Disparities in Lung-Protective Ventilation in the United States

Abstract

Background The objective of our study was to determine whether disparities exist in the use of lung-protective ventilation for critically ill mechanically ventilated patients in the United States based on gender, race/ethnicity, or insurance status. Methods This was a secondary data analysis of a prospective multicenter cohort study conducted from 2010 to 2012. The outcome of interest was the proportion of patients receiving tidal volume > 8 mL/kg predicted body weight (PBW). Results There were 1,595 patients in our primary analysis (710 women, 885 men). Women were more likely to receive tidal volumes > 8 mL/kg PBW than men (odds ratio [OR] = 3.42, 95% confidence interval [CI] = 2.67-4.40), a finding largely but not completely explained by gender differences in height. The underinsured were significantly more likely to receive tidal volume > 8 mL/kg PBW than the insured in multivariable analysis (OR = 1.54, 95% CI = 1.16-2.04). The prescription of > 8 mL/kg PBW tidal volume did not differ by racial or ethnic categories. Conclusions In this prospective nationwide cohort of critically ill mechanically ventilated patients, women and the underinsured were less likely than their comparators to receive lung-protective ventilation, with no apparent differences based on race/ethnicity alone.

Keywords: critical care; insurance coverage; lung injury; mechanical ventilation; respiratory failure; sex; tidal volume.

Figure 1. Derivation of the study sample.

Figure 2. Tidal volume parameters in men vs women

(A) Unadjusted tidal volume in men vs women, (B) Tidal volume adjusted for predicted body weight in men vs women. (C) Percentage of men vs women receiving tidal volume > 8 mL/kg predicted body weight. Dot plots show distributions of values, with the median value indicated by the horizontal line. Comparisons were analyzed using the rank-sum test or chi-square test.

Figure 3. Directed acyclic graphs modeling hypothesized relationships between exposures (ovals) and outcome of interest (rectangles with white background)

Proposed causal pathways are diagramed in thick solid arrows. Potential confounders are diagramed in shaded rectangles. Relationships between potential confounders and other variables are diagramed as thin arrows. Positive relationships between potential confounders and other variables are those that increase the probability of the other variable, designated by thin solid arrows. Negative relationships between potential confounders and other variables are those that decrease the probability of the other variable, designated by thin dashed arrows. Mediators are designated by black triangles. A. Theorized causal association diagram between female gender (exposure) and higher tidal volume (outcome). There are two possible causal pathways diagramed: one that includes shorter height as a mediator (the indirect path) and one goes directly from female gender to higher tidal volume (the direct path). Medical comorbidities and older age are diagramed as possible confounders of the relationship between height (mediator) and tidal volume (outcome). B. Theorized causal association diagram between underinsurance (exposure) and higher tidal volume (outcome). Minority race/ethnicity and more comorbidities are diagramed as potential confounders sharing positive associations with both the exposure and the outcome. Older age and elective surgery are diagramed as confounders sharing negative associations with underinsurance but positive associations with higher tidal volume. C. Theorized causal association diagram between minority race/ethnicity (exposure) and higher tidal volume (outcome). Underinsurance, more comorbidities, and female gender are diagramed as potential confounders sharing positive associations with the exposure and outcome.