Clinical Effects of Intraoperative Heat and Moisture Exchange Systems During Thoracic Surgery: A Prospective Observational Cohort Study

Clinical Effects of Active Versus Passive Intraoperative Respiratory Gas Humidification During Video-Assisted Thoracoscopic Surgery: A Prospective Single-Center Observational Cohort Study

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).

Study Overview

• Status: Recruiting
• Conditions: Postoperative Complications; Video Assisted Thoracic Surgery (VATS); Pulmonary Complications in Surgical Patients; Humidification; Air Conditioning
• Intervention / Treatment: Device: Active Heated Humidification; Device: Heat and Moisture Exchanger

Detailed Description

The physiological conditioning of inspired gases is bypassed during general anesthesia with endotracheal intubation. Delivery of inadequately heated and humidified gases to the lower respiratory tract may impair mucociliary function, increase secretion viscosity, reduce airway patency, and promote postoperative pulmonary complications.

Patients undergoing video-assisted thoracoscopic surgery (VATS) frequently require one-lung ventilation, which further increases susceptibility to pulmonary complications through ventilation-perfusion mismatch, impaired secretion clearance, and atelectasis formation.

Two principal approaches are used for intraoperative respiratory gas conditioning:

Passive heat and moisture exchangers (HMEs) Active heated humidification systems (AHHs) Although HMEs are widely used because of their simplicity, they may provide insufficient humidification during prolonged procedures, high minute ventilation, or one-lung ventilation. Active heated humidifiers deliver gases closer to physiological conditions (approximately 37°C and 100% relative humidity), potentially reducing secretion viscosity and improving airway patency.

Most existing studies evaluating respiratory gas humidification have focused on intensive care patients receiving prolonged mechanical ventilation. Evidence regarding thoracic surgical patients remains limited, particularly during one-lung ventilation.

This prospective, single-center observational cohort study will compare perioperative outcomes among patients managed with active or passive humidification according to routine anesthetic practice. No intervention or randomization will be performed.

• Study Type: Observational
• Enrollment (Estimated): 200

Contacts and Locations

• Study Contact: Name: Seniyye Ülgen Zengin, Associate Professor, MD; Phone Number: +905057142443; Email: ulgen_t@yahoo.com
• Study Contact Backup: Name: Nezaket Nur Arslan Kömür, MD; Phone Number: +905392911654; Email: nnurarslan@gmail.com

Study Locations

• Turkey (Türkiye)
  • Istanbul
    • Istanbul, Istanbul, Turkey (Türkiye), 34722
      • Recruiting
      • Marmara University
      • Contact: Seniyye Ülgen Zengin, Associate Professor, MD; Phone Number: +905057142443; Email: ulgen_t@yahoo.com
      • Principal Investigator: Seniyye Ülgen Zengin, Associate Professor, MD
      • Sub-Investigator: Meliha Orhon Ergün, Associate Professor, MD
      • Contact: Nezaket Nur Arslan Kömür, MD; Phone Number: +905392911654; Email: nnurarslan@gmail.com
      • Sub-Investigator: Nezaket Nur Arslan Kömür, MD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Adult patients undergoing elective video-assisted thoracoscopic lung resection requiring one-lung ventilation at Marmara University Pendik Training and Research Hospital.

Description

Inclusion Criteria:

• Patients aged 18 to 75 years
• Elective video-assisted thoracoscopic surgery (VATS)
• Lung resection requiring general anesthesia
• Planned one-lung ventilation
• Written informed consent

Exclusion Criteria:

• Emergency surgery
• Pregnancy
• Preoperative mechanical ventilation
• Previous enrollment
• Refusal to participate

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Active Heated Humidification (AHH); Patients receiving active heated respiratory gas humidification during intraoperative mechanical ventilation according to routine clinical practice.	Device: Active Heated Humidification; An 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 (HME); Patients receiving passive heat and moisture exchanger filters during intraoperative mechanical ventilation according to routine clinical practice.	Device: Heat and Moisture Exchanger; A 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
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.	From completion of surgery through postoperative Day 7.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Oxygenation (PaO₂/FiO₂ Ratio)	Intraoperative arterial oxygenation assessed by the ratio of arterial oxygen partial pressure (PaO₂) to the fraction of inspired oxygen (FiO₂).	Measured during one-lung ventilation and at the end of surgery.
Frequency of Endotracheal Suctioning	Number of endotracheal suctioning procedures performed during the intraoperative period.	From induction of anesthesia until completion of surgery.
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.	During one-lung ventilation, at the end of one-lung ventilation, and within 24 hours after extubation.
Incidence of Intraoperative Hypothermia	Proportion of patients developing intraoperative hypothermia, defined as a core body temperature <36.0°C.	From induction of anesthesia until completion of surgery.
Incidence of Postoperative Hypothermia	Proportion of patients with body temperature <36.0°C during postoperative monitoring.	Within the first 24 hours after surgery.
Postoperative Oxygen Therapy Requirement	Requirement for supplemental oxygen after surgery.	Within the first 72 hours after surgery.
Requirement for Non-invasive Ventilation	Requirement for postoperative non-invasive ventilatory support.	Within the first 72 hours after surgery.
Intensive Care Unit Length of Stay	Duration of admission to the intensive care unit.	From ICU admission until ICU discharge, up to postoperative Day 30.
Hospital Length of Stay	Length of hospitalization measured from the date of surgery until hospital discharge.	From surgery until hospital discharge, up to postoperative Day 30.
Bronchodilator Therapy Requirement	Proportion of patients requiring bronchodilator treatment during the postoperative period.	Within 7 days after surgery.
C-Reactive Protein (CRP)	Serum C-reactive protein concentration as a marker of postoperative inflammatory response.	Postoperative Day 7.

Collaborators and Investigators

• Sponsor: Marmara University
• Investigators: Study Director: Meliha Orhon Ergün, Associate Professor, MD, Marmara University; Study Chair: Nezaket Nur Arslan Kömür, MD, Marmara University; Principal Investigator: Seniyye Ülgen Zengin, Associate Professor, Marmara University

Study record dates

Study Major Dates

• Study Start (Estimated): July 25, 2026
• Primary Completion (Estimated): April 1, 2027
• Study Completion (Estimated): April 1, 2027

Study Registration Dates

• First Submitted: July 22, 2026
• First Submitted That Met QC Criteria: July 22, 2026
• First Posted (Actual): July 27, 2026

Study Record Updates

• Last Update Posted (Actual): July 27, 2026
• Last Update Submitted That Met QC Criteria: July 22, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Postoperative complications; Thoracic Surgery; VATS; Humidification; One-Lung Ventilation; HME; Pulmonary Complications; Heat and Moisture Exchanger; Air Conditioning
• Additional Relevant MeSH Terms: Pathologic Processes; Pathological Conditions, Signs and Symptoms; Postoperative Complications
• Other Study ID Numbers: 09.2026.26-0220

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data (IPD) will not be shared. The study involves clinical information collected under institutional ethical approval, and no consent was obtained for external sharing of identifiable or de-identified participant-level data.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: Yes