Effects of Automated Versus Conventional Ventilation on Quality of Oxygenation-A Substudy of a Randomized Crossover Clinical Trial

Abstract

Background/Objectives: Attaining adequate oxygenation in critically ill patients undergoing invasive ventilation necessitates intense monitoring through pulse oximetry (SpO₂) and frequent manual adjustments of ventilator settings like the fraction of inspired oxygen (FiO₂) and the level of positive end-expiratory pressure (PEEP). Our aim was to compare the quality of oxygenation with the use of automated ventilation provided by INTELLiVENT-Adaptive Support Ventilation (ASV) vs. ventilation that is not automated, i.e., conventional pressure-controlled or pressure support ventilation. Methods: A substudy within a randomized crossover clinical trial in critically ill patients under invasive ventilation. The primary endpoint was the percentage of breaths in an optimal oxygenation zone, defined by predetermined levels of SpO₂, FiO₂, and PEEP. Secondary endpoints were the percentage of breaths in acceptable or critical oxygenation zones, the percentage of time spent in optimal, acceptable, and critical oxygenation zones, the number of manual interventions at the ventilator, and the number and duration of ventilator alarms related to oxygenation. Results: Of the 96 patients included in the parent study, 53 were eligible for this current subanalysis. Among them, 31 patients were randomized to start with automated ventilation, while 22 patients began with conventional ventilation. No significant differences were found in the percentage of breaths within the optimal zone between the two ventilation modes (median percentage of breaths during automated ventilation 19.4 [0.1-99.9]% vs. 25.3 [0.0-100.0]%; p = 0.963). Similarly, there were no differences in the percentage of breaths within the acceptable and critical zones, nor in the time spent in the three predefined oxygenation zones. Although the number of manual interventions was lower with automated ventilation, the number and duration of ventilator alarms were fewer with conventional ventilation. Conclusions: The quality of oxygenation with automated ventilation is not different from that with conventional ventilation. However, while automated ventilation comes with fewer manual interventions at the ventilator, it also comes with more ventilator alarms.

Keywords: automated ventilation; closed-loop ventilation; fraction of oxygen; intensive care; invasive ventilation; manual interventions; oxygenation; positive end-expiratory pressure; ventilator alarms; ventilator settings.

Figure 1

CONSORT flow diagram.

Figure 2

Cumulative distribution plots for SpO₂, PEEP, and FiO₂. The plots show the median variables with automated ventilation (light blue) and conventional ventilation (purple). Horizontal dotted lines represent 50% of the patients and vertical dotted lines represent median values for the conventional group. Abbreviations: SpO₂, pulse oximetry; PEEP, positive end-expiratory pressure; FiO₂, fraction of inspired oxygen.

Figure 3

Proportions of breaths in predefined zones of oxygenation. Percentages of breaths in the predefined zones are shown in bar plots, wherein the mean percentages of breath in the optimal, acceptable, and critical zones per crossover phase are shown for the oxygenation zones and for SpO₂ and PEEP/FiO₂ zones separately.