Effects of High-Frequency Oscillatory Ventilation on Oleic Acid-Induced Lung Injury in Sheep

High-frequency oscillatory ventilation (HFOV) is a possible mechanical method for open lung strategies. The aim of this study was to examine whether HFOV has a beneficial effect on oleic acid-induced lung injury, with emphasis on changes in extravascular lung water. Thirteen anesthetized sheep prepared with a lung lymph fistula and vascular catheters for monitoring were randomly allocated to two experimental groups. In experiment 1, sheep (n = 6) were ventilated using conventional mechanical ventilation [CMV; 10 ml/kg of tidal volume, 70% oxygen, and positive end-expiratory pressure (PEEP) of 6 cmH(2)O after oleic acid administration (0.08 ml/kg)]. In experiment 2, sheep (n=7) were ventilated using HFOV (frequency=15 Hz, stroke volume=120 ml, mean airway pressure=15 cmH(2)O) after administration of the same dose of oleic acid as in experiment 1. Observation was continued for 4 h after oleic acid administration, then bronchoalveolar lavage (BAL) was performed and the lung wet-to-dry weight ratio was determined. Compared with CMV, HFOV significantly improved the deteriorated oxygenation during the late phase (2-4 h) of oleic acid-induced lung injury without any deterioration effects on pulmonary or systemic hemodynamics. HFOV showed significantly reduced lung lymph protein clearance, which paralleled significant decreases in wet-to-dry ratios and neutrophil counts in BAL fluid in the HFOV group. These findings suggest that HFOV could contribute to decreased lung lymph filtration in pulmonary microcirculation and improved oxygenation following oleic acid-induced lung injury in sheep.     

Applications of Airway Pressure Release Ventilation

The purpose of this review is to cover the definition and mechanism of airway pressure release ventilation, its advantages, and applications in acute lung injury.     

High-Frequency Oscillatory Ventilation in Pediatric Acute Hypoxemic Respiratory Failure: Disease-Specific Morbidity Survival Analysis

Background

Multiple ventilatory strategies for acute hypoxemic respiratory failure (AHRF) in children have been advocated, including high-frequency oscillatory ventilation (HFOV). Despite the frequent deployment of HFOV, randomized controlled trials remain elusive and currently there are no pediatric trials looking at its use. Our longitudinal study analyzed the predictive clinical outcome of HFOV in pediatric AHRF given disease-specific morbidity.

Methods

A retrospective 8-year review on pediatric intensive care unit admissions with AHRF ventilated by HFOV was performed. Primary outcomes included survival, morbidity, length of stay (LOS), and factors associated with survival or mortality.

Results

A total of 102 patients underwent HFOV with a 66?% overall survival rate. Survivors had a greater LOS than nonsurvivors (p?=?0.001). Mortality odds ratio (OR) for patients without bronchiolitis was 8.19 (CI?=?1.02, 65.43), and without pneumonia it was 3.07 (CI?=?1.12, 8.39). A lower oxygenation index (OI) after HFOV commencement and at subsequent time points analyzed predicted survival. After 24?h, mortality was associated with an OI?>?35 [OR?=?31.11 (CI?=?3.25, 297.98)]. Sepsis-related mortality was associated with a higher baseline FiO₂ (0.88 vs. 0.65), higher OI (42 vs. 22), and augmented metabolic acidosis (pH of 7.25 vs. 7.32) evaluated 4?h on HFOV (p?<?0.05).

Conclusion

High-frequency oscillatory ventilation may be safely utilized. It has a 66?% overall survival rate in pediatric AHRF of various etiologies. Patients with morbidity limited to the respiratory system and optimized oxygenation indices are most likely to survive on HFOV.     

双水平正压通气治疗急性心源性肺水肿

目的 探讨应用双水平无创正压机械通气技术治疗急性心源性肺水肿（ACPE）的临床价值。方法 将2004年7月-2006年5月收治的44例急性心源性肺水肿病人随机分为BiPAP组和面罩吸氧组。BiPAP组在常规药物治疗基础上，经鼻面罩连接BiPAP呼吸机，吸气末压力（IPAP）8cmH2O～15cmH2O、呼气末压力（EPAP）2cmH2O～5cmH2O，吸氧浓度28％～35％；面罩吸氧组在常规药物治疗的基础上单纯给予Venturi面罩吸氧。监测病人心率、血压、呼吸、指端血氧饱和度、动脉血气分析和临床变化。结果 BiPAP组经无创机械通气后所有病人呼吸频率减慢，心率下降，呼吸困难缓解，治疗总有效率为100．0％。对血压无明显影响。呼吸困难开始缓解时间40min（10min～100min），明显短于对照组的150min（50min～240min）（P〈0．01）。对照组在相应时间治疗有效率仅为64．7％。结论 充分使用药物治疗急性心源性肺水肿基础上，合用BiPAP治疗可使肺水肿和心功能迅速改善，减少气管插管率。     

无创气道正压通气在心力衰竭中的应用

无创气道正压通气能明显缓解心源性肺水肿患者的呼吸困难 ,提高血氧分压 ,降低气管插管率和住院病死率 ;显著提高心力衰竭合并睡眠呼吸暂停患者的睡眠质量 ,减轻气道阻塞 ,降低心脏负荷 ,增加心脏射血 ,改善心功能。     

Determining the Optimal Systolic Blood Pressure for Hypertensive Patients: A Network Meta-analysis

Background

There is clinical trial evidence that lowering systolic blood pressure (SBP) to < 120 mm Hg is beneficial, and this has influenced the latest American guideline on hypertension. We therefore used network meta-analysis to study the association between SBP and cardiovascular outcomes.

Termination of Recurrent Ventricular Tachycardia by Continuous Positive Airway Pressure Ventilation

We report a case of hypertrophic cardiomyopathy with recurrent ventricular tachycardia that resolved after initiating continuous positive airway pressure therapy.     

Exercise Oscillatory Ventilation in Hypertrophic Cardiomyopathy

To assess the prevalence and clinical correlates of exercise oscillatory ventilation (EOV) in patients with hypertrophic cardiomyopathy (HCM). Retrospective single-center study. Thirty-six consecutive HCM patients who underwent cardiopulmonary exercise testing. Two patients (5.6%) had EOV. Both patients with peak oxygen consumption (VO₂) less than or equal to 9.1 ml/kg/min had EOV. Left atrial size was greater in patients with EOV. Of the 2 patients in the study population with an abnormal blood pressure response to exercise, 1 had EOV. Both patients with New York Heart Association Class 3 heart failure had EOV. This is the first report of EOV in HCM. EOV is uncommon in patients with HCM. EOV appears to be a marker of disease severity as evidenced by overt heart failure, left atrial enlargement, and low peak VO₂.     

A Mathematical Model of Mean Airway Pressure Based Upon Positive End-Expiratory Pressure, I:E Ratio, and Plateau Pressure

A mathematical model of mean airway pressure (P _mean) has been derived which is based upon positive end-expiratory pressure (P _peep) and I:E ratio (I:E). Plateau pressure (P _PL) is also utilized: $$ P_{\rm mean}/P_{\rm PL} = [(I{:}E) + {\bf R}]/[(I{:}E) + 1] $$ where R is defined as: R = P _peep/P _PL. Based upon this model, it can be shown that (1) increasing I:E ratio will increase P _mean/P _PL in a self-limiting logarithmic manner; (2) P _mean/P _PL is a linear function with respect to R; (3) increases in R are associated with a diminished effect of I:E ratio on P _mean/P _PL; (4) similarly, increases in I:E ratio are associated with a diminished effect of R on P _mean/P _PL; (5) overall, changes in P _mean/P _PL will consistently be effected more by changes in R than by changes in I:E ratio. This model illustrates the interrelationship between plateau pressure, PEEP, and I:E ratio as they affect mean airway pressure. Furthermore, it appears to be useful in explaining the clinically reported discrepancies regarding the efficacy of inverse ratio ventilation (IRV), especially when simultaneously applied with varying levels of PEEP. In addition, for a given plateau pressure, it is also possible to mathematically optimize PEEP and I:E ratio combinations so as to avoid excessive amounts of either.     

Enhancement of Cardiac Performance by Bilevel Positive Airway Pressure Ventilation in Heart Failure

BackgroundRecent studies have reported the clinical usefulness of positive airway pressure ventilation therapy with various kinds of pressure support compared with simple continuous positive airway pressure (CPAP) for heart failure patients. However, the mechanism of the favorable effect of CPAP with pressure support can not be explained simply from the mechanical aspect and remains to be elucidated.Methods and ResultsIn 18 stable chronic heart failure patients, we performed stepwise CPAP (4, 8, 12 cm H₂O) while the cardiac output and intracardiac pressures were continuously monitored, and we compared the effects of 4 cm H₂O CPAP with those of 4 cm H₂O CPAP plus 5 cm H₂O pressure support. Stepwise CPAP decreased cardiac index significantly in patients with pulmonary arterial wedge pressure (PAWP) <12 mm Hg (n = 10), but not in those with PAWP ≥12 mm Hg (n = 8). Ventilation with CPAP plus pressure support increased cardiac index slightly but significantly from 2.2 ± 0.7 to 2.3 ± 0.7 L min^?1 m^?2 (P = .001) compared with CPAP alone, regardless of basal filling condition or cardiac index.ConclusionsOur results suggest that CPAP plus pressure support is more effective than simple CPAP in heart failure patients and that the enhancement might be induced by neural changes and not simply by alteration of the preload level.     

Mean Airway Pressure and Response to Inhaled Nitric Oxide in Neonatal and Pediatric Patients

Inhaled nitric oxide (iNO) can improve oxygenation and ventilation–perfusion (V/Q) matching by reduction of shunt (Qs/Qt) in patients with hypoxemic lung disease. Because the improvement in V/Q matching must occur by redistribution of pulmonary blood flow, and because high airway pressure (Paw) increases physiologic dead space (Vd/Vt), we hypothesized that high Paw may limit the improvement in V/Q matching during iNO treatment. iNO 0–50 ppm was administered during mechanical ventilation. Mechanical ventilator settings were at the discretion of the attending physician. Qs/Qt and Vd/Vt were derived from a tripartite lung model with correction for shunt-induced dead space. Data from 62 patients during 153 trials were analyzed for effects of Paw and iNO on Qs/Qt and Vd/Vt. Baseline Qs/Qt was slightly increased at Paw 16–23 cmH₂O (p < 0.05), while Vd/Vt increased progressively with higher Paw (p < 0.002). Therapy with iNO significantly reduced Qs/Qt (p < 0.001) at all levels of mean Paw, reaching a maximum reduction at 16–23 cmH₂O (p < 0.05), such that Qs/Qt during iNO treatment was similar at all levels of Paw. During iNO treatment, a reduction in Vd/Vt occurred only at Paw of 8–15 cmH₂O (p < 0.05), and the positive relationship between Vd/Vt and Paw was maintained. These differential effects on Qs/Qt and Vd/Vt suggest that both high and low Paw may limit improvement in gas exchange with iNO. Analysis of gas exchange using this corrected tripartite lung model may help optimize ventilatory strategies during iNO therapy.     

High-frequency Percussive Ventilation for Airway Clearance in Cystic Fibrosis: A Brief Report

Exacerbations of cystic fibrosis (CF) lung disease are characterized by increased inspissation of abnormally viscid pulmonary secretions with resultant plugging of small airways, worsened ventilation/perfusion mismatch, and increased physiological deadspace. In this circumstance, hypoxic respiratory failure necessitating mechanical ventilation can be life-threatening. We present such a case of CF lung disease poorly responsive to conventional mechanical ventilatory strategies, in which high-frequency percussive ventilation (HFPV) using volumetric diffusive respiration mobilized copious amounts of inspissated pulmonary secretions and improved refractory hypoxia. Subsequent transient hypercarbia necessitated titrating ventilator parameters to return the PaCO₂ to baseline; the voluminous clearance of secretions and improvement in oxygenation were sustained. HFPV appears unique in its ability to function as a methodological continuum from noninvasive percussion to invasive percussive ventilation for airway clearance, a fundamental tenet of the CF treatment paradigm.     

无创双水平正压通气治疗重症支气管哮喘96例临床分析

目的探讨无创双水平正压通气(BiPAP)在重症支气管哮喘治疗中的应用价值。方法观察96例重症支气管哮喘患者(无创通气组)在传统内科治疗基础上运用BiPAP治疗2h后的显效率,并与单用传统内科方法治疗的61例患者(对照组)进行比较。结果治疗后,两组患者的显效率间差异有统计学意义(P<0.05)。结论Bi-PAP是治疗重症支气管哮喘的有效方法,可有效缓解患者的症状,改善通气功能。     

无创性双水平气道正压通气治疗老年人心功能不全的探讨

目的 :本文观察BiPAP通气治疗 13例心功能不全低氧血症的老年患者的疗效。方法 :13例住院心衰患者均在心衰发作血氧饱和度低于 90 %后 ,使用BiPAP辅助通气。结果 :13例患者在BiPAP辅助呼吸后血氧饱和度均很快上升 ,由平均值 81.92± 3.2 9%增至 97.6 2± 1.2 1% ,血压均无明显下降。结论 :BiPAP机械通气方式可治疗心脏病心功能不全低氧血症的老年患者 ,优点为无创性、使用方便安全、疗效迅速可靠、并发症少。因此 ,应将BiPAP辅助呼吸列为老年人心功能不全低氧血症的常规治疗措施之一     

BiPAP呼吸机治疗急性呼吸衰竭疗效观察

目的探讨（鼻）面罩双水平气道正压通气（BiPAP）治疗不同病因急性呼吸衰竭的效果。方法选择60例不同病因急性呼吸哀竭患者应用BiPAP呼吸机辅助通气治疗,比较治疗前及治疗1h后患者的血气分析、心率和呼吸。结果比较BiPAP呼吸机治疗前、后1h的血气分析、心率和呼吸有统计学意义（P〈0．05）。结论BiPAP呼吸机治疗不同病因急性呼吸衰竭疗效显著。     

经鼻(面)罩双相气道正压通气治疗急性心源性肺水肿32例疗效观察

急性心源性肺水肿是临床常见的急症 ,对大多数患者传统的强心、利尿、扩血管等治疗能改善病情 ,但对部分难治性急性心源性肺水肿患者 ,传统的方法常难于奏效。我们观察 3年半中所收治的 6 0例急性心源性肺水肿患者 ,其中 32例应用双相气道正压通气(BiPAP)治疗 ,取得了满意的疗效 ,报告如下。资料与方法对象　急性心源性肺水肿患者 6 0例 (男 34,女2 6 ) ,年龄 19～ 74 (5 2 .4± 2 0 .1)岁。心功能NYHA评分均为Ⅳ级 ,其中冠心病 2 3例 (陈旧性心肌梗死15例 ,急性心肌梗死 8例 ) ,风湿性心脏病 11例 ,扩张性心肌病 9例 ,高血压心脏病 8例…     

BiPAP通气联合可拉明治疗COPD并肺性脑病的临床研究

目的 :研究慢性阻塞性肺病 (COPD)患者合并肺性脑病时进行无创双水平正压 (BiPAP)通气联合可拉明治疗的效果。方法 :4 0例COPD合并肺性脑病患者分为BiPAP组和BiPAP联用可拉明组 ,观察两组的治疗效果。结果 :两组患者治疗效果存在显著差异 ,与BiPAP组比较 ,联用组意识障碍恢复快 ,治愈率高。结论 :对于COPD合并自主呼吸较稳定的肺性脑病患者 ,BiPAP通气联用可拉明是一种有效的治疗方法。     

Non-Invasive Mechanical Ventilation Versus Continuous Positive Airway Pressure Relating to Cardiogenic Pulmonary Edema in an Intensive Care Unit

BackgroundTo compare the application of non-invasive ventilation (NIV) versus continuous positive airway pressure (CPAP) in the treatment of patients with cardiogenic pulmonary edema (CPE) admitted to an intensive care unit (ICU).MethodsIn a prospective, randomized, controlled study performed in an ICU, patients with CPE were assigned to NIV (n=56) or CPAP (n=54). Primary outcome was intubation rate. Secondary outcomes included duration of ventilation, length of ICU and hospital stay, improvement of gas exchange, complications, ICU and hospital mortality, and 28-day mortality. The outcomes were analyzed in hypercapnic patients (PaCO₂ > 45 mmHg) with no underlying chronic lung disease.ResultsBoth devices led to similar clinical and gas exchange improvement; however, in the first 60 min of treatment a higher PaO₂/FiO₂ ratio was observed in the NIV group (205±112 in NIV vs. 150±84 in CPAP, P=.02). The rate of intubation was similar in both groups (9% in NIV vs. 9% in CPAP, P=1.0). There were no differences in duration of ventilation, ICU and length of hospital stay. There were no significant differences in ICU, hospital and 28-d mortality between groups. In the hypercapnic group, there were no differences between NIV and CPAP.ConclusionsEither NIV or CPAP are recommended in patients with CPE in the ICU. Outcomes in the hypercapnic group with no chronic lung disease were similar using NIV or CPAP.