In a randomized controlled trial performed at Bowman Gray University, 300 patients were screened daily for PO2/FiO2 greater than 200, PEEP less than 5, adequate cough, a rapid shallow breathing index (frequency/tidal volume) less than 105, and minimal vasopressors or sedation. Patients in the intervention arm automatically received a two-hour trial of spontaneous breathing when they fulfilled the screening criteria. If they passed the two-hour trial (assessed by strict clinical criteria), an investigator personally informed the primary physician that the patient had an "85% chance of successfully staying off mechanical ventilation for 48 hours." The intervention group had a 25% reduction in days of mechanical ventilation and a similar reduction in ICU costs. There was no effect on ICU length of stay, hospital length of stay, or total hospital costs. (Ely EW, et al. N Engl J Med 1996;335:1864-1869.)
COMMENT BY GORDON D. RUBENFELD, MD
Few topics in critical care medicine engender more heated debate than weaning patients from mechanical ventilation. An endless supply of review articles and debates at national meetings competes with each clinician’s individual biases for the best weaning strategy. Investigators in this recent article throw more fuel into the fire. They reduced mechanical ventilation time by 25%, and they did it without a fancy new mode of ventilation, without an expensive work of breathing monitor, without noninvasive bridge ventilation, and without a modified nutritional formula. They did it with a telephone call.
There is nothing startling about the measurements used in the screening protocol in this study; they are fairly standard "weaning criteria." And, there is certainly nothing new about a two-hour "CPAP trial." However, these results indicate that some patients in the control arm of this study who would have passed the spontaneous breathing trial and been successfully extubated were kept on mechanical ventilation for days or even weeks. No doubt, many readers are silently thinking that their ICU would not benefit from a similar intervention because they identify and promptly extubate patients who would pass a two-hour CPAP trial. In fact, ICUs that routinely perform weaning parameters or those that use respiratory care protocols might not benefit as much from the intervention used in this study. However, many ICUs, particularly those with "open" admission policies (that is, where all hospital staff have ICU admission privileges), are likely to reduce duration of mechanical ventilation by instituting a clinical guideline that incorporates: 1) daily screening using criteria similar to those in this study, 2) a trial of spontaneous breathing for those who fulfill screening, and, perhaps most importantly, 3) verbal communication of these results from a physician to an attending responsible for the extubation decision.
This was not a study of "difficult-to-wean" patients. Half of the patients were ventilated for less than three days before successfully passing the screening criteria. In fact, it was not really a study of weaning. Nothing in this protocol was designed to get difficult-to-wean patients off the ventilator faster. However, it does reveal an important issue for interpreting studies of ventilator modes or monitors intended to reduce weaning time. Since simply having a protocol in place to identify extubatable patients appears to reduce mechancial ventilation days by 25%, patients in future weaning studies will need to receive similar screening. If not, then a new monitoring gadget that appears to reduce ventilator days compared to "standard care" in a randomized trial may only do so because the patients who were monitored with the gadget also received more careful screening for early extubation independent of the effect of the monitor.
Clinicians may need some help in weaning themselves from prolonged and complex weaning. Luckily, it looks as if verbal feedback guided by simple protocols can do the trick.
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