Frequency of Screening for Weaning From Mechanical Ventilation

Two Contemporaneous Proof-of-Principle Randomized Controlled Trials

Karen E. A. Burns, MD, FRCPC, MSc; Jessica T. Y. Wong, BSc, MPH; Peter Dodek, MD, MHSc; Deborah J. Cook, MD, FRCPC, MSc; Francois Lamontagne, MD, FRCPC, MSc; Ashley Cohen, PhD; Sangeeta Mehta, MD, FRCPC; Michelle E. Kho, PT, PhD; Paul C. Hebert, MD, FRCPC, MSc; Pierre Aslanian, MD, FRCPC; Jan O. Friedrich, MD, FRCPC, DPhil; Laurent Brochard, MD; Leena Rizvi, BSc; Lori Hand, BSc, RRT; Maureen O. Meade, MD, FRCPC, MSc; Andre C. Amaral, MD, FRCPC, MSc; Andrew J. Seely, MD, PhD, FRCSC; for the Canadian Critical Care Trials Group


Crit Care Med. 2019;47(6):817-825. 

In This Article

Abstract and Introduction


Objectives: It is unknown whether more frequent screening of invasively ventilated patients, identifies patients earlier for a spontaneous breathing trial, and shortens the duration of ventilation. We assessed the feasibility of conducting a large trial to evaluate screening frequency in critically ill adults in the North American context.

Design: We conducted two contemporaneous, multicenter, pilot, randomized controlled trials (the LibeRation from MEchanicaL VEntilAtion and ScrEening Frequency [RELEASE] and Screening Elderly PatieNts For InclusiOn in a Weaning [SENIOR] trials) to address concerns regarding the potential for higher enrollment, fewer adverse events, and better outcomes in younger patients.

Setting: Ten and 11 ICUs in Canada, respectively.

Patients: Parallel trials of younger (RELEASE < 65 yr) and older (SENIOR ≥ 65 yr) critically ill adults invasively ventilated for at least 24 hours.

Interventions: Each trial compared once daily screening to "at least twice daily" screening led by respiratory therapists.

Measurements and Main Results: In both trials, we evaluated recruitment (aim: 1–2 patients/month/ICU) and consent rates, reasons for trial exclusion, protocol adherence (target: ≥ 80%), crossovers (aim: ≤ 10%), and the effect of the alternative screening frequencies on adverse events and clinical outcomes. We included 155 patients (53 patients [23 once daily, 30 at least twice daily] in RELEASE and 102 patients [54 once daily, 48 at least twice daily] in SENIOR). Between trials, we found similar recruitment rates (1.32 and 1.26 patients/month/ICU) and reasons for trial exclusion, high consent and protocol adherence rates (> 92%), infrequent crossovers, and few adverse events. Although underpowered, at least twice daily screening was associated with a nonsignificantly faster time to successful extubation and more successful extubations but significantly increased use of noninvasive ventilation in both trials combined.

Conclusions: Similar recruitment and consent rates, few adverse events, and comparable outcomes in younger and older patients support conduct of a single large trial in North American ICUs assessing the net clinical benefits associated with more frequent screening.


Approximately 40% of the time patients spend on invasive ventilation is dedicated to weaning.[1] Reducing the duration of invasive ventilation and the risk of ventilator-related complications is a priority in the ICU.[2,3] To address these goals, trials have evaluated the use of screening protocols to identify candidates to undergo a spontaneous breathing trial (SBT), different SBT techniques, and specific strategies to liberate patients who fail an initial SBT.[4–12] A meta-analysis of 17 randomized controlled trials found that compared with usual care, screening protocols reduced weaning time, the total duration of ventilation, and ICU length of stay.[13] Only one trial compared twice daily screening to usual care and demonstrated favorable effects of more frequent screening on duration of ventilation and ventilator-associated pneumonia (VAP) rates.[6] No trial has compared a strategy of more frequent screening to once daily (OD) screening to identify SBT candidates. National and international surveys suggest that OD screening is the current standard of care.[14,15] However, OD screening is not patient-focused and is poorly aligned with the continuous care provided in ICUs, wherein a patient's status can change from hour to hour.[16] Furthermore, it disregards the impact that decisions made during daily rounds can have on patient's ability to undergo an SBT later the same day. With respiratory therapists (RTs) available continuously in most North American ICUs, an opportunity exists to screen patients more frequently, conduct more SBTs, and reduce the time patients spend on ventilators and in the ICU.

Although 26% to 51% of ICU admissions occur in patients who are at least 65 years old, only one weaning trial involving 38 patients with chronic obstructive pulmonary disease has been conducted in critically ill patients.[17,18] Older patients may be underrepresented in clinical trials due to lower consent rates or eligibility (more frequent comorbidities and treatment limitations). Meanwhile, older patients, especially those greater than 80 years old, have increased ICU[19,20] and hospital mortality.[21–26] Emerging literature supports that frailty is common among critically ill patients and is independently associated with less favorable outcomes.[27–29] Furthermore, extubation failure occurs in 34% of patients over 65 years, especially those who have chronic cardiac or respiratory disease.[30] For these reasons, formal evaluation of weaning strategies in older patients is justified and warranted.

In two contemporaneous, multicenter, randomized pilot trials comparing OD versus "at least twice daily" (ALTD) screening in nonelderly LibeRation from MEchanicaL VEntilAtion and ScrEening Frequency [RELEASE] trial, < 65 yr) and elderly (Screening Elderly PatieNts For InclusiOn in a Weaning [SENIOR] trial, ≥ 65 yr) adults, we assessed our ability to recruit younger and older patients (primary objective), adhere to the assigned screening protocols, and obtain preliminary estimates of effect on important clinical outcomes.