Low tidal volume ventilation use remains low in patients with acute respiratory distress syndrome at a single center

Abstract

Purpose

Low tidal volume ventilation (LTVV) reduces mortality in acute respiratory distress syndrome (ARDS) patients. Understanding local barriers to LTVV use at a former ARDS Network hospital may provide new insight to improve LTVV implementation.

Methods

A cohort of 214 randomly selected adults met the Berlin definition of ARDS at Harborview Medical Center between 2008 and 2012. The primary outcome was the receipt of LTVV (tidal volume of ≤ 6.5 mL/kg predicted body weight) within 48 h of ARDS onset. We constructed a multivariable logistic regression model to identify factors associated with the outcome.

Results

Only 27% of patients received tidal volumes of ≤ 6.5 mL/kg PBW within 48 h of ARDS onset. Increasing plateau pressure (OR 1.11; 95% CI 1.03 to 1.19; p-value < 0.01) was positively associated with LTVV use while increasing PaO₂:F_IO₂ ratio was negatively associated (OR 0.75; 95% CI 0.57 to 0.98; p-value 0.03). Physicians documented an ARDS diagnosis in only 21% of the cohort. Neither patient height nor gender was associated with LTVV use.

Conclusions

Most ARDS patients did not receive LTVV despite implementation of a protocol. ARDS was also recognized in a minority of patients, suggesting an opportunity for improvement of care.

Introduction

Acute respiratory distress syndrome (ARDS) is a common and devastating form of respiratory failure that affects 190,000 patients annually in the United States and has a mortality rate of 39% [1]. Despite 30 years of clinical trials and drug research, only a handful of interventions reduce mortality in ARDS patients [2], [3], [4], [5]. In 2000, the ARDS Network published the results of the landmark randomized controlled trial that demonstrated a 9% absolute reduction in mortality utilizing a low tidal volume ventilation (LTVV) strategy targeting a goal tidal volume ≤ 6 mL (mL) per kilogram (kg) of predicted body weight (PBW) and a goal plateau pressure (P_plat) < 30 cm H₂O [6]. This ventilation strategy is now termed “lung protective ventilation” and has become the standard of care for patients with ARDS. Many studies have confirmed the benefits of LTVV [7], [8], and have suggested a time-dependent mortality benefit from early utilization of LTVV [9]. Emerging evidence also suggests that LTVV may prevent incident ARDS in at-risk, critically ill patients [10], [11], [12].

The adoption of lung protective ventilation strategies in clinical practice has been slow despite convincing evidence of the benefits of LTVV [13], [14], [15], [16], [17], [18]. Studies performed in the initial five years of the ARDS Network trial demonstrated only 40% of ARDS patients received appropriate LTVV therapy [19], [20]. Low rates of compliance with LTVV have prompted further examination of barriers to utilization and several barriers to LTVV use have already been described. Known barriers include mismeasurement or missing height (used to calculate predicted body weight), concern for patient discomfort or perceived need for greater doses of sedating medications despite evidence to the contrary [21], [22], and physician failure to recognize ARDS [13], [19], [23], [24]. Factors associated with higher utilization of LTVV include a written protocol for delivery of appropriate ventilator settings and a closed ICU staffing model [19], [25], both of which have been adopted at our institution.

Our primary aim was to describe patient and physician factors associated with the use of LTVV in patients meeting the Berlin Definition of ARDS [28] at our institution, over ten years since the original trial. We hypothesized that the proportion of ARDS patients who receive LTVV remains low at our academic center, despite significant institutional efforts to increase utilization.