Effects of an inhaled bronchodilator on gas distribution and over-all ventilatory efficiency in patients with chronic obstructive pulmonary disease

The effects of an inhaled bronchodilator on the distribution of inspired gas and over-all efficiency of ventilation were studied by the nitrogen washout technic in 16 patients with chronic obstructive pulmonary disease; three normal subjects and two patients with asymptomatic asthma (and normal spirometric values) were also studied. In normal and asthmatic subjects and in patients with chronic obstructive pulmonary disease and mild to moderate functional impairment, the nitrogen clearance did not vary significantly or showed changes suggesting less uniform gas distribution and reduced ventilatory efficiency. In most patients with advanced chronic obstructive pulmonary disease, the bronchodilator caused changes suggesting more uniform distribution of inspired gas and increased efficiency of ventilation. Multiple regression analysis showed that the behavior of the nitrogen clearance after treatment was also related to the response of the anatomic dead space. The effects of the bronchodilator varied with time. The results are consistent with the assumption that the changes in nitrogen clearance after bronchodilator therapy reflect the concourse of multiple factors, which may be expected to have favorable or unfavorable effects on the distribution of inspired gas and the efficiency of ventilation.     

The Association of Lung Clearance Index with COPD and FEV1 Reduction in ‘Men Born in 1914’

Lung Clearance Index (LCI) provides an overall measurement of ventilation inhomogeneity. This population-based study examines whether LCI predicts pulmonary obstruction and incidence of chronic obstructive pulmonary disease (COPD) events over a long-term follow-up. Multiple breath nitrogen washout and spirometry were performed in 674 men from the cohort “Men born in 1914” at age 55 years. Subjects were classified into quartiles (Q) of LCI and according to LCI above and below upper limit of normal (ULN). Incidence of COPD events (COPD hospitalisations or COPD-related deaths) were monitored over the remaining life span of the men, by linkage with national hospital registers. In addition, development of pulmonary obstruction (i.e., FEV¹/vital capacity below lower limit of normal (LLN)) was studied in 387 men who were re-examined with spirometry at 68 years of age. Over 44 years of follow-up, there were 85 incident COPD events. Hazards ratios (HRs) for COPD across quartiles of LCI were: Q1 1.00 (reference), Q2 1.30 (95% confidence interval: 0.61–2.74), Q3 1.97 (0.97–3.98) and Q4 3.99 (2.06–7.71) (p value for trend <0.001). This relationship remained significant after adjustments for confounding factors, including smoking and FEV¹ (HR, Q4 vs Q1: 2.34 (1.17–4.69); p value for trend: 0.006). Reduction of FEV¹ between 55 and 68 years of age and incidence of pulmonary obstruction was highest in those with high LCI. High LCI is associated with future development of pulmonary obstruction and incidence of COPD hospitalisations in men from the general population.     

Evaluation of ventilation maldistribution as an early indicator of lung disease in children with cystic fibrosis.

Many children with cystic fibrosis (CF), receiving modern, aggressive CF care, have normal spirometry results. This study aimed to see if homogeneity of ventilation distribution is impaired early in the course of CF lung disease, and if ventilation inhomogeneity is a more frequent finding than abnormal spirometry in children benefiting from modern CF care. The study compared spirometry findings to two indices of ventilation inhomogeneity (mixing ratio (MR) and lung clearance index (LCI)) from multiple-breath inert gas washout in 43 children with CF, aged 3-18 yrs, and 28 healthy children. In total, 10/43 CF subjects (23%) had reduced forced expiratory volume in one second (FEV1) and 14/34 (41%) showed abnormal maximum expiratory flow at 25% of forced vital capacity (MEF25). In contrast, MR was abnormal in 31/43 (72%) and LCI in 27/43 (63%). MR was abnormal in 22/33 CF subjects with normal FEV1, versus 0/28 controls (p<0.001), and abnormal MR was found in 10/20 CF subjects with normal MEF25, versus 0/22 controls (p<0.001). Nine of the 10 CF subjects with reduced FEV1 and 12/14 with abnormal MEF25 showed abnormal MR. Inert gas washout discloses airway dysfunction in the majority of children with cystic fibrosis with normal lung function judged by spirometry. These findings suggest that multiple-breath inert gas washout is of greater value than spirometry in detecting early cystic fibrosis lung disease.     

Diffusing Capacity for Carbon Monoxide is Linked to Ventilatory Demand in Patients with Chronic Obstructive Pulmonary Disease

Abstract

Dyspnea is deemed to result from an imbalance between ventilatory demand and capacity. The single-breath diffusing capacity for carbon monoxide (DLCO) is often the best correlate to dyspnea in COPD. We hypothesized that DLCO contributes to the assessment of ventilatory demand, which is linked to physiological dead space /tidal volume (VD/VT) ratio. An additional objective was to assess the validity of non-invasive measurement of transcutaneous P_CO2 allowing the calculation of this ratio. Forty-two subjects (median [range] age: 66 [43–80] years; 12 females) suffering mainly from moderate-to-severe COPD (GOLD stage 2 or 3: n = 36) underwent pulmonary function and incremental exercise tests while taking their regular COPD treatment. DLCO% predicted correlated with both resting and peak physiological VD/VT ratios (r = ?0.55, p = 0.0015 and r = ?0.40, p = 0.032; respectively). The peak physiological VD/VT ratio contributed to increase ventilation (increased ventilatory demand), to increase dynamic hyperinflation and to impair oxygenation on exercise. Indirect (MRC score) and direct (peak Borg score/% predicted V˙O2) exertional dyspnea assessments were correlated and demonstrated significant relationships with DLCO% predicted and physiological VD/VT at peak exercise, respectively. The non-invasive measurement of transcutaneous P_CO2 both at rest and on exercise was validated by Bland-Altman analyses. In conclusion, DLCO constitutes and indirect assessment of ventilatory demand, which is linked to exertional dyspnea in COPD patients. The assessment of this demand can also be non invasively obtained on exercise using transcutaneous PCO₂ measurement.     

Effect of salmeterol on the ventilatory response to exercise in chronic obstructive pulmonary disease.

This study examined the effects of bronchodilator-induced reductions in lung hyperinflation on breathing pattern, ventilation and dyspnoea during exercise in chronic obstructive pulmonary disease (COPD). Quantitative tidal flow/volume loop analysis was used to evaluate abnormalities in dynamic ventilatory mechanics and their manipulation by a bronchodilator. In a randomised double-blind crossover study, 23 patients with COPD (mean +/- SEM forced expiratory volume in one second 42 +/- 3% of the predicted value) inhaled salmeterol 50 microg or placebo twice daily for 2 weeks each. After each treatment period, 2 h after dose, patients performed pulmonary function tests and symptom-limited cycle exercise at 75% of their maximal work-rate. After salmeterol versus placebo at rest, volume-corrected maximal expiratory flow rates increased by 175 +/- 52%, inspiratory capacity (IC) increased by 11 +/- 2% pred and functional residual capacity decreased by 11 +/- 3% pred. At a standardised time during exercise, salmeterol increased IC, tidal volume (VT), mean inspiratory and expiratory flows, ventilation, oxygen uptake (VO2) and carbon dioxide output. Salmeterol increased peak exercise endurance, VO2 and ventilation by 58 +/- 19, 8 +/- 3 and 12 +/- 3%, respectively. Improvements in peak VO2 correlated best with increases in peak VT; increases in peak VT and resting IC were interrelated. The reduction in dyspnoea ratings at a standardised time correlated with the increased VT. Mechanical factors play an important role in shaping the ventilatory response to exercise in chronic obstructive pulmonary disease. Bronchodilator-induced lung deflation reduced mechanical restriction, increased ventilatory capacity and decreased respiratory discomfort, thereby increasing exercise endurance.     

Effect of chlormadinone acetate on ventilatory control in patients with chronic obstructive pulmonary disease

Twelve patients with chronic obstructive pulmonary disease (COPD) were studied to determine the effect of ventilatory stimulation with chlormadinone acetate (CMA), a potent synthetic progesterone, on chemical and neuromechanical respiratory controls and pulmonary gas exchange. Using a randomized, double-blind, cross-over trial, 1 wk of CMA therapy caused a significant reduction in arterial CO2 tension (Paco2) by 4.6 +/- 0.6 (SE) mmHg. This Paco2 fall was associated with increased minute ventilation (Vl), tidal volume (VT), and mean inspiratory flow (VT/Tl). During CMA administration, occlusion pressure response to CO2 with and without inspiratory flow-resistive loading increased significantly (p less than 0.01) over that during placebo administration, whereas ventilatory response to CO2 did not. In addition, normocapnic ventilatory and occlusion pressure response to hypoxia were significantly elevated (p less than 0.01) during CMA therapy. Furthermore, the degree of load compensation, which was assessed by the ratio of the loaded to unloaded slope in the occlusion pressure response to CO2, increased in all subjects after CMA administration. These results indicate that CMA augments not only the respiratory neuromuscular response to hypercapnia and hypoxia, but also flow-resistive load compensation in patients with COPD, and it may provide support for the use of CMA in patients who are able to decrease their Paco2 with this agent.     

Changes in alveolar mixing efficiency during exercise.

The increased alveolar-arterial oxygen gradient (A-aDO2) occurring at higher levels of exercise may reflect impaired gas mixing. This latter function was investigated using the multiple breath nitrogen washout technique in 30 physical training students (15 M, 15 F). They were examined at rest and at work loads of 50, 100 and 150 W, using a cycle ergometer. Measurements included tidal volume (VT), serial dead space (VDS) and from the washout alveolar dead space (VDA), lung volume as the end-expiratory volume (EEV) and alveolar gas mixing efficiency (AME). There were expected rises in mean V1 from 641 +/- 161 to 1650 +/- 248 ml and in minute ventilation (VE) from 11.1 +/- 3.1 to 47.1 +/- 5.2 L.min-1 at 150 W but EEV changed only slightly from 2555 +/-559 to 2321 +/- 585 ml at the same workload. Despite an increase in VDS from 156 +/- 33 to 258 +/- 35 ml and VDA from 139 +/- 40 to 305 +/- 73 ml, AME rose significantly with exercise from 72.5 +/- 5.0 to 78.3 +/- 3.3%. These results are discussed in relation to the morphology of the lung, and the stationary interface theory. They suggest that gas mixing improves at the onset of exercise only, so that the widening in A-aDO2 with increasing levels of exercise cannot be explained by impaired mixing efficiency alone, and is probably due to other factors such as critically rapid transit time of blood through the pulmonary capillaries as cardiac output increases.     

Serial studies of pulmonary function in continuous ambulatory peritoneal dialysis. A prospective study

Continuous ambulatory peritoneal dialysis (CAPD) produces a nearly continuous state of iatrogenic ascites which may interfere with respiratory excursions of the diaphragm and compromise ventilatory function. Sitting and supine studies of pulmonary function and arterial blood gas analyses done serially in 13 patients undergoing CAPD showed a significant decline in pulmonary volumes immediately after the institution of CAPD; however, the decline was not accompanied by abnormalities in gas transfer. Pulmonary volumes returned to baseline values within two weeks in all patients, including those with preexisting mild chronic obstructive pulmonary disease (COPD). It is concluded that CAPD does not compromise pulmonary function in patients with normal pulmonary function or in those with mild COPD.     

Peripheral airway involvement in CF and asthma compared by inert gas washout

Multiple-breath N2 washouts were performed before and after bronchodilation in 15 patients with moderately severe asthma (mean age 13 years), and in 11 patients with cystic fibrosis (CF; mean age 16 years) matched for FEV1. Eighteen healthy subjects (mean age 15 years) were studied before bronchodilation. The lung clearance index (LCI) was determined from the washout curve and gas trapping was assessed from five subsequent large breaths. Analysis of the progression of the concentration normalized phase III slopes (Sn(III)) over the washout was used to determine inhomogeneity in the conducting airways (S(cond)) and inhomogeneity close to or within the gas exchange zone (S(acin)). Before bronchodilation all washout indexes were abnormal in the CF group, and all but S(acin) in the asthma group. Two indexes were higher in CF than in asthma: LCI (11.5 (3.3) vs. 8.7 (1.3); P < 0.01), and S(acin) (0.307 (0.207) vs. 0.142 (0.071); P < 0.01), while gas trapping indexes and S(cond) (0.151 (0.071) vs. 0.127 (0.041)) did not differ significantly. After bronchodilation, all indexes improved in asthma and only S(cond) remained abnormally elevated. In CF, only a modest but statistically significant S(acin) improvement was seen and all indexes stayed abnormal. The study shows that overall ventilation inhomogeneity and particularly inhomogeneity in or close to the gas exchange zone are more pronounced in CF than in asthma matched for FEV1, while inhomogeneity in the conducting airway zone is similar. After bronchodilation, residual abnormalities of airway function are seen all through the airway tree in CF but only in the conducting airways in asthma.     

呼出气CO2容积曲线对肺部疾病换气功能障碍的诊断与评价

目的 评价无创肺换气功能诊断技术即呼出气CO2容积曲线(VCap)对肺部疾病慢性阻塞性肺疾病(chronic obstructive pulmonary disease.COPD)、支气管哮喘(简称哮喘)和间质性肺疾病(ILD)患者换气功能障碍的诊断价值及临床意义.方法 对照组(医院对照)94人,平均年龄(61.59±8.73)岁.COPD组287例.平均年龄(64.31±11.71)岁.根据COPD肺功能分级标准分4级:COPD Ⅰ级(9例)、COPD Ⅱ级(141例)、COPD Ⅲ级(75例)、COPDⅣ级(62例).哮喘组251例,平均年龄(57.86±13.54)岁.根据气道阻塞程度分4级(分级标准同COPD):轻度阻塞(6例)、中度阻塞(113例)、重度阻塞(100例)、极重度阻塞(32例).ILD组45例,平均年龄(56.42±13.97)岁.主要分析变量:最大呼出气二氧化碳浓度、Ⅲ相斜率(dC/dV3)、呼出气最高CO2浓度的25%～50%时的容积与潮气容积的比值(Vm25-50/VT)、呼出气最高CO2浓度的50%～75%时的容积与潮气容积的比值(Vm50-75/VT).结果 ①ILD、哮喘和COPD分别与对照组比较:Vm25-50/VT、Vm50-75/VT、FeCO2max、dC/dV3,差异有统计学意义(P<0.01);②轻度哮喘和轻度COPD组比较:Vm50-75/VT,dC/dV3差异无统计学意义;中、重度组比较:Vms50-75/VT,dC/dV3差异有统计学意义(P<0.01);哮喘合并肺气肿和COPD(肺气肿)组比较差异无统计学意义;③Vm50-75/VT和dC/dV3用于COPD(肺气肿)的评价敏感度分别为98.3%和96.5%.特异度分别为91.4%和86.1%.结论 ①COPD、哮喘和ILD患者VCap形态异常.dC/dV3增高并且与疾病的严重程度有关,示肺内气体分布不均,系气道阻力增高和(或)肺顺应性改变导致吸入气体分布不均和呼出气体非同步排空所致,ILD相对于COPD和哮喘则气体分布不均更为突出;②变量Vm50-75/VT间接反映肺泡死腔量,相对受生理因素及通气量的影响小,与常规肺功能指标均有较好的相关性,可作为评价肺部疾病换气功能障碍即肺泡死腔增大,通气血流/灌注失调间接指标.③Vm50-75/VT%≥10%和dC/dV3≥1.3%/L用于评价肺气肿有较高敏感度和特异度.     

慢性阻塞性肺疾病患者运动高峰时肺内气体交换对运动能力的影响

目的 探讨COPD患者在运动高峰时肺内气体交换对最大运动能力的影响.方法 对42例男性稳定期COPD患者及26例健康男性进行功率递增至症状自限的踏车运动,同步实时测定摄氧量和二氧化碳产生量,在运动高峰时抽取桡动脉血,测定并计算PaO2、PaCO2、死腔容积与潮气容积比值(VD/VT)和P(A-a)O2.分别对两组资料进行正态性检验,符合正态分布的资料以x-±s表示,两组间比较采用独立样本t检验,最大摄氧量与运动高峰时的血气参数进行相关因素分析.结果 COPD组的最大摄氧量[(16±4)ml·kg-1·min-1]明显低于对照组[(19±6)ml·kg-1·min-1];PaCO2[(43±3)mm Hg,1 mm Hg=0.133 kPa]、VD/VT(0.35±0.11)和P(A-a)O2[(33±11)mm Hg]均明显高于对照组[(40±5)mm Hg、0.27±0.08和(15±7)mm Hg];最大摄氧量与VD/VT呈显著负相关(r=-0.734,P＜0.01).结论 VD/VT增加导致通气效率降低,这是引起COPD患者运动能力减低的一个重要原因.     

Pulmonary physiology: Future directions for lung function testing in COPD

Chronic obstructive pulmonary disease (COPD) is a term that encompasses different pathological conditions having excessive airflow limitation in common. A wide body of knowledge has been accumulated over the last century explaining the mechanisms by which airway (chronic bronchitis) and parenchymal (emphysema) diseases lead to an indistinguishable spirometric abnormality. Although the definition of emphysema is anatomical, early studies showed that its presence can be inferred with good approximation from measurements of lung mechanics and gas exchange, in addition to simple spirometry. Studies using tests of ventilation distribution showed that abnormalities are present in smokers with normal spirometry, although these tests were not predictive of development of COPD. At the beginning of the third millennium, new documents and guidelines for diagnosis and treatment of COPD were developed, in which the functional diagnosis of COPD was restricted, for the sake of simplicity, to simple spirometry. In recent years, there has been a resurgence of interest in separating bronchitic from emphysematous phenotype of COPD. For this purpose, high‐resolution computed tomography scanning has been added to diagnostic work‐up. At the same time, methods for lung function testing have been refined and seem promising for detection of early small airways abnormalities. Among them are the forced oscillation technique and the nitrogen phase III slope analysis of the multiple‐breath washout test, which may provide information on ventilation inhomogeneity. Moreover, the combined assessment of diffusing capacity for nitric oxide and carbon monoxide may be more sensitive than the latter alone for partitioning diffusive components at parenchymal level.     

长期家庭氧疗联合肺康复训练对慢阻肺合并呼吸衰竭患者的疗效观察

目的探讨长期家庭氧疗联合肺康复训练在慢阻肺合并呼吸衰竭患者康复治疗中的疗效。方法选取48例慢阻肺合并呼吸衰竭患者,按照计算机随机方法分为研究组与对照组,每组24例。对照组患者给予常规治疗,研究组患者在此基础上予以长期家庭氧疗和肺康复训练治疗,对两组患者进行为期12个月随访,对比两组患者肺功能、血气分析、6分钟步行距离、生存质量评分以及血清炎症因子水平。结果研究组与对照组患者的生活质量评分、动脉血气分析、肺功能、6分钟步行距离、炎症因子CRP及TNF-α水平检测值相比较,研究组比对照组患者上述指标具有明显改善,差异具有统计学意义,P0.05。结论长期家庭氧疗联合肺康复训练对慢阻肺疾病合并呼吸衰竭患者具有积极作用,值得推广。     

Dynamic hyperinflation and exercise intolerance in chronic obstructive pulmonary disease.

The role of dynamic hyperinflation (DH) in exercise limitation in chronic obstructive pulmonary disease (COPD) remains to be defined. We examined DH during exercise in 105 patients with COPD (FEV(1) = 37 +/- 13% predicted; mean +/- SD) and studied the relationships between resting lung volumes, DH during exercise, and peak oxygen consumption (VO(2)). Patients completed pulmonary function tests and incremental cycle exercise tests. We measured the change in inspiratory capacity (Delta IC) during exercise to reflect changes in DH. During exercise, 80% of patients showed significant DH above resting values. IC decreased 0.37 +/- 0.39 L or 14 +/- 15% predicted during exercise (p < 0.0005), but with large variation in range. Delta IC correlated best with resting IC, both expressed %predicted (r = -0.50, p < 0.0005). Peak VO(2) (%predicted maximum) correlated best with the peak tidal volume attained (VT standardized as % of predicted vital capacity) (r = 0.68, p < 0.0005), which, in turn, correlated strongly with IC at peak exercise (r = 0.79, p < 0.0005) or at rest (r = 0.75, p < 0.0005). The extent of DH during exercise in COPD correlated best with resting IC. DH curtailed the VT response to exercise. This inability to expand VT in response to increasing metabolic demand contributed importantly to exercise intolerance in COPD.     

Chronic effort dyspnea explained by lung function tests and by HRCT and CRX radiographic patterns in COPD: a post-hoc analysis in 51 patients

This paper is a post-hoc analysis of a previous study performed to investigate the relationship between computerized tomography (CT) and lung function in 51 outpatients with mild-to-moderate COPD. We studied whether changes in lung function and radiographic patterns may help to explain dyspnea, the most disturbing symptom in patients with COPD. The Medical Research Council (MRC) dyspnea scale shows, by univariate analysis, a similar strength of association to CT expiratory lung density and to DL(CO), a functional index of lung parenchymal loss. The MRC dyspnea scale shows a somewhat less strength of association with a small vertical heart on plain chest films. In multivariate analysis, the model with the strongest association to the MRC dyspnea scale (r = 0.76, p < 0.0001) contains 4 explanatory variables (DL(CO), FRC, PaCO(2), and radiographic pattern of pulmonary hypertension). We suggest that diffusing capacity reflects the emphysematous component of hyperinflation, associated by definition with destruction of terminal airspace walls, as distinct from the air trapping component, which is ascribed to airway obstruction and associated with FRC. PaCO(2) mainly reflects the ventilatory components, i.e., ventilatory drive and ventilatory constraints, of pulmonary gas exchange in COPD, while radiographic pattern of pulmonary hypertension likely reflects hypoxic vascular changes, which depend mainly on ventilation/perfusion mismatch and give rise to pulmonary arterial hypertension that may contribute per se to dyspnea. In conclusion, our analysis points out that chronic effort dyspnea variance may account for up to 58% (r(2) = 0.58) by lung function tests and radiographic patterns. Thus, about 42% of the MRC dyspnea variance remains unexplained by this model. On the other hand, dyspnea ascertainment is dependent on subjective behavior and evaluation and in tests is influenced by individual performance and perception. For example in the 6-minute walk test, a similar or higher proportion (60%) of the overall variance is unexplained.     

百令胶囊对慢性阻塞性肺病患者的影响

目的观察百令胶囊对COPD患者肺功能、血气和C反应蛋白的影响。方法选择101例住院的轻中度COPD患者,分为治疗组与对照组,进行第一秒用力呼气容积(FEV1)、用力肺活量(FVC)、血气、C反应蛋白检测;对照组常规予以抗炎、平喘、祛痰对症治疗,治疗组在此基础上加服百令胶囊,分别在入院时、出院时、12周后重复上述检查。结果治疗组与对照组比较差异显著(P0.05)。结论 COPD患者服用百令胶囊可改善肺功能,缓解病情,提高生活质量。     

Exercise hypercapnia in advanced chronic obstructive pulmonary disease: the role of lung hyperinflation

In severe chronic obstructive pulmonary disease (COPD), carbon dioxide retention during exercise is highly variable and is poorly predicted by resting pulmonary function and arterial blood gases or by tests of ventilatory control. We reasoned that in patients with compromised gas exchange capabilities, exercise hypercapnia could be explained, in part, by the restrictive consequences of dynamic lung hyperinflation. We studied 20 stable patients with COPD (FEV(1) = 34 +/- 3 percent predicted; mean +/- SEM) with varying gas exchange abnormalities (Pa(O(2)) range, 35 to 84 mm Hg; Pa(CO(2)) range, 31 to 64 mm Hg). During symptom-limited maximum cycle exercise breathing room air, Pa(CO(2)) increased 7 +/- 1 mm Hg (p < 0.05) from rest to peak exercise (range, -6 to 25 mm Hg). We measured the change in Pa(CO(2)) after hyperoxic breathing at rest as an indirect test of ventilation-perfusion abnormalities. The change in Pa(CO(2)) from rest to peak exercise correlated best with the acute change in Pa(CO(2)) during hyperoxia at rest (r(2) = 0.62, p < 0.0005) and with resting arterial oxygen saturation (r(2) = 0.30, p = 0.011). During exercise, the strongest correlates of serial changes in Pa(CO(2)) from rest included concurrent changes in end-expiratory lung volume expressed as a percentage of total lung capacity (partial correlation coefficient [r] = 0.562, p < 0.0005) and oxygen saturation (partial r = 0.816, p < 0.0005). In severe COPD, the propensity to develop carbon dioxide retention during exercise reflects marked ventilatory constraints as a result of lung hyperinflation as well as reduced gas exchange capabilities.     

不同机械通气模式对COPD呼吸衰竭患者肺功能及氧代谢的影响比较

目的比较不同机械通气模式对COPD呼吸衰竭患者肺功能及氧代谢的影响。方法选取本院进行治疗的64例COPD呼吸衰竭患者为研究对象,将其随机分为A组和B组各32例,其中A组采用BiPAP模式进行干预治疗,B组则采用SIMV+PSV模式进行干预治疗,将两组治疗前及治疗后3 d、7 d的肺功能、血气分析及氧代谢指标进行比较。结果 B组治疗后3 d、7 d的肺功能、血气分析及氧代谢指标改善幅度均大于A组,P均<0.05,有显著性差异。结论 SIMV+PSV模式可显著改善COPD呼吸衰竭患者肺功能及氧代谢指标,对于改善患者呼吸衰竭的状态发挥着积极的作用。     

Review of ventilatory techniques to optimize mechanical ventilation in acute exacerbation of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major global healthcare problem. Studies vary widely in the reported frequency of mechanical ventilation in acute exacerbations of COPD. Invasive intubation and mechanical ventilation may be associated with significant morbidity and mortality. A good understanding of the airway pathophysiology and lung mechanics in COPD is necessary to appropriately manage acute exacerbations and respiratory failure. The basic pathophysiology in COPD exacerbation is the critical expiratory airflow limitation with consequent dynamic hyperinflation. These changes lead to further derangement in ventilatory mechanics, muscle function and gas exchange which may result in respiratory failure. This review discusses the altered respiratory mechanics in COPD, ways to detect these changes in a ventilated patient and formulating ventilatory techniques to optimize management of respiratory failure due to exacerbation of COPD.     

Exercise tolerance in chronic obstructive pulmonary disease: importance of active and passive components of the ventilatory system

We investigated which components of ventilatory function are related to exercise tolerance in chronic obstructive pulmonary disease (COPD) patients. Physical characteristics, usual lung function, timing and neuromuscular components of ventilation were measured in 113 outpatients in whom FEV1/VC was less than 75% of the predicted value and exercise was limited by breathlessness. These variables were used to predict the maximum work load during progressive bicycle exercise. The prediction was obtained using a stepwise procedure in men and women separately. Among the variables selected, age, body weight, FEV1/VC, PImax, and P0.1/VT/TI accounted for 79% of the variability in maximum performance in men. The predictive model was statistically verified and was stable. The mean prediction error was 12 Watts. Among these variables, P0.1/VT/TI, PImax, and FEV1/VC were the main determinants of maximum work load (MWL). These results show that exercise limitation in COPD is related to impairment of both the active (inspiratory muscles) and passive (respiratory impedance) components of the ventilatory system. The same conclusions concerning passive components are proposed for women, despite a smaller population which prevented verification of the prediction.