General anesthesia with endotracheal intubation bypasses the physiological warming and humidification functions of the upper airway, allowing cold and dry gases to reach the lower respiratory tract. This may impair mucociliary clearance, increase secretion viscosity, promote atelectasis, and contribute to postoperative pulmonary complications (PPCs).
Patients undergoing thoracic surgery, particularly those requiring one-lung ventilation (OLV), are at increased risk for PPCs because of altered ventilation-perfusion matching, reduced functional residual capacity, and impaired secretion clearance. Although respiratory gas humidification is routinely used during anesthesia, evidence regarding the comparative clinical effects of active heated humidification (AHH) and passive heat and moisture exchangers (HMEs) during thoracic surgery remains limited.
This prospective observational cohort study aims to evaluate the association between intraoperative respiratory gas humidification methods and postoperative pulmonary complications and perioperative clinical outcomes in adult patients undergoing elective video-assisted thoracoscopic surgery (VATS).
Patients aged 18 to 75 years
Elective video-assisted thoracoscopic surgery (VATS)
Lung resection requiring general anesthesia
Planned one-lung ventilation
Emergency surgery
Pregnancy
Preoperative mechanical ventilation
Previous enrollment
Adult patients undergoing elective video-assisted thoracoscopic lung resection requiring one-lung ventilation at Marmara University Pendik Training and Research Hospital.
Cohort
Prospective
Active Heated Humidification
DeviceAn active heated humidification system integrated into the anesthesia breathing circuit is used during intraoperative mechanical ventilation to warm and humidify inspired respiratory gases. Device selection and clinical management are determined solely by the attending anesthesiologist according to institutional routine practice. No study-specific intervention or modification of patient care is performed.
Heat and Moisture Exchanger
DeviceA passive heat and moisture exchanger filter is incorporated into the anesthesia breathing circuit during intraoperative mechanical ventilation to conserve heat and moisture from exhaled gases. Device selection is based on routine clinical practice, and no intervention is assigned by the study protocol.
Incidence of Postoperative Pulmonary Complications
Incidence of one or more postoperative pulmonary complications occurring within 7 days after surgery, including atelectasis, pneumonia, secretion retention, bronchoscopy for mucus plugging, prolonged oxygen requirement, requirement for non-invasive or invasive ventilatory support, or reintubation. PPCs will be assessed using predefined clinical and radiological criteria.
Oxygenation (PaO₂/FiO₂ Ratio)
Intraoperative arterial oxygenation assessed by the ratio of arterial oxygen partial pressure (PaO₂) to the fraction of inspired oxygen (FiO₂).
Frequency of Endotracheal Suctioning
Number of endotracheal suctioning procedures performed during the intraoperative period.
Airway Secretion Viscosity Score
Airway secretion viscosity assessed using a semi-quantitative 5-point scale (0 = no secretions, 1 = watery secretions, 2 = mildly viscous secretions, 3 = thick secretions difficult to aspirate, 4 = very thick obstructive secretions). The highest score recorded for each patient will be used for analysis.
Incidence of Intraoperative Hypothermia
Proportion of patients developing intraoperative hypothermia, defined as a core body temperature \<36.0°C.
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