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Expert witness downplays effect of fentanyl in Floyd's slowed breathing during arrest

Expert witness downplays effect of fentanyl in Floyd's slowed breathing during arrest
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A respiratory expert downplayed the effect fentanyl had on George Floyd’s slowed breathing during his arrest after concluding in court that video evidence showed his respiratory rate before losing  consciousness was within a normal range.

During his testimony in the murder trial of former Minneapolis police officer Derek Chauvin on Thursday, pulmonologist Martin Tobin used his past clinical experience determining respiratory rates to calculate Floyd’s rate just before losing consciousness.

As the court played footage from the May 2020 arrest in which Floyd could be seen pinned front-down to the street, Tobin counted out the breaths Floyd took to determine his respiratory rate at the time.

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“At the lowest level, one of the simplest things to do that is especially informative is simply to count how many breaths somebody takes in. It’s one of the vital signs, like with blood pressure, pulse rate, temperature, is the respiratory rate,” Tobin said. “It’s one of the signs that tells us and it gives us a lot of clues as to what is happening inside the body.”

Tobin testified that he has often used individuals breathing to calculate their respiratory rate and has trained “nurses, respiratory therapists, medical students and doctors how to do it.”

Tobin walked the court through how he calculated Floyd’s respiratory rate in a roughly 17-second clip from his arrest presented by the prosecution.

After counting about seven to eight breaths from Floyd in the clip, Tobin said he was able to determine a rate of respiration of 22.

The rate, Tobin testified, is “extremely significant” to the case given the defense’s arguments focusing on the role fentanyl — one of the drugs found in Floyd’s system after his death — could have played in his death.

“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 percent reduction in the respiratory rate,” Tobin said.

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“So, with fentanyl, he respiratory rate should be down at around 10, instead of that, it’s right in the middle of normal at 22,” Tobin said.

“Basically, it tells you there that isn't fentanyl onboard that is affecting his respiratory centers. It's not having an effect on his respiratory centers,” he said.

“So, Mr. Floyd’s respiratory rate was normal at 22 just before he lost consciousness?” a prosecutor asked Tobin. 

“Correct,” Tobin confirmed.

His testimony comes as the prosecution and defense have clashed during the case over Floyd's cause of death. Tobin testified Thursday that Floyd died from a lack of oxygen during the arrest.

Throughout the trial, the prosecution has worked to highlight the role Chauvin's knee and the force he applied to Floyd's neck during the arrest last year played in his subsequent death. By contrast, Chauvin's legal team has focused on Floyd's drug use and underlying health issues.

During cross examination later on Thursday, Chauvin defense attorney Eric Nelson raised into question Tobin's calculations from his testimony with prosecution.

"Now in terms of the calculations that you've made. You would agree that your calculations are generally theoretical, correct?" Nelson asked Tobin.

"No, they're not theoretical. I mean they're based on direct measurements. They're based on extensive research," Tobin said.

Nelson then zeroed in on earlier calculations Tobin made during his testimony, when he also estimated that Chauvin at one point had half of his body weight on Floyd’s neck during his arrest last year.

While Tobin said he did not personally weigh Chauvin or his equipment to arrive at the estimate, the doctor said he "took the measurements that are reported."

During his hours-long testimony on Thursday, pool reporters said the jury appeared to pay close attention to Tobin throughout his remarks. Tobin said he has testified as an expert on dozens of cases, primarily those involving medical malpractice.

In a tweet on Thursday afternoon, Mary Moriarty, who previously served as chief public defender of Hennepin County, said Tobin was "very effective in teaching the jury about complicated concepts in plain English" and added that she is "not sure I've ever seen an expert this effective."