Ventilator Weaning by Protocol is Practical and Effective
Abstract & Commentary
Synopsis: A weaning protocol administered by respiratory therapists and authorized by each patient’s managing physician gained increasing acceptance in Ely and colleagues’ institution over the 12 months included in this study. Ely et al also identified and dealt with a number of barriers to protocol implementation.
Source: Ely EW, et al. Am J Respir Crit Care Med 1999;159:439-446.
This paper documents the process by which therapist-driven protocols (TDPs) for weaning patients from mechanical ventilation were successfully implemented in Ely and colleagues’ institution, a large university teaching hospital. During a 12-month period, Ely et al reintroduced a previously validated TDP throughout the hospital. This protocol relied on daily patient screening by respiratory therapists and requests to the patients’ managing physicians for permission to perform a spontaneous breathing trial.
The "readiness to wean" screen was considered to have been passed by the patient if all of the following criteria were met: the minute ventilation was less then 15 L/min, the inspired oxygen was less than 60%; positive end-expiratory pressure (PEEP) was less than 10 cm H2O, the PaO2/FIO2 ratio was greater than 200 mmHg, the rapid shallow breathing index (spontaneous tidal volume divided by respiratory rate) was 105 breaths/min/L or less, the patient had an adequate cough with suctioning, and there was no requirement for continuous infusion of pressor agents. If the managing physician provided an order to proceed with a spontaneous breathing trial, the patient was allowed to breathe through the ventilator circuit with 5 cm H2O or continuous positive airway pressure and flow triggering but without other support, or to be switched to a T-piece circuit. During the trial the patient was continuously monitored by the respiratory therapist and bedside nurse, who used pre-established criteria to return the patient to ventilatory support if spontaneous ventilation was not tolerated. Unassisted breathing for 30 to 120 minutes that was well tolerated by the patient was considered a positive trial.
During the 12-month study period, 1067 patients with respiratory failure required 9048 days of ventilatory support and were cared for by 117 respiratory therapists. With an intensive therapist education program about the use of the TDP, there was a progressive and significant increase in the rate of implementation of spontaneous breathing trials once daily screen criteria were met. As the year progressed, the number of participating physicians significantly increased. However, a number of problems were also identified. Spontaneous breathing trials were ordered more often on medical services than on surgical services (81 vs 63%; P = 0.004), and a questionnaire was used to determine physician barriers to protocol implementation.
Based on their experience with this study, Ely et al conclude that large-scale implementation of a TDP for ventilator weaning that does not require direct involvement of the managing physician during the weaning process is feasible in a large academic medical center. Further, they conclude that respiratory therapists can appropriately perform patient assessments and correctly interpret the data 95% of the time. Ely et al also emphasize the importance of recognizing barriers to successful implementation of a TDP for weaning. They point out the need for a staged implementation process, for intensive education of the respiratory therapists actually carrying out the protocol, and for periodic reinforcement of all participants in the process.
COMMENT BY DAVID J. PIERSON, MD, FACP, FCCP
Ventilator weaning has come full circle in the last 25 years. Before the mid-1970s, patients were fully supported until clinical assessment predicted that ventilation could be adequately maintained spontaneously, and then a trial of spontaneous breathing was carried out to determine whether that prediction had been correct. With the introduction of intermittent mandatory ventilation and later of pressure support as weaning techniques, focus shifted to the empirical reduction of ventilatory support, with assessment as to whether the patient was tolerating it. Attention tended to focus on the weaning technique rather than on the patient’s condition, and the assumption was often made that progressively stressing the ventilatory muscles would eventually enable the patient to breathe unassisted. In the last year or two, we have begun to return to the notion of more fully supporting ventilation, and periodically checking to see whether the patient has recovered to the point where spontaneous ventilation can be resumed.
This paper shows that a TDP based on daily patient screening for readiness to wean can be put into widespread clinical practice in the setting of a large teaching hospital. It takes a while for physicians to become comfortable with the idea of "turning their patients over to a protocol" rather than individually ordering every change in ventilator settings during the weaning process. However, the gradual transition documented here by Ely et al has been played out at numerous hospitals throughout the United States—and in community hospitals as well as big university teaching hospitals.
This paper also draws attention to a number of the problems encountered in implementing weaning protocols, and should facilitate the process in other institutions. The actual weaning protocol used by Ely et al, provided in the article’s appendix along with its accompanying documentation form, could probably be adopted unchanged in many institutions, avoiding the necessity of "reinventing the wheel." In other practice environments, however, clinician acceptance of TDPs may hinge on their incorporation of familiar local management routines. Whichever route is taken, it is likely that weaning by TDPs will be done in more institutions in the coming years.
A spontaneous breathing trial would be recommended in a patient with all but which one of the following findings?
a. A PaO2/FIO2 ratio of 250 mmHg.
b. An FIO2 of 55%.
c. A spontaneous tidal volume over respiratory rate of 80 breaths/min/L.
d. A positive end-expiratory pressure of 12 cm H2O.
e. A minute ventilation of 12 L/min.
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