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

Minimally invasive thoracic surgery is increasingly popular thanks to its potential benefits, including less pain, reduced surgical stress and systemic inflammatory response and reduced length of stay. In fact, video-assisted thoracoscopic surgery (VATS), is recommended for lung resection in early stages in ERAS Guidelines. Recently, a new minimally invasive thoracic approach, robotic-assisted thoracic surgery (RATS) has been developed. Its main indications are lung resection, diaphragmatic repair, esophagectomy and resection of mediastinal tumor. 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, it improves work ergonomics 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. Intrathoracic CO2 insufflation aims both to retract tissues and expand the surgical field which gives a better view of intrathoracic structures but also to facilitate anatomical dissection. Nevertheless, CO2 insufflation with intrathoracic positive pressure has a potential negative impact on the cardiorespiratory physiology: it may increase respiratory airway pressure, it may cause hypercapnia and respiratory acidosis and can compromise the hemodynamics induced by the compression of the mediastinal vessels. 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 one-lung ventilation in Robotic-Assisted Thoracic Surgery (RATS). The investigators hypothesized that such a procedure would improve oxygenation and lung mechanics during one-lung ventilation in RATS compared with the establishment of a standardized PEEP. The investigators perform a descriptive observational prospective study to test this hypothesis.