Erythropoietin response is blunted in critically ill patients

Objectives: Critically ill patients often develop anaemia which can be related to a number of factors. However, the exact causes of anaemia in many patients remain unexplained. We hypothesized that the relationship between erythropoietin (EPO) and haematocrit may be altered in critically ill patients. Design: Serum concentrations of EPO were serially determined by the ELISA method in 36 critically ill, non-hypoxaemic patients who stayed more than 7 days in the Intensive Care Unit, including 22 patients with sepsis and 14 without. Eighteen ambulatory patients with iron-deficiency anaemia served as a control group. Setting: Two University Hospital Intensive Care Departments. Results: A significant inverse correlation between serum EPO and haematocrit levels was found in the control patients (r = −0.81, p < 0.001), but not in the critically ill patients (r = −0.09, NS), except in a subgroup of non-septic patients without renal failure (r = −0.61, p < 0.01). Conclusions: EPO levels can be inappropriately low in critically ill patients, so that EPO deficiency may contribute to the development of anaemia in these patients. This phenomenon is observed not only in the presence of acute renal failure, but also in the presence of sepsis. Received: 4 March 1996 Accepted: 7 November 1996     

A new device to remove obstruction from endotracheal tubes during mechanical ventilation in critically ill patients

Objective To evaluate the efficiency of a new device developed to remove obstructions from endotracheal tubes (ETT) in mechanically ventilated patients.Design Open study in mechanically ventilated sedated and paralyzed ICU patients.Setting General ICU and Laboratory of Respiratory Mechanics of the University of Rome La Sapienza.Patients 8 consecutive unselected mechanically ventilated, critically ill patients in which a partial obstruction of ETT was suspected on the basis of an increase of the peak inspiratory pressure (>20%) plus the difficult introduction of a standard suction catheter.Interventions Obstructions to ETT were removed with an experimental obstruction remover (OR)Measurements In vivo ETT airflow resistance (0.25; 0.5; 0.75; 1l/s) was evaluated before and after use of the OR; the work of breathing necessary to overcome ETT resistance (WOB_ett) was also evaluated before and after OR use.Results The use of OR significantly reduced in all patients the ETT in vivo resistance (From 5.5±2.3 to 2.9±0.5 cmH₂O/l/s at 0.25l/s,p<0.05; from 9±2.4 to 3.8±0.8 cmH₂O/l/s at 0.51l/s; from 12.2±3.5 to 5.7±1.2 cmH₂O/l/s at 0.75l/s; from 16.9±6 to 9.3±3.8 cmH₂O/l/s at 1l/s,p<0.01 respectively). Also the WOB_ett was significantly reduced after use of the OR (from 0.66±0.19 to 0.34±0.08 J/l;p<0.05)Conclusion This experimental device can be safely and successfully used to remove obstructions from the ETT lumen, without suspending mechanical ventilation, reducing the need for rapid ETT substitution in emergency and life-threatening situations.     

无创机械通气在重症肺炎合并急性呼吸衰竭中的应用

目的探讨无创机械通气（NIV）在救治重症肺炎合并急性呼吸衰竭中的价值。方法收集24例重症肺炎合并急性呼吸衰竭患者进行NIV的临床资料,回顾性分析NIV前后缺氧的改善情况、并发症及转归等。结果24例患者使用了机械通气,14例仅采用NIV,气体交换获得持久性改善,避免了气管插管,并最终存活出院。另10例先采用NIV,后改用有创机械通气。所有患者均能较好耐受。NIV使用1h后,PaO2和平均氧合指数较治疗前有明显提高（P〈0．05）。结论NIV可用于重症肺炎合并急性呼吸衰竭的早期呼吸支持治疗,能有效改善缺氧,耐受性和安全性好。     

Noninvasive continuous positive airway pressure delivered by helmet in hematological malignancy patients with hypoxemic acute respiratory failure

Objective To compare the efficacy of early administration of noninvasive continuous positive airway pressure (nCPAP) delivered by the helmet vs. face mask to treat hematological malignancy patients with fever, pulmonary infiltrates, and hypoxemic acute respiratory failure.Design and setting Prospective clinical study with historical matched controls in the hematology department of a university hospital.Patients and interventions Seventeen hematological malignancy patients with hypoxemic acute respiratory failure defined as: moderate to severe dyspnea, tachypnea (>30–35 breaths/min), use of accessory muscles and paradoxical abdominal motion, and PaO₂/FIO₂ ratio less than 200. Each patient was treated with nCPAP by helmet outside the ICU in the hematological ward. Arterial oxygen saturation, heart rate, respiratory rate, and blood pressure were monitored to identify early nCPAP failure. Seventeen historical-matched controls treated in the same department with face mask CPAP were selected as control population; matching criteria were age, sex, diagnosis, and PaO₂/FIO₂ ratio. Primary end-points were improvement in gas exchanges and the need for endotracheal intubation.Results Oxygenation improved in all patients after nCPAP. No patient failed helmet nCPAP because of intolerance while eigh patients in the mask group did so. nCPAP could be applied continuously for a longer period of time in the helmet group (28.44±0.20 vs. 7.5±0.45 h).Conclusions Early nCPAP with helmet improves oxygenation in selected immunosuppressed patients with hypoxemic acute respiratory failure. Tolerance of helmet nCPAP seems better than that of nCPAP delivered by mask.     

Noninvasive ventilation for the treatment of acute respiratory failure in patients with hematologic malignancies: a pilot study

Objective: To evaluate treatment with noninvasive ventilation (NIV) by nasal mask as an alternative to endotracheal intubation and conventional mechanical ventilation in patients with hematologic malignancies complicated by acute respiratory failure to decrease the risk of hemorrhagic complications and increase clinical tolerance. Design: Prospective clinical study. Setting: Hematologic and general intensive care unit (ICU), University of Rome “La Sapienza”. Patients: 16 consecutive patients with acute respiratory failure complicating hematologic malignancies. Interventions: NIV was delivered via nasal mask by means of a BiPAP ventilator (Respironics, USA); we evaluated the effects on blood gases, respiratory rate, and hemodynamics along with tolerance, complications, and outcome. Measurements and results: 15 of the 16 patients showed a significant improvement in blood gases and respiratory rate within the first 24 h of treatment. Arterial oxygen tension (PaO₂), PaO₂/FIO₂ (fractional inspired oxygen) ratio, and arterial oxygen saturation significantly improved after 1 h of treatment (43 ± 10 vs 88 ± 37 mmHg; 87 ± 22 vs 175 ± 64; 81 ± 9 vs 95 ± 4 %, respectively) and continued to improve in the following 24 h (p < 0.01). Five patients died in the ICU following complications independent of the respiratory failure, while 11 were discharged from the ICU in stable condition after a mean stay of 4.3 ± 2.4 days and were discharged in good condition from the hospital. Conclusions: NIV by nasal mask proved to be feasible and appropriate for the treatment of respiratory failure in hematologic patients who were at high risk of intubation – related complications. Received: 21 April 1998 Accepted: 18 September 1998     

血小板及骨髓象变化在危重病临床监测中的意义

目的　研究血小板及骨髓象变化在危重病临床监测中的意义。方法　ICU危重病患者 2 13例 ,入选标准为各种原因所致的SIRS和MODS。回顾性将病例分为死亡组 (n=6 2 ) 和存活组 (n=15 1)。入院后当天及 3、 7、 10d进行APACHEⅡ评分和血小板检查 ,入院后次日对各种体液进行细菌和真菌培养。35例患者在入ICU后 2 4小时内进行骨髓象检查。结果　入ICU时存活组和死亡组APACHEⅡ评分明显增高 ,但差异无显著意义 ;治疗 7d和 10d后 ,存活组下降至 10分以下 ,而死亡组上升至 2 0分以上 (P <0 0 1)。血小板在入院时两组均降低 ,但在治疗 7d和 10d死亡组患者血小板再度进行性下降 ,而存活组上升至正常范围 (P <0 0 0 1)。严重的阴沟杆菌感染、金黄色葡萄球菌感染 (MRA)和真菌性脓毒症 ,血小板低下的发生率分别为 72 3%、 89 6 %和 93 5 %。危重病患者骨髓象显示存活组带状核和分叶核粒细胞、浆细胞、巨核细胞明显高于死亡组 (P <0 0 5 ) ,而淋巴细胞死亡组显著高于存活组 (P <0 0 1)。结论　血小板进行性下降和骨髓抑制能较正确、敏感地反映危重病患者的病情和预后 ,而血小板检查快速、简单易行在临床上更有实用价值。     

应用无创通气作为急性呼吸衰竭患者撤机方法的研究

目的评价接受机械通气治疗的急性呼吸衰竭(ARF)患者应用无创通气(NIV)撤机的临床效果。方法58例ARF患者经气管插管机械通气治疗48h后病情好转,尚未完全满足撤机条件时随机分为两组,NIV组:拔管立即给予NIV作为撤机方法;有创压力支持通气(IPSV)组:继续经人工气道给予PSV实施撤机。观察比较两组患者动脉血气变化、并发症发生率、机械通气时间和住院时间、再插管率和病死率。结果NIV组有创通气时间显著短于IPSV组(P<0.05),两组总的通气支持时间相似。NIV组呼吸机相关性肺炎(VAP)的发生率显著低于IPSV组(P<0.05),住院时间显著短于IPSV组(P<0.05)。两组再插管率和病死率相似。结论NIV用于接受机械通气的ARF患者撤机可缩短有创通气时间和住院时间,降低VAP的发生率。     

The impact of the initial ventilatory strategy on survival in hematological patients with acute hypoxemic respiratory failure

Purpose

The aim of this study was to assess the impact of the 3 types of initial respiratory support (noninvasive positive pressure ventilation vs invasive positive pressure ventilation vs supplemental oxygen only) in hematological patients with acute hypoxemic respiratory failure (ARF).

Materials and Methods

This study is a retrospective analysis of a cohort of hematological patients admitted to the intensive care unit (ICU) of a tertiary care hospital between January 1, 2002, and June 30, 2006.

Results

One hundred thirty-seven hematological patients were admitted at the ICU with ARF (defined as Pao₂/Fio₂ <200): within the first 24 hours, 24 and 67 patients received noninvasive positive pressure ventilation and invasive positive pressure ventilation, respectively, and 46 received supplemental oxygen only. Intensive care unit mortality in the 3 patient categories was 71%, 63%, and 32%, respectively (P = .001), and in-hospital mortality was 75%, 80%, and 47%, respectively (P = .001). In multivariate regression analysis, increasing cancer-specific severity-of-illness score upon admission and more organ failure after 24 hours of ICU admission, but not the type of initial respiratory support, were significantly associated with ICU or in-hospital mortality.

Conclusions

Intensive care unit and in-hospital mortality in our population of hematological patients with hypoxemic ARF was determined by severity of illness and not by the type of initial respiratory support.     

Prevention of extubation failure in high-risk patients with neuromuscular disease

Background

A substantial proportion of patients with neuromuscular disease (NMD) who undergo positive pressure ventilation via endotracheal intubation for acute respiratory failure fail to pass spontaneous breathing trials and should be considered at high risk for extubation failure. In our study, we prospectively investigated the efficacy of early application of noninvasive ventilation (NIV) combined with assisted coughing as an intervention aimed at preventing extubation failure in patients with NMD.

Methods

This study is a prospective analysis of the short-term outcomes of 10 patients with NMD who were treated by NIV and assisted coughing immediately after extubation and comparison with the outcomes of a population of 10 historical control patients who received standard medical therapy (SMT) alone. The participants were composed of 10 patients with NMD who were submitted to NIV and assisted coughing after extubation (group A) and 10 historical control patients who were administered SMT (group B), who were admitted to a 4-bed respiratory intensive care unit (RICU) in a university hospital. Need for reintubation despite treatment was evaluated. Mortality during RICU stay, need for tracheostomy, and length of stay in the RICU were also compared.

Results

Significantly fewer patients who received the treatment protocol required reintubation and tracheostomy compared with those who received SMT (reintubation, 3 vs 10; tracheostomy, 3 vs 9; P = .002 and .01, respectively). Mortality did not differ significantly between the 2 groups. Patients in group A remained for a shorter time in the RICU compared with group B (7.8 ± 3.9 vs 23.8 ± 15.8 days; P = .006).

Conclusions

Preventive application of NIV combined with assisted coughing after extubation provides a clinically important advantage to patients with NMD by averting the need for reintubation or tracheostomy and shortening their stay in the RICU; its use should be included in the routine approach to patients with NMD at high risk for postextubation respiratory failure.     

无创正压通气与有创正压通气治疗急性呼吸衰竭的比较研究

目的　比较无创正压通气 (NPPV)和有创正压通气 (IPPV)救治急性呼吸衰竭 (ARF)的临床效果 ,评估NPPV在ARF治疗中的作用。方法　将各种原因所致ARF 5 2例患者随机分为NPPV组 (2 6例 )和IPPV组 (2 6例 ) ,在给予病因治疗同时分别实施NPPV和IPPV。观察分析两组患者在治疗过程中动脉血气变化、并发症的发生率及治疗结果。结果　NPPV组有 7例 (2 6 .9% )治疗失败转为气管插管IPPV ,其中 4例 (15 .4 % )死亡。IPPV组死亡 5例 (19.2 % ) ,两组死亡率无显著差异 (P >0 0 5 )。两组治疗有效患者在分别接受NPPV和IPPV治疗后 6h动脉血气有相似的显著改善。NPPV组患者机械通气时间和住院时间短于IPPV组 (P <0 .0 5 )。NPPV组的并发症发生率低于IPPV组 (P <0 .0 5 )。结论　在经过选择的ARF患者中 ,应用NPPV治疗的临床效果与IPPV相似。实施NPPV可缩短机械通气和住院时间 ,减少并发症。且因为无创伤性 ,NPPV可作为经过选择的ARF患者首选的通气支持治疗手段。     

Acute polyneuropathy in critically ill patients

We studied five patients in the intensive care unit (ICU) with acute polyneuropathy. All had previously presented severe infectious processes, accompanied by diverse organ failure accompanied by the Adult Respiratory Distress Syndrome (ARDS) in all cases. Two patients died and the three survivors suffered severe motor deficiencies. Electromyographic studies revealed axonal damage which predominately affected motor neurons. Cerebrospinal fluid was normal in all the patients except one, who showed a moderate increase of lymphocytes. The common causes of polyneuropathy were excluded, but in all cases a nutritional disorder was detected, based on laboratory values of proteins, serum albumin and transferrin. We conclude that polyneuropathy is relatively frequent among critically ill patients and must be closely monitored because of diagnostic difficulties and the repercussions on the progress of these patients. In spite of uncertainties about its cause, it appears to be related to severe infectious processes, ARDS, and nutritional disorders.     

Age differences in survival outcomes and resource use for chronically critically ill patients

Purpose

Chronically critically ill (CCI) patients use a disproportionate amount of resources, yet little research has examined outcomes for older CCI patients. The purpose of this study was to compare outcomes (mortality, disposition, posthospital resource use) between older (≥65 years) and middle-aged (45-64 years) patients who require more than 96 hours of mechanical ventilation while in the intensive care unit.

Methods

Data from 2 prospective studies were combined for the present examination. In-hospital as well as posthospital discharge data were obtained via chart abstraction and interviews.

Results

One thousand one hundred twenty-one subjects were enrolled; 62.4% (n = 700) were older. Older subjects had a 1.3 greater risk for overall mortality (from admission to 4 months posthospital discharge) than middle-aged subjects. The Acute Physiology Score (odds ratio [OR], 1.009), presence of diabetes (OR, 2.37), mechanical ventilation at discharge (OR, 3.17), and being older (OR, 2.20) were statistically significant predictors of death at 4 months postdischarge. Older subjects had significantly higher charges for home care services, although they spent less time at home (mean, 22.1 days) than middle-aged subjects (mean, 31.3 days) (P = .03).

Conclusion

Older subjects were at higher risk of overall mortality and used, on average, more postdischarge services per patient when compared with middle-aged subjects.     

Changing use of intensive care for hematological patients:

Objective: Intensivists generally view patients with hematological malignancies as poor candidates for intensive care. Nevertheless, hematologists have recently developed more aggressive treatment protocols capable of achieving prolonged complete remissions in many of these patients. This change mandates a reappraisal of indications for ICU admission in each type of hematological disease. Improved knowledge of the prognosis is of assistance in making treatment decisions. Patients and methods: The records of 75 myeloma patients consecutively admitted to our ICU between 1992 and 1998 were reviewed retrospectively and predictors of 30-day mortality were identified using stepwise logistic regression. Results: The median age was 56 years (37–84). Chronic health status (Knaus scale) was C or D in 39 cases. Fifty-five patients (73 %) had stage III disease and 17 had a complete or partial remission. Autologous bone marrow transplantation had been performed in 28 patients (37 %). ICU admission occurred between 1992 and 1995 in 41 patients (54.7 %), and between 1996 and 1998 in 34 patients (45.3 %). The median SAPS II and LOD scores were 60 (23–107) and 7 (0–21), respectively. Reasons for ICU admission were acute respiratory failure in 39 patients (52 %) and shock in 31 (41 %). Forty-six patients (61 %) required mechanical ventilation. Fifty patients (66 %) received vasopressors and 24 dialysis. Thirty-day mortality was 57 %. Only five parameters were independently associated with 30-day mortality in the multivariate model: female gender (OR = 5.12), mechanical ventilation (OR = 16.7) and use of vasopressor agents (OR = 5.67) were associated with a higher mortality rate, whereas disease remission (OR = 0.16) and ICU admission between 1996 and 1998 (OR = 0.09) were associated with a lower one. Conclusion: The prognosis for myeloma patients in the ICU is improving over time. This may reflect either recent therapeutic changes in hematological departments and ICUs or changes in patient selection for ICU admission. Hematologists and intensivists should work closely together to select hematological patients likely to benefit from ICU admission. Received: 11 June 1999 Accepted: 22 September 1999     

布托啡诺与丙泊酚对急性呼吸衰竭行无创机械通气躁动患者镇静作用的比较研究

目的比较布托啡诺与丙泊酚干预急性呼吸衰竭（ARF）行无创机械通气（NIV）躁动患者的镇静作用情况。 方法将118例ARF行NIV治疗的躁动患者分为布托啡诺组（57例）及丙泊酚组（61例）,两组患者分别予以输注布托啡诺和丙泊酚,维持镇静躁动评分（SAS）于3 ～ 4分,在治疗过程中根据需要给予咪达唑仑及芬太尼治疗。记录两组患者的一般资料,治疗前及治疗24 h后急性病生理学和长期健康评价（APACHE）Ⅱ评分、序贯器官衰竭估计（SOFA）评分、NIV不耐受评分、SAS评分、视觉模拟评分法（VAS）、呼吸频率、pH值、吸入氧浓度（FiO₂）、动脉血氧分压（PaO₂）、PaO₂ / FiO₂、动脉血二氧化碳分压（PaCO₂）,咪达唑仑和芬太尼使用情况及不良事件发生情况。 结果布托啡诺组和丙泊酚组患者治疗后NIV不耐受评分[（1.2 ± 0.5）分vs.（1.3 ± 0.7）分]、SAS评分[（3.5 ± 0.4）分vs.（3.6 ± 0.5）分]、VAS评分[（1.8 ± 0.3）分vs.（1.7 ± 0.3）分]、呼吸频率[（20.1 ± 6.4）次/ min vs.（21.3 ± 4.4）次/ min]、pH值[（7.41 ± 0.06）vs.（7.40 ± 0.06）]、FiO₂ [（0.40 ± 0.12）vs.（0.42 ± 0.11）]、PaO₂ [（97 ± 40）mmHg vs.（95 ± 40）mmHg]、PaO₂ / FiO₂ [（290 ± 48）mmHg vs.（282 ± 51）mmHg]及PaCO₂ [（34 ± 8）mmHg vs.（35 ± 7）mmHg]比较,差异均无统计学意义（t = 0.887、1.194、1.809、1.194、0.905、0.945、0.311、0.808、0.836,P = 0.377、0.235、0.072、0.235、0.367、0.347、0.756、0.421、0.405）。两组患者治疗后NIV不耐受评分、SAS评分、VAS评分、呼吸频率、FiO₂和PaCO₂水平较同组治疗前均显著降低,而pH值及PaO₂ / FiO₂较同组治疗前均显著升高（P均< 0.05）。布托啡诺组和丙泊酚组患者咪达唑仑使用情况（44 / 57 vs. 48 / 61）比较,差异无统计学意义（ χ² = 0.038,P = 0.845）;而芬太尼使用情况（4 / 57 vs. 49 / 61）及不良事件发生情况（9 / 57 vs. 26 / 61）比较,差异均有统计学意义（ χ² = 64.007、10.169,P < 0.001、= 0.001）。其中,两组患者的低血压（2 / 57 vs. 16 / 61）及低血容量（1 / 57 vs. 13 / 61）的发生情况比较,差异均有统计学意义（ χ² = 4.137、4.213,P = 0.042、0.040）。 结论与丙泊酚相比较,持续静脉输注布托啡诺可以减少ARF行NIV躁动患者芬太尼的需要量,并改善血流动力学状态。     

无创正压通气对急性呼吸衰竭患者拔管后再插管率和预后影响的荟萃分析

目的 探讨无创正压通气对急性呼吸衰竭患者拔管后再插管率和预后的影响.方法 通过计算机检索和手工检索中文期刊数据库,Pubmed,Embase,Web of Science数据库,收集1995年1月1日至2010年6月30日关于无创正压通气对急性呼吸衰竭患者拔管后进行呼吸支持和治疗的随机对照研究,按Cochrane协作网推荐的方法对拔管后采用无创正压通气进行呼吸辅助治疗患者的再插管率和病死率行Meta评价.结果 共纳入6篇随机对照研究,其中拔管后无创正压通气组(治疗组)患者381例,拔管后常规氧疗组(对照组)患者379例,治疗组和对照组患者的病死率分别为18.6%(62/334)vs.21.6%(72/333)(P=0.34),再插管率分别为30.2%(115/381)vs.33.5%(127/379)(P=0.27).与常规氧疗相比,拔管后无创正压通气不能降低患者再插管率,也不能改善患者预后.对拔管后即开始进行无创正压通气的患者进行分析,结果提示治疗组患者病死率明显降低[12.2%(22/181)vs.23.9%(44/184),P=0.004],再插管率减少;但与对照组相比,差异无统计学意义[14.0%(32/228)vs.20.4%(47/230),P=0.07].结论 急性呼吸衰竭患者拔管后早期行无创正压通气有助于减少患者再插管率,可显著改善患者预后.

Abstract：

Objective To evaluate the effects of noninvasive positive pressure ventilation (NPPV)used after extubation on mortality and rate of reintubation in patients with acute respiratory failure (ARF).Method Pubmed, Embase, Web of Science databases were searched to collect data from randomized controlled trials (RCT) of the relevant subject from January 1995 to May 2010. Meta analysis of data about NPPV on mortality and rate of reintubation in patients after extubation carried out by using the methods recommended by the Cochrane Collaboration. Results Six RCTs included sample size of 381 NPPV and 379routine medical care. In total, the mortalities of patients in NPPV group and routine medical care group were 18.6% (62/334) vs. 21.6% (72/333), respectively, and the rates of reintubation of the two groups were 30.2% (115/381) vs. 33.5% (127/379), respectively. Compared with routine medical care, NPPV did not significantly reduce the mortality ( OR: 0.83, 95% CI =0.57 ～ 1.21 ,P =0.34) and rate of reintuation( OR: 0.83, 95% CI = 0.59 ～ 1.16, ( P = 0.27). When the analysis was focused to the four studies of them in which patients received NPPV as soon as extubation, the results were quite different. From these four studies, the mortalities of patients in NPPV group and routine medical care group were 12. 2% (22/181) vs.23.9% (44/184),(P=0.004), and the rate of reintubation of the two groups were 14.0% (32/228) vs.20.4% (47/230), (P =0.07). Compared with routine medical care, early application of NPPV to patients after extubation reduced the mortality. Conclusions This study suggests the favorable effects of early application of NPPV to patients after extubation on the mortality of acute respiratory failure.     

Significance of pathologic oxygen supply dependency in critically ill patients: Comparison between measured and calculated methods

Objective Oxygen supply dependency at normal or high oxygen delivery rate has been increasingly proposed as a hallmark and a risk factor in critical illnesses. We hypothesized that as fas as an adequate oxygen delivery is provided, oxygen consumption, when determined by indirect calorimetry, is not dependent on oxygen delivery in critically ill patients whereas calculated oxygen consumption is associated with artefactual correlation of oxygen consumption and delivery. Design Oxygen delivery, oxygen consumption and their relationship were analyzed prospectively. Metabolic data gained from both measured and calculated methods were obtained simultaneously before and after volume loading. Setting The study was completed in the intensive care unit as part of the management protocol of the patients. Patients 32 consecutive patients entered the study and were divided into 3 groups according to a clinical condition known to favour oxygen supply dependency: sepsis syndrome, adult respiratory distress syndrome and acute primary liver failure. Intervention The rise in oxygen delivery was obtained by colloid infusion (oxygen flux test) performed in hemodynamically and metabolically stable patients. All were mechanically ventilated. No change in therapy was allowed during the test. Measurements and results Oxygen consumption was simultaneously evaluated by calculation (Fick Principle) and direct measurement using indirect calorimetry. Oxygen delivery was derived from the cardiac output (thermodilution) and arterial content of oxygen. Oxygen supply dependency was considered while observing an increase in oxygen delivery greater than 45 ml/min·m². Irrespective of patient's clinical diagnosis and outcome, measured oxygen uptake remained unaltered by volume infusion whereas both oxygen delivery and calculated oxygen consumption increased significantly. Arterial lactate level>2 mmol/l and measured oxygen extraction ratio>25% failed to identify oxygen supply dependency when measured data were considered. Conclusion Analysis of oxygen uptake, when measured by indirect calorimetry, failed to substantiate oxygen supply dependency in the vast majority of the critically ill patients irrespective of diagnosis and outcome. Mathematical coupling of shared variables accounted for the correlation between oxygen delivery and calculated oxygen consumption.     

Intrathoracic blood volume accurately reflects circulatory volume status in critically ill patients with mechanical ventilation

Positive pressure ventilation in patients with acute respiratory failure (ARF) may render the interpretation of central venous pressure (CVP) or pulmonary wedge pressure (PCWP) difficult as indicators of circulating volume. The preload component of cardiac (CI) and stroke index (SI) is also influenced by the increased intrathoracic pressures of positive pressure ventilation. Moreover CI and SI do not indicate volume status exclusively but also contractility and afterload. We investigated whether intrathoracic blood volume (ITBV) more accurately reflects blood volume status and the resulting oxygen transport (DO₂). CVP, PCWP, cardiac (CI) and stroke index (SI) were measured, oxygen transport index (DO₂I) and oxygen consumption index (VO₂I) were calculated in 21 ARF-patients. Ventilatory patterns were adjusted as necessary. CI, SI and intrathoracic blood volume index (ITBVI) were derived from thermal dye dilution curves which were detected with a 5 F fiberoptic thermistor femoral artery catheter and fed into a thermaldye-computer. All data were collected in intervals of 6h. There were 224 data sets obtained. Linear regression analysis was performed between absolute values as well as between the 6 h changes (prefix ). The following correlation coefficients were determined: CVP/CI and PCWP/CI 0.01 and –0.142 (p<0.05); CVP/SI and PCWP/SI –0.108 and –0.228 (p<0.01); ITBVI/CI and ITBV/SI 0.488 (p<0.01) and 0.480 (p<0.01); ITBVI and DO₂I 0.460 (p<0.01); CVP/CI and PCWP/CI –0.069 and–0.018; CVP/SI and PCWP/SI –0.083 and –0.009; ITBVI/CI and ITBVI/SI 0.715 (p<0.01) and 0.646 (p<0.01); ITBVI and DO₂I 0.707 (p<0.01). We conclude that in mechanically ventilated patients ITBV is a suitable indicator of circulating blood volume.     

无创通气在机械通气撤离中的作用

目的 探讨无创通气(Noninvasive positive pressure Ventilation,NNPV)在多种原因导致的急性呼吸衰竭机械通气患者撤机流程中的有效性.方法 前瞻性分析2007年1月至2008年12月浙江大学医学院附属邵逸犬医院ICU人选的71例急性呼吸衰竭机械通气患者.经气管插管机械通气治疗48 h后,达到临床撤机条件,但末能完成自主呼吸试验,排除NPPV禁忌证,将患者随机(随机数字法)分成无创通气序贯撤机(NPPV组,n=36)和传统撤机方法(IPPV组,n=35)两组.NPPV组拔管前予提高压力支持水平休息30 min,拔管后立即给予NPPV作为撤机方法;IPPV组传统方法撤机.观察两组患者自主呼吸试验前后呼吸力学参数、动脉血气、循环指标的变化,以及分组后两组机械通气2 h后的心肺参数,同时比较两组患者的转归.结果 分绀后机械通气2 h后心肺参数差异无统计学意义.与IPPV组相比,NPPV组机械通气时间、ICU住院时间、总住院时间明显缩短,分别为[(14.88 ±3.76)d vs.(20.68±2.79)d,P<0.01);(14.16±3.45)d vs.(2.57±7.71)d,P<0.01);IPPV组分别为(23.39±5.19)d vs.(33.89±8.58)d,P<0.01)],NPPV组并发症发生率明显低于IPPV组(22.9%vs.72.2%,P<0.01),特别是肺部感染发生率较低(6.1%vs.36.1%,P<0.01).结论 NPPV适用于多种原因导致的呼吸衰竭的撤机过程.把握无创通气NPPV的适应证,以及在撤机过程中及早进行NPPV干预,可以提高NPPV住序贯撤机中的成功率.