Cobras and the First Look

Dr Alan Garner has been here before, asking whether we’re asking the wrong questions when we try to measure quality advanced airway care. Here’s a fresh bit of research that adds to the discussion.

Unintended consequences would hardly be a new thing in medicine or in any other endeavour.  Here is one of my favourite examples taken from Wikipedia (look we all go there from time to time):

“The British government, concerned about the number of venomous cobra snakes in Delhi, offered a bounty for every dead cobra. This was a successful strategy as large numbers of snakes were killed for the reward, but eventually enterprising people began to breed cobras for the income. When the government became aware of this, they scrapped the reward program, causing the cobra breeders to set the now-worthless snakes free. As a result, the wild cobra population further increased. The apparent solution for the problem made the situation even worse, becoming known as the Cobra effect.”

Check this link for some more cracking examples.

Avid or maybe even occasional readers who chanced to come back at exactly the right moment might recognise that I have previously expressed my doubts about reporting the first look intubation rate as a quality measure for intubation.  Have a look here for the previous post.

Now where might you go to find a basket of cobras these days? Well I have just spotted a new paper published in Prehospital Emergency Care which fits the bill.  You can find the full text here. I guess we’d better start picking up the snakes.

It’s probably a friendly one, right?

Let’s Start with the Headlines

This paper is a look at a ground paramedic system in a small US city (Spokane in Washington State) where the paramedics have used muscle relaxants for more than 20 years i.e. you would have to consider this a mature system.  It appears to be a well supervised system and paramedics have a minimum number of intubations they must successfully perform each three-year certification cycle in addition to a well-structured training regime.

Superficially the system appears to be working well.  They had a 95% success rate and 82% first look success.  Although 95% overall success rate is below par compared with other systems world-wide, all patients not successfully intubated were successfully managed with a supra-glottic device.  That should be OK, right? That probably means the primary focus is on managing the airway to achieve the goal that really counts – oxygenation. And that first look rate of 82% seems quite respectable compared with reports from other systems.  So not a star system but safe enough if these were the only quality measures you were looking at.

Let’s Get Our Hands Right Amongst the Snakes

The thing is the paper also reports physiological data captured by the patient monitor during the peri-intubation period and this tells a very different story.  Much of the data is not that surprising.  Desaturations were more common when patients were being intubated for respiratory pathology and were also related to the highest SpO2 achieved at the end of pre-oxygenation.

How about we look at some oximetry data highlights?

  • Oximetry data was available in 110 cases. Peri-intubation desaturation occurred in 47 cases (43%) and in 32 (68% of the desaturations) it was severe (<80%).
  • The median nadir was 71% and median duration was 2 minutes. Among cases with any desaturation, the time in the unhappy valley was at least 2 minutes in 46% of cases with first-attempt success and in 100% of cases requiring multiple attempts.
  • Although the frequency of desaturation was significantly higher in cases requiring multiple laryngoscopic attempts versus a single attempt (70% vs. 37%; p = 0.01), 70% of all desaturations occurred on first attempt intubation success. Only 11% of desaturations were reflected in the EMS patient care report.

Heart rate changes

  • 13% became bradycardic, 7% profoundly. The median SpO2 nadir during bradycardic episodes was 30% with median duration of nearly 5.5 mins.
  • Sixty percent of bradycardia events occurred on first-attempt intubation success.

Yes in the multiple attempt cases the desaturations were worse than cases requiring a single attempt.  But given the very high rate of desaturation events in this study is reporting the first pass success rate providing any meaningful quality data?  Is there subtle pressure placed on the paramedics in this system to achieve first pass intubation at the potential expense of desaturation events, by the very fact that first pass rate is being reported?

We can’t be sure and I’ll put my hand up and say “yes, I’m inferring a little bit from what we can see in the paper”.  But clearly the overall success and first pass success rates provide no real indication of process safety in this particular EMS system.  It is only in reporting of clinically meaningful quality data like desaturation that we see the real safety performance.

Who Else Thinks This?

To quote the paper itself “What may be obscured by this focus on the risks associated with multiple intubation attempts is the large absolute number of physiologic derangements occurring on first-attempt success. In our study, 70% of all desaturations, 60% of bradycardia episodes, 63% of hypotension episodes, and one of the two cardiac arrests occurred on first-attempt success.”  That’s really the nub of it and it’s excellent work by the authors to make sure that’s right up there in the discussion.

The authors conclude that first attempt success “is not a reliable indicator of patient safety.”  The authors specifically note that prolonged duration of first pass attempts is a contributor to the desaturation rate and that prolonged attempts might be “a consequence of lack of awareness of the passage of time during an intubation attempt, or lack of awareness of the occurrence of desaturation”.

But is the very fact of reporting first pass success rate a subtle psychological contributor too?  The authors clearly agree with me here when they comment “prolonged desaturations on first attempt success could be an unintended consequence of the focus on first-attempt success itself and the common use of first-attempt success as a primary measure of intubation quality.”

Maybe it’s an example of the Cobra effect.

The Take Home Bit

Prospectively it is right to set yourself up to get the ETT in the right place on the first attempt and with minimal complications.  However once the intubation attempt commences the emphasis needs to shift to prevention of complications by reacting to physiological changes as they occur.

We want to encourage this.  I want my teams obsessed with preventing complications, not first pass success.  Why are we reporting a process measure as a quality indicator when it might well be having the perverse effect of encouraging those very complications we were trying to remove?  The system I work in here in NSW requires us to report first pass success.  I remain hesitant to do this as I don’t want to signal to my teams that this is actually something that matters.  I would much rather them be proud of the 0% desaturation rate that we have for intubation over the last 9 months – that is really impressive.



That paper is this one:

Walker RG, White LJ, Whitmore GN, et al. Evaluation of Physiologic Alterations during Prehospital Paramedic-Performed Rapid Sequence Intubation. Prehosp Emerg Care. 2018;

And the link to that first post covering similar ground is right about here.

The image of the cobra came via Creative Commons off flickr and is unchanged from the post by Luca Boldrini.





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