高频振荡通气治疗急性呼吸窘迫综合征新进展

背景 高频振荡通气(high frequency oscillatory ventilation,HFOV)理论上符合肺保护通气策略,越来越多地应用于常规机械通气(conventional mechanical ventilation,CMV)下仍有低氧血症的急性呼吸窘迫综合征(acute respiratory distress syndrome,ARDS)患者. 目的 研究表明HFOV可以有效地改善低氧血症,但肺保护作用利用欠佳,文章旨在阐述如何更好地发挥HFOV的肺保护作用并同时满足氧合和安全性要求. 内容 总结以往HFOV应用于ARDS患者的研究,并讨论HFOV临床应用的相关问题. 趋向 基于大规模前瞻性随机对照研究结果,建议HFOV目前应作为常规肺保护性通气失败的补救措施.在使用HFOV前,要慎重考虑深度镇静肌松、血流动力学变化和噪音等对患者病情的影响.     

液体通气——ARDS治疗新途径

ARDS被认识以来,人们先后使用了一系列药物及通气、氧合技术,但其治愈率一直无突破性提高。晚近研究发现,以液态的全氟溴辛烷(perfluorocarbon, PFC)作携氧介质行液体通气(liquid ventilation, LV)能提高ARDS肺的顺应性,促使其萎陷域复张,减少肺内分流,有效改善气体交换和肺功能,为ARDS的治疗开辟了一条新途径。本文综述了LV的方法、治疗机制和临床应用前景。     

肺保护性通气策略在腹部和胸部手术中应用的研究进展

肺保护性通气策略(lung protective ventilation strategy,LPVS)的应用是近年来在急性肺损伤/急性呼吸窘迫综合征(acute lung injury/acute respiratory distress syndrome,ALI/ARDS)治疗中的重要进展。ALI/ARDS患者采用保护性通气策略,能够改善气体交换和氧合,降低肺泡及循环内炎性因子的水平,缩短机械通气时间,降低患者病死率[1,2]。但对于非ALI/ARDS需要全身麻醉进行手术的病人,采用LPVS是否受益尚不明确[3]。胸部和腹部手术时间较长、创伤较大,本文对腹部和胸部手术中LPVS应用的研究进展文献总结如下。     

不同潮气量机械通气对创伤后急性呼吸窘迫综合征疗效的影响

目的探讨小潮气量(LTV)加呼气末正压(PEEP)机械通气(MV)治疗创伤后急性呼吸窘迫综合征(ARDS)的疗效。方法以18例常规潮气量(8～12ml/kg)MV为对照组,20例小潮气量(5～7ml/kg)加用PEEP的MV模式为观察组,比较两组间血气,RR、HR、MAP、CVP、呼吸机所致肺损伤(VILI)、多脏器功能不全(MODS)发生率及ARDS病死率。结果两组PaO2差异无显著性意义(P>0.05);观察组PaCO2高于对照组(P<0.05);观察组无VILI、MODS及死亡病例发生,对照组2例VILI、2例ARDS并发MODS死亡。结论在ARDS治疗中采用小潮气量加PEEP及允许范围内高碳酸血症(PHC)的保护性通气策略,可明显改善缺氧,减少VILI发生,从而降低其病死率。     

不同通气模式联合肺表面活性物质治疗吸入性损伤的实验研究

严重吸人性损伤病死率在80％以上，吸入性损伤并呼吸衰竭的治疗手段是以呼吸支持为主。常规机械通气（CMV）易产生通气机诱导性肺损伤，高频震荡通气（HFOV）实施机械通气，能明显改善急性呼吸衰竭综合征（ARDS）呼吸系统的顺应性和氧合作用，减轻肺内炎症反应和通气机诱导性肺损伤。外源性肺表面活性物质（PS）应用在PS耗竭的动物模型和PS缺乏新生儿，效果良好。而在吸入性损伤，PS活性明显降低。HFOV联合应用外源性PS是否有协同作用，在个别动物实验已得到了阳性结果。2005年5月，我们在南昌大学第一附属医院烧伤中心，以家兔蒸汽吸入性损伤并发呼吸衰竭模型，应用4种（CMV、HFOV、CMV＋PS和HFOV＋PS）方法进行通气治疗，观察兔动脉氧合和肺组织损伤情况。     

呼吸窘迫综合征患者机械通气模式的探讨

目的 探讨急性呼吸窘迫综合征(ARDS)患者有效的机械通气模式.方法 随机将16例ARDS患者分成对照组和观察组各8例,对照组采用Belevel通气模式,观察组在对照组机械通气模式基础上加用控制性肺膨胀策略,观察治疗前及治疗后12 h、24 h、48 h的氧合指数和二氧化碳分压.结果 二氧化碳分压、氧合指数在不同组别不同观察时间的变化趋势不同(均P＜0.05),观察组与对照组二氧化碳分压、氧合指数的处理主效应差异有显著性意义(均P＜0.05).结论 ARDS患者应用机械通气可改善氧合功能,Belevel机械通气模式加控制性肺膨胀策略效果优于单纯采用Belevel机械通气模式.     

部分液体通气用于呼吸支持

成人ARDS及早产儿RDS时均因缺乏肺泡表面活性物质,致使肺泡萎陷,虽采用机械通气也难以改善其氧合。1976年Shatter首次将氟碳化合物(perflurocarbone)充满于一早产羊的肺内,由于可降低表面活力,并可溶解大量的氧,从而改善了羊肺的气体交换,此后对氟碳化合物进行了广泛的研究。早期采用的是完全液体通气(total liquid ventilation),即用大容量的氟碳化合物将肺完全充满,尚需要一改良的呼吸机先将氟碳化合物在体外进行氧合。近年来改进后的部分液体通气(partial liquid ventilation,PLV)不需要特制的呼吸机,所用的氟碳化合物容量亦较小(等于FRC)。     

全身麻醉期间肺保护通气策略研究进展

背景 机械通气保障全身麻醉手术患者的呼吸和气体交换,但也可能诱发机械通气相关性肺损伤(ventilation induced-lung injury,VILI).随着对VILI发病机制的不断探索,能在一定程度上减轻VILI损伤程度的肺保护性通气策略的研究也越来越深入.目的 就全身麻醉期间肺保护通气策略的研究进展予以综述.内容 综述肺保护机械通气策略、低潮气量通气、复合适当呼气末正压通气(positive end expiratory pressure,PEEP)、肺复张策略(recruiting maneuvers,RM)、控制平台压及FiO2等相关进展与争议.趋向 肺保护性机械通气相关研究已取得一定进展,在全身麻醉过程中采取适当的、个体化的通气策略有待进一步研究.     

ALI/ARDS患者俯卧位通气的研究进展

阐述了急性肺损伤(ALI)及急性呼吸窘迫综合征(ARDS)患者俯卧位通气的理论基础、俯卧位通气的优越性和改善ALI/ARDS患者氧合状况的机制,分析了俯卧位通气治疗的适应证、应用时机、禁忌证、并发症及治疗时间,提出俯卧位通气治疗的实施方法和护理,以期为临床俯卧位通气治疗提供参考。     

不同潮气量机械通气对创伤后急性呼吸窘迫综合征疗效的影响

目的探讨小潮气量（LTV）加呼气末正压（PEEP）机械通气（MV）治疗创伤后急性呼吸窘迫综合征（ARDS）的疗效。方法以18例常规潮气量（8～l2ml／kg）MV为对照组，20例小潮气量（5～7ml／kg）加用PEEP的MV模式为观察组．比较两组间血气，RR、HR、MAP、CVP、呼吸机所致肺损伤（VILI）、多脏器功能不全（MODS）发生率及ARDS病死率。结果两组PaO2差异无显著性意义（P〉0．05）；观察组PaCO2高于对照组（P〈0．05）；观察组无VILI、MODS及死亡病例发生，对照组2例VILI、2例ARDS并发MODS死亡。结论在ARDS治疗中采用小潮气量加PEEP及允许范围内高碳酸血症（PHC）的保护性通气策略，可明显改善缺氧，减少VILI发生，从而降低其病死率。     

Neue Beatmungsmodi

Mechanical ventilation is a cornerstone in the management of critically ill or postoperative patients to facilitate tissue oxygenation and reduce the work of breathing; however, mechanical ventilation per se can also cause or aggravate lung injury, a process referred to as ventilator-induced lung injury (VILI), through several mechanisms including volutrauma, barotrauma and atelectotrauma. Therefore, the goal of novel ventilation modes is not only to reduce the work of respiration and maintain an adequate oxygen supply but also to provide the greatest possible degree of lung protection and patient comfort as well as to keep the risk of VILI as low as possible by making ventilation least invasive and using short ventilation times.In recent years many novel ventilation forms have been developed and scientifically investigated. There is convincing evidence that lung-protective mechanical ventilation with lower tidal volumes and peak pressures leads to a significant improvement in survival of patients with acute respiratory distress syndrome (ARDS) and therefore represents the gold standard in ventilation therapy of patients with lung failure. Although high-frequency oscillatory ventilation (HFOV) theoretically meets the goals of lung-protective ventilation, some recently published randomized trials demonstrated that routine use of HFOV in ARDS patients is clearly not beneficial and may in fact be harmful with a higher mortality rate.Several small studies have demonstrated the physiological benefits of novel, non-conventional ventilator modes including neurally adjusted ventilatory assist (NAVA) and INTELLiVENT® with a better synchronicity with the patient and low rates of necesssary interventions on the respirator by personnel. However, there is currently insufficient evidence that these modern ventilation forms are superior to the conventional modes of ventilation with respect to clinically relevant outcome parameters. Owing to its ability to very quickly show changes in regional lung ventilation and perfusion, electrical impedance tomography (EIT) may be a valuable tool to adjust ventilator settings for the individual patient at the bedside but the available scientific evidence with respect to clinically relevant endpoints is currently inadequate.     

High frequency oscillatory ventilation in burn patients with the acute respiratory distress syndrome

BACKGROUND: High frequency oscillatory ventilation (HFOV) improves gas exchange while providing lung protective effects during the ventilation of patients with the acute respiratory distress syndrome (ARDS). The purpose of this study was to review our experience with HFOV in adult burn patients with oxygenation failure secondary to ARDS. METHODS: Retrospective cohort review of all burn patients treated with HFOV at a regional adult burn center. RESULTS: All values are reported as the mean +/- standard deviation (S.D.). HFOV was used on 28 occasions in 25 patients (age 44 +/- 16 years, %TBSA burns 40 +/- 15, and a 28% incidence of inhalation injury) who had severe oxygenation failure from ARDS (PaO2/FiO2 ratio 98 +/- 26, and oxygenation index (OI) (FiO2 x 100 x mean airway pressure/PaO2) 27 +/- 10) following 4.8 +/- 4.4 days of conventional mechanical ventilation (CMV). After switching from CMV to HFOV, there were significant improvements in the PaO(2)/FiO2 ratio within 1h and in the oxygenation index within 24 h. The duration of HFOV was 6.1 +/- 5.8 days. HFOV was continued during 26 surgeries for 14 patients where a mean of 18 +/- 9% TBSA burns were excised and closed. The only complications related to HFOV were three episodes of severe hypercapnia. In-hospital mortality was 32%. CONCLUSIONS: HFOV was safe, and was highly effective in correcting oxygenation failure associated with ARDS in burn patients, and can be successfully used as an intra-operative ventilation modality for burn patients.     

High frequency oscillatory ventilation for surgical patients with acute respiratory distress syndrome

BACKGROUND: Numerous studies have suggested that high-frequency oscillatory ventilation (HFOV) used as rescue therapy may improve oxygenation in acute respiratory distress syndrome (ARDS) patients. The purpose of this study is to analyze the efficacy and safety of HFOV in surgical patients with ARDS. METHODS: A total of 16 surgical ARDS patients with severe oxygenation failure received HFOV, despite aggressive conventional mechanical ventilatory support. Mean airway pressure was initially set 3 to 5 cm H2O higher than that for conventional ventilation and was subsequently adjusted to maintain oxygen saturation > or = 90% and FiO2 < or =0.6. Oxygenation, ventilation, and hemodynamic parameters were measured during conventional ventilation before initiating HFOV and during HFOV support for a total of 40 hours. Other outcome measures included duration of HFOV, successful weaning rate, cause of failure, complications, survival rate, and cause of death. RESULTS: There was a considerable increase in Pao2/FiO2 ratio after 30 minutes, and this increase was maintained after 12 hours of HFOV throughout the study. There was a significant decrease in oxygenation index after 24 hours of HFOV support. There was no significant change in blood pressure associated with initiation and administration of HFOV. The successful weaning rate from HFOV to conventional ventilation was 75%. The intensive care unit survival rate was 43.8% and hospital survival rate was 37.5%. CONCLUSION: High-frequency oscillatory ventilation was effective and safe in correcting oxygenation failure associated with ARDS in surgical patients. Future research is warranted to identify the suitable patients, timing, and optimal strategy for applying HFOV.     

Early treatment with arteriovenous extracorporeal lung assist and high-frequency oscillatory ventilation in a case of severe acute respiratory distress syndrome

BACKGROUND: Lung protective ventilation can reduce mortality in acute respiratory distress syndrome (ARDS). However, many patients with severe ARDS remain hypoxemic and more aggressive ventilation is necessary to maintain sufficient gas exchange. Pumpless arteriovenous extracorporeal lung assist (av-ECLA) has been shown to remove up to 95% of the systemic CO(2) production, thereby allowing ventilator settings and modes prioritizing oxygenation and lung protection. High-frequency oscillatory ventilation (HFOV) is an alternative form of ventilation that may improve oxygenation while limiting the risk of further lung injury by using extremely small tidal volumes (VT). METHODS: We discuss the management of a patient suffering from severe ARDS as a result of severe bilateral lung contusions and pulmonary aspiration. RESULTS: Severe ARDS developed within 4 h after intensive care unit admission. Conventional mechanical ventilation (CV) with high-airway pressures and low VT failed to improve gas exchange. Av-ECLA was initiated to achieve a less aggressive ventilation strategy. VT was reduced to 2-3 ml/kg, but oxygenation did not improve and airway pressures remained high. HFOV (8-10 Hz) was started using a recruitment strategy and oxygenation improved within 2 h. After 5 days, the patient was switched back to CV uneventfully and av-ECLA was removed after 8 days. CONCLUSION: The combination of two innovative treatment modalities resulted in rapid stabilization and improvement of gas exchange during severe ARDS refractory to conventional lung protective ventilation. During av-ECLA, extremely high oscillatory frequencies were used minimizing the risk of baro- and volutrauma.     

How to prevent ventilator-induced lung injury?

The experimental evidence that ventilator could injure lungs through the application of excessive end-inspiratory volumes and transpulmonary pressures has led to major changes in the clinical management of patients suffering from the acute respiratory distress syndrome (ARDS). The prevention of ventilator-induced lung injury has become one of the main goals of current ventilator strategies for patients with ARDS as well as for patients with normal lungs that require mechanical ventilation. Tidal volume reduction allowed for a reduction in mortality that confirmed the clinical relevance of ventilator-induced lung injury. In contrast, strategies for setting positive end-expiratory pressure (PEEP) have been proposed but the optimal PEEP level remains unsettled. Considerable efforts have been made within the last decades to try to develop new ventilator strategies as well as pharmacological and mechanical measures in order to prevent VILI and further improve the outcome of ARDS patients. This review will strive to describe seminal experimental and clinical studies that aimed at preventing the development of VILI.     

An approach to ventilation in acute respiratory distress syndrome.

Appropriate management of patients with acute respiratory distress syndrome (ARDS) represents a challenge for physicians working in the critical care environment. Significant advances have been made in understanding the pathophysiology of ARDS. There is also an increasing appreciation of the role of ventilator-induced lung injury (VILI). VILI is most likely related to several different aspects of ventilator management: barotrauma due to high peak airway pressures, lung overdistension or volutrauma due to high transpulmonary pressures, alveolar membrane damage due to insufficient positive end expiratory pressure levels and oxygen-related cell toxicity. Various lung protective strategies have been suggested to minimize the damage caused by conventional modes of ventilation. These include the use of pressure- and volume-limited ventilation, the use of the prone position in the management of ARDS, and extracorporeal methods of oxygen delivery and carbon dioxide removal. Although the death rate resulting from ARDS has been declining over the past 10 years, there is no evidence that any specific treatment or change in approach to ventilation is the cause of this improved survival.     

Combination of extracorporeal membrane oxygenation and high-frequency oscillatory ventilation saved a child with severe ARDS after pulmonary resection

We report a case in which a 2-year-old girl who underwent a right middle and lower lung lobectomy for congenital cystic adenomatoid malformation suffered massive bleeding and developed acute respiratory distress syndrome (ARDS) during the operation. She was ventilated with a high level of F_IO₂ (0.75–1.0), PEEP (10–20 cmH₂O), and PIP (33–55 cmH₂O) to maintain SPO₂ (>90%). Following transfer to the ICU, continuous hemodialysis was introduced to reduce excessive blood volume. However, pulmonary oxygenation did not improve, and marked subcutaneous emphysema occurred on postoperative day 3 (POD 3). We introduced venovenous (V-V) extracorporeal membrane oxygenation (ECMO) to rest the lung, and V-V ECMO was changed to right and left atrial ECMO because of unsatisfactory oxygen support on POD 23. A CT scan showed almost the entire lung had collapsed, even though we had administered diuretics, steroids, nitric oxide, sivelestat, and surfactant for ARDS. We applied high-frequency oscillatory ventilation (HFOV) with a mean airway pressure of 20 cmH₂O, frequency of 9.2 Hz, and amplitude of 38 cmH₂O on POD 45. The collapsed lung was then gradually recruited, and pulmonary oxygenation improved (P/F ratio = 434). ECMO was successfully weaned on POD 88. The patient required a tracheostomy, but she was able to function without a ventilator on POD 142. Although HFOV has failed to show a mortality benefit in ARDS patients, the unique lung recruitment by HFOV can be a useful therapeutic option for severe ARDS patients in combination with sufficient lung rest produced by ECMO.     

Recruiting maneuvers in ALI/ARDS

Mechanical ventilation, a life saving procedure in ARDS aims to optimally ventilate the patient and to avoid at the same time the ventilator induced lung injury (VILI). In ARDS the lung contains a variable portion of collapsed alveoli witch impair the normal oxygenation. While the positive end-expiratory pressure (PEEP) can prevent further alveolar collapse the recruiting maneuvers are able to open the already collapsed ones. Multiple recruiting maneuvers are reported in the literature but there is no consensus regarding the optimal one(s), as each maneuver is only partially efficient and has several down falls. While in animal studies theses maneuvers have proved their efficiency and safety, there are not enough humans studies to guide the decision on how, when and which technique should be used.     

Emerging modes of ventilation in the intensive care unit

Potentially harmful effects of positive pressure mechanical ventilation have been recognized since its inception in the 1950s. Since then, the risk factors for and mechanisms of ventilator-induced lung injury (VILI) have been further characterized. Publication of the ARDSnet tidal volume trial in 2000 demonstrated that a ventilator strategy limiting tidal volumes and plateau pressure in patients with acute respiratory distress syndrome was associated with a 22% reduction in mortality. Since then, a variety of ventilator modes have emerged seeking to improve gas exchange, reduce injurious effects of ventilation, and improve weaning from the ventilator. We review here emerging ventilator modes in the intensive care unit (ICU). Airway pressure release ventilation seeks to optimize alveolar recruitment and maintain spontaneous ventilatory effort. It is associated with improved indices of respiratory and cardiovascular physiology, but data to support outcome benefit are lacking. High-frequency oscillatory ventilation is associated with improvements in gas exchange, but outcome data are conflicting. Extracorporeal modes of ventilation continue to evolve, and extra-corporeal CO(2) removal is a technique that could be used in non-specialist ICUs. Proportional-assist ventilation and neutrally adjusted ventilator assist are modes that vary level of assistance with patient ventilatory effort. They result in greater patient-ventilator synchrony, but at present there is no evidence of a reduction in the duration of mechanical ventilation or outcome benefit. Although the use of many of these modes is likely to increase in intensive care units, further evidence of a beneficial effect is desirable before they are recommended.     

High frequency oscillatory ventilation in adult patients with acute respiratory distress syndrome--a retrospective study

BACKGROUND: At present there are limited data about the effects of high frequency oscillatory ventilation (HFOV) in adult patients with acute respiratory distress syndrome (ARDS). This study evaluates efficacy of HFOV in such patients. METHODS: Sixteen ARDS patients, mean age 38.2 years (range 18-76), that underwent HFOV between 1997 and 2001 were enrolled in the study and evaluated in retrospect. FIo2, arterial blood gases, mean airway pressure (mean Paw), blood pressure, heart rate and central venous pressure were recorded by 4, 8, 12, 24, 48 and 72 h of HFOV and compared to conventional mechanical ventilation (CMV) at baseline (4 h prior to HFOV). RESULTS: On admission to the ICU, mean Simplified Acute Physiology score (SAPS II) was 40.3 (SD 12.6). Main causes of ARDS were pneumonia (9/16) and burn injuries (4/16). At baseline the patients had severe ARDS as noted by a mean lung injury score (LIS) of 3.2 (SD 0.3) and Pao2/FIo2 ratio 12.2 (SD 3.2) kPa. Within 4 h of HFOV, Pao2/FIo2 increased to 17.3 (SD 5.9) kPa (P = 0.016). Throughout HFOV, Pao2/FIo2 was significantly higher than at baseline. There were no significant changes in haemodynamic parameters. Ending HFOV after 6.6 (SD 3.2) days, survivors (n = 11) significantly reduced their Sequential Organ Failure Assessment Score (SOFA) compared to baseline. Survival at 3 months was 68.8%. CONCLUSION: HFOV effectively improves oxygenation without haemodynamic compromise. During HFOV, the SOFA score may predict outcome.