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. 2025 Feb 3;13(1):13.
doi: 10.1186/s40635-025-00722-2.

Regional cerebral oxygen saturation during initial mobilization of critically ill patients is associated with clinical outcomes: a prospective observational study

Ryota Imai  1 , Takafumi Abe  1 , Kentaro Iwata  2 , Seigo Yamaguchi  3 , Takeshi Kitai  4 , Atsuhiro Tsubaki  5
Affiliations

Regional cerebral oxygen saturation during initial mobilization of critically ill patients is associated with clinical outcomes: a prospective observational study

Ryota Imai et al. Intensive Care Med Exp. .

Abstract

Background: Vital signs help determine the safety of early mobilization in critically ill patients in intensive care units. However, none of these variables directly assess cerebral circulation. Therefore, we aimed to investigate the relationship of regional cerebral oxygen saturation (rSO2) and vital signs with in-hospital death in critically ill patients.

Methods: This prospective study included critically ill patients admitted to the Uonuma Kikan Hospital Emergency Center who received physical therapy between June 2020 and December 2022. We continuously measured rSO2 during the initial mobilization using a wearable brain near-infrared spectroscopy device. With in-hospital death as the primary endpoint, the association between rSO2 and in-hospital death was assessed in Analysis 1 to determine the rSO2 cut-off value that predicts in-hospital death. In Analysis 2, patients were categorised into survival and non-survival groups to examine the temporal changes in vital signs and rSO2 associated with postural changes during mobilization.

Results: Of the 132 eligible patients, 98 were included in Analysis 1, and 70 were included in Analysis 2. Analysis 1 demonstrated that lower premobilization rSO2 was independently associated with in-hospital death (odds ratio 0.835, 95% confidence interval 0.724-0.961, p = 0.012). Receiver operating characteristic curve analysis identified an optimal rSO2 cut-off value of 57% for predicting in-hospital death (area under the curve 0.818, sensitivity 73%, specificity 83%). Analysis 2 showed that rSO2 changes during mobilization were unrelated to changes in vital signs, suggesting rSO2 as an independent prognostic marker.

Conclusions: The results suggest that rSO2 measured during initial mobilization is associated with in-hospital death in critically ill patients.

Keywords: Critically ill patients; Early mobilization; Near-infrared spectroscopy; Regional cerebral oxygen saturation; Rehabilitation.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: This study was conducted by a research team at Uonuma Kikan Hospital, with approval from the Institutional Review Board of Uonuma Kikan Hospital (approval number 02–006) and in accordance with the Declaration of Helsinki. Informed consent was obtained from all patients or their families. Additionally, a record was created in the University Hospital Medical Information Network before data collection (record number R000040749). Consent for publication: Not applicable. Competing interests: The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Mobilization procedure. The patient first lies down in the supine position and rests. The head end of the bed is then raised to 45°. Next, the patient sits on the edge of the bed. Each step lasts for 3 min. The rSO2 values are measured continuously from the resting position until mobilization is complete. Blood pressure and transcutaneous oxygen saturation are measured at six points: at rest, during the first 1 min of EHOB45°, during the last 1 min of EHOB45°, during the first 1 min of SEB, during the last 1 min of SEB, and while lying on one’s back. The rSO2 value is calculated as the average value over 1 min at the same six points. EHOB45°: head of the bed elevated to 45°; rSO2: regional cerebral oxygen saturation; SEB: sitting on the edge of the bed
Fig. 2
Fig. 2
Patient enrolment flowchart. Between June 2020 and December 2022, 132 patients met the inclusion criteria. The head mount for NIRS did not fit well on 21 of these patients, and another patient could not remain still. Twelve more patients were excluded because they spent less than 48 h in the ICU. Finally, 98 patients were included in Analysis 1. In Analysis 2, 25 survivors were excluded because the probe slipped during mobilization, and two survivors were excluded because their mobilization was discontinued for reasons such as hypotension. One non-survivor was excluded because the probe slipped during mobilization. Thus, Analysis 2 included 60 survivors and 10 non-survivors. ICU intensive care unit, NIRS near-infrared spectroscopy
Fig. 3
Fig. 3
Receiver operating characteristic curve analysis for in-hospital death. The rSO2 cut-off value for predicting in-hospital death is 57% (specificity, 0.83; sensitivity, 0.73; AUC, 0.82; 95% CI 0.715–0.922). The filled circle on the curve indicates the cut-off value. AUC area under the curve, CI confidence interval, rSO2 regional cerebral oxygen saturation
Fig. 4
Fig. 4
Temporal changes in vital signs and regional cerebral oxygen saturation. a HR is highest at SEB first minute (survivors: 89 ± 14 bpm, non-survivors: 90 ± 24 bpm). This change is significant (p < 0.001). b SBP does not change significantly with position. c DBP is highest during the first minute of SEB (survivors, 71 ± 18 mmHg; non-survivors, 70 ± 9 mmHg). This change is significant (p < 0.001). d MAP is highest during the last minute of SEB (survivors, 90 ± 19 mmHg; non-survivors, 83 ± 13 mmHg). This change is significant (p = 0.021). e SpO2 does not change significantly with position. f rSO2 is lowest at SEB first minute (survivors, 58% ± 5%; non-survivors, 54 ± 3 mmHg). This change is significant (p < 0.001). The rSO2 values of the two study groups were also significantly different at this time point (p = 0.011). DBP: diastolic blood pressure; EHOB45°: head of the bed elevated to 45°; HR: heart rate; MAP: mean arterial pressure; rSO2: regional cerebral oxygen saturation; SBP: systolic blood pressure; SEB: sitting on the edge of the bed; SpO2: transcutaneous arterial oxygen saturation
Fig. 4
Fig. 4
Temporal changes in vital signs and regional cerebral oxygen saturation. a HR is highest at SEB first minute (survivors: 89 ± 14 bpm, non-survivors: 90 ± 24 bpm). This change is significant (p < 0.001). b SBP does not change significantly with position. c DBP is highest during the first minute of SEB (survivors, 71 ± 18 mmHg; non-survivors, 70 ± 9 mmHg). This change is significant (p < 0.001). d MAP is highest during the last minute of SEB (survivors, 90 ± 19 mmHg; non-survivors, 83 ± 13 mmHg). This change is significant (p = 0.021). e SpO2 does not change significantly with position. f rSO2 is lowest at SEB first minute (survivors, 58% ± 5%; non-survivors, 54 ± 3 mmHg). This change is significant (p < 0.001). The rSO2 values of the two study groups were also significantly different at this time point (p = 0.011). DBP: diastolic blood pressure; EHOB45°: head of the bed elevated to 45°; HR: heart rate; MAP: mean arterial pressure; rSO2: regional cerebral oxygen saturation; SBP: systolic blood pressure; SEB: sitting on the edge of the bed; SpO2: transcutaneous arterial oxygen saturation
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