Optimal Positive End-Expiratory Pressure in Robotic-Assisted Thoracic Surgery

Minimally invasive thoracic surgery is increasingly popular. Recently, a new minimally invasive thoracic approach, robotic-assisted thoracic surgery (RATS) has been developed. RATS presents some advantages compared to VATS such as three-dimensional view of the surgical field, its precisions facilitates the navigation in difficult to access spaces and eliminates tremor which reduces learning curve and it may have a reduction of complications. During RATS and differently from VATS, not only one lung ventilation (OLV) is needed but also a continuous tension capnothorax. CO2 insufflation with intrathoracic positive pressure has a potential negative impact on the cardiorespiratory physiology. Moreover, CO2 insufflation and one lung ventilation can produce ventilation induced lung injury which are related to pulmonary postoperative complications (PPC). In order to reduce PPC and ventilation induced lung injury, lung protective strategies are used which reduce atelectrauma and overdistension. These strategies consist of three main pillars: use of low tidal volumes, performance of recruitment maneuvers and application of optimal positive end-expiratory pressure (PEEP). However, optimal PEEP levels and actual effects of PEEP are not clear. Several clinical studies with one-lung ventilation have reported improved oxygenation and ventilation when an alveolar recruitment maneuver is performed with a standardized PEEP of 5 to 10 cm·H2O. Nevertheless, other studies observe during one-lung ventilation improvements in oxygenation and lung mechanics with individualized PEEP determined by using a PEEP decrement titration trial after an alveolar recruitment maneuver. The effect of a tension capnothorax during RATS may modify pulmonary compliance and optimal PEEP may be different from patients having VATS resection. Even though both methods are habitual in the clinical practice, there are no studies of the effect of an alveolar recruitment maneuver with individualized PEEP during o