Prospective trial of high-frequency oscillation in adults with acute respiratory distress syndrome.

OBJECTIVE: To evaluate the safety and efficacy of high-frequency oscillatory ventilation (HFOV) in adult patients with the acute respiratory distress syndrome (ARDS) and oxygenation failure. DESIGN: Prospective, clinical study. SETTING: Intensive care and burn units of two university teaching hospitals. PATIENTS: Twenty-four adults (10 females, 14 males, aged 48.5 +/- 15.2 yrs, Acute Physiology and Chronic Health Evaluation II score 21.5 +/- 6.9) with ARDS (lung injury score 3.4 +/- 0.6, Pao2/Fio2 98.8 +/- 39.0 mm Hg, and oxygenation index 32.5 +/- 19.6) who met one of the following criteria: Pao2 < or =65 mm Hg with Fio2 > or =0.6, or plateau pressure > or =35 cm H2O. INTERVENTIONS: HFOV was initiated in patients with ARDS after varying periods of conventional ventilation (CV). Mean airway pressure (Paw) was initially set 5 cm H2O greater than Paw during CV, and was subsequently titrated to maintain oxygen saturation between 88% and 93% and Fio2 < or =0.60. MEASUREMENTS AND MAIN RESULTS: Fio2, Paw, pressure amplitude of oscillation, frequency, blood pressure, heart rate, and arterial blood gases were monitored during the transition from CV to HFOV, and every 8 hrs thereafter for 72 hrs. In 16 patients who had pulmonary artery catheters in place, cardiac hemodynamics were recorded at the same time intervals. Throughout the HFOV trial, Paw was significantly higher than that applied during CV. Within 8 hrs of HFOV application, and for the duration of the trial, Fio2 and Paco2 were lower, and Pao2/Fio2 was higher than baseline values during CV. Significant changes in hemodynamic variables following HFOV initiation included an increase in pulmonary artery occlusion pressure (at 8 and 40 hrs) and central venous pressure (at 16 and 40 hrs), and a reduction in cardiac output throughout the course of the study. There were no significant changes in systemic or pulmonary pressure associated with initiation and maintenance of HFOV. Complications occurring during HFOV included pneumothorax in two patients and desiccation of secretions in one patient. Survival at 30 days was 33%, with survivors having been mechanically ventilated for fewer days before institution of HFOV compared with nonsurvivors (1.6 +/- 1.2 vs. 7.8 +/- 5.8 days; p =.001). CONCLUSIONS: These findings suggest that HFOV has beneficial effects on oxygenation and ventilation, and may be a safe and effective rescue therapy for patients with severe oxygenation failure. In addition, early institution of HFOV may be advantageous.     

Comparison of prone positioning and high-frequency oscillatory ventilation in patients with acute respiratory distress syndrome

OBJECTIVE: Both prone position and high-frequency oscillatory ventilation (HFOV) have the potential to facilitate lung recruitment, and their combined use could thus be synergetic on gas exchange. Keeping the lung open could also potentially be lung protective. The aim of this study was to compare physiologic and proinflammatory effects of HFOV, prone positioning, or their combination in severe acute respiratory distress syndrome (ARDS). DESIGN:: Prospective, comparative randomized study. SETTING: A medical intensive care unit. PATIENTS: Thirty-nine ARDS patients with a Pao2/Fio2 ratio <150 mm Hg at positive end-expiratory pressure > or =5 cm H2O. INTERVENTIONS: After 12 hrs on conventional lung-protective mechanical ventilation (tidal volume 6 mL/kg of ideal body weight, plateau pressure not exceeding the upper inflection point, and a maximum of 35 cm H2O; supine-CV), 39 patients were randomized to receive one of the following 12-hr periods: conventional lung-protective mechanical ventilation in prone position (prone-CV), HFOV in supine position (supine-HFOV), or HFOV in prone position (prone-HFOV). MEASUREMENTS AND MAIN RESULTS: Prone-CV (from 138 +/- 58 mm Hg to 217 +/- 110 mm Hg, p < .0001) and prone-HFOV (from 126 +/- 40 mm Hg to 227 +/- 64 mm Hg, p < 0.0001) improved the Pao2/Fio2 ratio whereas supine-HFOV did not alter the Pao2/Fio2 ratio (from 134 +/- 57 mm Hg to 138 +/- 48 mm Hg). The oxygenation index ({mean airway pressure x Fio2 x 100}/Pao2) decreased in the prone-CV and prone-HFOV groups and was lower than in the supine-HFOV group. Interleukin-8 increased significantly in the bronchoalveolar lavage fluid (BALF) in supine-HFOV and prone-HFOV groups compared with prone-CV and supine-CV. Neutrophil counts were higher in the supine-HFOV group than in the prone-CV group. CONCLUSIONS: Although HFOV in the supine position does not improve oxygenation or lung inflammation, the prone position increases oxygenation and reduces lung inflammation in ARDS patients. Prone-HFOV produced similar improvement in oxygenation like prone-CV but was associated with higher BALF indexes of inflammation. In contrast, supine-HFOV did not improve gas exchange and was associated with enhanced lung inflammation.     

High-frequency oscillatory ventilation following prone positioning prevents a further impairment in oxygenation

OBJECTIVE: The improvement in oxygenation with prone positioning is not persistent when patients with acute respiratory distress syndrome (ARDS) are turned supine. High-frequency oscillatory ventilation (HFOV) aims to maintain an open lung volume by the application of a constant mean airway pressure. The aim of this study was to show that HFOV is able to prevent the impairment in oxygenation when ARDS patients are turned back from the prone to the supine position. DESIGN: Prospective, comparative randomized study. SETTING: A medical intensive care unit. PATIENTS: Forty-three ARDS patients with a Pao2/Fio2 ratio <150 at positive end-expiratory pressure > or =5 cm H2O. INTERVENTIONS: After an optimization period, the patients were assigned to one of three groups: a) conventional lung-protective mechanical ventilation in the prone position (12 hrs) followed by a 12-hr period of conventional lung-protective mechanical ventilation in the supine position (CV(prone)-CV(supine)); b) conventional lung-protective mechanical ventilation in the supine position (12 hrs) followed by HFOV in the supine position (12 hrs) (CV(supine)-HFOV(supine)); or c) conventional lung-protective mechanical ventilation in the prone position (12 hrs) followed by HFOV in the supine position (CV(prone)-HFOV(supine) group). MEASUREMENTS AND MAIN RESULTS: Pao2/Fio2 ratio was higher at the end of the study period in the CV(prone)-HFOV(supine) group than in the CV(prone)-CV(supine) group (p < .02). Venous admixture at the end of the study period was lower in the CV(prone)-HFOV(supine) group than in the two other groups. CONCLUSIONS: HFOV maintained the improvement in oxygenation related to prone positioning when ARDS patients were returned to the supine position.     

Acute oxygenation response to inhaled nitric oxide when combined with high-frequency oscillatory ventilation in adults with acute respiratory distress syndrome

OBJECTIVE: To prospectively evaluate the oxygenation effect of inhaled nitric oxide (INO) delivered during high-frequency oscillatory ventilation in adult patients with the acute respiratory distress syndrome and oxygenation failure. DESIGN Prospective, clinical study. SETTING: Intensive care unit of a university teaching hospital. PATIENTS: A total of 23 adults (14 women, 9 men, 44.9 +/- 17.5 yrs, Acute Physiology and Chronic Health Evaluation II score of 28.6 +/- 7.1) with acute respiratory distress syndrome (lung injury score, 3.5 +/- 0.4) with Fio2 of > or = 0.6 and mean airway pressure of >or=28 cm H2O. INTERVENTIONS: INO was initiated at a dose of 5 ppm, and subsequently titrated according to a protocol, to determine the dose (5, 10, or 20 ppm) resulting in the greatest increase in Pao2/Fio2. Blood gas measurements were obtained 10-15 mins after initiation or any increase in INO dosage to assess the effect on Pao2/Fio2. MEASUREMENTS AND MAIN RESULTS: Arterial blood gases and ventilator settings were recorded at four time points: during conventional ventilation just before initiating high-frequency oscillatory ventilation, during high-frequency oscillatory ventilation just before initiating INO, after 30 mins on the optimal dose of INO, and 8-12 hrs after starting INO. Oxygenation index ([Fio2 x mean airway pressure x 100]/Pao2) and Pao2/Fio2 ratios were calculated at the same time intervals. At 30 mins after INO initiation, 83% of patients had a significant increase in blood oxygen tension, defined as > or = 20% increase in Pao2/Fio2. The mean change in Pao2/Fio2 at 30 mins was 38%. In these 19 patients, Pao2/Fio2 was highest at 20 ppm in four patients, at 10 ppm in eight patients, and at 5 ppm in seven patients. Compared with baseline measurements, Pao2/Fio2 improved significantly at both 30 mins (112 +/- 59 vs. 75 +/- 32, p=.01) and 8-12 hrs after INO initiation (146 +/- 52 vs. 75 +/- 32, p<.0001). In addition, oxygenation index was reduced at 8-12 hrs compared with baseline measurements (26 +/- 13 vs. 40 +/- 17, p=.08). CONCLUSIONS: INO delivered at doses of 5 to 20 ppm during high-frequency oscillatory ventilation increases Pao2/Fio2 and may be a safe and effective rescue therapy for patients with severe oxygenation failure.     

Effects of sustained inflation and postinflation positive end-expiratory pressure in acute respiratory distress syndrome: focusing on pulmonary and extrapulmonary forms

OBJECTIVE: To investigate whether the response to sustained inflation and postinflation positive end-expiratory pressure varies between acute respiratory distress syndrome with pulmonary (ARDS(exp)) and extrapulmonary origin (ARDS(exp)). DESIGN: Prospective clinical study. SETTING: Multidisciplinary intensive care unit in a university hospital. PATIENTS: A total of 11 patients with ARDS and 13 patients with ARDS. INTERVENTIONS: A 7 ml/kg tidal volume, 12-15 breaths/min respiratory rate, and an inspiratory/expiratory ratio of 1:2 was used during baseline ventilation. Positive end-expiratory pressure levels were set according to the decision of the primary physician. Sustained inflation was performed by 45 cm H2O continuous positive airway pressure for 30 secs. Postinflation positive end-expiratory pressure was titrated decrementally, starting from a level of 20 cm H2O to keep the peripheral oxygen saturation between 92% and 95%. Fio2 was decreased, and baseline tidal volume, respiratory rate, inspiratory/expiratory ratio were maintained unchanged throughout the study period. MEASUREMENTS AND MAIN RESULTS: Blood gas, airway pressure, and hemodynamic measurements were performed at the following time points: at baseline and at 15 mins, 1 hr, 4 hrs, and 6 hrs after sustained inflation. After sustained inflation, the Pao2/Fio2 ratio improved in all of the patients both in ARDS(p) and ARDS(exp). However, the Pao2/Fio2 ratio increased to >200 in four ARDS(p) patients (36%) and in seven ARDS(p) patients (54%). In two of those ARDS patients, the Pao2/Fio2 ratio was found to be <200, whereas none of the ARDS(p) patients revealed Pao2/Fio2 ratios of <200 at the 6-hr measurement. Postinflation positive end-expiratory pressure levels were set at 16.7 +/- 2.3 cm H O in ARDS(p) and 15.6 +/- 2.5 cm H2O in ARDS. The change in Pao /Fio ratios was found statistically significant in patients with ARDS(p) (p =.0001) and with ARDS(p) (p =.008). Respiratory system compliance increased in ARDS patients (p =.02), whereas the change in ARDS was not statistically significant. CONCLUSIONS: Sustained inflation followed by high levels of postinflation positive end-expiratory pressure provided an increase in respiratory system compliance in ARDS; however, arterial oxygenation improved in both ARDS forms.     

Neuromuscular blocking agents decrease inflammatory response in patients presenting with acute respiratory distress syndrome

OBJECTIVE: To evaluate the effects of neuromuscular blocking agents (NMBAs) on pulmonary and systemic inflammation in patients with acute respiratory distress syndrome ventilated with a lung-protective strategy. DESIGN: Multiple-center, prospective, controlled, and randomized trial. SETTING: One medical and two medical-surgical intensive care units. PATIENTS: A total of 36 patients with acute respiratory distress syndrome (Pao2/Fio2 ratio of < or =200 at a positive end-expiratory pressure of > or =5 cm H2O) were included within 48 hrs of acute respiratory distress syndrome onset. INTERVENTIONS: Patients were randomized to receive conventional therapy plus placebo (n = 18) or conventional therapy plus NMBAs (n = 18) for 48 hrs. Both groups were ventilated with a lung-protective strategy (tidal volume between 4 and 8 mL/kg ideal body weight, plateau pressure of < or =30 cm H2O). MEASUREMENTS AND MAIN RESULTS: Bronchoalveolar lavages and blood samples were performed, before randomization and at 48 hrs, to determine the concentrations of tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, and IL-8. Pao2/Fio2 ratio was evaluated before randomization and at 24, 48, 72, 96, and 120 hrs. A decrease over time in IL-8 concentrations (p = .034) was observed in the pulmonary compartment of the NMBA group. At 48 hrs after randomization, pulmonary concentrations of IL-1beta (p = .005), IL-6 (p = .038), and IL-8 (p = .017) were lower in the NMBA group as compared with the control group. A decrease over time in IL-6 (p = .05) and IL-8 (p = .003) serum concentrations was observed in the NMBA group. At 48 hrs after randomization, serum concentrations of IL-1beta (p = .037) and IL-6 (p = .041) were lower in the NMBA group as compared with the control group. A sustained improvement in Pao2/Fio2 ratio was observed and was reinforced in the NMBA group (p < .001). CONCLUSION: Early use of NMBAs decrease the proinflammatory response associated with acute respiratory distress syndrome and mechanical ventilation.     

High-frequency oscillatory ventilation of the perfluorocarbon-filled lung: dose-response relationships in an animal model of acute lung injury

OBJECTIVE: To examine dose-response relationships regarding the efficiency of gas exchange and hemodynamic function during high-frequency oscillation and partial liquid ventilation (HFO-PLV) of the perfluorocarbon (PFC)-treated lung in a model of acute lung injury. SETTING: An animal research laboratory in a university medical center. DESIGN: A prospective, randomized study comparing animals receiving varying doses (0, 5, 15, and 20 mL/kg) of perflubron during high-frequency oscillatory ventilation (HFOV) with mean airway pressure (Paw) optimized to achieve a minimal percutaneous oxygen saturation (Spo2). SUBJECTS: Nineteen healthy swine (mean weight 28.9 kg) with saline lavage-induced acute lung injury. METHODS: Animals were treated with repetitive saline lavage to achieve a uniform degree of acute lung injury (Spo2 < or =90% on an Fio2 of 1.0). After lung injury, subjects were converted to HFOV, and lung volume was optimized. HFO-PLV was initiated by instillation of perflubron at a rate of 0.5 mL.kg-1.min-1 to achieve total doses of 5, 15, and 20 mL/kg. After PFC dosing, the only experimental manipulation consisted of adjustment of Paw to achieve an Spo2 of 90% +/- 2% with Fio2 of 0.6. Gas exchange, hemodynamic variables, and pulmonary mechanics data were collected over a 1-hr period. Five control animals were not dosed with perflubron and remained on HFOV for the 1-hr period of data collection. MEASUREMENTS AND MAIN RESULTS: After lung volume recruitment with HFOV, the initiation of HFO-PLV was best tolerated with the two lower doses in our protocol. There were essentially no changes in Paco2 or pH between groups over the dosing interval. After dosing, analysis of variance demonstrated a PFC dose-dependent effect for oxygenation index (p =.01) only; the lowest oxygenation index was found in the 15 mL/kg group (p =.01). In the 15 mL/kg group, the Paw decreased steadily from 20.6 +/- 3.4 cm H2O at the end of dosing to 18.0 +/- 4.9 cm H2O at 60 mins. The Pao2 increased from 113 +/- 51 torr (15.06 +/- 6.79 kPa) to 134 +/- 49 torr (17.86 +/- 6.53 kPa) during this period and was associated with a decreasing oxygenation index (from 11.4 +/- 2.0 to 9.3 +/- 1.5). The cardiac index and pulmonary vascular resistance did not change significantly during the dosing period and were relatively stable after the completion of dosing. CONCLUSIONS: The combination of HFOV and perflubron administration was well tolerated hemodynamically and was not associated with deterioration of gas exchange during dosing. Our data suggest that the optimal dose of perflubron to achieve the lowest oxygenation index during HFO-PLV is between 5 and 15 mL/kg. The combination of HFOV and perflubron administration is a novel strategy in the treatment of acute lung injury that shows some promise and merits additional investigation. We hope in future studies to address the histopathologic effects of varying perflubron doses during HFOV in a long-term study of the lung-protective effects of HFO-PLV.     

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.     

Albumin and furosemide therapy in hypoproteinemic patients with acute lung injury

OBJECTIVE: Hypoproteinemia, fluid retention, and weight gain are associated with development of acute lung injury and mortality in critically ill patients, without proof of cause and effect. We designed a clinical trial to determine whether diuresis and colloid replacement in hypoproteinemic patients with acute lung injury would improve pulmonary physiology. DESIGN: Prospective, randomized, double-blind, placebo-controlled trial. SETTING: All adult intensive care units from two university hospitals. PATIENTS: Thirty-seven mechanically-ventilated patients with acute lung injury and serum total protein 相似文献   

常频叠加高频振荡通气对肺损伤大鼠氧合及通气的影响

目的观察常频叠加高频振荡通气对急性肺损伤大鼠氧合和通气的影响。方法以15只Wistar大鼠为实验对象,给予机械通气,用生理盐水肺灌洗制作急性肺损伤大鼠模型,先后行常频机械通气(CMV参数:FiO2 100%、f 30 bpm、PEEP 6 cmH2O、I∶E 1∶2、MAP 12 cmH2O)、高频振荡通气(HFOV参数:FiO2 100%、f 11 Hz、Paw 12 cmH2O、Ti 33%)、常频叠加高频振荡通气(CMV+HFOV参数同前)各1 h,监测动脉血气。计算PaO2/FiO2、氧合指数(OI)、肺内血分流率(Qs/Qt)。结果损伤前、CMV、HFOV、CMV+HFOV各指标变化:(1)PaCO2分别为(41.04±3.94)mmHg、(100.5±28.73)mmHg、(82.06±22.87)mmHg及(54.01±19.32)mmHg,损伤后均显著高于损伤前(P<0.01);CMV+HFOV显著低于CMV、HFOV(P<0.01);CMV、HFOV两者差异无统计学意义(P>0.05)。(2)PaO2/FiO2分别为(467.9±47.71)mmHg、(105.3±25.39)mmHg、(131.2±67.72)mmHg、(216.3±76.84)mmHg,损伤后均显著低于损伤前(P<0.01);CMV+HFOV显著高于CMV、HFOV(P<0.01);CMV、HFOV两者差异无统计学意义(P>0.05)。(3)OI分别为1.88±0.30、8.84±2.15、6.16±3.19、4.60±1.71,损伤后均显著高于损伤前(P<0.01);CMV+HFOV、HFOV显著低于CMV(P<0.01);CMV+HFOV、HFOV两者差异无统计学意义(P>0.05)。(4)Qs/Qt分别为0.11±0.02、0.29±0.02、0.26±0.05及0.24±0.04,损伤后显著高于损伤前(P<0.01);各通气模式差异无统计学意义(P>0.05)。结论常频叠加高频振荡通气在促进肺损伤大鼠CO2排出及改善氧合方面优于单纯常频通气和单纯高频通气。     

Effects of exogenous surfactant supplementation and partial liquid ventilation on acute lung injury induced by wood smoke inhalation in newborn piglets

OBJECTIVE: To investigate the beneficial effects of exogenous surfactant supplementation (ESS) and partial liquid ventilation (PLV) in treating acute lung injury induced by wood smoke inhalation. DESIGN: A prospective, randomized, controlled, multigroup study. SETTING: An animal research laboratory at a medical center. SUBJECTS: Newborn piglets (n = 29; 1.80 +/- 0.06 kg) of either sex. INTERVENTIONS: Animals were ventilated with a tidal volume of 15 mL/kg, a rate of 30 breaths/min, a positive end-expiratory pressure of 5 cm H(2)O, and an Fio(2) of 1.0. After the induction of acute lung injury by wood smoke inhalation, animals were randomly assigned to receive either conventional mechanical ventilation (CMV) or PLV with or without ESS pretreatment. Animals were grouped as CMV, ESS-CMV, PLV, and ESS-PLV. MEASUREMENTS AND MAIN RESULTS: Arterial blood gases, cardiovascular hemodynamics, dynamic lung compliance, and total lung injury scores were measured. After smoke inhalation, all four groups displayed similar high arterial carboxyhemoglobin levels, low Pao(2) (<150 mm Hg), and low dynamic lung compliance (<66% of its baseline). In the CMV group, these deleterious conditions remained during the 4-hr observation period, and severe lung injury was noted histologically. All treatment groups demonstrated a significant increase in Pao(2) compared with the CMV group. In addition, both the PLV and ESS-PLV groups displayed significant improvements in dynamic lung compliance and in their histologic outcomes. Nevertheless, none of the variables measured in the PLV group differed from those measured in the ESS-PLV group. CONCLUSIONS: In a newborn piglet model of smoke inhalation injury, PLV or ESS improved oxygenation. PLV compared favorably with ESS in its greater improvements in lung compliance and lung pathology. However, the combined therapy of ESS and PLV was not clearly superior to PLV alone during the observation period.     

Benefits of early tracheostomy in severely burned children

OBJECTIVE: The role of tracheostomy in burn patients is controversial. Previous studies, primarily in adults, suggested that severely burned patients with tracheostomies have a higher incidence of tracheostomy site infections, mortality, and pneumonia. The purpose of this study is to determine the safety and efficacy of early tracheostomy in severely burned children. DESIGN: Case series study analyzing mechanical ventilation and sedation requirements before and 24 hrs after tracheostomy. SETTING: Regional pediatric burn center. PATIENTS: All children admitted to a regional pediatric burn center requiring tracheostomy from March 1, 1998, to October 1, 2001. METHODS: Data were recorded on patients' demographics, extent of burn, presence of inhalation injury, and mortality. Mechanical ventilation variables measured pretracheostomy (pre) and posttracheostomy (post) and included mode of ventilation, ventilator settings, peak inspiratory pressures, and arterial blood gases (Pao2, Paco2, pH, and oxygen saturation). Calculated variables included compliance, Pao2:Fio2 ratio, and minute ventilation. Tracheostomy-related variables recorded included the interval to tracheostomy insertion, the duration of tracheostomy, and tracheostomy complications. MAIN RESULTS: A total of 38 patients (with a mean age of 4.7 +/- 0.6 yrs and a mean total body surface area involvement of 54% +/- 4%, 63% with inhalation injury) underwent tracheostomy a mean of 3.9 +/- 0.7 days after admission. Overall mortality was 21%. There were no tracheostomy site infections, tracheostomy-related deaths, or tracheal stenoses in survivors. Peak inspiratory pressures were lower after tracheostomy (30.4 +/- 1.4 [pre] vs. 27.6 +/- 1.5 cm H2O [post]; p <.05), ventilatory volumes were higher (190 +/- 22 mL [pre] vs. 225.5 +/- 25 [post]; p <.05), compliance improved (10.5 +/- 1.4 [pre] vs. 15.1 +/- 2.3 mL/cm H2O [post]; p <.05), and the Pao2:Fio2 ratio improved (300.6 +/- 20 [pre] vs. 348.6 +/- 16 [post]). There was no difference in oxygenation, ventilation, minute ventilation, or pH after tracheostomy. CONCLUSIONS: Early tracheostomy in severely burned children is safe and effective. It provides a secure airway and may result in improvement in ventilator management for these children.     

高频振荡通气在新生儿呼吸窘迫综合征治疗中的应用

目的 探讨高频振荡通气(HFOV)治疗新生儿呼吸窘迫综合征(NRDS)的疗效及安全性.方法 对NRDS 64例,随机分为常频机械通气(CMV)30例和高频振荡通气(HFOV)34例,比较两组患儿治疗前后的血气分析、吸入氧浓度(FiO2)、氧合指数(OI)及并发症等.结果 HFOV组患儿吸入氧分数明显低于CMV组,PaCO2及氧合指数迅速下降,pH及PaO2明显上升,HFOV组发生肺气漏及慢性肺部疾病(CLD)等并发症低于CMV组(P<0.05).结论 HFOV用于治疗新生儿呼吸窘迫综合征,是一种疗效肯定、安全性好的新型机械通气方法.     

Partial liquid ventilation in severely surfactant-depleted, spontaneously breathing rabbits supported by proportional assist ventilation

OBJECTIVE: We hypothesized that partial liquid ventilation (PLV) would improve oxygenation in nonparalyzed, surfactant-deficient rabbits breathing spontaneously while supported by proportional assist ventilation (PAV). This ventilation mode compensates for low pulmonary compliance and high resistance and thereby facilitates spontaneous breathing. DESIGN: Randomized trial. SETTING: University animal research facility. SUBJECTS: Twenty-six anesthetized New Zealand white rabbits weighing 2592 +/- 237g (mean +/- sd). INTERVENTIONS: After pulmonary lavage (target Pao2 <100 mm Hg on mechanical ventilation with 6 cm H2O of positive end-expiratory pressure [PEEP] and an Fio2 of 1.0), rabbits were randomized to PAV (PEEP of 8 cm H2O) with or without PLV. PLV rabbits received 25 mL/kg of perfluorocarbon by intratracheal infusion (1 mL/kg/min). Pao2, Paco2, tidal volume, respiratory rate, minute ventilation, mean airway pressure, arterial blood pressure, heart rate, pulmonary compliance, and airway resistance were measured. Evaporated perfluorocarbon was refilled every 30 mins in PLV animals. After 5 hrs, animals were killed and lungs were removed. Lung injury was evaluated using a histologic score. MAIN RESULTS: Pao2 and compliance were significantly higher in PLV rabbits compared with controls (p <.05, analysis of variance for repeated measures). All other parameters were similar in both groups. CONCLUSIONS: PLV improved oxygenation and pulmonary compliance in spontaneously breathing, severely surfactant-depleted rabbits supported by PAV. The severity of lung injury by histology was unaffected.     

Recruitment maneuver: does it promote bacterial translocation?

OBJECTIVE: High peak airway opening pressures (Pao) are used routinely during recruitment maneuvers to open collapsed lung units. High peak Pao, however, can cause lung injury as evidenced by translocation of intratracheally inoculated bacteria. In this study we explored whether recruitment maneuvers that used high Pao could cause translocation of the intratracheally inoculated from the alveoli into the systemic circulation. DESIGN: Prospective, randomized, animal study. SETTING: Experimental animal care laboratory. SUBJECTS: Eighteen male Sprague Dawley rats.INTERVENTIONS Rats were anesthetized, tracheostomized, and ventilated with 14 cm H2O peak Pao and 0 cm H2O positive end-expiratory pressure (PEEP) in pressure-controlled ventilation (frequency, 30 bpm; inspiratory/expiratory ratio, 1:2; Fio, 1). Intratracheal inoculation of 500 microL of saline containing 1 x 10 colony forming units/mL was performed before randomization into three groups (n = 6 in each): a low-pressure group (14 cm H2O peak Pao, 0 cm H2O PEEP), a high-pressure group (45 cm H2O peak Pao, 0 cm H2O PEEP), and a recruitment maneuver group (14 cm H2O peak Pao, 0 cm H2O PEEP, and a recruitment maneuver sustained inflation of 45 cm H2O continuous positive airway pressure for 30 secs every 15 mins). Blood samples for blood gas analysis were obtained before intratracheal instillation of bacteria and at the end of the experimental protocol (2 hrs). Blood cultures were obtained before and after bacterial instillation at 30-min intervals during the experiment. Blood samples were cultured directly in sheep blood, MacConkey, and Iso-Sensitest agars and were observed on the second day. Bacteremia was defined as the presence of one or more colonies of in 1 mL of blood. MEASUREMENTS AND MAIN RESULTS: The blood cultures were positive for in only six rats in the high-pressure group and remained negative throughout the study period in the low-pressure and recruitment maneuver groups. Oxygenation deteriorated in all groups after intratracheal instillation of bacteria. In the high-pressure group, oxygenation decreased from 417 +/- 67 mm Hg to 79 +/- 20 mm Hg ( p=.004), whereas in the low-pressure and recruitment maneuver groups PaO2 decreased from 410 +/- 98 mm Hg and 383 +/- 78 mm Hg to 287 +/- 105 mm Hg ( p=.031) and 249 +/- 59 mm Hg (p =.11), respectively. CONCLUSION: Intermittent recruitment maneuvers applied as a sustained inflation superimposed on low-pressure ventilation with 0 cm H2O PEEP did not cause translocation of intratracheally inoculated.     

Extravascular lung water determined with single transpulmonary thermodilution correlates with the severity of sepsis-induced acute lung injury

OBJECTIVE: To find out if the extravascular lung water index (EVLWI) and the derived permeability indexes determined by the single transpulmonary thermodilution technique are associated with markers of acute lung injury in human septic shock. DESIGN: Prospective, observational study. SETTING: Mixed intensive care unit of a 900-bed university hospital. PATIENTS: Thirty-eight consecutive adult patients with septic shock and acute lung injury. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The variables were assessed over a 72-hr period and included hemodynamics, EVLWI, and pulmonary vascular permeability indexes determined with the single indicator transpulmonary thermodilution technique, lung compliance, oxygenation ratio (Pao2/Fio2), lung injury score, cell counts, and the plasma concentration of endothelin-1. At day 1, EVLWI was elevated (>or=7 mL/kg) in 28 (74%) patients and correlated with lung compliance (r=-.48, p=.002), Pao2/Fio2 (r=-.50, p=.001), lung injury score (r=.46, p=.004), roentgenogram quadrants (r=.39, p=.02), and platelet count (r=-.43, p=.007). At day 3, EVLWI correlated with compliance (r=-.51, p=.002), Pao2/Fio2 (r=-.49, p = .006), and lung injury score (r=.53, p=.003). At day 3, EVLWI and pulmonary vascular permeability indexes were higher in nonsurvivors (p<.05). The plasma concentration of endothelin-1 (mean+/-sd) was significantly higher in patients with elevated EVLWI (>or=7 mL/kg) (3.85+/-1.40 vs. 2.07+/-0.38 pg/mL, respectively). Twenty-two (59%) patients died before day 28. CONCLUSIONS: In human septic shock, EVLWI demonstrated moderate correlation with markers of acute lung injury, such as lung compliance, oxygenation ratio, roentgenogram quadrants, and lung injury score. In nonsurvivors, EVLWI and permeability indexes were significantly increased at day 3. Thus, EVLWI might be of value as an indicator of prognosis and severity of sepsis-induced acute lung injury.     

High-frequency oscillatory ventilation and partial liquid ventilation after acute lung injury in premature lambs with respiratory distress syndrome

OBJECTIVE: Conventional mechanical ventilatory support (CV) contributes to lung injury in premature lambs with respiratory distress syndrome, a disease that is characterized by progressive deterioration of gas exchange and increased lung inflammation. Lung recruitment strategies, such as high-frequency oscillatory ventilation (HFOV) and partial liquid ventilation (PLV), improve gas exchange and attenuate lung inflammation when instituted immediately after birth. However, whether these recruitment strategies are effective as rescue treatment after established lung injury is unknown. To determine the separate and combined effects of HFOV and PLV when initiated after the establishment of acute lung injury in severe respiratory distress syndrome, we studied the effects of these strategies on gas exchange and histologic signs of acute lung injury in premature lambs. DESIGN: Animals were intubated, treated with surfactant and ventilated with 1.00 FIO2 for 4 hrs. After 2 hrs, animals were either continued on CV (controls) or treated with one of three strategies: HFOV; CV + PLV; or HFOV + PLV. The response to low-dose inhaled nitric oxide (5 ppm) was measured in each group at the end of the study. SETTING: An animal laboratory affiliated with University of Colorado School of Medicine. SUBJECTS: A total of 20 premature lambs at 115-118 days of gestation (term = 147 days). MEASUREMENTS AND MAIN RESULTS: In comparison with control animals, each of the rescue therapies improved PaO2 after 1 hr of treatment. The HFOV and HFOV + PLV groups had higher PaO2 than CV + PLV or CV alone (p < .05). Mean airway pressure (Paw) was lower in the PLV groups during CV or HFOV compared with their controls (p < .05). Inhaled NO improved PaO2 in all groups; however, the increase in PaO2 was greatest in the HFOV + PLV group (p < .05). Histologic examination and myeloperoxidase assay were not different between groups. CONCLUSION: We conclude that each lung recruitment strategy improved oxygenation in premature lambs with established lung injury.     

Combining high-frequency oscillatory ventilation and recruitment maneuvers in adults with early acute respiratory distress syndrome: the Treatment with Oscillation and an Open Lung Strategy (TOOLS) Trial pilot study

OBJECTIVE: To determine the safety, feasibility, and lung-recruitment efficacy of an explicit ventilation protocol combining high-frequency oscillatory ventilation and recruitment maneuvers. DESIGN: Prospective, multiple-center, single-intervention pilot study. SETTING: Four university-affiliated intensive care units. PATIENTS: Twenty-five patients with early acute respiratory distress syndrome and severe oxygenation failure. INTERVENTIONS: Patients were transitioned from standardized conventional ventilation to high-frequency oscillatory ventilation beginning with an initial cycle of up to three sustained inflation recruitment maneuvers (40 cm H2O x 40 secs), followed by a decremental titration of Fio2 and then mean airway pressure. Recruitment maneuvers were repeated for hypoxemia and routinely at least twice daily if the Fio2 was >0.4. A specific protocol was used for weaning high-frequency oscillatory ventilation, for transitioning to conventional ventilation, and for judging intolerance of conventional ventilation whereby patients should be put back on high-frequency oscillatory ventilation. MEASUREMENTS AND MAIN RESULTS: Patients (median [interquartile range] Acute Physiology and Chronic Health Evaluation II, 24 [19-32]; age, 50 [41-64]) were enrolled after 13 (range, 6-51) hrs of conventional ventilation. Following the initial cycle of recruitment, the mean (+/-sd) Pao2/Fio2 increased significantly compared with standardized conventional ventilation (200 +/- 117 vs. 92 +/- 36 mm Hg, p < .001). After a mean of 12 hrs of high-frequency oscillatory ventilation, the mean Fio2 was significantly reduced compared with prestudy levels (0.5 +/- 0.2 vs. 0.9 +/- 0.1, p < .001). A median of seven (four to 11) recruitment maneuvers was performed per patient over the study period, with only eight of 244 (3.3%) being aborted. Six of 19 patients transitioned to conventional ventilation (32%) were deemed intolerant and were switched back to high-frequency oscillatory ventilation. Protocol adherence was excellent with documented rates >90%. CONCLUSIONS: The combination of high-frequency oscillatory ventilation and recruitment maneuvers resulted in rapid and sustained improvement in oxygenation, likely through lung recruitment. This explicit high-frequency oscillatory ventilation protocol appears well tolerated, feasible, and physiologically sound.     

Open lung ventilation improves gas exchange and attenuates secondary lung injury in a piglet model of meconium aspiration

OBJECTIVE: Previous studies failed to show clear benefits of high-frequency ventilation compared with conventional positive pressure ventilation (PPV(CON)) in experimental meconium aspiration syndrome. However, none of these studies applied an open lung ventilation strategy (OLC), which aims to reduce intrapulmonary shunt due to alveolar collapse. We hypothesized that, if combined with an open lung strategy, both high-frequency oscillatory ventilation (HFOV(OLC)) and positive pressure ventilation (PPV(OLC)) would improve gas exchange and attenuate ventilator-induced lung injury in experimental meconium aspiration syndrome. DESIGN: Prospective, randomized animal study. SETTING: Research laboratory of a large university. SUBJECTS: Forty-two newborn piglets. INTERVENTIONS: Thirty minutes after intratracheal meconium instillation, 36 newborn piglets were assigned to one of three ventilation groups-PPV(OLC), HFOV(OLC), or PPV(CON)-and ventilated for 5 hrs. In both OLC groups, collapsed alveoli were actively recruited and thereafter stabilized using the lowest possible airway pressures. During PPV(CON), ventilator settings were adjusted to prevent critical hypoxia (Pao2 <60 torr [8 kPa]). Six animals served as saline controls. MEASUREMENTS AND MAIN RESULTS: Compared with the PPV(CON) group, arterial oxygenation and lung mechanics were superior in both OLC groups and the saline controls. Analysis of the bronchoalveolar lavage fluid obtained after 5 hrs of ventilation showed increased myeloperoxidase activity in the PPV(CON) group compared with both OLC groups and saline controls. Alveolar protein influx was not different between the groups. Histologic analysis revealed a higher lung injury score in the PPV(CON) group compared with the PPV(OLC) and the HFOV(OLC) groups. CONCLUSIONS: Application of the OLC during PPV and HFOV is feasible in experimental meconium aspiration syndrome and results in superior oxygenation and less ventilator-induced lung injury compared with PPV(CON).     

常规机械通气与高频振荡通气在胎粪吸入综合征中的应用

【目的】评价常规机械通气（CMV）与高频振荡通气（HFOV）治疗新生儿重症胎粪吸入综合征（MAS）的疗效。【方法】对本院2008年9月至2011年6月83例重症MAS新生儿予CMV或HFOV治疗。观察比较CMV与HFOV治疗前后肺功能变化及病情转归。【结果】CMV治疗组与HFOV治疗组动脉氧分压（Pa02）分别由治疗前的（47．95土14．44）mmHg、（62．16±23．03）mmHg上升为（82．84±19．82）mmHg、（81．69士23．84）mmHg（P〈0．05）。氧合指数（Pa02／Fi02）分别由治疗前的（218．30±70．98）（173．59±74．44）增加到（275．52±68．40）、（237．02±89．22）（P〈0．05）;动脉二氧化碳分压（PaC02）分剐由（51．42±12．43）mmHg、（48．95±12．11）mmHg下降到（40．11±7．87）mmHg、（41．89土12．69）mmHg（P〈0．05）。在颅内出血并发症中CMV治疗组高于HFOV治疗组（P〈0．05）。【结论】CMV与HFOV用于新生儿重症MAS疗效好,均能较快改善肺氧合功能,改善预后,HFOV在重症MAS应用中可作为CMV应用失败的补救方法,并发症较低。