Total Oxygenation Index Research Articles

Thoracic Spinal Manipulation Effect on Neuroendocrine Response in People With Achilles Tendinopathy: A Randomized Crossover Trial

ObjectiveThe purpose of the present study was to determine the neuroendocrine response after a thoracic spinal manipulation in people with Achilles tendinopathy. MethodsThis was a randomized 2-sequence, 2-period crossover trial. A total of 24 participants, mean (standard deviation) age of 48 (7) years, with a diagnosis of Achilles tendinopathy (>3 mo) were randomly assigned into sequence 1 (sham intervention and then thoracic spinal manipulation) or sequence 2 (thoracic spinal manipulation and then sham intervention). The trial was conducted at a university laboratory with a washout period of 1 week. The primary outcome measure was the testosterone/cortisol (T/C) ratio (salivary samples). The secondary outcome measures included heart rate variability (measured with electrocardiography) and total oxygenation index (nmol/L) of calf muscle and Achilles tendon (measured with near-infrared spectroscopy). A 2-way mixed-model analysis of variance was performed. The statistic of interest was the condition by time interaction. ResultsA statistically significant condition by time interaction was found for the T/C ratio (mean difference: –0.16; confidence interval: –0.33 to 0.006; interaction: P < .05) and the total oxygenation index (mean difference: 1.35; confidence interval: –1.3 to 4.1; interaction: P < .05) of calf muscle but not for Achilles tendon (P = .6); however, no difference was found for heart rate variability (P = .5). ConclusionIn people with Achilles tendinopathy, thoracic spinal manipulation resulted in immediate increase in the total oxygenation index in the calf muscle followed by an increase in the T/C ratio 6 hours post-intervention.

Effect of PEMF on Muscle Oxygenation during Cycling: A Single-Blind Controlled Pilot Study

Pulsed electromagnetic fields (PEMFs) are used as non-invasive tools to enhance microcirculation and tissue oxygenation, with a modulatory influence on the microvasculature. This study aimed to measure the acute effect of PEMF on muscle oxygenation and its influence on pulmonary oxygen kinetics during exercise. Eighteen male cyclists performed, on different days, a constant-load exercise in both active (ON) and inactive (OFF) PEMF stimulations while deoxyhemoglobin and pulmonary oxygen kinetics, total oxygenation index, and blood lactate were collected. PEMF enhanced muscle oxygenation, with higher values of deoxyhemoglobin both at the primary component and at the steady-state level. Moreover, PEMF accelerated deoxyhemoglobin on-transition kinetic, with a shorter time delay, time constant, and mean response time than the OFF condition. Lactate concentration was higher during stimulation. No differences were found for total oxygenation index and pulmonary oxygen kinetics. Local application of a precise PEMF stimulation can increase the rate of the muscle O2 extraction and utilization. These changes were not accompanied by faster oxygen kinetics, reduced oxygen slow component, or reduced blood lactate level. It seems that oxygen consumption is more influenced by exercise involving large muscle mass like cycling, whereas PEMF might only act at the local level.

The effects of lumbar sympathectomy on bone and soft tissue haemodynamics of the leg recorded using near infrared spectroscopy: A case report

Near infrared spectroscopy (NIRS) is an established tool for the measurement of microvascular haemodynamics in different tissue types. This case report outlines the novel use of NIRS for measuring total oxygenation index (TOI) and relative oxygenated and deoxygenated haemoglobin concentration changes as markers of oxygenation and blood volume in muscle and bone tissue. In particular, NIRS is used to examine differences between the left and right leg in a participant who has experienced a permanent unilateral lumbar sympathectomy following an anterior lumbar intervertebral fusion. Anatomical sites at the lateral head of the gastrocnemius, tibial diaphysis and proximal tibia were investigated with NIRS during an arterial occlusion protocol at the distal femur. Consistent differences were observed between the sympathectomised left leg and the normal right leg. These included reduced baseline TOI, reduced deoxygenation rates during occlusion, and reduced reoxygenation rates post occlusion release in the sympathectomised leg at all anatomical sites. This case report demonstrates the potential of NIRS as a research tool for investigating the microvascular effects of lumbar sympathectomy. This may be useful for further investigation into the merit of chemical lumbar sympathectomy for the treatment of a variety of conditions, including hyperhidrosis and peripheral vascular disease.

Postexercise orthostatic intolerance: influence of exercise intensity.

What is the central question of this study? Following exercise, hypotension is often reported and syncope is more likely. It is unresolved whether the postexercise hypotension associated with different exercise intensities contributes to the rate at which syncope develops. What is the main finding and its importance? The physiological events that induce presyncope are the same both before and after exercise; however, more intense exercise accelerated the development of hypocapnia, hypotension and, ultimately, syncope. These data indicate that higher intensity exercise induces a postexercise hypotension that reduces cardiovascular reserve, an earlier development of hypocapnia and, ultimately, cerebral hypoperfusion. After exercise, a reduction in mean arterial pressure is often experienced and is referred to as postexercise hypotension. Whilst syncope is more likely following exercise, it is unknown whether orthostatic tolerance is impacted by any exercise intensity-mediated effect on postexercise hypotension. We examined the effect of exercise intensity on time to presyncope, induced via combined head-up tilt and lower body negative pressure following 1h of cycling at 30 and 70% of heart rate range. Healthy participants (n = 8; mean±SD, 28±5 years old) completed orthostatic testing to presyncope before and after exercise. Beat-to-beat middle cerebral artery blood flow velocity (MCAv), mean arterial pressure and cerebral oxygenation (measured by near-infrared spectroscopy) were recorded continuously throughout orthostatic testing. During exercise, heart rates were 95±6 and 147±5beatsmin(-1) for 30 and 70% heart rate range, respectively, with average power outputs of 103±22 and 221±45W, respectively. Time to presyncope occurred 32% sooner after the 70% heart rate range trial (952±484 versus 1418±435s; P = 0.004). Both before and after exercise, presyncope occurred at the same reduction in MCAv (grouped mean, -30±11cms(-1) ), mean arterial pressure (-18±13mmHg), total oxygenation index (-6±2%) and partial pressure of end-tidal CO2 (-16±8mmHg; all P >0.1). At presyncope following exercise, the MCAv response was related more to the change in partial pressure of end-tidal CO2 from the baseline preceding orthostatic testing (r(2) =0.50, P=0.01) than to the hypotension (r(2) =0.12, P=0.17). Presyncope both before and after exercise occurred as a result of the same physiological perturbations, albeit greatly accelerated following more intense exercise.

Does arterial health affect VO2peak and muscle oxygenation in a sedentary cohort?

An association between arterial health and peak oxygen consumption (VO2peak) has been demonstrated; however, little is known about how arterial health influences muscular oxygenation during exercise. The aim of this study was to gain insight into the relations between arterial health, VO2peak, and muscle oxygenation in a middle-age sedentary population. Radial augmentation index (AIx) (via pulse wave analysis) of 21 sedentary middle-age participants (15 females and six males; age, 54.7 ± 5.4; body mass index, 29.0 ± 4.7 kg·m; mean ± SD) was assessed, and on another day ( < 7 d), participants completed a modified Bruce protocol (MBP). Using near-infrared spectroscopy, total oxygenation index (TOI) of the left flexor carpi ulnaris and the left vastus lateralis were monitored throughout the MBP. Independent and average (arm + leg) percentage decrease in TOI between stage 1 of the MBP and maximal exertion (TOIdiff) during MBP was calculated. Changes between dependent variables were correlated using Pearson product-moment correlations and were interpreted as follows: r > 0.5, strong; 0.5 > r > 0.3, moderate; and r < 0.3, weak. We observed moderate negative correlation between AIx and VO2peak (r = -0.34, -0.63 to -0.03; Pearson correlation, 90% confidence limits) and strong negative correlation between AIx and average TOIdiff (r = -0.58, -0.78 to -0.27). The VO2peak and average TOIdiff were strongly correlated (r = 0.55, 0.23-0.77). Arterial health seems to be an important determinant of muscle oxygenation during exercise. In turn, muscle oxygenation during exercise is strongly related to VO2peak. Developing training modalities to prioritize arterial health outcomes may be a useful way of improving VO2peak in this population.

Elevated Cerebral Blood Oxygen Extraction in Non-Transfused Sickle Cell Disease Patients

Introduction Chronic Transfusion Therapy (CTT) has been successful in decreasing stroke frequency in patients with sickle cell disease (SCD). Despite this, indication for CTT is largely based on empirical evidence and the mechanisms by which CTT protects the brain remain unclear. CTT improves oxygen carrying capacity and lowers hemoglobin S%, but the corresponding impact on cerebral blood flow(CBF), cerebral metabolic rate (CMRO2), and oxygen extraction fraction (OEF) is unknown. Understanding the impact of these competing influences in non-transfused (NT) and chronically transfused (CT) SCD patients will inform stroke prevention. Thus, we measured CBF, CMRO2, and OEF, in NT and CT patients with SCD using magnetic resonance imaging (MRI).Methods All patients were recruited with informed consent or assent and this study was approved by the CHLA IRB. Fourteen (6 NT, 8 CT) patients with SCD and 12 healthy ethnicity matched controls (CTL) were studied. Exclusion criteria included pregnancy, previous stroke, acute chest or pain crisis hospitalization within one month. Complete blood count and hemoglobin electrophoresis were performed. Arterial oxygen saturation (SaO2) was measured via peripheral pulse oximetery. CaO2 was calculated as the product of hemoglobin, SaO2 and the oxygen density of hemoglobin (1.36 ml/g). Phase contrast imaging of the carotid and vertebral arteries was used to measure global CBF. T2 Relaxation Under Spin Tagging (TRUST) was used to measured T2 relaxation of blood within the sagittal sinus. T2 relaxation was converted to SvO2 via previously validated calibration curves. OEF represented the difference of SaO2 andSvO2 divided bySaO2. CMRO2 was calculated as the product of CBF and OEF. High resolution, 3D, T1 weighted images were used for brain volume calculation using BrainSuiteñ software.Results Table 1 summarizes the results. Hemoglobin and oxygen content were well matched between transfused and non transfused SCD patients. Cerebral metabolic rate was also nearly identical in the two groups. However, CT patients exhibited 25% higher CBF than NT SCD patients, allowing them to have a normal oxygen extraction fraction ~30%. In contrast, OEF in NT SCD patients was abnormally high (37.8%), suggesting a decreased extraction reserve. Total oxygenation index (TOI) by NIRS also trended lower in NT SCD patients, consistent with the greater oxygen extraction and lower cerebral venous saturations observed. Abstract 1387. TableCTL (reference)NTCTp value (NT vs CT)Hemoglobin (g/dl)13.5 ± 1.229.7 ± 1.259.7 ± 1.05nsCaO2 (umol O2/ml)9.85 ± .996.84 ± 1.176.95 ±.71nsCMRO2 (umol O2/100g/min)193.1 ± 44.9239.7 ± 35.3238.6 ± 38.3nsCBF (ml/100g/min)70.0 ± 12.8101.5 ± 16.6127.1 ± 23.5< 0.05OEF (%)30.0 ± 7.137.8. ± 3.0629.7 ± 7.53< 0.05NIRS TOI56.0 ± 4.0948.5 ± 4.2153.5 ± 8.760.076SvO2 (%)65.6 ± 6.856.2 ± 5.267.1 ± 6.7< 0.05Discussion: Chronically transfused SCD patients achieve normal brain oxygenation metrics (SvO2, OEF, and NIRS) but require very high CBF to achieve this balance (lowering flow reserve). In contrast, NT SCD patients have smaller increases in CBF but require greater oxygen extraction to meet cerebrovascular demands (lowering extraction reserve). Hemoglobin S mediate changes in oxygen dissociation, blood viscosity, red cell deformability and microvascular damage potentially mediate these differences but their interplay is complicated and requires further study. DisclosuresCoates:novartis: Consultancy, Honoraria, Speakers Bureau; shire: Consultancy, Honoraria; apo pharma: Consultancy, Honoraria; acceleron: Consultancy, Honoraria.

Cerebral hemodynamics during graded Valsalva maneuvers.

The Valsalva maneuver (VM) produces large and abrupt changes in mean arterial pressure (MAP) that challenge cerebral blood flow and oxygenation. We examined the effect of VM intensity on middle cerebral artery blood velocity (MCAv) and cortical oxygenation responses during (phases I–III) and following (phase IV) a VM. Healthy participants (n = 20 mean ± SD: 27 ± 7 years) completed 30 and 90% of their maximal VM mouth pressure for 10 s (order randomized) whilst standing. Beat-to-beat MCAv, cerebral oxygenation (NIRS) and MAP across the different phases of the VM are reported as the difference from standing baseline. There were significant interaction (phase * intensity) effects for MCAv, total oxygenation index (TOI) and MAP (all P < 0.01). MCAv decreased during phases II and III (P < 0.01), with the greatest decrease during phase III (−5 ± 8 and −19 ± 15 cm·s−1 for 30 and 90% VM, respectively). This pattern was also evident in TOI (phase III: −1 ± 1 and −5 ± 4%, both P < 0.05). Phase IV increased MCAv (22 ± 15 and 34 ± 23 cm·s−1), MAP (15 ± 14 and 24 ± 17 mm Hg) and TOI (5 ± 6 and 7 ± 5%) relative to baseline (all P < 0.05). Cerebral autoregulation, indexed, as the %MCAv/%MAP ratio, showed a phase effect only (P < 0.001), with the least regulation during phase IV (2.4 ± 3.0 and 3.2 ± 2.9). These data illustrate that an intense VM profoundly affects cerebral hemodynamics, with a reactive hyperemia occurring during phase IV following modest ischemia during phases II and III.

Helicopter Cockpit Seat Side and Trapezius Muscle Metabolism with Night Vision Goggles

Documented neck strain among military helicopter aircrew is becoming more frequent and many militaries use helicopters that provide pilots with the option of sitting in the left or right cockpit seat during missions. The purpose of this study was to use near infrared spectroscopy (NIRS) to investigate the physiological changes in trapezius muscle oxygenation and blood volume during night vision goggle (NVG) flights as a function of left and right cockpit seating. There were 25 pilots who were monitored during NVG flight simulator missions (97.7 +/- 16.1 min). Bilateral NIRS probes attached to the trapezius muscles at C7 level recorded total oxygenation index (TOI, %), total hemoglobin (tHb), oxyhemoglobin (Hbo2), and deoxyhemo-globin (HHb). No significant differences existed between variables for pilots seated in the right cockpit seat as compared with the pilots seated in the left cockpit seat in either trapezius muscle (pTOI = 0.72; ptHb = 0.72; pHbo2 = 0.57; pHHb = 0.21). Alternating cockpit seats on successive missions is not a means to decrease metabolic stress for helicopter pilots using NVG. This suggests that cockpit layout and location of essential instruments with respect to the horizontal and the increased head supported mass of the NVG may be important factors influencing metabolic stress of the trapezius muscle.

Physiological Effects of Night Vision Goggle Counterweights on Neck Musculature of Military Helicopter Pilots

Increased helmet-mounted mass and specific neck postures have been found to be a cause of increased muscular activity and stress. However, pilots who use night vision goggles (NVG) frequently use counterweight (CW) equipment such as a lead mass that is attached to the back of the flight helmet to provide balance to counter the weight of the NVG equipment mounted to the front of the flight helmet. It is proposed that this alleviates this stress. However, no study has yet investigated the physiological effects of CW during an extended period of time during which the pilots performed normal operational tasks. Thirty-one Canadian Forces pilots were monitored on consecutive days during a day and a NVG mission in a CH-146 flight simulator. Near infrared spectroscopy probes were attached bilaterally to the trapezius muscles and hemodynamics, i.e., total oxygenation index, total hemoglobin, oxyhemoglobin, and deoxyhemoglobin, were monitored for the duration of the mission. Pilots either wore CW (n = 25) or did not wear counterweights (nCW, n = 6) as per their usual operational practice. Levene's statistical tests were conducted to test for homogeneity and only total oxygenation index returned a significant result (p < or = 0.05). For the near infrared spectroscopy variables, significant differences were found to exist between CW and nCW pilots for total hemoglobin, deoxyhemoglobin, and oxyhemoglobin during NVG flights. The CW pilots displayed less metabolic and hemodynamic stress during simulated missions as compared to the nCW pilots. The results of this study would suggest that the use of CW equipment during NVG missions in military helicopter pilots does minimize the metabolic and hemodynamic responses of the trapezius muscles.

Heart Rate and Muscle Oxygenation during Hyperbaric Hyperoxia

PURPOSE: Hyperbaric hyperoxia is known to increase oxygen concentration in arterial blood and tissue and also to decrease heart rate (HR). This study aimed to investigate the relation between muscle oxygenation and HR under the condition of hyperbaric hyperoxia (HBHO). METHODS: Three males and 4 females aged 27.1 ±4.7 yrs volunteered to participate in this investigation. Written informed consent was obtained from all subjects. They sat in the hyperbaric chamber for 60 min and breathed 1) air of normal pressure (1.0 ATA) for 10 min (baseline) and 2) 100% O2 of 1.3 ATA for 30 min. Between the two stages, the atmospheric pressure was gradually increased from 1.0 to 1.3 ATA for 10 min and decreased to 1.0 ATA for 10 min after the 2nd stage. Heart rate variability (HRV) and oxygenation of vastus lateralis were measured during each phase. Time domain (HR and SD of HRV) and frequency domain (LF/HF and HF/TOT, LF: low frequency power, HF: high frequency power, and TOT: total power) measures of HRV were calculated. The changes of oxyhemoglobin (deltaO2Hb), deoxyhemoglobin (deltaHHb) and total hemoglobin (deltacHb) as well as TOI (total oxygenation index: O2Hb/(O2Hb+HHb)) were evaluated using near-infrared spectrophotometry. Correlations between the changing rates for HRV measures and oxygenation related measures from baseline to HBHO were calculated. RESULTS: The decrease of HR and increase of TOI under HBHO were observed in all subjects. There was a significant positive correlation in the changing rates of HR and TOI. CONCLUSIONS: From the results of the present investigation, it can be said that lower oxygenation accompanied greater decrease of HR under HBHO. It might be due to individual differences in vasoconstriction which might occur in response to HBHO and which could induce the increase of venousreturn to the heart.

Cerebral oxygen balance is impaired during repair of aortic coarctation in infants and children

During repair of aortic coarctation through a left thoracotomy without cardiopulmonary bypass, clamping the proximal transverse aortic arch occludes antegrade flow to the left carotid and vertebral arteries. It is assumed that flow through the right carotid and vertebral arteries is adequate for cerebral perfusion. The study objective is to determine whether aortic occlusion impairs left hemispheric cerebral oxygen balance measured by near-infrared spectroscopy. In 18 children having repair of aortic coarctation, we measured the maximum change and integral for hemoglobin D (difference of oxyhemoglobin and deoxyhemoglobin), total oxygenation index, and the redox state of cytochrome aa3. Thirteen subjects had recordings from the left hemisphere to test the hypothesis that aortic occlusion impairs left hemispheric oxygen balance. Five subjects had recordings from the right hemisphere for comparison. After aortic clamping, a significant decrease in hemoglobin D was observed in recordings from the left hemisphere compared with those from the right hemisphere (P = .03, maximum change in hemoglobin D). Total oxygenation index and cytochrome aa3 were generally preserved. There was an inverse linear relationship for the change in hemoglobin D during clamp application and after removal (Spearman rho = -0.74), with increased hemoglobin D after clamp removal in those subjects with the greatest decrease of hemoglobin D during arch occlusion. Linear regression analysis identified nitroprusside administration as significantly associated with a decrease in hemoglobin D (P < .001). Significant impairment in left hemispheric cerebral oxygen balance was identified during arch clamping. The neurodevelopmental significance of impaired cerebral oxygen balance detected by near-infrared spectroscopy during aortic coarctation repair remains to be elucidated.