Chronic obstructive pulmonary disease (COPD) is one of the most common comorbidities in acute respiratory distress syndrome (ARDS). Unfortunately, there aren’t many specific studies on the best way to ventilate patients with ARDS and COPD, especially when adjusting the amount of positive end-expiratory pressure (PEEP). Researchers sought to compare the mechanics of breathing in ARDS patients on mechanical ventilation who have or don’t have COPD and to find out if PEEP adjustment based on electrical impedance tomography (EIT) is better than the ARDSnet protocol. This is a single-center, repeated-measures study with one point of view. Patients with ARDS who needed mechanical ventilation and were admitted to an ICU between August 2017 and December 2020 were included. Patients with ARDS were categorized into 2 groups based on whether or not they had COPD. During ventilation, the mechanics of breathing, the exchange of gasses, and the flow of blood were compared between the groups based on whether the PEEP level was set by EIT or the ARDSnet protocol.

A total of 27 ARDS patients were chosen, including 14 with and 13 without COPD, who met the study’s requirements. The COPD group’s PEEP levels were lower than the non-COPD group’s (6.93 ± 1.69 cm H2O vs. 12.15 ± 2.40 cm H2O, P<0.001 and 10.43 ± 1.20 cm H2O vs. 14.0 ± 3.0 cm H2O, P<0.001, respectively). In the COPD group, the PEEP level titrated by EIT was lower than that titrated by the ARDSnet protocol (6.93 ± 1.69 cm H2O vs. 10.43 ± 1.20 cm H2O, P<0.001), as was the global inhomogeneity (GI) index (0.397 ± 0.040 vs. 0.446 ± 0.052, P=0.001), plateau airway pressure (16.50 ± 4.35 cm H2O vs. 20.93 ± 5.37 cm H2O, P=0.001), dead space ventilation ratio (48.29 ± 6.78% vs. 55.14 ± 8.85%, P<0.001), ventilation ratio (1.63 ± 0.33 vs. 1.87 ± 0.33, P<0.001), and mechanical power (13.92 ± 2.18 J/min vs. 15.87 ± 2.53 J/min, P<0.001). The cardiac index was higher when PEEP was treated by EIT than when it was titrated by the ARDSnet protocol (3.41 ± 0.50 L/min/m2 vs. 3.02 ± 0.43 L/min/m2, P<0.001), as was oxygen delivery (466.40 ± 71.08 mL/min/m2 vs. 411.10 ± 69.71 mL/min/m2, P=0.001).

Patients with ARDS and COPD had lower titrated PEEP levels than ARDS patients without COPD. In ARDS patients who also had COPD, the application of PEEP titrated by EIT was lower than that titrated by the ARDSnet protocol. This helped improve the ventilation ratio, mechanical energy, cardiac index, and oxygen delivery while having less of a negative effect on hemodynamics.