机械通气患者呼气流速受限危险因素分析及其对患者预后的影响

目的 评估重症医学科机械通气患者中呼气流速受限的发病率，并确定与呼气流速受限相关的主要临床特征、危险因素和对患者预后的影响。方法 选取需要机械通气的患者202例，通过呼气末正压通气(PEEP)试验分为呼气流速受限组和非呼气流速受限组，在患者行机械通气12小时内测定呼吸力学指标，每日测定呼吸力学指标，连测3日。所有患者均行简化急性生理状态评分系统(SAPS)评分和器官衰竭评分(SOFA)；改良的英国医学委员会呼吸困难评分量表（mMRC）评定呼吸困难严重程度。结果 22.77%的患者存在为呼气流速受限，其中脓毒性休克39例、ARDS 25例、失血性休克27例、慢性阻塞性肺疾病急性恶化32例、急性呼吸衰竭45例、心力衰竭12例和脑血管病合并肺炎22例。呼气流速受限患者的体重指数(BMI)较高，呼气流速受限与心脏病史、慢性肺病史有关(均P<0.05)。呼吸力学数据方面，呼气流速受限患者呼吸困难评分较差，最大气道阻力高，弹性阻力增加，具有较高的呼气末正压和内源性呼气末正压，峰值压较高，氧合指数较低(均P<0.05)。呼气流速受限组患者SOFA评分、SAPSⅡ评分均较高，机械通气时间更长，具有更高的病死率(均P<0.05)。结论 BMI高、肺病或心脏病史是重症医学科机械通气患者呼气流速受限的高危因素。呼气流速受限患者的呼吸力学参数更差。呼气流速受限患者机械通气时间较长，住院时间较长，病死率较高，预后差。     

Respiratory support in children

Respiratory failure is defined by the inability of the respiratory system to adequately deliver oxygen or remove carbon dioxide from the pulmonary circulation resulting in hypoxemia, hypercapnia or both. A wide variety of disease processes can lead to respiratory failure in children. Multiple interventions can support the paediatric patient with respiratory failure, from simple oxygen delivery devices to high frequency oscillatory ventilation and extracorporeal membrane oxygenation. This article will review available devices to improve oxygenation and ventilation, their advantages and disadvantages, and help guide physicians in the management of children with respiratory failure.     

Maternal sensitivity and infant autonomic and endocrine stress responses

Background

Early environmental exposures may help shape the development of the autonomic nervous system (ANS) and hypothalamic–pituitary–adrenal (HPA) axis, influencing vulnerability for health problems across the lifespan. Little is known about the role of maternal sensitivity in influencing the development of the ANS in early life.

Aims

To examine associations among maternal sensitivity and infant behavioral distress and ANS and HPA axis reactivity to the Repeated Still-Face Paradigm (SFP-R), a dyadic stress task.

Study design

Observational repeated measures study.

Subjects

Thirty-five urban, sociodemographically diverse mothers and their 6-month-old infants.

Outcome measures

Changes in infant affective distress, heart rate, respiratory sinus arrhythmia (RSA), and T-wave amplitude (TWA) across episodes of the SFP-R were assessed. A measure of cortisol output (area under the curve) in the hour following cessation of the SFP-R was also obtained.

Results

Greater maternal insensitivity was associated with greater infant sympathetic activation (TWA) during periods of stress and tended to be associated with greater cortisol output following the SFP-R. There was also evidence for greater affective distress and less parasympathetic activation (RSA) during the SFP-R among infants of predominantly insensitive mothers.

Conclusions

Caregiving quality in early life may influence the responsiveness of the sympathetic and parasympathetic branches of the ANS as well as the HPA axis. Consideration of the ANS and HPA axis systems together provides a fuller representation of adaptive versus maladaptive stress responses. The findings highlight the importance of supporting high quality caregiving in the early years of life, which is likely to promote later health.     

Role of mastication and swallowing in the control of autonomic nervous activity for heart rate in different postures

Mastication and swallowing increase the heart rate, and posture change and respiration also modulate the heart rate. To clarify the role of mastication and swallowing in the modulation of the autonomic nervous activity, we investigated how they interact with modulation of the heart rate by changing body positions and respiration in young healthy subjects. R-R intervals of electrocardiogram at rest were significantly changed with different body positions, compared with supine and standing. A net shortening by mastication of a chewing gum base was similar in various postures. Respiration induced a periodic change in the R-R intervals, depending on the body postures, but mastication did not markedly change them in each posture. Dry swallowing at rest and spontaneous swallowing during the mastication in the sitting position induced a similar transient shortening and suppressed the respiration-induced changes after the swallowing. The net transient shortening by dry swallowing at rest was similar in the different postures. These results suggest that signals from mastication and swallowing are summated with those from body positions and respiration for shortening the R-R intervals and that signals from swallowing suppress the respiration-induced periodic changes.     

中医五音疗法配合缩唇腹式呼吸肌功能锻炼在气管切开患者护理中的应用

目的:观察中医五音疗法配合缩唇腹式呼吸肌功能锻炼对治疗气管切开患者的临床疗效。方法:选取2012年1月—2013年12月在本院接受治疗的气管切开患者共50例,随机分为观察组与对照组,每组各25例。对照组采用常规缩唇腹式呼吸肌进行呼吸肌功能锻炼的护理方式,观察组采用中医五音疗法配合缩唇腹式呼吸肌功能锻炼对气管切开患者进行护理干预,比较两组患者撤去呼吸机情况,满意度以及生活质量情况。结果:对照组撤去呼吸机的成功率为60%,观察组的成功率为100%,两组成功率比较,差异具有统计学意义(P0.05)。两组患者治疗后满意度及生活质量评分均高于治疗前,且观察组高于对照组,差异均有统计学意义(P0.05)。结论:中医五音疗法配合缩唇腹式呼吸肌功能锻炼护理气管切开患者可提高患者的生活质量,增加患者的满意度。     

Effect of mother's voice on neonatal respiratory activity and EEG delta amplitude

While the influence of the mother's voice on neonatal heart‐rate response and its relevant activity on cerebral cortex and the autonomic nervous system (ANS) are well known, few studies have assessed its influence on respiratory activity. We investigated the relationship among the respiration rate, the delta wave amplitudes through electroencephalography, and the basal state of ANS through the respiratory variability index while 22 full‐term neonates hear their mother's voice and an unknown voice. It was found that when respiratory variability was large, a transient (<5 s) change in respiration rates was observed in response to an unknown voice, while a greater increase in the delta wave amplitude was observed in the frontal lobe than the parietal one in response to the mother's voice. Conversely, when respiratory variability was small, a sustained increase (>10 s) in respiration rates was observed in response to the mother's voice, while a greater increase in the delta wave amplitude was found in both the frontal and parietal lobes. These results suggest that the basal state of ANS influences the latency of increases in respiration rates. Furthermore, induced by the mother's voice, transient increases in respiration rates are reduced in association with frontal lobe activity, and sustained increases in respiration rates are promoted in association with frontal and parietal lobe activities.     

Iron oxides stimulate sulfate-driven anaerobic methane oxidation in seeps

Seep sediments are dominated by intensive microbial sulfate reduction coupled to the anaerobic oxidation of methane (AOM). Through geochemical measurements of incubation experiments with methane seep sediments collected from Hydrate Ridge, we provide insight into the role of iron oxides in sulfate-driven AOM. Seep sediments incubated with ¹³C-labeled methane showed co-occurring sulfate reduction, AOM, and methanogenesis. The isotope fractionation factors for sulfur and oxygen isotopes in sulfate were about 40‰ and 22‰, respectively, reinforcing the difference between microbial sulfate reduction in methane seeps versus other sedimentary environments (for example, sulfur isotope fractionation above 60‰ in sulfate reduction coupled to organic carbon oxidation or in diffusive sedimentary sulfate–methane transition zone). The addition of hematite to these microcosm experiments resulted in significant microbial iron reduction as well as enhancing sulfate-driven AOM. The magnitude of the isotope fractionation of sulfur and oxygen isotopes in sulfate from these incubations was lowered by about 50%, indicating the involvement of iron oxides during sulfate reduction in methane seeps. The similar relative change between the oxygen versus sulfur isotopes of sulfate in all experiments (with and without hematite addition) suggests that oxidized forms of iron, naturally present in the sediment incubations, were involved in sulfate reduction, with hematite addition increasing the sulfate recycling or the activity of sulfur-cycling microorganisms by about 40%. These results highlight a role for natural iron oxides during bacterial sulfate reduction in methane seeps not only as nutrient but also as stimulator of sulfur recycling.Microbial dissimilatory processes generate energy through the decomposition of substrates, whereas assimilatory processes use substrates for intracellular biosynthesis of macromolecules. The most known and energetically favorable dissimilatory process is the oxidation of organic carbon coupled to oxygen as terminal electron acceptor (Eq. 1). In sediments with a high supply of organic carbon, oxygen can be depleted within the upper few millimeters, leading to anoxic conditions deeper in the sediment column. Under these conditions, microbial dissimilatory processes are coupled to the reduction of a series of other terminal electron acceptors besides oxygen (1). The largest free-energy yields are associated with nitrate reduction (denitrification), followed by manganese and iron oxide reduction, and then sulfate reduction. Due to the high concentration of sulfate in the ocean, dissimilatory bacterial sulfate reduction (Eq. 2) is responsible for the majority of organic matter oxidation in marine sediments (2). Below the depth of sulfate depletion, traditionally the only presumed process is methanogenesis (methane production), where its main pathways are fermentation of organic matter, mainly acetate (Eq. 3), or the reduction of carbon dioxide with hydrogen as substrate (Eq. 4) (3):O₂ + CH₂O → H₂O + CO₂[1]SO42−+2CH2O→H2S+2HCO3−[2]CH₃COOH→CH₄ + CO₂[3]CO₂ + 4H₂→CH₄ + 2H₂O[4]When methane that has been produced deep in sediments diffuses into contact with an available electron acceptor, it can be oxidized (methanotrophy). Methanotrophy is the main process that prevents the escape of methane produced within marine and fresh water sediments into the atmosphere. In fresh water systems, methanotrophic bacteria are responsible for oxidizing methane to dissolved inorganic carbon (DIC) typically using oxygen as an electron acceptor (4, 5). In marine sediments, however, where oxygen diffusion is limited, anaerobic oxidation of methane (AOM) coupled to sulfate reduction [e.g., refs. 6 and 7 (Eq. 5)] has been shown to consume up to 90% of the methane produced within the subseafloor environment (8). Often, when methane is present, the majority of sulfate available in marine pore fluids is reduced through sulfate-driven AOM (9–13):CH4+SO42−→HS−+HCO3−+H2O.[5]Other electron acceptors such as nitrate and oxides of iron and manganese, could also oxidize methane anaerobically and provide a greater free-energy yield than sulfate-coupled methane oxidation (14). Indeed, Beal et al. (15) showed the potential for iron- and manganese-driven AOM in microcosm experiments with methane seep sediments from Eel River Basin and Hydrate Ridge, and iron-driven AOM has been interpreted from modeling geochemical profiles in deep-sea sediments (13, 16). AOM has been shown to occur in nonmarine sediments via denitrification (17–21) and iron reduction (22, 23). However, all geochemical and microbiological studies point to sulfate-driven AOM as the dominant sink for methane in marine sediments.Sulfate-driven AOM is understood to involve microbial consortia of archaea and bacteria affiliated with archaeal methanotrophs (“methane oxidizers”) and sulfate-reducing bacteria (11, 24). A common view is that anaerobic methanotrophic archaea (ANME) oxidize methane, while the sulfate-reducing syntrophic partner scavenges the resulting reducing equivalents to reduce sulfate to sulfide (7, 25, 26). Recently, however, cultured AOM enrichments from seeps were reported to be capable of direct coupling of methane oxidation and sulfate reduction by the ANME-2 archaea, with the passage of zero valent sulfur to a disproportionating bacterial partner, capable of simultaneously oxidizing and reducing this substrate to sulfate and sulfide in a ratio of 1:7, respectively (27). Whether this “single organism mechanism” for sulfate-driven AOM is widespread in the natural environment, or whether there is a diversity of mechanisms for sulfate-driven AOM, remains enigmatic.Carbon isotopes provide a good constraint on the depth distribution and location of methanogenesis and methanotrophy because of the carbon isotope fractionation associated with these processes (e.g., refs. 28 and 29). During methanogenesis, ¹²C is strongly partitioned into methane; the δ¹³C of the methane produced can be between −50‰ to −110‰. In parallel, the residual DIC pool in methanogenic zones becomes highly enriched in ¹³C, occasionally by as much as 50‰ to 70‰ (e.g., ref. 28). Oxidizing this methane on the other hand, results in ¹³C-depleted DIC and slightly heavier δ¹³C values of the residual methane, caused by a fractionation of 0‰ to 10‰ during methane oxidation and the initial negative δ¹³C value of the methane itself (30, 31).The sulfur and oxygen isotopes in dissolved sulfate (δ³⁴S_SO4 and δ¹⁸O_SO4) may also be a diagnostic tool for tracking the pathways of sulfate reduction by methane or other organic compounds. Sulfur isotope fractionation during dissimilatory bacterial sulfate reduction, which partitions ³²S into the sulfide, leaving ³⁴S behind in the residual sulfate, can be as high as 72‰ (32–35). As sulfate is reduced to sulfide via intracellular intermediates (34, 36–40), the magnitude of this sulfur isotope fractionation depends upon the isotope partitioning at each of the intercellular steps and on the ratio between the backward and forward sulfur fluxes within the bacterial cells (34, 36).Oxygen isotopes in sulfate, however, have been shown to be strongly influenced by the oxygen isotope composition of water in which the bacteria are grown (41–45). The consensus is that, within the cell, sulfur compounds, such as sulfite, and water exchange oxygen atoms; some of these isotopically equilibrated molecules return to the extracellular sulfate pool. As all of the intercellular steps are considered to be reversible (e.g., refs. 34, 36, 46, and 47), water–oxygen is also incorporated during the oxidation of these sulfur intermediates back to sulfate (41–43, 48–51).Therefore, both oxygen and sulfur isotopes in the residual sulfate during dissimilatory sulfate reduction are affected by the changes in the intracellular fluxes of sulfur species. However, these isotopes in the residual sulfate are affected in different ways, and thus the change of one isotope vs. the other helps uniquely solve for the relative change in the flux of each intracellular step as sulfate is being reduced (42, 43, 50). The sulfur and oxygen isotope composition of residual sulfate has been used to explore the mechanism of traditional (organoclastic) sulfate reduction both in pure culture (e.g., refs. 44, 45, and 52) and in the natural environment (e.g., refs. 12, 49, 50, and 53–55). The coupled isotope approach has been used specifically to study sulfate-driven AOM recently in estuaries (56). In the work of Antler et al. (56), it was shown that the oxygen and sulfur isotopes in the residual sulfate in the pore fluids are linearly correlated during sulfate-driven AOM, whereas during organoclastic bacterial sulfate reduction, the isotopes exhibit a concaved curve relationship.Although iron and manganese oxides should be reduced before the onset of dissimilatory bacterial sulfate reduction in the natural environment from thermodynamic considerations, due to their low solubility, they may not be completely reduced through dissimilatory respiration when sulfate reduction starts (e.g., ref. 22). These lower reactivity manganese and iron oxides therefore may still be present during the lower-energy yielding anaerobic processes such as sulfate reduction, methanotrophy, and methanogenesis. Indeed, iron oxides have been shown to serve as electron acceptors for methane oxidation even in the sulfate “zone” (15, 16, 22, 57), although the mechanism of this coupling remains enigmatic. In the context of deep-sea methane seep ecosystems, earlier work by Beal et al. (15) demonstrated stimulation of AOM by the addition of iron and manganese oxides in sediment incubation experiments. In that work, however, the nature of the coupling between methane oxidation and metal oxides was not ascertained, and the multiple links between the sediment sulfur, iron, and methane cycles are equivocal.Here, we conducted microcosm experiments with sediments collected from Hydrate Ridge South (Fig. S1) and used synergistic combinations of isotope analyses (δ³⁴S_SO4, δ¹⁸O_SO4, and δ¹³C_DIC) to aid in assessing whether methane oxidation is directly coupled to the respiration of iron oxides or whether stimulation in methanotrophy is a result of the coupling between iron and sulfate. We provide compelling evidence for the stimulation of AOM in seep sediments through the coupling between iron and sulfate, and propose a mechanism for iron involvement in sulfate-driven AOM. Using microcosm experiments with seep sediments dominated by sulfate-driven AOM and amended with hematite and ¹³C-labeled methane and glucose, we are able to demonstrate the role of iron in sulfate-driven AOM. Hematite is a less reactive form of iron oxide than, for example, amorphous iron (58), and it was used to prevent the microbial populations from “switching” completely to the more energetically favorable process of iron reduction.     

Tension pneumoperitoneum complicating cardiac resuscitation

A case of gastric rupture and tension pneumoperitoneum following cardiac resuscitation is presented. Respiratory embarrassment necessitated emergency decompression by needle puncture of the peritoneal cavity, followed by laparotomy and repair of the gastric tear. The post-operative course has been satisfactory. The eatiology of the gastric rupture is discussed and recommendations are made for the prevention and treatment of this unusual complication of combined mouth to mouth respiration and external cardiac massage.