Apr 8, 2021
Pulmonologist Martin Tobin Testimony Derek Chauvin Trial Transcript: Floyd’s Respiratory Rates
Pulmonology expert Dr. Martin Tobin testified during Derek Chauvin’s trial for the murder of George Floyd on April 8, 2021. Tobin explained that fentanyl was “not having an effect” on George Floyd’s respiratory center. Read the transcript of his testimony remarks here.
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Dr. Martin Tobin: (00:00)
One two, three, four, five, six, seven, eight.
Speaker 2: (00:21)
So that was roughly a 17 second clip?
Dr. Martin Tobin: (00:24)
Speaker 2: (00:25)
And you counted seven, or eight breaths?
Dr. Martin Tobin: (00:28)
Between seven and eight. Yep.
Speaker 2: (00:30)
And did you use this to calculate a rate of respiration?
Dr. Martin Tobin: (00:33)
Yes, because it’s simple. Once you have 19 seconds and you count out the number of breaths you have here, and if, say, you count at seven breaths, that would come out at a respiratory rate of 22.
Speaker 2: (00:47)
Is that number, the respiratory rate of 22 significant to this case?
Dr. Martin Tobin: (00:52)
It’s extremely significant.
Speaker 2: (00:54)
Why is that?
Dr. Martin Tobin: (00:55)
Because one of the things in this case is the question of fentanyl and if fentanyl is having an effect and is causing depression of the respiratory centers, the centers that control breathing, that’s going to result in a decrease in the respiratory rate. And it’s shown that with fentanyl, you expect a 40% reduction in the respiratory rate. So with fentanyl, his respiratory rate should be down at around 10. Instead of that, it’s right in the middle of normal at 22.
Speaker 2: (01:30)
So you didn’t see a depressed rate of respiration, or breathing rate in Mr. Floyd?
Dr. Martin Tobin: (01:35)
No, it’s normal.
Speaker 2: (01:37)
And so what does it tell you bottom line with respect to fentanyl as it relates to Mr. Floyd.
Dr. Martin Tobin: (01:44)
Exactly. In terms of fentanyl, one of the major changes you see in fentanyl is a slowing of the respiratory rate. And again, we would be expecting a 40% reduction in the respiratory rate with fentanyl. The norm of the respiratory rate is 17 breaths per minute, plus or minus five. So that would mean a normal respiratory rate of between 12 and 22. That’s the normal range of respiratory rate. And so if it was with fentanyl, you’d be expecting a respiratory rate of 10. Instead of that, you counted here yourself and you can see when you counted yourself that the respiratory rate is 22. So basically, it tells you there isn’t fentanyl on board, that is affecting his respiratory centers. It’s not having an effect on his respiratory center.
Speaker 2: (02:43)
So Mr. Floyd’s respiratory rate was normal at 22, just before he lost consciousness?
Dr. Martin Tobin: (02:49)
Speaker 2: (02:54)
So the jury may have heard some other information in the case about the fentanyl, related to an elevated carbon dioxide level in Mr. Floyd’s body in the emergency room. Was that significant to you?
Dr. Martin Tobin: (03:08)
Yes, that’s very significant as well.
Speaker 2: (03:11)
Dr. Martin Tobin: (03:12)
Because he’s reported that carbon dioxide level in the arterial blood in the emergency room of 89. That’s a very high level of carbon dioxide. And so you have to take into account what are the factors that might have led to that? And there’s a particularly important factors in Mr. Floyd to explain why his carbon dioxide was found at 89 in the emergency room.
Speaker 2: (03:43)
So doctor, would you first tell us, what would normal have been for carbon dioxide levels?
Dr. Martin Tobin: (03:48)
The normal carbon dioxide level in you or me is 35 to 45 millimeters of mercury. That’s the norm. You don’t need the millimeters of mercury stuff, but they are the units that are given in the hospital chart.
Speaker 2: (04:04)
So, you said that there were significant factors in the case of Mr. Floyd. Would you help the jury understand what those were?
Dr. Martin Tobin: (04:11)
Yes. The important factors are that we know that he made his own last spontaneous effort to breathe at 20:25:16. After that, you can look at the videos and you see, he makes no breath. The last breath he took was that 20:25:16. Then we know after that, he stayed on the street for another three minutes or so. Then he’s placed into the ambulance and we know that in the ambulance, they attempted to put in an airway and i-gel. And you can see that on Officer Lane’s body cam, you can see all of that happening. And then you can see the time at which they actually successfully inserted the airway, and when they gave him the first breath. And that is a gap of nine minutes and 50 seconds from when he last took a breath.
Speaker 2: (05:12)
And why is that significant?
Dr. Martin Tobin: (05:14)
That’s very significant, because we can calculate what is the rate of increase in the carbon dioxide in somebody who doesn’t breathe. If somebody doesn’t take a breath, carbon dioxide increases at a predictable rate. And that rate is up to 4.9 millimeters of mercury per minute that it increases. And so he has not taken a breath for nine minutes and 50 seconds, so you would expect just on that basis, that he’s carbon dioxide level will go up by 49. So you add 49 to the normal values of 35 to 45. And then you add that and you’re going to get a value of between 89 and above. And so it comes out virtually identical to the value that they’ve found in the emergency room of 89.
Speaker 2: (06:19)
So doctor, what’s the punchline with respect to that, what does it tell us?
Dr. Martin Tobin: (06:22)
The significance of all of that is it’s a second reason why you know fentanyl is not causing the depression of his respiration. What you’re seeing is that the increase in his carbon dioxide that is found in the emergency room is solely explained by what you expect to happen in somebody who doesn’t have any ventilation given to them for nine minutes and 50 seconds. It’s completely explained by that.
Speaker 2: (06:54)
So when the person then is not breathing, then carbon dioxide would naturally continue to build up in the body?
Dr. Martin Tobin: (07:00)
Speaker 2: (07:01)
And that’s what matches what was seen in the OR for Mr. Floyd?
Dr. Martin Tobin: (07:05)
Speaker 2: (07:14)
Now, you said that there were other things that were significant, that were related to the rate of respiration, and we talked about fentanyl.
Dr. Martin Tobin: (07:22)
Speaker 2: (07:22)
Was there anything else?
Dr. Martin Tobin: (07:23)
Yes. There’s two other things that are very important to the respiratory rate, because you saw it with your own eyes, exactly, his respiratory rate. And the first thing is that if you have somebody who has underlying heart disease and the heart disease is so severe that it’s been said that it’s causing shortness of breath, that it’s causing you difficulty with breathing, if somebody has heart disease that’s causing shortness of breath, virtually all of those patients are going to have very high respiratory rates. They’re going to have respiratory rates of 35, 30, over 30, even over 40 when you have heart disease that can give you a shortness of breath. Instead of that, we find that his respiratory rate is normal at 22.
Dr. Martin Tobin: (08:14)
The second thing that’s important about the respiratory rate of 22, is if you have somebody where the primary problem in the body is airway narrowing, where you have somebody where there is that the airways are being compressed, there’s narrowing in the neck, or there’s narrowing like in somebody in the chest. But the response, the physiological response to airway narrowing is a normal respiratory rate, and that is what he has. So it’s the expect. But the respiratory rate that you see that’s normal is the expected physiological response in somebody who has airway narrowing.