Contemporary ventilator management in patients with and at risk of ALI/ARDS

Abstract

Background: Ventilator practices in patients at risk for acute lung injury (ALI) and ARDS are unclear. We examined factors associated with choice of set tidal volumes (VT), and whether VT < 8 mL/kg predicted body weight (PBW) relates to the development of ALI/ARDS.

Methods: We performed a secondary analysis of a multicenter cohort of adult subjects at risk of lung injury with and without ALI/ARDS at onset of invasive ventilation. Descriptive statistics were used to describe ventilator practices in specific settings and ALI/ARDS risk groups. Logistic regression analysis was used to determine the factors associated with the use of VT < 8 mL/kg PBW and the relationship of VT to ALI/ARDS development and outcome.

Results: Of 829 mechanically ventilated patients, 107 met the criteria for ALI/ARDS at time of intubation, and 161 developed ALI/ARDS after intubation (post-intubation ALI/ARDS). There was significant intercenter variability in initial ventilator settings, and in the incidence of ALI/ARDS and post-intubation ALI/ARDS. The median VT was 7.96 (IQR 7.14-8.94) mL/kg PBW in ALI/ARDS subjects, and 8.45 (IQR 7.50-9.55) mL/kg PBW in subjects without ALI/ARDS (P = .004). VT decreased from 8.40 (IQR 7.38-9.37) mL/kg PBW to 7.97 (IQR 6.90-9.23) mL/kg PBW (P < .001) in those developing post-intubation ALI/ARDS. Among subjects without ALI/ARDS, VT ≥ 8 mL/kg PBW was associated with shorter height and higher body mass index, while subjects with pneumonia were less likely to get ≥ 8 mL/kg PBW. Initial VT ≥ 8 mL/kg PBW was not associated with the post-intubation ALI/ARDS (adjusted odds ratio 1.30, 95% CI 0.74-2.29) or worse outcomes. Post-intubation ALI/ARDS subjects had mortality similar to subjects intubated with ALI/ARDS.

Conclusions: Clinicians seem to respond to ALI/ARDS with lower initial VT. Initial VT, however, was not associated with the development of post-intubation ALI/ARDS or other outcomes.

Trial registration: ClinicalTrials.gov NCT00889772.

Keywords: ARDS; acute lung injury; mechanical ventilation; mortality; tidal volume.

Conflict of interest statement

The other authors have disclosed no conflicts of interest.

Figures

Figure 1

Flow chart of screening and case assessment. LIPS = Lung Injury Prevention Study. ALI = acute lung injury.

Figure 2

Intercenter variation in rate of subjects intubated for acute lung injury (ALI)/ARDS (n = 107) and developing post-intubation ALI/ARDS (n = 161).

Figure 3

Intercenter variation in initial tidal volume (VT) settings among all intubated and mechanically ventilated subjects (n = 829), subjects who never developed ALI/ARDS (n = 561), subjects intubated because of ALI/ARDS (n = 107), and subjects with post-intubation ALI/ARDS (n = 161). The horizontal lines represent the medians, the tops and bottoms of the boxes represent quintiles 1 and 3, and the whisker bars represent the upper and lower limits. For all the comparisons, P via analysis of variance is < .003.