Validation and Clinical Application of a First Order Step Response Equation for Nitrogen Clearance During FRC Measurement

Objective To derive a difference equation based on mass conservation and on alveolar tidal volumes for the calculation of Functional Residual Capacity. Derive an equation for the FRC from the difference equation. Furthermore, to derive and validate a step response equation as a solution of the difference equation within the framework of digital signal processing where the FRC is known a priori. Methods A difference equation for the calculation of Functional Residual Capacity is derived and solved as step response of a first order system. The step response equation calculates endtidal fractions of nitrogen during multiple breath nitrogen clearance. The step response equation contains the eigenvalue defined as the ratio of FRC to the sum of FRC and alveolar tidal ventilation. Agreement of calculated nitrogen fractions with measured fractions is demonstrated with data from a metabolic lung model, measurements from patients in positive pressure ventilation and volunteers breathing spontaneously. Examples of eigenvalue are given and compared between diseased and healthy lungs and between ventilatory settings. Results Comparison of calculated and measured fractions of endtidal nitrogen demonstrates a high degree of agreement in terms of regression and bias and limits of agreement (precision) in Bland & Altman analysis. Examples illustrate the use of the eigenvalue as a possible discriminator between disease states. Conclusion The first order step response equation reliably calculates endtidal fractions of nitrogen during washout based on a Functional Residual Capacity. The eigenvalue may be a clinically valuable index alone or in conjunction with other indices in the analysis of respiratory states and may aid in the setting of the ventilator. Conflict of interest: Gary Choncholas and Erkki Heinonen are employees in the company implementing the FRC algorithm in a critical care ventilator. Soren Sondergaard has lectured for and received economic support from the same company. Choncholas G, Sondergaard S, Heinonen E. Validation and clinical application of a first order step response equation for nitrogen clearance during FRC measurement.     

重组人生长激素在机械通气病人中的应用

目的 :探讨重组人生长激素 (rHGH )对外科术后需机械通气的病人的效果。方法 :6 0例术后呼吸衰竭需机械通气的病人 ,分为rHGH组和对照组各 30例 ,2组均接受ICU标准支持治疗 ,rHGH组每日肌内注射rHGH ,4～ 8IU。观察 2组机械通气时间 ,治疗期间血清清蛋白、血生化的峰值及胰岛素的用量。结果 :rHGH组机械通气时间为 (2 9±s13)d ,对照组为 (40± 14)d(P <0 .0 1)。rHGH组血清清蛋白浓度明显升高 (P <0 .0 1) ,血糖及胰岛素用量略有增加 ,血钙增加 (P <0 .0 5 )。rHGH组预测的死亡率为 4 3% ,实际死亡率 17% ,死亡率显著降低 (P <0 .0 5 )。结论 :rHGH能够显著缩短外科危重病人机械通气时间 ,撤机成功率增加 ,死亡率降低     

The early development of pediatric intensive care

The polio epidemic in Copenhagen in 1952 was a significant stimulus to the development of Intensive Care. Eighty-five percent of the patients with respiratory involvement died despite the use of Cuirass negative pressure ventilators. After some controversy Ibsen, an anesthetist, was consulted. He found that many patients were dying with CO(2) retention. He advocated tracheostomy, suction, and ventilation. Owing to the lack of positive pressure ventilators, this was undertaken by students who contributed 167,000 h of hand ventilation. The mortality decreased to 25%. Anesthetists, having special experience with ventilation, became the leaders in the field as Intensive Care developed.     

Evaluation of the Pneupac Ventipac portable ventilator in critically ill patients

We assessed adequacy of ventilation in 20 critically ill patients with multiple organ failure using a Pneupac Ventipac portable ventilator and the effects on patients' haemodynamic stability. Baseline data were recorded over 15 min for a range of respiratory, haemodynamic and oxygen transport variables during ventilation with a standard intensive care ventilator (Engstr?m Erica). Patients were then ventilated for 40 min using the portable ventilator. Finally, they were ventilated for a further 40 min using the standard intensive care ventilator. Heart rate, arterial and pulmonary artery pressures were recorded at 5-min intervals throughout the study period. Cardiac index and other haemodynamic data derived from a pulmonary artery catheter were recorded at 20-min intervals. Blood gas analysis was performed and oxygen transport data (oxygen delivery, oxygen consumption and physiological shunt) were calculated at the end of each of the three periods of ventilation. In general, no significant adverse effects of ventilation using the portable ventilator were observed for any of the variables studied. Arterial PO(2) increased significantly during ventilation with the portable ventilator, reflecting the use of a higher inspired oxygen fraction during this part of the study. Oxygen consumption decreased significantly in one patient during ventilation by the portable ventilator although none of the other variables measured in this patient was altered. We conclude that ventilation of critically ill patients using the Pneupac Ventipac portable ventilator was safe, satisfactory and associated with minimal adverse effects on respiratory, haemodynamic and oxygen transport variables.     

新生儿呼吸机相关性肺炎病原菌特点及诊断探讨

目的 了解新生儿呼吸机相关性肺炎(VAP)的临床特点.方法 回顾性分析我院新生儿重症监护病房2004年1月至2006年10月机械通气≥48 h的102例患儿临床资料.结果 并发VAP 53例,占51.9%,诊断时间平均在机械通气后90.3(±22.5)h,临床表现以胸片浸润阴影(100%)、呼吸道内出现脓性分泌物(88.7%)、肺部湿罗音(77.4%)及PCO2＞45 mm Hg(64.2%)为主.发热28例(52.8%),白细胞增多12例(22.6%),51例痰培养阳性(96.2%),其中革兰阳性球菌占53.8%,革兰阴性杆菌占46.2%.肺炎克雷伯菌、溶血葡萄球菌、表皮葡萄球菌、金黄色葡萄球菌、大肠埃希菌、阴沟肠杆菌是6种主要致病菌,耐药率高.放弃治疗及死亡12例,占22.6%.结论 VAP病原复杂、易变,应严格掌握抗生素的适应症,避免过多使用抗生素,防止耐药菌株的出现.     

Negative pressure ventilation vs. spontaneous assisted ventilation during rigid bronchoscopy: A controlled randomised trial

Background: Ventilation during interventional rigid bronchoscopy (IRB) under general anaesthesia (jet ventilation, positive pressure ventilation and spontaneous assisted ventilation) may offer some difficulties. This study compares the effectiveness during IRB of intermittent negative pressure ventilation (INPV) and spontaneous assisted ventilation (SAV). Methods: Thirty-eight patients submitted to IRB were randomised into two groups: SAV or INPV. All patients received a total intravenous anaesthesia; INPV patients were paralysed. Pre-and intra-operative arterial blood gases and O₂ flow through a rigid bronchoscope were assessed. The endoscopist applying a subjective score evaluated the operating conditions. Results: Patients of the INPV group, as compared to the SAV group, required a lower dosage of fentanyl (2.6 ± 1.8 (μg · kg^?1· h^?1 vs. 6.6 ± 4.8 μg · kg^?1· h^?1), a lower O₂ supply (3.3 ± 2.8 1/min vs. 11.6 ± 3.4 1/min), a shorter recovery time (5.4 ± 2.9 min vs. 9.8 ± 7.1 min) and no manually assisted ventilation (0 ± 0 vs. 1 ± 1.1 nd?/procedure). Intraoperative PaCO₂ was higher in the SAV (8.1 ± 1.3 kPa) than in the INPV group (5.0 ± 1.6 kPa) and intraoperative pH differed in the two groups (7.26 ± 0.05, SAV vs. 7.47 ± 0.08, INPV). Operating conditions, as assessed by a subjective score, were considered better with INPV than with SAV (4.9 vs. 4.3). Conclusions: As compared to SAV, INPV in paralysed patients during IRB reduces administration of opioids, shortens recovery time, prevents respiratory acidosis, excludes the need for manually assisted ventilation, reduces 02 need and affords optimal surgical conditions. INPV appears a safe, non-invasive and effective ventilatory management during IRB.     

智能脱机模式对机械通气时间影响的系统评价

目的评价智能脱机模式对机械通气时间、脱机时间、重症监护(intensive care unit,ICU)时间、总住院时间、病死率和不良事件发生率的影响。方法计算机检索PubMed,EMBASE,CINAHL,CENTRAL,SinoMed和ISI Web of knowledge,手工检索初步入选文献的全文和参考文献中所列的相关文献,收集国内外关于智能脱机模式和人工脱机模式比较的随机对照和半随机对照研究。对纳入的文献进行治疗评价和定量分析。结果共13篇文献入选,合并分析显示智能化脱机模式能够缩短机械通气时间[MD=-63.98,95%CI(-108.67,-19.29)]和脱机时间[MD=0.84,95%CI(-1.31,2.99)],降低再插管[RR 0.75,95%CI(0.57,0.98)]和机械通气大于14 d患者比例[RR 0.66,95%CI(0.44,0.99)],但对ICU和总住院时间、病死率无显著性影响。结论     

乌司他丁对肝移植术后肺血管通透性的影响

目的 探讨乌司他丁对肝移植术后肺血管通透性的改善作用.方法 选取肝移植术后患者36例随机分为两组,常规组接受常规性治疗,乌司他丁组在常规治疗基础上应用乌司他丁(60万U,每日1次,静脉滴注).监测两组患者肺血管通透性:超声肺水B线评分、血管外肺水(EVLWI)、肺血管通透性指数(PVPI)、氧合指数(PO2/FiO2)、肺泡与肺动脉氧分压差[PO2(A-a)]及内皮素1(ET-1);脉搏指示性连续性心排量监测(PICCO)血流动力学参数;脱离呼吸机时间以及观察期间液体累计出入量等.结果 与常规组比较,乌司他丁组脱离呼吸机时间明显缩短、超声肺水B线评分、EVLWI、PVPI和PO2(A-a)下降;PO2/FiO2上升(P＜0.05).PICCO血流动力学参数比较差异无统计学意义(P＞0.05).结论 肝移植术后应用乌司他丁有利于改善肺脏血管通透性,缩短机械通气时间.     

When Scarcity Meets Disparity: “Resources Allocation and COVID-19 Patients with Diabetes”

The COVID-19 pandemic raised distinct challenges in the field of scarce resource allocation, a long-standing area of inquiry in the field of bioethics. Policymakers and states developed crisis guidelines for ventilator triage that incorporated such factors as immediate prognosis, long-term life expectancy, and current stage of life. Often these depend upon existing risk factors for severe illness, including diabetes. However, these algorithms generally failed to account for the underlying structural biases, including systematic racism and economic disparity, that rendered some patients more vulnerable to these conditions. This paper discusses this unique ethical challenge in resource allocation through the lens of care for patients with severe COVID-19 and diabetes.