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Taking slow vent weans by the collar

Our ICUs are crowded by patients that are slow to liberate from mechanical ventilation. In North America, such patients are often transferred to long term mechanical ventilation facilities (LTAC) – where they are weaned to liberation. There are many strategies for weaning tracheostomised  patients from mechanical ventilation – a progressive reduction in pressure support, intermittent tracheal mask (trach collar) trials, external CPAP etc.

Martin Tobin has, for many years, questioned the now conventional wisdom of progressive pressure support weans, and in this weeks JAMA his group have published a paper comparing Volume Assist Control Ventilation with intermittent tracheal mask trials to progressive pressure support weaning. The patients in the pressure support group (PSG) started, if they were able to tolerate it, pressure support ventilation at 14cmH2O. Tolerance to wean was checked every 6 hours, and 2cmH2O decrements of PS were applied up to a maximum of 6cmH2O per day. Once the pressure support reached 6cmH2O, a 5 day vent liberation process began. In the tracheal mask group (TMG), patients were put on tracheal mask  for up to 12 hours per day for 2 days (then back on assist control) and on day 3 started on the 5 day vent liberation programme.

The primary outcome was weaning duration, defined from the first day of randomization to the day the patient was successfully weaned. Weaning was considered successful when patients breathed without ventilator assistance for at least 5 days. If the patients had not liberated by day 45, this was considered “failure to wean.”

Three hundred and twelve patients were randomized, of which one third died while in the study (equal numbers each group). Among the entire group of randomized patients (n = 312), median weaning time was shorter in TMG versus PSG: 15 days (IQR, 8-25) vs 19 days (IQR, 12-31), P = .004.. Among patients who completed the study (n = 194), median weaning time was shorter in TMG vs PSG: 13 days (IQR, 8-30) vs 19 days (12-43), P = .006.

Weaning time had no effect on survival at 6 and 12 months.

Impression: this article suggests that weaning patients using decrements of pressure support is not aggressive enough and that weaning in more likely to be successful with unassisted tracheal mask. Although, unsurprisingly, this had no effect on survival, a 6 day reduction in ventilator times translates into considerable resource savings – particularly with ICU/HDU beds are very scarce (as in our hospitals). Whether or not patients should be weaned from assist-control or high levels of pressure support appear moot: I doubt that it makes a difference. I continue to see any value for using external CPAP through a t-piece as a vent liberation process: there is not a shred of supportive evidence.

About Pat Neligan

Pat Neligan lives and works in Galway, Ireland

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