Dr. Frederick M. Burkle Jr., a former Vietnam War physician, laid out ideas for how to handle the victims of a large-scale bioterrorist event. After the SARS outbreak stressed Toronto hospitals in 2003, some of his ideas were proposed by Canadian doctors, and they made their way into many American plans after the H1N1 pandemic in 2009. “I have said to my wife, ‘I think I developed a monster here,’” Dr. Burkle said in an interview.

What worried him was that the protocols often had rigid exclusion criteria for ventilators or even hospital admission. Some used age as a cutoff or pre-existing conditions like advanced cancer, kidney failure or severe neurological impairment. Dr. Burkle, though, had emphasized the importance of reassessing the level of resources sometimes on a daily or hourly basis in an effort to minimize the need to deny care.

Also, the plans might not achieve their goals of maximizing survival. For example, most called for reassigning a ventilator after several days if a patient was not improving, allowing it to be allocated to a different patient.

But rapidly cycling ventilators might not give anyone enough chance to improve.