What ‘flattening the curve’ really means, and why it’s so important in the coronavirus outbreak
Flatten the curve. That’s the rallying cry of the coronavirus pandemic.
But what does that mean and why is it so important?
The drastic measures put in place by Washington Gov. Jay Inslee, President Donald Trump and other government officials aren’t meant to stop the disease from spreading. They are meant to slow the spread of the coronavirus. That, in turn, buys more of a crucial resource: time.
Time to conduct clinical trials, learn which therapies patients are responding to and develop a vaccine. Fewer people suddenly showing up at hospitals also helps to reduce the stress on an overburdened medical system.
“We have more tools to work with,” said Dr. James Town, director of the medical intensive care unit (ICU) at Harborview Medical Center in Seattle. He’s the person responsible for arranging his ICU’s response to COVID-19.
The coronvirus infection rate curve explains why time is critical.
A so-called thermometer chart might only show the total numbers of coronavirus cases on a given day. That number reached 10,000 in the U.S. on Thursday. But, it can’t tell you the numbers from yesterday, last week or last month.
The rise, peak and eventual fall of those coronavirus numbers can be seen when the factor of time is added — a chart with the number of total cases for each day of the calendar, for example.
Those total numbers, expressed graphically, can create a curve. If numbers fall in the same manner as they rose over time, the shape is often referred to as the classic bell curve.
Crisis standards of care
On Wednesday, Town had only a couple of COVID-19 patients in the ICU, but there were another two or three under investigation and still others in acute care, he said.
Town looks at the pandemic numbers in terms of percentages within percentages.
Not every person in Washington state is going to be infected with the coronavirus. Not every infected person will develop COVID-19. Not every person who develops COVID-19 will need acute care.
“But some fraction do,” Town said Wednesday. And it’s that fraction, if there’s enough of them, who can overwhelm a medical system. They compete for space with each other along with cardiac patients, accident victims and anyone else experiencing a health emergency.
As of Thursday, 74 people in Washington state have died from COVID-19. One week ago that number stood at 30. One month ago it was zero.
Sometimes, a dashed horizonal line is added to a chart to illustrate a benchmark or limit. The line can slide though the curve if it’s steep. Or, it can hover above it if the curve is flat.
In this case, the dashed line represents the capacity of a region’s medical system.
“If that curve is short and steep and then it crosses over that dashed line, all of the people above that dashed line represent the people who won’t be able to get the services we usually provide,” Town said.
It’s at that point that a hospital like Harborview would switch to crisis standards of care. That’s the worry in Italy, where the country’s medical system is at the breaking point.
“It may not mean immediately going into triage (a classification system where some patients are left to die),” he said. “It may just mean accepting different alternatives from what we normally do.”
A CPAP (continuous positive airway pressure) machine normally used by people with sleep disorders might be repurposed into a ventilator, he said. A ventilator helps patients breathe and is normally only used in medical settings.
Why a flat curve is better
“The flat curve has, potentially, the same number of infected people that need medical attention,” Town said. “But, if you can slow the transmission down, then not all those people are coming at once. Then, you don’t overwhelm the capacity of the medical system.”
Either way, there’s still going to be a lot of strain on the medical system. But the flat curve, Town said, is more adaptable than a steep one.
The medical system is expandable, Town said. A post-anesthesia care unit or an operating room can be converted into an ICU, for example. Ventilators can be rented. Staff can work overtime.
But the expansion can only go so far.
For every patient on a ventilator, the system needs doctors, nurses, personal protection equipment, beds and other resources. Staff can only work so long. And, they can get sick.
Currently, the medical system is recruiting staff and volunteers to help with the coming expected influx, he said.
“People are heeding that call,” Town said.
Some medical personnel are being repurposed.
Surgeons, for example, might have little work on their schedule following the cancellation of elective surgeries. But, they still went to medical school and still know who to take care of patients, Town said.
“We’re making some people do jobs they didn’t use to do,” Town said.
The good news is that we can learn from other countries, he said. China, Italy and Iran, where the disease has had a much stronger grip, offer signs of how to proceed.
“We know what’s coming,” Town said.
This story was originally published March 20, 2020 at 5:00 AM with the headline "What ‘flattening the curve’ really means, and why it’s so important in the coronavirus outbreak."
