Articles:
- Latency of Pulse Oximetry Signal with use of Digitial Probes Associated with Inappropriate Extubation (J Emerg Med 2012;42(4):424)
- Latency and loss of pulse oximetry signal with the use of digital probes during prehospital rapid-sequence intubation. (Prehosp Emerg Care. 2011 Jan-Mar;15(1):18-22.)
- Rate of decline in oxygen saturation at various pulse oximetry values with prehospital rapid sequence intubation. (Prehosp Emerg Care. 2008 Jan-Mar;12(1):46-51.)
Dan Davis at his best:
Did you like this episode? Then tweet the hell out of it…
ON EMCrit Podcast 88, I discuss Oxygen Physiology and Pulse Ox Lag with Dan Davis http://t.co/NBOLzbrl
— the EMCrit Crew (@emcrit) December 11, 2012
Additional New Information
More on EMCrit
- PulmCrit – Dismantling the systemic racism of pulse oximetry(Opens in a new browser tab)
- PulmCrit- Top 10 reasons pulse oximetry beats ABG for assessing oxygenation(Opens in a new browser tab)
- EMCrit 267 – They are not All Right!! An interview on Hemodynamic Assessment with Mike Patterson(Opens in a new browser tab)
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Editor-in-Chief, at EMCrit.org
An ED Intensivist from NY.
Professor
Nassau University Medical Center
No conflicts of interest (coi).
Professor
Nassau University Medical Center
No conflicts of interest (coi).
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Finally! This needs to be widely publicized. Dan showed me the video a few years ago when we had him up for a Journal Club on post intubation managment. BE AFRAID of pulse ox. UNDERSTAND what it tells you. UNDERSTAND what the number mean and WHEN it meant that!
How many people have we harmed by not understanding this.
ARRRRRGH
Mike Jasumback
It was news to me when I first read about it in the pulse oximetry literature.
Another excellent podcast Scott. Very useful information from Dr. Dan that has a lot of value in the pre-hospital setting where I work. Although I enjoy listening to all your podcasts, how can you ever get too much airway info??
Jeff
preaching to the choir, brother.
Great stuff, gentlemen. The pulse oximeter is the world’s first actual time machine. It transports you 30-90 seconds into the past. When you bail on an attempt at 90%, don’t be surprised as you’re bagging effectively to see a nadir of 75% before it bounces back. So bail earlier.
love it described as a time machine!
thanks to you and Davis for this podcast! dont worry about Thumper..not everyone has to deal with Irukandji syndrome..but everyone has to deal with airway and ventilation in resuscitation! whilst not being perfect solutions to this issue, I did ponder that NODESAT a la Levitan, DSI a la you, and airway ultrasound a la Mike & Matt…might address some of the challenges cited in pulse ox latency and emergency airway mgt. for prehospital folks, NODESAT is very achievable with planning, and may minimise this very issue.whilst the debate may rage over whether to teach VL vs DL vs both to… Read more »
Just taking your comments from a slightly different perspective. Most EMS providers can aim their vitals monitor at the eyes of intubator, this is usually not possible in the ED–a problem. Wouldn’t it be great if we could get the pulse ox number and ETCO2 waveform to appear on the video laryngoscope screen.
actually thats very perceptive point
most ED resus bay monitors Are positioned behind the intubator normally! all the wall suction and gas pipes are also behind.
this is why I usually assign a dedicated staff member to monitor pulse ox and call it out regularly during RSI.
because you can lose your situational awareness when the environment is designed for you to lose it!
Du Canto had an idea to use HUD type goggles to display the monitor and VL feed simultaneously.
interesting, but suspect only he could make it work for him!
A ‘slave’ monitor screen that is visible for the intubator can be installed quite cheaply…
ah yes, monitors are cheap but where to place them is hard. can you send us a photo of your set-up. after making my comment yesterday, I plan to mount a stand-alone pulse-ox on our VL cart.
actually you gave me an idea spawned from aviation and an anaesthetic colleague in aviation there are terrain avoidance warning systems, typically, with an audible alarm announcing the height from ground and eventually an alarm voice instructing emergency flight maneuvers, like “pull up, pull up” what if the pulse ox had an option of the audible beep alarm, that you could set it to announce the pulse ox reading every 5 seconds or so..it would still go beep beep with the pulse but a soothing voice would announce the reading regularly, then at a critical level, it might announce “pull… Read more »
We at least have an additional slave monitor mounted in front of the intubator in our resus cubicle. Something to consider when designing a
new ED.
Great stuff — I especially liked the point made in the “squeezer” portion, because many people don’t understand the importance of releasing the bag (although the UPitt CCM guys have managed to use this phenomenon to create a kind of BVM “PEEP” effect — see first minute of http://www.ccmpitt.com/education/airway_course/videos/video2_2012.html). A few other random thoughts: 1. Some of us have been using pulse ox (standard clip type) on ears forever. Awkward but it works and I did always imagine it’s somewhat more central than the finger. Thoughts? 2. Many students seem puzzled by the fact that we “resat” faster than we… Read more »
Brandon,
Somehow I missed these amazing comments. Bags with these duckbill valves are dangerous and horribly wrought. Problem with using them for CPAP is that unless you have the pressure gauge, no idea what CPAP the patient is getting and if the bagger likes to hold a little pressure between breaths, the patient can never exhale.
Yep, it’s definitely a somewhat ghetto technique for creating PEEP, and I think quite skill-intensive — especially because it really requires a slow squeeze, fast release (to avoid impeding exhalation), then quick pop at the very end of expiry to “catch” the pressure. But you gotta be watching like a hawk to get the rhythm and know where the end is; too soon and they don’t exhale fully (and if you then bag in the same volume, you start stacking breaths), too late and you reach 0 pressure. More of a way to teach mastery with the device, I expect.… Read more »
Minh,
Most monitors allow a pulse-ox tone and if you choose tone modulation will vary the sound based on pulse ox decline. This is standard in ORs.
I dont find the pulse ox tone decline to be sufficient a stimulus for most operators.
thats why aviation systems employ a computer generated voice and have actual numerical call outs of approach altitude . its still not perfect but I find myself emulating this in RSI situations by assigning a role of the pulse ox steward.
Tell everyone in the resus room to shut up when you are intubating. Actually you could apply that to most codes. I am told that the trauma director at The Alfred speaks softer and softer, the more critical circumstances get. Maybe its a prompt that there needs to more concentration and less noise.
Intubation is definitely a sterile cockpit procedure.
Davis’s discussion of tidal volume & minute ventilation video seems to put hemodynamics at odds with lung protection. Should we be using 750mL Vt or 6-8mL/kg PBW?
I think 500-550 ml is ideal. I think for the duration of the code, don’t need to worry as much re: lung protection.
Another very interesting topic, kudos for the fantastic work Scott, cheers from the Netherlands!
I like the idea of the voice announcer for the pulse oximeter. It definitely goes some way to helping one regain situational awareness. Just thinking out loud, but id imagine there is not a standard port for all pulse oximeter probes. Could an iPhone app be used to watch the display using the camera, and then announce values at critical points…? Would this be useful in the ED/prehospital setting or would this just be an expensive toy which gets lost in the detritus of a resus?
Any thoughts on the utility/accuracy of pharyngeal oximetry in this setting?
http://www.ncbi.nlm.nih.gov/pubmed/17567352
The proposed use of an OPA is not terribly useful while intubating, but perhaps there is another Macgyver way of utilising the pharynx as a monitoring site?
have tried this on myself and seems to work well for intubated patients. Forehead or tragus seems more realistic for patients you are going to intubate.
Great podcast! The first time I stumbled on this I was an R1 playing with on oximeter while waiting for my admission to come up, and trying to hold my breath and desaturate myself. I learned I had to exhale to as close to residual volume as I could and then gut it out, but even then, as I gasped for air, my sat would sit at about 97-98%. But wait a few more seconds, and watch it drop down – the “best” I managed was the mid 70’s – then come back up fairly quickly over 5-10 sec. Keep… Read more »
great stuff! also tubs of fun to see how high you can get your ETCO2
Hello,
I think that having a goal EtCO2 and SPO2 is a great idea in most patients. However, it was my understanding that EtCO2 in patients with diffusion disorders (i.e. ARDS) or with increased dead spaces was problematic?
I see many ICU patient’s whose ETCO2 is lower than their PaCO2.
Thank you,
David Hersey
We have discussed this elsewhere on the blog/podcast, but absolutely ETCO2 can not be used as a surrogate for blood CO2. The only thing you can say definitively is that PaCO2 is at least as high as ETCO2.
Hello,
So, in most clinical situations it isn’t possible to have a PaCO2 higher than the ETCO2. Good to know.
I always assumed that the ETCO2 reading could mask hypercapnia.
Thank you,
David
You lost me. PaCO2 is at least as high as ETCO2. Low. ETCO2 can mask sig. hypercapnia
Hello,
PaCO2 is at least as high as ETCO2.
Dose this rule work in all clinical situations?
For example, a patient with ARDS with a PaCO2 of 70. ARDS causes impairment of diffusion of C02 across the alveolar walls.
Therefore, the ETCO2 could be lower than the PaCO2 because it is unable to diffuse across alveolar wall?
Or, I could be out in left field here.
Thank you,
David
PaCO2 – ETCO2 gradient:
Read:
http://www.capnography.com/new/index.php?option=com_content&view=article&id=78&Itemid=1029
http://www.capnography.com/new/index.php?option=com_content&view=article&id=79&Itemid=1030
David, Not sure where we are disconnecting. I think you are looking at the phrase in reverse. Maybe this would be helpful. P-40E-38=normal; P-40E-20=happens all the time in sick patients like the ARDS patient or patient with poor CO; P-100E-22=see this in COPD folks; P-20,E40=this is what you will not see. PaCO2 will be at least as high as ETCO2. Now some annoying sticklers will write in that they once saw a PaCO2 that was slightly lower than a simultaneous ETCO2 and while this is physiologically possible, esp in severe asthma. The difference is so small in these cases that… Read more »
Hey all, Just wondering if anyone is aware of any literature regarding safe oxygenation practices in the light of Dr. Davis’ discussion for those of us at high altitudes (7-10k feet or ~2130-3050 meters). Up here we consider an Sp02 of 95% fairly routine and normal. However, we also see patients with Hemoglobins of 17 and Hct of >50% and don’t blink. Any guesses on whether the relative polycythemia is going to give us some extra time or are we stuck having to be extremely expedient in our attempts at intubation. The 93% number is especially troublesome for my colleagues… Read more »
wow, such a great question. unfortunately I have no idea. anyone, anyone…
Clint, The net improvement in total oxygen stores is only modest because the larger improvement in blood content is proportionately small compared to the effect of de-nitrogenation which contributes to >90% of the change i.e. it’s not going to buy you significantly more time. The more interesting question is whether mountain dwellers can tolerate greater degrees of hypoxia for longer periods of time without detriment. Factors such as ^2,3-DPG and better oxygen extraction may be factors to consider. From first principles in your example (Sao2 95%, paO2 80mmHg, Hb 17 g/DL Oxygen stores (room air – polycythaemic mountain dweller) FRC:… Read more »
Makes perfect sense. I wonder if there’s any real difference here between type I and II reap failure up here. There’s some anecdotal stories of guys just consciously “breathing faster” to compensate for the fact that their body hasn’t accumulated enough CO2 to trigger their resp drive to keep up with oxygenation on climbs. Thanks for the resp phys numbers walk through!
I am not sure what you are trying to say. At high altitude (and low FiO2), arterial hyperaemia becomes the dominant stimulus for alveolar ventilation. This results in a permanent reduction in paCO2 (compared to sea-level values) For those with lung disease, they will have a widened alveolar-arterial oxygen gradient. They will experience a greater reduction in paO2 for a given FiO2 when exposed to altitude. This may result in a greater ventilatory response to hypoxaemia and consequently they appear ‘to breathe faster’ compared to normal individuals. However, this is only an attempt at compensating for their poor oxygenation in… Read more »
The concept of ‘lag’ versus ‘lead’ monitors was emphasised to me by an anaesthesia professor I worked under. Both in the Australian Anaesthesia and ICU examination, equipment is a specific exam subject. One could argue that it should be the same for Emergency Physicians (particularly those who do a lot of resus/pre-hospital work). There is also some good stuff published by Prof Bill Runciman in the AIMS ( Australian incident monitoring system) study which looked at intra-operative incidents. The authors tried to find certain patterns and derive logical algorithms and mnemonics to deal with different scenarios e.g. acute desaturation or… Read more »
love it. have to give it the time it deserves to digest the whole site.
The gist of it is there are four separate procedures depending on the urgency level – ‘SCARE’ Scan = routine, regular systematic monitoring of all parameter, equipment and situation (the ‘idle’ situation) Check = provokes more active responses to new events Alert/Ready = when there is a major change in the situation Emergency = when the patient is peri-arrest/arrest The Scan procedure includes COVER ABCDA A mnemonic and a swift check. Within the ABCD mnemonic are further sub-procedures. The author reinforces the idea of regular: 1) situational awareness and constant vigilance (before problems occur) 2) defined actions in response to… Read more »
Thanks for getting all the airway obsessives on my back Weingart!
C
Lovin’ the comments on this post, particularly love the “pulse oximeter as a time machine” comment!
Hate to be the comment thread resuscitationist here, but here goes-
Re: comments about a HUD or monitor visible from the HOB- this would be a great implementation of Google Glass, maybe a HUD that includes selected monitor parameters w/ a timer (also good for timing RSI meds)?
Something tells me there’s some money to be made here…..
I’m a student currently in clinical rotations and was in the ED at a level II trauma center yesterday. The senior attending intubated a patient who had come in with a SpO2 of 52% and what appeared to be a R pneumo. While tube placement was verified via breath sounds and -epigastric sounds (by the attending and an RT), SpO2 continued to plummet for about a minute. Everyone in the room started to pucker and I could hear the wisdom from this podcast in the back of my head. This looked like completely normal lag caused by a 30 second… Read more »