Effect of Ventilator Mode on Ventilator-Free Days in Critically Ill Adults: A Randomized Trial

Abstract

Rationale: For critically ill adults receiving invasive mechanical ventilation, the ventilator mode determines how breaths are delivered. Whether the choice of ventilator mode affects outcomes for critically ill patients is unknown. To compare the effects of three common ventilator modes (volume control, pressure control, and adaptive pressure control) on death and duration of mechanical ventilation.

Methods: We conducted a pragmatic, cluster-randomized, crossover trial among adults receiving invasive mechanical ventilation in a medical ICU between November 1, 2022 and July 31, 2023. Each month, patients in the participating unit were assigned to receive volume control, pressure control, or adaptive pressure control during continuous mandatory ventilation. The primary outcome was ventilator-free days through 28 days.

Results: Among 566 patients included in the primary analysis, the median number of ventilator-free days was 23 [IQR, 0-26] in the volume control group, 22 [0-26] in the pressure control group, and 24 [0-26] in the adaptive pressure control group (P=0.60). The median tidal volume was similar in the three groups, but the percentage of breaths larger than 8mL/kg of predicted body weight differed between volume control (median, 4.0%; IQR, 0.0-14.1), pressure control (10.6%; 0.0-31.5), and adaptive pressure control (4.7%; 0.0-19.2). Incidences of hypoxemia, acidemia, and barotrauma were similar in the three groups.

Conclusions: Among critically ill adults receiving invasive mechanical ventilation, the use of volume control, pressure control, or adaptive pressure control did not affect the number of ventilator-free days, however, confidence intervals included differences that may be clinically meaningful.

Keywords: Artificial; Clinical Trial; Critical Illness; Respiration; Respiratory Failure.

Figure 1.

Flow of participants through the trial.

Figure 2.. Ventilator mode received by each group.

Shown are the percentages of ventilator breaths in each trial group that were in volume control mode (red), pressure control mode (yellow), and adaptive pressure control mode (blue) for the 72 hours following enrollment. Ventilator mode was assessed approximately every 1 minute. This figure displays data on breaths for which the patient was receiving a continuous mandatory mode of ventilation. Also shown is the number of patients who were alive and receiving continuous mandatory ventilation in each group during each time interval. The percentage of breaths in a continuous mandatory mode and in a spontaneous mode (e.g., pressure support) were 86.4% and 13.6% on day 1, 78.7% and 21.3% on day 2, and 75.7% and 24.3% on day 3. Ventilator mode is reported for 545 of 566 patients on study day 1. A total of 18 patients did not receive a continuous mandatory mode (i.e., they received only spontaneous modes) on day 1, of whom, 5 received a continuous mandatory mode on study days 2 or 3. Three patients were missing data on the ventilator modes received. Additional data on ventilator modes are in Figures E2–E4 and Table E7 in the online data supplement.

Figure 3.. Proportion of patients alive and not receiving invasive mechanical ventilation.

The proportions of patients who were alive (solid lines) and breathing without invasive mechanical ventilation (dotted lines) during the 28 days after enrollment in each ventilator mode group are shown. In a proportional-odds model, the number of days that patients were alive and free of invasive mechanical ventilation through day 28 did not differ significantly among the three study groups (P=0.60).