Serial measurements of f/VT can predict extubation failure in patients with f/VT ≤ 105?

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To evaluate is serial measurements of respiratory rate (frequency to tidal volume, f/VT) may predict extubation failure (EF) from mechanical ventilation in patients following a successful spontaneous breathing trial (SBT) with first measurement of f/VT ≤ 105.


Prospective cohort study.


Two medical-surgical intensive care units.


Seventy-three patients ventilated for more than 48 hours after successful SBT were extubated and followed up for postextubation respiratory distress during 48 hours.


Extubation failure occurred in 16 (21.9%) of 73 patients. Factors such as age, sex, Apache II score, days on mechanical ventilation, respiratory failure cause, and hemodynamic or ventilatory parameters did not predict EF. Patients were evaluated during 120 minutes of SBT, and f/VT was measured at the 1st minute (f/VT−1), 30th minute (f/VT−30), and 120th minute (f/VT−120). The f/VT−30 increased as compared with f/VT−1 (79 ± 24 vs 68 ± 30, P = .01) but did not differ from f/VT−120 (79 ± 44 vs 81 ± 42, P = .79). The f/VT−1 was lower in successful extubation (ES) as compared with EF patients (62 ± 29 vs 82 ± 15, P = .01), and this difference was unchanged during the trial (f/VT−30: ES [63 ± 22] vs EF [85 ± 24], P = .02; and f/VT−120: ES [65 ± 26] vs EF [88 ± 20], P = .01)].


Serial f/VT measurements during 120 minutes of SBT were unable to detect EF in patients following a successful SBT with initial f/VT lower than 105.

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