Dale M. Needham, Ting Yang, Victor D. Dinglas, Pedro A. Mendez-Tellez, Carl Shanholtz, Jonathan E. Sevransky, Roy G. Brower, Peter J. Pronovost, and Elizabeth Colantuoni Am. J. Resp. Crit. Care Med. Jan 15, 2015, vol. 191, no. 2: 177-185
Rationale: Reducing tidal volume decreases mortality in acute respiratory distress syndrome (ARDS). However, the effect of the timing of low tidal volume ventilation is not well understood.
Objectives: To evaluate the association of intensive care unit (ICU) mortality with initial tidal volume and with tidal volume change over time.
Methods: Multivariable, time-varying Cox regression analysis of a multisite, prospective study of 482 patients with ARDS with 11,558 twice-daily tidal volume assessments (evaluated in milliliter per kilogram of predicted body weight [PBW]) and daily assessment of other mortality predictors.
Measurements and Main Results: An increase of 1 ml/kg PBW in initial tidal volume was associated with a 23% increase in ICU mortality risk (adjusted hazard ratio, 1.23; 95% confidence interval [CI], 1.06–1.44; P = 0.008). Moreover, a 1 ml/kg PBW increase in subsequent tidal volumes compared with the initial tidal volume was associated with a 15% increase in mortality risk (adjusted hazard ratio, 1.15; 95% CI, 1.02–1.29; P = 0.019). Compared with a prototypical patient receiving 8 days with a tidal volume of 6 ml/kg PBW, the absolute increase in ICU mortality (95% CI) of receiving 10 and 8 ml/kg PBW, respectively, across all 8 days was 7.2% (3.0–13.0%) and 2.7% (1.2–4.6%). In scenarios with variation in tidal volume over the 8-day period, mortality was higher when a larger volume was used earlier.
Conclusions: Higher tidal volumes shortly after ARDS onset were associated with a greater risk of ICU mortality compared with subsequent tidal volumes. Timely recognition of ARDS and adherence to low tidal volume ventilation is important for reducing mortality.
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