Timing of Spontaneous Breathing Trials in Intubated Adults: A Pilot Prospective Observational Study

Introduction: The timing of spontaneous breathing trials (SBT) varies widely across institutions, with no established consensus on the optimal time for conducting them. Thus, this study aimed to evaluate whether the timing of SBT impacts the duration of intubation in adult critically ill patients.


Methods: Approved by the institutional ethics committee (No. 24081701), this pilot prospective observational study was conducted at Rush University Medical Center. Adult patients (≥ 21 years) who received invasive mechanical ventilation for over 48 hours and completed at least one SBT were included. Patients were divided into two groups based on the timing of SBT: the usual time group (7:00 a.m. to 12:00 p.m.) and the unusual time group (any other time). The primary outcome was intubation duration. Secondary outcomes included the interval from the last passed SBT to extubation, SBT attempts, 48-hour reintubation rate, trachostomy, ICU and hospital stays, and hospital mortality. A priori planned subgroup analysis was conducted for planned extubated patients.


Results: Between May 22, 2024, and May 31, 2025, 632 patients were screened and 163 were included. Of these, 86 patients underwent SBTs during the usual time and 77 during the unusual time. The usual time group included more African Americans (58% vs. 32%) and fewer Caucasians (27% vs. 42%). Other baseline characteristics (age, gender, APACHE II score, comorbidities, SBT mode) were comparable between groups. The intubation duration did not significantly differ between groups (102.5 [IQR 72.2–176.0] vs. 86.8 [IQR 67.0–141.6] hours, p=0.127). The secondary outcomes were also similar between groups. Among planned extubated patients (n=120), the extubation rate was 69% in the usual time group and 77% in the unusual time group (p=0.125), with similar outcomes between groups. However, the interval from the last passed SBT to extubation was shorter in the usual time group (1.4 [IQR 0.5–3.5] vs. 3.5 [IQR 0.8–6.4] hours, p=0.048).


Conclusions: Patients who underwent SBTs during the morning hours experienced shorter delays between passing the SBT and extubation compared to those who received SBT at other times. However, no significant differences were observed in intubation duration or other clinical outcomes.