Technical pitfalls in middle ear gas studies: Errors introduced by the gas permeability of tubing and additional dead space

Conclusions We demonstrated errors introduced by the gas permeability of the tubing and additional dead space. Materials with practically no permeability, such as glass, must be used to overcome the loss or gain of gas through the walls of tubes used for studying ME gas variations. Experiments conducted at a constant volume (variable pressure) require the smallest possible tubing volume in order to obtain good sensitivity and improve the accuracy of the results.

Objectives Experimental studies that investigate middle ear (ME) gas exchanges, using either pressure measurements or volume changes, are conducted using various tubing connections between the ME and a measuring device. The aims of this study were to highlight experimental problems due to the errors introduced by (i) the gas permeability of the tubing used and (ii) additional dead space in experiments conducted at constant volume.

Material and methods The problem of the gas permeability of the tubing was addressed by comparing three types of tube (silicone, polyethylene, PVC) with a glass tube. Horizontally placed tubes were connected to a syringe filled with pure CO₂ via a gas-tight valve. The end of each tube tested was plunged into colored water (5% Coomassie Brilliant Blue R-250). The tube was washed out with CO₂ until gas bubbles were seen leaving it. The valve was then closed and the movement of water in the tube was observed. The same experiments were repeated for pure O₂. The problem of the error introduced by the additional dead space volume was addressed at a theoretical level using the well-known gas laws. Two conditions were studied: condition A, in which the experiment was conducted at constant pressure and the volume was measured; and condition B, in which the experiment was conducted at constant volume and the pressure was measured. The main outcome measure of each condition was the calculated variation in the final number of moles of gas involved.

Results No water movement was observed in glass tubes. In contrast, plastic tubes exhibited significant gas permeability effects for both CO₂ and O₂. The colored solution advanced at a faster rate with CO₂ than O₂ but differently for each type of tubing. For condition A, gas transfer was independent of the volume of the external tubing and was accurately measured by the displacement of the droplet in the lumen. In contrast, for condition B, the pressure variations were influenced by the volume of the tubing.     

无创正压通气治疗慢性阻塞性肺疾病呼吸衰竭伴意识障碍的疗效观察

目的观察无创正压通气（NPPV）治疗慢性阻塞性肺疾病（COPD）呼吸衰竭伴意识障碍患者的疗效。方法将入选的16例COPD呼吸衰竭伴意识障碍患者分为A组,16例意识障碍不明显患者分为B组。在常规治疗的基础上行双水平无创正压通气（BiPAP）,动态观察治疗前后动脉血气、Glasgow昏迷评分、NPPV天数、住院天数、最高IPAP、NPPV成功率、住院病死率及不良反应情况。结果 A组NPPV成功率和住院病死率分别为68.75%（11/16）和18.75%（3/16）,B组分别为81.25%（13/16）和12.5%（2/16）,差异无统计学意义（P均〉0.05）。A组最高IPAP均值较B组高6 cmH2O,且NPPV和总住院时间也较B组长3和7 d（P〈0.05或P〈0.01）。A组胃肠胀气和面部皮肤损伤较B组发生率高（68.75%比18.75%,25.0%比6.25%,P〈0.05）。结论 NPPV对COPD呼吸衰竭伴意识障碍患者也有较好的疗效,意识障碍不是NPPV治疗的绝对禁忌症。     

不同药物对急性中毒性肾衰家兔作用效果的比较

目的观察10%葡萄糖、0.9%氯化钠溶液、肾上腺素对急性中毒性肾衰家兔的作用效果。方法制备家兔急性中毒性肾衰模型,观察急性中毒性肾衰状态下家兔动脉血压、心率、血尿素氮、血清肌酐的变化,以及注射10%葡萄糖、0.9%氯化钠溶液、肾上腺素对肾衰家兔动脉血压、心率、血尿素氮、血清肌酐的影响。对比肾衰前后以及肾衰后各药物注射后家兔的生命体征变化。结果肾衰家兔与正常家兔相比动脉血压下降,心率略下降,血清尿素氮、肌酐明显上升;肾衰家兔注射葡萄糖后动脉血压和心率都基本不变,血清尿素氮、肌酐略上升;注射0.9%氯化钠溶液后血压升高,心率略升高,血清尿素氮、肌酐略下降;注射肾上腺素后动脉血压上升,心率下降,血清尿素氮、肌酐明显下降。结论肾上腺素对急性中毒性肾衰家兔的治疗效果最佳。     

Recent Advances and Future Directions of Hypothermia Therapy for Traumatic Brain Injury

For severe traumatic brain injury (TBI) patients, no effective treatment method replacing hypothermia therapy has emerged, and hypothermia therapy still plays the major role. To increase its efficacy, first, early introduction is important. Since there are diverse pathologies of severe TBI, it is necessary to appropriately control the temperature in the hypothermia maintenance and rewarming phases by monitoring relative to the pathology. Currently, hypothermia is considered appropriate for severe TBI patients requiring craniotomy for removal of hematoma, while induced normothermia is appropriate for severe TBI patients with diffuse brain injury. Induced normothermia is expected to exhibit a cerebroprotective effect equivalent to hypothermia, as well as reduce the complexity of whole-body management and systemic complications. According to the Japan Neurotrauma Data Bank of the Japan Society of Neurotraumatology, the brain temperature was controlled in 43.9% of severe TBI patients (induced normothermia: 32.2%, hypothermia: 11.7%) in Japan. Brain temperature management was performed mainly in young patients, and the outcome on discharge was favorable in patients who received brain temperature management. Particularly, patients who need craniotomy for removal of hematoma were a good indication of therapeutic hypothermia. Improvement of therapeutic outcomes with widespread temperature management in TBI patients is expected.     

Continuous Measurement of O2 Consumption and CO2 Elimination During a Wakeful Hypometabolic State

Abstract

A previous investigation has demonstrated that the practice of a meditational technique elicits a wakeful, hypometabolic state. Measurement of O₂ consumption and CO₂ elimination was made by sampling techniques; mean values of these parameters were calculated from 6–10 minute samples. The present study extends this investigation, using a recently developed method of continuous measurement of O₂ consumption and CO₂ elimination. Continuous measurement of these parameters permitted the determination of mean values for the entire experimental periods as well as for selected intervals and permitted the examination of the sequence of respiratory changes. The present study reports statistically significant decreases in O₂ consumption of 5 percent and CO₂ elimination of 6 percent for the entire 20 minutes of the meditation period. These are lower than the sample values of 16 percent and 15 percent reported in the previous study. However, when selected intervals of the meditation period are examined, decreases in O₂ consumption and CO₂ elimination are comparable to those previously reported. The results are consistent with the difference between the discontinuous sampling measurement method originally employed and the continuous measurement method of the present investigation.     

Analysis of related factors affecting prognosis of shunt surgery in patients with secondary normal pressure hy- drocephalus

Objective： The management of se- condary normal pressure hydrocephalus （sNPH） is controversial. Many factors may affect the surgery effect. The purpose of this study was to identify the possible fac- tors influencing prognosis and provide theoretical basis for clinical treatment of sNPH. Methods： A retrospective study was carried out to investigate the results of 31 patients with sNPH who under- went ventriculoperitoneal shunt surgery from January 2007 to December 2011. We processed the potential influencing factors by univariate analysis and the result further by mul- tivariate logistic regression analysis. Results： Factors including age, disease duration and Glasgow coma scale （GCS） score before surgery significantly influenced the prognosis of sNPH （P〈0.05）. Further logistic regression analysis showed that all the three factors are independent influencing factors. Conclusion： Age, disease duration and GCS score before surgery have positive predictive value in estimating favorable response to surgical treatment for sNPH.     

Excessive Lowering of Blood Pressure Is Not Beneficial for Progression of Brain White Matter Hyperintensive and Cognitive Impairment in Elderly Hypertensive Patients: 4-Year Follow-Up Study

ObjectivesThis study was designed to explore the appropriate blood pressure (BP) target required to reduce cognitive decline and brain white matter lesions (WMLs) in elderly hypertensive patients.MethodsElderly patients (n = 294, ≥80 years of age) being treated for hypertension were enrolled in a longitudinal study examining cognitive impairment after an initial assessment and a period of 4 years. All patients underwent neurological and cognitive assessment, laboratory examination, and magnetic resonance imaging of the brain.ResultsThe 4-year follow-up examination revealed that body mass index, alcohol consumption, systolic blood pressure (SBP), diastolic blood pressure, and Mini-Mental State Examination (MMSE) all showed a significant decline, whereas fasting plasma glucose, white matter hyperintensities (WMH) volume, and the WMH/total intracranial volume (TIV) ratio were significantly increased when compared with baseline observations. Interestingly, the decline in MMSE, as well as the increment of WMH and WMH/TIV ratio was smaller in patients with SBP ranging from 140 to 160 mm Hg than in those whose SBP was lower than 140 mm Hg or higher than 160 mm Hg (P < .05). Furthermore, we observed that a 15 to 35 mm Hg targeted lowering of SBP in the elderly patients was more beneficial to our cognitive analysis than treatments that achieved less than 15 mm Hg or greater than 35 mm Hg (P < .05).ConclusionsIn elderly hypertensive patients, there exists a beneficial target for SBP lowering beyond which treatment may not be beneficial for improving or delaying the progression of cognitive impairment and WMLs.