General Anesthesia, Lumbar Disc Herniation, Prone Position, Spinal Surgery
Conditions
Keywords
PEEP, Driving Pressure, Mechanical Power, PCV-VG Ventilation, Prone Position, Lung Protective Ventilation
Brief summary
This randomized controlled clinical trial aims to compare the effects of two different positive end-expiratory pressure (PEEP) levels (5 cmH₂O and 8 cmH₂O) on respiratory mechanics in patients undergoing lumbar spine surgery in the prone position under total intravenous anesthesia (TIVA). Prone positioning may adversely affect lung compliance and gas exchange, making optimal ventilatory strategies essential. Driving pressure and mechanical power are considered key determinants of ventilator-induced lung stress. This study will evaluate the impact of different PEEP levels on respiratory parameters and intraoperative physiological changes.
Detailed description
Prone positioning during lumbar spine surgery is associated with increased intrathoracic pressure, reduced lung compliance, and impaired ventilation-perfusion matching, which may negatively affect respiratory mechanics and gas exchange. Mechanical ventilation strategies, particularly the application of positive end-expiratory pressure (PEEP), play a critical role in preventing atelectasis and optimizing oxygenation. Pressure-controlled ventilation with volume guarantee (PCV-VG) is a modern ventilation mode that ensures target tidal volume delivery while minimizing airway pressures, thereby reducing the risk of ventilator-induced lung injury. In recent years, driving pressure (ΔP) and mechanical power have emerged as important parameters reflecting lung stress and injury during mechanical ventilation. This prospective randomized controlled trial aims to evaluate the effects of two different PEEP levels (5 cmH₂O and 8 cmH₂O) on respiratory mechanics and gas exchange in patients undergoing lumbar spine surgery in the prone position under total intravenous anesthesia (TIVA). Patients will be randomly assigned into two groups receiving either 5 cmH₂O or 8 cmH₂O PEEP. Ventilation will be standardized using PCV-VG mode with a tidal volume of 6-8 mL/kg predicted body weight and respiratory rate adjusted to maintain normocapnia. Hemodynamic parameters and respiratory variables, including peak airway pressure, plateau pressure, dynamic compliance, airway resistance, tidal volume, and end-tidal CO₂, will be recorded at predefined time points. Arterial blood gas analyses will be performed at selected intervals to assess gas exchange. The primary outcome of the study is driving pressure (ΔP), while secondary outcomes include mechanical power, oxygenation parameters, PaCO₂-EtCO₂ gradient, and physiologic dead space fraction (VD/VT). The findings of this study are expected to provide clinical evidence regarding the optimal PEEP level in prone lumbar surgery and contribute to improving intraoperative lung-protective ventilation strategies.
Interventions
DEVICEMechanical Ventilation (PEEP)
Mechanical ventilation will be applied using pressure-controlled ventilation with volume guarantee (PCV-VG) mode during prone lumbar surgery under total intravenous anesthesia (TIVA). Two different positive end-expiratory pressure (PEEP) levels (5 cmH₂O and 8 cmH₂O) will be used according to group allocation. Tidal volume will be set at 6-8 mL/kg predicted body weight, and respiratory rate will be adjusted to maintain normocapnia (EtCO₂ 35-40 mmHg).
Sponsors
Harran University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE
Masking description
This is an open-label study. Due to the nature of the intervention (ventilator settings), masking of care providers and investigators is not feasible.
Intervention model description
Participants will be randomly assigned to one of two groups receiving either 5 cmH₂O or 8 cmH₂O PEEP during mechanical ventilation in prone lumbar surgery.
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
No
Inclusion criteria
* Patients aged between 18 and 65 years * American Society of Anesthesiologists (ASA) physical status I-II * Scheduled for elective lumbar spine surgery in the prone position * Planned general anesthesia with total intravenous anesthesia (TIVA) * Ability to provide informed consent
Exclusion criteria
* Body mass index (BMI) ≥ 30 kg/m² * History of significant pulmonary disease (e.g., COPD, asthma) * Severe cardiovascular disease * Pregnancy * Known difficult airway * Requirement for intraoperative vasopressor infusion due to hemodynamic instability * Conversion to different surgical position or change in surgical plan * Incomplete data or protocol deviation
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Driving Pressure (ΔP) | Intraoperative period (at predefined time points: T0, T2, T5) | Driving pressure (ΔP), calculated as the difference between plateau pressure (Pplat) and positive end-expiratory pressure (PEEP), will be used as the primary outcome to assess lung stress during mechanical ventilation. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Mechanical Power | Intraoperative period (T0, T2, T5) | Mechanical power will be calculated to quantify the energy delivered to the respiratory system during mechanical ventilation. |
| Oxygenation (PaO₂/FiO₂ Ratio) | Intraoperative period (T0, T2, T5) | Oxygenation status will be assessed using the arterial oxygen partial pressure to inspired oxygen fraction (PaO₂/FiO₂) ratio. |
| PaCO₂-EtCO₂ Gradient | Intraoperative period (T0, T2, T5) | The difference between arterial carbon dioxide pressure (PaCO₂) and end-tidal CO₂ (EtCO₂) will be used to evaluate ventilation-perfusion mismatch. |
| Physiological Dead Space Fraction (VD/VT) | Intraoperative period (T0, T2, T5) | Physiological dead space fraction will be calculated using the Bohr equation to assess ventilation efficiency. |
| Dynamic Lung Compliance (Cdyn) | Intraoperative period (all time points) | Dynamic compliance will be recorded to evaluate changes in lung mechanics during ventilation. |
| Peak Airway Pressure (Ppeak) | Intraoperative period (all time points) | Peak airway pressure will be recorded to assess airway pressure changes during mechanical ventilation. |
Contacts
CONTACTBasak Pehlivan, Assoc Prof
CONTACTVeli F Pehlivan, MD
PRINCIPAL_INVESTIGATORBasak Pehlivan, Asoc Prof
Harran University Faculty of Medicine, Department of Anesthesiology
Outcome results
None listed