Effect of tension capnothorax on respiratory mechanics and individualized PEEP during robotic-assisted thoracic surgery: a prospective pilot observational study

Abstract

Background: Tension capnothorax during robotic-assisted thoracic surgery (RATS) might promote intraoperative atelectasis, which predisposes to ventilation-induced lung injury (VILI). Lung-protective mechanical ventilation including recruitment maneuver (RM) and individualized positive-end expiratory pressure (iPEEP) minimizes VILI. This study examines the effects of capnothorax on respiratory mechanics (respiratory system compliance, Crs), and the potential differences in the iPEEP before-and-after capnothorax.

Methods: This is a prospective, observational pilot study enrolling patients scheduled for RATS using continuous tension capnothorax. The effects of capnothorax were analyzed with respiratory mechanics and volumetric capnography at different time points. The primary outcome were differences in Crs just before-and-after capnothorax. We also tested the iPEEP before-and-after capnothorax. After a RM, a PEEP titration trial was used to indentify the iPEEP.

Results: A total of 30 patients were included in the analysis. The application of capnothorax significantly impaired respiratory system mechanics, as shown by a decreased in Crs from 40 (7) to 21 (8) mL/cmH<inf>2</inf>O, P<0.001) and an increase in driving pressure (DP) from 8 (3) to 16 (5) cmH<inf>2</inf>O, P<0.001. A non-significantly increase was shown for dead spaces. RM + iPEEP significantly improved Crs from 21 (8) to 43 (8) mL/cmH<inf>2</inf>O and DP from 16 (5) to 8 (2) cmH<inf>2</inf>O (P<0.001). iPEEP before capnothorax was 6 (2) cmH<inf>2</inf>O, which increased to 12 (4) cmH<inf>2</inf>O, P<0.001 after it.

Conclusions: Tension capnothorax during RATS impairs respiratory system mechanics and increases iPEEP requirements to maintain an open-lung condition. Individualized PEEP after CO<inf>2</inf> insufflation restores respiratory system mechanics and alveolar dead space.