ORI monitoring allows a reduction of time with hyperoxia in critically ill patients: the randomized control ORI2 study

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.

The ability of Oxygen Reserve Index® to detect hyperoxia in critically ill patients

Background

Hyperoxia is associated with increased morbidity and mortality in the intensive care unit. Classical noninvasive measurements of oxygen saturation with pulse oximeters are unable to detect hyperoxia. The Oxygen Reserve Index (ORI) is a continuous noninvasive parameter provided by a multi-wave pulse oximeter that can detect hyperoxia. Primary objective was to evaluate the diagnostic accuracy of the ORI for detecting arterial oxygen tension (PaO₂) > 100 mmHg in neurocritical care patients. Secondary objectives were to test the ability of ORI to detect PaO₂ > 120 mmHg and the ability of pulse oximetry (SpO₂) to detect PaO₂ > 100 mmHg and PaO₂ > 120 mmHg.

Methods

In this single-center study, we collected ORI and arterial blood samples every 6 h for 3 consecutive days. Diagnostic performance was estimated using the area under the receiver operating characteristic curve (AUROC).

Results

There were 696 simultaneous measurements of ORI and PaO₂ in 62 patients. Considering the repeated measurements, the correlation between ORI and PaO₂ was r = 0.13. The area under the receiver operating characteristic curve (AUROC), obtained to test the ability of ORI to detect PaO₂ > 100 mmHg, was 0.567 (95% confidence interval = 0.566–0.569) with a sensitivity of 0.233 (95%CI = 0.230–0.235) and a specificity of 0.909 (95%CI = 0.907–0.910). The AUROC value obtained to test the ability of SpO₂ to detect a PaO₂ > 100 mmHg was 0.771 (95%CI = 0.770–0.773) with a sensitivity of 0.715 (95%CI = 0.712–0.718) and a specificity of 0.700 (95%CI = 0.697–0.703). The diagnostic performance of ORI and SpO₂ for detecting PaO₂ > 120 mmHg was AUROC = 0.584 (95%CI = 0.582–0.586) and 0.764 (95%CI = 0.762–0.766), respectively. The AUROC obtained for SpO₂ was significantly higher than that for ORI (p < 0.01). Diagnostic performance was not affected by sedation, norepinephrine infusion, arterial partial pressure of carbon dioxide, hemoglobin level and perfusion index.

Conclusion

In a specific population of brain-injured patients hospitalized in a neurointensive care unit, our results suggest that the ability of ORI to diagnose hyperoxia is relatively low and that SpO₂ provides better detection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01012-w.

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.

The Oxygen Reserve Index as a determinant of the necessary amount of postoperative supplemental oxygen

BACKGROUND

Although blood gas analysis (BGA) is important for supplemental oxygen titration, it is invasive, intermittent, costly, and burdensome for staff. We assessed whether the Oxygen Reserve Index (ORi™), a novel pulse oximeter-based index that reflects the partial pressure of oxygen (PaO<inf>2</inf>), could determine the amount of postoperative supplemental oxygen. We also evaluated the extent of hyperoxia and hypoxia.

METHODS

Fifty patients scheduled to undergo breast surgery were randomly assigned to receive ORi-based oxygen (group O) or conventional postoperative oxygen (group C) treatments. Postoperatively, patients were transported to the Post-Anesthesia Care Unit (PACU) and then to general wards. In group O, oxygen was administered at 4 L·min^-1 in the operation room after extubation and was decreased if the ORi was >0.00 until a continuous index of 0.00 was achieved for 30 min in the PACU and wards. In group C, oxygen was administered at 4 L·min^-1 throughout the evaluation period. BGA was performed 1 h after anesthesia induction (T0), after extubation (T1), before PACU exit (T2), and on the first postoperative morning (T3). Percutaneous oxygen saturation was measured every two seconds from 9 PM after surgery to 6 AM the next morning.

RESULTS

The supplemental oxygen amount and PaO<inf>2</inf> were significantly lower in group O than group C at T2 (1.5 [0.5-3.0] vs. 4.0 [4.0-4.0] L/min, 117.3 [26.8] vs. 170.0 [42.8] mmHg) and T3 (1.0 [0.5-3.0] vs. 4.0 [4.0-4.0] L/min, 107.5 [16.5] vs. 157.1 [28.4] mmHg; median [interquartile ranges] and mean [1 SD]; P<0.01). No patient exhibited hypoxia.

CONCLUSIONS

Based on our results, ORi might be useful to titrate postoperative oxygen supplementation.

Oxygen administration for postoperative surgical patients: a narrative review

Most postoperative surgical patients routinely receive supplemental oxygen therapy to prevent the potential development of hypoxemia due to incomplete lung re-expansion, reduced chest wall, and diaphragmatic activity caused by surgical site pain, consequences of hemodynamic impairment, and residual effects of anesthetic drugs (most notably residual neuromuscular blockade), which may result in atelectasis, ventilation–perfusion mismatch, alveolar hypoventilation, and impaired upper airway patency. Additionally, the World Health Organization guidelines for reducing surgical site infection have recommended the perioperative administration of high-dose oxygen, including during the immediate postoperative period. However, supplemental oxygen and hyperoxemia also have harmful effects on the respiratory and cardiovascular systems, with several clinical studies having reported an association between high perioperative oxygen administration and worse clinical outcomes. Recently, the increased availability of new and short-acting anesthetic drugs, comprehensive pharmacological knowledge, postoperative multimodal analgesia, and new minimally invasive surgery options could result in lower incidences of postoperative hypoxemia. Moreover, recommendations promoting high oxygen administration to prevent surgical site infections have been challenged, considering the lack of scientific investigations, and have not been widely accepted. Given the potential harmful effects of hyperoxemia, routine postoperative oxygen administration might not be recommended. Recent clinical studies have indicated that a conservative approach to oxygen therapy, where oxygen administration is titrated to achieve slightly lower oxygen levels than usual, could be safely implemented and decrease acutely ill patients’ susceptibility to hyperoxemia. Based on current evidence, appropriate monitoring, including peripheral oxygen saturation, and oxygen titration should be required during postoperative oxygen administration to avoid both hypoxemia and hyperoxemia. Future trials should therefore focus on determining the optimal oxygen target during postoperative care.