Pulmonary complications of mechanical ventilation.

Although life-saving, mechanical ventilation may be associated with many complications, including consequences of positive intrathoracic pressure, the many aspects of volutrauma, and adverse effects of intubation and tracheostomy. Optimal ventilatory care requires implementing mechanical ventilation with attention to minimizing adverse hemodynamic effects, averting volutrauma, and effecting freedom from mechanical ventilation as quickly as possible so as to minimize the risk of airway complications.     

吸气峰压、平台压对机械通气下呼吸窘迫鉴别的意义

目的探讨机械通气下峰压和平台压对呼吸窘迫鉴别诊断的意义。方法对60例机械通气下出现呼吸窘迫的患者进行分析,记录吸气峰压（PAP）和平台压（Pplateau）参数的变化情况,同时记录吸气峰压升高组系统静态顺应性（Cst）、气道阻力（Raw）的变化,并对病因进行分析。结果呼吸窘迫时,吸气峰压可出现增加,减少,和不变,峰压增加包括平台压增加（包括肺水肿、肺不张、气胸等）和不变（气道痉挛、分泌物增多和误吸等）,吸气峰压的增加主要见于Raw增加（平台压不变）和Cst的下降（平台压增加）,吸气峰压的减少见于通气环路漏气和过度通气,而吸气峰压不变见于肺栓塞和贫血。结论吸气峰压和平台压的变化,对机械通气下的呼吸窘迫的病因有一定的鉴别诊断意义。     

Acute exacerbations and respiratory failure in chronic obstructive pulmonary disease

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) describe the phenomenon of sudden worsening in airway function and respiratory symptoms in patients with COPD. These exacerbations can range from self-limited diseases to episodes of florid respiratory failure requiring mechanical ventilation. The average patient with COPD experiences two such episodes annually, and they account for significant consumption of health care resources. Although bacterial infections are the most common causes of AECOPD, viral infections and environmental stresses are also implicated. AECOPD episodes can be triggered or complicated by other comorbidities, such as heart disease, other lung diseases (e.g., pulmonary emboli, aspiration, pneumothorax), or systemic processes. Pharmacologic management includes bronchodilators, corticosteroids, and antibiotics in most patients. Oxygen, physical therapy, mucolytics, and airway clearance devices may be useful in selected patients. In hypercapneic respiratory failure, noninvasive positive pressure ventilation may allow time for other therapies to work and thus avoid endotracheal intubation. If the patient requires invasive mechanical ventilation, the focus should be on avoiding ventilator-induced lung injury and minimizing intrinsic positive end-expiratory pressure. These may require limiting ventilation and "permissive hypercapnia." Although mild episodes of AECOPD are generally reversible, more severe forms of respiratory failure are associated with a substantial mortality and a prolonged period of disability in survivors.     

机械通气中人机对抗的防治对策

目的:探讨机械通气患者发生人机对抗的原因和防治对策。方法:对57例人机对抗患者进行回顾性分析。结果:104例机械通气患者中发生人机对抗57例(54.8%),其中死亡3例(5.3%)。其原因包括:气道阻塞30例,支气管痉挛6例,潮气量不足6例,持续高热5例,急性肺水肿4例,单肺通气3例,呼吸机漏气2例,气胸1例。结论:人机对抗的发生均有其诱发因素。气道阻塞、潮气量不足、急性肺水肿等是主要原因。加强气道管理、设置合适的通气量、解除气道痉挛、祛除诱因等综合有效防治措施,可避免和减少人机对抗的发生。     

双相气道正压通气治疗急性肺损伤的临床观察

目的探讨双相气道正压（BIPAP）通气模式对急性肺损伤（acute lung injury，ALI）患者的治疗作用。方法将20例接受机械通气治疗的Au患者随机分为容量控制通气组（VCV组）和双相气道正压通气组（BIPAP组），每组各10例。观察两组血气分析、呼吸力学指标。结果通气后BIPAP组的氧分压（PaO2）、动脉血氧饱和度（SaO2）、氧合指数（OI）均显著高于VCV组（P〈0.05）；通气结束时，VCV组镇静剂用量和气管插管通气时间均显著高于BIPAP组（P〈0．05）。结论BIPAP通气模式人机协调性好，缩短了治疗时间。     

Elevated Tissue Kallikrein Activity in Airway Secretions from Patients with Tracheobronchitis Associated with Prolonged Mechanical Ventilation

The clinical course of patients undergoing prolonged mechanical ventilation is often complicated by the development of purulent tracheobronchitis. The purpose of this study was to assess whether ventilator-associated hypersecretion is associated with elevated levels of tissue kallikrein (TK) activity. TK can induce marked bronchial inflammation in animal models and TK activity is increased in the airway secretions of symptomatic asthmatics. It has not been studied in conditions with predominantly neutrophilic bronchial secretions, although animal data indicate that neutrophil elastase may stimulate TK activity. We measured TK activity in airway secretions of patients undergoing mechanical ventilation for more than 4 weeks (PMV group) and in two comparator groups: patients with cystic fibrosis, who were colonized with Pseudomonas aeruginosa (CF group) and patients undergoing mechanical ventilation for less than one week who did not have clinical evidence of purulent airway secretions (acute mechanical ventilation, AMV group). We also compared the level of neutrophil elastase (NE) activity, an index of neutrophil activation, in the three patient groups. TK and NE activity in the sol phase were measured by the degradation of chromogenic substrates (DL Val-Leu-Arg pNA and N-Methoxy Succinyl Ala-Ala-Pro-Val pNA, respectively). Intergroup differences in cell counts were not significant. However, TK activity was significantly less in the AMV group than in the PMV and cystic fibrosis patients (Kruskal-Wallis ANOVA, p < 0.05). Elastase activity was significantly greater in the CF group (p < 0.05) than in the other two groups. Compared to patients undergoing short-term mechanical ventilation (AMV group), TK activity was elevated in patients with purulent tracheobronchitis associated with prolonged mechanical ventilation (PMV group). The elevation in TK activity in these patients is comparable to levels in sputum from patients with cystic fibrosis (CF group), although the latter had a significantly higher level of NE activity. The observation of increased TK activity in patients with neutrophilic airway inflammation suggests that TK may play a role in modulating inflammation in ventilator-associated tracheobronchitis and may be worthy of further study to determine its source and significance.     

床旁电子支气管镜在358例接受机械通气的肝衰竭患者中的应用研究

目的探讨电子支气管镜在接受机械通气的肝衰竭患者中的临床应用价值。方法对358例在ICU接受机械通气的肝衰竭患者进行了床旁电子支气管镜检查,人工气道位置判断,并进行肺泡灌洗、吸痰、气道异物吸出、病原学检查以及可能的气管导管位置调整,最后对其应用价值进行分析。结果 358例患者中,304例合并肺炎经电子支气管镜吸痰及支气管肺泡灌洗等治疗后,明确病原学证据247例(81.25%),比较24 h胸片,明显改善者106例(34.87%);54例(17.76%)通气障碍患者经电子支气管镜检查明确原因,其中27例为人工气道梗阻、痰痂或血痂形成,经电子支气管镜反复吸取,成功解除气道梗阻;21例为气管插管或套管易位、顶端贴气管壁,在电子支气管镜协助下调整或更换套管;6例肝衰竭存在肺不张患者经电子支气管镜吸痰治疗后全部复张。结论针对机械通气的肝衰竭患者,电子支气管镜在直视下吸痰、调整导管位置或留取标本,可有效减少气道出血等并发症的发生,从而安全、有效清除气道内分泌物,及早获得病原学结果,及时指导临床抗生素的应用。     

The management of life-threatening airflow obstruction

Summary Patients with status asthmaticus commonly develop progressive airflow obstruction over hours to days as a result of airway wall inflammation, bronchospasm and intraluminal mucus. In sudden asphyxic asthma, airflow obstruction results primarily from smooth muscle mediated bronchospasm. Airflow obstruction causes ventilation-perfusion inequality, lung hyperinflation, and increased work of breathing. Severe cases are characterized by an inability to speak, diaphoresis, altered mental status, poor air movement, widened pulsus paradoxus, accessory muscle use, and low peak expiratory flow rate. Lack of early response to bronchodilator therapy, a rising partial pressure of carbon dioxide, and need for assisted ventilation are additional markers of severe disease. First line treatment consists of oxygen, beta agonists, and corticosteroids. In mechanically ventilated patients, bronchodilators must be given in higher dosages to achieve a physiologic effect. Agents of debated efficacy include theophylline, anticholinergics, and magnesium sulfate. Heliox and noninvasive positive pressure ventilation are promising adjuncts to the treatment of nonintubated patients. In patients requiring intubation and mechanical ventilation, a ventilatory strategy should be used that avoids excessive lung hyperinflation by prolonging expiratory time. In many cases, this strategy requires acceptance of hypercapnea and high peak airway pressures. Patients should be aggressively sedated to decrease the need for muscle paralysis and the risk of post paralytic myopathy. Indirect evidence suggests that the current approach to mechanical ventilation in acute severe asthma decreases morbidity and mortality; however, the key to the management of this disease (which in many cases represents a failure of outpatient management) is patient education and disease prevention. Received: 25 October 1996 Accepted: 13 November 1996     

支气管肺泡灌洗在慢性阻塞性肺疾病机械通气患者中的应用

目的 探讨支气管肺泡灌洗治疗慢性阻塞性肺疾病机械通气患者的临床价值.方法 将我院收治的94例慢性阻塞性肺疾病机械通气患者随机分为治疗组(48例)和对照组(46例).对治疗组患者进行支气管肺泡灌洗,观察灌洗后临床疗效、血气分析和呼吸力学指标变化.结果 治疗组患者灌洗后临床症状改善,PaO2上升,PaCO2下降,气道平均压...     

How best to deliver aerosol medications to mechanically ventilated patients

Pressurized metered-dose inhalers (pMDIs) and nebulizers are employed routinely for aerosol delivery to ventilator-supported patients, but the ventilator circuit and artificial airway previously were thought to be major barriers to effective delivery of aerosols to patients receiving mechanical ventilation. In the past two decades, several investigators have shown that careful attention to many factors, such as the position of the patient, the type of aerosol generator and its configuration in the ventilator circuit, aerosol particle size, artificial airway, conditions in the ventilator circuit, and ventilatory parameters, is necessary to optimize aerosol delivery during mechanical ventilation. The best techniques for aerosol delivery during noninvasive positive-pressure ventilation are not well established as yet, and the efficiency of aerosol delivery in this setting is lower than that during invasive mechanical ventilation. The most efficient methods of using the newer hydrofluoroalkane-pMDIs and vibrating mesh nebulizers in ventilator-supported patients also require further evaluation. When optimal techniques of administration are employed, the efficiency of aerosolized drug delivery in mechanically ventilated patients is comparable to that achieved in ambulatory patients.     

经喉罩或气管插管连接行常规机械通气在全身麻醉介入治疗手术中的安全性

目的 探索并评价使用喉罩或气管插管联合常规机械通气在介入治疗手术中的应用价值.方法 纳入2009年7月至2010年1月收入首都医科大学附属北京天坛医院呼吸科在全身麻醉下经喉罩或气管插管联合常规机械通气条件下接受气管镜介入治疗的患者29例,其中男19例,女10例,年龄19 ～74岁,平均(47±18)岁.观察手术前后的气道压、潮气量、术中血气分析、并发症及手术时间等指标,并对影响通气效果的相关因素进行分析.结果 所有患者术中一般情况稳定,通气效果满意,无严重并发症出现.气管镜插入喉罩或气管插管后,潮气量下降27.1％,峰压升高63.1％,平台压及平均压分别升高43.7％和32.4％;使用气管插管的患者操作前后峰压升高79.3％,高于使用喉罩的患者峰压升高程度(55.3％).结论 全身麻醉下使用喉罩或气管插管联合常规机械通气条件下进行气管镜介入治疗安全可靠.操作过程中峰压明显增高,但整个气道的平均压力仍能保持较低水平;在使用喉罩或气管插管进行气管镜介入治疗时,应尽可能选用较大内径的喉罩或插管,以最大限度地降低气道压并避免内源性呼气末正压的产生.     

重度气道狭窄置放国产镍钛记忆合金支架的方法学研究

目的 对重度气道狭窄患者置放国产镍钛记忆合金支架的方法学进行初步评价.方法 应用全身麻醉下分别采用经喉罩、气管插管或硬质气管镜的方法对2005年11月至2009年4月收入北京大坛医院呼吸科的40例难以在局部麻醉下操作的重症气道狭窄患者置入国产镍钛记忆合金气道支架.结果 40例患者根据病变部位及病变特点选择经喉罩23例,气管插管11例,硬质气管镜6例,并予全身麻醉及机械通气,共放置了42枚支架:气管支架27枚(其中覆膜支架9枚)、左主支气管支架8枚、右主支气管至右中间段支架2枚、气管至左主支气管楔形支架5枚.在全身麻醉、机械通气维持患者各项生命体征的条件下,所有病例都顺利置入,未出现并发症.支架释放后所有病例气道压力即降至正常,同时其他机械通气参数也恢复正常.大部分患者呼吸困难指数分级由Ⅳ～V级改善到0～Ⅱ级.结论 对于重度气道狭窄患者,在全身麻醉下经喉罩、气管插管及硬质气管镜的方法可以顺利放置局部麻醉下难以操作的各种高难度气道支架的置放,并且安全、有效、舒适,值得在临床进一步推广.     

Positive airway pressure in patients receiving intermittent mandatory ventilation at zero rate. The role in weaning in chronic obstructive pulmonary disease

Over a 20-month period, we treated 180 mechanically ventilated patients in our respiratory intensive care unit. Among these patients, we observed an interesting previously unreported phenomenon in 20 patients with severe chronic obstructive disease. During the weaning from mechanical ventilators of these 20 patients, there was a marked clinical deterioration when the mode of ventilation was changed from intermittent mandatory ventilation (IMV) at zero rate to that of a T-tube setup. To explain this previously unreported observation, we studied and compared nine different intubated patients for possible differences in airway pressure between IMV set up at zero rate and a T tube. We observed that peak airway pressures were greater on IMV at zero rate compared to the peak airway pressures on the T piece in all nine patients. At the end of expiration, seven out of the nine patients had higher airway pressures on IMV at zero rate compared to the T tube. These differences in the peak airway pressures and end-expiratory pressures were statistically significant in both groups. In spite of the obvious limitation of extrapolating the experimental results obtained in one group of patients to explain the clinical observations made in another group of patients, we believe that the higher airway pressures on the IMV system (even without any mechanical ventilation) prevent early collapse of the airways, and this may be of significant importance in successfully weaning patients with COPD.     

机械通气中气道压力增高的原因与防治

目的探讨机械通气患者气道压力增高的原因与防治对策。方法对本科2000年1月～2005年8月收治的112例机械通气病例进行回顾性分析。结果发生气道压力增高49例。其原因包括:气道阻塞31例,支气管痉挛7例,肺水肿5例,单肺通气3例,导管受压2例,气胸1例。结论气道阻塞、支气管痉挛、肺水肿为气道压力增高的主要原因。综合防治措施,可防止气道压力增高的发生,提高救治存活率。     

有创无创呼吸机在呼吸衰竭气管切开患者的临床观察

目的探讨双水平正压通气在呼吸衰竭气管切开患者序贯治疗中应用的价值。方法选择10例呼吸衰竭气管切开机械通气患者,肺部感染基本控制,均有自主呼吸,病情稳定,呼吸机通气模式为压力支持、但撤机困难。应用双水平正压通气无创呼吸机,连接气管切开导管,呼吸支持治疗,观察患者呼吸次数、心率、血压、血气分析指标的变化及预后。结果双水平正压通气无创呼吸机可应用于呼吸衰竭气管切开患者的呼吸支持治疗,患者呼吸次数、心率、血压稳定,PH、PaO2、PaCO2基本维持正常。观察、随访24周,10例患者中7例停用BiPAP,拔除气管导管,封闭气管切开开口。1例BiPAP通气24周,病情稳定。2例因再次感染死亡。结论双水平正压通气可应用于病情稳定,但撤机困难的气管切开呼吸衰竭患者序贯治疗。     

无创面罩正压通气治疗急性重度左心衰竭

目的探讨双水平式呼吸道正压无创呼吸机面罩正压通气配合抗心力衰竭药治疗急性重度左心力衰竭的临床意义。方法急性重度左心衰竭45例，在常规药物治疗的基础上，随机分成两组，分别应用双水平式呼吸道正压无创呼吸机和有创呼吸机治疗，比较治疗前后血压、心率、动脉血气变化、临床症状和转归。结果双水平式呼吸道正压无创呼吸机组较有创呼吸机组的临床症状、出院转归及相关指标差异无统计学意义（P〉0．05）。结论及早使用双水平式呼吸道正压通气结合抗心力衰竭药治疗急性重度左心衰竭对心功能改善有明显疗效。能及时有效地改善病人症状及低氧血症，缩短急性左心衰竭病程，促进康复．减少并发症。     

气道压力释放通气应用于急性肺损伤/急性呼吸窘迫综合征患者的研究

目的评价气道压力释放通气(airway pressure release ventilation,APRV)对急性肺损伤(acute lung injury,ALI)/急性呼吸窘迫综合征(acute respiratory distress syndrome,ARDS)患者的疗效,评估其对患者呼吸机相关性肺损伤(Ventilator-Induced Lung Injury,VILI)程度,并探讨可能的机制。方法采用前瞻性研究方法,入组患者随机分为APRV组、小潮气量肺保护通气组。描记肺准静态压力-容积曲线(pressure-volume curve,P-V曲线),并据此设置呼吸机参数,通气24h、48h观察效果。结果两组患者氧合明显改善,血流动力学指标无明显变化,APRV组Pmean明显高于SIMV+PEEP组,准静态P-V曲线三角区Pflex容积(Vdelta)增加明显,血清SP-D浓度呈升高趋势。结论 APRV应用于急性肺损伤/急性呼吸窘迫综合征患者,相对于小潮气量肺保护性通气策略,氧合改善、呼吸力学类似;较高的平均气道压,能更有效地肺复张,未对血流动力学产生影响,但加重了肺损伤,导致呼吸机相关性肺损伤。     

Role of airway mechanoreceptors in the inhibition of inspiration during mechanical ventilation in humans

The purpose of this study was to demonstrate a neuromechanical inhibitory effect on respiratory muscle activity during mechanical ventilation and to determine whether upper and lower airway receptors provide this inhibitory feedback. Several protocols were completed during mechanical ventilation: (1) positive and negative pressure changes in the upper airway, (2) airway anesthesia to examine the consequences of receptor blockade on respiratory muscle activity, (3) increasing FRC with positive end-expiratory pressure to study the effect of hyperinflation or stretch on respiratory muscle activity, and (4) use of heart-lung transplant patients to determine the effects of vagal denervation on respiratory muscle activity. All subjects were mechanically hyperventilated with positive pressure until inspiratory muscle activity was undetectable and the end-tidal PCO2 decreased to less than 30 mm Hg. End-tidal PCO2 (PETCO2) was increased by either adding CO2 to the inspired gas or decreasing tidal volume (50 ml/min). The PETCO2 where a change in inspiratory muscle activity occurred was taken as the recruitment threshold (PCO2RT). Neuromechanical feedback caused significant inspiratory muscle inhibition during mechanical ventilation, as evidenced by the difference between PCO2RT and PETCO2 during spontaneous eupnea (45 +/- 4 versus 39 +/- 4 mm Hg) and a lower PCO2RT when tidal volume was reduced with a constant frequency and fraction of inspired CO2. Recruitment threshold was unchanged during positive and negative pressure ventilation, during upper and lower airway anesthesia, and in vagally denervated lung transplant patients. These findings demonstrate that neuromechanical feedback causes highly significant inhibition of inspiratory muscle activity during mechanical ventilation; upper and lower airway receptors do not appear to mediate this effect.     

Mechanical controlled hypoventilation in status asthmaticus

This study reports the results obtained with mechanical ventilation in severe respiratory failure secondary to status asthmaticus. Of the 159 patients with status asthmaticus admitted to the Intensive Respiratory Unit over a 5-yr period, 26 required mechanical ventilation for a total of 34 episodes of acute respiratory acidosis. At the time of intubation, 10 patients were in coma and 5 were in respiratory arrest. Controlled mechanical ventilation was maintained for a mean of 2.5 days. Complications were few and reversible. All patients survived. These favorable results are attributed to a new strategy: mechanical ventilation is used to obtain a correction of hypoxemia with hyperoxic mixtures without attempting to restore an adequate alveolar ventilation. The respirator is adjusted to avoid high airway pressures, which appear to be more dangerous than persistent hypercapnia itself. Correction of hypercapnia is obtained later when bronchial obstruction relief provides better conditions of ventilation-perfusion distribution. So the risks of barotrauma and cardiocirculatory failure, which are frequently reported as fatal complications, appear to be significantly decreased.     

机械通气在AECOPD患者治疗中的临床观察

目的观察机械通气在慢性阻塞性肺疾病急性加重期（AECOPD）患者治疗中的应用，进一步探讨机械通气的应用价值。方法观察30例AECOPD患者应用无创或有创机械通气治疗效果，比较机械通气治疗前后动脉血气分析指标和呼吸机参数的变化及其临床意义。结果30例AECOPD患者经机械通气治疗后各项呼吸机参数指标较治疗前均有不同程度的好转，动脉血气分析指标明显好转。无创及有创机械通气治疗后呼吸频率（RR）、呼出潮气量（EVT）、分钟通气量（MV）、平均气道压（MAP）、呼气末正压（PEEP）、压力支持（PS）、吸入氧浓度（FiO2）以及动脉血气分析指标（PH、PaO2、PaCO2）与治疗前比较均有显著性差异（P〈0．01）。结论机械通气在治疗AECOPD患者过程中，有助于改善呼吸肌疲劳，克服气道阻力，降低肺顺应性，从而使呼吸机各项参数及动脉血气分析指标得到改善。