Serial measurement of pulmonary mechanics assists in weaning from extracorporeal membrane oxygenation in neonates with respiratory failure

Extracorporeal membrane oxygenation (ECMO) is a highly invasive therapy for intractable neonatal respiratory failure, and serious complications may occur with increasing duration of bypass. Weaning from bypass is empirical at present. Thus, there is a need to accurately predict when infants can be successfully decannulated. We hypothesized that pulmonary mechanics would reflect lung recovery and, therefore, predict successful weaning from ECMO. We measured pulmonary mechanics daily in 22 neonates, at gestational age of 37.8 +/- 0.6 weeks (SE) requiring ECMO for severe respiratory failure (oxygen index 66 +/- 6). Pulmonary resistance (Rpul), dynamic compliance (Cdyn), and tidal volume (VT) were measured. Rpul did not predict lung recovery. Cdyn within 24 hours of starting ECMO was 0.3 +/- 0.04 ml/cm H2O. Cdyn within 24 hours of weaning from ECMO was 1.2 +/- 0.09 ml/cm H2O (p less than 0.001). All 22 infants had Cdyn greater than 0.6 ml/cm H2O at the time of decannulation, but four infants (20 percent) with Cdyn less than 0.6 ml/cm H2O could not be weaned from ECMO within 20 hours (p less than 0.01). Thus, a minimum Cdyn of 0.6 ml/cm H2O is associated with successful weaning from ECMO. Cdyn of 0.8 ml/cm H2O provided better overall discrimination between those who could be successfully weaned from ECMO. We conclude that serial measurement of dynamic pulmonary compliance predicts successful weaning from ECMO.     

双侧肺同期手术中不同体位和单肺通气对病人呼吸力学的影响

目的观察双侧肺同期手术中体位改变和单肺通气时对病人呼吸力学的影响。方法选取我院2007年6月至2010年12月双侧肺同期手术病人142例,经气道旁路采用旁气流通气连续监测病人PIP、Pplat、Raw、Cdyn等呼吸力学指标,监测SpO2、PETCO2指标,分别在双腔支气管导管定位后,平卧改侧卧,单肺通气及改换通气方式后10 min抽取动脉血进行血气分析。结果病人双肺通气改变体位和单肺通气后,病人PIP、Pplat、Raw升高,Cdyn减少,PH值降低,PETCO2、PaCO2升高、SpO2、PaO2降低(P<0.05);双肺通气改换通气方式后,病人PIP、Pplat、Raw降低,Cdyn增加,PH值降低,PaO2、SpO2、PaCO2、PETCO2升高(P<0.05)。单肺通气38例病人改换通气方式后,病人PIP、Pplat、Raw降低,Cdyn增加,PH值、PaO2、SpO2升高,PaCO2、PETCO2降低(P<0.05)。结论双侧肺同期手术麻醉中不同体位和单肺通气对病人的呼吸力学影响较大,改换通气方式可改变病人呼吸力学指标。     

Predictive value of measurements of respiratory mechanics in preterm infants with HMD

Conventional methods for measuring respiratory mechanics model the respiratory system as a single compartment. The interrupter technique allows the respiratory system to be considered as a two compartment model with “flow resistance” of the conducting airways (Pinit), calculated from the initial pressure drop (Pinit), considered separately from Pdiff, as a measure of the viscoelastic properties of the lung and chest wall and any pendelluft present. The pulmonary mechanics of 50 intubated and mechanically ventilated preterm infants (≤1500 g) were studied during the first week of life using conventional methods and the interrupter technique to determine whether it was possible to predict which infants would develop bronchopulmonary dysplasia (BPD). Pulmonary mechanics of preterm infants intubated and ventilated for apnea of prematurity were also studied. The dynamic compliance of the respiratory system (C_rsdyn) was significantly lower on day 1 (P<0.001) and during the first week of life in the infants with HMD who developed BPD (ANOVA, P<0.0001). There was no significant difference in the respiratory system resistance (R_rs), Rinit, or Pdiff between BPD and no-BPD groups. However, Pdiff was significantly higher in infants with HMD, regardless of the outcome, when compared to the infants ventilated for apnea of prematurity. This suggests that the pathology of HMD is distal to the conducting airways and significantly alters the viscoelastic properties of the lung on day 1. Using stepwise logistic regression, C_rsdum on day 1 and birth weight or gestational age were significant independent predictors of the development of BPD, correctly classifying 92% of infants. Due to the correlation between birth weight and gestational age (r = 0.72, P<0.0001). only one of these variables was necessary in the prediction model. In conclusion, C_rsdyn is a better independent predictor of the development of BPD in preterm infants with HMD than gestational age or birth weight. Pediatr Pulmonol. 1993; 16:116–123. © 1993 Wiley-Liss, Inc.     

Pulmonary function in newborns after repair of congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is associated with pulmonary hypoplasia that limits survival, but the nature and extent of pulmonary dysfunction in neonates with CDH have not been studied. We performed pulmonary function tests (PFTs) in eight intubated infants who survived neonatal repair of CDH (wt, 3.33 ± 0.15 kg; age, 20.1 ± 2.7 d; mean ± S.E.M.). PFTs obtained from six full-term infants (wt, 3.56 ± 0.10 kg; age, 25.0 ± 3.3 d) with no respiratory illness served as controls. The deflation flow-volume curve technique produced maximum expiratory flow-volume (MEFV) curves, giving reproducible measurements of forced vital capacity (FVC) and maximal expiratory flow at 25% of FVC (MEF₂₅). Respiratory system compliance (Crs) and resistance (Rrs) were obtained with a modified passive mechanics technique. In seven of eight infants PFTs were repeated after nebulized bronchodilator (0.1% isoetharine). In neonates surviving CDH repair, as compared to those with normal lung function, FVC was significantly reduced (20.78 ± 3.32 vs. 39.83 ± 3.30 mL · kg^?1, P < 0.05). MEF₂₅ was also markedly reduced (8.41 ± 1.46 vs. 32.32 ± 4.35 mL · kg^?1 · s^?1, P < 0.05), indicating lower airway obstruction. After administration of nebulized bronchodilator, PFTs showed significant increases from control values in both FVC (15.9%) and MEF₂₅ (200%) without changes in Crs and Rrs. These findings indicate that neonates with CDH have restrictive lung defects, reflecting hypoplasia. After surgical repair and mechanical ventilation airway reactivity develops, primarily in smaller airways, and this may complicate the postoperative course. Pediatr Pulmonol. 1991 ; 11 :49-55.     

Mechanisms of late hemodynamic and airway dynamic responses to endotoxin in awake sheep

The mechanism of sustained alterations in pulmonary hemodynamics and lung mechanics after endotoxin infusion in sheep remains unclear. We examined the effects of metaproterenol, propranolol, atropine, and ibuprofen on pulmonary artery pressure (Ppa), dynamic compliance (Cdyn), resistance to airflow across the lungs (RL), specific airway conductance (SGaw), and alveolar-arterial oxygen difference (delta AaPO2) (room air) given 2.5 h after endotoxemia (except for propranolol, which was given 1 h after metaproterenol) in awake sheep. Atropine infusion had no effect on any of the variables measured. Ibuprofen infusion immediately reduced mean Ppa from 31 +/- 2 (mean +/- SEM) to 24 +/- 2 cm H2O (p less than 0.05). Metaproterenol and ibuprofen immediately increased Cdyn and SGaw and decreased RL to near baseline (p less than 0.05). No intervention affected delta AaPO2 (p greater than 0.05). In sheep treated with metaproterenol, propranolol immediately returned lung mechanics (p less than 0.05) to premetaproterenol levels without affecting delta AaPO2 (p greater than 0.05). Ibuprofen reduced lung lymph thromboxane-B2 towards baseline levels (p less than 0.05). We conclude that endotoxemia causes prolonged bronchoconstriction and pulmonary hypertension in sheep, which is largely mediated by constrictor prostanoids rather than by cholinergic mechanisms and is reversible with ibuprofen given 2.5 h after endotoxin.     

压力和容量控制通气在老年单肺麻醉肺保护通气策略中的比较

目的比较老年开胸手术单肺通气中压力控制通气（PCV）和容量控制通气（VCV）模式对呼吸力学和动脉血气的影响。方法46例术前肺功能不正常行开胸手术的患者,年龄均＆gt;60岁,双肺通气（TLV）期间均采用VCV模式（TLV-VCV）,单肺通气（OLV）后先采用传统方法通气（OLV-VCV1）,25 min后改为单肺保护通气（OLV-VCV2）,25 min后再改为压力控制通气（OLV-PCV）。监测气道峰压（Ppeak）、气道平台压（Pplat）、气道阻力（Raw）、动态胸肺顺应性（Cdyn）、分钟通气量（MV）等。结果与TLV-VCV比较,OLV-VCV1模式时Ppeak、Pplat、Raw升高（P〈0.01）、Cdyn降低（P〈0.01）。与OLV-VCV1比较,OLV-VCV2及OLV-PCV时Ppeak、Pplat、Raw较低,Cdyn较好（P均〈0.05）。OLV时动脉血PaO2较TLV时下降（P〈0.01）,OLV-PCV及OLV-VCV2时PaO2及PaCO2较OLV-VCV1升高（P〈0.05）。结论PCV模式控制气道压更有利于减少气道损伤,更适用于肺功能不全行开胸手术的老年患者。     

Leukotriene antagonist FPL 57231 prevents the acute pulmonary effects of Escherichia coli endotoxin in cats

We studied the effects of a selective leukotriene (LT) antagonist (FPL 57231, 2 mg kg-1 min-1) on the acute cardiopulmonary changes observed in feline endotoxin shock. LTC4 and LTD4 (0.1-3.0 micrograms kg-1) given intravenously had little or no activity on pulmonary arterial pressure (PAP), dynamic lung compliance (Cdyn), and airways resistance (Raw). They did, however, produce a systemic hypertension, which was significantly attenuated during the FPL 57231 infusion. E. coli endotoxin (2 mg kg-1) administration resulted in decreases in systemic arterial blood pressure and Cdyn, together with increases in both PAP and Raw. During infusion of FPL 57231, all these endotoxin-induced cardiopulmonary changes were attenuated. Radioimmunoassay of blood samples taken from cats given FPL 57231 showed that levels of 6-keto prosta-glandin F1 alpha and thromboxane B2 were not significantly increased by endotoxin, as would normally be expected in cats administered endotoxin. FPL 57231 was also found to antagonise the pulmonary effects of the thromboxanemimetic U46619 and of prostaglandin F2 alpha. These results indicate that it is unlikely that the leukotrienes are involved as important mediators of the acute phase of endotoxin shock in cats.     

Extracorporeal membrane oxygenation for the management of respiratory failure due to ANCA-associated vasculitis

We present here two patients whose near fatal respiratory distress was caused by pulmonary hemorrhage, and who were treated successfully by extracorporeal membrane oxygenation (ECMO). The underlying disease was anti-neutrophil cytoplasmic antibody (ANCA)-associated systemic vasculitis. They were initially treated with methylprednisolone pulse therapy along with cyclophosphamide. However, their respiratory failure progressed with a low PaO2/FiO2 ratio (< 100 mmHg) despite mechanical ventilation, and ECMO was initiated. After several days, the pulmonary hemorrhage subsided, and the patients were weaned successfully from ECMO. We suggest that ECMO may be used to manage life-threatening pulmonary hemorrhage in patients suffering from ANCA-associated systemic vasculitis.     

Airway responsiveness in isolated perfused rat lungs: effect of thoracic irradiation

We developed techniques for assessing airway reactivity in isolated perfused rat lungs by measuring the lung mechanics changes produced by injection of ACh into the pulmonary circulation. Lung resistance (RL) and dynamic compliance (Cdyn) changed in a dose-response fashion after ACh. We used the preparation to examine the effect of thoracic irradiation on airway responsiveness and pulmonary inflammation. Groups of rats were studied after sham irradiation or 24 h or 72 h after a single dose of 1500 rads. Thoracic irradiation did not alter baseline lung mechanics, but did increase the responsiveness of rat lungs to ACh 72 h after radiation. Radiation was not associated with an increase in neutrophils in lung lavage, airways or peripheral lung tissue. We conclude that thoracic irradiation alters airways reactivity without causing overt pulmonary inflammation, and that isolated perfused lungs can be useful for measurement of airway reactivity.     

The effects of acute hypoxia and hypercapnia on pulmonary mechanics in normal subjects and patients with chronic pulmonary disease

The influence of progressive hypoxia and hypercapnia on respiratory mechanics was evaluated in 26 subjects (six normal subjects, seven asthmatic subjects, seven patients with IPD, and six patients with COPD). During separate rebreathing runs of progressive isocapnic hypoxia and normoxic hypercapnia, breath-to-breath changes in RL and Cdyn were determined. In five of the six normal subjects, seven of the seven asthmatic subjects, and six of the seven subjects with IPD, RL decreased with both progressive hypoxia and hypercapnia without a change in Cdyn. In the patients with COPD, the effects of hypoxia and hypercapnia on RL and Cdyn were variable. Compared to normal subjects, the changes in RL during hypoxia and hypercapnia were not significantly different in the asthmatic subjects and the patients with IPD. These data provide evidence that acute progressive hypoxia and hypercapnia are associated with significant changes in Raw in both normal subjects and patients with chronic pulmonary disease.     

Clinical correlations and pulmonary function at 8 years of age after severe neonatal respiratory failure

OBJECTIVES: The aim of this study was to determine the pulmonary sequelae of severe neonatal respiratory failure. STUDY DESIGN: This was a multicenter, prospective study. Fifty-four survivors of neonatal respiratory failure (oxygenation indices >25 on two occasions), completed pulmonary function testing at 8 years of age. Thirty-one (57%) received extracorporeal membrane oxygenation (ECMO). Pulmonary outcome was based on spirometry and lung volume data. Pulmonary outcome for each diagnostic and treatment group is reported as mean and as percent predicted. Individually subjects were also classified based on spirometry, as either normal, obstructed (defined as forced expiratory volume (FEV(1)) in 1 sec:forced vital capacity (FVC) of <80 % predicted, or with reduced FVC (FCV of <80% predicted) with normal FEV(1)/FVC. Risk for adverse outcome was determined using univariate analysis. RESULTS: Mean FVC, FEV(1) and FEV(25-75) were reduced in the total cohort. The reduction was greatest in the subgroup with CDH and the group treated with ECMO. Assessed individually, 54% of subjects had normal spirometry and lung volumes, 19% airflow obstruction, and 27% reduced FVC. Poorer pulmonary outcome was linked to ECMO, congenital diaphragmatic hernia (CDH), birth weight for gestational age <10th percentile, duration of hospitalization, or need for prolonged supplemental oxygen. CONCLUSION: Neonates with severe respiratory failure due to CDH or needing ECMO and small for gestation are at increased risk of poorer pulmonary outcome and require close follow-up.     

Pulmonary sequelae at six months following extracorporeal membrane oxygenation.

Mechanical assisted ventilation for neonatal respiratory failure is associated with residual lung disease. Because ECMO rests the lungs, it has been suggested that ECMO will prevent chronic lung disease in survivors. To determine whether or not ECMO survivors have evidence of pulmonary sequelae, we studied 19 infants who were treated with ECMO for neonatal respiratory failure. Ten infants still required supplemental oxygen or pulmonary medications or both to treat clinical lung disease during the first six months of life. Thoracic gas volume was normal. Pulmonary mechanics in ECMO survivors were compared with those of 13 preterm infants with BPD at similar age. We conclude that a significant proportion of ECMO survivors have residual abnormalities in pulmonary mechanics at 6 months of age. We speculate that neonatal lung injury due to meconium aspiration and other causes is a more important determinant of abnormal pulmonary sequelae than the method of treatment.     

Frequency dependence of compliance in the evaluation of patients with unexplained respiratory symptoms

Frequency dependence of compliance (FDC) reflects non-homogeneous ventilatory distribution and, in the presence of a normal measured airway resistance, suggests peripheral airways dysfunction. This study evaluated peripheral airway function and bronchial reactivity in irritant exposed or non-exposed individuals with normal routine pulmonary function tests (PFTs) who had persistent unexplained lower respiratory symptoms. Twenty-two patients were identified with persistent respiratory symptoms and with normal chest X-ray and PFTs. Twenty were non-smokers; two had stopped smoking more than 10 years before evaluation. Twelve patients had been exposed to irritants in their workplaces or at home. Non-specific bronchial hyper-reactivity (nsBHR) and FDC, pre- and post-bronchodilator, were measured in all patients. Studies were repeated in 6/12 irritant-exposed subjects after exposure removal and inhaled corticosteroid treatment. Whereas 12/22 patients had nsBHR, all 22 subjects demonstrated FDC [dynamic lung compliance/static lung compliance Cdyn,1 / Cst,1 at respiratory frequency 60 min(-1) (f60), mean 46%, range 27-67%]. After bronchodilator administration, a 15% improvement Cdyn,1 was observed most consistently at f60 (mean% improvement 26%, 95% CI 14-38%) and in subjects without nsBHR. However, Cdyn,1 at f60 did not return to normal after inhaled bronchodilator. Irritant-exposed and unexposed individuals appeared similar in results of testing for FDC and nsBHR. FDC and its response to bronchodilators provide objective physiological measures of an airway abnormality which may provide a basis for clinical symptoms in patients with normal routine pulmonary function studies. The presence of persistently abnormal FDC after bronchodilator (BD) and on follow up studies may reflect chronic inflammatory and/or structural changes in the airways in addition to bronchoconstriction.     

Neonatologische Notf?lle beim reifen Neugeborenen

Neonatal emergencies still represent a major challenge with important implications for obstetricians and perinatologists. Meconium aspiration syndrome (MAS incidence 0.5?C1 per 1,000 live births in Europe) is characterized by an early onset of respiratory failure and often by pulmonary hypertension. Endotracheal inspection and suctioning of meconium immediately after birth are the most important therapeutic steps. In congenital diaphragmatic hernia (CDH), herniation of the abdominal viscera into the thorax leads to severe persistent pulmonary hypoplasia and pulmonary hypertension (PPHN). These newborns must be immediately intubated and receive mechanical ventilation; surgery is performed after 24-72?h. Biometric assessment of fetal lung volume and the fetal lung area to head circumference ratio (LHR) are the methods for prenatal prediction of survival and the need for extracorporeal membrane oxygenation (ECMO) and thus allow planning the optimal therapy. Perinatal asphyxia (estimated incidence 3?C5 per 1,000 live births) is the most common reason for mortality and long-term neurological morbidity in term newborns. In cases of hypoxic-ischemic encephalopathy (HIE), hypothermia is a promising therapeutic approach.     

Disparity between proximal and distal airway reactivity during methacholine challenge

There is an increasing awareness of the role of distal airways in the pathophysiology of obstructive lung diseases including asthma and chronic obstructive pulmonary disease. We hypothesize that during induced bronchoconstriction: 1) disparity between distal and proximal airway reactivity may occur; and 2) changes in distal airway function may explain symptom onset in subjects with minimal FEV(1) change. 185 subjects underwent methacholine challenge testing (MCT). In addition to spirometry, oscillometry was performed at baseline and after maximum dose of methacholine; 33/185 also underwent oscillometry after each dose. Oscillometric parameters included resistance at 5 and 20 Hz (R(5), R(20)) and heterogeneity of distal airway mechanics assessed by frequency dependence of resistance 5-20 Hz (R(5-20)) and reactance area (AX). R(5) varied widely during MCT (range -0.8 - 11.3 cmH(2)O/L/s) and correlated poorly with change in FEV(1) (r = 0.17). Changes in R(5) reflected changes in both R(20) and R(5-20) (r = 0.59, p<0.05; r = 0.87, p<0.0001). However, R(20) increased only 0.3 cmH(2)O/L/s, while R(5-20) increased 0.7 cmH(2)O/L/s for every 1cmH(2)O/L/s change in R(5,) indicating predominant effect of distal airway mechanics. 9/33 subjects developed symptoms despite minimal FEV(1) change (<5%), while R(5) increased 42% due to increased distal airway heterogeneity. These data indicate disparate behavior of proximal airway resistance (FEV(1) and R(20)) and distal airway heterogeneity (R(5-20) and AX). Distal airway reactivity may be associated with methacholine-induced symptoms despite absence of change in FEV(1). This study highlights the importance of disparity between proximal and distal airway behavior, which has implications in understanding pathophysiology of obstructive pulmonary diseases and their response to treatment.     

13例体外膜式氧合治疗肺栓塞合并心衰术后应用

【】目的：总结成人肺栓塞合并心衰术后应用体外膜式氧合技术(ECMO)治疗的临床经验。方法：2013年12月-2017年6月对我院13例成人肺栓塞合并心衰术后行体外膜式氧合技术治疗,其中,男性8例,女性5例;年龄37-65岁,采用静脉-动脉转流,辅助期间流量范围1.5L/min-3.0L/min,ECMO辅助时间(82.4±47.1)h,维持活化凝血酶时间(ACT)200s-220s结果：13例病人通过应用ECMO治疗过程中没有出现神经系统并发症,患者均成功撤除ECMO,并康复出院。结论：体外膜式氧和技术可以降低肺栓塞取栓术后肺动脉高压、减轻右心负荷、改善气体交换,是治疗肺栓塞术后合并心衰患者的有效手段。     

First successful treatment of a COVID-19 pregnant woman with severe ARDS by combining early mechanical ventilation and ECMO

The novel coronavirus (COVID-19) has become a global pandemic outbreak. Patients with COVID-19 are prone to progress to acute respiratory distress syndrome (ARDS), and even severe ARDS with ineffective mechanical ventilation, and an extremely high mortality. Extracorporeal membrane oxygenation (ECMO) provides effective respiratory support and saves time for the treatment of severe COVID-19. The present study reports that a 31-year-old pregnant female infected by COVID-19, who suffered from fever, dyspnea, and rapid ARDS. The patient's pulmonary function gradually recovered by combining early mechanical ventilation and ECMO, and finally, this patient was successfully weaned from ECMO and the ventilator. No fibrosis lesions were found in the chest CT, and the patient recovered very well after leaving from the hospital for one month.     

Detection of added respiratory loads in patients with restrictive lung disease

In patients with airways obstruction, inspiratory resistive load detection conforms to Weber's law: the higher the background or intrinsic pulmonary resistance, the greater the threshold resistance (the resistance detected 50% of the time, delta R50). In patients with restrictive lung disease, the pulmonary elastance is increased, and the present study was undertaken to assess whether Weber's law applies to elastic load detection in these patients. In 7 patients with restrictive lung disease caused by interstitial fibrosis, there was a significantly decreased total lung capacity compared with that in 6 normal subjects (mean, 63.1 and 101% predicted, respectively; p less than 0.01) and significantly increased total pulmonary elastance (means +/- SD, 14.4 +/- 4.7 and 9.6 +/- 1.8 cmH2O/L, respectively; p less than 0.05). There was no significant difference (p greater than 0.1) between the 2 groups in delta R50; however, the elastic load detection threshold, delta E50, was significantly greater (p less than 0.05) in the patients than in the normal subjects (mean +/- SD, 2.8 +/- 1.3 and 1.4 +/- 0.4 cmH2O/L, respectively). When the detection threshold was adjusted for the background elastance, however, there was no significant difference between the 2 groups (mean +/- SD, 0.21 +/- 0.1 and 0.15 +/- 0.04, respectively; p greater than 0.05). These results confirm that Weber's law is also applicable to the detection of added elastic loads in patients with restrictive lung disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of a proximal compliance on interrupter measurements of resistance

The interrupter method for measuring respiratory system resistance involves rapidly interrupting flow at the airway opening while measuring the pressure just distal to the site of interruption. In general, the pressure signal obtained exhibits an initial rapid change (delta Pinit) accompanied by rapid damped oscillations, followed by a further slow change to a steady-state plateau level. Delta Pinit is thought to principally reflect the resistance of the pulmonary airways Raw. We have developed a computer model capable of simulating the main features observed in an interrupter pressure signal. We show that the distinct phases in the pressure signal can be obscured by the existence of a compliant compartment between the airways and the occluding valve (e.g. the cheeks and pharynx) when Raw is increased. Our results suggest that supporting the cheeks may enable one to estimate Raw with the interrupter technique in the presence of mild to moderate bronchoconstriction, but that with severe bronchoconstriction (Raw increased 10-fold above normal) it may not be possible.     

慢性阻塞性肺疾病患者长期人工通气撤机指标的临床研究

目的评价床边综合肺功能作为长期人工通气的慢性阻塞性肺疾病（COPD）患者脱机指标的指导意义。方法监测58例（成功组：43例，失败组：15例）通气时间＞72h的COPD呼衰患者达到临床脱机标准后的血气分析、肺功能及呼吸力学的改变情况。结果两组患者的血气分析、急性生理、慢性健康评分（APACHEⅡ）、氧合指数、动态顺应性及气道阻力均无显著差异（P均＞0．05）；成功组患者的肺活量／潮气量（VC／V_T）、最大吸气负压（Pi_(max)）和浅快呼吸指数（f／V_T）分别为：2．10±0．20、（－21±4）cmH_2O及（74±30）次·min~(-1)·L~(-1)；失败组患者则依次为1．30±0．20、（－13±3）cmH_2O及（115±20）次·min~(-1)·L~(-1)，两组结果比较差异有显著性，P均＜0．05。以VC／V_T＞1．8、Pi_(max)＜－18cmH_2O和f／V_T＜105次·min~(-1)·L~(-1)作为临界值预测此类患者脱机成功与否，具有较高的敏感性（84％）和特异性（90％）。结论　综合肺功能指标（VC／V_T、Pi_(max)及f／V_T）可用于指导长期通气的COPD患者选择脱机时机，适宜在我国目前条件下推广普及。