Monday 19 November 2018

Manual vs. Mechanical CPR; which is better?

Image result for lucas device

There are theoretic advantages to a mechanical chest compression device (i.e. Lucas device). They demonstrate improved blood pressure and coronary perfusion pressure compared to regular CPR. In addition, the earlier observational studies looked promising.

However, there is a theoretical downside. Paradoxically, CPR may be interrupted more when fumbling to fit the device. Or even worse, they may increase time to defibrillation.

So, which is better?

This meta-analysis gathered the available data from out-of-hospital cardiac. Survival to hospital admission was the primary outcome of interest. They also looked at any ROSC, survival to hospital discharge and favourable neurologic outcome at discharge.

The authors found 20 studies of which 5 were RCT’s. In total, there were 21,363 patients included with just over half from the trials. The observational studies and the clinical trials were pooled and analysed separately.

For survival to admission, the RCT’s showed no advantage to the mechanical devices. Whereas the lower quality observational data demonstrated a benefit in favour of mechanical CPR.

How could this be?


In observational studies, patients are not randomised to a treatment allocation. As such, one group is usually “sicker” than the other. Perhaps the machine was utilised more when the paramedics thought the patient had a greater chance of survival (i.e. younger, witnessed arrest, bystander CPR, shockable rhythm)?

Researchers try to correct for this by doing some fancy statistics; propensity scores, stratified analysis, multivariate adjustment, logistic regression, etc. But these techniques are far from perfect. Furthermore, there are always the unknown and unmeasured confounders.

This may be irrelevant anyway.  The most important outcome, “favourable neurologic outcome at discharge” was no different in both the RCT’s and observational meta-analysis.

What’s the take home?

In all comers, it looks like there is no advantage to a mechanical compression device.

But there remains some “what if” questions.

What if we educated staff in how to fit the device very quickly while ensuring rapid defibrillation? What if it’s an overdose patient that needs prolonged good quality CPR? What if it's a bridge to the cath lab? What if the technology improves? What if we use the device as a cocktail shaker?

That’s a lot of what if’s…


Bonnes JL, Brouwer MA, Navarese EP, et al. Manual Cardiopulmonary Resuscitation Versus CPR Including a Mechanical Chest Compression Device in Out-of-Hospital Cardiac Arrest: A Comprehensive Meta-analysis From Randomized and Observational Studies. Ann Emerg Med. 2016;67:349-360. [Link]

Sunday 18 November 2018

Battlefield acupuncture to treat low back pain in the ED; witchcraft in action

Acupuncture has been around for thousands of years… so it must be good.

We all dread treating the patient with low back pain. We don’t have a magic bullet that will provide a fix. It’s frustrating for the patient and provider.

As such, maybe we should engage in witchcraft! Perhaps something that “has been around for thousands of years.”

This was a “feasibility study” enrolling 30 patients with low back pain in New York City. They were randomised to either standard care alone vs. standard care plus “battlefield acupuncture.” Evidently, this is ear acupuncture that has been used by the US military… so, it must be good.

Primary outcome was the 10 point numerical rating scale (NRS) and the “get-up-and-go” test (GUGT). The GUGT is how much time it takes a patient to get out of a chair, walk three meters, turn around and sit back down again.


Abracadabra! The post-intervention NRS in the acupuncture group was better at 5.2 vs. 6.9 (p=0.04). The GUGT showed no difference.

But wait a minute…

This study was listed at This is where original study protocols are published. All too often researchers change the goal posts mid-study or suppress negative results. (My all-time favourite example was gabapentin for off-label use.)

A search of registration number NCT02399969 shows the GUGT as the sole primary outcome. The NRS was a secondary outcome. Research misconduct anyone? One would hope the peer review process would pick up on this… it’s not hard! At the very least, the manuscript should mention why they changed their primary outcome to give them favourable results.

But there’s even more than an allegation of research misconduct.
  • Acupuncture was not blinded. Not even a sham acupuncture arm. This introduces bias that favoured acupuncture.
  • Placebo works; in particular for pain and nausea. Acupuncture is theatrical placebo at it’s best. All the results in the NRS can easily be explained by placebo effect. The GUGT is a more objective measure and the trend favoured standard care alone.
  • A quarter of patients approached for enrolment declined to participate. Did they screen out the patients who were acupuncture non-believers?
  • There’s more… but for brevity, I’ll stop now…

What are we to conclude?

Please stop the nonsense.

Acupuncture has been around for a long time. Currently we have no consistent good quality evidence to demonstrate efficacy beyond placebo effect.

No more study is needed.  


Fox LF, Murakami M, Danesh H, et al. Battlefield acupuncture to treat low back pain in the emergency department. Am J Emerg Med. 2018;36:1045-1048. [link]
Image result for witchcraft

Wednesday 14 November 2018

Supraglottic airway vs. endotracheal tube for out-of-hospital cardiac arrest; which is better?

This study was a large cluster-crossover clinical trial in the USA attempting to answer this research question. 27 EMS agencies were randomized in clusters to either a laryngeal tube or endotracheal tube with crossover to the alternate strategy at 3 to 5 month intervals.

Why randomize EMS agencies? Wouldn’t it be better to randomise individual patients?

Think feasibility.

Research in cardiac arrest is challenging.  The last thing paramedics want to do during a code is open a study envelope. They’ve got other things on their minds. Hence randomise EMS agencies. Of course this can introduce bias and statistical inefficiency. But such is compromise in research.

The primary outcome was 72-hour survival. They did report the much more important outcome of favourable neurologic status (mRS<3) at discharge from hospital.


3000 patients were enrolled. About half were unwitnessed and/or had no bystander CPR. 80% had non-shockable rhythms. It’s no surprise overall outcomes were terrible. It is also challenging to demonstrate a difference in treatment strategies when the vast majority were going to die regardless of intervention. But such is life… and death.

Rates of initial airway success were 90% with the laryngeal tube but a pretty dismal 50% with the endotracheal tube. Yikes!

72-hour survival was 18% with the laryngeal tube and 15% with the endotracheal tube. Rates of favourable neurologic outcome was 7% vs. 5% favouring the laryngeal tube.

What are we to think?

Unfortunately, this study did have some problems. It had poor rates of first pass success with intubation. The pragmatic study design and cluster randomisation introduced noise. They only studied one type of supraglottic airway… i.e. not the LMA.

But in the end, there probably is no compelling reason to push for endotracheal intubation in the field. This may distract from other meaningful interventions such as good quality CPR and rapid defibrillation.

It’s unclear how much of this is externally valid to a well-resourced Emergency Department. A dedicated airway doctor and lots of hands might change our outlook.  Nevertheless, this study does push our focus away from the endotracheal tube in cardiac arrest.

Image result for laryngeal tube airway 

Wang, HE, Schmicker RH, Daya MR, et al. Effect of a Strategy of Initial Laryngeal Tube Insertion vs. Endotracheal Intubation on 72-Hour Survival in Adults with Out-of-Hospital Cardiac Arrest. JAMA 2018;320(8):769-778. [link to abstract]