Comparison of the effect of volume controlled ventilation versus pressure controlled ventilation-volume guaranteed on postoperative pulmonary complications in emergency laparotomy : A Randomized Controlled Trial

The term postoperative pulmonary complication (PPC) encompasses almost any complication affecting the respiratory system after anaesthesia and surgery. Emergency laparotomy surgery is a high-risk surgical procedure performed to address acute abdominal conditions, such as perforated bowel, abdominal trauma, and abdominal sepsis. While this intervention is often life-saving, it carries a significant risk of postoperative pulmonary complications (PPCs) that can lead to prolonged hospital stays, increased healthcare costs, and elevated mortality rates. Immediate changes in the respiratory system become apparent upon the induction of general anesthesia. These alterations include shifts in respiratory drive and muscle function, a reduction in lung volumes, and the occurrence of atelectasis in more than 75% of patients who are administered neuromuscular blocking drugs.

PPCs are important causes of mortality after major noncardiac surgeries, and they adversely affect several aspects of morbidity, including hospital stay and unexpected ICU admissions. Their incidence is reported in a wide range (2.8-40%) depending mostly on the represented patient population and PPC definitions. Even though no single universal definition exists, there is a widespread consensus about the involvement of the following in its description: respiratory infection, respiratory failure, bronchospasm, atelectasis, pleural effusion, pneumothorax, or aspiration pneumonitis while others add pulmonary oedema and tracheal reintubation as well. In 2015, a European joint task force published guidelines for perioperative clinical outcome (EPCO) definitions.

High PEEP with recruitment maneuvers during low tidal volume ventilation in patients undergoing major surgery did not reduce postoperative pulmonary complications. Volume controlled ventilation (VCV) delivers a constant preset tidal volume, and airway pressure depends on pulmonary compliance. Pressure controlled ventilation (PCV) provides a constant preset tidal volume with decelerating flow, reducing peak airway pressures (Ppeak). Pressure controlled ventilation-volume guaranteed (PCV-VG), similar to PCV, uses decelerating flow and adjusts inspiratory pressure to achieve the set tidal volume based on measured dynamic compliance (Cdyn) at each breath. Pressure Controlled Ventilation-Volume Guaranteed (PCV-VG) mode of ventilation is found to have improved respiratory mechanics and oxygenation at lower peak inspiratory pressures in laparoscopic surgeries. The combination of PCV-VG and individualized PEEP, determined by static pulmonary compliance-directed titration, reduced inflammatory responses and lung injury markers and helped prevent atelectasis and hypoventilation in patients undergoing laparoscopic surgery in the Trendelenburg position. PCV-VG provided advantages such as lower peak airway pressure, plateau pressure, and higher dynamic airway compliance during two-lung ventilation as compared to volume controlled ventilation (VCV) in patients undergoing major elective non-cardiac surgery under general anesthesia. PCV-VG led to improved patient oxygenation, significantly lower peak airway pressure (Ppeak) and plateau pressure, and slightly lower mean airway pressure (Pmean) during one-lung ventilation (OLV) in thoracic surgery.

Lower peak airway pressures may lead to less barotrauma and volutrauma and reduced inflammatory responses which lead to postoperative pulmonary complications (PPC).

No significant studies focusing on the PCV-VG ventilation mode in emergency surgeries are there. With its various advantages over VCV ventilation mode, it would be beneficial to study the PCV-VG ventilation mode in emergency settings.

We hypothesized that the incidence of postoperative pulmonary complications (POPC) will be less with Pressure Controlled Ventilation-Volume Guaranteed (PCV-VG) over Volume Controlled Ventilation (VCV) in adult patients undergoing emergency laparotomy surgery.

The primary objective of the study is to assess whether PCV-VG ventilation has a lesser incidence of POPC up to 7 days of surgery over a VCV ventilation.