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

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.

Airway management and ventilation techniques in resuscitation during advanced life support: an update

For many years, ventilation has been an essential part of advanced life support (ALS) in cardiopulmonary resuscitation (CPR). Nevertheless, there is little evidence about the best method of ventilation during resuscitation for both out-of-hospital cardiac arrest (OHCA) and inhospital cardiac arrest (IHCA) patients. Effective ventilation is one of the two main keys to successful resuscitation. In this context, the question always arises as to which airway management, along with which ventilation mode, constitutes the best strategy. Conventional ventilation modes are not designed for cardiac arrest and show important limitations that must be considered when used in CPR. Manual ventilation without the use of an automated transport ventilator (ATV) could be shown to be uncontrolled in applied volumes and pressures and should be avoided. Mechanical ventilation with an ATV is therefore superior to manual ventilation, but both volume- and pressure-controlled ventilation modes are significantly influenced by chest compressions. With the newly designed chest compression synchronized ventilation (CCSV), a special ventilation mode for resuscitation is available. Further research should be conducted to obtain more evidence of the effect of ventilation during CPR on outcomes following OHCA and not only about how to secure the airway for ventilation during CPR.

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.

Is the occurrence of reversed airflow in manual ventilation during cardiopulmonary resuscitation associated with reduced net tidal volumes?

Background

During cardiopulmonary resuscitation, following advanced airway placement, chest compressions and ventilations are performed simultaneously. During inspiration, chest compressions and positive pressure ventilation exert opposite forces on the respiratory system, frequently resulting in reversed airflow.

Methods

Following endotracheal intubation, a flow sensor was connected to the respiratory circuit of intubated, adult out-of-hospital cardiac arrest patients receiving manual chest compressions and manual ventilations. Chest compression parameters were measured using an accelerometer. Inspiratory and expiratory volumes during the inspiratory phase of positive pressure ventilations were quantified. Duration of the inspiratory and expiratory phases was calculated.

Results

In this study, 25 patients were included, 682 ventilations were analyzed. Reversed airflow was observed in 23 patients, occurring 389 times during 270 ventilations. Median volume of reversed airflow was 2 mL (IQR 1.4-7 mL). There was no difference between net tidal volumes of ventilations during which reversed airflow did (median 420 mL, IQR 315-549) or did not occur (median 406 mL, IQR 308-530). When reversed airflow occurred, the duration of the inspiratory phase was longer (median 1.2 sec, IQR 0.9-1.4) compared to ventilations without reversed airflow (median 0.9 sec, IQR 0.9-1.4). Univariate analysis showed a weak correlation between chest compression depth and volume of reversed airflow.

Conclusion

Reversed airflow frequently occurs during cardiopulmonary resuscitation. Volumes of reversed airflow were small, showing a weak correlation with chest compression depth. The occurrence of reversed airflow was not associated with reduced net tidal volumes.

The effects of mechanical versus bag-valve ventilation on gas exchange during cardiopulmonary resuscitation in emergency department patients: A randomized controlled trial (CPR-VENT)

INTRODUCTION

Effective ventilation is crucial for successful cardiopulmonary resuscitation (CPR). Previous studies indicate that higher arterial oxygen levels (PaO2) during CPR increase the chances of successful resuscitation. However, the advantages of mechanical ventilators over bag-valve ventilation for achieving optimal PaO2 during CPR remain uncertain.

METHOD

We conducted a randomized trial involving non-traumatic adult cardiac arrest patients who received CPR in the ED. After intubation, patients were randomly assigned to ventilate with a mechanical ventilator (MV) or bag valve ventilation (BV). In MV group, ventilation settings were: breath rate 10/minute, tidal volume 6-7 ml/kg, inspiratory time 1 second, positive end-expiratory pressure 0 cm water, inspiratory oxygen fraction (FiO2) 100%. The primary outcome was to compare the difference in PaO2 from arterial blood gases (ABG) obtained 4-10 minutes later during CPR between both groups.

RESULTS

Sixty patients were randomized (30 in each group). The study population consisted of: 57% male, median age 62 years, 37% received bystander CPR, and 20% had an initial shockable rhythm. Median time from arrest to intubation was 24 minutes. The median PaO2 was not significantly different in the BV compared to MV [36.5 mmHg (14.0-70.0) vs. 29.0 mmHg (15.0-70.0), P = 0.879]. Other ABG parameters and rates of return of spontaneous circulation and survival were not different.

CONCLUSIONS

In ED patients with refractory cardiac arrest, arterial oxygen levels during CPR were comparable between patients ventilated with MV and BV. Mechanical ventilation is at least feasible and safe during CPR in intubated cardiac arrest patients.

Effect of a Real-Time Audio Ventilation Feedback Device on the Survival Rate and Outcomes of Patients with Out-of-Hospital Cardiac Arrest: A Prospective Randomized Controlled Study

The purpose of this study was to evaluate the effect of real-time audio ventilation feedback on the survival of patients with an out-of-hospital cardiac arrest (OHCA) during advanced cardiac life support (ACLS) performed by paramedics. This research was a prospective randomized controlled study performed in Busan, South Korea, from July 2022 to December 2022. This study included 121 patients, ages 19 and up, who were transferred to the study site, excluding 91 patients who did not receive CPR under a doctor's direction as well as those who had a '(DNR)' order among 212 adult CA patients. OHCA patients' clinical prognosis was compared by being randomly assigned to either a general manual defibrillator (NVF) group (N = 58) or a manual defibrillator with an audio ventilation feedback (AVF) group (N = 63). To verify the primary outcome, the cerebral performance category (CPC), return of spontaneous consciousness (ROSC), 30h survival, and survival discharge were compared. Multivariate logistic regression was conducted to analyze the association between the audio-feedback manual defibrillator (AVF) and the ROSC of OHCA patients. This study analyzed 121 patients among 212 OHCA patients. The ROSC (AVF group: 32 {26.4%} vs. NVF group: 21 {17.3%}), 24 h survival (AVF group: 24 {19.8%} vs. NVF group: 11 {9.0%}), and survival discharge (AVF group: 12 {9.9%} vs. NVF group: 6 {4.9%}) were higher in the AVF group than the NVF group. However, upon analyzing CPC scores in the surviving patients between the two groups, there was no significant difference (AVF group: 4.1 ± 1.23 vs. NVF group:4.7 ± 1.23, p = 1.232). Multivariate logistic regression analysis showed that the use of AVF was associated with a higher ROSC (odds ratio {OR}, 0.46; 95% confidence interval {CI}, 0.23-0.73; p < 0.01) and higher survival at 30 h (OR, 0.63; 95% CI, 0.41-0.98; p = 0.01).

Developments in Post-Resuscitation Care for Out-of-Hospital Cardiac Arrests in Adults-A Narrative Review

This review focuses on current developments in post-resuscitation care for adults with an out-of-hospital cardiac arrest (OHCA). As the incidence of OHCA is high and with a low percentage of survival, it remains a challenge to treat those who survive the initial phase and regain spontaneous circulation. Early titration of oxygen in the out-of-hospital phase is not associated with increased survival and should be avoided. Once the patient is admitted, the oxygen fraction can be reduced. To maintain an adequate blood pressure and urine output, noradrenaline is the preferred agent over adrenaline. A higher blood pressure target is not associated with higher rates of good neurological survival. Early neuro-prognostication remains a challenge, and prognostication bundles should be used. Established bundles could be extended by novel biomarkers and methods in the upcoming years. Whole blood transcriptome analysis has shown to reliably predict neurological survival in two feasibility studies. This needs further investigation in larger cohorts.

Mechanical ventilation with ten versus twenty breaths per minute during cardio-pulmonary resuscitation for out-of-hospital cardiac arrest: A randomised controlled trial

AIM OF THE STUDY

This study sought to assess the effects of increasing the ventilatory rate from 10 min^-1 to 20 min^-1 using a mechanical ventilator during cardio-pulmonary resuscitation (CPR) for out-of-hospital cardiac arrest (OHCA) on ventilation, acid-base-status, and outcomes.

METHODS

This was a randomised, controlled, single-centre trial in adult patients receiving CPR including advanced airway management and mechanical ventilation offered by staff of a prehospital physician response unit (PRU). Ventilation was conducted using a turbine-driven ventilator (volume-controlled ventilation, tidal volume 6 ml per kg of ideal body weight, positive end-expiratory pressure (PEEP) 0 mmHg, inspiratory oxygen fraction (FiO₂) 100%), frequency was pre-set at either 10 or 20 breaths per minute according to week of randomisation. If possible, an arterial line was placed and blood gas analysis was performed.

RESULTS

The study was terminated early due to slow recruitment. 46 patients (23 per group) were included. Patients in the 20 min^-1 group received higher expiratory minute volumes [8.8 (6.8-9.9) vs. 4.9 (4.2-5.7) litres, p < 0.001] without higher mean airway pressures [11.6 (9.8-13.6) vs. 9.8 (8.5-12.0) mmHg, p = 0.496] or peak airway pressures [42.5 (36.5-45.9) vs. 41.4 (32.2-51.7) mmHg, p = 0.895]. Rates of ROSC [12 of 23 (52%) vs. 11 of 23 (48%), p = 0.768], median pH [6.83 (6.65-7.05) vs. 6.89 (6.80-6.97), p = 0.913], and median pCO₂ [78 (51-105) vs. 86 (73-107) mmHg, p > 0.999] did not differ between groups.

CONCLUSION

20 instead of 10 mechanical ventilations during CPR increase ventilation volumes per minute, but do not improve CO₂ washout, acidaemia, oxygenation, or rate of ROSC.

CLINICALTRIALS

gov Identifier: NCT04657393.

Mechanical ventilation during cardiopulmonary resuscitation: influence of positive end-expiratory pressure and head-torso elevation

BACKGROUND

Efficient ventilation is important during cardiopulmonary resuscitation (CPR). Nevertheless, there is insufficient knowledge on how the patient's position affects ventilatory parameters during mechanically assisted CPR. We studied ventilatory parameters at different positive end-expiratory pressure (PEEP) levels and when using an inspiratory impedance valve (ITD) during horizontal and head-up CPR (HUP-CPR).

METHODS

In this human cadaver experimental study, we measured tidal volume (V_T) and pressure during CPR at different randomized PEEP levels (0, 5 or 10 cmH₂O) or with an ITD. CPR was performed, in the following order: horizontal (FLAT), at 18° and then at 35° head-thorax elevation. During the inspiratory phase we measured the net tidal volume (V_T) adjusted to predicted body weight (V_TPBW), reversed airflow (RAF), and maximum and minimum airway pressure (P_max and P_min).

RESULTS

Using ten thawed fresh-frozen cadavers we analyzed the inspiratory phase of 1843 respiratory cycles, 229 without CPR and 1614 with CPR. In a mixed linear model, thoracic position and PEEP significantly impacted V_TPBW (p < 0.001 for each), and the insufflation time, thoracic position and PEEP significantly affected the RAF (p < 0.001 for each) and P_max (p < 0.001). For P_min, only PEEP was significant (p < 0.001). In subgroup analysis, at 35° V_TPBW and P_max were significantly reduced compared with the flat or 18° position.

CONCLUSION

When using mechanical ventilation during CPR, it seems that the PEEP level and patient position are important determinants of respiratory parameters. Moreover, tidal volume seems to be lower when the thorax is positioned at 35°.

The combination of chest compression synchronized ventilation and aortic balloon occlusion improve the outcomes of cardiopulmonary resuscitation in swine

Aim

The primary mission of cardiopulmonary resuscitation (CPR) is to provide adequate blood flow and oxygen delivery for restoring spontaneous circulation from cardiac arrest (CA) events. Previously, studies demonstrated that chest compression synchronized ventilation (CCSV) improved systemic oxygen supply during CPR, and aortic balloon occlusion (ABO) augments the efficacy of external CPR by increasing blood perfusion to vital organs. However, both them failed to make a significant improvement in return of spontaneous circulation (ROSC). In this study, we investigated the effects of combined CCSV and ABO on the outcomes of CPR in swine.

Methods

Thirty-one male domestic swine were subjected to 8 min of electrically induced and untreated CA followed by 8 min of CPR. CPR was performed by continuous chest compressions and mechanical ventilation. At the beginning of CPR, the animals were randomized to receive intermittent positive pressure ventilation (IPPV, n = 10), CCSV (n = 7), IPPV + ABO (n = 7), or CCSV + ABO (n = 7). During CPR, gas exchange and systemic hemodynamics were measured, and ROSC was recorded. After resuscitation, the function and injury biomarkers of vital organs including heart, brain, kidney, and intestine were evaluated.

Results

During CPR, PaO₂ was significantly higher accompanied by significantly greater regional cerebral oxygen saturation in the CCSV and CCSV + ABO groups than the IPPV group. Coronary perfusion pressure, end-tidal carbon dioxide, and carotid blood flow were significantly increased in the IPPV + ABO and CCSV + ABO groups compared with the IPPV group. ROSC was achieved in five of ten (IPPV), five of seven (CCSV), six of seven (IPPV + ABO), and seven of seven (CCSV + ABO) swine, with the rate of resuscitation success being significantly higher in the CCSV + ABO group than the IPPV group (P = 0.044). After resuscitation, significantly improved myocardial and neurological function, and markedly less cardiac, cerebral, renal, and intestinal injuries were observed in the CCSV + ABO group compared with the IPPV group.

Conclusion

The combination of CCSV and ABO improved both ventilatory and hemodynamic efficacy during CPR, promoted ROSC, and alleviated post-resuscitation multiple organ injury in swine.