Oxygen Reserve Index Research Articles

Monitoring the Oxygen Reserve Index can contribute to the early detection of deterioration in blood oxygenation during one-lung ventilation.

Hypoxemia can occur during one-lung ventilation (OLV), but monitoring blood oxygenation using percutaneous oxygen saturation (SpO2) can be limited by detection latency, and SpO2 sometimes does not change during OLV. The Oxygen Reserve Index (ORi™) is a novel index reported to detect impending desaturation before this is observed with SpO2 monitoring. This study assessed whether the ORi decreased earlier than SpO2 during OLV and evaluated its correlation with the partial pressure of arterial oxygen (PaO2) during OLV. The study enrolled 15 patients undergoing elective thoracic surgery. The patient's trachea was intubated with a left-sided double-lumen endotracheal tube and the lungs were mechanically ventilated in pressure-control mode for 10 min, with the fraction of inspired oxygen set at 0.6. Right OLV was then initiated for 15 min or until SpO2 declined to 91%, while continuously recording the ORi and SpO2. PaO2 was measured 5 min before and every 3 min during OLV. Mean (SD) times from the start of OLV to the start of the decreases in ORi and SpO2 were calculated. ORi started decreasing significantly before SpO2 (ORi vs. SpO2: 171 [102] vs. 372 [231] s; P<0.01). ORi showed a significant, strong correlation with PaO2 (r2=0.671, P<0.01). ORi decreased earlier than SpO2 during OLV. This index could contribute to the early detection of deterioration in blood oxygenation during OLV.

Effects of indigo carmine intravenous injection on oxygen reserve index (ORi™) measurement.

To retrospectively investigate the effects of indigo carmine intravenous injection on oxygen reserve index (ORi™) in 20 patients who underwent elective gynecologic surgery under general anesthesia. The study subjects were patients who underwent elective gynecologic surgery under general anesthesia between April 2016 and January 2017, and were administered a 5-ml intravenous injection of 0.4% indigo carmine for clinical purposes during surgery with ORi monitoring. Changes in ORi within 20min after indigo carmine injection were observed. A relevant decrease in ORi was defined as ≥ 10% reduction in ORi from pre-injection level. ORi rapidly decreased after indigo carmine intravenous injection in all patients. In 10 of 19 patients, ORi decreased to 0 after indigo carmine injection. The median lowest value of ORi was 0 (range 0-0.16) and the median time to reach the lowest value of ORi was 2min (range 1-4min) after injection. ORi values returned to pre-injection levels within 20min in 13 of 19 patients, and the median time to return to pre-injection levels was 10min (range 6-16min) after injection. During ORi monitoring it is necessary to consider the rapid reduction in ORi after intravenous injection of indigo carmine.

Usefulness of oxygen reserve index (ORi™), a new parameter of oxygenation reserve potential, for rapid sequence induction of general anesthesia.

The oxygen reserve index (ORi™) is a new parameter for monitoring oxygen reserve noninvasively. The aim of this study was to examine the usefulness of ORi for rapid sequence induction (RSI). Twenty adult patients who were scheduled for surgical procedures under general anesthesia were enrolled. After attaching a sensor capable of measuring ORi, oxygen (6L/min) and fentanyl (2μg/kg) were administered. After 3min, propofol 2mg/kg and rocuronium 1mg/kg were administered without ventilation. Regardless of changes in ORi, tracheal intubation was performed either 2min after administration of propofol or when percutaneous oxygen saturation (SpO2) reached 98%. Ventilation was then provided with oxygen at 6L/min, and trends in ORi and SpO2 during RSI were observed. Data from 16 of the 20 patients were analyzed. Before oxygen administration, the median SpO2 was 98% [interquartile range (IQR) 97-98] and ORi was 0.00 in all patients. At 3min after starting oxygen administration, the median SpO2 was 100% (IQR 100-100) and the median ORi was 0.50 (IQR 0.42-0.57). There was an SpO2 decline of 1% or more from the peak value after propofol administration in 13 patients, and 32.5s (IQR 18.8-51.3) before the SpO2 decrease, ORi began to decline in 10 of the 13 (77%) patients. The ORi trends enable us to predict oxygenation reduction approximately 30s before SpO2 starts to decline. By monitoring ORi, the incidence related to hypoxemia during RSI could be reduced.

The Relationship Between Oxygen Reserve Index and Arterial Partial Pressure of Oxygen During Surgery.

The use of intraoperative pulse oximetry (SpO2) enhances hypoxia detection and is associated with fewer perioperative hypoxic events. However, SpO2 may be reported as 98% when arterial partial pressure of oxygen (PaO2) is as low as 70 mm Hg. Therefore, SpO2 may not provide advance warning of falling arterial oxygenation until PaO2 approaches this level. Multiwave pulse co-oximetry can provide a calculated oxygen reserve index (ORI) that may add to information from pulse oximetry when SpO2 is >98%. This study evaluates the ORI to PaO2 relationship during surgery. We studied patients undergoing scheduled surgery in which arterial catheterization and intraoperative arterial blood gas analysis were planned. Data from multiple pulse co-oximetry sensors on each patient were continuously collected and stored on a research computer. Regression analysis was used to compare ORI with PaO2 obtained from each arterial blood gas measurement and changes in ORI with changes in PaO2 from sequential measurements. Linear mixed-effects regression models for repeated measures were then used to account for within-subject correlation across the repeatedly measured PaO2 and ORI and for the unequal time intervals of PaO2 determination over elapsed surgical time. Regression plots were inspected for ORI values corresponding to PaO2 of 100 and 150 mm Hg. ORI and PaO2 were compared using mixed-effects models with a subject-specific random intercept. ORI values and PaO2 measurements were obtained from intraoperative data collected from 106 patients. Regression analysis showed that the ORI to PaO2 relationship was stronger for PaO2 to 240 mm Hg (r = 0.536) than for PaO2 over 240 mm Hg (r = 0.0016). Measured PaO2 was ≥100 mm Hg for all ORI over 0.24. Measured PaO2 was ≥150 mm Hg in 96.6% of samples when ORI was over 0.55. A random intercept variance component linear mixed-effects model for repeated measures indicated that PaO2 was significantly related to ORI (β[95% confidence interval] = 0.002 [0.0019-0.0022]; P < 0.0001). A similar analysis indicated a significant relationship between change in PaO2 and change in ORI (β [95% confidence interval] = 0.0044 [0.0040-0.0048]; P < 0.0001). These findings suggest that ORI >0.24 can distinguish PaO2 ≥100 mm Hg when SpO2 is over 98%. Similarly, ORI > 0.55 appears to be a threshold to distinguish PaO2 ≥150 mm Hg. The usefulness of these values should be evaluated prospectively. Decreases in ORI to near 0.24 may provide advance indication of falling PaO2 approaching 100 mm Hg when SpO2 is >98%. The clinical utility of interventions based on continuous ORI monitoring should be studied prospectively.

Oxygen Reserve Index: A Novel Noninvasive Measure of Oxygen Reserve--A Pilot Study.

Pulse oximetry provides no indication of downward trends in PaO2 until saturation begins to decrease. The Oxygen Reserve Index (ORI) is a novel pulse oximeter-based nondimensional index that ranges from 1 to 0 as PaO2 decreases from about 200 to 80 mmHg and is measured by optically detecting changes in SvO2 after SaO2 saturates to the maximum. The authors tested the hypothesis that the ORI provides a clinically important warning of impending desaturation in pediatric patients during induction of anesthesia. After preoxygenation, anesthesia induction, and tracheal intubation, the anesthesia circuit was disconnected and oxygen saturation was allowed to decrease to 90% before ventilation recommenced. The ORI and SpO2 values were recorded from a Masimo Pulse Co-Oximeter Sensor at the beginning of apnea, beginning and end of intubation, beginning and end of the ORI alarm, and 2 min after reoxygenation. Data from 25 healthy children, aged 7.6 ± 4.6 yr, were included in the analysis. During apnea, the ORI slowly and progressively decreased over a mean of 5.9 ± 3.1 min from 0.73 ± 0.16 at the beginning of apnea to 0.37 ± 0.11. SpO2 remained 100% throughout this initial period. Concurrently with alarm activation, the ORI began to decrease rapidly, and in median of 31.5 s (interquartile range, 19 to 34.3 s), saturation decreased to 98%. In this pilot study, the ORI detected impending desaturation in median of 31.5 s (interquartile range, 19-34.3 s) before noticeable changes in SpO2 occurred. This represents a clinically important warning time, which might give clinicians time for corrective actions.

Oxygen Reserve Index for Kids

Oxygen Reserve Index for Kids