Biologic Impact of Mechanical Power at High and Low Tidal Volumes in Experimental Mild Acute Respiratory Distress Syndrome

Methods: Forty Wistar rats received Escherichia coli lipopolysaccharide intratracheally. After 24 h, 32 rats were randomly assigned to be mechanically ventilated (2 h) with a combination of different V_T (6 ml/kg and 11 ml/kg) and RR that resulted in low and high power. Power was calculated as energy (ΔP,_L²/E,_L) × RR (ΔP,_L = transpulmonary driving pressure; E,_L = lung elastance), and was threefold higher in high than in low power groups. Eight rats were not mechanically ventilated and used for molecular biology analysis.

Results: Diffuse alveolar damage score, which represents the severity of edema, atelectasis, and overdistension, was increased in high V_T compared to low V_T, in both low (low V_T: 11 [9 to 14], high V_T: 18 [15 to 20]) and high (low V_T: 19 [16 to 25], high V_T: 29 [27 to 30]) power groups. At high V_T, interleukin-6 and amphiregulin expressions were higher in high-power than in low-power groups. At high power, amphiregulin and club cell protein 16 expressions were higher in high V_T than in low V_T. Mechanical energy and power correlated well with diffuse alveolar damage score and interleukin-6, amphiregulin, and club cell protein 16 expression.

Conclusions: In experimental mild ARDS, even at low V_T, high mechanical power promoted ventilator-induced lung injury. To minimize ventilator-induced lung injury, low V_T should be combined with low power.