Cardiac arrest management has long been dominated by algorithms, but I’m increasingly skeptical of how this fits with expert clinical practice. For the masses they are great! Simple algorithms are reproducible, teachable, and scalable, and they have been a great success for many patients who are alive as a result. But they are also blunt instruments applied to what is increasingly recognised as a complex physiological problem, that is quite bespoke to individual patients.
Whatever I think about algorithms, CPR is an essential component of resuscitation and is the cornerstone of any other intervention. But do we do it well all the time? The answer is no, as evidenced by a whole range of papers that have examined the true effectiveness of CPR. So how can we optimise bespoke CPR to individual patients? That might make a difference….
This week we have a paper in JAMA Internal Medicine, alongside its accompanying editorial, that challenges us to think again about whether we are compressing in the right place and, more importantly, whether improving physiology translates into better patient outcomes. We know that not all chests are the same. Not all hearts sit in the same place. And yet we still teach everyone to compress the same bit of sternum, as if anatomy politely aligns itself for our convenience. So can we make this better? Can TOE help?
Optimising CPR is something we have talked a lot about on stemlyns, particularly in relation to the use of arterial lines and chasing DBP. An alternative approach is to use TOE to actually look at the heart. With a TOE you can visualise compressions in real time and as a result adjust and optimse your CPR. In theory that makes a lot of sense and fits with a physiologically targets (maybe anatomically targeted in this case) resuscitation. So can we make this better? Can TOE help?
If you’re unfamiliar with TOE you can watch this video which gives a short intro into TOE in Cardiac arrest. Also note that the study is from Taiwan and they spell Oesophagus differently and so they refer to TEE, whereas we use TOE.
Out-of-hospital cardiac arrest (OHCA) still has pretty low rates of survival. In the UK it’s less than 10%. We have made progress in some areas, improvements in bystander cardiopulmonary resuscitation (CPR) and defibrillation have helped survival rates improve, but only modestly. Our big goal is to get patients who survive with favourable neurological outcome but this remains far too low.
High-quality chest compressions are key to success as they bridge the time between arrest and ROSC. Our current guidelines recommend compressions delivered to the lower half of the sternum. However, these recommendations are arguably based more on giving a simple/teachable approach rather than strong physiological evidence. In fact we now know that CPR is often in the wrong place to get maximal output and that there is a lot of variation between patients. Similarly we recommend a standard amount of compression for simplicity, but in reality patients differ here as well. Imaging studies, including those using transoesophageal echocardiography (T)E), show that the standard hand position frequently results in compression of the aortic root +/- the left ventricle, and if you have that you seriously diminsh the cardiac output. So basically position, depth and probably frequency really matter. Animal studies and observational human data suggest that targeting left ventricular compression improves haemodynamic parameters such as coronary perfusion pressure (we talk a lot about this on stemlyns, but in reality CPP is targeted using DBP), and end-tidal carbon dioxide (ETCO₂), both of which are associated with better outcomes.
TOE offers a potential solution. Unlike transthoracic echocardiography, it allows continuous imaging during CPR without interrupting compressions. This makes it theoretically ideal for identifying the optimal site of compression and dynamically adjusting technique in real time, but does it actually make a difference?
The study by Chu et al., supported by the accompanying editorial, tested this in a cluster randomised trial. The abstract is below. As always, we recommend you erad that full paper and come to your own conclusions.
Importance Cardiopulmonary resuscitation (CPR) guidelines recommend chest compressions at the lower half of the sternum. This may lead to aortic valve compression, which is associated with poor outcomes, while compressions over the left ventricle are seldom achieved.
Abstract
Objective To test the hypothesis that transesophageal echocardiography (TEE) guidance during CPR to avoid aortic valve compression and target the left ventricle would improve outcomes in patients with nontraumatic out-of-hospital cardiac arrest compared with conventional CPR.
Design, Setting, and Participants This cluster-randomized clinical trial (the EXECT-CPR study) was conducted from June 26 to November 19, 2023, at 1 tertiary medical center in Taiwan. Participants were adults who consecutively presented to the emergency department (ED) with nontraumatic out-of-hospital cardiac arrest. Exclusion criteria were prehospital return of spontaneous circulation, extracorporeal CPR, contraindications to TEE, prior do-not-resuscitate orders, and obvious signs of death. Complete blinding was not feasible; the allocation schedule was disclosed only to the principal investigator.
Intervention Post–ED arrival CPR at TEE-guided (avoid aortic-valve compression and target the left ventricle) or guideline-recommended (the lower half of the sternum) site.
Main Outcomes and Measures The primary outcome was a sustained return of spontaneous circulation (≥20 minutes). Secondary outcomes were any return of spontaneous circulation, survival to intensive care unit admission, survival to hospital discharge, cerebral performance category of 2 or lower at discharge, and intra-CPR end-tidal carbon dioxide levels.
Results A total of 132 patients underwent randomization (66 in each group; median [IQR] age, 68 [55-74] years; 87 [66%] male). The primary outcome was similar between groups (TEE-guided group, 29 [44%]; conventional group, 26 [39%]; cluster-adjusted odds ratio, 1.21; 95% CI, 0.64-2.29). The secondary outcomes also did not significantly differ, except for higher intra-CPR end-tidal carbon dioxide levels in the TEE-guided group during the 11th to 20th minutes after arrival. Adverse event rates related to TEE and CPR were comparable.
Conclusions and Relevance In this randomized clinical trial among adults transported to the emergency department with ongoing CPR for nontraumatic out-of-hospital cardiac arrest, TEE-guided CPR with an adjusted compression site after arrival did not significantly improve clinical outcomes compared with conventional CPR, although it produced potential hemodynamic benefits without increasing adverse events. Given that the trial was underpowered due to optimistic effect size assumptions, these neutral findings should be interpreted with caution.
What kind of study is this?
This is a cluster randomised clinical trial (the EXECT-CPR trial) conducted at a single tertiary emergency department in Taiwan.
Patients were allocated to receive either TOE-guided CPR or conventional guideline-directed CPR based on time blocks, rather than individual randomisation. This design reflects the practical challenges of delivering an intervention that requires trained operators and equipment availability (there is a significant investment needed for both if you are thinking about this).
The intervention involved using TOE during ongoing resuscitation to identify the area of maximal compression and adjust the position of chest compressions to target the left ventricle while avoiding the aortic valve.
The comparator group received standard CPR according to current guidelines, with compressions delivered to the lower half of the sternum.
As with many resuscitation studies, blinding was not feasible. However, allocation concealment at the level of the treating team was attempted through the cluster design.
Tell me about the patients
The study enrolled 132 adult patients with non-traumatic OHCA who arrived at the emergency department with ongoing CPR. Note that although this study talks about OHCA, the intervention was delivered once the patient arrived in hospital. This is a key issue for me. If the point of TOE is to optimise compressions, then surely it needs to move as close as possible (in time and space) to the point of the arrest. If the patient has poor quality CPR up to the point of arrival in the ED, is that simply too late?
Because this is actually an ED study, these were not early arrests but patients who had already undergone prehospital resuscitation. The median total prehospital time was approximately 30 minutes, and patients were profoundly acidotic on arrival, with mean pH values around 6.85.
Baseline characteristics were broadly similar between groups. The median age was 68 years, and approximately two-thirds of patients were male. Rates of bystander CPR and initial shockable rhythms were consistent with typical OHCA populations, although the prolonged arrest duration suggests a population with a relatively poor prognosis.
Importantly, most patients received mechanical CPR during transport and in the emergency department. This has implications for the feasibility of repositioning compressions and for the generalisability of findings to systems where manual CPR predominates as many m-CPR systems cannot really be moved that much. On my BASICS scheme we are now using the CORPULS device which is adjustable, but on HEMS and in hospital we still use the LUCAS which you can only move a small amount on the chest (and often slips back to midline).
What were the measured outcomes in this study?
The primary outcome was sustained return of spontaneous circulation (ROSC), defined as ROSC lasting at least 20 minutes. This is not really what we want of course, as neurologically intact survival is more important, but as an early exploration of the technology and as an interim measure it is reasonable.
Secondary outcomes included:
- Any ROSC
- Survival to intensive care unit admission
- Survival to hospital discharge
- Neurological outcome at discharge (cerebral performance category ≤2)
- End-tidal carbon dioxide (ETCO₂) during resuscitation
ETCO₂ is relevant, as it serves as a surrogate marker of perfusion and CPR quality.
What are the main results?
The overall picture was one that did not show a big difference
- Sustained ROSC occurred in 44% of the TOE group versus 39% in the control group (no statistically significant difference, but the numbers are too small to show anything other than a huge difference, and 5% may be important if shown in other trials).
- Rates of any ROSC (50% vs. 50%) and survival to ICU admission (30% vs. 30%) were identical between groups.
- There was no improvement in survival to hospital discharge. (4% for standard care vs. 0%)
- No patients in the TOE group survived with favourable neurological outcome, but there again, none survived with a favourable score in the conventional group either. In other words no patients survived.
However:
- ETCO₂ levels were higher in the TEE-guided group during the later phases of resuscitation, suggesting improved haemodynamics.
In addition, TOE frequently led to repositioning of compressions, with approximately 80% of patients requiring adjustment to achieve left ventricular targeting.
Safety outcomes, including complications related to CPR and TEE, were similar between groups.
How robust are the results?
This is a good study on an important question, but as with all studies there are caveats.
First, the issue of timing. These patients had already experienced prolonged cardiac arrest prior to enrolment. By the time TOE was used and compression location optimised, many patients had undergone 30 to 50 minutes of total ischaemia. At this stage, the likelihood of meaningful recovery is low, regardless of improvements in haemodynamics. I think this time issue is by far the biggest hurdle, 30-50 mins is just too late to have an impact. In other words the patients who could have benefitted were likely characterised by poor CPR for 30-50 mins — think about it. Have we just defined a low probablity of survival cohort (barn, horse, bolted)?
Second, the study is underpowered. The observed difference in ROSC was 5% which could be clinically significant but we would need many more patients to detect a statistically significant effect. I’ve done some sums on this and I think you would need about 1520 patients in each group, so over 3000 patients which would be a challenge!
Third, there are implementation challenges. TOE requires specialised equipment, training, and expertise. Even within the trial, not all patients in the intervention group received TOE. In a cash strapped NHS, I don’t see anyone shelling out for a TOE in my ED anytime soon. To move it into the prehospital setting the implimentation challenges are even greater. It can (and has) been done by specialist doctor based prehospital teams, but we know that access to those in the UK and internationally is random and poor.
Fourth, the reliance on mechanical CPR may limit generalisability. While mechanical devices standardise compression depth and rate, they may be less adaptable to dynamic repositioning compared with manual CPR. I actually still like manual CPR. It’s rapidly adjustable and there are no trials demonstrating superiority of m-CPR. Some services that have the highest ROSC rates in the world don’t use mCPR, and I understand why. The newer devices that allow the point of CPR to be adjusted may change this, but that’s not proven as yet.
Fifth, there is a potential disconnect between physiological endpoints and clinical outcomes. The increase in ETCO₂ suggests improved perfusion, yet this did not translate into survival benefit. This is a recurring theme in resuscitation research and highlights the complexity of cardiac arrest pathophysiology. Improving one aspect of physiology may not be sufficient if other determinants of outcome, such as time to intervention and underlying cause, are not addressed.
Sixth, no patients survived with a good neurological score (CPC of 1 or 2). So what does this tell us about the outcomes for this cohort? If survival rates are so low in this cohort, what are we really aiming for? I think a lot of this is about patient selection and the fact that they are transported in arrest. I cannot remember the last person I saw who was transported in arrest to the ED who subsequently walked out of hospital with a good neurological score. I’m sure they may exist, but I don’t seem to see them.
Finally, the editorial rightly highlights the broader implications. TOE may offer additional benefits beyond guiding compression location, including identification of reversible causes such as tamponade or aortic dissection. These potential advantages were not the primary focus of this trial but may be important.
Should we change practice based on this study
In short, no.
This study does not provide evidence to support routine use of TOE-guided CPR in out-of-hospital cardiac arrest patients brought to the ED. However, this does support the idea that compression location matters and that physiological optimisation is possible. At the moment we are using intra-arrest arterial lines to guide our resuscitation, but maybe TOE could do something similar. But for both interventions, time is almost certainly a really important factor. Any optimisation a long way down the line is unliklely to lead to meaningful outcomes for our patients.
Summary
This cluster randomised trial examined whether ED based TOE-guided CPR could improve outcomes in patients with out-of-hospital cardiac arrest. While the intervention improved physiological markers such as ETCO₂, it did not lead to improvements in ROSC, survival, or neurological outcomes.
This is in keeping with many of our other thoughts about cardiac arrest. Interventions will work best when they are delivered soon after the start of the arrest. Transporting people in arrest to hospital often leads to delay, which may impact the effectiveness of that intervention.
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References
- Chu SE, Cheng CY, Chang CJ, et al. Transesophageal echocardiography during CPR in patients with out-of-hospital cardiac arrest: the EXECT-CPR randomized clinical trial. JAMA Intern Med. 2026.
- Brender TD, Wang TY, Inouye SK, Moore C. Can transesophageal echocardiography–guided CPR improve out-of-hospital cardiac arrest outcomes? JAMA Intern Med. 2026.
- Simon Carley, “Access to physician-based HEMS in the UK: progress, patchwork or postcode lottery?,” in St.Emlyn’s, March 22, 2026, https://www.stemlynsblog.org/access-to-physician-based-hems-in-the-uk-progress-patchwork-or-postcode-lottery/.
- Gareth Hardy, “ALS: Airway, Breathing, Capnography???,” in St.Emlyn’s, October 11, 2012, https://www.stemlynsblog.org/als-airway-breathing-c02/.
- Simon Carley, “Intra-Arrest Arterial Blood Pressure and Return of Spontaneous Circulation in Out-of-Hospital Cardiac Arrest.,” in St.Emlyn’s, November 22, 2024, https://www.stemlynsblog.org/intra-arrest-arterial-blood-pressure/.
- Simon Carley, “JC: Bystanders make the difference in cardiac arrest. St.Emlyn’s,” in St.Emlyn’s, May 5, 2017, https://www.stemlynsblog.org/jc-bystanders-make-the-difference-in-cardiac-arrest-st-emlyns/.
- Simon Carley, “ECPR for refractory cardiac arrest,” in St.Emlyn’s, January 30, 2023, https://www.stemlynsblog.org/ecpr-for-refractory-cardiac-arrest/.
- Iain Beardsell, “Podcast – Prehospital eCPR with Alice Hutin at Tactical Trauma 2024,” in St.Emlyn’s, November 6, 2024, https://www.stemlynsblog.org/podcast-prehospital-ecpr/.
