Effect of step duration during incremental exercise on breathing pattern and mouth occlusion pressure

We compared the effects of two step durations on breathing pattern, mouth occlusion pressure and "effective" impedance of the respiratory system during incremental exercise. Nine normal subjects (mean age: 27.8+/-1.21 years) performed two incremental exercise tests in randomized order: one test with step increments every 1 min 30s and the other, every 4 min. After a warm-up at 25 W for the 1 min 30 s test, the power was increased by 50 W from 50 W to exhaustion. During the last minute at each power, we measured ventilation (VE), tidal volume (VT), breathing frequency (fR), inspiratory and expiratory time (TI and TE), total time of the respiratory cycle (TTOT), TI/TTOT, mean inspiratory flow (VT/TI), mouth occlusion pressure (P0.1), "effective" impedance of the respiratory system (P0.1/(VT/ TI)) and venous blood lactate concentration ([La]). Our result showed that at maximal exercise the power was significantly higher (p < 0.01) and [La] lower (p < 0.01) in the 1 min 30 s test. At 100, 150 and 200 W, the 4 min test showed significantly higher oxygen uptake (VO2), carbon dioxide output (VCO2), VE, P0.1, fR, VT/TI and HR (p <0.001) and significantly lower TI, TE and TTOT (p<0.01). [La] was significantly higher at 150 W (p<0.05) and 200 W (p<0.001). At the same VCO2, P0.1 was not significantly different between the two tests, whereas VE showed a tendency to be higher (p = 0.08) and P0.1/(VT/TI) was significantly lower during the 4 min test. In conclusion, this study allowed us to quantify the difference in inspiratory neuromuscular output and ventilatory response between 1 min 30s and 4 min tests and showed that different step durations alter the relationship between inspiratory neuromuscular output and mean inspiratory flow.     

The effect of low flow oxygen on sleep-disordered breathing and oxygen desaturation. A study of patients with chronic obstructive lung disease

Oxygen desaturation occurs during sleep in many patients with chronic obstructive lung disease (COLD) and is often caused by sleep-disordered breathing (SDB). Nocturnal oxygen therapy should improve nighttime hypoxemia, but might also worsen SDB. Using standard polysomnographic techniques, we evaluated the frequency and duration of oxygen desaturation and SDB during sleep in 11 patients with stable COLD. During half of the night the patients breathed air through a nasal cannula and during the other half of the night they breathed oxygen at 2 liters per minute. Five patients had arterial lines inserted for determination of arterial blood gas levels during periods of SDB or desaturation. The ten men and one woman slept 70 minutes (52 percent of time in bed) while on air and 111 minutes (80 percent of time in bed) while on oxygen (p < 0.001). Oxygen therapy reduced the number of episodes of desaturation per hour and the time spent in desaturation. However, there was no difference between air and oxygen in episodes of SDB per hour, the duration of episodes of SDB, baseline sleeping PaCO2 or PaCO2 during episodes of desaturation or SDB. Therefore, in most patients with stable COLD, administration of oxygen at 2 liters per minute improves oxygenation, prolongs sleep, but does not adversely affect SDB.     

Nasal response in subjects undergoing challenges by inhaling occupational agents causing asthma through the nose and mouth

BACKGROUND: Subjects with occupational asthma (OA) often report nasal symptoms, but nasal reactions to inhalation challenges with occupational agents have not been well characterized. METHODS: Fifteen subjects with OA (eight due to high-molecular-weight agents--flour and guar gum--and seven due to isocyanates) underwent inhalational challenges using closed-circuit devices (dry particles for high-molecular-weight agents and gas generator for isocyanates) on two occasions, 2-4 weeks apart in a random fashion. On one occasion, they inhaled through the nose and, on another, through the mouth. The FEV1 was monitored for up to 8 h afterward, and symptoms were documented with a standardized questionnaire on nasal symptomatology, assessment of nasal resistance by rhinomanometry, and nasal lavage for the examination of cells and mediators. RESULTS: Inhaling through the mouth and through the nose: 1) yielded similar asthmatic responses (25+/-8% and 22+/-10% maximum changes in FEV1) 2) more than doubled the peak nasal symptoms and nasal resistance when the maximum daily response was compared with prechallenge results. This increase occurred on the days of inhalational challenges through the mouth and through the nose. There were some significant responses assessed by nasal lavage in terms of cells and mediators, again with no differences between the days of challenges through the mouth and through the nose. CONCLUSIONS: Inhaling occupational agents of high or low molecular weight, including isocyanates, whether through the mouth or nose: 1) results in a similar asthmatic response 2) causes a significant nasal response in terms of symptoms and an increase in nasal resistance 3) causes some significant changes in inflammatory cells and mediators.     

锰银矿同步浸出锰、银新工艺试验研究

介绍了在H2O2体系中处理锰银矿新方法。针对矿石中锰和银的赋存形式,采用在硫酸溶液中加入H2O2可以实现二氧化锰还原和银氧化同时进行。为了进一步提高银的浸出率,在溶液中加入高锰酸钾,以浸出未被二氧化锰包裹的银。研究结果表明,在最佳浸出条件下,锰浸出率可达到96．71％,银浸出率达85．1％。     

Effect of exposure to 15% oxygen on breathing patterns and oxygen saturation in infants: interventional study

OBJECTIVE: To assess the response of healthy infants to airway hypoxia (15% oxygen in nitrogen). DESIGN: Interventional study. SETTINGS: Infants' homes and paediatric ward. SUBJECTS: 34 healthy infants (20 boys) born at term; mean age at study 3.1 months. 13 of the infants had siblings whose deaths had been ascribed to the sudden infant death syndrome. INTERVENTION: Respiratory variables were measured in room air (pre-challenge), while infants were exposed to 15% oxygen (challenge), and after infants were returned to room air (post-challenge). MAIN OUTCOME MEASURES: Baseline oxygen saturation as measured by pulse oximetry, frequency of isolated and periodic apnoea, and frequency of desaturation (oxygen saturation < or = 80% for > or = 4 s). Exposure to 15% oxygen was terminated if oxygen saturation fell to < or = 80% for > or = 1 min. RESULTS: Mean duration of exposure to 15% oxygen was 6.3 (SD 2.9) hours. Baseline oxygen saturation fell from a median of 97.6% (range 94.0% to 100%) in room air to 92.8% (84.7% to 100%) in 15% oxygen. There was no correlation between baseline oxygen saturation in room air and the extent of the fall in baseline oxygen saturation on exposure to 15% oxygen. During exposure to 15% oxygen there was a reduction in the proportion of time spent in regular breathing pattern and a 3.5-fold increase in the proportion of time spent in periodic apnoea (P < 0.001). There was an increase in the frequency of desaturation from 0 episodes per hour (range 0 to 0.2) to 0.4 episodes per hour (0 to 35) (P < 0.001). In 4 infants exposure to hypoxic conditions was ended early because of prolonged and severe falls in oxygen saturation. CONCLUSIONS: A proportion of infants had episodes of prolonged (< or = 80% for > or = 1 min) or recurrent shorter (< or = 80% for > or = 4 s) desaturation, or both, when exposed to airway hypoxia. The quality and quantity of this response was unpredictable. These findings may explain why some infants with airway hypoxia caused by respiratory infection develop more severe hypoxaemia than others. Exposure to airway hypoxia similar to that experienced during air travel or on holiday at high altitude may be harmful to some infants.     

固态金属及合金材料中氧、氮、氢联测技术进展

对金属和合金材料中氧、氮、氢3种气体元素的联测技术进展进行了综述,侧重汇总了各种联测方法的分析流程及技术指标,同时介绍了相关的气体分析仪器的情况,最后指出以质谱仪为检测器的联测技术有望成为氧、氮、氢联测技术的发展方向。     

A new microprocedure for continuous and non-consuming determination of cellular oxygen uptake based on fluorescence quenching

The oxygen uptake in a cell suspension can be measured by various methods using manometric, paramagnetic or photometric techniques, oximetry, mass spectrometry or radiospectrometry. Easy-to-apply Clark-type electrochemical (polarographic) sensors are by far the most commonly used devices in medical applications. One of their drawbacks is the fact that they consume oxygen and may cause systematic errors when measuring oxygen uptake. Since the beginning of this century, concentration dependent quenching luminescence by oxygen has been used in a number of experimental settings. Using this analytical approach it is possible to detect oxygen without consuming it. We report about a new method of assessing cellular oxygen uptake using the luminescence quenching by oxygen. In an 850 microliters oxygen-tight microchamber, a fluorescent dye (tetraphenylporphyrin) adsorbed on a monolayer of gas chromatographic beads is separated from a cell suspension by a silicone membrane. An active electrochemical electrode integrated within the chamber is used to calibrate the fluorescence signal. Fluorescence is generated by green light (wavelength lambda = 546 nm), the intensity of the emitted red fluorescent light (lambda > 630 nm) is measured with a photomultiplier tube. As the first application of this new method, the oxygen uptake of human lymphocytes was determined. The cells were prepared using a routine separating technique-gradient centrifugation in Ficoll. For methodological reasons, all experiments were carried out at a temperature of 22 degrees C. In 7 consecutive measurements, an oxygen uptake of 2.81 +/- 0.85 mmol O2/10(11) lymphocytes/h was found. In less concentrated suspensions this figure is higher--an effect known as the "crowding phenomenon"--which means that with increasing cell concentration the specific oxygen uptake rate decreases. Our values for cellular oxygen uptake are higher than those in the literature. Since most reported studies on lymphocytes were done at 37 degrees C, a larger difference between our values and those in the literature would be expected. This may in part be attributed to different cell concentrations, separation techniques, etc. Another explanation might be the fact that electrochemical oxygen sensors used by other authors consume oxygen. Cell suspensions investigated with polarographic sensors therefore need to be stirred. Slow stirring reduces the values of oxygen uptake, so that a high stirring frequency is needed to obtain correct results (so-called stirring effect of polarographic electrodes). High stirring frequencies, however, destroy cells, which might be another factor explaining the results reported above. Our new method based on fluorescence quenching consumes no oxygen, and is therefore independent of stirring.     

Qigong and L-1 straining maneuver oxygen system requirements with and without positive pressure breathing

Based on the characteristics of respiration and the intrathoracic pressure in Qigong (Q-G) maneuvering, it has been theorized that the Q-G maneuver may lessen the lack of coordination between aircraft oxygen apparatus and anti-G maneuvers and may be more compatible with positive pressure breathing (PPB). In an experiment intended to test this hypothesis, 5 male volunteers, trained in Q-G and L-1 maneuvers, performed the Q-G and the L-1 maneuvers without and with (PPB) at 4 and 6 kPa, respectively, with 14 respiratory parameters being measured. The results demonstrated that, when performing Q-G maneuver, the maximal expiratory flow rate averaged 1.175-1.645 L.s-1, the inspiratory peak flow, 1.003-1.297 L.s-1. Both these values were markedly lower than those of the L-1 maneuver, and matched well the performance of current aircraft oxygen apparatus. From the blood pressure and heart rate values, it is evident that PPB can further promote the blood pressure-raising effect of the Q-G maneuver, and alleviate pilots' fatigue.     

Experiences with a new bone drill for surgery of the ear and nose (author's transl)

Surgical drilling similar to that developed by Kaltenbach and Voigt for bone work on the ear, nose, maxilla, hand and vertebrae can be used at up to 80,000 rev/min without undesirable heat production. Drill-bits with the normal shaft length of 45 mm remain steady at 80,000 rev/min, but drill-bits of 70 mm length sometimes vibrate. The size of drill head and rate of revolution in this respect are related proportionately especially with cutting as opposed to diamond drill-heads. In ear surgery this method is only suitable on certain conditions. In nasal surgery it is useful for the transverse osteotomy with a 45 mm long circular saw.     

A new Combi test for simultaneous detection of antibodies to viral capsid, early and EBNA antigens of Epstein-Barr virus

In order to facilitate the differentiation between a recent (acute) and a past Epstein-Barr virus (EBV) infection, the Combi test was developed. This test is an anticomplement immunofluorescence test (ACIF) requiring only a single serum dilution to be tested on a single cellular spot. The cell line used expresses viral capsid antigen (VCA) and early antigen (EA) in about 5 to 10 percent of the cells as well as EBV nuclear antigens (EBNA) in more than 90 percent of cells. A satisfactory agreement between the Combi test and other tests for antibodies to EBV was obtained (IgG and IgM antibodies to VCA by IFA and EIA and antibodies to EBNA by ACIF including tests for heterophile and complement-fixing antibodies). When the standard serological tests gave negative results, the Combi test was also negative (absence of any fluorescence in the cells). Serologically confirmed recent (acute) infections lead to specific fluorescence in only 5 to 10 percent of the cells, while past infections result in fluorescence in 90 percent or more of the cells. For the diagnosis of a reactivated EBV infection or of EBV-associated malignancies, other tests should be employed. The test is based on the measurement of the activation and specific distribution of the C3 component of complement; the antibody class differentiation is therefore not necessary. The presence of rheumatoid factor (RF) and the IgG competition phenomenon do not influence the results of the Combi test. An introduction of the Combi test will enable a simplified, less expensive and more reliable serodiagnosis of EBV infections.     

Comparison of oxygen cost of breathing with pressure-support ventilation and biphasic intermittent positive airway pressure ventilation

OBJECTIVE: To assess the oxygen cost of breathing with either pressure-support ventilation (PSV) or biphasic intermittent positive airway pressure ventilation (BIPAP). DESIGN: Prospective, randomized, crossover study. SETTING: Medical intensive care unit of a university hospital. PATIENTS: Twenty clinically stable and spontaneously breathing patients after long-term mechanical ventilation. INTERVENTIONS: Patients were randomized to start on either PSV or BIPAP, and measurements were performed after an adaptation period of 30 mins. Immediately after, the ventilatory mode was changed and after another 30-min adaptation period, the same measurements were performed. MEASUREMENTS AND MAIN RESULTS: Indirect calorimetry was performed during each ventilatory mode for a period of 30 mins. Oxygen consumption, energy expenditure, CO2 production, and respiratory quotient did not differ significantly between the two ventilatory modes, regardless of the patients' randomization. There were no statistically significant differences with regard to respiratory rate, minute volume, and blood gas analysis. All patients tolerated both ventilatory modes without any signs of discomfort. CONCLUSIONS: Pressure support ventilation and BIPAP are both used for weaning patients gradually from the ventilator. BIPAP may be advantageous in patients not breathing sufficiently with PSV, since no patient effort is necessary with use of this ventilatory mode.     

Evaluation of a new semiautomatic electrode system for simultaneous measurement of ionized calcium and pH

The instrument (ICA 1 Radiometer, Copenhagen) measures the activity of calcium ion and hydrogen ion and displays the estimated concentration of free calcium ion (cCa2+) and pH at 37 degrees C in 110 microliter of whole blood or serum. The cCa2+ at pH 7.40 is calculated by means of a fixed relationship between cCa2+ and pH. The results are indicated on a display approximately 1 min after sample introduction. The measuring cycle plus automatic rinsing takes 3 min. The apparatus is equipped with a number of control functions. The sensitivity of the calcium electrode showed a fall from 100% to 92% over 20 weeks. The cell potential of the calcium cell showed a slow drift of--0.02 mV per day over a 20-week period while the pH cell which employs the same reference electrode showed no drift. Interference of Na+, K+, Li+, Mg2+ and H+ on the calcium measurement in whole blood is estimated to be at most +0.1%. The effect of erythrocytes on the static liquid junction potential is minimized by a special extrapolation procedure. The analytical standard deviation for cCa2+ in serum was 0.008 mmol/l within series, 0.017 mmol/l between days. The mean value for cCa2+ (at pH 7.4) in serum for 53 healthy adults was 1.249 mmol/l with a standard deviation of 0.036 mmol/l. cCa2+ in capillary blood at the actual pH from 20 healthy volunteers gave a mean value of 1.215 +/- 0.047 mmol/l (+/- 2SD) with pH 7.428 +/- 0.031 (+/- 2 SD). The slopes delta lgcCa2+/delta pH measured after equilibration at two different PCO2 values in venous blood (n = 20) and in serum (n = 104) gave a mean value of -0.221 +/- 0.040 (+/- 2 SD). The semi-automatic combined Ca2+ - pH electrode system makes the measurement of ionized calcium for clinical use a reliable and accurate analysis.     

A new type of oxygen analyzer utilizing a potentiostatic coulometric titration technique

A new type of oxygen analyzer was constructed utilizing the electrochemical oxygen pump: Pt, air/ZrO₂ (+ CaO)/Ar + H₂ + H₂0 gas mixture, Pt. Copper, indium, or tin samples were melted in a circulating Ar + H₂ gas mixture; the oxygen content was then determined within 3 minutes from the change in the electrical current passing through the oxygen pump. The analytical values were highly consistent and reliable despite the fairly low oxygen concentrations in the samples. Neither standard samples nor the establishment of blank conditions was necessary. This type of oxygen analyzer appears to be useful for determining oxygen concentrations less than 1 wt ppm.     

The urethral closure pressure profile. A new technique using gas and simultaneous EMG-recording from the urethra

A new technique for recording of the urethral closure pressure profile using gas-inflation and simultaneous EMG-recording from the urethra is described. With the present technique, the parameters of the urethral closure pressure profile in healthy volunteers were in accordance with previous reports using water-infusion. The effect of alpha-adrenergic blockade on the pressure profile was studied in a series of patients. Half of the patients showed a marked reduction of the intraurethral pressure in the presphincteric part of the profile after alpha-adrenergic blockade. This indicated that sympathetic innervated smooth musculature gives a significant contribution to the total intraurethral pressure.     

Evaluation of respiratory muscle strength in patients with interstitial lung changes based on simultaneous measurement of esophageal and mouth pressure

A well know good relation between nasal and oesophageal inspiratory pressures exists in healthy and in COPD patients "sniff manoeuvres. Similar results are obtained using "gasp" maneuvers. The aim of the study was to appreciate the usefulness of "gasp" for evaluation of inspiratory muscles strength in ILD patients. 18 ILD patients were examined: group A consisted of 9 pts (8M+IF) aged 35 +/- 8.6 yrs, with static compliance > 70% pred. (mean 98.6 +/- 16.3), group B consisted of 9 pts (6M + 3F) (aged 52 +/- 13.0) with static compliance < 70% pred. (mean 37.2 +/- 12.0), Pmo and Poe (Milic-Emili method) were measured simultaneously during breathing with Pflex device (1.7 mm diameter). Results were stored in a computer for further analysis. In all patients spirometry, plethysmography and maximal inspiratory (MIP) and maximal expiratory (MEP) pressure measurements were performed. Poe and Pmo in group A were nearly the same (8.16 +/- 1.82 vs. 8.35 +/- 2.74 kPa), but in the group B Pmo was lower than Poe (4.81 +/- 1.59 vs. 6.19 +/- 2.03 kPa; p < 0.0005). We conclude that "gasp" - Pmo is a useful method for inspiratory muscle strength measurement only in ILD patients with normal static compliance but in ILD patients with decreased compliance "gasp" - Poe measurement in necessary.     

A new technique for measuring the effects of oxygen activity on surface energies: Application to nickel

A new technique for oxygen fugacity control was used in conjunction with the microcreep method for determination of surface energy. Oxygen fugacity was controlled by electro-statically controlled pumping through a solid zirconia electrolyte. The method was applied to the measurement of the surface energy of nickel at 1300°C as a function of oxygen fugacity in the range 10_-6 to 10_-13 N/m². The determined surface energy value, 2.12 J/m², at the lowest oxygen fugacity is in good agreement with other measurements, while values at other pressures indicate a variation with oxygen adsorption similar to that observed for copper. Twin and grain boundary energies were also determined and found to agree well with earlier work once a texture effect for metal foils was included in the analysis.