This is interesting and possibly important; an excerpt, but do read it all:
What’s driving this reassessment [of ventilator use] is a baffling observation about Covid-19: Many patients have blood oxygen levels so low they should be dead. But they’re not gasping for air, their hearts aren’t racing, and their brains show no signs of blinking off from lack of oxygen.
That is making critical care physicians suspect that blood levels of oxygen, which for decades have driven decisions about breathing support for patients with pneumonia and acute respiratory distress, might be misleading them about how to care for those with Covid-19. In particular, more and more are concerned about the use of intubation and mechanical ventilators. They argue that more patients could receive simpler, noninvasive respiratory support, such as the breathing masks used in sleep apnea, at least to start with and maybe for the duration of the illness....
An oxygen saturation rate below 93% (normal is 95% to 100%) has long been taken as a sign of potential hypoxia and impending organ damage. Before Covid-19, when the oxygen level dropped below this threshold, physicians supported their patients’ breathing with noninvasive devices such as continuous positive airway pressure (CPAP, the sleep apnea device) and bilevel positive airway pressure ventilators (BiPAP). Both work via a tube into a face mask.
In severe pneumonia or acute respiratory distress unrelated to Covid-19, or if the noninvasive devices don’t boost oxygen levels enough, critical care doctors turn to mechanical ventilators that push oxygen into the lungs at a preset rate and force: A physician threads a 10-inch plastic tube down a patient’s throat and into the lungs, attaches it to the ventilator, and administers heavy and long-lasting sedation so the patient can’t fight the sensation of being unable to breathe on his own.
But because in some patients with Covid-19, blood-oxygen levels fall to hardly-ever-seen levels, into the 70s and even lower, physicians are intubating them sooner...
In patients who are on ventilators due to non-Covid-19 pneumonia or acute respiratory distress, a blood oxygen level in the 80s can mean impending death, with no room to give noninvasive breathing support more time to work. Physicians are using their experience with ventilators in those situations to guide their care for Covid-19 patients. The problem, critical care physician Cameron Kyle-Sidell told Medscape this week, is that because U.S. physicians had never seen Covid-19 before February, they are basing clinical decisions on conditions that may not be good guides....
In a letter last week in the American Journal of Respiratory and Critical Care Medicine, researchers in Germany and Italy said their Covid-19 patients were unlike any others with acute respiratory distress. Their lungs are relatively elastic (“compliant”), a sign of health “in sharp contrast to expectations for severe ARDS.” Their low blood oxygen might result from things that ventilators don’t fix. Such patients need “the lowest possible [air pressure] and gentle ventilation,” they said, arguing against increasing the pressure even if blood oxygen levels remain low. “We need to be patient.”
“We need to ask, are we using ventilators in a way that makes sense for other diseases but not for this one?” Gillick said. “Instead of asking how do we ration a scarce resource, we should be asking how do we best treat this disease?”
Researchers and clinicians on the front lines are trying. In a small study last week in Annals of Intensive Care, physicians who treated Covid-19 patients at two hospitals in China found that the majority of patients needed no more than a nasal cannula. Among the 41% who needed more intense breathing support, none was put on a ventilator right away. Instead, they were given noninvasive devices such as BiPAP; their blood oxygen levels “significantly improved” after an hour or two. (Eventually two of seven needed to be intubated.) The researchers concluded that the more comfortable nasal cannula is just as good as BiPAP and that a middle ground is as safe for Covid-19 patients as quicker use of a ventilator....
One reason Covid-19 patients can have near-hypoxic levels of blood oxygen without the usual gasping and other signs of impairment is that their blood levels of carbon dioxide, which diffuses into air in the lungs and is then exhaled, remain low. That suggests the lungs are still accomplishing the critical job of removing carbon dioxide even if they’re struggling to absorb oxygen. That, too, is reminiscent of altitude sickness more than pneumonia.
