Non‐invasive positive pressure ventilation during sleep at 3800 m: Relationship to acute mountain sickness and sleeping oxyhaemoglobin saturation

Background and objective: Ascent to high altitude results in hypobaric hypoxia and some individuals will develop acute mountain sickness (AMS), which has been shown to be associated with low oxyhaemoglobin saturation during sleep. Previous research has shown that positive end‐expiratory pressure by use of expiratory valves in a face mask while awake results in a reduction in AMS symptoms and higher oxyhaemoglobin saturation. We aimed to determine whether positive pressure ventilation would prevent AMS by increasing oxygenation during sleep. Methods: We compared sleeping oxyhaemoglobin saturation and the incidence and severity of AMS in seven subjects sleeping for two consecutive nights at 3800 m above sea level using either non‐invasive positive pressure ventilation that delivered positive inspiratory and expiratory airway pressure via a face mask, or sleeping without assisted ventilation. The presence and severity of AMS were assessed by administration of the Lake Louise questionnaire. Results: We found significant increases in the mean and minimum sleeping oxyhaemoglobin saturation and decreases in AMS symptoms in subjects who used positive pressure ventilation during sleep. Mean and minimum sleeping SaO₂ was lower in subjects who developed AMS after the night spent without positive pressure ventilation. Conclusions: The use of positive pressure ventilation during sleep at 3800 m significantly increased the sleeping oxygen saturation; we suggest that the marked reduction in symptoms of AMS is due to this higher sleeping SaO₂. We agree with the findings from previous studies that the development of AMS is associated with a lower sleeping oxygen saturation.     

Why High-Intensity NPPV is Favourable to Low-Intensity NPPV: Clinical and Physiological Reasons

High-intensity non-invasive positive pressure ventilation (NPPV) was originally described for chronic hypercapnic chronic obstructive pulmonary disease (COPD) patients in 2009, and refers to a specific ventilatory approach whereby NPPV settings are aimed at achieving the lowest arterial partial pressure of carbon dioxide (PaCO₂) values possible. Thus, high-intensity NPPV requires ventilator settings to be increased in a stepwise approach to either an individually tolerated maximum, or to the levels necessary to achieve normocapnia. This differs from the classic approach to low-intensity NPPV, which comprises considerably lower ventilator settings and typically fails to lower elevated PaCO₂ values. The ongoing discussion about whether or not long-term NPPV should be used in chronic hypercapnic COPD patients is based on the observation that many studies in the last two decades have failed to provide evidence for this particular patient cohort. In addition, these trials preferably used low-intensity NPPV. There is now, however, increasing evidence to suggest that high-intensity NPPV is capable of improving important physiological parameters such as blood gases and lung function, as well as health-related quality of life. Moreover, this approach also produced positive outcomes following two recent randomized controlled trials, e.g., improved survival rates in stable COPD patients, and admission-free survival in patients with persisting hypercapnia following acute in-hospital NPPV to treat acute acidotic respiratory failure. As a consequence, the time has now come to evaluate the impact of long-term NPPV on both the physiological and clinical outcomes, with emphasis on the different approaches to NPPV. Therefore, the aim of the current review article is to elaborate on the clinical and physiological reasons for why high-intensity NPPV is favourable to low-intensity NPPV.     

Differential effects of melatonin on amyloid‐β peptide 25–35‐induced mitochondrial dysfunction in hippocampal neurons at different stages of culture

Abstract: β‐Amyloid (Aβ) is strongly involved in the pathogenesis of Alzheimer’s disease (AD), and mitochondria play an important role in neurodegenerative disorders. To determine whether any different effect of melatonin on cultured neurons treated with Aβ in vitro and which may be produced through its different action on mitochondria at different stages of culture, we investigated the damage of cultured rat hippocampal neurons mitochondrial function induced by Aβ in young neurons [days in vitro 10 (DIV 10)] and senescent neurons (DIV 25) and the protective effect of melatonin. Rat hippocampal neurons were incubated with amyloid‐β peptide 25–35 (Aβ25‐35) alone or pretreatment with melatonin. Cell viability, mitochondrial membrane potential (Δψm), ATP and the activity of the respiratory chain complexes were measured. Data showed that Aβ25‐35 caused a reduction in Δψm, inhibited the activity of the respiratory chain complexes and led to ATP depletion, melatonin attenuated Aβ25‐35‐induced mitochondrial impairment in young neurons, whereas melatonin had no effect on Aβ25‐35‐induced mitochondrial damage in senescent neurons. These results demonstrate that melatonin has differential effect on Aβ25‐35‐induced mitochondrial dysfunction at different stages of culture and suggest that melatonin is useful for the prevention of AD, rather than treatment.     

鼻塞式呼吸机间歇指令通气联合肺表面活性物质治疗早产儿肺透明膜病的临床研究

Objective To evaluate the effect of nasal intermittent mandatory ventilation (NIMV)combined with pulmonary surfactant for the treatment of hyaline membrane disease in premature children and to compare the clinical efficacy with conventional mechanical ventilation and continuous positive airway pressure (CPAP). Methods Seventy-four babies with severe respiratory syndrome were given curosurf[100 mg/(kg·dose)],25 of them were given to NIMV, another 25 were given conventional intermittent mandatory ventilation (IMV), the last 24 patients were given conventional CPAP. Blood gas analysis parameters and incidences of respiratory complications including respiratory tract infection and chronic lung disease,frequent apnea and carbon dioxide retention, were compared among the three groups. Results After treatment of 1 h, symptoms and signs of the patients markedly improved. All the three groups showed an increase in arterial oxygen partial pressure, but arterial pressure of carbon dioxide and oxygen index decreased significantly by the time of 6,12,24 h after treatment and there were not significantly difference among the three groups. The rates of respiratory infection and chronic lung disease in NIMV group were less than that of conventional IMV group[(8% vs 36% ) ,(20% vs 72% )],the rates of frequent apnea and carbon dioxide retention in NIMV group were less than that of CPAP group[(8% vs 36% ), (20% vs 72% )]. Conclusion NIMV combined with pulmonary surfactant is a potentially efficient therapy for hyaline membrane disease in premature infants. NIMV treatment of hyaline membrane disease in premature infants can reduce or avoid ventilation-associated pneumonia,chronic lung disease and other complications,but also efficiently reduce the incidence of frequent apnea and carbon dioxide retention.     

大鼠视网膜神经元的原代培养方法

目的:探求视网膜神经元的最佳分离和培养方法,提高原代培养神经元的纯度及活性。方法:采用新生大鼠视网膜神经元,应用含100mL/L新生牛血清、100g/LF-12 Nutrient Mixtures的DMEM培养基进行接种培养,含20g/LB-27 Serum-Free Supplements的Neurobasal Medium进行维持培养,利用尼氏染色进行神经元鉴定。结果:培养的神经元生长良好,胞体饱满,突起长。尼氏染色示神经元比例大于90%。结论:采用机械分离法和Neurobasal Medium培养基可以使新生大鼠视网膜神经元得到良好的生长和较高的纯度。     

Repeatability and agreement in the measurement of horizontal fusional vergences

PURPOSE: This study was designed to determine the repeatability of fusional vergence ranges measured using the rotary prisms in the phoropter and in free space using the prism bar. The level of agreement between the two methods was also investigated. METHODS: In two separate sessions, negative and positive fusional vergence ranges (NFV and PFV, respectively) were measured at distance and near in 61 young adults (mean age 19.74, S.D. 2.5 years) who were unfamiliar with the methods used. Base-in and base-out blur, break and recovery points were sequentially determined. Both sets of measurements were obtained by the same examiner. At each distance, NFV was determined first and then PFV. The repeatability of the tests and agreement between measurements made with the phoropter rotary prisms and the prism bar were estimated by the Bland and Altman method. RESULTS: For both the phoropter rotary prisms and prism bar, NFV measurements showed better repeatability than PFV at both near and distance. Mean differences recorded for the NFV break and recovery points were non-significant (under 0.5Delta), while those observed for PFV were generally greater than 2Delta. When agreement between the two tests was assessed, it was found that break points were higher when determined using the phoropter rotary prisms, while recovery points were generally higher for the prism bar method. In clinical terms, according to the expected values of the NFV and PFV, agreement between the two techniques can be described as fair, because although mean differences were never greater than 5.5Delta, 95% agreement intervals were as wide as +/-8.00Delta for NFV and +/-13.19Delta for PFV. CONCLUSIONS: The two methods used to measure fusional vergences showed fairly good inter-session repeatability for measuring NFV but repeatability was reduced for PFV measurements. The level of agreement observed between the two methods was such that their interchangeable use in clinical practice is not recommended.     

化学物的神经毒性体外评价方法

神经系统毒性反应是药物常见的毒性反应。神经系统对外源性和内源性毒性物质的攻击都十分敏感,因而毒性作用的结果也可能较其他系统更为严重。神经毒性的体外评价主要用于药物筛选的早期阶段以及毒性机制研究。神经毒性的体外评价以各种培养的细胞和组织模型为基础,随着体外培养的复杂程度增加,培养物与活体内组织的相似性越高。体外评价的终点包括一般细胞毒性指标、神经轴突生长的形态学指标和反映特异神经毒性的指标。     

吗啡条件性位置偏爱大鼠脑伏核中CaMK Ⅱ及NOS阳性神经元变化

目的:研究吗啡条件性位置偏爱(CPP)大鼠伏核中CaMK Ⅱ及NOS的阳性神经元变化。方法:采用免疫组织化学实验方法观察CaMK Ⅱ及NOS阳性神经元的形态及数目的变化。结果:与正常对照组比较,吗啡模型组CaMK Ⅱ及NOS的阳性神经元数均明显升高(P<0.01)。结论:吗啡CPP大鼠伏核中显示CaMK Ⅱ及NOS的阳性神经元增多,参与了吗啡精神依赖的形成。