Dynamic Changes In Oxygenation Research Articles

Regional analysis of cerebral hemodynamic changes during the head-up tilt test in Parkinson's disease patients with orthostatic intolerance.

.Significance: Cerebral oxygenation changes in the superior, middle, and medial gyri were used to elucidate spatial impairments of autonomic hemodynamic recovery during the head-up tilt table test (HUTT) in Parkinson’s disease (PD) patients with orthostatic intolerance (OI) symptoms.Aim: To analyze dynamic oxygenation changes during the HUTT and classify PD patients with OI symptoms using clinical and oxygenation features.Approach: Thirty-nine PD patients with OI symptoms [10: orthostatic hypotension (PD-OH); 29: normal HUTT results (PD-NOR)] and seven healthy controls (HCs) were recruited. Prefrontal oxyhemoglobin (HbO) changes during the HUTT were reconstructed with diffuse optical tomography and segmented using the automated anatomical labeling system. Decision trees were used for classification.Results: HCs and PD-NOR patients with positive rates of HbO change (PD-POS) showed the greatest HbO recovery in the superior frontal gyrus (SFG) during tilt. PD-OH and PD-NOR patients with negative rates of HbO change (PD-NEG) showed asymmetric reoxygenation. The classification accuracy was 89.4% for PD-POS versus PD-NEG, 71% for PD-NOR versus PD-OH, and 55.8% for PD-POS versus PD-NEG versus PD-OH. The oxygenation features were more discriminative than the clinical features.Conclusions: PD-OH showed decreased right SFG function, which may be associated with impaired compensatory autonomic responses to orthostatic stress.

Dynamic time domain near-infrared optical tomography based on a SPAD camera.

In many clinical applications it is relevant to observe dynamic changes in oxygenation. Therefore the ability of dynamic imaging with time domain (TD) near-infrared optical tomography (NIROT) will be important. But fast imaging is a challenge. The data acquisition of our handheld TD NIROT system based on single photon avalanche diode (SPAD) camera and 11 light sources was consequently accelerated. We tested the system on a diffusive medium simulating tissue with a moving object embedded. With 3D image reconstruction, the moving object was correctly located using only 0.2 s exposure time per source.

Dynamic changes in oxygenation of intracranial tumor and contralateral brain during tumor growth and carbogen breathing: A multisite EPR oximetry with implantable resonators

Introduction Several techniques currently exist for measuring tissue oxygen; however technical difficulties have limited their usefulness and general application. We report a recently developed electron paramagnetic resonance (EPR) oximetry approach with multiple probe implantable resonators (IRs) that allow repeated measurements of oxygen in tissue at depths of greater than 10 mm. Methods The EPR signal to noise ( S/ N) ratio of two probe IRs was compared with that of LiPc deposits. The feasibility of intracranial tissue pO 2 measurements by EPR oximetry using IRs was tested in normal rats and rats bearing intracerebral F98 tumors. The dynamic changes in the tissue pO 2 were assessed during repeated hyperoxia with carbogen breathing. Results A 6–10 times increase in the S/ N ratio was observed with IRs as compared to LiPc deposits. The mean brain pO 2 of normal rats was stable and increased significantly during carbogen inhalation in experiments repeated for 3 months. The pO 2 of F98 glioma declined gradually, while the pO 2 of contralateral brain essentially remained the same. Although a significant increase in the glioma pO 2 was observed during carbogen inhalation, this effect declined in experiments repeated over days. Conclusion EPR oximetry with IRs provides a significant increase in S/ N ratio. The ability to repeatedly assess orthotopic glioma pO 2 is likely to play a vital role in understanding the dynamics of tissue pO 2 during tumor growth and therapies designed to modulate tumor hypoxia. This information could then be used to optimize chemoradiation by scheduling treatments at times of increased glioma oxygenation.

Assessing pH and oxygenation in cryotherapy-induced cytotoxicity and tissue response to freezing.

The microenvironmental pH and oxygenation is known to influence tumor cell response to heat, radiation, photodynamic and even chemotherapy. We have studied the previously untested influence of acidity and hypoxia on tumor and endothelial cell sensitivity to freezing. In addition, we have measured changes in oxygenation in vivo in murine FSaII fibrosarcomas after freeze injury. A low pH or low oxygenation environment was found to increase the sensitivity of tumor and endothelial cells to freezing at -20 degrees C or -40 degrees C in vitro. However, low pH and low oxygenation combined did not further increase cryosensitivity of the cells. In vivo, tumor oxygenation after freeze injury was studied immediately or 1-3 days after a standard freezing protocol was applied to FSaII tumors ranging from 250-500 mm3 grown in the rear-limb of C3H mice. Tumor oxygenation at the edge of the iceball was found to transiently increase 1-2 hours after freezing. At 1-3 days after freezing, a treatment that delayed FSaII tumor growth by approximately 1.5-fold, the mean tumor oxygenation was significantly increased by up to 2.5-fold from a control level of 5 mmHg partial pressure of oxygen (pO2), especially at the periphery of the tumor. We conclude that manipulation of pH or oxygenation has potential to increase the anti-tumor effects of minimally invasive cryosurgical techniques. Furthermore, the dynamic changes in oxygenation after freeze injury in vivo suggests value in combining cryotherapy with treatments dependent on oxygenation levels. Ultimately, these may be routes to more reliable treatment response with fewer recurrences.

Continuous Intra-arterial Blood Gas Monitoring in Patients Undergoing Suprarenal Aortic Surgery

The authors used an on-line, real-time, continuous blood gas monitor in 5 patients undergoing elective suprarenal aortic reconstruction. They retrospectively analyzed data to evaluate its utility in acid-base management and in detection of dynamic changes in oxygenation. Seven sets of data were analyzed since 1 patient underwent two additional periods of aortic crossclamping. A similar group of 7 patients undergoing elective suprarenal aortic surgery without continuous blood gas monitoring was analyzed and served as a control group. There was a highly significant mean decrease in partial pressure of oxygen (P02) of 158 mm Hg (P = 0.0060) with unclamping. In 1 patient the P02 dropped from 218 to 63 mm Hg within sixty seconds of unclamping, and this required immediate reinstitution of two-lung ventilation. Continuous availability of pH permitted accurate therapy with bicarbonate infusion during clamping. As a result there was no significant change in pH between preclamp and immediately after unclamping (P = 0.97). In the control group the pH decreased from a mean of 7.38 to a mean of 7.24 (P = 0.0005) between preclamp and after unclamping. In summary, dynamic changes in oxygenation and pH are observed during suprarenal aortic surgery. Continuous blood gas monitoring provided data resulting in improved management of acid-base status and early detection of significant decreases in oxygenation.