Anesthetic effects, surgery, and invasive mechanical intubation can impair respiratory function during general anesthesia. The risk factors for postoperative pulmonary complications (PPCs) include the type of surgery and duration, ventilation-perfusion discrepancy, and the presence of pain. Mitigating PPCs under anesthesia is a goal, but effective strategies are yet to be defined. Conventional ventilation (CV) procedure uses more inspired oxygen during pre-oxygenation and anesthesia maintenance. The protective lung ventilation (PV) procedure, on the other hand, includes high positive end-expiratory pressure, lung recruitment maneuver, oxygen saturation levels above 94%, lower inspired oxygen levels, and continuous positive airway pressure before the tube is removed. In this study, 56 consecutive patients undergoing abdominal surgery were randomly assigned, with 30 in the CV and 23 in the PV group, while 3 were lost during the follow-up. We concluded that the implementation of protective lung ventilation strategies has the potential to reduce the occurrence of PPCs, recommending these strategies be adopted as the standard practice in general anesthesia.

Additionally, despite accumulated knowledge and careful monitoring, sometimes an anesthesiologist is still unable to entirely avoid the occurrence of atelectasis, a common phenomenon observed during general anesthesia. Altogether, it can be concluded that the effects of mechanical ventilation and oxygenation over an extended period are not yet well understood, particularly regarding the impact of reducing tidal volume and using higher PEEPs. This study was a prospective, single-center, randomized controlled, patient- and evaluator-blinded clinical investigation with a two-arm parallel design to assess the advantage of the protective (optimized) ventilation procedure (PV group of patients) compared to the conventional (standard) method of lung ventilation (CV) during general anesthesia.

Inclusion Criteria:

• the inclusion criteria were as follows:
• subject status according to the American Society of Anesthesiologists Association classification
• ASA 1 (normal healthy patients, i.e. patients without associated comorbidities) or ASA 2 (patients with mild systemic disease, such as well-controlled hypertension), normal heart and lung function, both sexes,
• non-smokers, normal X-ray findings for heart and lungs,
• age 18-65 years,
• planned operation of medial laparotomy for colorectal cancer with a minimum duration of anesthesia of at least one hour,
• signed informed consent.
• In the case of hypertension in ASA 2 patients enrolled in the study, by examining the self-monitoring diary for the past three months (as described in Gropper et al., 2019), there was no increase in systolic pressure more than 20 mmHg from the average daily value and no increase in diastolic arterial pressure more than 10 mmHg from the average daily value.
• In the case of diabetes type II in ASA 2 patients enrolled in the study, the HbA1c values were not higher than 7% while taking oral hypoglycemic drugs and having a regulated diet. The patients enrolled also had no complications or episodes of hypoglycemia in the past three months, as described by Gropper et al., 2019.
• In the case of thyroid disease in ASA 2 patients enrolled in the study, values of TSH, fT3, and fT4 in the period up to 6 months since the last examination were normal.

Exclusion Criteria:

• ASA 4 status
• terminal renal illness
• cardiac status NYHA III i NYHA IV
• at home oxygenotherapy during 16 hours