The assessment of gas exchange by automated analysis of O2 and CO2 alveolar to arterial differences

Summary A computer program to measure breath by breath alveolar pressure (PA) and alveolar to arterial difference (AaD) for O₂ and CO₂, by a mass-spectrometer has been implemented. The program allows the determination of alveolar gas by different methods: 1. Bohr's equation (BE); 2. ideal alveolar air equation for O₂ (IDO₂); 3. end-tidal (ET); 4. by the Rahn's definition of mean alveolar gas, i.e., alveolar pressures are defined when instantaneous respiratory exchange ratio (IRQ) equals mean respiratory exchange ratio (MRQ). This automated technique has been used in 16 patients with chronic obstructive lung disease (COLD) and 15 patients with pulmonary embolism (APE). In both groups of patients it was always possible to find in each breath the point where IRQ=MRQ and therefore to measure AaD by RD. IDO₂ was significantly lower than PAO₂ by the other methods. Also ET values of O₂ and CO₂ were significantly different from RD and BE in both groups of patients, however the difference was consistently higher in COLD patients. The different shape of the expirograms (steeper expirograms in COLD) is responsible for this different result. RD and BE AaD characterize gas exchange more precisely than ET, because the contribution of high VA/Q units is also evaluated. This is particularly important in COLD patients.Consideration on dead space measurements are also reported both for COLD and APE patients. In conclusion this automated technique provides the assessment of gas exchange for the use in clinical respiratory physiology and for the monitoring of gas-exchange in critically ill patients.Abbreviations IRQ instantaneous respiratory exchange ratio - MRQ mean respiratory exchange ratio - ETRQ end-tidal respiratory exchange ratio - PE mean respiratory pressures - FE mean expiratory fractions - PA alveolar pressures - ETO₂, ETCO₂ end-tidal pressures of O₂ and CO₂ - RDO₂, RDCO₂ O₂ and CO₂ alveolar pressures according to Rahn's definition - BEO₂, BECO₂ O₂ and CO₂ alveolar pressures according to Bohr's equation - IDO₂ O₂ alveolar pressure according to ideal alveolar air equation - AaD alveolar to arterial differences - VDphy/VT% physiologic dead space using Enghoff equation - VDalv(Eng)% alveolar dead space subtracting from VDphy anatomical dead space predicted according to Hart et al (3) - VDalv(SE)% alveolar dead space using the index proposed by Severinghaus and Stupfel (4) - VDalv(Ro)% alveolar dead space using the correction proposed by Robin et al. (5)     

Transtracheal O2 insufflation (TOI) as an alternative method of ventilation during cardiopulmonary resuscitation

We examined the efficiency of continuous transtracheal O₂ insufflation (TOI) as a method of ventilation during cardiopulmonary resuscitation (CPR) in a canine model. The tip of the insufflation catheter was placed 1 cm above the carina. The effects of TOI at flow rates of 0.2, 0.5, and 1.01/kg per min during and after CPR were examined in dogs with induced ventricular fibrillation. During CPR, adequate oxygenation and ventilation were maintained with TOI at flow rates of 0.5 and 1.0 1/kg per min, but not at 0.21/kg per min. After CPR, TOI was adequate to maintain oxygenation, but not ventilation. TOI alone did not prevent post-CPR hypercarbia in successfully resuscitated animals. Still, this study suggests that TOI might be useful as a temporary measure for emergency ventilation during CPR, especially in situations such as upper airway abnormalities, when mask ventilation or endotracheal intubation is not feasible.     

Prostaglandin E2 (PGE2) induces headache in healthy subjects

The role of prostanoids in nociception is well established. The headache-eliciting effects of prostaglandin E₂ (PGE₂) and its possible mechanisms have previously not been systematically studied in man. We hypothesized that infusion of PGE₂ might induce headache and vasodilation of cranial vessels. PGE₂ (0.40 µg kg⁻¹ min⁻¹) or saline was infused for 25 min into 11 healthy subjects in a cross-over, double-blind study. Headache intensity was scored on a verbal rating scale from 0 to 10. In addition, we recorded mean flow in the middle cerebral artery (V_MCA) by transcranial Doppler and diameter of the superficial temporal artery (STA) by high-resolution ultrasonography. All 11 subjects reported headache on the PGE₂ day and no subjects reported headache on the placebo day ( P  = 0.001). During the immediate phase (0–30 min) ( P  = 0.005) and the postinfusion phase (30–90 min) ( P  = 0.005), the area under the curve for headache score was significantly larger on the PGE₂ day compared with the placebo day. PGE₂ caused dilatation of the STA (23.5%; 95% CI 14.0, 37.8) and the MCA (8.3%; 95% CI 4.0, 12.6). We suggest that PGE₂ induces headache by activation and sensitization of cranial perivascular sensory afferents.     

The Serology of Rho Variants (Rho)

Eighty-two Rh_o samples were tested with a battery of ten anti-Rh_o sera by the antiglobulin, bromelin and albumen replacement technics. The varying ability of different anti-Rh_o sera to react with Rh_o variant cells was clearly demonstrated. Anti-Rh_o used for the detection of Rh_o variants should be specially selected for this purpose. It is suggested that the Rh_o factor results from a genetically determined absence or abnormality of the primary Rh_o factor, and the serologic reactions characterizing it are dependent on the reactions of the subsidiary factors Rh^A, Rh^B, Rh^C, and Rh^D.     

血液透析患者血浆PGE2含量与T细胞亚群和NK细胞活性的关系

目的探讨血液透析患者外周血前列腺素E2(PGE2)含量与T细胞亚群和NK细胞活性的关系.方法应用流式细胞仪和酶联免疫分析法检测透析、未透析和长期维持性透析(透析时间大于7年)患者外周血PGE2、T细胞表面CD3、及其亚群CD4及CD8抗原表达.结果尿毒症未透析组(NHD组)的外周血 NK细胞和T细胞的CD3+、CD4+、CD8+表达及CD4+/CD8+比值均显著低于正常对照组(P<0.05); PGE2含量明显增高,并与CD4+/CD8+细胞比值和NK细胞活性间呈负相关.透析后,尿毒症患者PGE2水平降低,CD3+、CD4+和CD8+值及CD4/+CD8+比值均显著上升(P<0.05), NK细胞活性接近于正常对照组.然而透析时间大于7年的尿毒症患者血浆PGE2水平又显著增高,外周血淋巴细胞数值、CD3+细胞浓度、CD4+/CD8+细胞比值及NK细胞活性均显著低于正常组(P均<0.05).结论PGE2异常增高与细胞免疫功能失衡有关,血液透析能够降低PGE2浓度,改善患者的免疫功能.但长期维持性透析患者免疫功能又呈现恶化状态.     

超声造影评估脑梗死与非脑梗死患者颈动脉滋养血管新生的特点及其一致性研究

【】 目的 探讨超声造影评估脑梗死与非脑梗死患者颈动脉滋养血管新生特点及其一致性。 方法 对47例脑梗死患者和18例非脑梗死患者双侧颈动脉进行超声造影检查,对颈动脉滋养血管进行分级并进行一致性评估。 结果 脑梗死患者梗死侧颈动脉滋养血管以I级为主,与脑梗死非梗死侧和非脑梗死双侧颈动脉滋养血管分级差异明显(P分别为0.0104,0.0005,0.0085),而非脑梗死和脑梗死非梗死侧颈动脉滋养血管以0级为主,三者间分级差异无统计学意义(P分别为0.4795,0.2425,0,6889);入选者I级滋养血管患者中脑梗死的比例明显高于0级滋养血管患者(P=0.0001);以颈动脉滋养血管I级为标准评价脑梗死的敏感性和特异性分别为72.3%,61.5%(AUC=0.669),受试者之间评估颈动脉滋养血管新生的一致性均较佳。 结论 脑梗死与非脑梗死的颈动脉滋养血管分级差异明显,颈动脉滋养血管分级是预测脑梗死的一个有效指标。     

P（v-a）CO 2/C（a-v）O 2 ratio在休克复苏中的临床应用进展

静脉-动脉二氧化碳分压差/动脉-静脉氧含量差[P（v-a）CO₂/C（a-v）O₂ ratio]通过计算氧的消耗量和二氧化碳的生成量的比率获得,其本质是反映机体呼吸商。在无氧代谢时只有CO₂的产生,却无O₂的消耗,此时呼吸商趋向无限大。因此,当机体存在无氧代谢时,可出现P（v-a）CO₂/C（a-v）O₂ ratio增高。近来,应用P（v-a）CO₂/C（a-v）O₂ ratio作为识别机体是否存在无氧代谢的指标在休克复苏中受到广泛关注。     

Pharmacological control of the human gastric histamine H2 receptor by famotidine: comparison with H1, H2 and H3 receptor agonists and antagonists

Histamine 0.1 microM-0.1 mM increased adenylate cyclase activity five- to ten-fold in human fundic membranes, with a potency Ka = 3 microM. The histamine dose-response curve was mimicked by the H3 receptor agonist (R) alpha-MeHA, but at 100 times lower potency, Ka = 0.3 mM. Histamine-induced adenylate cyclase activation was abolished by H2, H1 and H3 receptor antagonists, according to the following order of potency IC50: famotidine (0.3 microM) greater than triprolidine (0.1 mM) thioperamide (2 mM), respectively. Famotidine has no action on membrane components activating the adenylate cyclase system, including the Gs subunit of the enzyme stimulated by forskolin and cell surface receptors sensitive to isoproterenol (beta 2-type), PGE2 and VIP. The Schild plot was linear for famotidine (P less than 0.01) with a regression coefficient r = 0.678. The slope of the regression line was 0.64 and differs from unity. Accordingly, famotidine showed a slow onset of inhibition and dissociation from the H2 receptor in human cancerous HGT-1 cells. The results demonstrate that famotidine is a potent and selective H2 receptor antagonist with uncompetitive actions in human gastric mucosa. Consequently, famotidine might be a suitable drug with long-lasting actions in the treatment of Zollinger-Ellison syndrome. The results also confirm and extend the previous observations that (R) alpha-MeHA and thioperamide are two selective ligands at histamine H3 receptor sites. In the human gastric mucosa, these drugs are respectively 330 and 6700 times less potent than histamine and famotidine on the adenylate cyclase system. The possible involvement of histamine H3 receptors in the regulation of gastric secretion is proposed.     

P（cv-a）CO 2/C（a-v）O 2 ratio在感染性休克早期目标导向性复苏中的潜在价值

目的探讨中心静脉血二氧化碳分压-动脉血二氧化碳分压差/动脉血氧含量-静脉血氧含量差［P（cv-a）CO₂/C（a-v）O₂ ratio］在感染性休克早期目标导向性复苏中的应用。 方法收集自2018年6月至2019年6月在新疆维吾尔自治区人民医院ICU接受治疗的感染性休克患者44例。根据P（cv-a）CO₂/C（a-v）O₂ ratio值将患者分为A、B 2组,其中A组为P（cv-a）CO₂/C（a-v）O₂ ratio＜1.6,B组为P（cv-a）CO₂/C（a-v）O₂ ratio≥1.6。比较2组患者的基线资料［性别、年龄、感染部位、急性生理学与慢性健康状况（APACHE Ⅱ）评分与序贯器官衰竭评估（SOFA）评分］、基本参数［中心静脉压（CVP）、平均动脉压（MAP）、小时尿量、血管活性药物使用量、24 h出入量、血红蛋白、乳酸水平］、氧代谢参数［0、6、12、24 h的动脉血氧分压（PaO₂）,动脉血氧饱和度（SaO₂）,中心静脉血氧分压（PcvO₂）,中心静脉血氧饱和度（ScvO₂）,P（cv-a）CO₂（gap）,P（cv-a）CO₂/C（a-v）O₂ ratio,氧合指数,氧摄取率,及6、12 h的乳酸清除率］及转归［血管活性药物使用时间,机械通气时间,24、48、72、96 h的APACHEⅡ评分和SOFA评分,住ICU时间,住院时间,28 d病死率］等数据。 结果2组患者基线资料比较差异无统计学意义（P＞0.05）。0 h 2组间P（cv-a）CO₂/C（a-v）O₂ ratio、氧分压、氧合指数、氧摄取率、乳酸、P（cv-a）CO₂（gap）比较,差异均有统计学意义（P＜0.05）;6 h 2组间乳酸清除率比较,差异有统计学意义（P＜0.05）。2组间1、3、5、7 d APACHE Ⅱ评分、SOFA评分、血管活性药物使用时间（去甲肾上腺素）、机械通气时间、住ICU时间、住院时间及28 d病死率比较,差异均无统计学意义（P＞0.05）。 结论P（cv-a）CO₂/C（a-v）O₂ ratio在感染性休克早期目标导向性复苏中可作为补充指标,评价组织乏氧代谢,指导治疗。