Seattle Study Hints at Low COVID-19 Risk From Bystander CPR

Patrice Wendling

June 10, 2020

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A new analysis shows that COVID-19 cases accounted for less than 10% of out-of-hospital cardiac arrests (OHCAs) treated in the Seattle area when the outbreak was active.

Concerns were raised by several groups early in the pandemic that cardiopulmonary resuscitation (CPR) could generate aerosols and thus increase the risk for coronavirus transmission.

"Our fear is that we are unintentionally having people die because of our concerns about COVID," Michael R. Sayre, MD, professor of emergency medicine, University of Washington, Seattle, said in an interview. "We just want to raise awareness that some of the unintended consequences of well-meaning policies can be to increase deaths in other groups."

Sayre, who also serves as medical director of the Seattle Fire Department, and colleagues analyzed their OHCA registry, emergency medical services (EMS), and death certificates to estimate the frequency of COVID-19 among the OHCA population served in Seattle and surrounding King County.

From January 1 through April 15, EMS responded to 1067 OHCAs, of which 478 were treated by EMS. As of April 15, the community had 15 deaths per 100,000 population from COVID-19 — higher than 42 other states at that time, according to the research letter, published June 4 in Circulation.

During the active period from February 26 — the day the first American COVID-19 deaths were reported in Washington state — to April 15, EMS responded to 537 OHCAs, of which 230 were treated by EMS.

After February 26, COVID-19 (diagnosed by polymerase chain reaction testing) or COVID-like illness (classified by two of the researchers) was present in 6.5% of EMS-treated OHCAs and in 3.7% of those dead on EMS arrival.

Assuming a 10% risk for transmission to bystanders performing hands-only CPR without personal protective equipment (PPE), treating 100 patients could result in one bystander infection (10% with COVID-19 × 10% transmission), Sayre and colleagues estimate.

Given a 1% mortality for COVID-19, approximately one rescuer might die in 10,000 bystander CPR events.

The 10% transmission risk "is an assumption. Let's put that out there first of all. We don't have proof of that at all," Sayre said. "We looked at a variety of different scenarios that we thought were similar in our literature and picked a recent report in MMWR of healthcare workers taking care of one COVID patient in an ICU setting where they were not wearing any PPE and the risk of transmission in that cohort was well below 10%. And, even among caregivers who were doing more work around the patient's airway, there was a very low risk of transmission."

In addition, Sayre noted that none of the cardiac arrests occurring in public in the Seattle area involved COVID-19 patients, compared with 5% occurring in homes and 11% in nursing homes.

"So we felt pretty confident that a 10% transmission risk was pretty conservative and that the transmission risk is probably substantially lower than that," he said.

The 1% mortality for COVID-19 is also an assumption. "We're talking about a diverse group of bystanders, so it's possible that it's lower than that, it's possible it's a little bit higher," Sayre said. "Even if it is 2%, it doesn't actually change the answer much, it could be two in 10,000 then."

Asked for independent comment, Torben K. Becker, MD, PhD, chief of critical care medicine, and director of prehospital research at the University of Florida, Gainesville, said "the calculations they are trying to make are intriguing," but too narrow and simple. The true mortality of COVID-19 remains up in the air and there are many unknowns with regard to the risk for infection, he said.

Nevertheless, "I would say this study serves as sort of a reassurance that bystander CPR is still way more likely to create benefit rather than excess risk to the bystander, and with some very simple safety measures it might be possible to still safely perform bystander CPR, which we know is the number one thing in cardiac arrest outcomes," he said.

If people witnessing a cardiac arrest have concerns about COVID, they could significantly lower those concerns by putting a mask on before doing CPR, Becker said. "It's really a process that only takes a few seconds."

For many years, infectious disease was a particular concern for bystanders performing mouth-to-mouth CPR but that's changed in recent years, particularly with the shift to hands-only CPR, Becker observed.

Notably, causing additional harm and lack of appropriate skills were the leading concerns related to performing bystander CPR in a survey by Becker and colleagues. But that was in 2019, well before the COVID-19 pandemic.

"My concern is that if this persists, we could really have a huge step backwards because of people becoming afraid again of the exposure risk during CPR, which I think this study seems to support, to some degree, is overall still relatively low," he said.

Sayre reported receiving other support from Stryker/Physio-Control. Becker reported no relevant conflicts of interest.

Circulation. Published online June 4, 2020. Full text

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