Increase In deoxy-Hb Research Articles

Regional Differences in Skeletal Muscle O2 Dynamics During Body-Weight Resistance Exercise with Slow Movement and Tonic Force Generation.

The aim of this study was to investigate the skeletal muscle O2 dynamics during body-weight resistance exercise with slow movement and tonic force generation. Thirteen untrained, healthy, young males performed Bulgarian split squats and push-ups until volitional failure. Relative changes from rest in oxygenated haemoglobin (oxy-Hb) and deoxygenated haemoglobin (deoxy-Hb) concentrations were continuously monitored at the vastus lateralis (VL) and rectus femoris (RF) muscles during squats, and pectoralis major (PM) and triceps brachii (TB) muscles during push-ups using spatial resolved near-infrared spectroscopy oximetry. During the squat exercise, deoxy-Hb continuously increased at RF until failure (10.8±7.0μmol/L), while at VL, deoxy-Hb was relatively maintained during 25-100% of the number of maximum repetitions (18.0±7.4μmol/L at volitional failure). During the push-up exercise, a significant increase in deoxy-Hb was observed during exercise from rest at PM and TB. We found a significant increase in oxy-Hb during exercise at PM (28.1±15.8μmol/L at volitional failure), while at TB, no significant difference was observed from rest (-2.7±13.7μmol/L at volitional failure). Our findings suggest that the deoxygenation patterns during body-weight squat exercise were heterogeneous within the quadriceps muscles. Moreover, differences in O2 dynamics between the trunk and extremity muscles may be partly explained by convective O2 supply during resistance exercise. However, future studies are needed due to inter-individual differences in skills for body-weight resistance exercise.

Vascular myogenic control of tibial bone blood flow in young healthy individuals

Bone health is critically dependent on adequate blood flow supplied by its extensive vascular network. Without adequate perfusion to provide oxygen and essential nutrients critical for bone metabolism, nearly all skeletal functions are compromised. However, despite the importance of blood flow to bone, regulation of bone blood flow is poorly understood in humans. The broad hypothesis of the current work is that the primary regulators of blood flow to bone are not different from other vascular beds. We have recently shown that sympathetic innervation of the bone vasculature has an active role in controlling bone blood flow in young healthy individuals. This work furthers our previous findings by investigating additional key bone blood flow regulators ‐ myogenic vasodilation and vasoconstriction. While vascular myogenic control has been investigated in soft tissue, to our knowledge there has been no research in the bone vasculature in humans, with only a handful of animal studies.In young healthy individuals (N=8), we characterized myogenic control of tibial blood flow via novel custom‐made near infrared spectroscopy (NIRS). Tibial blood flow via NIRS was measured as oxy‐, deoxy‐, and total hemoglobin (Hb). We employed reactive hyperemia and leg dependency to assess myogenic vasodilation and vasoconstriction in the whole calf and in the tibia. The magnitude of maximum myogenic vasodilation was defined by the peak reactive blood flow response to sustained ischemia. Arterial flow to the lower leg was occluded by rapidly inflating a pneumatic thigh cuff above the knee to 220 mmHg in supine subjects. Tibial blood flow was assessed via NIRS and whole leg blood flow velocity in the popliteal artery of the same leg was measured via Doppler ultrasound during 1 min of rest, 10 min of cuff inflation, and 5 min of recovery. Myogenic vasoconstriction was assessed via leg dependency, i.e., during two levels of increased transmural pressure achieved by lowering the leg below heart level. Only tibial blood flow was assessed during 5 min in supine position, 5 min in seated upright position, and 5 min in seated position with legs lowered at 90deg knee flexion.During cuff occlusion, there was a time dependent decrease in bone oxyHb accompanied by an increase in deoxyHb indicating lack of flow with continued metabolism. Tibial total Hb (sum of oxy‐ and deoxy‐Hb) did not change significantly during cuff inflation, but increased rapidly and markedly with cuff release, far surpassing baseline values when flow was restored. A similar overshoot response was seen in whole leg blood flow with cuff release. Thus, the response of tibial flow to reactive hyperemia follows the same behavior as the whole limb, indicating an active myogenic vasodilator response in bone similar to other vascular beds. During leg dependency, despite increases in arterial perfusion pressure at both levels (ΔP, 25.8 + 3.67, and 40.0 + 3.02 mmHg), there was no change in tibial flow (total Hb, ‐0.39 + 7.40, and ‐0.29 + 16.2 μM). Hence, unchanged tibial flow despite increased pressure indicates a compensatory vasoconstrictor response in the tibia. Our results indicate that similar to other vascular beds, myogenic control plays an active role in regulating the bone vasculature in young healthy individuals. Characterizing blood flow regulation in bone constitutes the basis of defining its role in overall bone health and its contribution to numerous bone loss conditions.

Physiological mechanism of increase in deoxy-hemoglobin concentration during neuronal activation in patients with cerebral ischemia: a simulation study with the balloon model.

Patients with cerebral ischemia or brain tumor have been reported to exhibit an increase of deoxygenated hemoglobin (deoxy-Hb) together with an increase of oxygenated hemoglobin (oxy-Hb). However, the physiological mechanisms underlying this hemodynamic response pattern are unclear. In this study, we performed a simulation using the balloon model (Buxton et al., Magn Reson Med 39:855-864, 1998). We hypothesized that the oxygen extraction rate during the rest period (E 0) in the patients is larger than in normal subjects, because the cerebral blood flow and the speed at which the blood passes through the brain tissues are lower in the patients. The simulation result showed an increase of deoxy-Hb as well as oxy-Hb, especially when E 0 is extremely high. Thus, the results of our simulation suggest that the increase of deoxy-Hb during activation in patients with ischemia or brain tumor is caused by an increased oxygen extraction rate at rest, compared with that of healthy adults.

337 脳血流の移流・拡散割合が組織の酸素交換へ与える影響の考察

In recent years, NIRS has been widely utilized for monitoring oxygen metabolism of human brain. Though NIRS can measure two kinds of hemoglobin, only oxy-Hb has received attention as a criterion for judgment of a brain function. Therefore, implications of changes in deoxy-Hb have not been revealed enough and have to be investigated from a physical viewpoint. In this study, numerical simulation of oxygen transport to cerebral tissue is conducted to obtain transient hemoglobin changes with different blood flow rate to short stimulations. Our numerical results suggest that increase in deoxy-Hb during stimuli shows physiological signals coming from capillaries.

Multichannel Monitoring of Cerebral Circulatory and Oxygenation Status Using Optical Topography during Deep Hypothermic Retrograde Cerebral Perfusion

In this study, we evaluated changes in the cerebral circulatory and oxygenation status during deep hypothermic total circulatory arrest (TCA) and retrograde cerebral perfusion (RCP) using optical topography, a form of multichannel near-infrared spectrophotometry, to monitor the broad area perfused by the middle cerebral artery. Seven patients underwent thoracic aortic surgery with TCA and RCP via the superior vena cava. Pressure-regulated RCP was performed under pH-stat. No postoperative neurologic complications occurred. Using optical topography, the relative changes in oxy-, deoxy-, and total hemoglobin (oxy-Hb, deoxy-Hb, total Hb) were simultaneously measured from 24 points in both hemispheres. Deoxy-Hb was used for evaluating the regional oxygenation status under RCR The values of deoxy-Hb at the beginning of RCP were regarded as the basal values, and the rate of increase in deoxy-Hb per minute (deoxy-Hb/min) was calculated at each site. Deoxy-Hb/min during TCA was also calculated. In every case, both oxy-Hb and total Hb decreased and deoxy-Hb increased during TCA. When RCP was initiated, the decrease in oxy-Hb and the increase in deoxy-Hb were attenuated. Deoxy-Hb/min was significantly lower under RCP than during TCA in all portions. There was no significant difference of deoxy-Hb/min between any portions during RCP Our results showed that the status of circulation and oxygenation might be uniform in the brain during RCP and better than that under TCA.

Evoked-cerebral blood oxygenation changes in false-negative activations in BOLD contrast functional MRI of patients with brain tumors

Blood oxygenation level dependent contrast functional MRI (BOLD-fMRI) has been used to define the functional cortices of the brain in preoperative planning for tumor removal. However, some studies have demonstrated false-negative activations in such patients. We compared the evoked-cerebral blood oxygenation (CBO) changes measured by near-infrared spectroscopy (NIRS) and activation mapping of BOLD-fMRI in 12 patients with brain tumors who had no paresis of the upper extremities. On the nonlesion side, NIRS demonstrated a decrease in deoxyhemoglobin (Deoxy-Hb) with increases in oxyhemoglobin (Oxy-Hb) and total hemoglobin (Total-Hb) during a contralateral hand grasping task in the primary sensorimotor cortex (PSMC) of all patients. On the lesion side, NIRS revealed a decrease in Deoxy-Hb in five patients (Deoxy-decrease group), and an increase in Deoxy-Hb in seven patients (Deoxy-increase group); the Oxy-Hb and Total-Hb were increased during activation in both groups, indicating the occurrence of rCBF increases in response to neuronal activation. BOLD-fMRI demonstrated clear activation areas in the PSMC on the nonlesion side of all patients and on the lesion side of the Deoxy-decrease group. However, in the Deoxy-increase group, BOLD-fMRI revealed only a small activation area or no activation on the lesion side. Intraoperative brain mapping identified the PSMC on the lesion side that was not demonstrated by BOLD-fMRI. The false-negative activations might have been caused by the atypical evoked-CBO changes (i.e. increases in Deoxy-Hb) and the software employed to calculate the activation maps, which does not regard an increase of Deoxy-Hb (i.e., a decrease in BOLD-fMRI signal) as neuronal activation.

Relationships between Force Curves and Muscle Oxygenation Kinetics during Repeated Handgrip

The purpose of this study was to clarify the kinetics of muscle oxygenation by near infrared spectroscopy (NIRS) in the phase of the decreasing force, especially the pre- and post-phases of the inflection point, during repeated rhythmic grip (RRG) of 30 grips/min(-1) for 6 minutes. The inflection point was the time at which the decreasing speed of the grip force changed markedly. It was calculated statistically from two regression lines fitted to each decreasing phase by applying a two-phase regression model. Ten healthy males performed the RRG for 6 minutes. Total Hb and Oxy-Hb decreased rapidly about 10 sec (7.0+/-5.9 sec, 9.8+/-5.4 sec, respectively) corresponding to the value decreasing by 90% MVC after the onset of gripping. Deoxy-Hb was maintained at a high value for 76.2+/-27.9 sec, corresponding to the value decreasing by 70-80% MVC. These phases are considered to be the states where oxygen was not satisfactorily supplied to the active muscles because of the obstruction of blood flow caused by an increase in the intra-muscular pressure. Deoxy-Hb decreased for 120+/-21.3 sec after reaching the highest value, and then reached an almost steady state at a higher level than the rest. After this phase, muscle oxygenation kinetics enters the state where oxygen is satisfactorily supplied to active muscles. We considered that the relationship between oxygen supply and demand differs during the initial and the latter phases in RRG. The changing phase in the decreasing speed of the grip force, namely the inflection point of the decreasing force, significantly correlated with the changing phase of the Oxy-Hb and Deoxy-Hb kinetics. The inflection point of the decreasing force seems to correspond to the phase where oxygen supply cannot meet oxygen demand and the increase of Deoxy-Hb. We infer that the pre- and post-phases of the inflection point depend on different physiological factors.

Simultaneous study of interictal EEG and near-infrared spectroscopy in a boy with epilepsy

Near-infrared spectroscopy (NIRS) is a useful non-invasive method for the diagnosis of the cerebral metabolism with epileptic foci in cases of intractable epilepsy. We examined the cerebral metabolic state of epilepsy at the interictal state using a simultaneous measurement of electroencephalograph (EEG) and an NIR system in a boy with epilepsy. The subject was a 9-year-old boy with temporal lobe epilepsy. Oxy-hemoglobin (oxy-Hb), deoxy-hemoglobin (deoxy-Hb) and regional cerebral blood volume (rCBV) were estimated using a multi-channel functional NIR (fNIR) system with 24 channels (Hitachi Medical), after obtaining informed consent. Spikes on the EEG were frequently seen on the left parietal and middle temporal area during photo stimulation at the drowsy stage. On the opposite side, spikes were occasionally seen during photo stimulation. Functional NIR findings at the same time were the following: the increase of deoxy-Hb and the slight decrease of oxy-Hb and rCBV firstly from the left middle/post-temporal surfaces, and delaying response at the opposite sides. Besides, the changes of deoxy-Hb, oxy-Hb and rCBF showed the relatively small amplitude. The appearance of the abnormal metabolic state was consistent with the EEG, as spikes became less and less frequent, we then came to the conclusion that NIRS could evaluate the real-time cerebral metabolic state of the epileptic foci, even if the clinical seizure did not occur.

No Evidence for Early Decrease in Blood Oxygenation in Rat Whisker Cortex in Response to Functional Activation

Using optical methods through a closed cranial window over the rat primary sensory cortex in chloralose/urethane-anesthetized rats we evaluated the time course of oxygen delivery and consumption in response to a physiological stimulus (whisker deflection). Independent methodological approaches (optical imaging spectroscopy, single fiber spectroscopy, oxygen-dependent phosphorescence quenching) were applied to different modes of whisker deflection (single whisker, full whisker pad). Spectroscopic data were evaluated using different algorithms (constant pathlength, differential pathlength correction). We found that whisker deflection is accompanied by a significant increase of oxygenated hemoglobin (oxy-Hb), followed by an undershoot. An early increase in deoxygenated hemoglobin (deoxy-Hb) proceeded hyperoxygenation when spectroscopic data were analyzed by constant pathlength analysis. However, correcting for the wavelength dependence of photon pathlength in brain tissue (differential pathlength correction) completely eliminated the increase in deoxy-Hb. Oxygen-dependent phosphorescence quenching did not reproducibly detect early deoxygenation. Together with recent fMRI data, our results argue against significant early deoxygenation as a universal phenomenon in functionally activated mammalian brain. Interpreted with a diffusion-limited model of oxygen delivery to brain tissue our results are compatible with coupling between neuronal activity and cerebral blood flow throughout stimulation, as postulated 110 years ago by C. Roy and C. Sherrington (1890, J. Physiol. 11:85–108).

Saccadic suppression induces focal hypooxygenation in the occipital cortex.

This study investigated how a decrease in neuronal activity affects cerebral blood oxygenation employing a paradigm of acoustically triggered saccades in complete darkness. Known from behavioral evidence as saccadic suppression, electrophysiologically it has been shown in monkeys that during saccades an attenuation of activity occurs in visual cortex neurons (Duffy and Burchfiel, 1975). In study A, using blood oxygen level-dependent (BOLD) contrast functional magnetic resonance imaging (fMRI), the authors observed signal intensity decreases bilaterally at the occipital pole during the performance of saccades at 2 Hz. In study B.1, the authors directly measured changes in deoxyhemoglobin [deoxy-Hb] and oxyhemoglobin [oxy-Hb] concentration in the occipital cortex with near-infrared spectroscopy (NIRS). Whereas a rise in [deoxy-Hb] during the performance of saccades occurred, there was a drop in [oxy-Hb]. In a second NIRS study (B.2), subjects performed saccades at different rates (1.6, 2.0, and 2.3 Hz). Here the authors found the increase in deoxy-Hb and the decrease of oxy-Hb to be dependent on the frequency of the saccades. In summary, the authors observed a focal hypooxygenation in the human visual cortex dependent on the saccade-frequency in an acoustically triggered saccades paradigm. This could be interpreted as evidence that corresponding to the focal hyperoxygenation observed in functional brain activation, caused by an excessive increase in cerebral blood flow (CBF) over the increase in CMRO2 during decreased neuronal activity CBF, is more reduced than oxygen delivery.

Language-activated cerebral blood oxygenation and hemodynamic changes of the left prefrontal cortex in poststroke aphasic patients: a near-infrared spectroscopy study.

In normal subjects, regional cerebral blood flow (rCBF) is greatly increased by neuronal activity, whereas the cerebral metabolic rate for O2 is increased only slightly. However, it is not clear what kinds of cerebral blood oxygenation and hemodynamic changes can be induced by language activities in language-relevant areas of poststroke aphasics. In the present study, we investigated the difference in the changes of cerebral blood oxygenation and hemodynamics in the left prefrontal cortex induced by language activities between normal subjects, poststroke nonaphasic patients, and nonfluent aphasic patients using near-infrared spectroscopy (NIRS). Twenty-nine participants performed speech tasks, such as confrontational naming, to evaluate changes among poststroke nonfluent (Broca's) aphasia patients (10 cases; mean+/-SEM, 56.9+/-2.2 years), age-matched normal subjects (13 cases; 50.7+/-2.2 years) and poststroke nonaphasic patients (6 cases; 52.5+/-3.9 years). The optodes of NIRS were placed over the left prefrontal cortex. We analyzed the NIRS parameter (oxyhemoglobin [oxy-Hb], deoxyhemoglobin [deoxy-Hb], and total hemoglobin [total-Hb]) changes by qualitative pattern analysis of the parameter changes and quantitative analysis of the parameter values among the groups. The most common NIRS parameter change was an increase in oxy-Hb and total-Hb, with a slight decrease or no change in deoxy-Hb in the normal subjects (5 of 13 cases, 38.5%) and the nonaphasic cerebrovascular disease (CVD) patients (3 of 6 cases, 50.0%). In contrast, the most common pattern in the aphasic patients was an increase of deoxy-Hb, with an increase of oxy-Hb and total-Hb (5 of 10 cases, 50%). However, this pattern was observed in only 3 of 13 cases (23.1%) in the normal subjects and 1 of 6 cases (16.7%) in the nonaphasic CVD patients. The mean (+/-SEM) changes of deoxy-Hb of the aphasic patients, the normal subjects, and the nonaphasic CVD patients were 0.78+/-0.29, 0.06+/-0.16, and -0.18 +/- 0.22, respectively. The statistical analysis demonstrated a significant effect for deoxy-Hb (P<0.05), with the aphasic patients differing significantly from the normal subjects and the nonaphasic CVD patients, while the 2 nonaphasic groups did not differ from each other. The present results demonstrate a multiplicity of language-activated cerebral blood oxygenation and hemodynamic changes in the left prefrontal cortex in the nonaphasic and aphasic groups. The increase of deoxy-Hb with increases of oxy-Hb and total-Hb in the aphasics during language tasks suggests that the left prefrontal cortex of the aphasics utilizes more oxygen than the nonaphasics during language tasks. Finally, functional MRI, which images the activation area in the brain by detecting the reduced concentration of deoxy-Hb during neuronal activation, should be performed on the patients with cerebral dysfunction, giving special consideration to the possible multiplicity of the rCBF and cerebral oxygen metabolism responses to functional tasks.