Field comparison between two nitrous oxide (N2O) passive monitors and conventional sampling methods

Field tests conducted over the range of 4-330 ppm nitrous oxide in hospital operating rooms as well as dental and veterinary clinics showed a prototype of the Landauer NITROX passive monitor compared more favorably with a Miran 1-A IR gas analyzer than either the Solid State Sensor or bag samples. All methods were tested simultaneously in a chamber designed to produce uniform real-time monitoring.     

笑气吸入法镇痛分娩的临床观察

目的观察笑气吸入法镇痛分娩的临床效果.方法随机选取253例在我院待产孕妇,遵循自愿原则分为镇痛组(123例)与非镇痛组(130例).观察两组产程、产后出血、分娩方式、羊水性状、新生儿窒息等进行资料统计分析.结果两组第一产程、总产程比较,镇痛组明显短于对照组,P<0.01,有显著性差异,第二、三产程,产后出血、剖宫产羊水性状两组比较无显著性差异,P>0.05,新生儿窒息对照组多于镇痛组,但两组比较P>0.05,无显著性差异.结论笑气镇痛分娩是安全有效的,值得推广应用.     

N2O production pathways in the subtropical acid forest soils in China

To date, N₂O production pathways are poorly understood in the humid subtropical and tropical forest soils. A ¹⁵N-tracing experiment was carried out under controlled laboratory conditions to investigate the processes responsible for N₂O production in four subtropical acid forest soils (pH<4.5) in China. The results showed that denitrification was the main source of N₂O emission in the subtropical acid forest soils, being responsible for 56.1%, 53.5%, 54.4%, and 55.2% of N₂O production, in the GC, GS, GB, and TC soils, respectively, under aerobic conditions (40%–52%WFPS). The heterotrophic nitrification (recalcitrant organic N oxidation) accounted for 27.3%–41.8% of N₂O production, while the contribution of autotrophic nitrification was little in the studied subtropical acid forest soils. The ratios of N₂O–N emission from total nitrification (heterotrophic+autotrophic nitrification) were higher than those in most previous references. The soil with the lowest pH and highest organic-C content (GB) had the highest ratio (1.63%), suggesting that soil pH-organic matter interactions may exist and affect N₂O product ratios from nitrification. The ratio of N₂O–N emission from heterotrophic nitrification varied from 0.02% to 25.4% due to soil pH and organic matter. Results are valuable in the accurate modeling of N2O production in the subtropical acid forest soils and global budget.     

Effect of He-O2, O2, and N2O-O2 breathing on injected bubbles in spinal white matter.

Injected air bubbles in spinal white matter in the rat were studied at 1 bar after decompression from an exposure to air at 3.1 bar (absolute) for 4 h. During air breathing all injected bubbles grew for the first 2 h of the observation period. Thereafter three of nine bubbles began to shrink and one of them disappeared. During breathing of heliox (80:20) bubbles consistently shrank and disappeared from view. If the breathing gas was changed from heliox to N2O-O2 (80:20), while bubbles still had an appreciable size, they started growing again. If the change to N2O-O2 was done after a bubble disappeared from view, it did not reappear. During breathing of 100% oxygen, all bubbles initially grew. Subsequently they all shrank and disappeared at about the same time after gas shift, as during heliox breathing. The effect of heliox treatment on CNS decompression sickness after air dives is discussed.     

维生素E对N2O4致肺水肿的预防作用及机理探讨

四氧化二氮(N2O4)是工业上常见的化学品,主要以气态二氧化氮(NO2)形式,通过呼吸道吸入引起肺损伤.因此,深入开展防治N2O4损伤的研究是医学领域的重要课题.本文观察了维生素E对N2O4致肺水肿的预防作用及机理,旨在为中毒性肺损伤的防治提供更广泛的依据.     

O2 pressures between 0.12 and 2.5 atm abs, circulatory function, and N2 elimination

To study the effects of inhaled oxygen pressures on N2 elimination, 72, 2-h washouts were performed in 6 subjects at oxygen pressures of 0.12, 0.2, 1.0, 2.0, and 2.5 atm abs using a closed circuit system that supplied an O2-argon mixture and collected the N2 off-gassed. Hypoxia induced a significant (9.4%, P less than 0.05) increase in nitrogen eliminated as compared to normoxia. Pure oxygen breathing induced a small, insignificant (3.5%) decrease in nitrogen yields, but further increases in oxygen pressure induced significant decreases in nitrogen yields (-8.9% and -16.9% for 2.0 and 2.5 atm abs, respectively). Heart rate, cardiac output, skin perfusion and leg blood flow decreased, whereas mean arterial pressure increased with increasing oxygen pressure. We conclude, therefore, that perfusion-dependent N2 elimination decreases secondary to vasoconstriction induced by increasing oxygen pressures. Changes in inhaled oxygen pressures during different phases of compression-decompression may induce alterations in the rate of inert gas uptake and elimination. Although not currently quantifiable, such alterations would imply added uncertainties in the computation of decompression schedules. Oxygen breathing during decompression should be performed at the lowest possible ambient pressure compatible with freedom from pathogenic bubble formation.     

Narcotic potency of N2, A, and N2O evaluated by the physical performance of mouse colonies at simulated depths.

The physical performance of colonies of deer mice was studied in various inert gas environments at pressures up to 31 ATA. The mice were housed in habitats wherein their diurnal running activity and social interactions could be monitored. By transferring the portable habitats and mouse colonies to a high pressure chamber, the effects of elevated inert gas pressures were studied in socially and ecologically intact surroundings. Analysis of wheel-running performance showed that either 1.1 atm nitrous oxide, 7.2 atm argon, or 20.5 atm nitrogen reduced running activity to 50% of its control value. Behavioral observations revealed a deterioration of physical performance and social interaction with increasing inert gas pressures. A comparison was made between ED50 (the dose that will depress a particular response by 50%) values obtained by studying wheel-running activity and those published for single-reflex responses.     

Formaldehyde (CH2O) concentrations in the blood of humans and Fischer-344 rats exposed to CH2O under controlled conditions

The effect of exposure to formaldehyde (CH2O) on the CH2O concentration of the blood was determined. Eight male F-344 rats were exposed to 14.4 +/- 2.4 ppm of CH2O for 2 hours and the blood was collected immediately after exposure. Formaldehyde concentrations in the blood were determined by gas chromatography/mass spectrometry. The blood of eight rats unexposed to CH2O was collected and analyzed in the same manner. Measured CH2O concentrations (micrograms/g of blood) were: controls, 2.24 +/- 0.07; exposed, 2.25 +/- 0.07 (mean +/- S.E.). Formaldehyde concentrations in human blood were determined by analyzing samples of venous blood collected before and after exposure of six human volunteers (4 M, 2 F) to 1.9 +/- 0.1 ppm of CH2O for 40 min. Average CH2O concentrations (micrograms/g of blood) were: before exposure, 2.61 +/- 0.14; after exposure, 2.77 +/- 0.28. In neither experiment was there a statistically significant effect of exposure on the average CH2O concentration of the blood. However, human subjects differed significantly with respect to their blood CH2O concentrations, and significant differences (either an increase or a decrease) were found between the CH2O concentrations of the blood taken before and after exposure from some of the subjects, suggesting that blood CH2O concentrations may vary with time.     

Study of neutralization of 218 Po ions by small ion recombination in O2, Ar, and N2.

Three mechanisms of neutralization of Po(+)--electron transfer, electron scavenging, and small ion recombination--have previously been suggested. Considerable work has been conducted on the first two mechanisms. However, little information about small ion recombination is available. In the present study, this mechanism was studied by examining the neutralization rates of different Rn concentrations in N2, Ar, and O2 with the aid of a continuous Rn progeny monitoring system. The results showed that the neutralization rates in the three gases are of the order 1-4 s-1 at high Rn concentrations (higher than 40,000 Bq m-3). A linear relationship between the neutralization rate and the square root of Rn concentration (from 40,000 Bq m-3 to 810,000 Bq m-3) was obtained. Neutralization rates were higher in the gas with lower ionization potential. Further, the existence of a neutralization rate plateau at high Rn concentrations was strongly suggested.     

Limited exposure of rats to H2SO4 with and without O3

The purpose of this study was to determine the effects of sulfuric acid (H2SO4) alone and with ozone (O3) on rats. To accomplish this, rats were exposed for 8 hours daily to an atmosphere containing either nebulized H2SO4, H2SO4 plus 0.9 ppm O3, or 0.9 ppm O3. The atmosphere in the exposure chambers was maintained at a fairly constant temperature and humidity. Nebulized H2SO4 was delivered uniformly to provide a particle size of about 0.3 micron mass median diameter (MMD) and a mass concentration of 2 mg/m3. In preliminary experiments, animals exposed to 2 mg/m3 of H2SO4 daily for 82 days showed very slight morphologic injury to the respiratory tract. In contrast, biological effects were readily demonstrable in rats exposed to H2SO4 plus O3 or to O3 alone, possibly with some enhancement of effect in animals exposed to the mixture. The effects observed were characteristic of the response to O3 alone.     

氧化亚氮联合利多卡因行无痛人工流产术280例临床分析

目的: 探讨吸入 50%氧化亚氮 (N2O) 与 50%氧气 (O2 ) 的混合气体联合宫颈注射 2%利多卡因进行无痛人工流产术 (人流术) 的有效性和安全性。方法: 将人流术 580例分为A、B两组。其中A组 280例吸入 50%氧化亚氮 (N2O)与 50%氧气的混合气体联合宫颈注射 2%利多卡因进行无痛人流术, 称为联合组; B组 300例, 不用任何药物, 为对照组, 分析比较两组手术中镇痛效果, 宫口松弛情况, 手术出血量, 人流综合反应。结果: 联合组镇痛完全, 有效率达 97 5%。宫口完全松弛率 97 9%。两组比较有显著性差异 (P<0 05)。结论: 吸入氧化亚氮联合宫颈注射利多卡因进行无痛人流术, 镇痛效果确定, 人流时受术者意识处于朦胧状态, 安静, 无痛苦, 不良反应少, 苏醒快等。     

三氧化二砷亚急性染毒对雄性小鼠生殖与免疫毒性的研究

目的探讨As2O3亚急性染毒对雄性小鼠生殖与免疫毒性作用。方法24只清洁级KM雄性小鼠,分为对照组、低、中及高剂量染砷组。分别给予去离子水,As2.0、4.0、8.0mg/kg体重灌胃染毒7天。实验结束后剖杀动物取睾丸、附睾称重、计算器官指数并测定附睾精子数,摘取免疫器官胸腺、脾脏称重、计算免疫器官指数。结果(1)高剂量组睾丸及附睾重量低于正常对照组(P<0.05),但各组睾丸指数与对照组没有差异;各染砷组精子数均低于对照组(P>0.05),且中、高剂量组精子畸形率上升显著(P<0.05);(2)中、高剂量组免疫器官重量及指数降低,且高剂量组脾脏重量及指数显著低于对照组(P<0.05)。结论As2O3可致小鼠某些生殖和免疫毒性指标改变。