Low Oxygen Air Research Articles

Enhanced motor learning and motor savings after acute intermittent hypoxia are associated with a reduction in metabolic cost.

Breathing mild bouts of low oxygen air (i.e. acute intermittent hypoxia, AIH) has been shown to improve locomotor function in humans after a spinal cord injury. How AIH-induced gains in motor performance are achieved remains unclear. We examined the hypothesis that AIH augments motor learning and motor retention during a locomotor adaptation task. We further hypothesized that gains in motor learning and retention will be associated with reductions in net metabolic power, consistent with the acquisition of energetically favourable mechanics. Thirty healthy individuals were randomly allocated into either a control group or an AIH group. We utilized a split-belt treadmill to characterize adaptations to an unexpected belt speed perturbation of equal magnitude during an initial exposure and a second exposure. Adaptation was characterized by changes in spatiotemporal step asymmetry, anterior-posterior force asymmetry, and net metabolic power. While both groups adapted by reducing spatial asymmetry, only the AIH group achieved significant reductions in double support time asymmetry and propulsive force asymmetry during both the initial and the second exposures to the belt speed perturbation. Net metabolic power was also significantly lower in the AIH group, with significant reductions from the initial perturbation exposure to the second. These results provide the first evidence that AIH mediates improvements in both motor learning and retention. Further, our results suggest that reductions in net metabolic power continue to be optimized upon subsequent learning and are driven by more energetically favourable temporal coordination strategies. Our observation that AIH facilitates motor learning and retention can be leveraged to design rehabilitation interventions that promote functional recovery. KEY POINTS: Brief exposures to low oxygen air, known as acute intermittent hypoxia (AIH), improves locomotor function in humans after a spinal cord injury, but it remains unclear how gains in motor performance are achieved. In this study, we tested the hypothesis that AIH induces enhancements in motor learning and retention by quantifying changes in interlimb coordination, anterior-posterior force symmetry and metabolic cost during a locomotor adaptation task. We show the first evidence that AIH improves both motor learning and savings of newly learned temporal interlimb coordination strategies and force asymmetry compared to untreated individuals. We further demonstrate that AIH elicits greater reductions in metabolic cost during motor learning that continues to be optimized upon subsequent learning. Our findings suggest that AIH-induced gains in locomotor performance are facilitated by enhancements in motor learning and retention of more energetically favourable coordination strategies.

Looking at the bigger PICture: understanding and counteracting the decline of persistent inward currents in older adults.

Looking at the bigger PICture: understanding and counteracting the decline of persistent inward currents in older adults.

Radioprotective Effects on Late Third-Instar Bactrocera dorsalis (Diptera: Tephritidae) Larvae in Low-Oxygen Atmospheres.

Simple SummaryThe oriental fruit fly Bactrocera dorsalis Hendel is a highly invasive fruit fly that causes extensive damage to many fruits and vegetables. Irradiation treatment is an economically effective and promising treatment measure. However, treatment efficacy is affected by the presence of low oxygen, i.e., mangoes are treated in modified atmosphere package. In order to investigate the reduced (radioprotective) effects on insects and determine its critical O2 level, third-instar B. dorsalis larvae were irradiated by X-rays at the doses of 8 to 64 Gy with intervals of 8 Gy. The treatments were conducted under ambient air or low-oxygen atomospheres (0%, 2%, 4%, 6%, 8% O2 and nitrogen). No adult emergence from treatments at 64 Gy in pure nitrogen or 56 Gy under other atmospheres, resulted in significant difference in tolerance. The results from statistical analyses indicate that differences in tolerance to radiation were significant in 0% and 2% O2 but insignificant in 4%, 6%, and 8% O2 environments when compared with radiation in ambient air. Therefore, the critical threshold is an O2 level of ≥4% and <6%, but a maximum radiation dose of 14 Gy can compensate for the radioprotective effects when the oriental fruit fly is treated in low-oxygen atmospheres.Ionizing radiation creates free radicals, the effect of which is enhanced by the presence of oxygen; a low oxygen level produces radioprotective effects for insects compared with irradiation in ambient air. Modified (controlled) atmosphere packaging is used for maintaining quality and shelf-life extension; therefore, treatment efficacy may be affected, and there is a need to determine the critical O2 levels that may cause radioprotective effects. Late third-instar Bactrocera dorsalis (Hendel) larvae were irradiated in bags filled with ambient or low-oxygen air (0%, 2%, 4%, 6%, 8% O2) and were exposed to radiation doses of 8 to 64 Gy with intervals of 8 Gy. Efficacy was measured by the prevention of adult emergence. Dose–response data on mortality (failure of adult emergence) were analyzed via two-way ANOVA (analysis of variance), ANCOVA (analysis of covariance), and probit regression. The difference in radiotolerance was only significant in 0% O2 atmospheres through two-way ANOVA; therefore, the 95% confidence limits (CLs) of lethal dose ratios at LD99 were used to determine significant differences between treatments at different O2 levels. The differences in radiotolerance were significant in 0% and 2% O2 but insignificant in 4%, 6%, and 8% O2 environments when compared with radiation in ambient air. The critical threshold of radioprotective effects for late third-instar B. dorsalis larvae is an O2 level of ≥4% and <6%, but a maximum radiation dose of 14 Gy can compensate for this effect during phytosanitary irradiation treatment.

High flow oxygen for dyspnea in hospitalized patients with cancer: A 4x4 crossover randomized clinical trial.

12077 Background: Dyspnea is common in hospitalized cancer patients and highly distressing. High flow oxygen (HFOx) is administered for oxygenation in this setting; however, its effect on dyspnea has not been well examined, particularly among non-hypoxemic patients. In this phase II trial, we assessed the effect of HFOx, high flow air (HFAir), low flow oxygen (LFOx) and low flow air (LFAir) on dyspnea. We hypothesized that HFO and HFA can alleviate dyspnea. Methods: This double-blind, 4x4 crossover clinical trial enrolled hospitalized patients with cancer who were dyspneic (NRS ≥3 at rest) and non-hypoxemic (SpO2&gt;90% on room air). Patients were randomized to 10 minutes of HFOx, HFAir, LFOx and LFAir in different orders. The flow rate was titrated between 20-60 L/min in the high flow groups and 2 L/min in the low flow groups. The primary outcome was dyspnea 0-10 numeric rating scale (NRS) “now”, where 0=none and 10=worst. Secondary outcomes included modified Borg scale dyspnea intensity and unpleasantness, adverse effects, and overall preference. We compared among the interventions with a linear mixed model adjusting for time, treatment effect, period effect and carryover effect. Results: 17 patients completed 55 interventions in a random order. Mean age 51, 58% female, mean baseline dyspnea NRS 6.3 (SD 1.7). The absolute change of dyspnea NRS between 0 and 10 minutes was -1.8 (SD 1.7) for HFOx, -1.8 (2.0) for HFAir, -0.5 (0.8) for LFOx and -0.6 (1.2) for LFAir. In mixed model analysis, HFOx group provided greater dyspnea relief than LFOx (mean difference [95% CI] -0.80 [-1.45, -0.15], P=0.02) and LFAir (-1.24 [-1.90, -0.57], P&lt;0.001). HFAir also provided a significantly greater dyspnea relief than LFOx (-0.95 [-1.61, -0.30], P=0.005) and LFAir (-1.39 [-2.05, -0.73], P&lt;0.001). No difference was found between HFOx and HFAir nor between LFOx and LFAir. There was no significant carryover effect. Dyspnea Borg scale intensity and unpleasantness showed similar changes. Oxygen saturation increased in the HFOx group (97.2% to 99.7%) and LFOx group (95.5% to 98.2%) but not HFAir nor LFAir groups. HFOx was well tolerated. At the end of the study, 7 (54%), 4 (31%), 1 (8%) and 1 (8%) patients blindly preferred HFOx, HFAir, LFOx and LFAir, respectively. Conclusions: For the first time, we found that HFOx and HFAir provided a rapid and clinically significant reduction of dyspnea at rest in hospitalized cancer patients even when they were non-hypoxemic, supporting a role for high flow devices to provide palliation beyond oxygenation. Larger studies are needed to confirm these findings. Clinical trial information: NCT02932332 .

Enhanced oil recovery mechanism of low oxygen air injection in high water cut reservoir

Whether air injection can extract additional oil in high water cut reservoirs is a big question. In this paper, long-core displacement experiment has been carried out to investigate the potential of low oxygen air flooding in high water cut reservoirs. Results indicate that implementing low oxygen air injection has potential to improve oil recovery in high water cut light oil reservoir. The reservoir with higher matrix permeability and or lower reservoir permeability contrast ratio is desirable to achieve higher oil recovery factor. In addition, the oil recovery factor for water/gas alternate injection (WAG) strategy is higher than that of continuous low oxygen air flooding. And the WAG strategy has the ability to delay gas breakthrough compared with the strategy of continuous low oxygen air injection under same experiment condition.

Abstract B31: NOX2 generated reactive oxygen species promotes glioblastoma growth through inhibition of PTEN

Abstract The tumor suppressor protein Phosphatase and Tensin Homolog (PTEN) is a negative regulator of the Akt pathway which promotes proliferation, migration, and self-renewal. PTEN is mutated or deleted in ~40% of glioblastoma (GBM) resulting in increased Akt activity; however almost all GBM's have increased Akt activity, regardless of PTEN status. This raises the possibility that GBM may inactivate PTEN through means other than mutation or deletion. Treatment with exogenous reactive oxygen species (ROS), like hydrogen peroxide, inactivates PTEN through oxidation in the phosphatase domain. The low oxygen environment of tumors (1%O2) increases ROS levels as compared to normal body tissue (4% O2), and tissue culture conditions (20% O2). Recent data indicate that low to moderate levels of ROS are required for cell maintenance and stem cell renewal while moderate increases in ROS may promote migration, invasion, and proliferation. Indeed, our lab recently found that normal neural stem cells have higher ROS levels, which is required for stem cell renewal. Moreover, data from our lab and others, have found that growing cells under physiological oxygen levels increases ROS and promotes renewal and proliferation. This suggests that the low-oxygen environment of tumors may promote proliferation and tumorigenesis through post-translational modification of proteins, like PTEN. NADPH oxidase (NOX) is a membrane bound complex of proteins that produces a significant amount of endogenous intracellular ROS. While this protein was originally identified in macrophages as being important for immune surveillance, new data suggests that the family of NOX proteins (1-4) has many other biological functions in a variety of different cell types. New data has found that the constitutively active NOX4 acts as an oncogene in several different cancer types by promoting migration, invasion, and proliferation. Within the brain, NOX2 promotes ROS-induced stem cell renewal in normal neural stem cells. Additionally, increased NOX2 expression in GBM patients correlates with shorter survival, while patients with low NOX2 expression generally live longer. Together these data suggest that, through NOX2, the low-oxygen environment of GBM increases ROS levels that oxidize and inhibit PTEN. This novel post-translational modification may increase proliferation and promote tumorigenicity through activation of Akt in cells with intact PTEN. We examined endogenous ROS levels in patient-derived GBM samples and found that increased ROS correlated with faster proliferating cells. Furthermore, low levels of O2 (1%) increased proliferation and Akt activation in a PTEN dependent manner. Both PTEN null and knockdown cells showed no increase in either proliferation or Akt activation over cells grown at room air (20%). Moreover, pharmacological inhibition of Akt abrogated ROS-induced proliferation, suggesting this mechanism functions through the PTEN/Akt pathway. This response was due directly to ROS production, as treatment with antioxidants decreased both ROS production and proliferation at low oxygen and room air. Additionally, we found that growth at 1% O2 led to the oxidation and inhibition of PTEN as seen by Akt phosphorylation. Treatment with apocynin, a NOX2 inhibitor decreased ROS production, proliferation, and Akt phosphorylation, suggesting that ROS-induced proliferation may be mediated through the NOX2 protein. This data not only show PTEN oxidation and inhibition under physiological conditions for the first time, it suggests that the low-oxygen tumor microenvironment may alter PTEN positive GBM to up-regulate the Akt pathway and promote tumorigenesis. Citation Format: Kirsten Ludwig, Harley Kornblum. NOX2 generated reactive oxygen species promotes glioblastoma growth through inhibition of PTEN. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr B31.

Study on the Basic Characteristics of Low Oxygen Air Combustion with Natural Gas in Glass Tempering Furnace

The basic characteristics of natural gas with low oxygen air combustion is analyzed, and low oxygen content, excess air ratio, and the change of flue gas composition are studied, the results show that using the technology of low oxygen air combustion for glass tempering furnace in production has directive significance. The composition content of carbon dioxide and water vapor increases in the combustion products. The radiation heat transfer is decreased in glass tempering furnace. The furnace temperatures are maintained in the range of 650 to 800°C.

Central modulation of arterial chemo‐baroreflex control by propofol during severe arterial hypoxia in the rabbit

During hypoxia specific deficits in neural control caused by propofol (2,6‐diisopropylphenol) anesthesia (Prop) are unknown. Dose‐related effects were analysed in rabbits with and without carotid body denervation (CBD) to partition arterial chemo‐baroreflex control. Minute ventilation (VE), tidal volume (VT), respiratory frequency (f), heart rate (HR), mean arterial pressure (MAP) were measured in 12 awake rabbits mask‐breathing room air, then 15 minutes of low oxygen air (PaO2 &lt; 35 mm Hg), during Prop alone (0.2 and 0.5 mg kg−1min−1i.v.), and during matched Prop plus hypoxia. Prop alone caused dose‐related depression in f and rise in HR. Prop plus hypoxia abolished bradycardia, while MAP, VE and VT effects remained intact. CBD eliminated all chemoreflex responses to hypoxia and MAP fell while HR rose, effects enhanced by Prop in a dose‐related way. It is concluded that during Prop, carotid body function for respiratory and MAP defense is functionally intact. Central activation of the vagus is inhibited selectively, because electrical stimulation of peripheral vagus during Prop evokes normal bradycardia blocked by atropine. By contrast, Prop inhibits arterial baroreflex‐vagosympathetic defense against widespread hypoxic vasodilatation. We speculate that the data reflect dominant central GABAA receptor agonist effects on the arterial chemo‐baroreflex arc. Funding: ANZCA and HMRI.

Modelling of the optimum harvest time for long-term storage of ‘Elstar’ and ‘Aroma’ (Malus domestica) apples at low oxygen concentration

Research evaluated modelling of optimum harvest time for long-term storage of ‘Aroma’ and ‘Elstar’ apples at 1 °C in three low-oxygen air compositions: (1) 1.5/1.5% O2/CO2 throughout the storage period; (2) 0.25/0.25% O2/CO2 for seven days, and then at 1.5/1.5% O2/CO2 for the remaining storage period; and (3) 1.5/1.5% O2/CO2 until the final three weeks of the storage period where it changed to 2.0/2.0% O2/CO2. The differences between measured and predicted fruit weight of ‘Aroma’ apples varied by 0–4 g during the six harvesting dates in 2005, whereas the differences for ‘Elstar’ apples were 1–10 g. Measured and predicted Streif index for ‘Aroma’ and ‘Elstar’ apples varied between 0.01 and 0.07 g/w/w%*index and from 0.04 to 0.10 kg/w/w%*index, respectively. For ‘Aroma’ the Streif index was 0.16 kg/w/w%*index at the beginning of the storage period and 0.04 kg/w/w*index at the end; whereas the Streif indexes were 0.16 and 0.05 kg/w/w*index for ‘Elstar’. The highest and the lowest levels of the gas compositions resulted in the least and most mature apples, respectively. Apple colour was unaffected by air composition. Improved prediction of fruit weight and Streif index for ‘Aroma’ and ‘Elstar’ may be obtained using four linear equations and degree days without a reference temperature and improvement in prediction of apple fruit diameter may be obtained using degree days and two exponential equations. The quality characteristics of both cultivars were extremely high after storage in controlled atmosphere for 204 days and the analytical data including the low weight losses indicate that the storage time for ‘Aroma’ and ‘Elstar’ may be extended by at least two and three more months, respectively. The highest level of the gas compositions resulted in the least mature apples and may therefore be recommended for storage of ‘Aroma’ and ‘Elstar’.

LOCAL REACTION ZONE STRUCTURE OF NON-PREMIXED FLAMES OF PROPANE WITH HIGHLY PREHEATED LOW-OXYGEN AIR

To investigate the instantaneous structure of the local reaction zone of the HiCOT (High Temperature Air Combustion Technology) flames, the characteristics of ion current obtained from the non-premixed flames of propane with highly preheated low-oxygen air have been closely examined. Nonluminous (bluish-green) region is seen in the upstream part and luminous (bright yellow) region is seen in the downstream part of the non-premixed flames of propane with highly preheated low-oxygen air, while only the luminous region is seen in the non-premixed flames of propane with highly preheated regular air. The ion current fluctuations, obtained from the nonluminous region of the HiCOT flames, look quite similar with those obtained from turbulent premixed flames in the reaction sheet regime, implying that the unburnt mixture, burnt gas and local reaction zone exist separately. It has been clearly shown from the ion current that homogenous combustion does not occur but the local reaction zone exists separately from burnt and unburnt gases. The thickness of the local reaction zone in the nonluminous region of HiCOT flames is not broadened but is similar to that of the laminar premixed flames. Thickness of the local reaction zone in the non-premixed flames of propane with highly preheated regular air is estimated approximately twice as much as that in the nonluminous regions of the HiCOT flames.

Local Reaction Zone Thickness of Non-Premixed Flames of Propane with Highly Preheated Low-Oxygen Concentration Air

To investigate the instantaneous structure of the local reaction zone of the HiCOT (High Temperature Air Combustion Technology) flames, the characteristics of ion current obtained from the non-premixed flames of propane with highly preheated low-oxygen air have been closely examined. Luminous region is seen in the non-premixed flames of propane with highly preheated regular air and in the downstream part of the non-premixed flames of propane with highly preheated low-oxygen air. On the other hand, non-luminous region is seen only in the upstream part of the non-premixed flames of propane with highly preheated low-oxygen air. The ion current fluctuations, obtained from the non-luminous region of the HiCOT flames, look quite similar with those obtained from turbulent premixed flames in the reaction sheet regime. It has been clearly shown from the ion current that homogeneous combustion does not occur but the local reaction zone exists separately from burnt and unburnt gases. The thickness of the local reaction zone in the non-luminous region of HiCOT flames is not broadened but is similar to that of the laminar premixed flames. Thickness of the local reaction zone in the non-premixed flames of propane with highly preheated regular air is estimated approximately twice as much as that in the non-luminous region of the HiCOT flames.

NO x emission from high-temperature air/methane counterflow diffusion flame

The objectives of the present study are to measure NO x emission of counterflow diffusion flame, to compare the findings with numerical results, and finally to demonstrate efficacious effect of high-temperature air with low concentration of oxygen on NO x emission. Recently, high-temperature air with low concentration of oxygen is used for various industrial furnaces, resulting high efficiency and low emission of pollutants. Since high-temperature air increases NO x emission and air with low concentration of oxygen decreases it, these effects are competitive. Measurement and computation were conducted to clarify these two effects by use of counterflow diffusion flame. Since it is difficult to employ very high temperature over 1100 K in a laboratory-scale apparatus, a quantitative agreement between experimental and numerical results was confirmed first, and then a numerical approach was used to obtain a larger effect of low oxygen to reduce NO x emission. In the experiments, the methane concentration is changed from 10 to 30 vol% diluted by nitrogen, oxygen from 10 to 21 vol%, and air temperature from room temperature to 1100 K. The total amount of NO x sufficiently agreed between experimental and numerical results, although NO and NO 2 could not be separated. By the numerical method, it was found that NO x emission from the counterflow diffusion flame of high-temperature low-oxygen air of 1500 K and 5% oxygen is comparable with that of room-temperature air of 21% oxygen.

An experimental study on high temperature and low oxygen air combustion

High temperature preheated and diluted air combustion has been confirmed as the technology, mainly applied to industrial furnaces and kilns, to realize higher thermal efficiency and lower emissions. The purpose of this study was to investigate fundamental aspects of the above-mentioned combustion experimentally and to compare with those in ordinary hydrocarbon combustion with room temperature air. The test items were exhaust gas components of CO, NOx, flame shape and radical components of CH, OH and C2, which were measured with gas analyser, camera and ICCD(Intensified Charged - Coupled Device) camera. Many phenomena as results appeared in combustion with the oxidizer, low oxygen concentration and extremely high temperature air, such as expansion of the flammable limits, increased flame propagation speed, it looked so strange as compared with those in existing combustion technology. We confirmed that such extraordinary phenomena were believable through the hot-test experiment.

An experimental study on high temperature and low oxygen air combustion

High temperature preheated and diluted air combustion has been confirmed as the technology, mainly applied to industrial furnaces and kilns, for realizing higher thermal efficiency and lower emissions. The purpose of this study was to investigate fundamental aspects of the above-mentioned combustion experimentally and to compare with those in ordinary hydrocarbon combustion with room temperature air. The test items were exhaust gas components of CO, NOx, flame shape and radical components of CH, OH and C2, which we measured with gas analyser, camera and ICCD (Intensified Charged-Coupled Device) camera. Many phenomena, as a result, which appeared in the combustion with the oxidizer, low oxygen concentration and extremely high temperature air, such as expansion of the flammable limits, increased flame propagation speed, looked very strange in comparison with those in existing combustion technology. We confirmed that such extraordinary phenomena were believable through a hot-test experiment.

CLINICAL PATHOPHYSIOLOGICAL STUDIES ON AGE DIFFERENCE OF RESPIRATORY REGULATION IN LOW OXYGEN INHALATION

A. Age Difference in Arterial Blood Oxygen Saturation During a Period of Low Oxygen Air Respiration Attention has been called upon the fact that the degree of arterial blood oxygen saturation which serves as a criteria in the estimation of low oxygen air respiration may vary depending upon a number of conditions regardless of the same low oxygen air inspired. Considering this fact, the author has attempted to investigate this by statistically studying the data of arterial blood oxygen saturation during low oxygen air breathing. Method ; Estimation of arterial blood oxygen saturation (SaO2) during a period of 10% oxygen inhalation in various age groups composed of 46 healthy individuals were tabulated. SaO2 values were also, studied on another group of 20 healthy young adults during 10 ± 0.5% oxygen inhalation by venous catheterization. Results : (1) Without Venous Catheterization In the study of age relationship with the SaO2 values of 46 cases during 10 ± 0.5% low oxygen air inhalation without resorting to venous catheterization, a significant negative correlation, r=-0.66 (p <0.01), was obtained. The values of arterial oxygen saturation of respective age group were as follows : Young adult group (ages 20-39, 16 cases, average age 27.4) 74.0-5.4 per cent. Middle age group (ages 40-59, 11 cases, average age 50.4) 65.4 ± 7.1 per cent. Old age group (ages 60-78, 19 cases, average age 68.8) 63.6 ± 5.1 per cent showing a low value. (2) With Venous Catheterization The healthy young adults (ages 21-38, 20 cases, average 30.8) were studied under the same low oxygen inhalation with venous catheterization. The SaO2 value was found to be 62.6 ± 7.9 per cent, a definitely lower value when compared with that (74.0 ± 5.4 per cent ) of the none catheterized young adults. From the foregoing results, it was found that in the old age persons without venous catheterization, the SaO2 reduction was more marked than that of the young adults without catheterization and just comparable to that of the latter with catheterization.

災害と疲労 (II) : 作業時flicker値の低下限界とこれからみた災害発生の可能性

Though it is comprehensible from our routine experience that fatigue should be an important cause of accident, the proving of it is next to impossible. As far as every hour's accident rate is concerned, accidents caused by fatigue seem to be very few in common factories. But, in accident curve of heavy workers the peaks tend to thrive toward the end of work, this means the increase of accidents of fatigue origin. This tendency is also found in bus driving, an increase in accident rate several hours after the start (figs. 1, 2). We saw that drivers' fatigue remarkably varied with the condition of roads. FF (critical flicker frequency) curve, which is based on flicker test performed every 15-20 minutes during run, seem to have four patterns in it (fig. 3). Pattern B is obtained from a bad road, C from a good one, A worse than B and D better than C. In A and B FF heavily drops sometime during drive, but not below a certain level as long as the driving is kept on, which is presumably due to the fact that the situation requires a driver to be excited interoceptively or exteroceptively above the level. The level is, therefore, thought to be the lowest bottom of FF he is allowed to take, in other words, the physiological criterion for safety drive. We next examined FF change in accordance with consciousness disorder during the experimental inhalation of low oxygen air and ascertained that when the initial disorder (drowsy state) appeared in brain wave (fig. 4, 5) the ability in mental work such as a simple adding showed a quick drop (fig. 6). FF at this period when normal mental activity begins to get impaired I call a critical level (CL). CL is variable individually 85-92 per cent of the resting level, but almost constant with the same person. And it appears nearly equal to the safety limit during drive as seen from the diminution rate of the two. When FF during run surpasses the critical level normal mental activity must be in disorder, thus increasing the possibilty of accidents. Hence the relation between fatigue and accidents can be discussed with regard to the FF curve and critical level mentioned above.

誘発性低酸素血症に於ける心筋糖質代謝に関する臨床的研究

Carbohydrate metabolism under hypoxemic conditions was first studied by Araki' in 1895, and since that time numerous reports have been published on this subject. With the introduction of the coronary catheterization method by Bing in 1949, it has become possible study the coronary flow and cardiac muscle metabolism directly. The influence of oxygen dificiency on carbohydrate metabolism in the human cardiac muscle, the relation to other factors and differences in cardiac conditions of various types however, have not yet been examined. In the present study, 52 cases of normal subjects and subjects with some disorder were placed in a state of hypoxemia induced by low oxygen loading (10% O2 for 20 minutes), and in 25 cases of these, coronary catheterization was performed before breathing of low oxygen air. In the 52 cases, samples of the arterial blood and in the latter 25 cases samples of the arterial and the coronary venous blood were taken prior to, 5 minutes and 15 minutes after loading. The author measured the glucose, lactate and pyruvate levels, and the findings were considered in relation to the results obtained by the co-workers on the gas content of the blood and the amount of coronary flow.The results are presented here.(1) Changes in myocardial carbohydrate metabolism in the stage of low oxygen breathing.(i) Initial stage (after 5 minutes, arterial O2 saturation 60-80%).In arterial levels, glucose is slightly increased, lactate is almost unchanged, pyruvate is slightly decreased and the L/P ratio shows a small increase. The percentage of each change is within ±3%. Examination of the myocardial extraction shows that the relation between extraction of glucose and the arterial concentration is more pronounced following loading with a trend for higher extraction with higher glucose concentration in the artery. This corresponds to the findings under anaerobic condition described Schumann. Lactate and pyruvate extractions show a slight decrease, but the relation between the lactate- and pyruvate extraction coefficient is clearer than before loading. Thus at this stage the influence of low oxygen loading still seems to be small, and it may be said that this stage is that of compensatory response to hypoxemia.(ii) Stage of constant hypoxemia (after 15 minutes, arterial O2 saturation 45-70%).There is an increase in glucose, lactate, pyruvate and L/P ratio. The lactate especially shows a rise of 25%. The others, glucose pyruvate and L/P ratio show a rise of about 9%. Myocardial extraction however, is reduced despite the rise in glucose, lactate and pyruvate levels, and the relation between lactate- and pyruvate extraction coefficient no longer becomes apparent. In other words, distinct disturbances in myocardial carbohydrate metabolism are produced at this stage of induced hypoxemia.(2) Relation between carbohydrate metabolism and gas metabolism in hypoxemic myocardium.(i) The relationship between myocardial carbohydrate extraction and arterial oxygen content.With advance in the state of hypoxemia, extraction of blood carbohydrate metabolites decreases and there is a freeing of metabolites from the cardiac muscle. After 15 minutes, when a constant state is reached, there is a suppression of glucose, lactate and pyruvate extraction in the order named together with reduction in arterial oxygen content. The borderline is an arterial oxygen content of 12-10 Vol%.(ii) The relationship between myocardial carbohydrate metabolism and coronary flow.Calculation of the mean carbohydrate usage, by multiplying the extractions with the coronary flow, was performed prior to and 15 minutes after loading. Glucose usage is reduced in general in the normal, pulmonary and circulatory cases in which coronary flow is increased.