Dynamic Changes in Respiratory Frequency/Tidal Volume May Predict Failures of Ventilatory Liberation in Patients on Prolonged Mechanical Ventilation and Normal Preliberation Respiratory Frequency/Tidal Volume Values

Authors

Raeanna C. Adams
Oliver L. Gunter
Jonathan R. Wisler
Melissa L. Whitmill, Wright State UniversityFollow
James Cipolla
David E. Lindsey
Christy Stehly
Steven M. Steinberg
Charles H. Cook
Stanislaw P. Stawicki

Document Type

Article

Publication Date

1-2012

Abstract

Rapid shallow breathing index (RSBI, respiratory frequency [f] divided by tidal volume [Vt]) has been used to prognosticate liberation from mechanical ventilation (LMV). We hypothesize that dynamic changes in RSBI predict failed LMV better than isolated RSBI measurements. We conducted a retrospective study of patients who were mechanically ventilated (MV) for longer than 72 hours. Failed LMV was defined as need for reinstitution of MV within 48 hours post-LMV. Ventilatory frequency (f) and Vt (liters) were serially recorded. The instantaneous RSBI (i-RSBI) was defined as f/Vt. Dynamic f/Vt ratio (d-RSBI) was defined as the ratio between two consecutive i-RSBI (f/Vt) measurements ([f₂/Vt₂]/[f₁/Vt₁]). RSBI Product (RSB-P) was defined as (i-RSBI × d-RSBI). Data from 32 patients were analyzed (Acute Physiology and Chronic Health Evaluation II 13.4, male 69%, mean age 57 years). Mean length of stay was 19.5 days (11.5 ventilator; 14.1 intensive care unit days). For LMV failures, mean time to reinstitution of invasive MV was 20.8 hours. All patients had pre-LMV i-RSBI less than 100. Failed LMVs had higher i-RSBI values (68.9, n = 18) than successful LMVs (44.2, n = 23, P < 0.01). Failures had higher d-RSBI (1.48) than successful LMVs (1.05, P < 0.04). The RSB-P was higher for failed LMVs (118) than for successful LMVs (48.8, P < 0.01) with failures having larger proportion of pre-LMV d-RSBI values greater than 1.5 (39.0 vs 10.7%, P < 0.03). Pre-LMV RSB-P may offer early prediction of failed LMV in patients on MV for longer than 72 hours despite normal pre-LMV i-RSBI. Divergence between RSB-P for successful and failed LMVs occurred earlier than i-RSBI divergence with a greater proportion of pre-LMV d-RSBI greater than 1.5 among failures.

Repository Citation

Adams, R. C., Gunter, O. L., Wisler, J. R., Whitmill, M. L., Cipolla, J., Lindsey, D. E., Stehly, C., Steinberg, S. M., Cook, C. H., & Stawicki, S. P. (2012). Dynamic Changes in Respiratory Frequency/Tidal Volume May Predict Failures of Ventilatory Liberation in Patients on Prolonged Mechanical Ventilation and Normal Preliberation Respiratory Frequency/Tidal Volume Values. The American Surgeon, 78 (1), 69-73.
https://corescholar.libraries.wright.edu/surg/481