急性呼吸窘迫综合征患者侧卧位通气与俯卧位通气的临床疗效观察

目的 评价侧卧位通气和俯卧位通气对急性呼吸窘迫综合征（ARDS）患者的临床疗效。并对两种体位通气方法进行对比观察。方法 将ICU2005年收治的23例ARDS患者随机分为两组，分别施行侧卧位通气（15例）和俯卧住通气（8例），监测仰卧位时，体位改变后1、2、4h及转复为仰卧位后1h的呼吸循环指标，并分别进行比较。结果 体位改变后1、2、4h及转复为仰卧住后1h，两组患者动脉血氧分压、氧舍指数均较仰卧位时升高（P〈0．05），心率、平均动脉压、气道峰压及动脉血二氧化碳分压与仰卧位时比较差异无统计学意义（P〉0．05）。以氧分压升高10mmHg为有效标准。治疗有效率侧卧位组73．3％，俯卧位组66．7％，两组比较差异无统计学意义（P〉0．05）。结论 作为ARDS机械通气治疗手段，侧卧位通气与俯卧位通气治疗的有效率接近。但侧卧位实施更容易，护理更方便。并发症少，值得临床进一步探讨。     

Tidal volume delivery during high-frequency oscillatory ventilation in adults with acute respiratory distress syndrome

OBJECTIVE: a) Characterize how ventilator and patient variables affect tidal volume during high-frequency oscillatory ventilation; and b) measure tidal volumes in adults with acute respiratory distress syndrome during high-frequency oscillatory ventilation. DESIGN: Observational study. SETTING: Research laboratory and medical intensive care unit. PATIENTS: Test lung and patients with acute respiratory distress syndrome. INTERVENTIONS: Using a previously validated hot wire anemometer placed in series with a Sensormedics 3100B high-frequency ventilator, an endotracheal tube, and a test lung, tidal volume was measured at different combinations of frequency (4, 6, 8, 10, and 12 Hz), pressure amplitude (50, 60, 70, 80, and 90 cm H2O), mean airway pressure (20, 30, and 40 cm H2O), test lung compliance (10, 30, and 50 mL/cm H2O), endotracheal tube internal diameter (6, 7, and 8 mm), bias flow (20, 30, and 40 L/min), and inspiratory/expiratory ratio (1:2 and 1:1). In patients, tidal volume was measured at baseline ventilator settings and at baseline frequency +/-2 Hz and baseline pressure amplitude +/-10 cm H2O. MEASUREMENTS AND MAIN RESULTS: Measured tidal volumes were 23-225 mL during high-frequency oscillatory ventilation of the test lung. A 2-Hz increase in frequency and a 10-cm H2O increase in pressure amplitude caused a 21.3% +/- 4.1% decrease and 21.4% +/- 3.4% increase in tidal volume, respectively. Decreasing endotracheal tube internal diameter from 8 mm to 7 mm and from 7 mm to 6 mm caused a 15.3% +/- 1.7% and 18.9% +/- 2.1% reduction in tidal volume, respectively. Increasing bias flow from 20 L/min to 30 L/min increased tidal volume by 11.2% +/- 3.9%. Further increases in bias flow, changes in compliance, and changes in mean airway pressure had little effect. Tidal volumes measured in acute respiratory distress syndrome patients were 44-210 mL. A 2-Hz increase in frequency was associated with a 23.1% +/- 6.3% decrease in tidal volume. In contrast to the test lung data, a 10-cm H2O increase in pressure amplitude resulted in only a 5.6% +/- 4.5% increase in tidal volume. CONCLUSIONS: Tidal volumes are not uniformly small during high-frequency oscillatory ventilation. The primary determinant of tidal volume in adults with acute respiratory distress syndrome during high-frequency oscillatory ventilation with the Sensormedics 3100B is frequency. Test lung findings suggest that endotracheal tube internal diameter is also an important determinant of tidal volume.     

Recruitment maneuvers during prone positioning in patients with acute respiratory distress syndrome

OBJECTIVE: To evaluate the interaction of recruitment maneuvers and prone positioning on gas exchange and venous admixture in patients with early extrapulmonary acute respiratory distress syndrome ventilated with high levels of positive end-expiratory pressure. We hypothesized that a sustained inflation performed after 6 hrs of prone positioning would induce sustained improvement in oxygenation (Pao2/Fio2) and venous admixture. DESIGN: Prospective, interventional study. SETTING: Tertiary care, postoperative intensive care unit. PATIENTS: Fifteen patients with early extrapulmonary acute respiratory distress syndrome. INTERVENTIONS: After 6 hrs of prone positioning, a sustained inflation was performed with 50 cm H2O maintained for 30 secs. Data were recorded in supine position, after 6 hrs of prone positioning, at 3, 30, and 180 mins following the sustained inflation. MEASUREMENTS AND MAIN RESULTS: A response to prone positioning was observed in nine of 15 patients leading to an improvement of Pao2/Fio2 (147 +/- 37 torr vs. 225 +/- 77 torr, p = .005) and venous admixture (35.4 +/- 8.3% vs. 28.9 +/- 9.8%, p = .001). Six patients did not respond to prone positioning. Following the sustained inflation, the responders to prone positioning showed a further increase of Pao2/Fio2 and decrease of venous admixture at 3 mins (Pao2/Fio2, 225 +/- 77 torr vs. 368 +/- 90 torr, p = .018; venous admixture, 28.9 +/- 9.8% vs. 18.9 +/- 6.7%, p = .05). In all six nonresponders to prone positioning, an improvement of Pao2/Fio2 and venous admixture occurred at 3 mins following the sustained inflation (128 +/- 18 torr vs. 277 +/- 59 torr, p = .03; venous admixture, 34.2 +/- 6.0% vs. 23.8 +/- 6.3%, p = .05). The beneficial effects of the sustained inflation remained significantly elevated over 3 hrs in responders and nonresponders to prone positioning. CONCLUSION: In patients with early extrapulmonary acute respiratory distress syndrome, a sustained inflation performed after 6 hrs of prone positioning induced further and sustained improvement of oxygenation and venous admixture in both responders and nonresponders to prone positioning.     

Efficacy and safety of prone positioning for patients with acute respiratory distress syndrome

This article presents an overview of a literature review on how prone positioning can alleviate pathophysiological changes in ARDS and improve ventilation and perfusion. Improvement of gas exchange, efficiency of oxygenation and lung function are emphasized. Literature on the pathophysiology of ARDS, and the physiological effects of prone positioning on haemodynamics and lung function is examined. There are both advantages and disadvantages in turning a patient from the supine to the prone position. There are also contraindications in rotating between the supine and prone positions. Nevertheless, by rotating patients with ARDS, it is possible to achieve a significant improvement in A-aDO2, decrease shunting, and therefore improve oxygenation without use of expensive, invasive and experimental procedures. Placing patients with ARDS in the prone position can reduce inspiratory oxygen concentrations and peak inspiratory pressures, which minimizes the chance for barotrauma and the iatrogenic effects of hyperventilation oxygen toxicity.     

High-frequency oscillatory ventilation in adults with acute respiratory distress syndrome

The last decade has seen increased appreciation of ventilator-induced lung injury. The understanding that the process of mechanical ventilation can itself damage lungs has spurned the search for ventilation strategies that are more lung protective. High-frequency oscillatory ventilation is a mode of high-frequency ventilation that may accomplish all of the current goals of lung protection. Historically, much of the data evaluating high-frequency oscillatory ventilation came from neonatal and pediatric populations. In the past year, a number of provocative and exciting studies have been published that contribute significantly to our understanding of high-frequency oscillatory ventilation, its role in preventing and reducing ventilator-induced lung injury, and its use in the support of adult patients with lung injury. In this article, we discuss the current understanding of high-frequency oscillatory ventilation and highlight the most recent literature addressing its application in adult patients with acute respiratory distress syndrome.     

Efficacy and adverse events of high-frequency oscillatory ventilation in adult patients with acute respiratory distress syndrome: a meta-analysis

Introduction

Theoretically, high-frequency oscillatory ventilation (HFOV) achieves all goals of a lung-protective ventilatory mode and seems ideal for the treatment of adult patients with acute respiratory distress syndrome (ARDS). However, its effects on mortality and adverse clinical outcomes remain uncertain given the paucity of high-quality studies in this area. This meta-analysis was performed to evaluate the efficacy and adverse events of HFOV in adults with ARDS.

Methods

We searched PubMed, EMBASE and Cochrane Central Register of Controlled Trials through February 2014 to retrieve randomized controlled trials of HFOV in adult ARDS patients. Two independent reviewers extracted data on study methods, clinical and physiological outcomes and adverse events. The primary outcome was 30-day or hospital mortality. Risk of bias was evaluated with the Cochrane Collaboration’s tool. Mortality, oxygenation and adverse effects of HFOV were compared to those of conventional mechanical ventilation. A random-effects model was applied for meta-analysis.

Results

A total of five trials randomly assigning 1,580 patients met inclusion criteria. Pooled data showed that HFOV significantly improved oxygenation on day one of therapy (four studies; 24% higher; 95% confidence interval (CI) 11 to 40%; P <0.01). However, HFOV did not reduce mortality risk (five studies; risk ratio (RR) 1.04; 95% CI 0.83 to 1.31; P = 0.71) and two early terminated studies suggested a harmful effect of HFOV in ARDS (two studies; RR 1.33; 95% CI 1.09 to 1.62; P <0.01). Safety profiles showed that HFOV was associated with a trend toward increased risk of barotrauma (five studies; RR 1.19; 95% CI 0.83 to 1.72; P = 0.34) and unfavorable hemodynamics (five studies; RR 1.16; 95% CI 0.97 to 1.39; P = 0.12).

Conclusions

HFOV improved oxygenation in adult patients with ARDS; however, it did not confer a survival benefit and might cause harm in the era of lung-protective ventilation strategy. The evidence suggests that HFOV should not be a routine practice in ARDS and further studies specifically selecting patients for this ventilator mode should be pursued.     

High-frequency oscillatory ventilation in adult acute respiratory distress syndrome

Objective This study examined whether ARDS patients in whom predefined ventilator settings fail to maintain oxygenation and CO₂ removal can be safely transitioned to high-frequency oscillatory ventilation (HFOV), and whether HFOV use is efficacious.Design and setting Prospective observational study in the 14-bed intensive care unit of a university hospital.Patients and participants 42 patients with ARDS (APACHE II score 28 (IQR 24–37) and ventilation time prior HFOV 3.0 days (0.7–9.1).Measurements and results Gas exchange parameters and ventilator data were recorded before and during HFOV treatment (–12 h, –6 h, baseline, 10 min, 1 h, 6 h, 12 h, 24 h). Primary endpoints included: (a) P_aO₂/FIO₂ ratio 24 h after start of HFOV treatment or the last point of measurement if HFOV ended within the first 24 h; (b) HFOV-related complications. Post hoc analysis assessed the relationship between outcome and the response to HFOV, and between outcome and time of mechanical ventilation prior to HFOV. At baseline the median P_aO₂/FIO₂ ratio was 95 (IQR 62–129); after 24 h of HFOV the P_aO₂/FIO₂ ratio had increased significantly to 165 (88–225); only one patient developed a unilateral pneumothorax. Of the 42 patients 18 (43%) had died by day 30. Subset analyses showed a significantly higher 30-day mortality rate in patients with at least 3 days of mechanical ventilation prior to HFOV (64%) and in patients without oxygenation improvement after 24 h on HFOV (71%).Conclusions HFOV is an effective and safe method to ventilate ARDS patients. Failure to improve oxygenation within 24 h of HFOV is associated with high mortality.An editorial regarding this article can be found in the same issue     

Physiological predictors of survival during high-frequency oscillatory ventilation in adults with acute respiratory distress syndrome

Introduction

Data that provide clinical criteria for the identification of patients likely to respond to high-frequency oscillatory ventilation (HFOV) are scarce. Our aim was to describe physiological predictors of survival during HFOV in adults with severe acute respiratory distress syndrome (ARDS) admitted to a respiratory failure center in the United Kingdom.

Methods

Electronic records of 102 adults treated with HFOV were reviewed retrospectively. We used logistic regression and receiving-operator characteristics curve to test associations with oxygenation and mortality.

Results

Patients had severe ARDS with a mean (SD) Murray''s score of 2.98 (0.7). Partial pressure of oxygen in arterial blood to fraction of inspired oxygen (PaO₂/FiO₂) ratio and oxygenation index improved only in survivors. The earliest time point at which the two groups differed was at three hours after commencing HFOV. An improvement of >38% in PaO₂/FiO₂ occurring at any time within the first 72 hours, was the best predictor of survival at 30 days (area under the curve (AUC) of 0.83, sensitivity 93%, specificity 78% and a positive likelihood ratio (LR) of 4.3). These patients also had a 3.5 fold greater reduction in partial pressure of carbon dioxide in arterial blood (PaCO₂). Multivariate analysis showed that HFOV was more effective in younger patients, when instituted early, and in patients with milder respiratory acidosis.

Conclusions

HFOV is effective in improving oxygenation in adults with ARDS, particularly when instituted early. Changes in PaO₂/FiO₂ during the first three hours of HFOV can identify those patients more likely to survive.     

Comparison of high-frequency jet ventilation to conventional ventilation in adults with respiratory distress syndrome

Sixteen patients with acute respiratory failure (ARF) were studied. In group I (12 patients, 15 explorations) patients were treated with continuous positive pressure ventilation (CPPV) during conventional ventilation (CV), pulmonary lesions (PL) were severe (Q_sp/Q_t=0.24–0.16 with PEEP=14±7 cm H₂O) and high-frequency jet ventilation (HFJV) was performed without spontaneous ventilation (SV). In group II (5 patients, 12 explorations) patients were treated with intermittent mandatory ventilation (IMV) during CV, PL were moderate (Q_sp/Q_t=0.13–0.05 with PEEP=8±3 cm H₂O) and HFJV was performed with SV. In both groups, frequency was 120 c/mn and I:E ratio=1:2. The cannula size, the driving pressure and the PEEP (water column) were progressively adapted to obtained the same blood gases as those observed during CV, FIO₂ being the same. Results on HFJV were compared to CV. In both groups there were no differences between PaCO₂, PaO₂, FIO₂, Q_sp/Q_t during CV and HFJV. In group I peak airway pressure (PAWP), mean artery pressure (MAP), heart rate (HR), transmural mean pulmonary and wedge pressure (MPAP_tm, PWP_tm) were not different. Mean airway pressure (MAWP), PEEP and pleural pressure (PP) were higher, cardiac index (CI) was lower. In group II, PP, CI, MAP, HR, MPAP_tm, MPWP_tm were not different. PAWP was lower, MAWP and PEEP were higher. We conclude that during HFJV it is possible to obtain the same blood gas as during CV, but HFJV without CV may not be indicated in patients with severe PL, because circulatory impairment is higher.     

Prone positioning in patients with acute respiratory distress syndrome

Prone positioning is a technique used to treat patients with acute respiratory distress syndrome (ARDS). Nurses are ideally placed to initiate and manage prone positioning. This article examines the aetiology of ARDS and how nurses can identify this condition. Patient groups that benefit most from prone positioning are considered as well as the research evidence on the use of prone positioning in the treatment of ARDS. This article addresses nurse involvement in delivering therapy and suggests that nurses alert members of the multidisciplinary team to the possible use of this therapy.     

Mechanisms of the effects of prone positioning in acute respiratory distress syndrome

Introduction

Prone positioning has been used for many years in patients with acute respiratory distress syndrome (ARDS). The initial reason for prone positioning in ARDS patients was improvement in oxygenation. It was later shown that mechanical ventilation in the prone position can be less injurious to the lung and hence the primary reason to use prone positioning is prevention of ventilator-induced lung injury (VILI).

Material and methods

A large body of physiologic benefits of prone positioning in ARDS patients accumulated but these failed to translate into clinical benefits. More recently, meta-analyses and randomized controlled trial in a specific subgroup of ARDS patients demonstrated that prone positioning can improve survival. This review covers the effects of prone positioning on oxygenation, respiratory mechanics, and VILI.

Conclusions

We conclude with the effects of prone positioning on patient outcome, in particular on survival.     

俯卧位机械通气在急性呼吸窘迫综合症患者中的应用状况

急性呼吸窘迫综合征（acuterespiratorydistresssyndrome,ARDS）是指肺内、外严重疾病导致以肺毛细血管弥漫性损伤、通透性增强为基础,以肺水肿、透明膜形成和肺不张为主要病理变化,以进行性呼吸窘迫和难治性低氧血症为临床特征的急性呼吸衰竭综合征。ARDS是急性肺损伤（acutelunginjury,ALI）发展到后期的典型表现。该病起病急骤,发展迅猛,预后极差,     

Bench-to-bedside review: High-frequency oscillatory ventilation in adults with acute respiratory distress syndrome

Mechanical ventilation is the cornerstone of therapy for patients with acute respiratory distress syndrome (ARDS). Paradoxically, mechanical ventilation can exacerbate lung damage – a phenomenon known as ventilator-induced lung injury. While new ventilation strategies have reduced the mortality rate in patients with ARDS, this mortality rate still remains high. High-frequency oscillatory ventilation (HFOV) is an unconventional form of ventilation that may improve oxygenation in patients with ARDS, while limiting further lung injury associated with high ventilatory pressures and volumes delivered during conventional ventilation. HFOV has been used for almost two decades in the neonatal population, but there is more limited experience with HFOV in the adult population. In adults, the majority of the published literature is in the form of small observational studies in which HFOV was used as 'rescue' therapy for patients with very severe ARDS who were failing conventional ventilation. Two prospective randomized controlled trials, however, while showing no mortality benefit, have suggested that HFOV, compared with conventional ventilation, is a safe and effective ventilation strategy for adults with ARDS. Several studies suggest that HFOV may improve outcomes if used early in the course of ARDS, or if used in certain populations. This review will summarize the evidence supporting the use of HFOV in adults with ARDS.