Controlling mechanical ventilation in acute respiratory distress syndrome with fuzzy logic

The current ventilatory care goal for acute respiratory distress syndrome (ARDS) and the only evidence-based approach for managing ARDS is to ventilate with a tidal volume (VT) of 6 mL/kg predicted body weight (PBW). However, it is not uncommon for some caregivers to feel inclined to deviate from this strategy for one reason or another. To accommodate this inclination in a rationalized manner, we previously developed an algorithm that allows for VT to depart from 6 mL/kg PBW based on physiological criteria. The goal of the present study was to test the feasibility of this algorithm in a small retrospective study.

Current values of peak airway pressure, positive end-expiratory pressure (PEEP), and arterial oxygen saturation are used in a fuzzy logic algorithm to decide how much VT should differ from 6 mL/kg PBW and how much PEEP should change from its current setting. We retrospectively tested the predictions of the algorithm against 26 cases of decision making in 17 patients with ARDS.

Differences between algorithm and physician VT decisions were within 2.5 mL/kg PBW, except in 1 of 26 cases, and differences between PEEP decisions were within 2.5 cm H2O, except in 3 of 26 cases. The algorithm was consistently more conservative than physicians in changing VT but was slightly less conservative when changing PEEP.

Within the limits imposed by a small retrospective study, we conclude that our fuzzy logic algorithm makes sensible decisions while at the same time keeping practice close to the current ventilatory care goal.