Oxygen reserve index, a new method of monitoring oxygenation status: what do we need to know?

Oxygen concentration titration guided by oxygen reserve index during pediatric laryngeal surgery with high-flow nasal cannula oxygen: a randomized controlled trial

PURPOSE

The objective of this study was to evaluate whether adjusting the oxygen concentration guided by the Oxygen Reserve Index (ORI) during pediatric laryngeal surgery with High Flow Nasal Cannula Oxygen (HFNO) could achieve postoperative PaO2 close to physiological levels while ensuring adequate oxygenation in surgery.

METHODS

Sixty pediatric patients undergoing laryngeal surgery or examination were randomly assigned to two groups. The ORI group received oxygen concentration adjustments every 5 min to maintain a target ORI value of 0.21, whereas the control group did not undergo any adjustments. Postoperative PaO2, time weighted average fraction of inspired oxygen (FiO2), and mean Peripheral Oxygen Saturation (SpO2) were compared between groups. Finally, some analyses were conducted to examine the relationship of ORI with PaO2.

RESULTS

In general, the postoperative PaO2 was 164.9 ± 48.8 mmHg in ORI group and 323.0 ± 87.7 mmHg in control group (P < 0.01). The time weighted average FiO2 in the ORI group was 85.9 [81.8-92.7] %. There was no significant difference in mean SpO2 between the two groups (ORI vs. control: 98.4 [97.7-99.2] vs. 98.8 [97.7-99.5]; P = 0.36). According to the analyses, the optimal cut value for ORI was determined to be 0.195 when PaO2 was 150 mmHg.

CONCLUSIONS

In pediatric laryngeal surgery with HFNO, reducing oxygen concentration guided by ORI helped achieve postoperative PaO2 levels closer to physiological norms without compromising intra-operative oxygenation.

Evaluation of the relationship between the STOP-Bang score with oxygen reserve index and difficult airway: a prospective observational study

BACKGROUND

Patients diagnosed with Obstructive Sleep Apnea (OSA) syndrome have a tendency towards hypoventilation, hypoxia, and hypercarbia in the perioperative period. This study hypothesized that the Oxygen Reserve Index (ORi) could predict possible hypoxia and determine difficult airways in patients at risk for OSA, as determined by the STOP-Bang questionnaire.

METHODS

This prospective study included adult patients undergoing elective surgery under general anesthesia with endotracheal intubation, divided into two groups: low risk (0-2 points) and high risk (3-8 points) based on their STOP-Bang questionnaire results. The primary outcome measure was the highest ORi value reached during preoxygenation and the time to reach this value. Data were recorded at four time points: before preoxygenation (T1), end of preoxygenation (T2), end of mask ventilation (T3), and end of intubation (T4), as well as partial oxygen pressure values in T1, T2, and T4. The secondary outcome measures were the grading scale for mask ventilation, Cormack-Lehane score, tonsil dimensions, use of a stylet, and application of the burp maneuver during intubation.

RESULTS

In the high-risk group, preoperative peripheral oxygen saturation values, the highest ORi value reached in preoxygenation, and ORi values at T3 and T4 times were lower, and the time to reach the highest ORi value was longer (p < 0.05).

CONCLUSION

Using ORi in patients with OSA may be useful in evaluating oxygenation, and since difficult airway is more common, ORi monitoring will better manage possible hypoxic conditions.

Revolutionizing trauma care: advancing coagulation management and damage control anesthesia

Despite advances in emergency transfer systems and trauma medicine, the incidence of preventable deaths due to massive hemorrhage remains high. Recent immunological research has elucidated key mechanisms underlying trauma-induced coagulopathy in the early stages of trauma, including sympathoadrenal stimulation, shedding of the glycocalyx, and endotheliopathy. Consequently, the condition progresses to fibrinogen depletion, hyperfibrinolysis, and platelet dysfunction. Coexisting factors such as uncorrected acidosis, hypothermia, excessive crystalloid administration, and a history of anticoagulant use exacerbate coagulopathy. This study introduces damage-control anesthetic management based on recent insights into damage-control resuscitation, emphasizing the importance of rapid transport, timely bleeding control, early administration of antifibrinolytics and fibrinogen concentrates, and maintenance of calcium levels and body temperature. Additionally, this study discusses brain-protective strategies for trauma patients with brain injuries and the utilization of cartridge-based viscoelastic assays for goal-directed coagulation management in trauma settings. This comprehensive approach may provide potential insights for anesthetic management in the fast-paced field of trauma medicine.

Use of oxygen reserve index during bronchoscopic balloon dilation for subglottic stenosis in a patient with left ventricular assist device implantation -a case report

BACKGROUND

Monitoring the oxygenation status is crucial during general anesthesia to ensure patient safety. Although noninvasive pulse oximetry is commonly used to monitor percutaneous oxygen saturation (SpO2), it may not accurately reflect changes in oxygen partial pressure when the latter is excessively high or low. The oxygen reserve index (ORi) provides real-time information about the oxygen reserve status.

CASE

We present a case of successful management of subglottic stenosis using balloon bronchoscopy in an infant with a left ventricular assist device implantation under ORi monitoring to predict hypoxemia during the surgical procedure.

CONCLUSIONS

Utilizing ORi monitoring during anesthesia for procedures involving apnea in critically ill infants can help predict impending desaturation before a drop in SpO2 occurs, allowing anesthesiologists to effectively anticipate and manage the apnea period. Continuous ORi monitoring offers valuable insights during surgical procedures, especially in infants with compromised respiratory and cardiovascular functions.

Effectiveness of the oxygen reserve index in detecting and preventing hyperoxia in critically ill patients on mechanical ventilation: a randomized controlled trial

AIM

To assess the effectiveness of fraction of inspired oxygen (FiO2) titration guided by oxygen reserve index (ORi) in preventing hyperoxia in intensive care unit (ICU) patients receiving mechanical ventilator support.

METHODS

Patients aged 18 years and older who were admitted to a tertiary ICU and required mechanical ventilator support were randomly divided into two groups: the control group (n=30) and the oxygen saturation (SpO2) +ORi group (n=30). In the SpO2+ORi group, the goal was to maintain SpO2 between 95% and 98% and ORi at 0.00. In both groups, SpO2, ORi, partial pressure of oxygen (PaO2), partial pressure of carbon dioxide, positive end-expiratory pressure, FiO2, and hemodynamic parameters were recorded every six hours for two consecutive days.

RESULTS

A very strong positive linear correlation was found between PaO2 and ORi (r=0.937; P<0.001). In the ORi+SpO2 group, PaO2 values were significantly lower and decreased with FiO2 titration over time. Severe hyperoxia was observed in 24.8% of the control group and in only 3.3% of the ORi+SpO2 group. When PaO2>120 mm Hg, FiO2>0.40 was found in 83.5% of the control group, and in 40% of the ORi+SpO2 group.

CONCLUSION

FiO2 titration guided by ORi+SpO2 effectively prevents hyperoxia and reduces the exposure time to hyperoxia in critically ill patients.

Comparison between Arterial Blood Gases and Oxygen Reserve Index™ in a SCUBA Diver: A Case Report

Hypoxia and hyperoxia are both worrisome issues potentially affecting SCUBA divers, but validated methods to monitor these two conditions underwater are still lacking. In this experiment, a volunteer SCUBA diver was equipped with a pulse oximeter to detect peripheral oxygen saturation (SpO₂) and a device to monitor the oxygen reserve index (ORi™). ORi™ values were compared with arterial blood oxygen saturation (SaO₂) and the partial pressure of oxygen (PaO₂) obtained from the cannulated right radial artery at three steps: at rest out of water; at -15 m underwater after pedaling on a submerged bike; after resurfacing. SpO₂ and ORi™ mirrored the changes in SaO₂ and PaO₂, confirming the expected hyperoxia at depth. To confirm the potential usefulness of an integrated SpO₂ and ORi™ device, further studies are needed on a broader sample with different underwater conditions and diving techniques.

Anesthetic Management Using the Oxygen Reserve Index for Tracheal Resection and Tracheal End-to-End Anastomosis for a Malignant Thyroid Tumor With Tracheal Invasion

When tracheal invasion of cancerous diseases such as thyroid cancer occurs, tracheal resection followed by end-to-end anastomosis is a treatment of choice. Anesthetic management of the patient during this procedure may pose challenges, such as maintaining ventilation during tracheal dissection, resection of the tracheal invasion, and tracheal end-to-end anastomosis. Here, we have presented a case of a woman in her 50s. Computed tomography of the head and neck displayed a 31-mm mass in the medial lobe of the thyroid gland, and irregularities in the trachea and right tracheoesophageal groove. We decided to perform total thyroidectomy followed by tracheal resection and end-to-end tracheal anastomosis, as a radical treatment. Anesthetic management was successfully performed without a decrease in the peripheral blood oxygen saturation level, due to managing oxygenation by using the oxygen reserve index (ORI^TM) monitoring during the tracheostomy, tracheal infiltration division resection, and tracheal end-to-end suturing. This case was a unique situation requiring two intraoperative tube exchanges, but the ORI monitoring of oxygenation enabled safe anesthetic management.

Investigation of preoxygenation methods in cesarean surgeries with the oxygen reserve index

OBJECTIVES

To investigate preoxygenation methods that were carried out for 3 minutes (min) at tidal volume and 30 seconds (s) with the 4 deep vital capacity technique using the Oxygen Reserve Index (ORI) among pregnant women.

METHODS

This prospective study was carried out between December 2020 and 2021. The patients were randomly divided into 2 groups with the provision of preoxygenation using 100% O2 at a rate of 10 L.min-1 for 3 min at normal tidal volume (Group 1) and 30 s with the 4 deep vital capacity technique (Group 2). For the pregnant women who underwent routine anesthesia induction, hemodynamic parameters before preoxygenation, as well as their fraction of inspired O2 (FiO2), fraction of expired O2 (FeO2), and ORI values were recorded after preoxygenation and 0, 3 and 7 minutes after intubation (T1, T2, T3, and T4).

RESULTS

The study was completed with 66 patients. FiO2 values were found to be low in T1 (p=0.012) in Group 1, and high in FeO2 values in T1 and T2 (p=0.025 and 0.009) in Group 2, while no significant differences were found at other times (p>0.05). Oxygen Reserve Index values did not show a significant difference in comparisons between groups, but ORI values of Group 1 after intubation were significantly lower than those measured after preoxygenation in in-group comparisons (p<0.001). According to the results of the correlation analyses between the mean ORI values and their mean FeO2 and FiO2 values, there were weak and positive statistically significant relationships at T3 and T4 (p<0.05).

CONCLUSION

As we obtained greater FiO2 and FeO2 values in preoxygenation with the 30 s 4 deep vital capacity method, and because this method did not cause a significant decrease in the post-intubation ORI values, we believe that the usage of this method in cesarean section surgeries may be appropriate.

Oxygen reserve index guided fraction of inspired oxygen titration to reduce hyperoxemia during laparoscopic gastrectomy: A randomized controlled trial

BACKGROUND

The usefulness of the oxygen reserve index (ORi) in reducing hyperoxemia remains unclear. We designed this study to investigate whether fraction of inspired oxygen (FiO2) adjustment under a combination of ORi and peripheral oxygen saturation (SpO2) guidance can reduce intraoperative hyperoxemia compared to SpO2 alone.

METHODS

In this prospective, double-blind, randomized controlled study, we allocated patients scheduled for laparoscopic gastrectomy to the SpO2 group (FiO2 adjusted to target SpO2 ≥ 98%) or the ORi-SpO2 group (FiO2 adjusted to target 0 < 0 ORi < .3 and SpO2 ≥ 98%). The ORi, SpO2, FiO2, arterial partial pressure of oxygen (PaO2), and incidence of severe hyperoxemia (PaO2 ≥ 200 mm Hg) were recorded before and 1, 2, and 3 hours after surgical incision. Data from 32 and 30 subjects in the SpO2 and ORi-SpO2 groups, respectively, were analyzed.

RESULTS

PaO2 was higher in the SpO2 group (250.31 ± 57.39 mm Hg) than in the ORi-SpO2 group (170.07 ± 49.39 mm Hg) 1 hour after incision (P < .001). PaO2 was consistently higher in the SpO2 group than in the ORi-SpO2 group, over time (P = .045). The incidence of severe hyperoxemia was higher in the SpO2 group (84.4%) than in the ORi-SpO2 group (16.7%, P < .001) 1 hour after incision. Higher FiO2 was administered to the SpO2 group [52.5 (50-60)] than the ORi-SpO2 group [40 (35-50), P < .001] 1 hour after incision. SpO2 was not different between the 2 groups.

CONCLUSION

The combination of ORi and SpO2 guided FiO2 adjustment reduced hyperoxemia compared to SpO2 alone during laparoscopic gastrectomy.

[Oxygen reserve index: a new parameter for oxygen therapy]

Oxygen reserve index (ORI) is a novel dimensionless index used for noninvasive, real-time, and continuous monitoring of oxygenation, and ORI value ranges from 0 to 1, which reflects the range of 100-200 mmHg for arterial partial pressure of oxygen. ORI combined with pulse oximetry may help to accurately adjust the concentration of inspired oxygen and prevent hyperoxemia and hypoxemia. ORI is suitable for various clinical situations, and the medical staff should master this novel parameter and use it properly to assess the oxygenation of patients. In addition, several limitations of ORI should be noticed during clinical application.

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%.

The outcomes of using high oxygen concentration in pediatric patients

Oxygen reserve index, available as part of Masimo Rainbow SET pulse oximetry, is a noninvasive and continuous variable intended to provide insight into a patient's oxygen status in the moderate hyperoxic range (PaO₂ > 100 and ≤ 200 mm Hg), defined as a patient's oxygen "reserve". When used in conjunction with pulse oximetry, ORi extends the knowledge on a patient's oxygen status providing clinically important information helping to prevent hyperoxemia and hypoxemia. There are limited data on patients undergoing craniosynostosis surgery. Our primary goal was to evaluate the effects of different concentrations of inspiratory oxygen (FiO₂) on patient oxygenation status by monitoring ORi. Thirty patients scheduled for craniosynostosis were included in this observational cohort study. Patients were randomized into two equal groups: Group 1 received a fraction of inspired oxygen of 0.8 and group 2 received a FiO₂ of 0.6 during induction of anaesthesia. In addition to standard haemodynamic variables with ORi were recorded at baseline 1 min, 5 min, 60 min, and 120 min after intubation. Postoperative complications, length of stay in the intensive care unit and hospital were recorded. In total, 14 patients were evaluated in each group. Gender, age, BMI, ASA scores were similar between groups (p > 0.05). In Group 1, ORi values were significantly higher when compared to group 2 at baseline (0.86 ± 0.21 vs 0.45 ± 0.32, p = 0.001), one minute (0.61 ± 0.24 vs 0.27 ± 0.21, p = 0.001), and 5 min (0.34 ± 0.31 vs 0.10 ± 0.13, p = 0.033). High inspired oxygen concentration during induction of anesthesia in pediatric patients is associated with higher levels of ORi. Therefore, ORi may provide the means to safely reduce the inspired oxygen fraction during inhalational induction in paediatric patients.

ORi™: a new indicator of oxygenation

In the perioperative period, hypoxemia and hyperoxia are crucial factors that require attention, because they greatly affect patient prognoses. The pulse oximeter has been the only noninvasive monitor that can be used as a reference of oxygenation in current anesthetic management; however, in recent years, a new monitoring method that uses the oxygen reserve index (ORi™) has been developed by Masimo Corp. ORi is an index that reflects the state of moderate hyperoxia (partial pressure of arterial oxygen [PaO₂] between 100 and 200 mmHg) using a non-unit scale between 0.00 and 1.00. ORi monitoring performed together with percutaneous oxygen saturation (SpO₂) measurements may become an important technique in the field of anesthetic management, for measuring oxygenation reserve capacity. By measuring ORi, it is possible to predict hypoxemia and to detect hyperoxia at an early stage. In this review, we summarize the method of ORi, cautions for its use, and suitable cases for its use. In the near future, the monitoring of oxygen concentrations using ORi may become increasingly common for the management of respiratory function before, after, and during surgery.

Pathomechanisms of Non-Traumatic Acute Brain Injury in Critically Ill Patients

Delirium, an acute alteration in mental status characterized by confusion, inattention and a fluctuating level of arousal, is a common problem in critically ill patients. Delirium prolongs hospital stay and is associated with higher mortality. The pathophysiology of delirium has not been fully elucidated. Neuroinflammation and neurotransmitter imbalance seem to be the most important factors for delirium development. In this review, we present the most important pathomechanisms of delirium in critically ill patients, such as neuroinflammation, neurotransmitter imbalance, hypoxia and hyperoxia, tryptophan pathway disorders, and gut microbiota imbalance. A thorough understanding of delirium pathomechanisms is essential for effective prevention and treatment of this underestimated pathology in critically ill patients.