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This single-center randomized controlled trial aims to evaluate whether intraoperative monitoring using the Oxygen Reserve Index (ORI) reduces the incidence of postoperative atelectasis, as assessed by lung ultrasound (LUS), in adult patients undergoing elective robotic surgery under general anesthesia.
Postoperative atelectasis is observed in 60-90% of patients undergoing general anesthesia. Factors such as high inspired oxygen concentration, muscle relaxation, and reduced functional residual capacity contribute to its development through mechanisms like absorption atelectasis. The persistence of atelectasis increases the risk of pneumonia, hypoxia, prolonged hospital stay, healthcare costs, and mortality. Despite the well-known pathophysiology, the optimal intraoperative fraction of inspired oxygen (FiO₂) remains unclear.
The Oxygen Reserve Index (ORI) is a non-invasive, continuous parameter that reflects the oxygen reserve within the moderate hyperoxia range (100-200 mmHg). It may facilitate individualized FiO₂ titration to avoid hyperoxia-related atelectasis. Lung ultrasound (LUS) is a reliable, radiation-free bedside tool for detecting atelectasis.
This study hypothesizes that ORI-guided oxygen therapy will reduce the incidence of postoperative atelectasis compared to standard Peripheral Capillary Oxygen Saturation (SpO₂)-guided therapy.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Peripheral Oxygen Saturation (SpO₂) Group | Active Comparator | FiO₂ adjusted based on pulse oximetry to maintain SpO₂ ≥98% |
|
| Peripheral Oxygen Saturation and Oxygen Reserve Index (SpO₂-ORI) Group | Active Comparator | FiO₂ adjusted using both SpO₂ and ORI to maintain ORI between 0-0.3 |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Peripheral Oxygen Saturation (SpO₂) Group | Procedure | FiO₂ adjusted based on pulse oximetry to maintain SpO₂ ≥98% |
|
| Measure | Description | Time Frame |
|---|---|---|
| Postoperative LUS score at 30 min | Lung ultrasound (LUS) measurements will be performed by an anesthesiologist blinded to the study groups, who is experienced in lung ultrasonography with at least 100 prior examinations. LUS will be performed and recorded 30 minutes before surgery while patients are in the supine position, using a linear probe (6-12 MHz). The total LUS score will be calculated as the sum of the scores for the 12 quadrants of each hemithorax (range: 0-36). Higher scores will indicate more severe loss of aeration. Loss of aeration will be scored as follows:
| At 30 minutes following tracheal extubation at the end of surgery |
| Measure | Description | Time Frame |
|---|---|---|
| Preoperative LUS score | Lung ultrasound (LUS) measurements will be performed by an anesthesiologist blinded to the study groups, who is experienced in lung ultrasonography with at least 100 prior examinations. LUS will be performed and recorded 30 minutes before surgery while patients are in the supine position, using a linear probe (6-12 MHz). The total LUS score will be calculated as the sum of the scores for the 12 quadrants of each hemithorax (range: 0-36). Higher scores will indicate more severe loss of aeration. Loss of aeration will be scored as follows: • 0: Presence of A-lines or fewer than two B-lines • 1: Three or more well-defined B-lines • 2: Presence of multiple coalescent B-lines • 3: Presence of lung consolidation characterized by dynamic air bronchograms |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| NILGUN KAVRUT OZTURK, PROFESSOR MD | Antalya Training and Research Hospital | Study Chair |
| AYSE MERVE ERDEM, RESIDENT | Antalya Training and Research Hospital | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Antalya Training and Research Hospital | Antalya | Muratpasa | 07100 | Turkey (Türkiye) |
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| ID | Term |
|---|---|
| D001261 | Pulmonary Atelectasis |
| D018496 | Hyperoxia |
| ID | Term |
|---|---|
| D008171 | Lung Diseases |
| D012140 | Respiratory Tract Diseases |
| D012818 | Signs and Symptoms, Respiratory |
| D012816 | Signs and Symptoms |
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| ID | Term |
|---|---|
| D000089382 | Oxygen Saturation |
| D007784 | Lactoperoxidase |
| D044382 | Population Groups |
| ID | Term |
|---|---|
| D008660 | Metabolism |
| D010544 | Peroxidases |
| D010088 | Oxidoreductases |
| D004798 | Enzymes |
| D045762 |
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| Peripheral Oxygen Saturation and Oxygen Reserve Index (SpO₂-ORI) Group | Procedure | FiO₂ adjusted using both SpO₂ and ORI to maintain ORI between 0-0.3 |
|
| 30 minutes prior to patient transfer to the operating room |
| Intraoperative arterial partial pressure of oxygen (PaO₂) | Arterial blood samples will be collected intraoperatively at baseline (immediately before skin incision) and at the 1st, 2nd, and 3rd hour to measure the partial pressure of oxygen (PaO₂). | At baseline (immediately before incision), and at 1st, 2nd, and 3rd hour intraoperatively |
| Intraoperative fraction of inspired oxygen (FiO₂) | The fraction of inspired oxygen administered to the patient will be recorded at baseline (immediately before skin incision) and hourly at the 1st, 2nd, and 3rd hour during surgery. | At baseline (immediately before incision), and at 1st, 2nd, and 3rd hour intraoperatively |
| Intraoperative Oxygen Reserve Index (ORI) | Continuous monitoring of the Oxygen Reserve Index (ORI) will be performed, and values will be documented at baseline (immediately before skin incision) and at 1st, 2nd, and 3rd hour intraoperatively.Intraoperative Oxygen Reserve Index (ORI) will be measured. ORI is a unitless index ranging from 0.00 to 1.00, with higher values indicating a greater oxygen reserve. | At baseline (immediately before incision), and at 1st, 2nd, and 3rd hour intraoperatively |
| Number of episodes with severe hyperoxia (PaO₂ > 200 mmHg) | The number of severe hyperoxia episodes, defined as PaO₂ levels exceeding 200 mmHg, will be recorded at baseline (immediately before skin incision) and at the 1st, 2nd, and 3rd hour during surgery.Each time point will be evaluated independently, and the number of measurements exceeding 200 mmHg will be counted.This is a binary threshold-based event count, not a continuous scale; thus, no scoring system or scale interpretation is applicable. | At baseline (immediately before incision), and at 1st, 2nd, and 3rd hour intraoperatively |
| D013568 | Pathological Conditions, Signs and Symptoms |
| Enzymes and Coenzymes |
| D003710 | Demography |
| D011154 | Population Characteristics |