Measurement of a Baseline Minute Ventilation for the Calculation of Minute Ventilation Recovery Time: Is a Subjective Method Reliable?

BACKGROUND: Minute ventilation recovery time is a new predictor of extubation outcome that uses a subjective method for the determination of baseline minute ventilation (V̇_E) during its measurement. The purpose of the current study is to evaluate the inter-rater reliability of this subjective method for determining baseline V̇_E.

METHODS: Three critical-care physicians served as independent readers. Each was trained with 5 practice V̇_E trends, using the published method for determining baseline V̇_E, defined as the lowest, stable nadir lasting 15–30 min prior to the final weaning trial before extubation. Readers then determined baseline V̇_E prospectively from an 8-hour V̇_E trend for 19 patients who were weaning from mechanical ventilation in the surgical intensive care unit of a tertiary care hospital. Each V̇_E trend was an objective recording of V̇_E every 15 min for 8 hours, immediately prior to the final weaning trial before extubation.

RESULTS: There was excellent inter-rater reliability between trained readers for determination of a subjective V̇_E baseline. Baseline V̇_E was within 1 L/min for 15/19 patients (79%). Intra-class correlation across the 3 readers was 0.92 (p < 0.01). Tukey's test revealed no significant variability between readers (p > 0.5), and Spearman correlations between all reader pairs were significant (p < 0.01).

CONCLUSION: After minimal training, readers can reliably determine a subjective baseline V̇_E. This study validates the original methodology for determining baseline V̇_E, an essential step in the measurement of minute ventilation recovery time.