Hypoxemia During One-Lung Ventilation: Does It Really Matter?

Preoperative Multivariable Model for Risk Stratification of Hypoxemia During One-Lung Ventilation

BACKGROUND

Hypoxemia occurs with relative frequency during one-lung ventilation (OLV) despite advances in airway management. Lung perfusion scans are thought to be one of the most accurate methods to predict hypoxemia during OLV, but their complexity and costs are well-known limitations. There is a lack of preoperative stratification models to estimate the risk of intraoperative hypoxemia among patients undergoing thoracic surgery. Our primary objective was to develop a risk stratification model for hypoxemia during OLV based on preoperative clinical variables.

METHODS

This is a single-center, retrospective cohort study including 3228 patients who underwent lung resections with OLV from 2017 to 2022, at a tertiary academic health care center in the United States. Vital signs and ventilator settings were retrieved minute by minute. Intraoperative hypoxemia was defined as an episode of oxygen desaturation (Sp o2 <90%) for at least 5 minutes. Demographic and clinical characteristics were included in a stepwise logistic regression, which was used for the selection of predictors of the risk score model. All patients included in this cohort underwent elective lung surgery in lateral decubitus position, with double lumen tube and placement confirmation with fiberoptic bronchoscopy. Our model was validated internally using area under the receiver operating curves (AUC) with bootstrapping correction.

RESULTS

The incidence of hypoxemia during OLV was 8.9% (95% confidence interval [CI], 8.0-10.0). Multivariable logistic regression identified 9 risk factors with their corresponding scoring: preoperative Sp o2 <92% (15 points), hemoglobin <10 g/dL (6 points), age >60 years old (4 points), male sex (4 points), body mass index >30 kg/m 2 (8 points), diabetes mellitus (4 points), congestive heart failure (7 points), hypertension (3 points), and right-sided surgery (3 points). The AUC of the model after bootstrap correction was 0.708 (95% CI, 0.676-0.74). Based on the highest Youden index, the optimal score for predicting intraoperative hypoxemia was 13. The risk of hypoxemia increased from 4.7% in the first quartile of scores (0-13 points), to 32% in the third quartile (27-39 points), and 83.3% in the fourth quartile (>39 points). At scores of 20 or greater, the specificity of the model exceeded 90% and reached a positive predictive value of 80%.

CONCLUSIONS

The risk of hypoxemia during OLV can be stratified preoperatively using accessible clinical variables. Our risk model is well calibrated but showed moderate discrimination for predicting intraoperative hypoxemia. The accuracy of preoperative models for risk stratification of hypoxemia during OLV should be explored in prospective studies.

A Review of Non-Cardiac Complications of General Anesthesia: The Current State of Knowledge

General anesthesia, despite the constant development of anesthesiology, still carries certain risks. To provide safe anesthesia, it is crucial to properly qualify patients and to react in an appropriate manner when problems occur. It is therefore essential to have knowledge of risk factors, pathophysiology, symptoms, and management patterns regarding complications. This review comprehensively describes respiratory complications such as airway spasm, conditions leading to intraoperative hypoxemia, postoperative pulmonary complications (PPC), and complications of cross airway compromise, from aspects including respiratory complications and mechanical injuries. Moreover, events characteristic of this type of anesthesia, such as anaphylaxis, postoperative nausea and vomiting (PONV), neurological complications, accidental awakening during general anesthesia (AAGA), hypothermia, and malignant hyperthermia (MH), have been included. Each complication is elaborated on in terms of risk groups and factors, symptoms, and prevention and treatment options, taking into account the interrelationship of particular conditions. Although that issue is well reported in the literature, this review, in addition to a comprehensive summary of the most important non-cardiovascular and hemodynamic complications, takes into account the latest findings on methods of prevention, diagnosis, and intraoperative monitoring. The article combines a comprehensive compilation of basic information on the most significant complications, including their diagnosis and methods of intervention, along with consideration of the latest scientific developments and indication of future research directions. This review is based on the most recent articles possible, published between 2006 and 2024.

Mechanical Protective Ventilation: New Paradigms in Thoracic Surgery

One-lung ventilation (OLV) in thoracic anesthesia poses dual challenges: preventing hypoxemia and minimizing ventilator-associated lung injury (VALI). Advances such as fiberoptic bronchoscopy and improved anesthetic techniques have reduced hypoxemia, yet optimal management strategies remain uncertain. Protective ventilation, involving low tidal volumes (4-6 mL/kg), individualized PEEP, and selective alveolar recruitment maneuvers (ARM), seek to balance oxygenation and lung protection. However, questions persist regarding the ideal application of PEEP and ARM, as well as their integration into clinical practice. As for PEEP and ARM, further research is needed to address key questions and establish new guidelines.

Clinical practice of one-lung ventilation in mainland China: a nationwide questionnaire survey

BACKGROUND

Limited information is available regarding the application of lung-protective ventilation strategies during one-lung ventilation (OLV) across mainland China. A nationwide questionnaire survey was conducted to investigate this issue in current clinical practice.

METHODS

The survey covered various aspects, including respondent demographics, the establishment and maintenance of OLV, intraoperative monitoring standards, and complications associated with OLV.

RESULTS

Five hundred forty-three valid responses were collected from all provinces in mainland China. Volume control ventilation mode, 4 to 6 mL per kilogram of predictive body weight, pure oxygen inspiration, and a low-level positive end-expiratory pressure ≤ 5 cm H2O were the most popular ventilation parameters. The most common thresholds of intraoperative respiration monitoring were peripheral oxygen saturation (SpO2) of 90-94%, end-tidal CO2 of 45 to 55 mm Hg, and an airway pressure of 30 to 34 cm H2O. Recruitment maneuvers were traditionally performed by 94% of the respondents. Intraoperative hypoxemia and laryngeal injury were experienced by 75% and 51% of the respondents, respectively. The proportions of anesthesiologists who frequently experienced hypoxemia during OLV were 19%, 24%, and 7% for lung, cardiovascular, and esophageal surgeries, respectively. Up to 32% of respondents were reluctant to perform lung-protective ventilation strategies during OLV. Multiple regression analysis revealed that the volume-control ventilation mode and an SpO2 intervention threshold of < 85% were independent risk factors for hypoxemia during OLV in lung and cardiovascular surgeries. In esophageal surgery, working in a tier 2 hospital and using traditional ventilation strategies were independent risk factors for hypoxemia during OLV. Subgroup analysis revealed no significant difference in intraoperative hypoxemia during OLV between respondents who performed lung-protective ventilation strategies and those who did not.

CONCLUSIONS

Lung-protective ventilation strategies during OLV have been widely accepted in mainland China and are strongly recommended for esophageal surgery, particularly in tier 2 hospitals. Implementing volume control ventilation mode and early management of oxygen desaturation might prevent hypoxemia during OLV.

Whole lung lavage: considerations from the anesthesiology perspective

PURPOSE OF REVIEW

Whole lung lavage (WLL) remains the standard treatment for pulmonary alveolar proteinosis (PAP). The procedure involves meticulous preparation, including a multidisciplinary team and appropriate facilities, to ensure patient safety and procedural success. Effective anesthesia management is essential to allow for successful completion of the procedure and prevent complications.

RECENT FINDINGS

Effective anesthesia management, including total intravenous anesthesia (TIVA) and careful intraoperative monitoring, is essential to prevent complications such as hypoxemia and fluid overload. Proper airway control with a double-lumen tube, careful positioning, and continuous monitoring during the lavage phase are key to minimizing risks. Challenges such as fluid spillage and ventilation-perfusion mismatch must be managed proactively with techniques such as fiberoptic bronchoscopy and recruitment maneuvers. In cases of severe hypoxemia, advanced options like extra-corporeal membrane oxygenation (ECMO) or sequential lavage may be required.

SUMMARY

WLL is a pivotal treatment for PAP, offering significant relief and improvement for many patients despite the challenges in standardizing the procedure due to the rare nature of the condition. Involvement of a multidisciplinary team involving pulmonologist, anesthesiologist, critical care personnel, operating room personnel and in some cases and centers, cardiothoracic surgeon and perfusionist is critical to the success of the procedure.

Effect of dexmedetomidine on postoperative high-sensitivity cardiac troponin T in patients undergoing video-assisted thoracoscopic surgery: a prospective, randomised controlled trial

BACKGROUND

One-lung ventilation and intrathoracic operations during thoracoscopic surgery often result in intraoperative hypoxaemia and haemodynamic fluctuations, resulting in perioperative myocardial injury. Dexmedetomidine, an alpha-2 (α-2) agonist, has demonstrated myocardial protection. We hypothesize that the routine intravenous administration of dexmedetomidine could reduce the extent of myocardial injury during video-assisted thoracoscopic surgery (VATS).

METHODS

The study included patients aged ≥ 45 years, classified as American Society of Anesthesiologists physical status I-III, who underwent general anesthesia for video-assisted thoracoscopic surgery. The patients were randomly assigned to either the intervention group, receiving general anesthesia with dexmedetomidine, or the control group, receiving general anesthesia without dexmedetomidine. Patients in the intervention group received a loading dose of dexmedetomidine (0.5 µg·kg-1) before anesthesia induction, followed by a continuous infusion (0.5 µg·kg-1·h-1) until the completion of the surgery. Placebos (saline) were administered for the control group to match the treatment. The primary outcome assessed was the high-sensitivity cardiac troponin T on postoperative day 1. Additionally, the incidence of myocardial injury after noncardiac surgery (MINS) was noted.

RESULTS

A total of 110 participants completed this study. The median [interquartile range (IQR)] concentration of hs-cTnT on postoperative day 1 was lower in the intervention group compared with the control group (7 [6-9] vs. 8 [7-11] pg·ml-1; difference in medians,1 pg·ml-1; 95% confidence interval [CI], 0 to 2; P = 0.005). Similarly, on postoperative day 3, the median [IQR] concentration of hs-cTnT in the intervention group was also lower than that in the control group (6 [5-7] vs. 7 [6-9]; difference in medians,1 pg·ml-1; 95%CI, 0 to 2; P = 0.011). Although the incidence of MINS was not statistically significant (the intervention group vs. the control group, 3.8% vs. 9.1%, P = 0.465), there was a decreasing trend in the incidence of MINS in the intervention group.

CONCLUSION

The administration of perioperative dexmedetomidine in patients ≥ 45 years undergoing video-assisted thoracoscopic surgery could lower the release of postoperative hs-cTnT without reducing incidence of myocardial injury.

TRIAL REGISTRATION

chictr.org.cn (ChiCTR2200063193); prospectively registered 1 September 2022.

Effects of Dexmedetomidine in Improving Oxygenation and Reducing Pulmonary Shunt in High-Risk Pediatric Patients Undergoing One-Lung Ventilation for Thoracic Surgery: A Double-Blind Randomized Controlled Trial

Background and objectives Pediatric thoracic surgery has unique considerations due to the immaturity of the respiratory system anatomically and physiologically, which presents technical and pharmacological considerations, including the very common technique of one-lung ventilation (OLV), which causes serious complications in children. Therefore, we investigated the effects of dexmedetomidine on oxygenation and pulmonary shunt fraction (Qs/Qt) in high-risk pediatric patients undergoing OLV for thoracic surgery. This randomized controlled trial aimed to investigate dexmedetomidine's effect on the partial pressure of arterial oxygen (PaO2) and pulmonary shunt fraction (Qs/Qt). Methods A total of 63 children underwent thoracic surgery with OLV and were divided into two groups. The dexmedetomidine group (group Dex, n = 32) received dexmedetomidine (0.4 μg/kg/hour), and the placebo group (group placebo, n = 31) received normal saline. Two arterial and central venous blood samples were taken for arterial and venous blood gas analysis at four time points: T1 (10 minutes after mechanical ventilation of total lung ventilation), T2 (10 minutes after OLV), T3 (60 minutes after OLV), and T4 (20 minutes after the end of OLV). At these intervals, the following parameters were measured: PaO2, Qs/Qt, mean arterial pressure (MAP), heart rate (HR), and peak inspiratory pressure (PIP). Results The two groups had no significant differences in FEV1/FVC and baseline pulmonary shunt fraction (Qs/Qt). Dexmedetomidine significantly improved PaO2 compared with placebo during OLV (T2 and T3). There was a significant decrease in Qs/Qt compared with placebo during OLV (T2, T3, and T4). There was a decrease in PIP compared with placebo during OLV (T2 and T3). No statistically significant differences in MAP or HR were observed between the groups. Conclusion Infusion of dexmedetomidine during OLV in high-risk pediatric thoracic surgery reduces shunt and pulmonary shunt fraction Qs/Qt, improves PaO2 and body oxygenation, reduces PIP and pressure load, and maintains hemodynamic stability (MAP, HR).

Dexmedetomidine improves lung injury after one-lung ventilation in esophageal cancer patients by inhibiting inflammatory response and oxidative stress

Aim

To explore the effect of Dexmedetomidine (DEX) on lung injury in patients undergoing One-lung ventilation (OLV).

Methods

Esophageal cancer patients undergoing general anesthesia with OLV were randomly divided into the DEX group and control group, with 30 cases in each group. Mean arterial pressure (MAP), heart rate (HR), arterial partial pressure of oxygen (PO2), and arterial partial pressure of nitrogen dioxide (PCO2) were recorded at the time points after anesthesia induction and before OLV (T1), OLV 30 min (T2), OLV 60 min (T3), OLV 120 min (T4), OLV end before (T5) and before leaving the room (T6) in both groups. Reverse Transcription-Polymerase Chain Reaction (RT-qPCR) was applied to detect the levels of CC16 mRNA. Enzyme-linked immunosorbent assay (ELISA) was used to detect serum CC16 protein levels. The content of malondialdehyde (MDA) in serum was determined by thio barbituric acid (TBA) method. ELISA was used to measure the concentrations of TNF-α (tumor necrosis factor-alpha)/and IL-6 (interleukin 6).

Results

DEX treatment slowed down HR at time points T1-T6 and increased PO2 and PCO2 at time points T2-T5 compared with the control group. Moreover, at time points T2-T6, DEX treatment reduced the levels of club cell secretory protein-16 (CC16) mRNA and serum CC16 protein levels. Furthermore, DEX treatment caused the reduction of MDA, TNF-α and IL-6 concentrations in serum of patients.

Conclusion

During the OLV process, DEX could reduce serum CC16 protein levels, inhibit inflammatory reactions and oxidative stress, and improve oxygenation index, indicating a protective effect on lung injury during OLV.

Effects of positive end-expiratory pressure on regional cerebral oxygen saturation in elderly patients undergoing thoracic surgery during one-lung ventilation: a randomized crossover-controlled trial

BACKGROUND

A significant reduction in regional cerebral oxygen saturation (rSO2) is commonly observed during one-lung ventilation (OLV), while positive end-expiratory pressure (PEEP) can improve oxygenation. We compared the effects of three different PEEP levels on rSO2, pulmonary oxygenation, and hemodynamics during OLV.

METHODS

Forty-three elderly patients who underwent thoracoscopic lobectomy were randomly assigned to one of six PEEP combinations which used a crossover design of 3 levels of PEEP-0 cmH2O, 5 cmH2O, and 10 cmH2O. The primary endpoint was rSO2 in patients receiving OLV 20 min after adjusting the PEEP. The secondary outcomes included hemodynamic and respiratory variables.

RESULTS

After exclusion, thirty-six patients (36.11% female; age range: 60-76 year) were assigned to six groups (n = 6 in each group). The rSO2 was highest at OLV(0) than at OLV(10) (difference, 2.889%; [95% CI, 0.573 to 5.204%]; p = 0.008). Arterial oxygen partial pressure (PaO2) was lowest at OLV(0) compared with OLV(5) (difference, -62.639 mmHg; [95% CI, -106.170 to -19.108 mmHg]; p = 0.005) or OLV(10) (difference, -73.389 mmHg; [95% CI, -117.852 to -28.925 mmHg]; p = 0.001), while peak airway pressure (Ppeak) was lower at OLV(0) (difference, -4.222 mmHg; [95% CI, -5.140 to -3.304 mmHg]; p < 0.001) and OLV(5) (difference, -3.139 mmHg; [95% CI, -4.110 to -2.167 mmHg]; p < 0.001) than at OLV(10).

CONCLUSIONS

PEEP with 10 cmH2O makes rSO2 decrease compared with 0 cmH2O. Applying PEEP with 5 cmH2O during OLV in elderly patients can improve oxygenation and maintain high rSO2 levels, without significantly increasing peak airway pressure compared to not using PEEP.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR2200060112 on 19 May 2022.

The anesthesia management of totally thoracoscopic cardiac surgery: A single-center retrospective study

Anesthesia management of Totally thoracoscopic cardiac surgery (TTCS) has been the subject of much debate and discussion. In this single center retrospective study, we summarize the experience of clinical anesthesia management for TTCS by review the medical records of our medical center and look forward to its future development. In this retrospective study, 103 patients (49 male and 54 female) were enrolled, the mean age was 56.7 ± 14.4 years old. The participants underwent Mitral Valve Replacement (MVR) + Tricuspid Valve Annuloplasty (TVA) (42, 40.8%), Mitral Valve Annuloplasty (MVA) + TVA (38, 36.9%), MVA (21, 20.4%), and MVR (2, 1.9%)，respectively. Intraoperative hypoxemia, radiographic pulmonary infiltrates, and pneumonia were observed in 19 (18.4%), 84 (81.6%), and 13 (12.6%) patients, respectively. The LOS of ICU and POD were as follows: MVR + TVA (55.1 ± 25h, 9.9 ± 3.5 d), MVA + TVA (56.5 ± 28.4h, 9.4 ± 4.2d), MVA (37.9 ± 21.9h, 8.1 ± 2.3d) and MVR (48 ± 4.2h, 7.5 ± 2.1d). No reintubation, reoperations, postoperative cognitive dysfunction, 30-day mortality were observed in the present study. The present study demonstrated that applying this anesthesia management for TTCS associated with acceptable morbidity, intensive care unit and postoperative hospital lengths of stay. The finding from the present study might provide some new approach for Anesthesia management of TTCS.

Effect of the VivaSight double-lumen tube on the incidence of hypoxaemia during one-lung ventilation in patients undergoing thoracoscopic surgery: a study protocol for a prospective randomised controlled trial

INTRODUCTION

A double-lumen tube (DLT) is a traditional one-lung ventilation tool that needs to be positioned under the guidance of a fibreoptic bronchoscope or auscultation. The placement is complex, and poor positioning often causes hypoxaemia. In recent years, VivaSight double-lumen tubes (v-DLTs) have been widely used in thoracic surgery. Because the tubes can be continuously observed during intubation and the operation, malposition can be corrected at any time. However, the effect of v-DLT on perioperative hypoxaemia has been rarely reported. The aim of this study was to observe the incidence of hypoxaemia during one-lung ventilation with v-DLT and to compare the perioperative complications between v-DLT and conventional double-lumen tube (c-DLT).

METHODS AND ANALYSIS

One hundred patients planning to undergo thoracoscopic surgery will be randomised into the c-DLT group and the v-DLT group. During one-lung ventilation, both groups of patients will receive low tidal volume for volume control ventilation. When the blood oxygen saturation falls below 95%, the DLT will be repositioned and the oxygen concentration will be increased to improve the respiratory parameters (5 cm H₂O Positive end-expiratory pressure (PEEP) on the ventilation side and 5 cm H₂O CPAP (continuous airway positive pressure) on the operation side), and double lung ventilation measures will be taken in sequence to prevent a further decline in blood oxygen saturation. The primary outcomes are the incidence and duration of hypoxaemia and the number of intraoperative hypoxaemia treatments, and the secondary outcomes will be postoperative complications and total hospitalisation expenses.

ETHICS AND DISSEMINATION

The study protocol was approved by the Clinical Research Ethics Committee of The First Affiliated Hospital, Sun Yat-sen University (2020-418) and registered at the Chinese Clinical Trial Registry (http://www.chictr.org.cn). The results of the study will be analysed and reported.

TRIAL REGISTRATION NUMBER

ChiCTR2100046484.

Effects of Acute Hypobaric Hypoxia Exposure on Cardiovascular Function in Unacclimatized Healthy Subjects: A "Rapid Ascent" Hypobaric Chamber Study

Background: This study aimed to observe the effects of a fast acute ascent to simulated high altitudes on cardiovascular function both in the main arteries and in peripheral circulation. Methods: We examined 17 healthy volunteers, between 18 and 50 years old, at sea level, at 3842 m of hypobaric hypoxia and after return to sea level. Cardiac output (CO) was measured with Doppler transthoracic echocardiography. Oxygen delivery was estimated as the product of CO and peripheral oxygen saturation (SpO2). The brachial artery’s flow-mediated dilation (FMD) was measured with the ultrasound method. Post-occlusion reactive hyperemia (PORH) was assessed by digital plethysmography. Results: During altitude stay, peripheral oxygen saturation decreased (84.9 ± 4.2% of pre-ascent values; p < 0.001). None of the volunteers presented any hypoxia-related symptoms. Nevertheless, an increase in cardiac output (143.2 ± 36.2% of pre-ascent values, p < 0.001) and oxygen delivery index (120.6 ± 28.4% of pre-ascent values; p > 0.05) was observed. FMD decreased (97.3 ± 4.5% of pre-ascent values; p < 0.05) and PORH did not change throughout the whole experiment. Τhe observed changes disappeared after return to sea level, and normoxia re-ensued. Conclusions: Acute exposure to hypobaric hypoxia resulted in decreased oxygen saturation and increased compensatory heart rate, cardiac output and oxygen delivery. Pre-occlusion vascular diameters increase probably due to the reduction in systemic vascular resistance preventing flow-mediated dilation from increasing. Mean Arterial Pressure possibly decrease for the same reason without altering post-occlusive reactive hyperemia throughout the whole experiment, which shows that compensation mechanisms that increase oxygen delivery are effective.

Flurbiprofen used in one-lung ventilation improves intraoperative regional cerebral oxygen saturation and reduces the incidence of postoperative delirium

BACKGROUND

We previously demonstrated that flurbiprofen increased arterial oxygen partial pressure and reduced intrapulmonary shunts. The present study aims to investigate whether flurbiprofen improves intraoperative regional cerebral oxygen saturation (rScO₂) and reduces the incidence of postoperative delirium (POD) in elderly patients undergoing one-lung ventilation (OLV).

METHODS

One hundred and twenty patients undergoing thoracoscopic lobectomy were randomly assigned to the flurbiprofen-treated group (n = 60) and the control-treated group (n = 60). Flurbiprofen was intravenously administered 20 minutes before skin incision. The rScO₂ and partial pressure of arterial oxygen (PaO₂) were recorded during the surgery, and POD was measured by the Confusion Assessment Method (CAM) within 5 days after surgery. The study was registered in the Chinese Clinical Trial Registry with the number ChiCTR1800020032.

RESULTS

Compared with the control group, treatment with flurbiprofen significantly improved the mean value of intraoperative rScO₂ as well as the PaO₂ value (P < 0.05, both) and significantly reduced the baseline values of the rScO₂ area under threshold (AUT) (P < 0.01) at 15, 30, and 60 min after OLV in the flurbiprofen-treated group. After surgery, the POD incidence in the flurbiprofen-treated group was significantly decreased compared with that in the control group (P < 0.05).

CONCLUSION

Treatment with flurbiprofen may improve rScO₂ and reduce the incidence of POD in elderly patients undergoing thoracoscopic one-lung ventilation surgery for lung cancer.

CLINICAL TRIAL REGISTRATION

http://www.chictr.org/cn/, identifier ChiCTR1800020032.

The use of oxygen reserve index in one-lung ventilation and its impact on peripheral oxygen saturation, perfusion index and, pleth variability index

Background

Our goal is to investigate the use of the oxygen reserve index (ORi) to detect hypoxemia and its relation with parameters such as; peripheral oxygen saturation, perfusion index (PI), and pleth variability index (PVI) during one-lung ventilation (OLV).

Methods

Fifty patients undergoing general anesthesia and OLV for elective thoracic surgeries were enrolled in an observational cohort study in a tertiary care teaching hospital. All patients required OLV after a left-sided double-lumen tube insertion during intubation. The definition of hypoxemia during OLV is a peripheral oxygen saturation (SpO2) value of less than 95%, while the inspired oxygen fraction (FiO2) is higher than 50% on a pulse oximetry device. ORi, pulse oximetry, PI, and PVI values were measured continuously. Sensitivity, specificity, positive and negative predictive values, likelihood ratios, and accuracy were calculated for ORi values equal to zero in different time points during surgery to predict hypoxemia. At Clinicaltrials.gov registry, the Registration ID is NCT05050552.

Results

Hypoxemia was observed in 19 patients (38%). The accuracy for predicting hypoxemia during anesthesia induction at ORi value equals zero at 5 min after intubation in the supine position (DS5) showed a sensitivity of 92.3% (95% CI 84.9–99.6), specificity of 81.1% (95% CI 70.2–91.9), and an accuracy of 84.0% (95% CI 73.8–94.2). For predicting hypoxemia, ORi equals zero show good sensitivity, specificity, and statistical accuracy values for time points of DS5 until OLV30 where the sensitivity of 43.8%, specificity of 64%, and an accuracy of 56.1% were recorded. ORi and SpO2 correlation was found at DS5, 5 min after lateral position with two-lung ventilation (DL5) and at 10 min after OLV (OLV10) (p = 0.044, p = 0.039, p = 0.011, respectively). Time-dependent correlations also showed that; at a time point of DS5, ORi has a significant negative correlation with PI whereas, no correlations with PVI were noted.

Conclusions

During the use of OLV for thoracic surgeries, from 5 min after intubation (DS5) up to 30 min after the start of OLV, ORi provides valuable information in predicting hypoxemia defined as SpO2 less than 95% on pulse oximeter at FiO2 higher than 50%.