Self-measurement of oxygen levels with pulse oximeters is no better than just regularly asking patients with COVID if they are short of breath, according to new research published in the New England Journal of Medicine. Pulse oximeters have often been applied because of concerns that patients might not notice their blood oxygen levels sliding dangerously.
However, people in Penn Medicine’s COVID Watch programme, which monitors patients recovering at home via automated text messaging, had the same outcomes whether they used oxygen-measuring devices or not.
“Compared to remotely monitoring shortness of breath with simple automated check-ins, we showed that the addition of pulse oximetry did not save more lives or keep more people out of the hospital,” said the study’s co-lead author, Anna Morgan, MD, medical director of the COVID Watch program and an assistant professor of General Internal Medicine. “And having a pulse oximeter didn’t even make patients feel less anxious.”
The COVID Watch was launched in March 2020 to remotely monitor COVID patients at home, with 28 500 people enrolled to date. Twice a day for two weeks, text messages were automatically sent to these patients asking how they felt and if they were having difficulty breathing. If patients indicated dyspnoea, the programme would alert a nurse to make contact and arrange care.
“The programme made it easy to identify the sickest patients who needed the hospital, and keep the others at home safely,” said David Asch, MD, executive director of the Center for Health Care Innovation and a professor of Medicine, Medical Ethics and Health Policy. “The programme was associated with a 68 percent reduction in mortality, saving a life approximately every three days during peak enrollment early in the pandemic.”
However it was not known if monitoring blood oxygen would help.
“Early in the pandemic, there was a prevalent theory that oxygen levels in the blood dropped before a COVID patient became symptomatic and short of breath,” said study co-lead author Kathleen Lee, MD. “Detecting this earlier with a home pulse oximeter might provide an opportunity to get patients who are on the cusp of deteriorating to the hospital faster and initiate time-sensitive therapies to improve outcomes.”
The use of pulse oximeters was so intuitively appealing that the process got adopted even before this trial, the first randomised trial to test whether it actually worked.
“Several health systems, and even states like Vermont and countries like the United Kingdom, have integrated pulse oximetry into the routine home management of patients with COVID, but there’s been scant evidence to show this strategy makes a difference,” said the research project’s principal investigator M. Kit Delgado, MD.
In this study, more than 2000 patients enrolled in COVID Watch between Nov. 29, 2020, and Feb. 5, 2021, were randomised to receive standard COVID Watch care or the same program with the addition of a pulse oximeter.
However, no statistical difference was seen in the main study measure, the average number of days enrolled patients spent alive and out of the hospital in the 30 days after they were enrolled. For patients with pulse oximeters, the measure was 29.4 days; for those without, it was 29.5, with no difference across racial liines. This was important as black patients are known to have had worse COVID outcomes and concerns had been raised about the accuracy of pulse oximeters in people with darker skin.
The researchers cautioned that the study focused on pulse oximeters in established programme of remote monitoring, and patients don’t have access to a system like COVID Watch or on-call clinicians, self-monitoring with pulse oximeters may still be a reasonable approach until there is evidence to the contrary.
“Overall, these findings suggest that a low-tech approach for remote monitoring systems based on symptoms is just as good as a more expensive one using additional devices. Automated text messaging is a great way for health systems to enable a small team of on-call nurses to manage large populations of patients with COVID,” said co-principal investigator, Krisda Chaiyachati, MD. “There are a lot of other medical conditions where the same kind of approach might really help.”