Flow Index Trajectories During Spontaneous Breathing Trials Are Associated With Extubation Failure: A Latent Class Trajectory Modeling Study.

Extubation failure may occur despite a successful spontaneous breathing trial (SBT), suggesting that conventional SBT criteria may not fully capture respiratory reserve. The Flow index (FI), derived from inspiratory flow time waveform morphology, reflects inspiratory effort during pressure support ventilation. We investigated whether FI trajectories during SBT were associated with extubation failure. In this retrospective cohort study, FI values during the final 10 min of SBT were summarized within six prespecified 2 min windows using patient level medians. Latent class trajectory modeling was used to identify FI patterns, followed by clinically and statistically justified consolidation into three trajectory groups. Multivariable logistic regression evaluated the association between FI trajectory and extubation failure. Mean based trajectories and machine learning analyses were performed as exploratory supplementary analyses. Among 432 screened patients, 123 were included, and 27 (22.0%) experienced extubation failure. The consolidated groups were Traj1, stable/moderate reserve (n = 89; failures, 12.4%); Traj2, depleted/low effort (n = 18; failures, 50.0%); and Traj3, escalating/high effort (n = 16; failures, 43.8%). Compared with Traj1, Traj2 (adjusted odds ratio [OR], 8.23; 95% confidence interval [CI], 1.69-39.98; p = 0.009) and Traj3 (adjusted OR, 16.06; 95% CI, 3.02-85.40; p = 0.001) were associated with higher odds of extubation failure after adjustment for age, sex, SOFA score, and dynamic compliance. Median based FI trajectories during SBT identified distinct patterns associated with extubation failure and may provide complementary post SBT risk stratification information. Prospective external validation is required before clinical implementation.