utility of various airway adjuncts, and best practices for oxygenation and ventilation in the peri-arrest period.

Use of a novel pedal-operated compressor is non-inferior to the use of a standard hand-compressed bag-valve mask

BACKGROUND

The standard bag-valve mask (BVM) used universally requires that a single healthcare practitioner affix the mask to the face with 1 hand while compressing a self-inflating bag with the second hand. Studies have demonstrated that creating a 2-handed seal (with 2 healthcare practitioners) is superior. Our study aims to assess the efficacy of a novel single-practitioner BVM device that uses a foot pedal as the bag compressor, allowing both hands to be available for the seal to facilitate delivery of appropriate tidal volumes during single-practitioner resuscitation.

METHODS

This was a prospective, randomized, cross-over study. Participants with various BVM ventilation experience performed 2 minutes of metronome-guided BVM ventilation using a standard BVM and the pedal-operated compressor on a high-fidelity simulation mannequin. Analysis examining differences in mean tidal volume delivered was conducted using a regression model that adjusted for covariates. A secondary analysis using a series of Wilcoxon tests was conducted to compare differences in the additional out-of-range sensed breaths metrics to compare differences by prior BVM ventilation experience.

RESULTS

A total of 58 subjects participated. The pedal-operated compressor unadjusted mean tidal volume delivered was 446.5 mL (95% confidence interval [CI], 425.9-467.1) compared with 340.6 mL (95% CI, 312.2-369.0) by standard BVM (mean change, 105.9 mL [95% CI, 71.2-140.6]; P < .001). When modeling a generalized estimation equation regression model, standard BVM ventilation provided a mean difference of 105.9 mL less than pedal-operated compressor ventilation after adjusting for covariates (P = 0.01). For the secondary outcome, the pedal-operated compressor did have a significantly lower median number of out-of-range breaths (median, 3; interquartile range [IQR], 1-11.5) compared with the standard device (median, 13.5; IQR, 6-19; P < 0.001).

CONCLUSIONS

Use of a novel pedal-operated compressor may allow a single healthcare practitioner, regardless of prior experience, to deliver consistent, appropriate tidal volumes with more ease compared with the standard BVM during manual respiratory resuscitation.

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.

Opioid-Associated Out-of-Hospital Cardiac Arrest: Distinctive Clinical Features and Implications for Health Care and Public Responses: A Scientific Statement From the American Heart Association

Opioid overdose is the leading cause of death for Americans 25 to 64 years of age, and opioid use disorder affects >2 million Americans. The epidemiology of opioid-associated out-of-hospital cardiac arrest in the United States is changing rapidly, with exponential increases in death resulting from synthetic opioids and linear increases in heroin deaths more than offsetting modest reductions in deaths from prescription opioids. The pathophysiology of polysubstance toxidromes involving opioids, asphyxial death, and prolonged hypoxemia leading to global ischemia (cardiac arrest) differs from that of sudden cardiac arrest. People who use opioids may also develop bacteremia, central nervous system vasculitis and leukoencephalopathy, torsades de pointes, pulmonary vasculopathy, and pulmonary edema. Emergency management of opioid poisoning requires recognition by the lay public or emergency dispatchers, prompt emergency response, and effective ventilation coupled to compressions in the setting of opioid-associated out-of-hospital cardiac arrest. Effective ventilation is challenging to teach, whereas naloxone, an opioid antagonist, can be administered by emergency medical personnel, trained laypeople, and the general public with dispatcher instruction to prevent cardiac arrest. Opioid education and naloxone distributions programs have been developed to teach people who are likely to encounter a person with opioid poisoning how to administer naloxone, deliver high-quality compressions, and perform rescue breathing. Current American Heart Association recommendations call for laypeople and others who cannot reliably establish the presence of a pulse to initiate cardiopulmonary resuscitation in any individual who is unconscious and not breathing normally; if opioid overdose is suspected, naloxone should also be administered. Secondary prevention, including counseling, opioid overdose education with take-home naloxone, and medication for opioid use disorder, is important to prevent recurrent opioid overdose.

Optimizing airway management and ventilation during prehospital advanced life support in out-of-hospital cardiac arrest: A narrative review

Airway management and ventilation are essential components of cardiopulmonary resuscitation to achieve oxygen delivery in order to prevent hypoxic injury and increase the chance of survival. Weighing the relative benefits and downsides, the best approach is a staged strategy; start with a focus on high-quality chest compressions and defibrillation, then optimize mask ventilation while preparing for advanced airway management with a supraglottic airway device. Endotracheal intubation can still be indicated, but has the largest downsides of all advanced airway techniques. Whichever stage of airway management, ventilation and chest compression quality should be closely monitored. Capnography has many advantages and should be used routinely. Optimizing ventilation strategies, harmonizing ventilation with mechanical chest compression devices, and implementation in complex and stressful environments are challenges we need to face through collaborative innovation, research, and implementation.

Is Rescuer Cardiopulmonary Resuscitation Jeopardised by Previous Fatiguing Exercise?

Survival outcomes increase significantly when cardiopulmonary resuscitation (CPR) is provided correctly, but rescuer's fatigue can compromise CPR delivery. We investigated the effect of a 100-m maximal run on CPR and physiological variables in 14 emergency medical technicians (age 29.2 ± 5.8 years, height 171.2 ± 1.1 cm and weight 73.4 ± 13.1 kg). Using an adult manikin and a compression-ventilation ratio of 30:2, participants performed 4-min CPR after 4-min baseline conditions (CPR) and 4-min CPR after a 100-m maximal run carrying emergency material (CPR-run). Physiological variables were continuously measured during baseline and CPR conditions using a portable gas analyzer (K4b2, Cosmed, Rome, Italy) and analyzed using two HD video cameras (Sony, HDR PJ30VE, Japan). Higher VO2 (14.4 ± 2.1 and 22.0 ± 2.5 mL·kg-1·min-1) and heart rate (123 ± 17 and 148 ± 17 bpm) were found for CPR-run. However, the compression rate was also higher during the CPR-run (373 ± 51 vs. 340 ± 49) and between every three complete cycles (81 ± 9 vs. 74 ± 14, 99 ± 14 vs. 90 ± 10, 99 ± 10 vs. 90 ± 10, and, 101 ± 15 vs. 94 ± 11, for cycle 3, 6, 9 and 12, respectively). Fatigue induced by the 100-m maximal run had a strong impact on physiological variables, but a mild impact on CPR emergency medical technicians' performance.

Effectiveness of a Real-Time Ventilation Feedback Device for Guiding Adequate Minute Ventilation: A Manikin Simulation Study

Background and objectives: It is often challenging even for skilled rescuers to provide adequate positive pressure ventilation consistently. This study aimed to investigate the effectiveness of a newly developed real-time ventilation feedback device (RTVFD) that estimates tidal volume (TV) and ventilation interval (VI) in real time. Materials and methods: We conducted a randomised, crossover, manikin simulation study. A total of 26 medical providers were randomly assigned to the RTVFD-assisted ventilation (RAV) first group (n = 13) and the non-assisted ventilation (NV) first group (n = 13). Participants provided ventilation using adult and paediatric bag valves (BVs) for 2 min each. After a washout period, the simulation was repeated by exchanging the participants’ groups. Results: The primary outcome was optimal TV in the RAV and NV groups using adult and paediatric BVs. A secondary outcome was optimal VI in the RAV and NV groups using adult and paediatric BVs. The proportions of optimal TV values were higher for the RAVs when using both adult and paediatric BVs (adult BV: 47.29% vs. 18.46%, p < 0.001; paediatric BV: 89.51% vs. 72.66%, p < 0.001) than for the NVs. The proportions of optimal VI were significantly higher in RAVs when using both adult and paediatric BVs than that in NVs (adult BV: 95.64% vs. 50.20%, p < 0.001; paediatric BV: 95.83% vs. 57.14%, p < 0.001). Additionally, we found that with paediatric BVs, the simulation had a higher OR for both optimal TV (13.26; 95% CI, 9.96–17.65; p < 0.001) and VI (1.32; 1.08–1.62, p = 0.007), regardless of RTVFD use. Conclusion: Real-time feedback using RTVFD significantly improves the TV and VI in both adult and paediatric BVs in a manikin simulation study.

A review of ventilation in adult out-of-hospital cardiac arrest

Out-of-hospital cardiac arrest continues to be a devastating condition despite advances in resuscitation care. Ensuring effective gas exchange must be weighed against the negative impact hyperventilation can have on cardiac physiology and survival. The goals of this narrative review are to evaluate the available evidence regarding the role of ventilation in out-of-hospital cardiac arrest resuscitation and to provide recommendations for future directions. Ensuring successful airway patency is fundamental for effective ventilation. The airway management approach should be based on professional skill level and the situation faced by rescuers. Evidence has explored the influence of different ventilation rates, tidal volumes, and strategies during out-of-hospital cardiac arrest; however, other modifiable factors affecting out-of-hospital cardiac arrest ventilation have limited supporting data. Researchers have begun to explore the impact of ventilation in adult out-of-hospital cardiac arrest outcomes, further stressing its importance in cardiac arrest resuscitation management. Capnography and thoracic impedance signals are used to measure ventilation rate, although these strategies have limitations. Existing technology fails to reliably measure real-time clinical ventilation data, thereby limiting the ability to investigate optimal ventilation management. An essential step in advancing cardiac arrest care will be to develop techniques to accurately and reliably measure ventilation parameters. These devices should allow for immediate feedback for out-of-hospital practitioners, in a similar way to chest compression feedback. Once developed, new strategies can be established to guide out-of-hospital personnel on optimal ventilation practices.

Gastric insufflation during cardiopulmonary resuscitation: A study in human cadavers

INTRODUCTION

Bag-valve-mask ventilation is the first-line ventilation method during cardiopulmonary resuscitation (CPR). Risks include excessive volume delivery and gastric insufflation, the latter increasing the risk of pneumonia. The efficacy of ventilation can also be reduced by airway closure. We hypothesized that continuous chest compression (CC) could limit the risk of gastric insufflation compared to the recommended 30:2 interrupted CC strategy. This experimental study was performed in human "Thiel" cadavers to assess the respective impact of discontinuous vs. continuous chest compressions on gastric insufflation and ventilation during CPR.

METHODS

The 30:2 interrupted CC technique was compared to continuous CC in 5 non-intubated cadavers over a 6 min-period. Flow and Airway Pressure were measured at the mask. A percutaneous gastrostomy allowed measuring the cumulative gastric insufflated volume. Two additional cadavers were equipped with esophageal and gastric catheters instead of the gastrostomy.

RESULTS

For the 7 cadavers studied (4 women) median age of death was 79 [74-84] years. After 6 min of CPR, the cumulative gastric insufflation measured in 5 cadavers was markedly reduced during continuous CC compared to the interrupted CC strategy: (1.0 [0.8-4.1] vs. 5.9 [4.0-5.6] L; p < 0.05) while expired minute ventilation was slightly higher during continuous than interrupted CC (1.9 [1.4-2.8] vs. 1.6 [1.1-2.7] L/min; P < 0.05). In 2 additional cadavers, the progressive rise in baseline gastric pressure was lower during continuous CC than interrupted CC (1 and 2 cmH₂O vs. 12 and 5.8 cmH₂O).

CONCLUSION

Continuous CC significantly reduces the volume of gas insufflated in the stomach compared to the recommended 30:2 interrupted CC strategy. Ventilation actually delivered to the lung is also slightly increased by the strategy.

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.

Can Altering Grip Technique and Bag Size Optimize Volume Delivered with Bag-Valve-Mask by Emergency Medical Service Providers?

INTRODUCTION

Emergency Medical Services (EMS) professionals rely on the bag-valve-mask (BVM) to provide life-saving positive-pressure ventilation in the prehospital setting. Multiple emergency medicine and critical care studies have shown that lung-protective ventilation protocols reduce morbidity and mortality. A recent study has shown that the volumes typically delivered by EMS professionals with the adult BVM are often higher than recommended by lung-protective ventilation protocols. Our primary objective was to determine if a group of EMS professionals could reduce the volume delivered by adjusting the way the BVM was held. Secondary objectives included 1) if the adjusted grip allowed for volumes more consistent with lung-protection ventilation strategies and 2) comparing volumes to similar grip strategies used with a smaller BVM.

METHODS

A patient simulator of a head and thorax was used to record respiratory rate, tidal volume, peak pressure, and minute volume delivered by participants for 1 minute each across 6 different scenarios: 3 different grips (using the thumb and either 3 fingers, 2 fingers, or one finger) with 2 different sized BVMs (adult and pediatric). Trials were randomized by blindly selecting a paper with the scenario listed. A convenience sample of EMS providers was used based on EMS provider and research staff availability.

RESULTS

We enrolled 50 providers from a large, busy, urban hospital-based EMS agency a mean 8.60 (SD = 9.76) years of experience. Median volumes for each scenario were 836.0 mL, 834.5 mL, and 794 mL for the adult BMV (p = 0.003); and 576.0 mL, 571.5 mL, and 547.0 mL for the pediatric BVM (p < 0.001). Across all 3 grips, the pediatric BVM provided more breaths within the recommended volume range for a 70 kg patient (46.4% vs. 0.4%; p < 0.001) with only a 1.1% of breaths below the recommended tidal volume.

CONCLUSION

The study suggests that it is possible to alter the volume provided by the BVM by altering the grip on the BVM. The tidal volumes recorded with the pediatric BVM were above recommended range in 2 of the 3 grips. The volumes of the pediatric BVM were overall more consistent with lung-protective ventilation volumes when compared to all 3 finger-grips of the adult BVM.

To intubate or not: ventilation is the question. A manikin-based observational study

INTRODUCTION

There is a continuous debate concerning the superiority of endotracheal intubation on bag-valve-mask (BVM) ventilation in patients with cardiac arrest. In this manikin-based observational study, we evaluate and compare the performance of manual ventilation through a facemask (BVM) and an endotracheal tube (ETT).

METHODS

One hundred and forty healthcare providers were instructed to manually ventilate a manikin as they would do for a 75 kg adult patient in respiratory arrest. Each one was ventilating both through a facemask and an ETT for a 5 min period in a random order. Ventilatory parameters were measured by the ASL 5000 lung simulator and ventilation performance was analysed using a sliding window method published in a previous study to assess accurately ventilation efficiency.

RESULTS

The mean ventilation rate was high whatever the technique used (24 bpm). A weak relationship between manual ventilation performance and the type of interface used was observed (p=0.0484). The overall rate of adequate ventilation was low even if we noticed a slight improvement when ventilating through an ETT (13.21% vs 7.5% of adequate ventilation). However, the rate of hyperventilation did not differ between mask and tube (79% vs 77%). A significant relationship is observed between professional category, the size of the hand squeezing the bag and manual ventilation performance (p<0.05).

CONCLUSION

Whatever the interface used, healthcare professionals are still struggling to perform manual ventilation efficiently according to international guidelines. Ventilation with an ETT does not prove to be significantly more efficient than with a facemask. It would be therefore important to recentre the debate on controlling ventilatory parameters with current devices. Focusing on training may maximise manual ventilation efficiency and minimise the loss of time during cardiopulmonary resuscitation.

Cardiopulmonary resuscitation quality: [corrected] improving cardiac resuscitation outcomes both inside and outside the hospital: a consensus statement from the American Heart Association

The "2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care" increased the focus on methods to ensure that high-quality cardiopulmonary resuscitation (CPR) is performed in all resuscitation attempts. There are 5 critical components of high-quality CPR: minimize interruptions in chest compressions, provide compressions of adequate rate and depth, avoid leaning between compressions, and avoid excessive ventilation. Although it is clear that high-quality CPR is the primary component in influencing survival from cardiac arrest, there is considerable variation in monitoring, implementation, and quality improvement. As such, CPR quality varies widely between systems and locations. Victims often do not receive high-quality CPR because of provider ambiguity in prioritization of resuscitative efforts during an arrest. This ambiguity also impedes the development of optimal systems of care to increase survival from cardiac arrest. This consensus statement addresses the following key areas of CPR quality for the trained rescuer: metrics of CPR performance; monitoring, feedback, and integration of the patient's response to CPR; team-level logistics to ensure performance of high-quality CPR; and continuous quality improvement on provider, team, and systems levels. Clear definitions of metrics and methods to consistently deliver and improve the quality of CPR will narrow the gap between resuscitation science and the victims, both in and out of the hospital, and lay the foundation for further improvements in the future.

Duration of Ventilations During Cardiopulmonary Resuscitation by Lay Rescuers and First Responders

Background—

The 2010 guidelines for cardiopulmonary resuscitation allow 5 seconds to give 2 breaths to deliver sufficient chest compressions and to keep perfusion pressure high. This study aims to determine whether the recommended short interruption for ventilations by trained lay rescuers and first responders can be achieved and to evaluate its consequence for chest compressions and survival.

Methods and Results—

From a prospective data collection of out-of-hospital cardiac arrest, we used automatic external defibrillator recordings of cardiopulmonary resuscitation by rescuers who had received a standard European Resuscitation Council basic life support and automatic external defibrillator course. Ventilation periods and total compressions delivered per minute during each 2 minutes of cardiopulmonary resuscitation cycle were measured, and the chest compression fraction was calculated. Neurological intact survival to discharge was studied in relation to these factors and covariates. We included 199 automatic external defibrillator recordings. The median interruption time for 2 ventilations was 7 seconds (25th–75th percentile, 6–9 seconds). Of all rescuers, 21% took <5 seconds and 83% took <10 seconds for a ventilation period; 97%, 88%, and 63% of rescuers were able to deliver >60, >70, and >80 chest compressions per minute, respectively. The median chest compression fraction was 65% (25th–75th percentile, 59%–71%). Survival was 25% (49 of 199), not associated with long or short ventilation pauses when controlled for covariates.

Conclusions—

The great majority of rescuers can give 2 rescue breaths in <10 seconds and deliver at least 70 compressions in a minute. Longer pauses for ventilations are not associated with worse outcome. Guidelines may allow longer pauses for ventilations with no detriment to survival.

Update on cardiopulmonary resuscitation guidelines of interest to anesthesiologists

BACKGROUND AND OBJECTIVES

The new cardiopulmonary resuscitation (CPR) guidelines emphasize the importance of high-quality chest compressions and modify some routines. The objective of this report was to review the main changes in resuscitation practiced by anesthesiologists.

CONTENTS

The emphasis on high-quality chest compressions with adequate rate and depth allowing full recoil of the chest and with minimal interruptions is highlighted in this update. One should not take more than ten seconds checking the pulse before starting CPR. The universal relationship of 30:2 is maintained, modifying its order, initiating with chest compressions, followed by airways and breathing (C-A-B instead of A-B-C). The procedure "look, listen, and feel whether the patient is breathing" was removed from the algorithm, and the use of cricoid pressure during ventilations is not recommended any more. The rate of chest compressions was changed for at least one hundred per minute instead of approximately one hundred per minute, and its depth in adults was changed to 5 cm instead of the prior recommendation of 4 to 5 cm. The single shock is maintained, and it should be of 120 to 200 J when it is biphasic; and 360 J when it is monophasic. In advanced cardiac life support, the use of capnography and capnometry to confirm intubation and monitoring the quality of CPR is a formal recommendation. Atropine is no longer recommended for routine use in the treatment of pulseless electrical activity or asystole.

CONCLUSIONS

Updating the phases of the new CPR guidelines is important, and continuous learning is recommended. This will improve the quality of resuscitation and survival of patients in cardiac arrest.

Airway management for the uninitiated

The 21(st) century has witnessed burgeoning interest in airway management. Pertinent basic sciences are covered in numerous texts and lectures. This article presents clinical information required to perform airway management. It serves as a primer for those interested in learning airway management skills. It does not replace extensive practice under the tutelage of expert airway managers.

Cricoid Pressure in Emergency Department Rapid Sequence Tracheal Intubations: A Risk-Benefit Analysis

Cricoid pressure is considered an integral part of patient safety in rapid sequence tracheal intubation and emergency airway management. Cricoid pressure is applied to prevent the regurgitation of gastric contents into the pharynx and subsequent aspiration into the pulmonary tree. This review analyzes the published evidence supporting cricoid pressure, along with potential problems, including increased difficulty with tracheal intubation and ventilation. According to the evidence available, the universal and continuous application of cricoid pressure during emergency airway management is questioned. An awareness of the benefits and potential problems with technique allows the practitioner to better judge when cricoid pressure should be used and instances in which it should be removed.

Comparison of ventilation and cardiac compressions using the Impact Model 730 automatic transport ventilator compared to a conventional bag valve with a facemask in a model of adult cardiopulmonary arrest

PURPOSE

To determine the performance of two person CPR on an instrumented manikin by registered nurses using conventional bag valve mask (BVM) ventilation or the Impact Model 730 automatic transport ventilator (Impact 730, Impact Instrumentation, Inc., West Caldwell, NJ) in CPR mode using a face mask.

DESIGN

Randomized crossover quasi-experimental.

SETTING

Laboratory simulation.

SUBJECTS

Twenty-eight registered nurses trained in performing adult cardiopulmonary resuscitation (CPR).

INTERVENTIONS

Basic Life Support was provided by subjects using a conventional bag valve mask (BVM) ventilation or mask ventilation with an automatic transport ventilator, the Impact 730, which incorporates a metronome to facilitate chest compression timing. Subjects alternated performing 4min of CPR using the BVM or Impact 730 to deliver breaths with a mask while the other subject performed compressions.

MEASUREMENTS AND MAIN RESULTS

Flow, volume and pressure were measured using a pneumotachograph and pressure transducer, and ease of use was measured using a 10cm visual analogue scale. There was no statistical or clinical difference between the actual and recommended tidal lung volume (mean+/-S.D.) delivered by the Impact 730 (-120.4+/-91.5ml) versus the BVM (-119.8+/-187.3+/-ml). Ventilation with the BVM resulted in more (137.7+/-143.9ml) air per breath passing through the simulated lower esophageal sphincter compared to the Impact 730 (14.0+/-16.8ml, p<0.05). The reduced mask leak per breath with the Impact 730 (176.1+/-98.3ml) compared to the BVM (367.6+/-337.7ml, p<0.05) is likely to have resulted from the subject being able to manage the mask with two rather than one hand and is reflected in the higher ease of use score on a 10cm visual analogue scale with the Impact 730 (8.06+/-1.35cm) versus the BVM (6.46+/-2.46cm, p<0.05). Subjects tended to deliver slightly more compressions and breaths when using the BVM.

CONCLUSION

Compared to the BVM, the Impact 730 is as effective, easier to use and limits the amount of gas entering the stomach when used during adult CPR in a simulated setting.

Comparison of ventilation and chest compression performance by bystanders using the Impact Model 730 ventilator and a conventional bag valve with mask in a model of adult cardiopulmonary arrest

"Bystanders" or lay persons are typically the first caregivers to attend to a victim of out-of-hospital cardiopulmonary arrest. Astronaut crew medical officers (CMO) play a similar role to bystanders aboard the International Space Station (ISS). Studies have demonstrated the importance of bystander cardiopulmonary resuscitation (BCPR) for patient survival before the arrival of emergency medical care. Recent apprehension from bystanders about the threat of contracting communicable diseases during BCPR, however, has led to the consideration of other ventilation systems such as the bag-valve mask (BVM) and automatic transport ventilators (ATV). BVM use is called for during CPR aboard the ISS. This study evaluated the ventilation and compression performance of 40 basic CPR-trained bystanders using either a BVM (adult-sized self-inflating bag with face mask) or an ATV (Model 730 ventilator (M730), Impact Instrumentation, Inc., West Caldwell, NJ). Each two-bystander team gave BCPR to a simulated cardiopulmonary arrest victim using the 2-breath/15-compression cycle for 4 min and then switched roles for another 4-min interval. Compared to BVM use, the M730 led to significantly (p<0.05) lower number of breaths, smaller tidal volumes, airway flows, airway pressures, volume of gas entering the stomach per breath and chest compressions for the 4-min period. The M730 also enabled a bystander to meet the recommendation of 4-breath and compression cycles per minute as per Guidelines 2000. Lastly, ease-of-use scores were significantly higher for the M730 compared to the BVM. Overall, the data suggest that the M730 improves the quality of performance for a bystander performing BCPR.

Analysis of non-invasive ventilation effects on gastric inflation using a non-linear mathematical model

A non-linear mathematical model of the oesophagus was developed to study the effects of non-invasive ventilation variables on the severity of gastric inflation. The model was based on the non-linear physical characteristics of biological tissue. The model simulated oesophageal mechanical function during non-invasive ventilation in cardiac arrest (2:30 ventilations/chest compressions cycles) and respiratory arrest (1:5 ventilations/s) as recommended by the European Resuscitation Council (ERC) in its 2005 guidelines for adult basic and advanced life support. Model predictions establish a strong correlation between the expiratory time and the occurrence of gastric inflation. For cardiac arrest, when using ventilation pressure lower than 12 cmH2O, expiratory time between consequent ventilations and time until the occurrence of gastric inflation were linearly dependent (r = 0.98). This linear correlation changed abruptly when airway pressure exceeded the threshold pressure of 12 cmH2O, indicating that air had entered the stomach during the first ventilation. The interval at which the pressure at the distal section of the oesophagus was above the lower oesophageal sphincter (LES) opening pressure was significantly prolonged in the model of cardiac arrest (approximately 5.5 s compared to 3 s in respiratory arrest), thus allowing a greater amount of air to enter the stomach at relatively low airway pressures. During cardiac arrest, the mean pressure at the distal section of the oesophagus and the amplitude of air backflow were higher compared to the mean pressure and amplitude during respiratory arrest. This is also due to the shorter expiratory intervals in the 2:30 ventilations/chest compressions technique. The model indicates that the time required for the air trapped in the oesophagus to completely deflate is approximately 2 s. This may be longer than the expiratory time recommended by the 2005 guidelines. Model predictions support the 2005 guidelines regarding the decrease in the tidal volume and in the inspiratory pressure in an effort to minimise gastric inflation.

Reflection on a patient's airway management during a ward-based resuscitation

BACKGROUND

The bag-valve-mask (BVM) system is a common adjunct used during adult resuscitation to ventilate the lungs and deliver oxygen to patients in cardiopulmonary arrest. Gastric inflation, regurgitation and aspiration are well-documented complications of BVM ventilation, which can have serious consequences for patients.

AIM

The aim of this paper is to review the cause of gastric inflation, regurgitation and aspiration during BVM ventilation and to consider techniques that have been suggested to reduce these problems.

METHOD

Using a reflective model, the author revisits an actual cardiac arrest, and within a structured framework considers the event itself, the context of the event and looks at ways in which practice could be improved in future.

RESULTS

It is clear from the evidence that a reduction in peak airway pressure can reduce the risk of gastric inflation, regurgitation and aspiration. A review of the available research strongly suggests that in expert hands, the most effective means of reducing peak airway pressure is by reducing tidal volume by using a smaller bag.

CONCLUSION

Although the evidence, as presented, for a reduction in bag size is convincing, there appears to be a problem that less regular users do not appear to be able to produce effective tidal volumes when using a smaller bag. If a reduced bag size is standardized, further research using a diverse group of health care workers with the BVM is required before a clear policy can be achieved. It is likely that training and practice will be shown to be important for nursing staff expected to use the smaller BVM.

Basic airway management by junior doctors: assessment and training on human apnoeic subjects in the anaesthetic room*

We assessed the airway management skills of 20 junior doctors on patients in the anaesthetic room, using a self-inflating bag with digital flowmeter to measure exhaled tidal volume. Following induction of anaesthesia the junior doctor attempted to ventilate the patient's lungs with five breaths. If two of these breaths were > 250 ml the assessment was completed. If not, a period of instruction was given followed by a further five-breath assessment. Eight doctors did not need further training; of these, six were senior house officers and seven had been on an Advanced Life Support course. Twelve doctors required instruction and re-assessment. Four were senior house officers and two had been on an Advanced Life Support course. They showed some improvement following the instruction period but never reached the standard of the other eight. Validated courses improve resuscitation skills but hands-on training in the anaesthetic room can also be of benefit in maintaining these skills.

Comparison of mouth-to-mouth, mouth-to-mask and mouth-to-face-shield ventilation by lay persons

OBJECTIVE AND METHODS

A prospective randomised study on 70 volunteers without previous first aid education (42 males, 28 females, mean age 17) was performed to compare mouth-to-mouth ventilation (MMV, n = 24) versus mouth-to-pocket-mask ventilation (MPV, n = 25) and mouth-to-face-shield ventilation (MFV, n =21), and to evaluate if an instruction period of 10 min would be sufficient to teach lay persons artificial ventilation. Every volunteer performed three ventilation series using a bench model of an unprotected airway.

RESULTS

MMV and MPV show higher mean tidal volume (TV) than MFV (values of series 3: 976 +/- 454 and 868 +/- 459 versus 604 +/- 328 ml, P = 0.002 and P = 0.025, respectively). We found a higher inter-individual variation in TV than in previous studies (P = 0.031). The recommended TV of 700-1000 ml was reached in only 23%, most frequently with MPV (MMV 16.7%, MPV 32%, MFV 19%) but the difference was not significant (P = 0.391). However, we found a significantly higher percentage with a TV below 700 ml with MFV (MMV 33.3%, MPV 36%, MFV 66.7% P = 0.047) and a significantly higher percentage of TV exceeding 1000 ml with MMV (MMV 50%, MPV 32%, MFV 14.3%) (P = 0.039). "Stomach" inflation was highest with MMV (79.2%) followed by MPV (52%) and MFV (42.9%) (P = 0.034). We found further differences between the sexes; males produced a higher TV (P = 0.003) and a higher percentage of stomach inflation (P = 0.029).

CONCLUSION

MPV showed the best ventilation quality. It resulted in a more adequate TV than MMV and MFV and lower stomach inflation than MMV. Only a relatively low percentage of ventilations were within the recommended range for TV and this may be related to the short training duration. We found different performances between the sexes, a high inter-individual variation and mainly a low ventilation quality. Therefore, further studies have to focus more on teaching duration, sex differences and ventilation quality.

Beatmung eines ungeschützten Atemwegs

BACKGROUND

Currently 30 chest compressions and 2 ventilations with an inspiratory time of 1 s are recommended during cardiopulmonary resuscitation with an unprotected airway, thus spending about 15% instead of 40% of resuscitation time on ventilation. Time could be gained for chest compressions when reducing inspiratory time from 2 s to 1 s, however, stomach inflation may increase as well.

METHODS

In an established bench model we evaluated the effect of reducing inspiratory time from 2 s to 1 s at different lower oesophageal sphincter pressure (LOSP) levels using a novel peak inspiratory-flow and peak airway-pressure-limiting bag-valve-mask device (Smart-Bag).

RESULTS

A reduction of inspiratory time from 2 s to 1 s resulted in significantly lower peak airway pressure with LOSP of 0.49 kPa (5 cm H2O), 0.98 kPa (10 cm H2O) and 1.47 kPa (15 cm H2O) and an increase with 1.96 kPa (20 cm H2O). Lung tidal volume was reduced with 1 s compared to 2 s. When reducing inspiratory time from 2 s to 1 s, stomach inflation occurred only at a LOSP of 0.49 kPa (5 cm H2O).

CONCLUSIONS

In this model of a simulated unprotected airway, a reduction of inspiratory time from 2 s to 1 s using the Smart-Bag resulted in comparable inspiratory peak airway pressure and lower, but clinically comparable, lung tidal volume. Stomach inflation occurred only at a LOSP of 0.49 kPa (5 cm H2O), and was higher with an inspiratory time of 2 s vs 1 s.

Retention of ventilation skills of emergency nurses after training with the SMART BAG® compared to a standard bag–valve–mask

BACKGROUND AND PURPOSE

Studies show that nurses retain resuscitation skills poorly and that retention of ventilation skills is particularly difficult. We formed the hypothesis that the SMART BAG (SB, O-Two Medical Technologies Inc., Canada), i.e. a bag-valve-mask device with a pressure/flow responsive valve, would assist nurses in providing more efficient ventilation six months after training.

MATERIALS AND METHODS

Prior to training, 39 emergency nurses performed CPR for 2 min, in pairs, using a standard bag-valve-mask device (STBVM, Laerdal, Norway) to assess their base line skills. A CPR training manikin (Simulaids, USA) equipped with a PEEP valve in the oesophagus set at 20 cm H2O was used to measure inspiratory time, tidal volume (Vt), peak pressure and gastric insufflation (GI). Immediately following training they were tested using an O-Two STBVM and a SB. Half of the nurses were retested after three months, the other half after six months. Efficient ventilation was defined as a mean Vt>400 ml and GI<50 ml in 1 min.

RESULTS

Before training, only 16% of nurses ventilated efficiently: 63% had GI and 28% had Vt<400 ml. Three months after training the efficiency of the STBVM and the SB was high (81 and 75%, respectively). Six months after training, there was a trend towards higher efficiency for the SB (63%) compared to the STBVM (25%) (p=0.07). For instances with the STBVM producing a Vt>400 ml, those without GI had a lower peak pressure than those with GI (7.8 cm H2O versus 17.7 cm H2O, p=0.0001) and showed a trend towards a longer inspiratory time (1.28 s versus 1.08 s, p=0.08). Of all efficient ventilations with a STBVM, 26% had a Vt>600 ml.

CONCLUSIONS

Six months after training, nurses ventilated at least as efficiently with the SB, compared with the STBVM. This illustrates the ability of the SB to compensate for the deterioration over time in skill. On the other hand, training with a STBVM should focus primarily on prolonging the inspiratory time, and therefore the peak pressure, whilst maintaining an adequate Vt.

In-water resuscitation: a pilot evaluation

INTRODUCTION

The first and most important treatment for the apnoeic drowning victim is the rapid alleviation of hypoxia by artificial ventilation. Recent studies have suggested that commencing resuscitative efforts with the victim still in the water may be beneficial. The aim of this pilot study was to evaluate the feasibility and efficacy of in-water unsupported rescue breathing.

METHODS

Three lifeguards were taught how to perform in-water unsupported rescue breathing. Ventilation volume, inflation duration were recorded from a modified Laerdal resuscitation manikin. The rescue duration was recorded and compared to a rescue undertaken without in-water resuscitation.

RESULTS

The three lifeguards performed between seven and nine ventilations during each simulated rescue. This gave average inflation volumes for each lifeguard of 711 ml (S.D. 166), 750 ml (S.D. 108), 629 ml (S.D. 182) and average inflation duration of 0.8s (S.D. 0.3), 0.9s (S.D. 0.2) and 0.6s (S.D. 0.1). The rescue duration was increased from an average time of 1 min 10 s to 1 min 24 s by performing in-water resuscitation.

CONCLUSION

This study has demonstrated the feasibility and potential efficacy of in-water unsupported rescue breathing with a victim in deep water. Furthermore, the technique was not associated with an undue prolongation of the rescue duration over a 50 m rescue. In circumstances where the trained lifeguard finds themselves with an apnoeic victim in the water, with no buoyant rescue aid available, they may consider the application of in-water, unsupported rescue breathing, especially if recovery to dry land is likely to be delayed. The effectiveness of this technique, however, remains to be proven in the open water environment.

Two-rescuer CPR results in hyperventilation in the ventilating rescuer

The "Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care--International Consensus on Science" recommend a tidal ventilation volume of 10 ml/kg body-weight without the use of supplemental oxygen during two-rescuer adult cardiopulmonary resuscitation (CPR). This relates to a ventilation volume of about 6.4 l/min. Additionally, the first aid provider ventilating the victim will breathe for him/herself during the external chest compression period adding another 3.2 l/min of ventilation. Finally, a deep breath is recommended before each ventilation to increase the end-expiratory oxygen concentration of the air exhaled. To investigate the effects of these recommendations, 20 healthy volunteers were asked to perform two-rescuer CPR in a lung model connected to a BLS-manikin. End-tidal carbon dioxide, oxygen saturation, and heart rate were recorded continuously. Capillary blood gas samples were collected and non-invasive blood pressure was recorded prior to the start of external chest compressions and immediately after the end of each measurement period. Furthermore, hyperventilation related symptoms reported by the volunteers were also recorded. The data reveal a significant decrease in capillary and end-tidal carbon dioxide pressure in the volunteers (P < 0.001). Additionally, in 75% of test persons multiple hyperventilation associated symptoms occurred. Ventilation during two-rescuer CPR performed according to the Guidelines 2000 may cause injury to the health of first aid providers. To minimize hyperventilation, both rescuers should exchange their positions at intervals of 3-5 min. These data challenge the recommendation to take a deep breath prior to each ventilation.

Effects of decreasing inspiratory times during simulated bag-valve-mask ventilation

During CPR, an inspiratory time of 2 s is recommended when the airway is unprotected; indicating that approximately 30% of the resuscitation attempt is spent on ventilation, but not on chest compressions. Since survival rates may not decrease when ventilation levels are relatively low, and uninterrupted chest compressions with a constant rate of approximately 100/min have been shown to be lifesaving, it may be beneficial to cut down the time spent on ventilation, and instead, increase the time for chest compressions. In an established bench model of a simulated unprotected airway, we evaluated if inspiratory time can be decreased from 2 to 1 s at different lower oesophageal sphincter pressure (LOSP) levels during ventilation with a bag-valve-mask device. In comparison with an inspiratory time of 2 s, 1 s resulted in significantly (p < 0.001) higher peak airway pressure and peak inspiratory flow rate, while lung tidal volumes at all LOSP levels were clinically comparable. Neither ventilation strategy produced stomach inflation at 20 cmH2O LOSP, and 1 s versus 2 s inspiratory time did not produce significantly higher (mean +/- S.D.) stomach inflation at 15 (8 +/-9 ml versus 0 +/- 0 ml; p < 0.01) and 10 cmH2O LOSP (69 +/- 20 ml versus 34 +/- 18 ml; p < 0.001), and significantly lower stomach inflation at 5 cmH2O LOSP (219 +/- 16 ml versus 308 +/- 21 ml; p < 0.001) per breath. Total cumulative stomach inflation volume over constantly decreasing LOSP levels with an inspiratory time of 2 s versus 1 s was higher (6820 ml versus 5920 ml). In conclusion, in this model of a simulated unprotected airway, a reduction of inspiratory time from 2 to 1 s resulted in a significant increase of peak airway pressure and peak inspiratory flow rate, while lung tidal volumes remained clinically comparable (up to approximately 15% difference), but statistically different due to the precise measurements. Theoretically, this may increase the time available for, and consequently the actual number of, chest compressions during CPR by approximately 25% without risking an excessive increase in stomach inflation.

Verkürzte Inspirationszeit während der Beatmung eines ungeschützten Atemweges

BACKGROUND

In an unprotected airway during cardiopulmonary resuscitation, two ventilations with an inspiratory time of 2 s after 15 chest compressions are recommended. Therefore, approximately 30% of the resuscitation attempt is spent on ventilation. Since survival rates did not decrease sharply when minute ventilation levels were relatively low, and uninterrupted chest compressions with a constant rate of approximately 100/min have been shown to be lifesaving, it may be beneficial to decrease the time spent on ventilation and instead, increase the time for chest compressions.

METHODS

In an established bench model of a simulated, unprotected airway with increased airway resistance, we evaluated if inspiratory time can be decreased from 2 to 1 s at different lower oesophageal sphincter pressure (LOSP) levels during ventilation with a bag-valve-mask device.

RESULTS

An inspiratory time of 2 vs. 1 s resulted in significantly lower peak airway pressure, while lung tidal volume was significantly higher at an inspiratory time of 2 s and a LOSP of 5 cm H(2)O (480+/-20 vs. 380+/-30 ml) and 10 cm H(2)O (630+/-50 vs. 440+/-20 ml) and significantly lower at a LOSP of 15 cm H(2)O (470+/-70 vs. 540+/-20 ml). While neither ventilation strategy produced stomach inflation at 20 cm H(2)O LOSP, 1 vs. 2 s inspiratory time produced significantly higher stomach inflation at 15 cm H(2)O LOSP (8+/-11 vs. 0 ml) and significantly lower stomach inflation at a LOSP of 5 cm H(2)O (359+/-31 vs. 375+/-29 ml) and 10 cm H(2)O (28+/-13 vs. 36+/-12 ml) per breath.

CONCLUSION

In this model of a simulated, unprotected airway, a reduction of inspiratory time from 2 to 1 s resulted in a significant increase of peak airway pressure, while lung tidal volumes and stomach inflation volumes were statistically different but clinically comparable.

["Topless" cardiopulmonary resuscitation. Fashion or science?]

A decade after the onset of a discussion whether ventilation could be omitted from bystander basic life support (BLS) algorithms, the state of the evidence is reevaluated. Initial animal studies and a prospective randomized patient trial had suggested that omission of ventilation during the first minutes of lay cardiopulmonary resuscitation (CPR) did not impair patient outcomes. More recent studies demonstrate, however, that this may hold true only in very specific scenarios, and that the chest compression-only technique was never superior to standard BLS. Instead of calling basics of BLS training and practice into question, more and better training of lay persons and professionals appears mandatory, and targeted use of dispatcher-guided telephone CPR should be evaluated and, if it improves outcome, it should be encouraged. Future studies should focus much less on the omission but on the optimization of ventilation under the specific conditions of CPR.

Developing a Strategy to Improve Ventilation in an Unprotected Airway with a Modified Mouth-to-Bag Resuscitator in Apneic Patients

The strategies to ensure safety during ventilation of an unprotected airway are limiting airway pressure and/or inspiratory flow. In this prospective, randomized study we assessed the effect of face mask ventilation with small tidal volumes in the modified mouth-to-bag resuscitator (maximal volume, 500 mL) versus a pediatric self-inflatable bag versus automatic pressure-controlled ventilation in 40 adult apneic patients during induction of anesthesia. The mouth-to-bag resuscitator requires the rescuer to blow up a balloon inside the self-inflating bag that subsequently displaces air which then flows into the patient's airway. Respiratory variables were measured with a pulmonary monitor (CP-100). Mouth-to-bag resuscitator and pressure-controlled ventilation resulted in significantly lower (mean +/- sd) peak airway pressure (8 +/- 2 and 8 +/- 1 cm H(2)O), peak inspiratory flow rate (0.7 +/- 0.1 and 0.7 +/- 0.1 L/s), and larger inspiratory time fraction (33% +/- 5% and 47% +/- 2%) in comparison to pediatric self-inflating bag ventilation (12 +/- 3 cm H(2)O; 1 +/- 0.2 L/s; 27% +/- 4%; all P < 0.001). The tidal volumes were similar between groups. No stomach inflation occurred in either group. We conclude that using a modified mouth-to-bag resuscitator or automatic pressure-controlled ventilation with similar small tidal volumes during face mask ventilation resulted in an approximately 25% reduction in peak airway pressure when compared with a standard pediatric self-inflating bag.

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.

A comparison between over-the-head and standard cardiopulmonary resuscitation

BACKGROUND

Standard cardiopulmonary resuscitation (CPR) is performed by kneeling adjacent to the side of the casualty. In certain circumstances it may be difficult or impossible to perform CPR in this position, for example in confined spaces such as a narrow corridor, aircraft or train gangway. The aim of this study was to investigate the technique of over-the-head CPR (OTH CPR), where the CPR provider kneels above the casualty and performs chest compressions OTH of the casualty.

METHODS

Twenty volunteers were randomised to a cross over trial where they performed standard and OTH CPR at a 7-day interval. Compression and ventilation variables were recorded on the Laerdal Resusci Annie VAM system.

RESULTS

Chest compression depth and ventilation volume declined over time (0-3 min P < 0.001). There was no difference in compression rate, depth, duty cycle or ventilation rate, inflation rate and ventilation volume between techniques. Hand position was incorrect more frequently in the standard compared to the OTH group (incorrect compressions 300 versus 76, respectively, P < 0.001) due principally to a greater proportion of low positioned compressions in the standard CPR group.

CONCLUSION

OTH CPR appears equally effective as standard CPR with some marginal advantages in correct hand placement. We suggest that in situations where it is not possible to perform standard CPR, OTH CPR may be considered as a suitable alternative.