The study by Krishnan et al highlighted the importance of the “organizational context,” which relates to factors such as staffing, “usual care,” type of ICU (surgical, medical, neurosurgical, etc), bed availability, and even an open versus a closed ICU model. It points to redundancies in hospitals and medical centers where a high staffing level is likely to promote early recognition and transition to weaning and extubation without the need for a choreographed structure.25,26 Usual care refers to the customary practices performed at a particular ICU. At Johns Hopkins Hospital where the Krishnan study was conducted, high-level, evidence-based practice with 24-hour ICU physician coverage (ie, usual care) may explain the lack of difference in outcomes and the apparent ineffectiveness of PBW.27 Protocolized weaning may be more suitable to hospitals that lack 24-hour coverage by intensivists or other physicians versed in the weaning cultures.
The type of ICU can play an important role in the weaning process. For example, a postanesthesia care unit (PACU) or a surgical ICU may not embrace the time-consuming and restrictive PBW. The daily screen is often disregarded in favor of an expeditious SBT in the majority of patients in the PACU or surgical ICU, thereby avoiding the burden of fulfilling stringent weaning criteria. No benefits were demonstrated when PBW was tried in neurosurgical and trauma ICUs, reinforcing the limitations associated with certain types of ICU.23,24 Although safe and effective, PBW may miss many patients that could be extubated sooner than what is predicted by established protocol criteria. As previously reported, half of the patients who self-extubate prematurely, do not require reintubation within a 24-hour period.28,29
Another major concern regarding PBW lies in the heterogeneity of the published studies and their conflicting and inconsistent results. Hospital and ICU cultures, resources and settings heavily influence the methodology and protocol designs of these trials, resulting in a vast array of treatment algorithms. In the meta-analysis of 11 randomized controlled trials (RCTs) by Blackwood et al, readiness to wean criteria (daily screen) differed in every single study.18 Likewise, there was variability in the staff members (RTs, RNs, or physicians) involved in the application of the study protocols. Of the 11 studies, only 2 employed the same weaning protocol while the remainder used different combinations of weaning methods for liberation from IMV. The weaning modality (eg, PSV, T-piece trials, SIMV, or CPAP) also differed between the studies but did not impact the process of adequately identifying prospective candidates for liberation from IMV.10,20 The results of these studies are hardly reproducible and centers should be mindful and perform careful assessment of a protocol before its implementation.
Despite these limitations, a large body of evidence argues in favor of an RN/RT-led approach to weaning when compared to conventional (ie, no protocol) weaning by physicians (Table 65–3). Indeed, RN- and RT-directed protocols appear to be safe, beneficial and cost-effective. Certainly, healthcare providers who spend a lot of time with patients are well equipped to recognize the best time for extubation. PBW is relatively easy to incorporate into the culture of an ICU because RNs and RTs are widely available in many ICUs and they are consistently present at a patient’s bedside.
RN/RT-led PBW appears ideal for patients in the “simple weaning” category and for most patients in the “difficult weaning” group. Patients in the “prolonged weaning” group and a few patients in the “difficult weaning” category should undergo further workup to identify barriers to successful liberation from IMV. Imaging studies, electromyography and nerve conduction testing, serologic markers for vasculitides, myopathies and endocrinopathies, esophageal manometry, etc may be necessary to diagnose medical conditions that impede weaning and to develop appropriate plans of treatment.30,31
In the past few years, a new paradigm has emerged with the concepts of limited/no sedation and early ICU mobilization (early rehabilitation therapy) as adjuncts in liberating patients faster from IMV.32,33,34,35,36 A small number of RCTs and prospective studies have demonstrated that early mobilization of patients requiring mechanical ventilation was not only safe and feasible but also associated with increased ventilator-free days, shorter return time to baseline functional capacity, and reduced ICU and hospital LOS, mortality and costs.33,34,35 In the majority of cases, early mobilization was possible at a median of 1.5 days (range of 1-2.1 days) after initiation of IMV.35