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Shortage of mechanical vents seen for pandemic, airborne terrorism
Tough choices may have to be made about who gets one
A dire shortage of mechanical ventilators appears to be the weakest link in any emergency response to an airborne bioterrorism threat or pandemic influenza outbreak, a recently published study by the Centers for Disease Control and Prevention found.1
Though the data were collected in 2003-2004 — and thus are regarded essentially as a "baseline" reading in the aftermath of 9/11— there is broad consensus that the problem has not been resolved, says lead author Richard Niska, MD, a medical epidemiologist in the CDC division of health care statistics.
"The literature in general raises the specter that there wouldn't be enough," he tells Bioterrorism Watch. "With a lot of ventilators already spoken for by people with lung problems, if there was any mass influx of people with pulmonary problems due to anthrax or something like that, there would be a shortfall. I don't think there is any literature out there that says we are ready. We need much more than we have now if there was a mass casualty attack or flu pandemic, where a lot of people would need ventilator support."
The 2003 and 2004 National Hospital Ambulatory Medical Care Survey included a Bioterrorism and Mass Casualty Preparedness Supplement to assess a nationally representative sample of hospitals for their ability to respond to mass casualties. The CDC found that hospitals nationwide have available an average of only 12 mechanical ventilators each.
The CDC cited another study published last year that underscores the hard choices necessary to deal with such a situation.2 In a hypothetical pneumonic plague epidemic involving 400 patients, a regional 27-hospital system in the Minneapolis area rapidly experienced a major shortage of ventilators. Although 480 intensive care beds were available in that system, one would presume that many of these were already in use. The drill also revealed little potential for backup, with only 16 ventilators available for purchase from regional vendors. The authors therefore proposed a three-stage triage system for either instituting or continuing mechanical ventilation, based on objective clinical factors related to survival potential and available resources, but not on patient age or subjective value judgments. The system, which would involve a change in the standard of care, would be implemented through the health department and supported by a declaration from the state governor with professional liability protections, the CDC reported.
"Because many epidemic and bioterrorist agent illnesses involve respiratory failure, mechanical ventilation is a frequently required intervention but one that is in limited supply," wrote John L. Hick, MD, lead author of the Minneapolis paper. "In advance of such an event, we must develop triage criteria that depend on clinical indicators of survivability and resource utilization to allocate scarce health care resources to those who are most likely to benefit. These criteria must be tiered, flexible, and implemented regionally, rather than institutionally, with the backing of public health agencies and relief of liability."
The authors of another recent paper warn a severe pandemic could create demand for mechanical ventilators that may far exceed the reserves in the CDC's Strategic National Stockpile (SNS).3 They used the CDC's FluSurge modeling software to predict the effects of planning assumptions for a severe pandemic, finding that typical city, with a pandemic of moderate duration and attack rate (eight weeks and 25%, respectively), at epidemic peak (Week 5), flu patients would require 191% of all nonintensive care unit (ICU) beds, 461% of all available ICU beds, and 198% of all available mechanical ventilators. Even with greatly increased reserves, the SNS will not be able to provide supplies of ventilators adequate to meet the needs of hospitals in a pandemic. Moreover, they will not be able to rent equipment, and it is not practical for hospitals to purchase, maintain, and store expensive full feature mechanical ventilators just to have them on hand in case they are needed, according to the report and a subsequent analysis of the findings in the Center for Biosecurity Network Report.4 The authors assert that alternative positive pressure ventilation (PPV) equipment, designed and used for short term PPV in non-ICU locations, but suitable for definitive mechanical ventilation during mass casualty events, should be considered. This equipment is available, less expensive, and more easily stockpiled than full feature mechanical ventilators, they argue. Moreover, alternative PPV equipment must be easy for noncritical care staff, with limited training and experience, to operate, as it is likely that they will be called upon to help manage patients with respiratory failure in a mass casualty setting.
However, because it also may have to be used outside of an ICU, alternative PPV equipment must have appropriate alarm capabilities, battery power, and the ability to function with either high-and low-pressure oxygen sources. The authors conclude that portable ventilators with internal compressors and oxygen blenders will be the most oxygen sparing and will meet most of the criteria for the ideal mass casualty PPV device. They also point out that a stockpile of PPV equipment alone will not be adequate or sufficient. Shortages of critical care staff will be a limiting factor in any emergency response, which means that cross-training of noncritical care staff must be central to any effort to expand hospital surge capacity.
"It all speaks to surge capacity — the number of hospitals beds, doctors, nurses, and equipment," notes Niska.
In other specific findings of the 2003-2004 survey, about 92% of hospitals had revised their emergency response plans since Sept. 11, 2001, but only about 63% of those had addressed all five preparedness scenarios: natural disasters, biological, chemical, radiological, and explosive terrorism. The remaining 37% had addressed one or more of the scenarios, he says. The CDC is planning to update its hospital emergency response study in 2008 with likely publication in a year or two to follow. Will hospitals show greater levels of preparedness than the 2003-2004 survey?
"That would be my hope, but without studying it we don't know," Niska says. "The [post-911] funding may have made a difference and everybody was able to ramp up everything. Or it is possible since there have been no terrorists attacks since then that people went on and looked at other things related more to day-to-day concerns."