番茄社区

Easing the traumatic "air hunger" created by mechanical ventilation settings for COVID-19 acute respiratory distress syndrome (ARDS) may take more than just sedation or paralytics, one group argued.

Lung protective ventilation, with low tidal volumes and permissive hypercapnia, is a recipe for "the most uncomfortable form of dyspnea," Richard Schwartzstein, MD, of Beth Israel Deaconess Medical Center and Harvard in Boston, wrote in the .

The feeling of wanting to breathe but being unable due to ventilation "evokes fear and anxiety, so much so that involuntary air hunger has been used as a very effective form of torture (e.g. waterboarding)," the group noted. "Among ICU survivors, the experience of air hunger is associated with post-traumatic stress disorder (PTSD)."

"With the likelihood that hundreds of thousands of dyspneic patients will require low tidal volume mechanical ventilation around the world, we are concerned about the potential for mass psychological trauma in the survivors induced by untreated air hunger during this pandemic," they wrote.

Critical care physician Robert Dickson, MD, of the University of Michigan School of Medicine in Ann Arbor, agreed.

"It's turning out that survival among mechanically ventilated COVID patients is far better than was initially reported," he commented in an email to 番茄社区. "This is great news, but it does mean there will be more COVID ICU survivors dealing with the persistent effects of critical illness, including psychological distress."

Dyspnea is hard to estimate from observing patients and not relieved by going on mechanical ventilation, Schwartzstein's group noted.

Neuromuscular blockade used to keep patients from self-extubation doesn't actually help either, despite persistent misconceptions based on theories disproven decades ago, they added. Paralysis just makes it harder to observe signs of dyspnea.

Benzodiazepines aren't effective and may actually exacerbate psychological trauma from the experience; propofol has no data on dyspnea impact, although high doses that cause ventilatory depression may offer some relief.

"Opiates are the most reliable agent for symptomatic relief of air hunger -- they seem to act both through depression of ventilatory drive and ascending perceptual pathways, as they do with pain," the group wrote. Even low doses have been shown to relieve air hunger both in healthy volunteers and clinical studies.

However well known among ICU clinicians, opiates remain underutilized, they argued. For instance, only 60% of ARDS patients in the got opioids as part of their initial sedation strategy. The rate was 55% in a small meta-analysis of ARDS studies.

"There has been a tendency to equate 'sedation' with an 'anti-dyspnea' effect and the push has been to use sedation primarily because patients are often anxious and agitated when being treated with mechanical ventilation," Schwartzstein said in a press release. "We now know that many sedatives do not relieve dyspnea and we urge doctors to use opiates for dyspnea and sedatives, when needed, for anxiety and agitation."

Worries about longer-term addiction potential shouldn't hold physicians back, Dickson argued.

"These are powerful medicines that we use judiciously in the safest possible setting," he said. "I would not let concerns for long-term dependence dissuade us for using them humanely in critically ill patients."

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