Tachypnea as a marker of respiratory distress is sensitive, but is not sufficiently specific to be used as a criterion in preextubation trials. Reliance on tachypnea as a preextubation trial failure criterion is likely to prolong intubation and ventilatory support for a large number of patients. Patient risks, determined by the extubation failures and reintubation rate, are the same.
ObjectiveThe objective of this study was to describe the development of a cost-effective ventilatory strategy using a portable microprocessor-controlled respiratory monitor (Bicore CP-1 00; Allied Healthcare Products, Riverside, CA).
Summary Background DataUntil recently, clinicians have had to accept the uncertainties of clinical judgment, which unfortunately, often biased the patient to a prolonged ventilatory course to avoid extubation failures, necessitating reintubation.
MethodsOver a 4-year period, the authors attempted to re-engineer the process of ventilatory support based on measured work of breathing (WOB),including physiologic (WOBphy,), imposed (WOB,mp) and total (WOBTot)
ResultsThe authors made 90 determinations of WOB in 31 patients. The coefficient of determination (r2) of WOBTot, with the breathing frequency was 0.35, with tidal volume was 0. 10, and with the rapid shallow breathing index (f/VT) was 0.23; therefore, the authors discarded them as reliable inferences. Of 27 patients ventilated for >2 days with satisfactory blood gases, but with breathing frequency > 30 breaths/minute, 6 had WOB-rt < 0.8 J/L and were extubated successfully. In 21 patients, WOBTOt was elevated to 1.6 ± 0.83 J/L, WOB1mp was 1.1 ± 0.64 J/L, approximately twice the WOBphys (0.5 ± 0.26 J/L), a normal value. Extubation was successful in 20 of those 21 patients. This approach was extended to the spontaneous breathing pre-extubation trial. In addition, the ventilator was adjusted so that the patient sustained a WOB-rt of 0.6 to 1 J/L during the ventilatory support. This evolution was tracked for 18 months in a series of 838 trauma intensive care unit patients. Average duration of ventilation decreased from 8.2 to 4.2 days (49%; p < 0.01). This translated into approximately 2400 decreased ventilator days per year.
ConclusionObjective measurement to guide the adequacy of ventilatory support and interpret apparent clinical weaning failures decreased total ventilatory time by 50%, permitting extubation in nearly 20% of patients previously considered failures.396
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