Effect of feedback device on CPR: too good to be true?

Rules of Running a Good Code:
1 – compressions
2 – compressions
3 – compressions
Accordingly, we have been seeing  a lot of new devices and techniques which promise to improve CPR quality.
 Vahedian-Azimi et al. (Critical Care201620:147) [1] published a small RTC looking at the use of a feedback device (CardioFirst Angel) on CPR quality and survival. 

2
ROSC was observed more frequently in the intervention group (72 % vs. 35 %; p = 0.001). Additionally, A significant decrease in rib fractures was identified between groups (57 % vs. 85 %; p = 0.02).
The authors conclude:
“Use of the Cardio First Angel™ CPR feedback device improved adherence to published CPR guidelines and CPR quality, and it was associated with increased rates of ROSC. “

Survival Benefit?

It seems clear that there is a significant increase in ROSC (72% vs. 35%). Does that increase in ROSC translate to increased survival?
Per the abstract:
“We investigated whether a CPR feedback device would improve CPR quality and consistency, as well as patient survival.”
The only outcome reported related to survival is ROSC, which often does not relate to increased survival to hospital discharge (looking at you epinephrine). Although the increased ROSC is promising, it would be great to see survival to discharge reported in a future study.
The study was submitted for publication September 2015 but was not registered with clinicaltrials.gov until March, ~6 months after it was submitted for publication. Due to the late registration with clinical trials.gov there is no way to tell if they initially intended to look at survival.
Although the study reports an improvement in a CPR quality score in the control arm, they do not report total %time of the code where CPR was preformed. AHA recommends at least 60% and a goal of 80% compression time during a code. This can be an important confounding factor which is not listed.

Intention To Treat Analysis?

Patients were randomized in the emergency department at the time of ICU admission.  Out of 229 patients randomized only 80 where included in the final analysis. 65 of those excluded were excluded due to no cardiac arrest. Which means 165/229 (~72%)patients admitted to the ICU during the study period had a cardiac arrest!
Only 35% of randomized patients where included. 48% of the patients who had cardiac arrest where included. However, there is no mention how the study dealt with the patients not included. It appears clear there was no intention to treat analysis (ITT), was it per protocol? as treated? Hard to say. To be honest, although ITT is typically the gold standard in RCTs I am not sure it would be applicable in this case since patients were randomized prior to any cardiac arrest. There is no way to include the 64 patients who did not have a cardiac arrest into the analysis of ROSC. Can you return what was never lost?
But what about the 52% of patients (n=84) who had a cardiac arrest and were not included in analysis? was a modified ITT used?

Control Arm ROSC %

Perhaps, the most glaring part of this study is the low 35% ROSC rate of the control arm. This low rate is despite the patients not only being in hospital during arrest, but are in an ICU.
The 2015 AHA statistics update [2] ROSC rates where reported as 55.8% for black patients and 67.4% for white patients. Both numbers significantly higher than the 35% in this study. 67.4% in white patients would not appear to be significantly different to the 72% reported in the intervention arm in this study. Survival at discharge was 37.4% for white patients, which is better than the ROSC achieved in this study. (25.5% survival for black patients).

Does it make sense?

An important question to ask when interpreting a study is does the hypothesis make sense.
At first glance it certainly does; higher quality CPR = increased ROSC.
However, in contrast to mechanical CPR I am not so sure.
Mechanical would apparently achieve all the goals of a feedback device; appropriate compression depth, full recoil and appropriate rate.
However, time and again studies have not shown survival benefit with mechanical CPR [3] and have minimal if any effect on increasing ROSC. [4]
In a 72 pt cohort with in hospital cardiac (28 in ICU, CCU or ED, 44 on floors) 63.8 % had ROSC [5]. This % is similar to current AHA statistics for inhospitable ROSC, and not as high as the 72% achieved by  Vahedian-Azimi et al. with a feedback device.

Conclusion

The reported increase in ROSC is promising and high quality CPR should improve outcomes, however, I don’t think this paper proves that feedback devices are truly beneficial. The most important outcome, survival to discharge, is missing. The high rate of cardiac arrest in this patient population and the low rate of ROSC in the control arm make me question the external validity of this trial. It appears clear that the use of this new device did not interfere with CPR quality and did not prove to be burdensome during a cardiac arrest. Anyone who has felt a rib (or two) crack under their hands can appreciate the significance  of a decrease in fractures. Although the study is promising, I would love to see it replicated with increased survival as the primary end point.
With all that being said, I would like to end with this Tweet:

 

Please contact me @foamflea with any comments

Sources:

[1] http://ccforum.biomedcentral.com/articles/10.1186/s13054-016-1296-3

[2] http://circ.ahajournals.org/content/early/2014/12/18/CIR.0000000000000152

Heart Disease and Stroke Statistics—2015 Update

A Report From the American Heart Association

(Circulation. 2015;131:00-00.)

[3] https://volunteer.heart.org/apps/pico/Pages/PublicComment.aspx?q=782

[4] http://www.lucas-cpr.com/doc_en/Verstraete%20Does%20the%20use%20of%20LUCAS%202008%20p-ERC.pdf

Unpublished poster presentation:  Verstraeten S, De Knock J, Müller N, Martens P, Van den Brande F, Vandevelde K. “Does the use of LUCAS influence survival for in-hospital cardiac arrest patients?”. ERC congress 2008; Poster 240 (on file at Jolife).

ROSC was achieved in 55% in the LUCAS group, a slightly better result compared to the conventional CPR-group (44%). However no difference was demonstrated between both groups regarding discharge rate.

 

[5] http://www.lucas-cpr.com/doc_en/Durnez%20ROSC%20and%20neurological%202008%20p-ERC%20.pdf

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