外科ICU机械通气患者医院内气管支气管炎发生率、病原学和危险因素分析

目的　探讨机械通气患者并发医院内气管支气管炎(NTB)的发生率、病原学及危险因素。方法　应用队列研究方法回顾性分析我院2002年1月—2004年4月在外科ICU内机械通气患者的临床资料。结果　96例外科ICU内机械通气患者有43例(44.8%)发生NTB,NTB组和非NTB组患者在血浆白蛋白、鼻饲情况、机械通气天数、抗生素应用种数以及ICU内住院时间差别均有统计学意义。鼻饲的比值比(OR)为4.5(95%CI为1.7~11.7),血浆白蛋白减低的OR值为2.6(95%CI1.2~6.0)。机械通气并发NTB患者第1位致病菌是鲍曼不动杆菌(39.5%),其次是金黄色葡萄球菌(32.6%)。在机械通气<5 d并发NTB患者常见致病菌是鲍曼不动杆菌和耐甲氧西林金黄色葡萄球菌(MRSA),机械通气≥5 d并发NTB患者常见致病微生物为铜绿假单胞菌和鲍曼不动杆菌。结论　ICU内机械通气患者NTB的发病率较高,血浆白蛋白减低、鼻饲、机械通气时间和ICU内住院时间延长是NTB的重要危险因素。NTB患者应合理使用抗生素,以减少细菌产生耐药。鲍曼不动杆菌、MRSA和铜绿假单胞菌是机械通气并发NTB常见致病菌。     

Pulmonary levels of high-mobility group box 1 during mechanical ventilation and ventilator-associated pneumonia

High-mobility group box (HMGB) 1 is a recently discovered proinflammatory mediator that contributes to acute lung injury. We determined HMGB-1 levels in bronchoalveolar lavage fluid of patients during mechanical ventilation (MV) and ventilator-associated pneumonia (VAP). Bronchoalveolar lavage fluid was obtained from patients who were ventilated for 5 h because of an elective surgical procedure ("short-term MV"; n = 40) or for several days because of respiratory failure without acute lung injury ("long-term MV"; n = 10) and from patients who developed unilateral VAP (n = 4). Ten healthy volunteers served as controls. In healthy volunteers, HMGB-1 levels were low (median, 1.6 ngmL(-1); interquartile range [IQR], 0.7-3.7 ng mL(-1)). Although HMGB-1 levels were elevated after short-term MV, differences were not statistically significant compared with healthy volunteers (1.7 ng mL(-1); IQR, 0.8-8.5 ng mL(-1), P = 0.493 vs. healthy volunteers; P = 0.250 vs. start of MV). However, HMGB-1 levels were significantly higher in "long-term" MV patients (11.7 ng mL(-1); IQR, 8.7-37.0 ng mL(-1); P < 0.0001 vs. healthy volunteers). With unilateral VAP, HMGB-1 levels from the infected lung.were 17.4 (IQR, 8.5-23.2) ng mL(-1) (P = 0.014 vs. healthy controls); these levels were not different from those measured in the contralateral noninfected lung (P = 0.625). Summarized, long-term MV is associated with increased HMGB-1 levels in contrast to "short-term" MV. In addition, HMGB-1 levels during VAP are increased compared with healthy volunteers; however, they are not different from those found in patients intubated and mechanically ventilated for a similar period of time.     

Incidence and regional distribution of lung overinflation during mechanical ventilation with positive end-expiratory pressure

OBJECTIVE: In patients with acute lung injury, alveolar recruitment resulting from positive end-expiratory pressure (PEEP) may be associated with overinflation of previously aerated lung regions. The aim of this study was to assess the incidence and regional distribution of lung overinflation resulting from mechanical ventilation with PEEP. DESIGN: Reanalysis with a specific software including a color-coding system of quantitative lung computed tomography data obtained in four previous prospective studies. SETTING: A 20-bed surgical intensive care unit of a Parisian university hospital. PATIENTS: Thirty-two patients with acute lung injury in whom computed tomography of the whole lung was obtained at zero end-expiratory pressure (ZEEP) and PEEP 15 cm H2O. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Total lung recruitment was measured as the reaeration of poorly aerated (computed tomography attenuations ranging between -500 and -100 Hounsfield units) and nonaerated (computed tomography attenuations > or = -100 Hounsfield units) lung areas, and overinflation was measured as the lung volume characterized by computed tomography attenuations < or = -900 Hounsfield units. PEEP was associated with a significant alveolar recruitment (423 +/- 178 mL). Concomitantly, a lung overinflation of 123 +/- 138 mL was found in 14 patients (44%). In eight patients without chronic obstructive pulmonary disease, lung overinflation was predominantly found in nondependent lung regions located beneath the dome of diaphragm. In six patients with a past history of chronic obstructive pulmonary disease, PEEP increased the volume of emphysematous areas present in apical lung regions and produced an overinflation of nondependent lung regions located beneath the dome of diaphragm. CONCLUSION: Lung overinflation resulting from mechanical ventilation with PEEP is observed in more than one third of patients with acute lung injury lying supine and predominates in caudal and nondependent lung regions. Furthermore, in patients with a history of chronic obstructive pulmonary disease, PEEP markedly increases the volume of emphysematous lung regions.     

Incidence and risk factors of pneumonia acquired in intensive care units

Objective To estimate the incidence of pneumonia acquired in the intensive care unit (ICU), and to define risk factors for developing such an event.Design European prospective survey, in which all patients admitted to the participating ICU from January, 17 to 23, 1990, were followed until ICU discharge.Setting 107 general ICUs from 18 countries.Patients Of 1078 admitted to the ICUs, 996 patients without pneumonia at admission were studied.Measurements Pneumonia was diagnosed by the staff physician on the basis of clinical, radiological and microbiological criteria, secondly validated by an expert committee who reviewed all the forms and even recontacted ICU physicians. Crude incidence and time to occurrence of pneumonia were estimated, then both used as endpoints for prognosis analysis.Results 89 pneumoniae were observed: crude incidence was estimated at 8.9%, 7-day and 14-day pneumonia rates at 15.8% and 23.4%, respectively. The risk of developing pneumonia increased when either coma, trauma, respiratory support, Apache II >16 and/or impaired airway reflexes were present at ICU admission. To predict time to occurrence of pneumonia, only two variables remained significant: the presence of impaired airway reflexes at admission and the use of mechanical ventilation during ICU course.Conclusion The role of the injury to the respiratory system — with the subsequent need for respiratory support-appears central in determining the risk to acquire pneumonia in ICU. In the future, the predictive value of severity scores during ICU course should be otherwise assessed.     

Heliox during mechanical ventilation

The indications for heliox during mechanical ventilation are lower-airway obstruction, especially with hypercarbia; need to enhance aerosol delivery to lung periphery; and need to facilitate weaning from mechanical ventilation. Certain ventilators perform relatively well with heliox and are not substantially affected by it. It is preferable to connect the heliox to the air inlet of the ventilator, because this results in more consistent delivery of oxygen and tidal volume. When administering heliox, pay close attention and directly monitor the actual tidal volume and fraction of inspired oxygen.     

Prognosis factors and outcome of community-acquired pneumonia needing mechanical ventilation

PURPOSE: To evaluate the variables associated with mortality of patients with community-acquired pneumonia who require mechanical ventilation and to determine the attributable morbidity and intensive care unit (ICU) mortality of community-acquired pneumonia. MATERIAL AND METHODS: Retrospective cohort study carried out in 361 ICUs from 20 countries including 124 patients who required mechanical ventilation on the first day of admission to the hospital due to acute respiratory failure secondary to severe community-acquired pneumonia. To assess the factors associated with outcome, a forward stepwise logistic regression analysis was performed, and to determine the attributable mortality of community-acquired pneumonia, a matched study design was used. RESULTS: We found 3 independent variables significantly associated with death in patients with community-acquired pneumonia requiring mechanical ventilation: simplified acute physiological score greater than 45 (odds ratio, 5.5 [95% confidence interval, 1.7-12.3]), shock (odds ratio, 5.7 [95% confidence interval, 1.7-10.1]), and acute renal failure (odds ratio, 3.0 [95% confidence interval, 1.1-4.0]). There was no statistically significant difference in ICU mortality among patients with or without community-acquired pneumonia (32% vs 35%; P=.59). CONCLUSIONS: Community-acquired pneumonia needing mechanical ventilation is not a disease associated with higher mortality. The main determinants of patient outcome were initial severity of illness and the development of shock and/or acute renal failure.     

Sedation and paralysis during mechanical ventilation

Treatment of anxiety and delirium, provision of adequate analgesia, and, when necessary, amnesia in critically ill patients is humane and may reduce the incidence of post-traumatic stress disorders. Injudicious use of sedatives and paralytics to produce a passive and motionless patient, however, may prolong weaning and length of stay in the intensive care unit. This report reviews indications and choices for pharmacologic treatment of anxiety, delirium, agitation, and provision of anesthesia in critically ill patients. The choice of pharmacologic agents is made difficult by complex or poorly understood pharmacokinetics, drug actions, and adverse effects in critically ill patients. Advantages, adverse effects, and limitations of drug treatment, including use of neuromuscular blocking drugs and use of sedatives and analgesia during the withdrawal of life-sustaining measures are reviewed.     

Transbronchial biopsy during mechanical ventilation

The diagnostic yield and risks of transbronchial biopsy (TBB) during mechanical ventilation were assessed in 13 patients with progressive pulmonary infiltrates. TBB was of considerable diagnostic value in ten patients and useful in excluding potentially treatable infections in the remaining three patients. Complications included two pneumothoraces, pulmonary hemorrhage in one case, and supraventricular tachycardia in another. No fatalities were attributable to TBB. TBB proved to be a relatively safe procedure, with a high diagnostic yield in these critically ill patients.     

Respiratory monitoring during mechanical ventilation

Continuous monitoring of important respiratory indices has the potential for predicting catastrophes and for providing an opportunity for the timely institution of lifesaving measures. Pulmonary gas exchange can be assessed by indices derived from arterial blood gas measurements, but these are limited by their invasive and intermittent nature. Intra-arterial electrodes that provide a continuous recording of blood gases are under development and appear very promising. Specially designed pulmonary artery catheters permit continuous recording of mixed venous O2 saturation, whereas continuous, non-invasive recordings of arterial oxygenation can be obtained with pulse oximetry and transcutaneous electrodes. A satisfactory method of monitoring CO2 tension does not exist. Measurements of respiratory drive can be obtained at the bedside, but their clinical usefulness remains unknown. Assessment of respiratory muscle strength is helpful in determining the need for mechanical ventilation, but a practical method of diagnosing respiratory muscle fatigue remains elusive. Recordings of the airway pressure waveform, calculation of thoracic compliance, and detailed examination of the pattern of breathing are helpful in assessing pulmonary mechanics. Although respiratory monitoring provides much useful information, it does not substitute for careful bedside examination.     

两种湿化液在小儿肺炎机械通气吸痰中的效果比较

目的探讨两种湿化液对肺炎机械通气患儿吸痰的效果。方法 选择建立人工气道行机械通气的ICU肺炎患儿60例,随机分为研究组和对照组各30例。研究组吸痰前采用0.45%盐水气管内滴入,对照组采用生理盐水气管内滴入,观察两组吸痰前后血气分析结果。结果两组吸痰前血气分析结果,差异无统计学意义(P>0.05),吸痰后研究组血气分析结果优于对照组,差异有统计学意义(P<0.01)。结论对机械通气痰液黏稠的患儿吸痰时,0.45%盐水的湿化效果优于生理盐水。     

江油地区儿童社区获得性肺炎病原学分析

目的了解江油地区社区获得性肺炎病原体分布情况,为经验治疗提供依据。方法对1 995例大于或等于2岁的社区获得性肺炎患儿留取呼吸道分泌物进行细菌培养,同时采用聚合酶链反应检测非典型病原体。结果 1 995例患儿病原学检测阳性426例(21.35%),其中常见细菌阳性324例(16.24%),病原菌中以肺炎链球菌为主,其次为阴沟肠杆菌、肺炎克雷伯菌及肺炎克雷伯菌。非典型病原体102例(5.11%),包括肺炎支原体、细菌合并肺炎支原体感染及肺炎衣原体等。结论肺炎链球菌是江油地区社区获得性肺炎的主要致病菌。     

Carbon dioxide production during mechanical ventilation

Because of large stores of CO2 in different body tissues, metabolic change cannot be detected by measuring gas exchange until the CO2 stores have adapted to the new situation. Similarly, changes in the CO2 stores not due to metabolic alterations, may lead to error in gas exchange measurements. We studied CO2 production (VCO2) and oxygen consumption (VO2) in mechanically ventilated ICU patients, where CO2 stores were altered by: a) changing minute ventilation by 15%, b) reducing body temperature, and c) changing the level of sedation. Expired gases went through a mixing chamber and were analyzed continuously by a mass spectrometer. Signals from this instrument, together with gas-volume signals from the ventilator, were fed to a computer for calculation of VO2 and VCO2. Twenty to 120 min were required to reach a stable level, depending on the patient's size and circulatory response. Similar results were obtained by computer simulation using a five-compartment model of CO2 stores. These experiments indicate that measuring VO2 (for calculation of metabolic respiratory quotient [RQ]) in ventilated patients should occur after the patients maintain a 60-min period of stable body temperature and awareness. Ventilatory variables should not be changed substantially during the 90-min period before gas sampling. Cardiac output and muscle blood flow should not have changed 2 to 3 h before measuring RQ. If muscle blood flow is low, the stable periods for body temperature and ventilatory variables should be increased.     

Inhaled bronchodilator administration during mechanical ventilation

Inhaled bronchodilators are routinely administered to mechanically ventilated patients to relieve dyspnea and reverse bronchoconstriction. A lower percentage of the nominal dose reaches the lower respiratory tract in a mechanically ventilated patient than in a nonintubated subject, but attention to device selection, administration technique, dosing, and patient-ventilator interface can increase lower-respiratory-tract deposition in a mechanically ventilated patient. Assessing the airway response to bronchodilator by measuring airway resistance and intrinsic positive end-expiratory pressure helps guide dosing and timing of drug delivery. Selecting the optimal aerosol-generating device for a mechanically ventilated patient requires consideration of the ease, reliability, efficacy, safety, and cost of administration. With careful attention to administration technique, bronchodilator via metered-dose inhaler or nebulizer can be safe and effective with mechanically ventilated patients.     

Patient-ventilator asynchrony during assisted mechanical ventilation

Objective The incidence, pathophysiology, and consequences of patient-ventilator asynchrony are poorly known. We assessed the incidence of patient-ventilator asynchrony during assisted mechanical ventilation and we identified associated factors.Methods Sixty-two consecutive patients requiring mechanical ventilation for more than 24 h were included prospectively as soon as they triggered all ventilator breaths: assist-control ventilation (ACV) in 11 and pressure-support ventilation (PSV) in 51.Measurements Gross asynchrony detected visually on 30-min recordings of flow and airway pressure was quantified using an asynchrony index.Results Fifteen patients (24%) had an asynchrony index greater than 10% of respiratory efforts. Ineffective triggering and double-triggering were the two main asynchrony patterns. Asynchrony existed during both ACV and PSV, with a median number of episodes per patient of 72 (range 13–215) vs. 16 (4–47) in 30 min, respectively (p = 0.04). Double-triggering was more common during ACV than during PSV, but no difference was found for ineffective triggering. Ineffective triggering was associated with a less sensitive inspiratory trigger, higher level of pressure support (15 cmH₂O, IQR 12–16, vs. 17.5, IQR 16–20), higher tidal volume, and higher pH. A high incidence of asynchrony was also associated with a longer duration of mechanical ventilation (7.5 days, IQR 3–20, vs. 25.5, IQR 9.5–42.5).Conclusions One-fourth of patients exhibit a high incidence of asynchrony during assisted ventilation. Such a high incidence is associated with a prolonged duration of mechanical ventilation. Patients with frequent ineffective triggering may receive excessive levels of ventilatory support.B.C. is supported by the Instituto de Salud Carlos III (expedient CM04/00096, Ministerio de Sanidad) and the Instituto de Recerca Hospital de la Santa Creu i Sant Pau