Spontaneous Breathing Trials in Patients Managed with a Sedation Protocol or a Sedation Protocol with Daily Interruption

Objective

To describe adherence to SBT screening and conduct, and the rates of extubation after successful SBTs in patients enrolled in the SLEAP trial.

Methods

This was a secondary analysis of the SLEAP trial, which was conducted in 16 tertiary ICUs in Canada and the United States. The complete SLEAP trial methods relating to study participants, the nurse-directed sedation protocol, and daily sedation interruption have been published [5]. Before the SLEAP trial, 14 ICUs routinely employed SBTs as the standard of care to guide extubation decisions; and in 2 ICUs SBT use varied by clinician. During the SLEAP trial, respiratory therapists assessed extubation-readiness in a standardized fashion; they screened patients daily for eligibility to undergo an SBT using the following criteria: awake, adequate cough, PaO2>60 mmHg, SpO2 ≥ 90%, FiO2 ≤ 0.4, PEEP≤10 cm H2O, respiratory rate ≤35/min, minute ventilation ≤15 L/minute, no inotropes/vasopressors, mean arterial pressure >60 mmHg, and no evidence of myocardial ischemia. If all SBT criteria were met, patients underwent a 60-minute SBT, during which they breathed spontaneously through a T-tube circuit, a tracheotomy mask, or the ventilator circuit with continuous positive airway pressure of 5 cm H2O. Respiratory therapists could terminate the SBT if any of the following signs of failure persisted for more than 5 minutes: respiratory rate > 35/min, oxygen saturation <90%, heart rate >140/min or a change in heart rate ≥20% in either direction, systolic blood pressure <90 or >180 mmHg, or increased anxiety and diaphoresis. If the SBT was successful, respiratory therapists notified the ICU team for the purpose of prompt extubation. Weaning method and decisions to commence weaning and to extubate were at the discretion of the ICU team. When an SBT was not performed, or a patient was not extubated despite passing an SBT, respiratory therapists selected one of 8 reasons (agitation, procedure, physician request, worsening chest radiograph, mental status concerns, concern about airway patency, secretions, and inadequate cough or gag) or ‘other’ on the case report form .

Results

The frequency of screening for SBT eligibility was similar in the DI and control groups (92% versus 93% days) (Table 1). Among screened patients, the DI group were eligible for an SBT less often than the control group (32% versus 36% days, P=0.003). In both groups, respiratory therapists performed SBTs on 82% of days that SBT were indicated. Morning Sedation Agitation Scale (SAS) scores [6] was similar on days when SBTs were or were not done. The reasons for not performing an SBT when indicated differed between the groups. The most common reasons for missed SBTs in the DI group were patient agitation and concerns about airway patency. The most common reasons for not performing a SBTs in the control group were patient agitation, need for ICU procedures and physician request. The proportion of days patients passed an SBT but were not extubated was high and similar in the two groups (61% DI versus 65% control). Morning SAS scores were similar between days when ventilator support was removed or not removed. The reasons for not extubating a patient on the day of a successful SBT differed between groups. In both groups, the most commonly cited reasons from the options provided on the case report form were concerns about mental status and physician request. In the control group, clinicians more often selected miscellaneous reasons (‘other’) which were not listed on the case report form as a reason for delayed extubation, compared with the interruption group. More than one third of patients in both groups were extubated without an SBT (39% interruption versus 35% control, P=0.31). The proportion of patients extubated after the first, second, or third successful SBT was similar between groups. Despite differences in SBT conduct, the median time to successful extubation was 7 days in both groups [5].

Interpretation

In this multicenter trial, screening for SBT eligibility was frequent, and SBTs were commonly performed when patients met screening criteria. However, patients were extubated less than 40% of the time on the day of a successful SBT. Patients in the DI group met SBT criteria on fewer days than the control group, possibly because clinicians perceived patients in the DI group to be less alert, as indicated by more concerns about ‘mental status’ and ‘airway’, despite similar SAS scores. These concerns may reflect the higher doses of opioids and benzodiazepines received by the DI group [5]. A limitation of our study is that while we recorded many reasons that SBTs and extubation were not done when indicated, not all were captured on the case report form.These findings are consistent with the lack of benefit of DI when a sedation protocol is used. SLEAP was a pragmatic trial; therefore our findings related to SBT and extubation practices likely reflect usual practice; and are similar to the ABC trial in which 46% of patients were extubated on the day they first passed an SBT [4]. While screening and conduct of SBTs are easily protocolized, extubation decisions are challenging to protocolize as clinical judgment is necessary. Causes for delayed extubation once an SBT is passed represent an important yet understudied aspect of the process of liberation from mechanical ventilation.

Data expressed as n (%) unless otherwise indicated SBT=spontaneous breathing trial, SAS = sedation agitation scale