Re-Engineering Ventilatory Support to Decrease Days and Improve Resource Utilization

Abstract

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

Pressure Support Ventilation Advisory System Provides Valid Recommendations for Setting Ventilator

“…In another study, an approach akin to an open-loop PSV system was employed, in which the response or input variable was WOB per breath, directly measured with an esophageal balloon catheter, and the output variable was PSV. 2 The clinicians maintained WOB per breath in a specific and fairly normal physiologic range by increasing or decreasing PSV as needed. When WOB per breath was maintained in that range with PSV, adults weaned faster than with the traditional method.…”

“…In adults treated with PSV it was found that WOB of 2-8 J/min was well tolerated. 3 Another clinical study 2 reported that WOB maintained in a fairly normal range during PSV was well tolerated. Our PSV advisory system's target f and V T ranges are congruent with those applied to spontaneously breathing adults receiving PSV: 10 -25 breaths/min, and 6 -8 mL/ kg, respectively.…”

“…[1][2][3] The inspiratory muscles become loaded due to decreased respiratory system compliance and/or increased respiratory system resistance. The amount of inspiratory positive pressure assist applied with PSV is typically determined by observing the patient's spontaneous breathing pattern.…”

“…The inspiratory muscle load, which can be assessed by work of breathing per minute (WOB/min), is thought to be appropriate when the spontaneous breathing frequency (f) and tidal volume (V T ) are in clinically acceptable ranges, a comfortable breathing pattern is present, and accessory inspiratory muscles (eg, sternocleidomastoid) are not active. Because inspiratory muscle load and breathing-pattern data do not always correlate when applying PSV, 2,3 SEE THE RELATED EDITORIAL ON PAGE 359 another approach is to consider using measured values for WOB/min, f, and V T , and then using a portable computerized bedside monitor to assess the interrelationships of these values and formulate recommendations for setting PSV.…”

Assessment of lung function in the ventilated patient

“…Some studies have found WOB to be a sensitive method of predicting successful weaning and extubation [57] although others have not been able to confirm this [58]. Differentiating the WOB into its components has revealed that in certain circumstances imposed WOB may be the most significant factor increasing total WOB such that patients benefit from discontinuation of respiratory support [59].…”