Bedside assessment of tissue oxygen saturation monitoring in critically ill adults: an integrative review of the literature

Validation of a Novel Noninvasive Technology to Estimate Blood Oxygen Saturation Using Green Light: Observational Study

BACKGROUND

Pulse oximeters work within the red-infrared wavelengths. Therefore, these oximeters produce erratic results in dark-skinned subjects and in subjects with cold extremities. Pulse oximetry is routinely performed in patients with fever; however, an elevation in body temperature decreases the affinity of hemoglobin for oxygen, causing a drop in oxygen saturation or oxyhemoglobin concentrations.

OBJECTIVE

We aimed to determine whether our new investigational device, the Shani device or SH1 (US Patent 11191460), detects a drop in oxygen saturation or a decrease in oxyhemoglobin concentrations.

METHODS

An observational study (phase 1) was performed in two separate groups to validate measurements of hemoglobin and oxygen concentrations, including 39 participants recruited among current university students and staff aged 20-40 years. All volunteers completed baseline readings using the SH1 device and the commercially available Food and Drug Administration-approved pulse oximeter Masimo. SH1 uses two light-emitting diodes in which the emitted wavelengths match with absorption peaks of oxyhemoglobin (hemoglobin combined with oxygen) and deoxyhemoglobin (hemoglobin without oxygen or reduced hemoglobin). Total hemoglobin was calculated as the sum of oxyhemoglobin and deoxyhemoglobin. Subsequently, 16 subjects completed the "heat jacket study" and the others completed the "blood donation study." Masimo was consistently used on the finger for comparison. The melanin level was accounted for using the von Luschan skin color scale (VLS) and a specifically designed algorithm. We here focus on the results of the heat jacket study, in which the subject wore a double-layered heated jacket and pair of trousers including a network of polythene tubules along with an inlet and outlet. Warm water was circulated to increase the body temperature by 0.5-0.8 °C above the baseline body temperature. We expected a slight drop in oxyhemoglobin concentrations in the heating phase at the tissue level.

RESULTS

The mean age of the participants was 24.1 (SD 0.8) years. The skin tone varied from 12 to 36 on the VLS, representing a uniform distribution with one-third of the participants having fair skin, brown skin, and dark skin, respectively. Using a specific algorithm and software, the reflection ratio for oxyhemoglobin was displayed on the screen of the device along with direct hemoglobin values. The SH1 device picked up more minor changes in oxyhemoglobin levels after a change in body temperature compared to the pulse oximeter, with a maximum drop in oxyhemoglobin concentration detected of 6.5% and 2.54%, respectively.

CONCLUSIONS

Our new investigational device SH1 measures oxygen saturation at the tissue level by reflectance spectroscopy using green wavelengths. This device fared well regardless of skin color. This device can thus eliminate racial disparity in these key biomarker assessments. Moreover, since the light is shone on the wrist, SH1 can be readily miniaturized into a wearable device.

Diagnostic value of intravenous oxygen saturation compared with arterial and venous base excess to predict hemorrhagic shock in multiple trauma patients

Introduction:

In this study, with the help of peripheral vein sampling, Spvo2, and peripheral artery and vein sampling, we examined base excess (BE) in trauma patients and determined its diagnostic value for hemorrhagic shock.

Methods:

In this cross-sectional study, from 64 patients with abdominal, pelvic and chest Blunt trauma who have a score of 2 or higher trauma during treatment, blood samples were taken from peripheral vein to measure oxygen saturation and peripheral vein and artery for BE measurements and were compared in order to assess their diagnostic value in predicting the occurrence of hemorrhagic shock.

Results:

Out of 60 examined patients, 43 (71.67%) patients were diagnosed with hemorrhagic shock. The correlation for the percentage of oxygen saturation of the peripheral blood and the rate of arterial and venous BE for these r^2patients were 17.0 and 09.0, respectively, with a P value greater than 0.005. In the case of the percentage of oxygen saturation of the peripheral blood, the sensitivity and specificity were 93.03 and 11.76%, respectively. The positive and negative likelihood ratios were 1.05 and 0.59, respectively. The positive and negative predictive values were 72.73 and 40%, respectively.

Conclusion:

In general, the results of this study showed that arterial and venous excess base levels had a proper correlation, specificity and sensitivity for diagnosing and predicting hemorrhagic shock, while the percentage of oxygen saturation of peripheral blood and BE arterial and venous levels had not proper correlation to detect and predict hemorrhagic shock.

Accurate Image-guided (Re)Placement of NIRS Probes

BACKGROUND AND OBJECTIVE

Functional near-infrared spectroscopy (fNIRS) has become an attractive choice to neuroscience because of its high temporal resolution, ease of use, non-invasiveness, and affordability. With the advent of wearable fNIRS technology, on-the-spot studies of brain function have become viable. However, the lack of within-subject reproducibility is one of the barriers to the full acceptability of fNIRS. To support the validation of the claim that within-subject reproducibility of fNIRS could benefit from accurate anatomical information, we present in this paper a method to develop an image-based system that improves the placement of the sensors on the scalp at interactive rates.

METHODS

The proposed solution consists of an electromagnetic digitizer and an interactive visualization system that allows monitoring the movements of the digitizer on a real head with respect to the underlying cerebral cortical structures. GPU-based volume raycasting rendering is applied to unveil these structures from the corresponding magnetic resonance imaging volume. Scalp and cortical surface are estimated from the scanned volume to improve depth perception. An alignment algorithm between the real and scanned heads is devised to visually feedback the position of the stylus of the digitizer. Off-screen rendering of the depthmaps of the visible surfaces makes spatial positioning of a 2D interaction pointer possible.

RESULTS

We evaluated the alignment accuracy using four to eight anatomical landmarks and found seven to be a good compromise between precision and efficiency. Next, we evaluated reproducibility in positioning five arbitrarily chosen points on three volunteers by four operators over five sessions. In every session, seven anatomical landmarks were applied in the alignment of the real and the scanned head. For the same volunteer, one-way analysis of variance (ANOVA) revealed no significant differences within the five points digitized by the same operator over five sessions (α = 0.05). In addition, preliminary study of motor cortex activation by right-hand finger tapping showed the potential of our approach to increase functional fNIRS reproducibility.

CONCLUSIONS

Results of experiments suggest that the enhancement of the visualization of the location of the probes on the scalp, relative to the underlying cortical structures, improves reproducibility of fNIRS measurements. As further work, we plan to study the fNIRS reproducibility in other cortical regions and in clinical settings using the proposed system.

Near-Infrared Spectroscopy: The New Must Have Tool in the Intensive Care Unit?

Standard hemodynamic monitoring such as blood pressure and pulse oximetry may only provide a crude estimation of organ perfusion in the critical care setting. Near-infrared spectroscopy (NIRS) is based on the same principle as a pulse oximeter and allows continuous noninvasive monitoring of hemoglobin oxygenation and deoxygenation and thus tissue saturation "StO2" This review aims to provide an overview of NIRS technology principles and discuss its current clinical use in the critical care setting. The study selection was performed using the PubMed database to find studies that investigated the use of NIRS in both the critical care setting and in the intensive care unit. Currently, NIRS in the critical care setting is predominantly being used for infants and neonates. A number of studies in the past decade have shown promising results for the use of NIRS in surgical/trauma intensive care units during shock management as a prognostic tool and in guiding resuscitation. It is evident that over the past 2 decades, NIRS has gone from being a laboratory fascination to an actively employed clinical tool. Even though the benefit of routine use of this technology to achieve better outcomes is still questionable, the fact that NIRS is a low-cost, noninvasive monitoring modality improves the attractiveness of the technology. However, more research may be warranted before recommending its routine use in the critical care setting.

An integrative review of literature on determinants of nurses' organizational commitment

Background:

This integrative review was aimed to examine in literature and integrate the determinants of nurses’ organizational commitment in hospital settings.

Materials and Methods:

In this study, an integrative review of the literature was used. The search strategy began with six electronic databases (e.g. CINAHL and Medline). Considering the inclusion criteria, published studies that examined the factors influencing nurses’ organizational commitment in the timeframe of 2000 through 2013 were chosen. Data extraction and analysis were completed on all included studies. The final sample for this integrative review comprised 33 studies.

Results:

Based on common meanings and central issues, 63 different factors contributing to nurses’ organizational commitment were integrated and grouped into four main categories: Personal characteristics and traits of nurses, leadership and management style and behavior, perception of organizational context, and characteristics of job and work environment.

Conclusions:

In general, categories emerged in this study could be useful for formulating initiatives to stimulate nurses’ OC. However, little is known about the relative significance of each identified factor among nurses working in different countries. Qualitative research is recommended for narrowing this gap. Future research should be directed to examine the psychometric properties of the organizational scales for nurses in different cultures.